AGRICULTURE TRIBUNE Monday, June 3, 2002, Chandigarh, India

Crop residues as renewable plant nutrients resource
Gulshan Singh Bahl and Milkha Singh Aulakh
Increasing population heightens the need for enhancing the crop production. Meeting this challenging task requires judicious utilisation of soil, water and plant nutrient resources through adoption of sustainable management practices. The ability of the plants to produce more grains is largely dependent on the availability of adequate and balanced amounts of plant nutrients.

Gene revolution: need to adopt biotechnology
Kulwinder Sandhu
The Asian economic resurgence of the last several years has improved the lives of millions. Yet the region is home to 70 per cent of the world’s 1.3 billion desperately poor people. As most impoverished and hungry people depend on locally grown crops for food, Asian countries need to boost their food production using the latest in technologies.

Farm operations for June




Crop residues as renewable plant nutrients resource
Gulshan Singh Bahl and Milkha Singh Aulakh

Increasing population heightens the need for enhancing the crop production. Meeting this challenging task requires judicious utilisation of soil, water and plant nutrient resources through adoption of sustainable management practices. The ability of the plants to produce more grains is largely dependent on the availability of adequate and balanced amounts of plant nutrients. Therefore, among other resources, the annual cycling of essential plant nutrients through fertilisers, bulky organic manures, green manures or crop residues is essential for maintaining a productive agricultural enterprise while leaving a good soil heritage.


Crop Crop Production (mt) Crop residues Produced (mt) Nutrients removed by crop 
residues (000t)
N P2O5 K2O
Wheat 74.3 111.4 501 282 1422
Rice 88.3 114.7 665 263 1907
Maize 11.5 17.2 102 55 227
Total Pulses 13.1 14.4 165 25 207
Total oil seeds 21.2 42.4 297 195 102
Sugarcane 325.0 6.5 23 3 33
Total 533.4 306.6 1753 823 3898
Chemical fertiliser used     5810 2402 825

Prior to 1966, organic manures were the main source of plant nutrients with the farmers of India. With the introduction of high-yielding dwarf cultivars of field crops (for example wheat and rice), the need for plant nutrients was substantially augmented which could not be met by organics alone because of their low nutrient content. Hence the use of chemical fertilisers became necessary to exploit the crops’ production potential. However, escalating prices of chemical fertilisers and declining soil health has once again focused attention on the need of recycling of organic "wastes" in crop production. There is now immense realisation that the crop residues are an important natural renewable resource of plant nutrients which can be used in conjunction with chemical fertilisers for improving soil health and productivity.

Foodgrains and associated crop residues production

The foodgrain production in India has increased from 52.0 million tonnes in 1951-52 to 205.9 million tonnes in 1999-2000. Although more than half of dry matter produced annually in cereals, legumes, root and tuber crops is the inedible phytomass (above ground plant parts), hardly any nation keeps statistics of the crop residues produced as part of the total crop production. The residual phytomass could be calculated from the studies of harvest index or the ratio of crop yield to the rest of crop’s above ground phytomass. However, variability of environmental and agronomic factors precludes and an exact calculation of the country’s crop residue production. From India’s annual crop production figures, the calculated residue production from major food crops that are grown on nearly 50 per cent of the country’s cultivable area, comes to about 306.6 million tonnes which is nearly 58 per cent of the annual aggregate crop harvest of major food crops (see table).

Annual harvest of major food crops and crop residues in India (1999-2000).

Resource benefits of crop residues

The consumption of chemical fertilisers nutrients (N+P2O5+K2O) in India has registered a spectacular increase from merely 65.6 thousand tonnes in 1951-52 to 18.1 million tonnes in 1999-2000. Nevertheless there is deficit of these nutrients to meet the crop demand which has to come from sources other than chemical fertilisers.

Crop residues are the significant resources of fibre, energy and plant nutrients. However, recycling of nutrients through crop residues is of primary importance in plant nutrition. Crop residues are excellent source of plant nutrients for the reasons: they benefit the soil physically, chemically as well as biologically; they require little or no transportation and can be applied in situ, they do not cost since they are produced along with the grains; and have no health hazard problem like heavy metal contamination, salinity, sodicity or nitrate contamination.

Substantial inter and intra-specific variation in the nutrient content of crop residues allow only approximate calculation of the amounts of total nitrogen (N), phosphorus (P) and potassium (K) mined by them from the soil and fertiliser. Nitrogen and phosphorus removed annually by the crop residues is equivalent to approximately 30 and 34 per cent, respectively, of the nutrients used in the chemical fertilisers. Potassium removal by crop residues represents approximately five times as much as is supplied by fertilisers. Based on recent calculations, the total N, P2O5 and K2O removed by crop residues amounts to approximately 1753, 823 and 3898 thousand tonnes per year.

Considering the current prices of fertiliser NPK from urea, SSP and MOP, the total cost of these nutrients approximates Rs 5,920 crore. Assuming that two-thirds of the crop residues are used as feed for animals and other purposes and only one-third can be mobilised for direct recycling on the farmland approximately Rs 1,973 crore in terms of fertiliser nutrients can be saved by utilising this natural repository of nutrients. Likewise, in Punjab the total NPK removed for the production of 25.2 million tonnes of foodgrains during 1999-2000, comes to 200, 90 and 400 thousand tonnes, respectively, costing about Rs 633 crore, out of which Rs 211 crore worth of the nutrients can by recycled by proper crop residue management.

Why removal or burning of crop residues?

Despite enormous benefits of the crop residues, most of crop reisdues are removed and/or burnt. In Punjab, for instance, about 70 per cent of the total rice straw produced from combine harvest is burnt in open fields. Similarly, after combine-harvesting wheat, 70 per cent of wheat straw is converted to bhusa for animal feed and the remaining burnt in the field. Unlike wheat straw, rice straw is not used as a cattle-feed because of high silica and oxalate content it.

Besides the loss of organic matter and plant nutrients, burning of crop residues also causes atmospheric pollution due to the emission of toxic gases like methane, carbon dioxide or nitrous oxide that poses a threat to human and ecosystem health. In the weeks following the rice harvest, flames and dense smog can be seen above the rice fields which engulf the vast surroundings. The nightmare of October 15, 1998, when the thick smog made the atmosphere suffocating in Punjab is a living example of the recent past. On the contrary, the common justification advocated by the farmers regarding burning of crop residues are to ensure a quick seedbed preparation; get rid of the pest, diseases, mice, etc. which harbour the residues, and avoid risk of reduced crop yields associated with the incorporation of wide C:N ratio residues. Notwithstanding the validity of these contentions, and going by the pros and cons, blanket burning of crop residues can hardly be justified.

Efficient management of crop residues

(i) Mechanical difficulties in tilling residue-laden fields can be managed by using a straw chopper and spreading the residues as evenly as possible, and (ii) no doubt, decomposition is a problem for residue with a high C:N ratio such as those of cereals which leads to locking up of inorganic nitrogen which the plants are unable to utilise. This is however, temporary and manageable. Within a few days or weeks after available carbon gets depleted by the microorganisms, net mineralisation occurs and unlocking of inorganic nitrogen also sets in. Based on their C:N ratio, the crop residues can be classified as high carbon and low nitrogen (about 80:1) and high carbon and nitrogen (about 20:1) materials. The former includes stubbles, weeds, wheat and rice straw, sugarcane trash, etc. and the latter includes legumes such as pea and moong, sunflower and water hyacinth, etc. Extensive long-term experiments at the Punjab Agricultural University research farm showed that integrated use of chemical fertilisers and legume green manures counteract the adverse effect of incorporating wide C:N ratio (high carbon and low nitrogen) crop residues on the crops production. So depending upon their nutrient content, cellulose, lignin content and succulence these residues can be recycled either by direct ploughing into soil or through composting.

Extension efforts are, therefore, urgently needed to educate the farmers about the immense benefits of recycling of crop residues in farming in improving the soil health, crop productivity, supply of nutrients and reducing cost of production and protecting environment. Simultaneously evolving regulations and their enforcement prohibiting the burning of crop residues while providing some incentives could facilitate the adoption of such eco-friendly practice of utilising the crop residues.



Gene revolution: need to adopt biotechnology
Kulwinder Sandhu

The Asian economic resurgence of the last several years has improved the lives of millions. Yet the region is home to 70 per cent of the world’s 1.3 billion desperately poor people. As most impoverished and hungry people depend on locally grown crops for food, Asian countries need to boost their food production using the latest in technologies. Innovative biotechnology can continue to transform Asia’s agrarian economies to produce more food with less land, water, labour and chemicals while maintaining their natural biodiversity. Increasing productivity per unit of land — not converting more forest to farming — is the only solution to meeting food requirements for Asia. Locally grown food makes it affordable for both urban and rural poor while generating more jobs and income.

Though China has become a global leader in biotechnology, elsewhere in Asia the brakes are being put on this technology. Non-government agencies from developed countries are spreading groundless fears about biotechnology. The task of producing more food on the farm is daunting, given the challenges of insects, disease, dwindling water supply and steadily degrading soils. It is an urgent challenge. Asia can’t afford to ignore scientific innovations used increasingly by the rest of the world. Let us not forget the Green Revolution and the resistance that it spurred 30 years ago. The gallant leadership in India paved the way for this miracle by importing 18,000 tonnes of Mexican wheat seeds despite massive criticism at the time. Wheat production since then has increased several fold in India. Asian farmers have increased rice yields by 2.5 per cent each year since 1965, enabling more than one billion more people to be fed.

The gains from such increases are now slowing. Population growth is outstripping yields from traditional technologies. Clearly, the once revolutionary technologies of the Green Revolution now have to incorporate new technologies of the "gene revolution." Trials with biotechnology-enhanced rice in China show that the crop can be protected against loss from pests while minimising the use of pesticides. The much-heralded "golden rice" with increased vitamin A can reduce the problems of blindness and disease in hundreds of thousands of Asian children. The International Rice Research Institute has developed rice that can tolerate submergence, a common source of crop loss due to river overflows in Bangladesh and Vietnam. Hundreds of university labs across Asia are using biotechnology to improve food crops such as chickpeas with disease resistance and papayas that don’t rot easily.

Biotechnology also helps protect the environment. Thanks to technology, cotton farmers in the USA have eliminated the use of more than 4 million kg of pesticides, while production increased by 100 million kg per year. Soyabean farmers have embraced reduced tillage, saving valuable topsoil from erosion. It is not just rich farmers who have adopted these new technologies; more than a million small-scale Chinese farmers have profited from pest-resistant cotton cutting down costs and the use of pesticides. The value from biotechnology is delivered through improved seeds. No new machines or chemicals are needed; just the availability of improved seed at affordable cost for farmers. Globally, more than 40 million hectares of land is planted with these crops. Farmers in 15 countries grew a trillion plants enhanced by biotechnology in the past year, feeding hundreds of millions of people. To date, not a single piece of scientifically proven evidence of harm or injury has been reported.

Asians must be on guard against the luxuries of the radical environmental movement — an unwanted export from its former colonial rulers. Romantic notions of less intensive farming are naive at best and dangerous at worst if the expectation is that low productivity will feed increasing populations. Asian nations and their leaders must distinguish between reliable, credible people (those who have actually done something about a problem) and those who are merely talking. As Asian countries surge ahead, they must embrace the best available technology to help feed their people while protecting the environment. Otherwise, the dream of the "Asian century" may remain just a dream.



Farm operations for June


— Irrigate the crop at 7 to 10 days’ interval and apply the second dose of 65 kg of urea per acre along the cane rows.

— Check attack of top borer by applying 12 kg of Carbofuran 3 G Orphorate at the base of shoots of sugarcane during the last week of June. Earth up slightly and give light irrigation to the crop immediately.

— Black bug sometimes becomes serious, particularly on ratoon crop during this month. Check this pest by spraying 350 ml of Thiodan 35 EC/Dursban/Lethal 20 EC or 225 ml of Sumithion/Folithion/Accothion 50 EC in 400 litres of water per acre. Direct the spray into the leaf whirl.

— Due to prolong dry weather conditions, mites may also cause severe damage to this crop. Spray 400 ml of Malathion 50 EC in 100 litres of water per acre. Remove "baru" weed growing around the sugarcane field.

— Check thrips by spraying 400 ml/acre of Malathion 50 EC or Thiodam 35 EC

350 ml/acre in 100 litres of water.


— In situations where itsit emerges after first irrigation or with the rain shower, Stomp 30 EC

1 litre/acre dissolved in 200-250 litres of water can also be applied as post-emergence after first irrigation to cotton. If the weeds emerge before the application of the herbicide, a light hoeing/inter-culture may be done as the Stomp does not control the emerged weeds.

— Apply 30 to 35 kg of urea along the American cotton rows after final thinning.

— Apply first irrigation to the May-sown crop after about four weeks of sowing and give hoeing to keep the weeds under check.

— Direct spray of Glycel/Roundup (glyphosate) at 1.0 litre/acre or Gramoxone (paraquat) at 0.5 litre/acre at 6 to 8 weeks after sowing in between the cotton rows is very good for effective control of weeds. Avoid application of the herbicide on the top foliage of the cotton plants. Application of either herbicide at 6 to 8 weeks after sowing when crop is 40 to 45 cm high can replace hand weeding/hoeing etc.

— Control sucking pests such as jassid/whiteflies/thrips etc., by spraying 250 ml of Rogor 30 EC or 300 ml of Metasystox 25 EC/Anthio 25 EC or 75 ml Dimecron 85 SL in 100 litres of water per acre.


— To the nursery-sown during middle of May, apply second dose of nitrogen to get the seedlings ready for transplanting.

— Start transplanting varieties, PR-116, PR-114, PR-113, from June 10 onward and variety PR-115 from June 20 onward. Variety PR-115 vacates the fields earlier and facilitates timely sowing of potato, peas or berseem crops.

— Paddy seedlings in the nursery, particularly in light-textured soils become yellow or whitish. To check this, spray 0.5 to 1 kg ferrous sulphate dissolved in 100 litres of water. Repeat this treatment 3 to 4 times at 4 days interval.

— At the time of transplanting, apply 37 kg of urea per acre on medium soils. Phosphorus application mey be omitted where paddy is to follow wheat receiving recommended dose of phosphorus. In soil testing low in phosphorus, 75 kg single superphosphate per acre may also be applied.

— Zinc deficiency is generally noticed in paddy. Therefore, apply 25 kg of zinc sulphate per acre at the time of puddling.

— Dhaincha for green manuring be buried at the time of puddling.

— For control of weeds, use 1200 ml of any recommended formulations of Butachlor 50 EC or 500 ml of Anilofos 30 ec or Pretilachlor 50 EC

600 ml or Stomp 30 EC

1000-1200 ml/acre by mixing with 60 kg of sand. Broadcast any one of the herbicides uniformly in standing water within 2 to 3 days of transplanting.

— Avoid early planting of rice to keep under check the BLB of rice.

— Stress should be laid on the proper use of fertiliser as excess use of nitrogen may lead to outbreak of BLB.

— Prefer to grow PR-116, PR-114, PR-111/PR-113 variety in BLB prone areas.

— Basmati-386 and Basmati-370 are photosensitive and mature late, therefore, nursery of these varieties should be sown in second fortnight of June.


— Under irrigated conditions, sow groundnut from May-end to June 10 after applying pre-sowing irrigation. Use of bolder seeds ensures high yields.

— Treat the seed with 5 g Thiram or 3 g Indofil M-45/kg of seed before sowing, to control coller rot disease.

— Use 40 kg of seed for M-335, 38 kg for M-522, SG-84 and 25 kg for M-37.

— Apply 50 kg of superphosphate and 13 kg of urea per acre with last ploughing. Also 50 kg gypsum/acre may be applied.

— Treat the seed with 12.5 ml of Dursban 20 EC per kg kernels, apply 4 kg Thimet 10 G or 13 kg of Furadan 3 G grannules per acre in the soil at or before sowing for preventing the attack of whitegrub in groundnut.

— Progressive Farming, PAU