Open access peer-reviewed chapter

Planting Geometry and Herbicides for Weed Control in Rice: Implications and Challenges

Written By

Umair Ashraf, Saddam Hussain, Alam Sher, Muhammad Abrar, Imran Khan and Shakeel A. Anjum

Submitted: 02 March 2018 Reviewed: 18 June 2018 Published: 05 November 2018

DOI: 10.5772/intechopen.79579

From the Edited Volume

Grasses as Food and Feed

Edited by Zerihun Tadele

Chapter metrics overview

2,332 Chapter Downloads

View Full Metrics


Weeds are one of the major biological threats to higher rice productivity worldwide. Various cultural, biological, physical and chemical practices affect the composition and intensity of weeds in rice fields. Generally, weeds can be controlled through herbicides; nevertheless, chemical weed control is not a sustainable option on a long term. Various agronomic practices such as the use of tolerant cultivars, adjusting sowing time, tillage permutations and plant geometry may reduce the weed pressure in rice. Integrated approaches for weed management, emphasizing on the combination of management practices and scientific knowledge, may reduce the economic costs and improve weed control owing to the complexity of the weed community. The present chapter reveals the role of planting geometry and herbicides as weed management strategies in rice, and discusses the issue of herbicide resistance associated with chemical weed control. Moreover, the research and knowledge gaps in rice weed management through planting geometry and herbicides were also highlighted.


  • rice
  • planting geometry
  • herbicidal sprays
  • weed management
  • yield

1. Introduction

To declare a plant as a weed means to narrate it with the human environment. Their presence in crops, pastures, lawns, gardens, rangelands, along roads or thoroughfares, parks, recreational areas and other natural lands, interferes with human intensions by changing the native flora/natural vegetation of a region. Hence, human intentions are directly linked to define a weed and their activities endorse weed establishment and dissemination while weed persistence over a period, its type and density, emergence time and its interference period with the crop are directly related to the weed-related losses in crop yields [1]. Both ecological and biological factors of a specific region affect weed composition, distribution and propagation as well as its diversification and occupancy in that region. Interference to the environment often led to multiplication and colonization of plants in open space whose biological activities predispose them. Most of the weed species in annual cropping systems are those which rapidly colonized under disturbed environment [2]. Weed interference and species composition of an area are affected by various environmental and biological factors like soil type, soil moisture, pH, light intensity, temperature, precipitation patterns, crop type, crop competitiveness, crop-weed interference and other flora and fauna of that area. Further, weed interference, its competitive ability and population dynamics changes with weed species composition which further affected by human efforts to control them.

Weeds being the most serious pests in agriculture have the ability to compete with the crop for nutrients through rapid growth and development. Competitive abilities of weeds developed through natural selection make them more vigorous even under severe conditions [3]. Weeds uptake available nutrients and compete with rice plants for water, light and space. Weeds under adverse conditions negatively affect plant growth cycle, plant developmental pattern, leaf architecture, tillering ability, as well as yield and yield attributes of rice [4]. Out of the other factors, poor weed management is also responsible for reduction in rice yield depending on weed type and their infestation [5]. Further, weed management in rice is one of the major causes that affect its crop yield. Normally the decrease in yield due to weeds ranges between 15 and 20%, however; under severe conditions the losses may raise up to 50% or more depending upon the weeds species, types, pressure and intensity [3]. For example, up to 76% reduction in rice grown under puddle conditions is caused due to uncontrolled weeds [6]. The most problematic and common weeds in rice especially in Asia are Cyperus iria, Cyperus maritimus, Echinochloa glabrescens, Cyperus rotundus, Cyperus difformis, Paspalum distichum, Echinochloa colona, Echinochloa crus-galli, and Marsilea minuta [7, 8, 9].

Weed control in rice crop is always remaining a difficult task for successful crop production as their presence in the field cause severe reduction in yield and quality of crops and increase the cost of production [10]. The use of herbicides to control weeds is just in the introductory stage in most of the developing and under developed countries and farmers of these regions also behave rationally in herbicide usage. Among all the weed control methods, chemical weed control is commonly used to overcome weeds infestation which is easy, quick, time saving, cost effective and the most reliable method to control weeds in rice. There are diverse weed communities and types in rice fields. Hence the use of a single herbicide cannot give satisfactory and cost-effective results of weed control [11]. The use of herbicides gives effective control of weeds; hence care must be taken in the selection of herbicide that should be based on the target weed species in addition to their broader category of grass, sedge and broadleaf for planning of an effective weed control program for successful rice production [12]. No doubt, manual weed control is efficient method to control weeds but difficult to apply due to scarcity and rising wages of labor and its dependence on the prevailing weather conditions [13]. Azmi et al. [14] stated that use of herbicides seems a crucial part to control and manage weed infestation in rice. An effective and feasible weed management program is essential to overcome various types of weeds throughout the growing period of crop as manual control of weeds is not a quick method. It requires lot of time and labor as well whilst herbicides offer easy, economical and quick control of weeds if applied in proper dose and at a proper stage of the crop [15].

Not only the weeds pressure, but also the sub-optimal plant population also favors weeds to grow profusely which can be managed by spatial arrangement of crops [4]. The growth, development and the yield of rice as well as the intensity of weed infestation are greatly affected by plant spacing. Planting density in rice strongly influences the growth and development due to its inter-specific competition which affects grain yield [16]. Dense plant population may lead to intra-plant competition whereas lower plant population provides the space for off-types to grow easily [17]. Hossain et al. [18] reported that in too dense populated rice fields, inter- specific competition starts which may cause lodging and gradual shading and results in yield penalty. Hence, it is necessary to adjust suitable plant spacing and plant population as a weed management tool and to get better economic returns.

Integrated weed management is the best option to control weeds whereas cultural weed control is a key component of it [19, 20]. By manipulating the different weed management strategies, the competitive ability of crop over weeds for above and below ground resources can be enhanced [20, 21, 22, 23, 24]. This review comprehends the role of planting geometry and herbicide application as a viable tool for weed management in rice.


2. Weed dynamics and control in rice

Weeds are serious problem to rice production. It accounts for one third of the total crop yield losses due to various biotic factors. Simply, plants that compete and interfere with the desirable crop plants and compete with its growth and development are known as weeds [25]. Weeds are one of the main factors which are responsible for low production of field crops [26, 27, 28]. Weeds compete with crops for available resources like light, space, water as well as nutrients. During early growth stages weeds compete with crop plants vigorously than later growth stages and ultimately cause substantial reduction in growth and yield [29]. For instance, 16–48% grain yield of transplanted rice is reduced due to the occurrence of weed flora in rice field [4]. This weed infestation in rice disturbs the rice growth badly and may result in complete crop failure [30]. So to minimize the weed density, various weed control strategies have been evaluated in rice crop to get maximum output [20, 30]. Moreover, weed competition is more severe in direct seeded than in transplanted rice [13, 31, 32, 33]. Reduction in grain yield of direct seeded rice (DSR), wet seeded rice (WSR) and transplanted rice due to uncontrolled weeds was 75.8, 70.6 and 62.6% respectively [31]. Wet seeded rice refers to the use of pre-germinated seeds as a planting material.

There are about 50 weed species found in rice field causing severe losses in productivity all over the world [33]. Asian sprangletop (Leptochloa chinensis L.) and barnyard grass (Echinochloa crus-galli) quickly establish formal in a very short duration especially where rice is produced by direct seeding [34]. Echinochloa colona L., known as a Jungle rice, grows vigorously in direct seeded rice whilst predominantly found in both direct-seeded and transplanted rice [13, 35, 36].

Juraimi et al. [37] observed that dominance of weed species vary significantly with weed control and different crop establishment methods and reported that E. crus-galli and E. colona are the most problematic weeds found in rice. Moreover, in the upland rice field, Cynodon dactylon and Cyperus rotundus are also serious weeds of rice. The list of most common weeds infesting rice fields are presented in Table 1.

Sr. No. Family Category Weed species
1 Poaceae Grass Paspalum distichum, Echinochloa colona, Leptochloa chinensis, Echinichloa crus-galli, Oryza sativa (weedy rice), Digitaria setigera, Digitaria ciliaris, Eleusine indica, Ischaemum rugosum, and Digitaria ciliaris
2 Cyperaceae Sedge Cyperus rotundus, Fimbristy lismiliacea, Cyperus difformis, and Cyperusiria
3 Commelinaceae Broadleaved Commelina benghalensis
4 Pontederiaceae Monochoria vaginalis
5 Asteraceae Eclipta prostrata
6 Convolvulaceae Ipomoea aquatica
7 Onagraceae Ludwigia octovalvis
8 Sphenocleaceae Sphenoclea zeylanica
9 Onagraceae Ludwigia adscendens

Table 1.

The most common weed species in rice.

Source: [37]

Singh et al. [38, 39] reported a reduction of 12–98% in rice yield due to weed infestation. Threshold levels of Cyperus iria and Echinochloa crus-galli were estimated about 30 and 20 plants m−2 in transplanted rice [40, 41]. A competition study of C. iria in transplanted rice showed that 30 days competition caused 12.9% while a 40 day competition caused 43.5% yield loss in rice [42]. Similarly, about 25 kg ha−1 yield is reduced in direct seeded rice for every day delay in weeding [43]. According to the same study, 35.2% yield reduction was recorded by delaying the removal C. iria for a period of 30–40 days after tillering. At the seedling stage, E. colona and E. crus-galli are closely related to rice plant and may be called as “crop mimicry” that need to control in time [44]. While checking the efficacy of different weed control strategies, Cherati et al. [45] found weed control through herbicides as the best method followed by mechanical weeding without engine, three hand weeding and power mechanical weeding. Chemical and manual weed control measures resulted in similar effect under puddled rice [46]. Anaya [47] and Remington and Posner [43] reported that lack of weed control in fields shared about 12% of total waste production and suggested hand weeding, chemical or mechanical weeding or their combinations for better weed control.


3. Planting geometry: role in weed management and rice yield

In most crops, narrower row spacing can increase the competitiveness of a crop [48] whilst reduced crop spacing has also been found to favor the crop development at the expense of weeds.

Weeds are the serious pest in rice production but these can be managed effectively by maintaining the critical periods of weed competition [11] as growth of the rice is greatly influenced by all the competition periods [49]. Chemical weed control is the most popular weed control method, however herbicide resistance, limited amount of available herbicides, weed population shifts and expensive herbicide products may limit its application in the future [50, 51]. To control weeds more effectively and to minimize the complete reliance on herbicides, adoption of cultural approaches in integrated pest management by farmers has been increasing [14].

Weeds can be suppressed by enhancing the crop competitive ability [52]. Hand weeding is a cultural approach to control weeds but it is a very tedious, labor intensive and slow method [53]. Weed control through herbicides is effective but total dependence on chemical weed control with extensive use of hazardous farm chemicals has necessitated the new approaches to tackle the weeds problems [54]. In addition, the use of herbicides on a large scale has resulted serious ecological threats such as shifts in weed population and dominance of minor weeds [55].

Both yield and yield components of rice are affected by plant spacings as well as planting density [56]. Optimum plant density is necessary to obtain higher yields in rice [57]. The effect of both varied planting patterns and herbicides on weed dynamics in rice is presented in Figure 1. According to Awan et al. [58], the yield of rice was much higher where nursery was transplanted in lines as compared to randomly transplanting. Bozorgi et al. [59] studied three levels of plant spacings i.e., 15 × 15, 20 × 20, and 25 × 25 cm in interaction with number of seedlings per hill and found the highest grain yield from 15 × 15 cm. Furthermore, narrow plant spacing in rice significantly reduced weed pressure and weed dry biomass [60]. Hence, plant spacing in rice determines rice-weed competition and has a crucial role in reducing weed intensity and rice yield (Table 2). Among the three plant spacings (20 × 10, 25 × 15, 30 × 20 cm), the efficiency of weed control was the highest (62.03%) in 20 × 10 cm at 30 days after transplanting (DAT), while the lowest (55.03%) at 60 DAT [17]. Ehsanullah et al. [16] studied four rice sowing methods and concluded that the highest grain yield (3.06 t ha−1) was obtained from 20 × 20 cm spacing while the lowest of 2.52 t ha−1 from direct seeding by broadcasting the seeds in the standing water. Rasool et al. [67] estimated the impacts of three plant spacings (15 × 15, 15 × 20, 20 × 20 cm) on yield and yield components of rice and observed maximum plant height, total number of tillers, leaf area index (LAI) and total dry matter accumulation from 15 × 15 cm which provided 8.97% higher yield than the 20 × 20 cm spacing. Similarly higher grain yield was obtained in 50 hills m−2 and the paddy yield record obtained due to high planting density over 16.7, 22.2, 25 and 33.3 hills m−2 were 4.0, 9.5, 4.8 and 6.0%, respectively [68]. Moreover, number of panicle per plant and straw yield of rice increased significantly by raising planting density in rice [69]. Tari et al. [70] concluded that rice sown at the spacing of 20 × 20 cm and the application fertilizer (138 kg N ha−1) gave maximum yield. Out of three spacings investigated (5 × 15, 15 × 20 and 15 × 25 cm), the highest yield and harvest index were recorded for rice from 15 × 20 cm [71]. Sultana et al. [72] evaluated the effect of five hill to hill spacings viz. 2.5, 5, 10, 15 and 20 cm and two row spacings viz. 20 and 25 cm where the highest grain yield was recorded at 25 × 15 cm and the lowest at 20 × 2.5 cm spacing. Further studies using four row spacings (10 × 25, 15 × 25, 20 × 25, and 25 × 25 cm) resulted in significant improvements in rice yield and related components from 15 × 25 cm spacing with two seedlings per hill with four levels of seedlings per hill were assessed by Alam et al. [73]. In addition, vigorous growth and better yield of rice was harvested from the spacing of 22.5 × 22.5 cm2 compared to that of 20 × 20 cm2 and 25 × 25 cm2 [74]. The yield of rice was found higher in widest plant spacing i.e., 20 × 20 cm than the narrow plant spacings i.e., 20 × 15 cm and 10 × 10 cm.

Figure 1.

Effect of differnt planting patterns and early post emergence herbicides on total weed density, and weed dry biomass at 35 and 50 days after transplanting (DAT) (a-d). Bars above means represent S.E. of three replicates. WC: weedy check; Bisp WP: Bispyribac sodium 20% WP at 39.50 g a.i. ha−1; Bisp SC: Bispyribac sodium 100 SC at 39.50 g a.i. ha−1; Clf-but: Cyhalofop-butyle 10% EC at 49.50 g a.i. ha−1; Penox: Penoxulam 240 EC at 15 g a.i. ha−1 [64].

Sr. No. Rice establishment method Widest spacing Narrowest spacing Remarks References
1 DSR 20 × 20 cm 10 × 10 cm Under weed free conditions, yield was 29% higher in the plot with 10 cm row spacing than 20 cm whereas grain yield 87–88% higher than uncontrolled weedy plots. [3]
2 TR 20 × 20 cm 15 × 15 cm 24.31% higher yield was recorded in widest spacing of 20 × 20 cm compared with narrow spacing of 15 × 15 cm. whilst 36.63% increase in paddy yield was observed in weed free treatment compared with weedy check. [4]
3 TR 20 × 10 cm 30 × 20 cm Among the spacing, the widest spacing gave maximum weed control efficiency (55.30%) at 30 DAT and lowest weed control efficiency (62.03%) at 60 DAT. [17]
4 TR 20 × 10 cm 20 × 10 cm Adoption of 20 × 10 cm spacing and pre emergence application of anilofos 2, 4-D at 6 days after transplanted supplemented with 2, 4-D Na salt at 20 days after transplanted generally enhanced rice yield from 58.13 to 70.41%. [29]
5 DSR 10 × 10 cm 30 × 30 cm Rice spacing determines rice-weed competition and can play a decisive role to minimize weed pressure. Closer spacing could be considered as a vital tool in integrated weed management program for aerobic rice. 51.79 and 70.68% increase in weed dry biomass was observed for 10 × 10 cm and 30 × 30 cm, respectively. Up to 50% increase in rice yield was recorded for narrow spacing compared with wide spacing [60]
6 TR 20 × 20 cm 15 × 15 cm The maximum weed density and dry biomass was found in widest spacing, nevertheless, the yield was also remained higher in widest spacing with 19.55% more than the closest. [4]
7 DSR 30 × 30 cm 20 × 20 cm The weed population especially E. colona and E. crus-galli was 29% more in widely spaced crop than narrow spacing whilst 18.68 and 23.45% higher grain yield was recorded in narrowest spacing than wide spacing for E. colona and E. crus-galli, respectively. [61]
8 DSR 30 × 30 cm 15 × 15 cm Rice grown in 30 cm row spacing has 32–35% greater weed biomass and 38–50% less yield as compared with 15 cm. [62]
9 TR 25 × 10cm 20 × 10 cm Short duration of ‘aman’ rice transplanted at 25 × 15 cm with three hand weedings gives 193% total dry matter than 20 × 10 cm with weedy control. [63]
10 TR 10 × 10 cm 10 ×10 cm Grain yield was remained lower up to 25% in narrowest plant spacing than widest spacing. Lower grain yield could be due to intra specific competition in rice. [64]
11 DSR & TR 25 × 15 cm 20 × 10 cm Narrow row spacing in both DSR and TR resulted in higher grain productivity from 4.7 to 12.2% with reduced weed density. [65]
12 SRI 30 × 30 cm 25 × 25 cm The rice yield in closer spacing was 19.50% more than wider. Further, weed control through anilophos at 0.4 kh ha−1 gave higher yield than weedy check. [66]

Table 2.

Planting geometry-induced changes in weed density and yield of direct seeded and transplanted rice.

DSR: Direct seeded rice, TR: Transplanted rice, SRI: System of rice intensification

The performance of rice established under different planting geometries was investigated by Ashraf et al. [4] where a maximum yield of 5.87 t ha−1 was obtained using Machete 5G and GGR-6 under plant spacing 20 × 20 cm. Furthermore, Jacob et al. [75] concluded that 20 × 10 cm spacing with the application of anilofos+2, 4-DEE (ready mix) 0.40 + 0.53 kg ha−1 supplemented with 2, 4-D sodium salt 1 kg ha−1 provided the maximum grain yield and minimum weed competition. Hence, spatial arrangement of crop plants is the best cultural practice to reduce weed competition and raise rice yield.


4. Weed control in rice using herbicides

Herbicides are chemicals that either kill or inhibit growth of plants. They can be classified in numerous ways viz; by crop (e.g., a soybean herbicide), by their application timing (e.g., pre- or post- emergence to the crop or weeds), by their chemical family (e.g., sulfonylureas, dinitroanilines), by their path of mobility in the plant (e.g., translocation by phloem, xylem, or both), and by their mode of action (MOA) (e.g., photosystem II inhibitors, ALS inhibitors). In the context of herbicide resistance in crops and weeds, MOA is the most relevant classifier because it best describes the means by which the herbicide imposes selection pressure on weeds, and its manipulation can be used for herbicide resistant weed management. More than 200 active ingredients are registered as herbicides around the world, and this estimate does not include compounds that are used exclusively as crop growth regulators or crop desiccants. There are, however, only 29 major mechanisms of herbicide action, including a group of herbicides for which the MOA is unknown [76]. The herbicides are very specific for their mode of action and differ in their weed control efficacy (Table 3).

Sr No. Herbicide Class Herbicide name Mode of action Weed efficacy References
1 Post emergence Pyrazosulfuron ethyl ALS inhibitor An increase of 87–188% was recorded in rice yield in herbicide treated plots than weedy check (control). [3]
2 Pre emergence Pretilachlor Selective Among all treatments, 79.53% weed control was obtained by application of pretichlor at 30 DAT. [17]
3 Pre emergence Butachlor Selective, systemic herbicide. Weed dry biomass was 56.92% less in treatment having machete (butachlor) application over weedy check. [4]
Ethoxysulfuron ALS inhibitor
Post emergence Penoxsulam ALS inhibiting
Early emergence and post emergence Cyhalofop-butyl Contact and translocated
4 Pre+Post emergence Pendimethalin-followed by- bispyribac-sodium + azimsulfuron ALS inhibitor Application of these herbicide provided 85% weed control over other herbicides with minimum weed dry biomass. [63]
5 Post emergence Penoxsulam ALS inhibiting Penoxsulam gives excellent control of Echinochloa spp resulting 19–40% increase in rice yield. [97]
6 Pre and post emergence Isoproturon + 2, 4-D Selective systemic herbicide Rice yield was 11–15% higher and 0.19 more B:C ratio (net monetary return) than weedy control [109]
7 Pre emergence Butachlor Selective, systemic herbicide All the herbicides reduced more than 80% weed density and 74–87% [110]
Pretilachlor Selective
Pendimethlane Microtubule assembly inhibition
8 Pre emergence Pretilachlor Selective Rotational use of pretilachlor with butachlor reduces sedges population and increased paddy yield by 3–5%. [111]
9 Pre emergence Pendimethlane Microtubule assembly inhibition Highest yield attributes and grain yield 62.8% (q ha−1) were recorded in treated plots. Uncontrolled weed caused 98.64% reductions in grain yield. [112]
Pre emergence Pretilachlor Selective
Post emergence Quinclorac Synthetic Auxin
10 Post emergence Penoxsulam ALS inhibiting In herbicide treated plots grain yield was 75–88% and 81–93% better weed control as compared to other treatments [113]
11 Early emergence and post emergence Cyhalofop-butyl Contact, translocated In herbicide treated plots 27–41% higher grain yield was obtained as compared to control providing 75–93% weed control [113]

Table 3.

Herbicides differ for their class, name, mode of action and weed control efficacy.

Chemical weed control is becoming priority for farmers due to mainly shortage of labor for hand weeding [77]. Rising wages of labor and their non-availability at peak time discourage hand weeding and make it necessary to use alternative methods of weed control including herbicides [13, 33, 78]. Hence, the importance of herbicides cannot be ignored as it is the most effective, time saving and reliable weed control technology available today [79]. Weedicides can suppress weeds effectively and may provide a weed free environment if applied at proper stage and time [80]. Chemical weed control has an edge over cultural weed control as it is quick, cost effective and saves labor, time and money. So, it may be regarded as an economical method of weed control [81].

The doses of registered herbicides under changing weed composition and density as well as different growth stages may be overestimated to get maximum weed control [82]. Manufacturers recommend higher doses of herbicides than the optimum dose which controls the weed population at satisfactory level [83]. The rate of herbicide to be applied depends on the type of weed flora, the density of weed population, phenological development of both the weed and the crops and the prevailing environmental conditions of the location. Keeping the weed density below the threshold level instead complete removal is considered best as it is also an ecological approach of weed management [84]. Various herbicides give satisfactory weed control without reducing yield and increasing weed population pressure even if applied at lower rates [85, 86, 87, 88]. Weed control efficiency at reduced dose of herbicide tend to be lower than recommended doses, although in many cases it may be 60–100% and acceptable commercially [82]. Application of both pre and post emergence herbicides at proper dose suppress weed flora effectively, however, the use of a single herbicide rarely gives an effective weed control in rice [78].

Rao et al. [13] suggested various herbicides packages like penoxsulam, bensulfuron, carfentrazone, molinate, bentazone, clomazone, pyrazosulfuron, fenoxaprop, propanil, bispyribac-sodium and cyhalofop-butyl control weeds in rice. Further, Pacanoski and Glatkova [89] reported that herbicides i.e., propanil + bentazon, mefenacet + bensulfuron-methyl, penoxsulam, and azimsulfuron + adjuvant controlled Cyperus rotundus, Echinochloa crus-galli effectively in rice. Similarly, Kawana [90] indicated that weeds such as L. chinensis and I. rugosum can were effectively controlled using cyhalofop-butyl and bispyribac-sodium, respectively. Herbicide treatments applied with bispyribac-sodium substantially suppressed dry weight and density of weeds as compared to penoxsulam and resulted in maximum marginal rate of return [91]. Bispyribac-sodium is the most effective to the small and actively growing weeds especially against barnyard grass (alligator weed) when applied as an early post emergence herbicide applied at the 3-leaf stage of rice [92]. Both bispyribac-sodium and penoxsulam herbicides in suspension concentrate (SC) formulation were applied in combination with ethoxysulfuron as post emergence and found that bispyribac-sodium + ethoxysulfuron gave better weed control in rice [93]. Saini et al. [94] found that cyhalofop-butyl at 90 g ha−1 caused significant reduction in dry matter accumulation and growth of weeds. Post-emergence application of bispyribac-sodium with metsulfuron methyl after pre-emergence application of oxyfluorfen gave the highest weed control index in fine rice [95]. Application of pendimethalin followed by bispyribac-sodium and penoxsulam reduced weed density up to 80% in rice [91], whereas application of cyhalofop-butyl at 80 g ha−1 effectively controlled Echinochloa colona [96]. On the other hand, post emergence application of penoxsulam effectively controlled barnyard grass (Echinochloa crus-galli) but was inefficient in controlling broadleaf weeds. In contrary, the combination of penoxsulam and cyhalofop-butyl was ineffective in controlling grassy weeds [97]. Moreover, the total weed density was significantly reduced using bispyribac-sodium and cyhalofop butyl herbicides although the former caused a slight recoverable injury to the rice plant [98]. Bispyribac sodium at 30 g a.i. ha−1 reduced the density and biomass of weeds by up to 75 and 80%, respectively; hence, its application as a post emergence herbicide proved as a viable strategy of weed control in rice [99]. In direct seeded rice, the lowest weed dry biomass was recorded using the combination of bispyribac-sodium and pretilachlor [100]. The use of bispyribac-sodium at 30 g a.i. ha−1 suppressed various types of weeds which includes broad leaf weeds, grasses and sedges; hence enhanced the grain and straw yield of rice by up to 17.45 and 12.30%, respectively compared to the weedy check [101]. Application of herbicide mixtures proved better regarding weed control than single herbicide application at critical weed competition periods [102].

Chauhan et al. [103] evaluated the efficacy of different post emergence herbicides viz. penoxsulam + cyhalofop, fenoxaprop + ethoxy sulfuron (in combination) and bispyribac-sodium (alone) on four different types of weeds i.e., E. colona, Digitaria ciliaris, Leptochloa chinensis and E. crus-galli by applying it at four, six and eight-leaf stages. Fenoxaprop + ethoxy sulfuron gave more than 97% weed control in all weed species under study. Moreover, early application of post emergence herbicides provided high weed control than late application whilst fenoxaprop + ethoxy sulfuron controlled Digitaria ciliaris and Leptochloa chinensis, penoxsulam + cyhalofop controlled Leptochloa chinensis and bispyribac-sodium controlled E. colona effectively. Furthermore, both bispyribac-sodium and anilophos were effective against broadleaf and narrow leaf weeds. Bispyribac-sodium reduced the density of Alternanthera philoxeroides, Ammania sp.,Commelina diffusa, C. difformis, C. iria, and D. junceum while anilophos controlled Cyperus difformis, C. sanguinolentus, and C. iria effectively. However, high weed density led to significant reductions in tiller production and grain yield in rice [104]. Application of bensulfuron, bispyribac-sodium and cyhalofop-butyl at early growth stage followed by Bentazon/2-methyl-4-chlorophenoxyacetic acid (MCPA) at mid growth stage control weeds effectively with increased productivity of rice [105]. Different herbicides viz. ethoxy sulfuron, cyhalofop-butyl, chlorimuron, metsulfuron, bispyribac-sodium and penoxsulam controlled different types of weeds effectively in dry seeded rice [37, 106, 107]. Hussain et al. [108] reported that bispyribac-sodium and ethoxy sulfuron were efficient with 90 and 87% weed control efficiency, respectively in rice. They further reported that maximum paddy yield and net benefits were obtained where bispyribac-sodium was applied followed by ethoxysulfuron while the lowest were recorded from weedy check.

Herbicides such as penoxsulam, ethoxysulfuron and butachlor, ethoxysulfuron were considered the most efficient with 93% reduction in weed density in rice [109]. Bispyribac-sodium and penoxsulam at 25 g ha−1 controlled weeds effectively in rice [107]. Penoxsulam (15 g a.i. ha−1) as post emergence was better in suppressing weed density and biomass than pendimethalin (825 g a.i. ha−1) as pre-emergence in rice [110].

On the other hand, the study by Khaliq et al. [91] using five pre- and post-emergence herbicides resulted in unexpected outcome. In this case, not only the germination rate of the two dominant weeds i.e., jungle rice and purple nut sedge were significantly reduced but also the germination and root-shoot growth of rice were negatively affected. This shows that these herbicides caused seedling mortality to both the weed and the crop irrespective of the time of application as a pre-emergence or post emergence.

Khaliq et al. [93] studied the efficacy of tank mixed pre- and post-emergence herbicides on weed control in rice. In this case, pendimethalin herbicide was tank mixed with ethoxy sulfuron ethyl at 1137 and 30 g a.i. ha−1 and applied as pre-emergence, respectively. Similarly, pyrazosulfuron ethyl, penoxsulam and bispyribac-sodium at 30, 15, 30 g a.i. ha−1were also tank mixed with ethoxysulfuron ethyl at the same concentration, respectively and applied as post emergence. The findings of this work showed that the weed control was higher for ethoxy sulfuron with bispyribac-sodium combination than all other combinations. In general, different herbicide mixtures can be used for better weed control in rice.


5. Weed resistance to herbicides

Herbicide resistance is the heritable capacity for plants to grow and reproduce after herbicide treatment that would have been fatal to all but one or a very few progenitors in an antecedent population. Herbicide resistant weeds occur in both herbicide-resistant crops and conventional crops in response to selection pressure from a specific herbicide. A herbicide selects plants with natural genetic resistance to that MOA. The mechanism of herbicide MOA has been depicted in Figure 2. Those plants survive and reproduce, and if selection by the herbicide continues for several generations, the population of the resistant weed biotype increases until there is a noticeable population of weeds that herbicide will no longer control that biotype. On the other hand, both transgenic and non-transgenic herbicide-resistant crop cultivars are resistant to specific herbicides because they have been bred to survive the action of herbicide. Therefore, susceptible crop genotypes are killed by a specific herbicide while the resistant cultivars survive. When the identity of a conventional cultivar is mistaken for a resistant cultivar in the field, the conventional cultivar is killed or severely injured by the herbicide that the resistant cultivar resists without adverse effects.

Figure 2.

Herbicide class and its mode of action as defined by Herbicide Resistance Action Committee (HRAC; Herbicides target different cellular strucures and functions and are very specific in their mechanism of action in plants. Source: [115].

Resistance of weeds to various herbicides is a well-known phenomenon but not as much focused as resistance to insecticides or fungicides [111]. Most often it is misunderstood that resistance is a problem caused by a particular active ingredient but it results from agronomic systems which totally depend on herbicides to control weeds [76]. Herbicides commonly used in rice mostly relate to acetyl co-enzyme A carboxylase (ACCase) inhibitors, acetolactate synthase (ALS), thiocarbamates, synthetic auxins and amides due to which herbicide resistance has become a serious problem in many regions [112]. Zein et al. [111] observed the evolutionary resistance of Echinochloa colonum during the years 2005–2007 against bispyribac-sodium when applied to both susceptible and resistant biotypes of Echinochloa colonum. Riar et al. [44] found some resistant populations of Echinochloa crus-galli to bispyribac-sodium and penoxsulam. El-Nady et al. [113] investigated the physiological and anatomical differences between the susceptible and resistant biotypes of Echinochloa colonum and resulted that GR50 of resistant biotype was 10.2 times greater than susceptible biotype of Echinochloa colonum where bispyribac-sodium was applied. Rahman et al. [114] tested cyhalofop-butyl, quinclorac and propanil against 10 populations of Echinochloa crus-galli which were collected from rice field. They concluded from the ED50 values from the dose–response experiment that resistant biotypes were 4, 10 and 17 times resistant to propanil, quinclorac and cyhalofop-butyl, respectively. Regular monitoring and early detection of the evolution and mechanism of herbicide resistance and by adopting some suitable management strategies usefulness of herbicides may be enhanced otherwise weed control through herbicides might be at a high risk in future [116, 117].


6. Conclusions and future needs

Weeds being the most serious pests in agriculture have the ability to compete with the crop for available resources through rapid growth and development. Competitive abilities of weeds developed through natural selection make them more vigorous even under severe conditions. Weed control in rice crop is always remaining a difficult task for successful crop production as their presence causes severe reduction in yield and quality of crops thus increasing the cost of production. Among all the weed control methods, chemical weed control is commonly used to overcome weed infestation which is easy, quick, time saving, cost effective and the most reliable method to control weeds. There are diverse weed communities and types in rice fields. Hence, the use of a single herbicide cannot give satisfactory and cost-effective results of weed control. Not only the weeds pressure, but also the sub-optimal plant population favors weeds to grow profusely. Planting density significantly influences the growth and development as well as grain yield of rice due to its inter-specific competition. Dense plant population may lead to intra-plant competition whereas low plant population provides the space for off-types to grow easily. Integrated weed management is the best option to control weeds. By manipulating diverse weed management strategies, the competitive ability of crop over weeds for the above and below ground resources can be enhanced. Regular monitoring and early detection of the evolution and mechanism of herbicide resistance is necessary. The adoption of suitable management strategies on herbicide is also important. Hence, in the future, researchers need to develop integrated weed management strategies along with effective herbicides which do not only favor crop yield and reduce weed infestation but also discourage the resistance of weed flora to herbicides.


  1. 1. Fahad S, Hussain S, Chauhan BS, Saud S, Wu C, Hassan S, Tanveer M, Jan A, Huang J. Weed growth and crop yield loss in wheat as influenced by row spacing and weed emergence times. Crop Protection. 2015;71:101-108
  2. 2. Rabbani N, Bajwa R, Javaid A. Interference of five problematic weed species with rice growth and yield. African Journal of Biotechnology. 2011;10:1854-1862
  3. 3. Khaliq A, Matloob A, Chauhan BS. Weed management in dry-seeded fine rice under varying row spacing in rice wheat system of Punjab, Pakistan. Plant Production Science. 2014;17(4):321-332
  4. 4. Ashraf U, Anjum SA, Ehsanullah KI, Tanveer M. Planting geometry induced alteration in weed infestation, growth and yield of puddled rice. Pakistan Journal of Weed Science Research. 2014;20(1):77-89
  5. 5. Mustafa S, Sohail R, Muhammad A, Akash Z, Adeel M, Muhammad MJ. Weed management in transplanted rice through different weedicides at rice research station Bahawalnagar. Asian Journal of Plant Science and Research. 2017;7(3):11-13
  6. 6. Singh VP, Govindra S, Mahendra S. Effect of fenoxaprop-p-ethyl on transplanted rice and associated weeds. Indian Journal of Weed Science. 2004;36:190-192
  7. 7. Sandeep N, Singh S, Panwar KS, Malik RK, Narwal S, Singh S. Performance of acetachlor and anilofos+ethoxysulfuron for weed control in transplanted rice (Oryza sativa). Indian Journal of Agronomy. 2002;47:67-71
  8. 8. Rekha KB, Raju MS, Reddy MD. Effect of herbicides on weed growth, grain yield and nutrient uptake in rain fed low land rice. Indian Journal of Weed Science. 2003;35:121-122
  9. 9. Chin DV. Biology and management of barnyard grass, red sprangletop and weedy rice. Weed Biology and Management. 2001;1:37-41
  10. 10. Mahmood K, Subhani S, Chaudhry MA, Ghafoor A. Impact of various packages of herbicides use on yield of transplanted rice. International Journal of Agriculture and Biology. 2000;2:141-143
  11. 11. Khaliq A, Matloob A. Weed-crop competition period in three fine rice cultivars under direct-seeded rice culture. Pakistan Journal of Weed Science Research. 2011;17:229-243
  12. 12. Rahman M, Juraimi AS, Jayasuria ASM, Man AB, Anwar P. Response of weed flora to different herbicides in aerobic rice system. Scientific Research and Essays. 2012;7:12-23
  13. 13. Rao AN, Jhonson DE, Sivaprasad V, Ladha JK, Mortimer AM. Weed management in direct seeded rice. Advances in Agronomy. 2007;93:153-155
  14. 14. Azmi M, Chin DV, Vongsaroj P, Johnson DE. Emerging issues in weed management of direct seeded rice in Malaysia, Vietnam and Thailand. In: Rice Is Life: Scientific Perspectives for the 21st Century, Proceedings of the World Research Conference; 4-7 November 2004; IRRI & Tsukuba, Japan: International Research Center for Agricultural Sciences; 2005. pp. 196-198
  15. 15. Kumar M, Sharma G. Effect of herbicides alone and in combination on direct seeded rice. Indian Journal of Weed Science. 2005;37:197-201
  16. 16. Ehsanullah AN, Jabran K, Habib T. Comparison of different planting methods for optimization of plant population of fine rice (Oryza sativa L.) in Punjab (Pakistan). Pakistan Journal of Agricultural Sciences. 2007;44:597-599
  17. 17. Ali M, Sardar MSA, Biswas PK, Mannan AKMSB. Effect of integrated weed management and spacing on the weed flora and on the growth of transplanted aman rice. International Journal of Sustainable Crop Production (IJSCP). 2008;3:55-64
  18. 18. Hossain MS, Mamun AA, Basak R, Newaj MN, Anum MK. Effect of cultivar and spacing on weed infestation and performance of transplanted aman rice in Bangladesh. Pakistan Journal of Agronomy. 2003;2:169-178
  19. 19. Ghadiri H, Bayat ML. Effect of row and plant spacings on weed competition with pinto beans (Phaseolus vulgaris L.). Journal of Agricultural Science and Technology (JAST). 2004;6:1-9
  20. 20. Chauhan BS, Migo T, Westerman PR, DE J. Post-dispersal predation of weed seeds in rice fields. Weed Research. 2010;50:553-560
  21. 21. O’Donovan JT, Harker KN, Clayton GW, Newman JC, Robinson D, Hall LM. Barley seeding rate influence the effects of variable herbicide rates. Weed Science. 2001;49:746-754
  22. 22. Weiner J, Gripenentrog HE, Kristensen L. Suppression of weeds by spring wheat (Triticum aestivum) increases with crop density and spatial uniformity. Journal of Applied Ecology. 2001;38:784-790
  23. 23. Grichar WJ, Bessler BA, Brewer KD. Effect of row spacing and herbicide dose on weed control and grain sorghum yield. Crop Protection. 2004;23:263-267
  24. 24. Shinggu CP, Dadari SA, Shebayan JAY, Adekpe DI, Mahadi MA, Mukhtar A, Asala SW. Influence of spacing and seed rate on weed suppression in finger millet (Eleucine carocana). Middle East Journal of Scientific Research. 2009;4:267-270
  25. 25. Qureshi R, Waheed A, Arshad M. Weed communities of wheat crop in district Toba Tek Singh, Pakistan. Pakistan Journal of Botany. 2009;41:239-245
  26. 26. Jakhar GS, Mahar AQ, Abro SA, Qureshi R. Weed communities of wheat crop under diverse Edaphography of District Khairpur. Pakistan Journal of Botany. 2005;37:709-714
  27. 27. Marwat SK, Khan MA, Ahmad M, Zafar M, Rehman FU. Ethnophyto medicines for treatment of various diseases in D. I. Khan District. Sarhad Journal of Agriculture (SJA). 2008;24:305-315
  28. 28. Abbas RN, Tanveer A, Ali A, Zaheer ZA. Simulating the effect of Emex australis densities and sowing dates on agronomic traits of wheat. Pakistan Journal of Agricultural Sciences. 2010;47:104-110
  29. 29. Jacob D, Syriac EK. Performance of transplanted scented rice (Oryza sativa L.) under different spacing and weed management regimes in southern Kerala. Journal of Tropical Agriculture. 2005;43:71-73
  30. 30. Phuong LT, Denich M, Vlek PLG, Balasubramanian V. Suppressing weeds in direct-seeded lowland Rice: Effects of methods and rates of seeding. Journal of Agronomy and Crop Science. 2005;191:185-194
  31. 31. Singh S, Singh G, Singh VP, Singh AP. Effect of establishment methods and weed management practices on weeds and rice in rice-wheat cropping system. Indian Journal of Weed Science. 2005;37:51-57
  32. 32. Savary S, Castilla NP, Elazegui FA, Teng PS. Multiple effects of two drivers of agricultural change, labour shortage and water scarcity, on rice pest profiles in tropical Asia. Field Crops Research. 2005;91:263-271
  33. 33. Rao AN, Nagamani A. Available technologies and future research challenges for managing weeds in dry-seeded rice in India. In: Proceedings of the 21st Asian Pacific Weed Science Society Conference; 2-6 October 2007; Colombo, Sri Lanka: Asian Pacific Weed Science Society; 2007. pp. 391-401
  34. 34. Allard JL, Kon KF, Morishima Y, Kotzian R. The crop protection industry’s view on trends in rice crop establishment in Asia and their impact on weed management techniques. In: Rice Is Life: Scientific Perspectives for the 21st Century, Proceedings of the World Research Conference; 4-7 November 2004; Tsukuba, Japan; 2005. pp. 205-208
  35. 35. Caton BP, Mortimer M, Hill JE, Johnson DE. A practical guide to weeds of rice in Asia. 2nd ed. Los Baños, Laguna, Philippines: International Rice Research Institute (IRRI); 2004. p. 58
  36. 36. Dubey V. Ecology of jungle rice (Echinochloa colonum), a weed of rice agro-ecosystems: A case study in Bilaspur (Chhattisgarh). International Rice Research Notes. 2004;29:52-55
  37. 37. Juraimi AS, Begum M, Yusuf MNM, Man A. Efficacy of herbicides on the control weeds and productivity of direct seed rice under minimal water conditions. Plant Protection Quarterly. 2010;25:19-25
  38. 38. Singh Y, Singh VP, Singh G, Yadav DS, Sinha RKP, Jhonson DE, Mortimer AM. The implications of land preparation, crop establishing method and weed management on rice yield variation in the rice-wheat system in the indo-genetic plains. Field Crops Research. 2011;121:64-74
  39. 39. Singh JKL, Guptaa RK, Bhushana L, Raob AN. Weed management in aerobic rice systems under varying establishment methods. Crop Protection. 2008;27:660-671
  40. 40. Singh KP, Angaris NN. Ecophysiological studies of Cyperus irria L. in transplanted rice under mid hill conditions of Himachal Pradesh, Indian. Physiology and Molecular Biology of Plants. 2003;9:283-285
  41. 41. Singh KP, Angaris NN. Studies on threshold level of Echinochloa crus-galli L. in transplanted rice under mid hill conditions of Himachal Pradesh. Advances in Plant Sciences. 2008;21:505-508
  42. 42. Dhammu HS, Sandhu KS. Critical period of Cyperus iria L. competition in transplanted rice. In: Proceedings of 13th Australian Weeds Conference: Weeds “Threats Now and Forever?”; 8-13 September 2002; Perth, Western Australia: Plant Protection Society, Sheraton Perth Hotel; 2002. pp. 79-82
  43. 43. Remington TRJ, Posner L. On-farm evaluation of weed control technologies in direct seeded rice in the Gambia. In: Starkey P, Simalenga T, editors. Animal Power for Weed Control. Wageningen, the Netherlands: Technical Centre for Agricultural and Rural Cooperation, Animal Traction Network for Eastern and Southern Africa; 2000. pp. 255-261
  44. 44. Riar DS, Norsworthy JK, Bond JA, Bararpour MT, Wilson MJ, Scott RC. Resistance of Echinochloa crus-galli populations to Acetolactate synthase-inhibiting herbicides. International Journal of Agronomy. 2012;2012:1-8
  45. 45. Cherati FE, Bahrami H, Asakereh A. Evaluation of traditional, mechanical and chemical weed control methods in rice fields. Australian Journal of Crop Science. 2011;5:1007-1013
  46. 46. Prasad SM, Mishra SS, Sing SJ. Effect of establishment methods, fertility levels and weed management practices on rice (Oryza sativa). Indian Journal of Agronomy. 2001;46:216-221
  47. 47. Anaya AL. Allelopathy as a tool in the management of biotic resources. Critical Reviews in Plant Sciences. 2003;19:697-739
  48. 48. Norsworthy JK, Oliveria MJ. Sicklepod (Senna obtusifolia) germination and emergence as affected by environmental factors and seeding depth. Weed Science. 2006;54(5):903-909
  49. 49. Irshad A, Cheema ZA. Growth analysis of transplanted fine rice under different competition durations with barnyard grass. International Journal of Agriculture and Biology. 2002;4:123-126
  50. 50. Buhler DD, Liebman M, Obrycki JJ. Review: Theoretical and practical challenges to an IPM approach to weed management. Weed Science. 2002;48:274-280
  51. 51. Johnson DE, Mortimer AM. Issues for weed management in direct-seeded rice and the development of decision-support frameworks. In: Singh Y, Singh VP, Chauhan B, Orr A, Mortimer AM, Johnson DE, Hardy B, editors. Direct Seeding of Rice and Weed Management in the Irrigated Rice-Wheat Cropping System of the Indo-Gangetic Plains. Los Banos (Philippines)/Pantnagar (India): International Rice Research Institute/Directorate of Experiment Station, G.B Pant University of Agriculture and Technology; 2008. pp. 223-228
  52. 52. Gibson KD, Fischer AJ, Foin TC, Hill JE. Implications of delayed Echinochloa spp. germination and duration of competition for integrated weed management in water-seeded rice. Weed Research. 2002;42:351-358
  53. 53. Khan BM, Asif M, Hussain N, Iqbal M. Agro-economic impact of different weed management strategies in wheat. Journal of Research and Science. 2000;11:46-49
  54. 54. Jodaugiene D, Pupaliene R, Urboniene M, Prankietis V, Prankietiene I. The impact of different types of organic mulches on weed emergence. Agronomy Research. 2006;4:197-101
  55. 55. Heap I. Global perspective of herbicide‐resistant weeds. Pest Management Science. 2014;70(9):1306-13015
  56. 56. Hassanuzzaman M, Rehman MI, Roy TS, Ahmed JU, Zobaer ASM. Plant characters, yield components, and yield of late transplanted aman rice as affected by plant spacing and number of seedlings per hill. Advances in Biological Research (ABR). 2009;3:201-207
  57. 57. Kumar A, Mishra BN, Mishra PK. Effect of age of seedlings and plant density on growth and yield of hybrid rice. Annals of Agricultural Research. 2002;23(3):381-386
  58. 58. Awan TH, Ahmad M, Ashraf MM, Ali I. Effect of different transplanting methods on paddy yield and its components at farmer’s field in rice zone of Punjab. Journal of Animal and Plant Science. 2011;21:498-502
  59. 59. Bozorgi HR, Faraji A, Danesh RK, Keshavarz A, Azarpour E, Tarighi F. Effect of plant density on yield and yield components of rice. World Applied Sciences Journal. 2011;12:2053-2057
  60. 60. Sunyob NB, Juraimi AS, Rahman MM, Anwar MP, Man A, Salamat A. Planting geometry and spacing influence weed competitiveness of aerobic rice. Journal of Food, Agriculture and Environment. 2012;10:330-336
  61. 61. Chauhan BS, Johnson DE. Implications of narrow crop row spacing and delayed Echinochloa colona and Echinochloa crus-galli emergence for weed growth and crop yield loss in aerobic rice. Field Crops Research. 2010;117(2):177-182
  62. 62. Chauhan BS, Johnson DE. Row spacing and weed control timing affect yield of aerobic rice. Field Crops Research. 2011;121:226-231
  63. 63. Singh V, Jat ML, Ganie ZA, Chauhan BS, Gupta RK. Herbicide options for effective weed management in dry direct-seeded rice under scented rice-wheat rotation of western indo-Gangetic Plains. Crop Protection. 2016;81:168-176
  64. 64. Ashraf U, Abbas RN, Hussain S, Mo ZW, Anjum SA, Khan I, Tang XR. Consequences of varied planting geometry and early post emergence herbicides for crop-weed interventions in rice under semi-arid climate. Planta Daninha. 2016;34:737-746
  65. 65. Dass A, Shekhawat K, Choudhary AK, Sepat S, Rathore SS, Mahajan G, Chauhan BS. |Weed management in rice using crop competition-a review. Crop Protection. 2017;95:45-52
  66. 66. Nain S, Dinesh K, Thenua OVS, Tyagi VK. Influence of spacing and weed management on rice (Oryza sativa) varieties under system of rice intensification. Indian Journal of Agronomy. 2012;57:138-142
  67. 67. Rasool F, Habib R, Bhat MI. Evaluation of plant spacing and seedlings per hill on rice (Oryza sativa L.) productivity under temperate conditions. Pakistan Journal of Agricultural Sciences. 2012;49:169-172
  68. 68. Asmamaw BA. Effect of planting density on growth, yield and yield attributes of rice (Oryza sativa L.). African Journal of Agricultural Research (AJAR). 2017;12(35):2713-2721
  69. 69. Amin M, Khan MA, Khan EA, Ramzan M. Effect of increased plant density and fertilizer dose on the yield of rice variety ir-6. Journal of Research and Science. 2004;15:9-16
  70. 70. Tari DB, Pirdashti HA, Nasiri M. Investigation some agronomical traits of rice under different transplanting dates, planting spacing. World Applied Sciences Journal. 2009;6:1021-1027
  71. 71. Uddin MJ, Ahmed S, Rashid MH, Hasan MM, Zaman MA. Effect of spacings on the yield and yield attributes of transplanted aman rice cultivars in medium lowland ecosystem of Bangladesh. Journal of Agricultural Research. 2011;49:465-476
  72. 72. Sultana MR, Rahman MM, Rahman MH. Effect of row and hill spacing on the yield performance of boro rice (cv. BRRI dhan45) under aerobic system of cultivation. Journal of the Bangladesh Agricultural University. 2012;10:39-42
  73. 73. Alam MS, Baki MA, Sultana MS, Ali KJ, Islam MS. Effect of variety, spacing and number of seedlings per hill on the yield potentials of transplant aman rice. International Journal of Agronomy and Agricultural Research. 2012;2:10-15
  74. 74. Baloch AW, Soomro AM, Javed MA, Ahmed M, Bughio HR, Bughio MS, Mastoi NN. Optimum plant density for high yield in Rice (Oryza sativa L.). Asian Journal of Plant Sciences. 2002;1:25-27
  75. 75. Jacob D, Syriac EK, Pushpakumari R. Spacing and weed management in transplanted basmati rice. The Madras Agricultural Journal. 2005;92:224-229
  76. 76. Senseman SA. Herbicide handbook. 9th ed. Lawrence, US: Weed Science Society of America; 2007. p. 493
  77. 77. Al-Mamun MA, Shultana R, Bhuiyan MKA, Mridha AJ, Mazid A. Economic weed management options in winter rice. Pakistan Journal of Weed Science Research. 2011;17:323-331
  78. 78. Singh VP, Singh G, Singh RK. Integrated weed management in direct seeded spring sown rice under rain-fed low valley situation of Uttaranchal. Indian Journal of Weed Science. 2001;33:63-66
  79. 79. Marwat KB, Khan IA, Hassan G. Efficacy of different pre and post-emergence for controlling weeds in chickpea. Pakistan Journal of Weed Science Research. 2004;10:51-54
  80. 80. Gitsopoulos TK, Froud-Williams RJ. Effects of oxadiargyl on direct-seeded rice an Echinochloa crus-galli under aerobic and anaerobic conditions. Weed Research. 2004;44:329-334
  81. 81. Ahmed GJU, Mamun AA, Hossain SMA, Mridha AJ, Hossain ST. Agro-economic study of weed control in direct seeded Aus rice in the farmers’ field. Annals of Bangladesh Agriculture. 2000;8(2):111-118
  82. 82. Zhang J, Weaver SE, Hamill AS. Risks and reliability of using herbicides at below-labeled rates. Weed Tech. 2000;14:106-115
  83. 83. Talgre L, Lauringson E, Koppel M. Effect of reduced herbicide dosages on weed infestation in spring barley. Zemdirbyste-Agriculture. 2008;95:194-201
  84. 84. Barroso J, Ruiz D, Escribano C, Barrios L, Fernandez-Quintanilla C. Comparison of three chemical control strategies for Avena sterilis ssp. ludoviciana. Crop Protection. 2009;28:393-400
  85. 85. Walker SR, Medd RW, Robinson GR, Cullis BR. Improved management of Avena ludoviciana and Phalaris paradoxa with more densely sown wheat and less herbicide. Weed Research. 2002;42:257-270
  86. 86. Auskalnis A, Kadzys A. Effect of timing and dosage in herbicide application on weed biomass in spring wheat. Agronomy Research. 2006;4:133-136
  87. 87. Barros JFC, Baschand G, Carvalho M. Effect of reduced doses of a post-emergence herbicide to control grass and broadleaved weeds in no-till wheat under Mediterranean conditions. Crop Protection. 2007;26:1538-1545
  88. 88. Islam T, Bhowmic MK, Ghoshand RK, Sounda G. Effect of pretilachlor on weed control and yield of transplanted rice. Journal of Environment and Ecology. 2000;19:265-268
  89. 89. Pacanoski Z, Glatkova G. The use of herbicides for weed control in direct wet-seeded Rice (Oryza sativa L.) in rice production regions in the republic of Macedonia. Plant Production Science. 2009;45:113-118
  90. 90. Kawana Y. Control of Grass Weeds in Wet Direct-Seeded Rice. PhilRice, Muñoz, Nueva Ecija: Short-Term JICA Expert Report; 2000. pp. 32-33
  91. 91. Khaliq A, Matloob A, Shafiq HM, Cheema ZA, Wahid A. Evaluating sequential application of pre and post emergence herbicides in dry seeded fine rice. Pakistan Journal of Weed Science Research. 2011;17:111-123
  92. 92. Odero DC, Rainbolt C. Weed Management in Rice. Institute Food Agric. Sci. Univ. Florida, USA: Florida Cooperative Extension Service; 2011. pp. 1-5
  93. 93. Khaliq A, Matloob A, Mahmood S, Abbas RN, Khan MB. Seeding density and herbicide tank mixtures furnish better weed control and improve growth, yield and quality of direct seeded fine rice. International Journal of Agriculture and Biology. 2012;14:499-408
  94. 94. Saini JP, Angiras NN, Singh CM. Efficacy of cyhalofop-butyl in controlling weeds in transplanted rice (Oryza sativa). Indian Journal of Agronomy. 2001;46:222-226
  95. 95. Gnanavel I, Anbhazhagan R. Bio-efficacy of pre and post-emergence herbicides in transplanted aromatic basmati rice. Research Journal of Agricultural Science. 2010;1:315-317
  96. 96. Choubey NK, Kobe SS, Tripathi RS. Relative performance of cyhalofop butyl for weed control in direct seeded rice. Indian Journal of Weed Science. 2001;33:132-135
  97. 97. Ottis BV, Talbert RE, Malik MS, Ellis AT. Rice weed control with Penoxsulam (grasp). B.R. Wells Rice Research Studies;517:144-146
  98. 98. Rao AS, Ratnam M. Evaluation of post emergence herbicides on weed control in rice nursery. Pakistan Journal of Weed Science Research. 2010;16:387-392
  99. 99. Khaliq A, Matloob A, Ahmad N, Rasul F, Awan IU. Post emergence chemical weed control in direct seeded fine rice. Journal of Animal and Plant Science. 2012;22:1101-1106
  100. 100. Javier EF, Furuya S, Soriano R, Garcia F. Management of wet direct-seeded rice. II: Weed control by water & herbicides. Philippine Journal of Crop Science. 2005;30:11-17
  101. 101. Begum M, Juraimi A, Omar SS, Rajan A, Azmi M. Effect of herbicides for the control of Fimbristylis miliacea (L.) Vahl. In rice. Journal of Agronomy. 2008;7(3):251-257
  102. 102. Shukor JA, Mahfuza B, Yusof M, Najib M, Azmi M. Efficacy of herbicides on the control of weeds and productivity of direct seeded rice under minimal water conditions. Plant Protection Quarterly. 2010;25:19-25
  103. 103. Chauhan BS, Abugho SB. Effect of growth stage on the efficacy of postemergence herbicides on four weed species of direct-seeded rice. The Scientific World Journal. 2012;2012:1-7
  104. 104. Ranjit JD, Suwanketnikom R. Response of weeds and yield of dry direct seeded rice to tillage and weed management. Weed Science. 2005;33:63-66
  105. 105. Anwar MP, Juraimi AS, Puteh A, Man A, Rahman MM. Efficacy, phytotoxicity and economics of different herbicides in aerobic rice. Acta Agriculturae Scandinavica. 2012;62(7):1-12
  106. 106. Mann RA, Ahmad S, Hassan G, Baloch MS. Weed management in direct seeded rice crop. Pakistan Journal of Weed Science Research. 2007;13:219-226
  107. 107. Mahajan G, Chauhan BS, DE J. Weed management in aerobic rice in northwestern indo-Gangetic plains. Journal of Crop Improvement. 2009;23:366-382
  108. 108. Hussain S, Ramzan M, Akhter M, Aslam M. Weed management in direct seeded rice. Journal of Animal and Plant Science. 2008;18(2-3):86-88
  109. 109. Ashraf MM, Awan TH, Manzoor Z, Ahmad M, Safdar ME. Screening of herbicides for weed management in transplanted rice. Journal of Animal and Plant Science. 2006;16:92-95
  110. 110. Jabran K, Farooq M, Hussain M, Ehsanullah KMB, Shahid M, Lee DJ. Efficient weeds control with penoxsulam application ensures higher productivity and economic returns of direct seeded rice. International Journal of Agriculture and Biology. 2012;14:901-907
  111. 111. Zein AA, Abd-El-Baky MA, Hassan SM, Derbalah AS, Hamza AM. Evolution and mechanism of Rice weeds resistance to herbicides I-resistance of Echinochloa colonum to Bispyribac-sodium herbicide with respect to its effect on chlorophyll content. Journal of Agricultural Research. 2010;36:480-494
  112. 112. Valverde BE, Itoh K. World rice and herbicide resistance. In: Powles SB, Shaner DL, editors. Herbicide Resistance and World Grains. Boca Raton, Florida (USA): CRC Press LLC; 2001. pp. 195-249
  113. 113. El-Nady M, Hamza A, Derbalah A. Echinochloa colonum resistance to bispyribac-sodium in Egypt-occurrence and identification. Journal of Plant Protection Research. 2012;52(1):139-145
  114. 114. Rahman MM, Sahid IB, Juraimi AS. Study on resistant biotypes of Echinochloa crus-galli in Malaysia. Australian Journal of Crop Science. 2010;4:107-115
  115. 115. Délye C, Jasieniuk M, Le Corre V. Deciphering the evolution of herbicide resistance in weeds. Trends in Genetics. 2013;21:649-58
  116. 116. Fischer AJ, CMD A, Bayer E, Hill JE. Herbicide-resistant Echinochloa oryzoides and E. phyllopogon in California Oryza sativa fields. Weed Science. 2000;48:225-230
  117. 117. Osuna MD, Vidotto F, Fischer AJ, Bayer DE, Prado R, Ferrero A. Cross-resistance to bispyribac-sodium and bensulfuron-methyl in Echinochloa phyllopogon and Cyperus difformis. Pesticide Biochemistry and Physiology. 2002;73:9-17

Written By

Umair Ashraf, Saddam Hussain, Alam Sher, Muhammad Abrar, Imran Khan and Shakeel A. Anjum

Submitted: 02 March 2018 Reviewed: 18 June 2018 Published: 05 November 2018