Crop Residue for Soil Cover: Constraints and Way Ahead
Authors: Deep Mohan Mahala*, Rajendra Kumar Yadav
Sustained improvement in crop productivity, and resilience of farming systems can only be realized if crops are grown on healthy soils. To maintain a healthy state of soil, one of the key efforts needed is to retain crop residue on soil surface. Keeping residue on soil surface as mulch is one of the essential principles of CA in conjunction with other principles such as minimal soil disturbance and crop rotation. These principles, if adopted in a holistic manner, help in establishing and sustaining healthy soil systems that positively impact the farming system, thereby improving crop, and livestock productivity. Among other benefits, these help in reducing soil erosion, promote in situ water conservation, and enhance soil quality through improved biological activity, and organic matter content. It is affirmed that most benefits of CA accrue only when minimal or no soil disturbance (zero-tillage) is practiced along with retention of residue or by growing cover crops. There is ample scientific evidence from literature on CA that no-till without soil cover results in poor yields.
The practice of removal of crop residue in rainfed regions, and burning it in irrigated regions has resulted in degraded soil structure compared to when residue have been retained on them. This has had a direct implication on crop production; largely on account of being influenced by improved soil quality parameters such as soil aggregation, water infiltration, and microbial biomass. Benefits of Crop Residue as Soil Cover Residue maintained on soil surface serve as a protective layer from the impacts of excessive rainfall and temperature. It helps in improving soil health by increasing infiltration, reducing surface sealing, soil crusting, and moisture evaporation. However, there are only few options available to farmers to divert residue for reaping such benefits. Though CA advocates this approach, socio-economic factors govern its adoption, given the opportunity cost attached to crop residue.
Depending on local specificities, scarcity of sufficient crop residue as soil cover for the succeeding crop makes establishment of CA based practices more challenging. Crop residue comprises an important source of fodder/feed for livestock in majority of farming systems in India. The integrated crop–livestock farming system approach lays much emphasis on needs of livestock to contribute to income and food security of the household. Given the importance of crop residue as a soil cover, it is important to understand farmer’s perception towards it. Non-availability of fodder for animals and fuel for household are key constraints with majority of farmers who approve of the practice of retention of crop residue as soil cover. Termite infestation, and need for increased ploughing was perceived by the farmers as other important reasons preventing farmers from retaining crop residue on the fields.
While availability of an appropriate seed drill can enable seeding crops without tilling the soil, the availability of crop residue for keeping the soil covered will pose as a key issue to farmers in the context of crop-livestock farming system. Apart from household consumption, a significant amount of these crop residue/by-products are sold in the market for cash income. There is competitive demand for crop residue for diversified uses such as fuel, fodder or even construction material and roofing and could constitute a serious bottleneck to the implementation of zero-till system with residue retention. The key issue lies in making farmers understand its judicious applicability to take needed decisions.
Successful transition to CA based farming systems will demand deeper understanding of issues involved and laying down of mechanisms that would facilitate CA adoption in the region. Issues that need to be further explored to encourage the practice of soil cover through ongoing research effort include:
• Understanding prevailing crop residue scenario and usage in selected clusters of the region
• Identification of alternate mechanisms of meeting fodder & fuel needs of farmers to help make crop residue available as soil cover.
These would include encouraging generation of more biomass to meet fodder and fuel needs through pursuit of three areas of effort:
* COVER CROPS: The choice of cover crop depends on climatic features, prevailing soil condition (pH, salinity, water logging), farming system, and seed availability. A broad range of species could serve as cover crops mostly during rabi season. fodder crops such as Oats, Berseem (Trifolium sp.) and local varieties such as Chikori, intercropping with legume crops such as cowpea (Vigna unguiculata), Sesbania sp., and beans such as Mung ( Vigna mungo), Clusterbean/Guar (Cyamopsis tetragonolobus) along with short-duration variety of pearl-millet (Pennisetum glaucum) maize (Zea mays), and sorghum can be grown.
* GRASSES: Some of the arid forage grasses that could be introduced for pasture, grazing, and hay crops after the onset of monsoon (kharif season) include: Napier (hybrid), Stylos, Guine, Anjan and Dinanath grass varieties. Forage legumes could be seeded in perennial grasses to provide protein in animal diets and nitrogen to soil from rhizobium fixation.
* AGROFORESTRY: This intervention will include introduction of trees and shrubs to serve needs of fodder and fuel for the region. Trees and shrubs with potential for fodder, owing to their good growth characteristics, cause minimal soil disturbance, help to prevent nutrient losses, and provide biomass for feed in a short time. In addition to providing fodder, fuel, wood, and other products, trees & shrubs selected will promote soil and water conservation, enhance soil fertility, and act as windbreaks for nearby crops. Promotion of trees/shrubs suitable to the area for alternate biomass generation could be Leucaena and Prosophis.
Generating more biomass for fodder and fuel needs through above options would require effective use of available land. Overall, these interventions will address the need to lay down a strategy with direct policy implications for gradual conversion to CA based farming system, and to help increase availability of crop residue/biomass while keeping the livestock & fodder needs intact for farmers.
About Author / Additional Info:
Ph.D. Scholar, Division of Soil Science and Agricultural Chemistry, IARI, New Delhi