Open access peer-reviewed chapter

# Crop Rotation Biomass and Effects on Sugarcane Yield in Brazil

By Edmilson José Ambrosano, Heitor Cantarella, Gláucia Maria Bovi Ambrosano, Eliana Aparecida Schammas, Fábio Luis Ferreira Dias, Fabrício Rossi, Paulo Cesar Ocheuze Trivelin, Takashi Muraoka, Raquel Castellucci Caruso Sachs, Rozario Azcón and Juliana Rolim Salomé Teramoto

Submitted: November 16th 2011Reviewed: September 26th 2012Published: April 30th 2013

DOI: 10.5772/53825

## 1. Introduction

Healthy soils are vital to a sustainable environment. They store carbon, produce food and timber, filter water and support wildlife and the urban and rural landscapes. They also preserve records of ecological and cultural past. However, there are increasing signs that the condition of soils has been neglected and that soil loss and damage may not be recoverable [1]. Soil is a vital and largely non-renewable resource increasingly under pressure. The importance of soil protection is recognized internationally.

In order to perform its many functions, it is necessary to maintain soil condition. However, there is evidence that soil may be increasingly threatened by a range of human activities, which may degrade it. The final phase of the degradation process is land desertification when soil loses its capacity to carry out its functions. Among the threats to soil are erosion, a decline in organic matter, local and diffuse contamination, sealing, compaction, a decline in bio-diversity and salinisation.

The authors in [2] made the interesting observation when study of nine great groups of New Zealand soils, that although many soil quality indicators will be different between soil types differing in clay and organic mater contents, land use had an overriding effect on soil quality: agricultural systems could be clearly differentiated from managed and natural forests, and grass land and arable land were also clearly separated.

Regular additions of organic matter improve soil structure, enhance water and nutrient holding capacity, protect soil from erosion and compaction, and support a healthy community of soil organisms. Practices that increase organic matter include: leaving crop residues in the field, choosing crop rotations that include high residue plants, using optimal nutrient and water management practices to grow healthy plants with large amounts of roots and residue, applying manure or compost, using low or no tillage systems, using sod-based rotations, growing perennial forage crops, mulching, and growing cover crops as green manure [3].

Addition to being a frequent addition of organic matter should be diversified. Diversity cropping systems are beneficial for several reasons. Each plant contributes a unique root structure and type of residue to the soil. A diversity of soil organisms can help control pest populations, and a diversity of cultural practices can reduce weed and disease pressures. Diversity across the landscape can be increased by using buffer strips, small fields, or contour strip cropping. Diversity over time can be increased by using long crop rotations. Changing vegetation across the landscape or over time not only increases plant diversity, but also the types of insects, microorganisms, and wildlife that live on your farm [3]. In addition a dedicated management approach is needed to maintain or increase the soil organic matter content.

The incorporation of plant materials to soils, with the objective of maintaining or improving fertility for the subsequent crop is known as green manuring. The inclusion of a legume fallow within a sugarcane cropping cycle is practiced to reduce populations of detrimental soil organisms [5, 6], provide nitrogen (N) through biological fixation [7,8] and for weed suppression [9, 10].

Interest in the use of green manure’s biomass has revived because of their role in improving soil quality and their beneficial N and non-N rotation effects [11]. Because of its nitrogen fixation potential, legumes represent an alternative for supplying nutrients, substituting or complementing mineral fertilization in cropping systems involving green manuring. This practice causes changes in soil physical, chemical and biological characteristics, bringing benefits to the subsequent crop both in small-scale cropping systems and in larger commercial areas such as those grown with sugarcane [12].

The area cropped with sugarcane (Saccharum spp.) in Brazil shows rapid expansion, with most of the increase for ethanol production. The area cultivated with sugarcane is now 9.6 Mha, with an increase of 5 Mha from 2000 and over 8.6 Mha of fresh sugarcane harvested per year [13]. Sugarcane crops in Brazil are replanted every five to ten years. In southeastern Brazil, the interval between the last sugarcane harvest and the new plantings occurs during the spring-summer season, under high temperature and heavy rainfall (almost 1,000 mm in six months) [14].

Green manure fertilization of the soil with legumes has been recommended before a sugarcane field is replanted. This practice does not imply on losing the cropping season, does not interfere with sugarcane germination, and provides increases in sugarcane and sugar yield, at least during two consecutive cuts [12]. Additionally, it protects the soil against erosion, prevents weed spreading and reduces nematode populations [15, 16]. Legumes usually accumulate large quantities of N and K, the nutrients which are taken up in the highest amounts by the sugarcane plants.

Residue incorporation studies of legumes using 15N label indicate that 10 to 34% of the legume N can be recovered in the subsequent rye or wheat crop, 42% in rice, 24% recovery from Velvet bean by corn crop, around 15% of N recovery from sunn hemp by corn plants in no-till system, 30% by maize [51],and 5% of N recovery from sunn hemp by sugarcane [12], and ranged from 19 to 21% when the recovery was observed from sunn hemp by two sugarcane harvest [17].

The authors suggested that legume residue decomposition provided long-term supply of N for the subsequent crops, by not supplying the nutrient as an immediate source.

There are many benefits to the sugarcane crop of leguminous plants rown in rotation in sugarcane renovation areas; these include the recycling of nutrients taken up from deep soil layers by the rotational crop, which may prevent or decrease leaching losses, and the addition of N from biological fixation. Leguminous plants can accumulate over 5 t ha–1 of dry mass during a short period of time during the summer and take up large amounts of N and K. Most of this N comes from the association of legumes with rhizobia. In this way crop rotation with legumes can replace partially or totally N mineral fertilization of sugarcane, at least for the first ratoon [18, 12].

Another important microbial association is that of mycorrhizal fungi and plant roots. These fungi are present in over 80% of plant species [19]. In contrast with the large diversity of plants, which includes sugarcane, that have their roots colonized by mycorrhizas, only 150 fungi species are responsible for that colonization [19]. A crop whose roots are colonized by mycorrhizal fungi can raise the soil mycorrhizal potential which can benefit plants which are responsive to this fungi association and that are cultivated in sequence. This could be particularly useful for the nutritional management of crops in low nutrient, low input–output systems of production [20].

This study evaluated biomass production, N content, characterizing the biomass and the natural colonization of arbuscular mycorrhizal fungi (AMF) of leguminous green manure and sunflower (Helianthus annuus L.) in rotation with sugarcane and their effect in the soil. Their effect on stalk and sugar yield and nematode that occur on sugarcane cv. IAC 87-3396 grown subsequently was also studied. The economic balance considered the costs of production and revenues of the rotational crops as well as three or five harvests of sugarcane was too evaluated.

## 2. Development:

Three long term assays were developed during December 4, 1999 to October 10, 2005 to complete this study as following:

The experiments were carried out in Piracicaba, state of São Paulo, Brazil (22o42’ S, 47o38’ W, and 560 m a.s.l). The soil, classified as an Arenic Hapludult, and a Typic Paleudult, was chemically characterized at different depths after cutting the green manure crop, before the sugarcane first planting. The soil was acidic and had low amounts of nutrients (Table 1), typical of many sugarcane growing areas.

Total monthly rainfall and local temperature were measured at the meteorological station near the experimental site (Figure 1).

 Soil characteristics* Arenic Hapludult Typic Paleudult 0.0-0.2 0.2-0.4 0.0-0.2 0.2-0.4 Soil depth, m pH (0.01mol l-1) 4.1 4.0 5.5 5.5 O.M. (g dm–3) 26 22 20 19 P (mg dm-3) 3 14 13 10 K (mmolc dm-3) 0.7 0.5 0.6 0.4 Ca (mmolc dm-3) 7 6 33 29 Mg (mmolc dm-3) 6 5 21 19 H + Al (mmolc dm-3) 50 68 23 25 CEC (mmolc dm-3) 64 80 79 74 V % 22 14 68 64

### Table 1.

Soil chemical characteristics before sugarcane planting, in plots without green manure, at depths of 0.0-0.2 and 0.2-0.4 m.

### 2.1. Effect of seven rotational crops in sugarcane yield:

The experiment 1 consisted to evaluate seven rotational crops plus control (fallow) grown before sugarcane was planted.

The soil is as a Typic Paleudult and was chemically characterized at different depths with samples taken after the green manures were cut but before sugarcane was planted (Table 1). The experimental design was a randomized block with eight treatments and five replications.

The rotational crops were peanut (Arachis hypogaea L.) cv. IAC-Tatu, peanut cv. IAC-Caiapo, sunn hemp cv. IAC-1 (Crotalaria juncea L.), velvet bean (Mucuna aterrima Piper and Tracy), soybean (Glycine max L. Merrill) cv. IAC-17, sunflower (Helianthus annuus L.) cv. IAC-Uruguai, and mung bean (Vigna radiata L. Wilczek).

The green manures were sowed always in December on 7 m × 10 m size plots, with rows 0.50 m apart. The experimental area was weeded 30 d after sowing, and the weed residues were left on the soil surface.

During seed filling, the plants used as green manure were manually cut and spread on the soil covering the entire plot surface in pieces less than 0.25 m and left there for six months. Peanut, soybean, sunflower and mung bean were harvested after physiological maturation for the grain yield, and the remaining plant parts were cut and spread on the soil. Biomass production of the rotational crops was evaluated in 1 m2 of the plot area.

At the harvest stage, the roots of each rotational crop were sampled in order to evaluate the natural colonization level of arbuscular mycorrhizal fungi (AMF). The colonization percentage was estimated using the root coloration technique according to [21]. The percentage of colonization by AMF was estimated by counting the roots’ stained portions using a reticular plate under a microscope following the procedures described by [22].

To evaluate sugarcane stalk yield 2-m sections of each of the three central rows were cut and weighed.

Ten successive stems were separated from each plot for the technological evaluation of the Brix, pol, and total recovered sugar [23]. Sugar yield, expressed in terms of tons of pol per hectare (TPH), was estimated with the stem yield and technological analysis data.

### Table 8.

Economic balance1 of sugarcane production including revenues and costs of crop rotation.

## 4. To evaluated the recovery of nitrogen by sugarcane when applied green manure crop and mineral N

To evaluate the utilization of nitrogen by sugarcane (Saccharum spp.) fertilized with sunn hemp (SH) (Crotalaria juncea L.) and ammonium sulfate (AS):

The presence of a green manure crop and mineral N applied together caused some soil alterations that could be detected in samples collected in the sugarcane planting and harvesting seasons (Table 9). There was an increase in calcium and magnesium availability, and consequently in base saturation and pH, in relation to the AS-15N treatment, at planting. Similar results were obtained by [38], who worked with four velvet bean cultivars, velvet bean, Georgia velvet bean, cow itch, and cratylia. The presence of green manure caused a significant sum of bases increase, due to increases in calcium and magnesium; consequently, treatments involving velvet bean showed higher CEC values. The presence of organic acids in the plant mass could be the reason for this change.

During sugarcane harvest, increases in Mg concentration, pH, and base saturation (V%) were observed in the treatments containing SH-15N+ AS in relation to the treatment containing AS-15N alone. Also, a significant reduction in potential acidity was observed in treatments containing SH-15N+ AS in relation to the treatment containing AS-15N alone (Table 9).

 Soil sampling at sugarcane planting Treatment pH (CaCl2) Ca Mg H+Al SB V 0.01mol l-1 ------------------mmolc dm-3------------------- ----- % ----- Control 5.1 ab 20.5 ab 14.5 ab 37.8 a 35.4 ab 48.2 a AS-15N2 4.7 b 15.8 b 9.8 b 47.0 a 25.9 b 36.0 a SH + AS -15N 5.3 a 24.8 a 17.8 a 32.0 a 42.8 a 55.8 a SH-15N 5.0 ab 18.0 ab 13.0 ab 39.0 a 31.4 ab 44.5 a Mean 5.0 19.8 13.8 39.0 33.9 46.1 C.V.% 5.12 7.55 10.76 20.77 6.81 22.52 Soil sampling at sugarcane harvest Control 5.0 ab 17.8 a 14.0 ab 39.8 ab 32.2 a 44.5 ab AS-15N 4.7 b 15.3 a 9.8 b 46.5 a 25.4 a 35.8 b SH + AS -15N 5.6 a 24.7 a 26.8 a 25.5 b 44.4 a 67.5 a SH-15N 5.0 ab 19.0 a 15.3 ab 36.3 ab 34.5 a 48.5 ab Mean 5.0 18.0 16.4 37.0 33.5 49.1 C.V.% 8.00 30.88 15.18 25.87 32.45 29.57

### Table 9.

Chemical characterization of the soil (0.0-0.2 m depth) in the sugarcane planting and harvesting seasons.

The presence of organic acids in decomposing plant residues can help Mg movement in the soil [39]. Crops with high C:N ratio may release N more slowly and cause an increase in N uptake by succeeding crop In addition, rotational plants that were grown before sugarcane could recycle nutrients that would otherwise be leached contribute with N derived from BNF and keep some elements in plant available forms, which could be transformed into more recalcitrant forms if the soil lie fallow for some time.

There was no variation in nutrient contents for macronutrients N and P, and for micronutrients B and Zn in sugarcane stalks at harvest time (Table 10). However, there were differences in Ca and K contents; the latter showed higher values in treatments involving fertilizer application, either mineral or organic, while Ca showed a higher value in the treatment with green manure and mineral N, indicating better nutrition with this element in the treatment containing higher nitrogen supply.

Nitrogen and potassium absorption is greatly influenced by moisture; this relation has been known for a long time [40], and the fact that treatments involving green manure crops maintained environments with higher moisture due to soil mulching with plant mass could have favored better potassium nutrition. With regard to calcium, nitrogen seems to favor absorption [41].

 Treatment N K P Ca Zn B Contents determined in sugarcane stalks at harvest ---------------g kg-1---------------- --mg kg-1-- Control 7.2 a 3.3 b 0.8 a 1.6 b 10.9 a 12.1 a AS-15N2 8.1 a 6.7 a 0.9 a 1.7 b 15.3 a 14.9 a SH-15N 7.7 a 7.1 a 0.9 a 1.8 b 13.3 a 14.8 a SH + AS -15N 8.8 a 8.5 a 1.0 a 2.4 a 13.7 a 15.4 a Mean 8.0 6.4 0.9 1.88 13.3 14.3 C.V.% 11.52 27.89 15.61 8.14 19.80 18.00

### Table 10.

N, K, P, Ca, Zn, and B contents in sugarcane stalks at harvest time.

When sugarcane was cultivated for five years and was harvested three times. 15N recovery was evaluated in the two first harvests. In the sum of the three harvests, the highest stalk yields were obtained with a combination of green manure and inorganic N fertilizer; however, in the second cutting the yields were higher where sunn hemp (SH) was used than in plots with ammonium sulfate (AS) (Table 11).

Millable stalk yields of the first cycle (plant cane, harvested 18 months after planting) were higher than those of the second and the third cycle (Table 11). The yield decline with time is common, especially in the cases such as the present experiment when only the first cycle crop was fertilized in order to evaluate the residual effect of N application in the mineral or green manure forms. In the first year the stalk yield was numerically higher in plots fertilized with a combination of green manure and AS; however, in the second year the plots that received SH produced more cane than those fertilized only with AS or the control treatment, indicating that the green manure applied before planting still affected plant growth and yield after 34 months. In the third cycle, there were no differences among the treatments, showing that the residual effect of both N sources had disappeared (Table 11). In the sum of three cuttings, the combination of AS and green manure resulted in highest yields.

 Treatments2 Harvests Total of three cuttings Mean ± SEM3 24 Aug 2002 08 Oct 2003 20 Sep 2004 --------------------------- Stalk yield, Mg ha-1 --------------------------- Control 86.0 Ba 61.1 Bab 47.1 Ab b194.2 64.7 ± 4.6 AS15N 106.2 ABa 64.7 Bb 42.3 Ab ab213.2 71.1 ± 4.6 SH + AS15N 128.7 Aa 84.5Ab 45.0 Ac a258.2 86.1 ± 4.6 SH15N 92.4 ABa 83.8 Aa 41.2 Ab ab217.3 72.4 ± 4.6 Mean ± SEM 103.3 ± 3.8 a 73.5 ± 3.8 b 43.9 ± 3.8 c 215.4 ± 18.9 -------------------------POL, Mg ha-1 ------------------------------ Control 11.9 10.4 17.9 b40.2 13.5 ± 0.7 B AS15N 14.9 11.1 17.5 ab43.5 14.5 ± 0.6 AB SH + AS15N 17.0 14.1 18.4 a49.5 16.5 ± 0.6 A SH15N 12.9 14.2 18.1 ab45.2 15.1 ± 0.6 AB Mean ± SEM 14.2 ± 0.9 b 12.4 ± 0.9 b 18.0 ± 0.9 a 43.8 ± 2.4

### Table 11.

Millable stalk yield and POL1 of sugarcane plants in three consecutive harvests as a function of N applied at planting as ammonium sulfate (AS) or Sunn hemp (SH) green manure1

[36] showed evidence of the positive effect of green manure fertilization with sunn hemp in sugarcane, with greater sugarcane yield increase than with the application of 40 kg ha-1 mineral N to the soil. [43], studying lupine in maize, and [44], studying velvet bean and sunn hemp in rice, could not find response to mineral N applied after green manure, and no N fertilizer was needed when vetch (Vicia spp.) was grown after wheat, and when cotton followed faba beans [42].

The effect of fertilizer source on sugar concentration was less evident. In the average of three cuttings, the value of pol in plots, treated with both AS + SH was higher than in that observed in plots that received no N (Table 11). Pol in cane juice was higher in the third cutting than in the two previous ones. Variations in pol measurements among cropping seasons are usually more affected by environmental conditions (temperature and drought) that determine cane maturation than by nutrition. However, high N tends to decrease sugar content and delay maturation [45]; therefore, after two years with no N fertilization, sugar content in cane plants was more likely to be high.

The recovery of N by the first two consecutive harvests accounted for 19 to 21% of the N applied as leguminous green manure and 46 to 49% of the N applied as AS.

Nitrogen derived from AS and SH in the leaves and top parts of the sugarcane plant, excluding the stalks, varied from 6.9 to 12.3 % of the total N at the end of the first cycle (plant cane) and was not affected by N source (Table 12). But the amounts of N from both sources accumulated in the leaves and tops were in the range of only 4.5 to 6.0 kg ha-1, which represent a recovery of 6.4 to 8.1% of the N applied as AS and 2.7 and 3.1% of the N from the green manure (Table 12). The recovery of 15N in the second cycle decreased when the N source was the inorganic fertilizer. In the second year the percentage of N derived from sunn hemp was greater than that from the AS, indicating a slightly higher residual effect of the green manure (Table 12).

 Samplingdates Treatments2 Mean ± SEM3 AS15N SH-15N + AS SH15N AS15N+ SH ----------------------------- Ndff ,% ------------------------- 24 Aug 2002 12.3 Aa 11.1 Aa 10.9 Aa 6.9 Aa 10.3 ± 1.1 08 Oct 2003 1.7 Bb 5.5 Aa 4.1 Aab 1.7 Bb 3.2 ± 1.1 Mean ± SEM 7.0 ± 1.6 8.3 ± 1.6 7.5 ± 1.6 4.3 ± 1.6 ---------------------------- QNdff, kg ha-1 ----------------------- 24 Aug 2002 5.7 6.0 5.2 4.5 5.4 ± 0.6 A 08 Oct 2003 1.8 6.8 4.6 2.9 4.0 ± 0.6 A Mean ± SEM 3.7 ± 1.0 a 6.4 ± 1.0 a 4.9 ± 1.0 a 3.7 ± 1.0 a --------------------------------- R, % ------------------------------- 24 Aug 2002 8.1 Aa 3.1 Aa 2.7 Aa 6.4 Aa 5.1 ± 0.6 08 Oct 2003 2.6 Ba 3.5 Aa 2.3 Aa 4.1 Aa 3.1 ± 0.6 Mean ± SEM 5.3 ± 0.9 3.3 ± 0.9 2.5 ± 0.9 5.3 ± 0.9

### Table 12.

Percentage (Ndff) and quantity (QNdff) of nitrogen in leaves derived from the labeled fertilizer source and nitrogen recovery (R) in samples taken in the first and second harvests1.

The percentage of N derived from the AS or SH accumulated in the stalks harvested in the first cycle were similar and ranged from 7.0 to 10.5% of the total N content. In the plant cane cycle the amounts of N in the stalks that had been applied as inorganic or organic fertilizers were higher than those measured in the leaves and tops and varied from 27.3 to 24.1 kg N ha-1 (Table 13). The recovery of N derived from inorganic fertilizer - 30.1 to 34.4% - was higher than that of the sunn hemp - 8.8 to 9.8%. However, in the second harvest the N the green manure supplied more N to the cane stalk than AS (Table 13). The difference in the amounts of N in the sugarcane plants derived from green manure and mineral fertilizer in the ratoon crop was around 1to 2 kg ha-1 N in leaves and tops (Table 12) and 4 to 7 kg N ha-1 in the stalks (Table 13), which were relatively small compared to the amounts of N accumulated in the ratoon plants (179 kg N ha-1 in plants supplied with AS and 243 kg ha-1 N in the SH treatments, or a 64 kg N ha-1difference - Table 13). These results suggest that the effect of green manure on the yield of the second ratoon crop (Table 11) may not be only due to the extra N supply, but rather to other beneficial role of green manure on soil physical-chemical or biological activity properties.

Adding up the amounts of N taken up by the sugarcane plant and contained in the above-ground parts of the plant (leaves, tops and stalks), AS supplied 32.4 to 34.2 kg N ha-1or about 46 to 49% of N recovery; the N taken up by sugarcane from sunn hemp varied from 37.4 to 40.0 kg ha-1, which represented 19.1 to 20.8% N recovery (Tables 12 and 13).

The recovery of N from fertilizers by sugarcane is usually lower than that of grain crops: the latter varies from 50 to 70% [46] whereas for sugarcane the figures vary from 20 to 40% [47- 49, 25]. Results of several studies show that the utilization of N from green manure by subsequent crops rarely exceeds 20% [43, 50, 12, 51] and most of the N remains in the soil, incorporated in the organic matter fraction. In the present study the application of AS along with SH increased N utilization by sugarcane plants. This result is in line with that of [44] who used an organic source isolated or combined with an inorganic fertilizer in rice crops and concluded that the green manures improved the mineral N utilization, resulting in N use efficiency of up to 79%.

In a study in pots [51] observed that maize plants took up more N from sunn hemp incorporated to a sandy soil (Paleudalf) than to a clayey soils (Eutrudox) and that the N derived from the roots was more recalcitrant than that of the shoots. Between 50 and 68% of the 15N of the sunn hemp shoots remained in the soil whereas the figures for roots varied from 65 to 80%. Unaccounted for 15N, probably lost in gaseous forms, varied from 5 to 15% of the sunn hemp N [51].

In a detailed account of the first year of the present experiment, [12] showed that 8 months after planting, the recovery by sugarcane plants (above ground parts) of the N derived from AS or from sunn hemp was similar: 3 to 6% of the added N. However, 12 and 15-month-old sugarcane plants recovered between 20 and 35% of the AS but only 6 to 8% of the sunn hemp-derived N.

The percentage of recovery of the inorganic fertilizer N contained in the stalk when the sugarcane plants were harvested after 18 months of planting varied from 30 to 34%; the corresponding figures for the N derived from sunn hemp were significantly lower: around 9 to 10% (Table 13). The residual effect of the N from both sources in the second harvest of the sugarcane plant was similar: between 4 and 6% of the N supplied at planting as AS or SH was recovered in the stalks of the sugarcane plant 31 months after planting (Table 12).

 Sampling dates Treatments2 Mean ± SEM3 AS15N SH 15N + AS SH15N AS15N + SH ------------------------------ Ndff, % ------------------------- 24 Aug 2002 10.5 Aa 7.0 Aa 8.2 Aa 10.3 Aa 9.0 ± 1.2 08 Oct 2003 1.4 Bb 3.8 Aa 3.7 Aa 1.7 Bb 2.6 ± 0.1 Mean ± SEM 6.0 ± 1.2 5.4 ± 1.2 5.9 ± 1.2 6.0 ± 1.2 ---------------------------- QNdff, kg ha-1 ----------------------- 24 Aug 2002 24.1 Aa 19.3 Aa 17.3 Aa 21.1 Aa 20.4 ± 2.78 08 Oct 2003 2.7 Bb 8.6 Aa 10.3 Aa 3.9 Bb 6.4 ± 0.8 Média ± SEM 13.4 ± 2.6 14.0 ± 2.6 13.8 ± 2.6 12.5 ± 2.6 ---------------------------------- R, % ------------------------------- 24 Aug 2002 34.4 Aa 9.9 Abc 8.8 Ac 30.1 Aab 20.8 ± 1.9 08 Oct 2003 3.9 Ba 4.4 Aa 5.3 Aa 5.6 Ba 4.8 ± 1.9 Mean ± SEM 19.1 ± 3.2 7.1 ± 3.2 7.0 ± 3.2 17.8 ± 3.2 -------------------- Cumulative N kg ha-1------------------------ 24 Aug 2002 177.4 235.6 257.0 220.4 222.6 ± 9.2 A 08 Oct 2003 181.0 190.8 228.0 270.8 217.6 ± 9.2 A Mean ± SEM 179.2 ± 12.0 a 213.2 ± 12.0 a 139.9 ± 12.0 a 245.6 ± 12.0 a

### Table 13.

Percentage (Ndff) and quantity (QNdff) of nitrogen derived from the labeled fertilizer source, nitrogen recovery (R) in sugarcane stalks and nitrogen accumulated in samplings carried out in the first and second harvestings1.

In the present study, about 69% of the N present in the sunn hemp residues were from BNF. The data obtained in the present study are also in agreement with those obtained by [18] for green manure produced in the field, in the inter-rows of the ratoon crop.

Perin [32] found substantial amounts of N derived from BNF present in the above ground parts of sunn hemp (57.0%) grown isolated and 61.1% when intercropped with millet (Pennisetum glaucum, (L.) R. Brown) (50% seeded with each crop). The sunn hemp+millet treatment grown before a maize crop resulted in higher grain yield than when sunn hemp alone was the preceding rotation. This effect was not observed when N-fertilizer (90 kg N ha–1) was added; Perin [32] concluded that intercropping legume and cereals is a promising biological strategy to increase and keep N into production system under tropical conditions.

No difference was observed in relation to the cumulative N listed in Table 10. The cumulative N results are similar to those found by [47], who obtained, during plant cane harvesting, mean values of 252.3 kg ha-1 cumulative nitrogen, with high nitrogen and plant material accumulation during the last three months, as also observed by [49]. The nitrogen contents found in the above-ground part of sugarcane, Table 10, are in agreement with results of [47].

As the amounts of N applied as AS or SH to sugarcane in the first cycle were different (70 kg N ha-1as AS and 196 kg N ha-1 as SH), the quantities of N derived from the green manure in the second harvest were larger than those from the inorganic fertilizer, although the percentage of N recovery was similar (Table 12).

Because less N derived from the green manure was recovered by the sugarcane plant in the first cycle it would be expected that a higher proportion of that N would be taken up in the second cycle (first ratoon), but this did not happen. It seems that the residual N that is incorporated to the soil organic matter has a somewhat long turnover. Other authors have reported low recovery (about 3.5% of the N) by the second crop after sunn hemp cover crop [52] or hairy vetch (Vicia villosa Roth) plowed into the soil [53]. Low recovery of residual N has also been observed for inorganic fertilizer sources: less than 3% of the N derived from fertilizers was taken up by soybeans (Glicine max (L) Merril) [54], maize (Zea Mays L.) [52], [53] or sugarcane (Saccharum spp) [55], results similar to those obtained in the present study (Table 12 and 13).

The amounts of inorganic N, derived from both N sources, present in the 0-0.4 m layer of soil in the first season after N application and were below 1 kg ha–1.

The average concentration of inorganic nitrogen in the 0-40 cm layer of soil was relatively low in most samples taken after 8, 12, 15, and 18 months of planting (Table 14). Samples taken in February, in the middle of the rainy and hot season, presented somewhat higher values of (NH4+ + NO3-)-N probably reflecting higher mineralization of soil organic N (Figure 2). Later in the growing season (samples of May and Aug 2002) soil inorganic N content decreased again. This coincides with beginning of the dry season with mild temperatures, when the sugarcane plant reached maturity and probably had already depleted the soil for most of the available N.

 Treatments1 Sampling dates 29 Oct 2001 20 Feb 2002 28 May 2002 24 Aug 2002 Mean ± SEM2 -----------------------------------------mg kg-1--------------------------------------- Control 2.7 Ab 7.3 ABa 2.3 Ab 2.8 Ab 3.8 ± 0.22 AS15N 2.6 Ab 9.1 Aa 2.2 Ab 3.2 Ab 4.3 ± 0.22 SH15N + AS 2.9 Ab 7.0 ABa 2.7 Ab 3.1 Ab 3.9 ± 0.22 SH15N 2.8 Ab 5.8 Ba 1.5 Bc 2.8 Ab 3.2 ± 0.22 SH + AS15N 2.7 Ab 7.2 ABa 3.1 Ab 2.6 Ab 3.9 ± 0.22 Mean ± SEM 2.7 ± 0.19 7.3 ± 0.19 2.4 ± 0.19 2.9 ± 0.19

### Table 14.

Soil mineral N (NH4+ + NO3-) determined in four sampling dates during the plant cane cycle. Data are average of samplings of the 0-0.2 and 0.2-0.4 m soil layers.

The percentage of the inorganic N derived from AS or SH present in the soil from the 8th to the 18th month after sugarcane planting represented only 1 to 9% of total inorganic N (Table 15). The proportion of N that was originated from AS decreased with time whereas that from the green manure increased, indicating that the mineralization of this organic source could supply more N at the end of the season (Table 15). Indeed, [12] showed that sugarcane stalks sampled in 15-month old plants had significantly higher percentage of N derived from AS than from SH; in the 18th month that difference had disappeared. Nonetheless, throughout the season, the amounts of inorganic N in the soil derived from either AS or SH were of very little significance for the nutrition of the sugarcane plant – less than 1 kg ha-1 of inorganic N in a 40 cm soil layer (Table 15), indicating that little residual N is expected in soils grown with this crop. Although the rate of N applied as SH was almost 200 kg N ha-1, little nitrate leaching losses are expected under the conditions of this experiment.

 Treatments1 Sampling dates 29 Oct 2001 20 Feb 2002 28 May 2002 24 Aug 2002 Mean ± SEM2 ------------------------------ Ndff, % ----------------------------------- AS15N 5.9 Aa 0.7 Aa 3.2 Aa 1.0 Ba 2.7 ± 0.57 SH15N + AS 2.6 Ab 3.2 Aab 9.0 Aa 5.7 ABab 5.1 ± 0.62 SH15N 2.9 Aa 4.3 Aa 7.0 Aa 5.9 Aa 5.0 ± 0.58 SH + AS15N 2.9 Aa 0.3 Aa 4.0 Aa 1.3 ABa 2.1 ± 0.62 Mean ± SEM 3.6 ± 0.58 2.1 ± 0.56 5.8 ± 056 3.5 ± 0.55 --------------QNdff, kg ha-1 -------------------------- AS15N 0.3 Aa 0.3 Aa 0.4 Aa 0.5 Aa 0.40 ± 0.16 SH15N + AS 0.1 Aa 0.2 Aa 0.2 Aa 0.2 Aa 0.18 ± 0.18 SH15N 0.1 Aa 0.2 Aa 0.1 Aa 0.2 Aa 0.15 ± 0.16 SH + AS15N 0.1 Aa 0.1 Aa 0.1 Aa 0.0 Aa 0.07 ± 0.16 Mean ± SEM 0.15 ± 0.09 0.21 ± 0.09 0.24 ± 0.09 0.22 ± 0.09

### Table 15.

Percent (Ndff) and amount (QNdff) of soil mineral N (NH4+ + NO3-) derived from the labeled fertilizer source (Ndff). Data are average of samplings of the 0-0.2 and 0.2-0.4 m soil layers.

Soil N is often the most limiting element for plant growth and quality. Therefore, green manure may be useful for increasing soil fertility and crop production. With regard to fertilization, organic matter such as a green manure can be potentially important sources of N for crop production [56].

Sugarcane is a fast growing plant that produces high amounts of dry matter. Therefore, it tends to rapidly deplete the soil of inorganic N, especially in soils fertilized with small rates of soluble N as in the case of this study. Cantarella [25] reviewed several Brazilian studies showing little nitrate leaching losses in sugarcane. More recently, [57] showed that only 0.2 kg ha-1 NO3--N derived from 120 kg ha-1 of N as urea enriched to 5.04 15N At% applied to the planting furrow leached below 0.9 m in a sugarcane field, although the total N loss reached 18 kg ha-1 N, mostly derived from soil organic matter mineralization or residual N already present in the soil. As in the present study, the data of [57] refer to N applied at the end of the rainy season when excess water percolating through the soil profile is limited (Figure 2).

## 5. To evaluate the effect of biomass on the occurrence of nematodes (Pratylenchus spp.) and sugarcane yield after five cuts

The legume most productive was sunn hemp crotalaria juncea IAC-1 with 10,264 kg ha-1, followed by velvet-bean with 4,391 kg ha-1 and peanuts IAC-Caiapó and IAC-Tatu with 3,177 kg ha-1 and 1,965 kg ha-1, respectively.

There was an increase of Stalk yield of sugarcane in the average of the five cuts, compared to control treatment (Table 16). It can be seen that the effect of planting green manure in the fields of sugarcane promoted reform of benefits in terms of increased productivity of sugarcane, and this is lasting reaching in this case until the fifth cut, and the only treatment that stood out was the rotation of the witness with sunn hemp. Notably, the sunn hemp had higher dry matter production, and this may be a positive influence on growth of sugarcane. After five harvests, sunn hemp crotalaria was the leguminous crop that induced the greatest sugarcane yield, with 30% increase in cane yield and 35% in sugar yield.

 Rotational crop Harvests 25 Oct 2001 9 Sep 2002 1Aug 2003 7Nov 2004 6 Oct 2005 Mean --------------------------- Stalk yield, Mg ha-1 ---------------------------- Sunn hemp IAC 1 145.36 122.30 79.70 51.86 39.30 87.70 A Velvet bean 141.2 121.88 75.72 51.78 28.12 85.56 AB Peanut cv. IAC-Tatu 149.92 108.79 74.58 52.16 29.64 83.02 AB Peanut cv. IAC-Caiapó 122.74 122.30 67.42 49.44 36.78 79.74 AB Control 129.90 85.31 55.38 46.40 36.15 67.51 B Mean 138.39 a 113.23 b 71.00 c 50.43 d 34.16 e

### Table 16.

Millable stalk yield of sugarcane plants in five consecutive harvests as a function of treatments.

Crop rotation with non-host species of nematodes, when well planned, can be an efficient method for integrated control of nematodes. It is common in some areas, the practice of cultivation of Fabaceae in the period between the destruction of ratoon sugarcane field and planting the new. There are several plants used in systems of crop rotation with sugarcane, the most common are crotalarias, velvet beans, soybeans and peanuts. However, depending on nematode species occurring in the area, some of these cultures may significantly increase the population of these parasites. Thus, the sugarcane crop, can be greatly impaired by increasing the inoculum potential of the nematodes [58, 59].

The peanut IAC-Caiapó and velvet bean were the leguminous crops that resulted in the greater percentage of AM fungus. The lowest population of Pratylenchus spp. was found in the treatments with peanut IAC-Tatu and IAC-Caiapó (Figure 3).

Thet peanut IAC-Caiapó showed a minimum of 10 nematodes per 10 g of roots and a maximum of 470, while on the control this variation was from 80 to 2,510, indicating the smaller presence of the nematode in treatments with peanut IAC-Caiapó (Figure 3).

## 6. Conclusions

Crop rotation can positively affect yield and increase profit, contributed to raise the net income. This was true both for the green manures (sunn hemp and velvet bean), as for the grain crops (soybean, sunflower and mung bean). Peanuts caused an increase in the sugarcane stalk yields relative to the control, especially in the first harvest, but the high cost of production of this grain somewhat cancelled out the benefit of this rotation.

However, in many sugarcane regions in São Paulo State (Brazil) peanuts are extensively grown in rotation with sugarcane, probably because in those sites yields are higher and the cost of production, lower. Mung beans are a niche crop. Although it provided a relatively high net return in the present study, the risks may be high due to the market restrictions and price fluctuations.

The biomass of green manure induced a complete N substitution in sugarcane and can cause positively affect yield and increase Ca and Mg contents, sum of bases, pH, and base saturation, and decreasing potential acidity and increase profit.

The combination of inorganic fertilizer and green manure resulted in higher sugarcane yields than either N source separately. The recovery of N from ammonium sulfate was higher in the first year whereas in the green manure presented a longer residual effect and resulted in higher yields of cane in the second cycle. The recovery of 15N- labeled fertilizers by two successive sugarcane crops summed up 19 to 21% of the N applied as sunn hemp and 46 to 49% of the N applied as ammonium sulfate. Very little inorganic N was present in the 0-40 cm soil layer with both N sources.

The sugar content of sugarcane stalks is important because the raw material remuneration takes into account this parameter in Brazil. Some crops that preceded sugarcane had a high effect on sugar yield; this was observed mainly in the first harvest in areas where sunflower, peanuts, velvet beans and sunn hemp were previously cultivated. The 3-year average data showed a sugar yield increase, in the best treatment, of 3 t ha–1 in relation to the control.

The peanut IAC-Caiapó, sunflower and velvet bean were the leguminous crops that resulted in the greater percentage of AM fungus. The lowest population of Pratylenchus spp. was found in the treatments with peanut IAC-Tatu and IAC-Caiapó.

After five harvests, sunn hemp crotalaria was the leguminous crop that induced the greatest sugarcane yield, with 30% increase in cane yield and 35% in sugar yield.

### Acknowledgement

To the technical research support of Gilberto Farias, Benedito Mota, and Maria Aparecida C. de Godoy. To FAPESP and CNPq for the grants. Piraí seeds for green manure and cover crops for the support.

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Edmilson José Ambrosano, Heitor Cantarella, Gláucia Maria Bovi Ambrosano, Eliana Aparecida Schammas, Fábio Luis Ferreira Dias, Fabrício Rossi, Paulo Cesar Ocheuze Trivelin, Takashi Muraoka, Raquel Castellucci Caruso Sachs, Rozario Azcón and Juliana Rolim Salomé Teramoto (April 30th 2013). Crop Rotation Biomass and Effects on Sugarcane Yield in Brazil, Biomass Now - Cultivation and Utilization, Miodrag Darko Matovic, IntechOpen, DOI: 10.5772/53825. Available from:

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