Nutrient Supplying Potential of Crop Residues in Indian Agriculture

Abstract

The Indian agriculture sector has seen tremendous changes over the period. The country’s food grain production has increased from just 50 million tons (mt) in the 1950s to 308 mt at present, around a sixfold rise. All of this could become possible due to the introduction of green revolution technologies in the 1970s and onwards, such as the introduction of high-yielding varieties, chemical fertilizers, pesticides, selective herbicides, and improvement of irrigation facilities with improved agronomic management. According to an estimate, chemical fertilizers alone account for 50% of growth in the country’s foodgrain production. In the early 1950s, total fertilizer consumption in India was just 0.069 mt, which has increased to 2.25 mt in 1970–71 and 32.5 mt at present. This about 14.4 times rise in fertilizer consumption since the 1970s level to the present highlights the role of fertilizers and nutrient management in Indian agriculture. However, a continuous increase in fertilizer consumption over the year has invited many secondary agricultural problems, such as multi-nutrient deficiency, increased cost of production, and declining factor productivity of fertilizers. Imbalance and overuse use of fertilizers, along with increased cropping intensity and reduced recycling of residues are some of the reasons for such problems. Increased agricultural production also generates a large volume of surplus residue, which often creates problems for farmers. It is well-understood facts from various research studies that crop residues are the hidden treasurer of all the essential nutrients and organic carbon. This chapter highlights the potential of crop residue in nutrient recycling in India and the availability of surplus crop residue.

1. Introduction

The agriculture sector alone engages about 55% of the Indian population and is the backbone of the Indian economy. India’s foodgrain production has significantly increased from 50 mt in the 1950s to 308.6 mt in 2020, making it the world’s second-largest producer [1]. Green revolution technologies (GRTs) and modern infrastructure helped the country achieve self-sufficiency by implementing a variety of modern methods and technologies, including the use of high-yielding varieties, chemical fertilizers, irrigation facilities, pesticides, and farm machinery, all backed by increased public investment and facilitating institutions [2]. The adoption of high-yielding varieties of rice and wheat coupled with chemical fertilizers and agronomic management were critical factors in achieving foodgrain self-sufficiency. Better nutrient management through fertilizers alone accounts for a 50% rise in food grain production in the country [3]. Consumption of fertilizers increased to 32.5 million tons in 2020–21, scaled up from 0.069 mt in 1950–51 and 2.25 mt in 1970–71. India's total NPK consumption increased 471 times to its 1950–1951 level, and 14.44 times to the 1970–1971 level [1, 2, 3, 4]. Increased use of chemical fertilizer and intensive agriculture create secondary agricultural problems. More than half of Indian soils are deficient in NPK, indicating a multi-nutrient deficiency. According to a recently published report based on soil samples collected between 2011–2017, about 36.5, 23.4, 12.8, 7.1, and 4.2% of soils were found deficient in Zn, B, Fe, Mn, and Cu, respectively [5, 6]. Multi-nutrient deficiency is of prime concern to Indian agriculture, mostly caused by the over and imbalance usage of primary major nutrients, particularly nitrogen, as well as a lack of attention to secondary and micronutrients, and increased intensive cropping without returning crop biomass. Approximately 188.4 thousand tons (Tt) of micronutrients were removed by 263 mt of foodgrains produced [7]. Based on annual crop production data from 2011–12 to 2015–16, India is producing 696.38 million tons of gross crop residue annually [8]. This hulk size of crop residue warrants judicious management in agriculture, which would aid in the elimination of multi-nutrient deficiency, as well as reduced fertilizers costs and improved soil health. This chapter will touch on the issues of nutrient deficiency in Indian soils and the potential of nutrient recycling from agricultural crop waste.

2. Status of nutrient deficiency in Indian soils

Indian soils are largely poor in fertility status, especially in nitrogen, phosphorus, and potassium, which is compounded by the emergence of micronutrient deficiencies, as a result of their accelerated removal under intensive agriculture. Multi-nutrient deficiency has now become a severe problem in Indian soils; nearly all of the 17 essential plant nutrients are deficient in Indian soils to variable degrees. Multi-nutrient deficiency is exaggerated with modern highly intensive agriculture, which lacks in providing micronutrients back to the soil. According to the latest data from the DAC’s soil health dashboard (available at https:/soilhealth .dac.gov.in /NewHome Page/StateWiseNPKChart), 96% of Indian soils have extremely low, and or medium nitrogen content, with only 4% having a high nitrogen content (Figure 1).

Figure 1.

Primary nutrient deficiencies (%) in Indian soils. (Source: https://www.soilhealth.dac.gov.in/NewHomePage/StateWiseNPKChart).

About 61% of Indian soils are deficient in available phosphorus. Similarly, about 5, 10, and 47% of soils are very low, and medium in plant-available potassium, respectively.

In a recent report from Shukla et al., [5], a detailed description of secondary (sulfur) and micronutrient deficiencies in Indian soils are given in Figures 2 and 3.

Figure 2.

Percentage of Indian soils deficient in S and micronutrients (adopted from [5]).

Figure 3.

State-wise percent distribution of micronutrient deficiencies in India (source: [5]).

About, 40.5, 36.5, 12.8, 4.2, 7.1, and 23.2% of soils in 536 districts in India are found to be deficient in sulfur (S), zinc (Zn), iron (Fe), copper (Cu), manganese (Mn), and boron (B), respectively [5]. In Indian soils, zinc was reported to be the most deficient micronutrient. The prevalence of zinc deficiency varies by state, ranging from 9.6% in Uttarakhand to 75.3% in Rajasthan. Zn deficiency was found to be more prevalent in the states of Rajasthan (75.3%), Madhya Pradesh (66.9%), Tamil Nadu (65.5%), Maharashtra (54.0%), Bihar (44.0%), and Uttar Pradesh (33.1%); in the rest of the country, deficiency varied from 9.6 to 25%. Boron is the second most deficient (23.2%) micronutrient in Indian soils, trailing just Zn (36.5%). B deficiency is more common in calcareous soils of Bihar (39.39%) and Gujarat (18.72%), as well as acid soils of Jharkhand (60%), Nagaland (54.31%), Odisha (51.88%), Meghalaya (47.93%), West Bengal (37%) and Jammu and Kashmir (43%). The primary cause is excessive B leaching in sandy loam soils, and alluvial and less deposits [9, 10, 11]. Iron deficiency is more prevalent in western states, such as Rajasthan (38.34%), Gujarat (25.87%), Maharashtra (23.12%), Haryana (21.72%), and Punjab (21.72%) (13%). Fe deficiency is emerging in states of Andhra Pradesh (12.24%), Telangana (16.65%), Uttar Pradesh (15.56%), Tamil Nadu (12.62)%, and Bihar (12%). In comparison to other micronutrients, manganese deficiency in Indian soils is low (7.10%). Rajasthan (28.28%), Punjab (26.20%), Goa (16.91%), Uttar Pradesh (15.82%), and Chhattisgarh (14.77%) are the states with the highest levels of Mn deficiency. The copper deficiency was observed to be lower in Indian soils.

3. Partial factor productivity: foodgrain production vis-à-vis fertilizers consumption

Fertilizer consumption in India surged after the adoption of fertilizer-responsive high-yielding rice and wheat varieties in 1965–66, later termed the green revolution era.

Consumption of nutrients increased to 32.5 million tons in 2020–21, up from 0.069 Mt in 1950–51 and 2.25 Mt in 1970–71 (Table 1, Figure 4). With 32.5 mt of total fertilizer nutrient use (N+P2O5+K2O), India is second only to China (52.50 mt) globally. Total nutrient consumption (NPK) increased from 2.25 mt in 1970–71 to 32.5 mt in 2020–21, while foodgrain production rose from 108.4 mt to 308.6 mt during the same period. From 1950 to 1951, India’s total NPK consumption increased 471 times, from 1970 to 1971, the increase was 14.44 times. However, partial factor productivity (kg of foodgrain produced per unit of fertilizer nutrient used) fell from 728 kg/kg in 1950–51 to 9.48 kg/kg in 2020–21 (Figure 1).

Years	Foodgrains production (mt)	N use (000 tons)	P2O5 use (000 tons)	K2O use (000 tons)	Total (N+P2O5+K2O) (000 tons)	N/K2O; ratio	P2O5/K2O; ratio	N+P2O5+K2O ratio	PFP (kg/kg)
1950–51	50.8	55	8.8	6	69.8	9.17	1.47	9.17:1.47:1	728.08
1960–61	82.0	211.7	53.1	29	293.8	7.30	1.83	7.30:1.83:1	279.17
1970–71	108.4	1479.3	541	236.3	2256.6	6.26	2.29	6.26:2.29:1	48.05
1980–81	129.6	3678.1	1213.6	623.9	5515.6	5.90	1.95	5.90:1.95:1	23.50
1990–91	176.4	7997.2	3221	1328	12546.2	6.02	2.43	6.02:2.43:1	14.06
2000–01	196.8	11310.2	4382.4	1667.1	17359.7	6.78	2.63	6.78:2.63:1	11.34
2010–11	244.5	16558.2	8049.7	3514.3	28122.2	4.71	2.29	4.71:2.29:1	8.69
2011–12	259.3	17300.3	7914.3	2575.5	27790	6.72	3.07	6.72:3.07:1	9.33
2012–13	257.1	16820.9	6653.4	2061.8	25536.2	8.16	3.23	8.16:3.23:1	10.07
2013–14	265.1	16750.1	5633.5	2098.9	24482.4	7.98	2.68	7.98:2.68:1	10.83
2014–15	252.0	16949.6	6098.9	2532.9	25581.3	6.69	2.41	6.69:2.41:1	9.85
2015–16	251.5	17372.3	6978.8	2401.5	26752.6	7.23	2.91	7.23:2.91:1	9.40
2016–17	275.1	16735.9	6705.5	2508.5	25949.9	6.67	2.67	6.67:2.67:1	10.60
2017–18	285.0	16959.3	6854.4	2779.7	26593.4	6.10	2.47	6.10:2.47:1	10.72
2018–19	284.9	17637.8	6910.2	2680.3	27228.2	6.58	2.58	6.58:2.58:1	10.47
2019–20	297.5	19101.3	7662	2607	29370.4	7.33	2.94	7.33:2.94:1	10.13
2020–21	308.6	20404	8977.9	3153.7	32535.6	6.47	2.85	6.47:2.85:1	9.48

Table 1.

Foodgrain production, NPK consumption, their ratio, and partial factor productivity in India from 1950–51 to 2020–21.

Figure 4.

Fertilizer consumption, foodgrain production, and partial factor productivity.

The decline in PFP at an alarming rate is a sign of decreasing crop response to fertilizer use and declining soil health. The relative use of nitrogen, phosphorus, and potash fertilizers remains highly skewed toward N. In 1950–51, the NPK use ratio was 9.17:1.47:1, which decreased to 6.26:229:1 in 1970–71, and 6.47:285:1 in 2020–21 (Table 1, Figure 4). Use of micronutrients remains negligible in Indian agriculture, which is evident from emerging multi-nutrient deficiencies (Table 2).

Crop	N (%)	P (%)	K (%)	References
Rice	0.45–0.49	0.089–0.104	1.45–1.51	[12]
	0.55–0.66	0.067–0.103	1.463–1.525	[13]
	0.61	0.18	1.38	[14]
	0.71	-	-	[15]
Wheat	0.37	-	1.2	[16]
	0.34	-	-	[15]
	0.62	0.038	1.324	[17]
	0.48	0.16	1.18	[14]
Maize	0.6		--	[15]
	0.52	0.18	1.35	[14]
Sorghum	0.52	0.23	1.34	[14]
	0.537	0.194	1.59	[18]
Pearlmillet	0.45	0.16	1.14	[14]
	0.68	0.194	1.39	[19]
Pulses	1.29	0.36	1.64	[14]
Gram	0.6	0.223	-	[20]
Redgram	0.74	0.28	0.89	[21]
Lentil	1.96	0.199	1.142	[13]
Oilseed	0.8	0.21	0.93	[14]
Groundnut	1.6	0.23	1.37	[14]
Soybean	0.85	-	1.45	[16]
	0.58	-	-	[15]
	1.93	0.14	1.84	[22]
Mustard	0.55–0.65	0.25–0.32	0.39–0.41	[23]
Sunflower	0.55–0.58	0.18–0.22	1.70–1.79	[24]
Sugarcane	0.4	0.18	1.28	[14]
Cotton	0.67	-	0.46	[16]
	0.86	0.3	0.92	[21]
Banana	0.47	0.062	3.84	[25]
	0.7	0.13	7.71	[26]

Table 2.

Major nutrients content in residue of major field crops.

4. Availability of crop residue in India

Crop residues or biomass are non-economical material remains after the removal of economically important parts (generally grains in cereals, seeds in pluses and oilseeds, pods/fruits in vegetables, and fruits) at the harvesting sites and agricultural processing sites [27]. The amount of crop waste is increasing with increasing crop area and cropping intensity. Crop biomass is often treated as wasteful material and is subjected to burning, exporting for other uses, selling, and feeding animals. However, multiple studies have emphasized the importance of crop residues in sustainable agriculture and conservation agriculture, as and means of reducing the chemical fertilizer requirement [16, 28, 29, 30].

Venkatramanan et al., [8] calculated the annual gross crop residue potential (GCR) of India, 696.38 million tons, based on the annual crop production data from 2011–12 to 2015–16, which includes cereal crops, pulse crops, oilseed crops, sugarcane, fiber crops and horticultural and plantation crops (Table 3, Figures 5 and 6). The major contributors to GCR are cereals (52%), bananas and plantain (17.76%), sugarcane (17.13%), oilseed crops (6.26%), fiber crops (4.5%), and pulse crops (1.95%). Cereals contribute about 364.3 mt to the total gross crop residue generated annually in India. The sugarcane crop alone generates about 119 mt/year of gross crop residue. The contribution of oilseeds and pulses is only 43.57 million tons/year and 13.58 million tons/year of gross crop residues, respectively. Uttar Pradesh, Maharashtra, Karnataka, Madhya Pradesh, Tamil Nadu, Punjab, Gujarat, and West Bengal all contribute considerably to crop residue generation (Figures 5 and 6).

Crop	Gross crop residue; Potential (mt)	Surplus Crop residue (mt)	Nutrient supply potential (kg nutrients/t residue)			Gross nutrient supply potential (mt)			Nutrient supply potential based on surplus residue (mt)
			N	P	K	N	P	K	N	P	K
Rice	156.89	46.91	6.00	1.20	14.50	0.94	0.19	2.27	0.28	0.06	0.68
Wheat	149.05	48.67	4.50	1.00	12.30	0.67	0.15	1.83	0.22	0.05	0.60
Maize	43.222	12.83	5.60	1.80	13.50	0.24	0.08	0.58	0.07	0.02	0.17
Sorghum	10.26	3.01	5.30	2.10	14.70	0.05	0.02	0.15	0.02	0.01	0.04
Pearlmillet	4.85	1.52	5.70	1.80	12.70	0.03	0.01	0.06	0.01	0.00	0.02
Gram	7.1	2.7	6.00	2.20	16.00	0.04	0.02	0.11	0.02	0.01	0.04
Redgram	4.93	2.04	7.40	2.80	8.90	0.04	0.01	0.04	0.02	0.01	0.02
Lentil	1.54	0.49	19.60	2.00	11.40	0.03	0.00	0.02	0.01	0.00	0.01
Sugarcane	119.34	44.94	4.00	1.80	12.80	0.48	0.21	1.53	0.18	0.08	0.58
Groundnut	14.46	3.51	16.00	2.30	13.70	0.23	0.03	0.20	0.06	0.01	0.05
Mustard	9.73	2.21	6.00	2.90	4.00	0.06	0.03	0.04	0.01	0.01	0.01
Linseed	0.125	0.031	8.00	2.10	9.30	0.00	0.00	0.00	0.00	0.00	0.00
Safflower	0.305	0.09	8.00	2.10	9.30	0.00	0.00	0.00	0.00	0.00	0.00
Soybean	17.85	4.59	11.20	1.40	16.50	0.20	0.02	0.29	0.05	0.01	0.08
Sunflower	1.1	0.33	5.70	2.00	17.50	0.01	0.00	0.02	0.00	0.00	0.01
Cotton	28.6	12.73	7.70	3.00	6.90	0.22	0.09	0.20	0.10	0.04	0.09
Banana	68.9	27.55	5.90	1.00	57.80	0.41	0.07	3.98	0.16	0.03	1.59
Total	638.25	214.15	132.60	33.50	251.80	3.65	0.94	11.34	1.20	0.32	3.98

Table 3.

Nutrient supplying potential of annually generated crop residue in India (Based on potential and surplus residue, source: [8]).

Figure 5.

Gross crop residue potential of India (Adopted from [8]).

Figure 6.

Surplus crop residue potential of India (Adopted from [8]).

The surplus residue is an unutilized part of the gross crop residue, which is not being used by farmers, and it can be exploited for nutrient recycling in the agroecosystem. Surplus crop residues available for nutrient recycling are estimated to be 214.15 million tons annually, which is nearly 33% of gross crop residue potential. Within the crop category, cereals and sugarcane contribute to an extent of 53.86% and 21.21% to the surplus crop residue in India, respectively.

Rice, wheat, and sugarcane crops all contribute a nearly equal amount to gross residual surplus. About 27.5 million tons of banana crop residue (peels) is added to the estimated surplus crop residue. Fiber crops contribute near about 13.6 million tons in crop residual surplus (stalk, husk, and boll shell). Surplus crop residues from oilseeds and pulse crops amount to 10.8 mt and 5.2 mt, respectively. Uttar Pradesh produces 116.7 mt of total crop waste and 41.8 mt of surplus crop residues, according to estimates. States of Punjab, Madhya Pradesh, Gujarat, Maharashtra, Karnataka, Andhra Pradesh, and Tamil Nadu produce between 32.2 mt and 64.1 million tons of gross crop residues (Figures 5 and 6).

5. Nutrient supplying potential of crop residues in India

Crop residue is an important source of essential plant nutrients; therefore, it should be explored for recycling in agriculture. It is widely known that depending on the crop species, varying amounts of N, P, K, and other nutrients are extracted from and returned to the soil via crop residues [12, 13, 14].

The amount of nutrients that crop residue can provide, as well as the rate at which it decomposes and becomes available to plants, is determined by the type of residue. Based on 17 primary crops, including bananas, India generates 638.25 mt and 214.15 mt of total and surplus agricultural residue, respectively. The potential of nutrient supply from these residues varied with the nutrient content in the residue. Major nutrient content (NPK) in major field crops is given in Table 2. Nitrogen concentration in rice residue ranges from 0.45 to 0.71%, phosphorus from 0.089 to 0.18%, and potassium from 1.2 to 1.52%. Nitrogen content is higher in pulses (1.29%) and legume oilseeds like soybean (1.93%) and groundnut (1.6%). Phosphorus content is relatively lower than N and K, It varied from 0.089 to 0.36%. K content in crop biomass was found to have higher variation among the type of crops, being higher in bananas (3.84–7.7%) to as low as 0.89% in gram.

The per ton of rice residue could supply 6, 1.20, and 14.50 kg of N, P, and K, respectively (Table 2). Similarly, one ton of lentil residue could supply 19.6 kg N and 11.4 kg K. The variation in the nutrient amount of various crop residues depends on the percentage of nutrient content in the particular crop. The potassium supply from one ton of banana residue could be 57 kg. Based on the gross crop residue generated (638.25 mt annually), the nutrient locked in or present in is 16.02 mt of NPK, comprising 3.65 mt of N, 0.94 mt of P, and 11.34 mt of K. However, with the competition for residues in other sectors, the surplus reside available for recycling in the field is 214.15 mt [8], which would supply a total of 5.5 mt of NPK, comprised of 1.20 mt of N, 0.32 mt of P, and 3.98 mt of K. Similarly, Srivastava [31] reported that ten major crops (rice, wheat, sorghum, pearl millet, barley, finger millet, sugarcane, potato tubers, and pulses) of India generate about 312.5 mt of crop residues that have the nutrient supplying potential of about 6.46 million tons of NPK.

6. Conclusion

Crop residue often being treated as wasteful material and burnt on-farm. Annually, India generates about 214.1 mt surplus crop residue, which could supply 5.5 mt of NPK. However, the policy, strategies, and methods need to be explored for better utilization of the whopping amount of crop residue in India. Currently, crop residues are either burnt on the field or used for ruminants as feed, or transported for other uses. To exploit the trapped nutrients in crop biomass, mass awareness and government-backed schemes have to be implemented. The recycling and reuse of crop biomass would not only reduce the dependence on chemical fertilizers but will also enhance the functioning of soil health via increasing various soil physical, chemical, and biological properties.