The United Nations declared 2016 as the International Year of Pulses (grain legumes) under the banner ‘nutritious seeds for a sustainable future’. A second green revolution is required to ensure food and nutritional security in the face of global climate change. Grain legumes provide an unparalleled solution to this problem because of their inherent capacity for symbiotic atmospheric nitrogen fixation, which provides economically sustainable advantages for farming. In addition, a legume-rich diet has health benefits for humans and livestock alike. However, grain legumes form only a minor part of most current human diets, and legume crops are greatly under-used. Food security and soil fertility could be significantly improved by greater grain legume usage and increased improvement of a range of grain legumes. The current lack of coordinated focus on grain legumes has compromised human health, nutritional security and sustainable food production.

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Neglecting legumes has compromised human health and sustainable food production

Climate change has increased the occurrence of extreme weather patterns globally, causing significant reductions in crop production, and hence threatening food security. In order to meet the food demand of the growing world population, a faster rate of genetic gains leading to productivity enhancement for major crops is required. Grain legumes are an essential commodity in optimal human diets and animal feed because of their unique nutritional composition. Currently, limited water is a major constraint in grain legume production. Root system architecture (RSA) is an important developmental and agronomic trait, which plays vital roles in plant adaptation and productivity under water-limited environments. A deep and proliferative root system helps extract sufficient water and nutrients under these stress conditions. The integrated genetics and genomics approach to dissect molecular processes from genome to phenome is key to achieve increased water capture and use efficiency through developing better root systems. Success in crop improvement under drought depends on discovery and utilization of genetic variations existing in the germplasm. In this review, we summarize current progress in the genetic diversity in major legume crops, quantitative trait loci (QTLs) associated with RSA, and the importance and applications of recent discoveries associated with the beneficial root traits towards better RSA for enhanced drought tolerance and yield.

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Genetic diversity of root system architecture in response to drought stress in grain legumes.

Serious water deficits are threatening agricultural sustainability in many regions of the South Asia (SA). While the increase in crop production of irrigated rice–wheat system in SA has been impressive since the 1970s, the low water productivity (WP) has led to the depletion of surface water and groundwaters. In this chapter we have discussed the availability of water resources in SA, identified the positive effects of soil and water management and crop genetic improvement on WP, and then described knowledge gaps and research priorities to further improve the WP with special emphasis on wheat-based cropping systems in irrigated and rainfed regions of SA. A single approach would not be able to tackle the forthcoming challenge of producing more food and fiber with limited or even reduced available water. Integrating irrigation water-saving techniques (water-saving irrigation methods, deficit irrigation, modernization of irrigation system, etc.) with agronomic and soil manipulations viz., optimum irrigation scheduling, direct-seeded rice, alternate wetting and drying in puddle transplanted rice, raised bed planting, crop diversification, conservation tillage, crop residue management, and conjunctive use of good quality (canal) water. Improved soil water management practices for rainfed regions include reducing runoff, rainwater harvesting and recycling, conserving rainwater in the root zone by reducing evaporation losses, and optimal nutrient management. The low WP in farmer’s fields compared with well-managed experimental sites indicates the need for more efforts to transfer water-saving technologies to the farmers. In future we need to increase scientific understanding of the effects of agronomic management on WP across various soil and climate conditions; improve irrigation practices (timing and amounts) and methods (drip and sprinkler) based on real-time monitoring of water status in soil-crop systems; and maximize WP by managing water resources and allocation at regional scales in wheat-based cropping systems.

Improving Water Productivity of Wheat-Based Cropping Systems in South Asia for Sustained Productivity

Grain legumes form an important component of the human diet, feed for livestock and replenish soil fertility through biological nitrogen fixation. Globally, the demand for food legumes is increasing as they complement cereals in protein requirements and possess a high percentage of digestible protein. Climate change has enhanced the frequency and intensity of drought stress that is posing serious production constraints, especially in rainfed regions where most legumes are produced. Genetic improvement of legumes, like other crops, is mostly based on pedigree and performance-based selection over the last half century. For achieving faster genetic gains in legumes in rainfed conditions, this review article proposes the integration of modern genomics approaches, high throughput phenomics and simulation modelling as support for crop improvement that leads to improved varieties that perform with appropriate agronomy. Selection intensity, generation interval and improved operational efficiencies in breeding are expected to further enhance the genetic gain in experiment plots. Improved seed access to farmers, combined with appropriate agronomic packages in farmers’ fields, will deliver higher genetic gains. Enhanced genetic gains including not only productivity but also nutritional and market traits will increase the profitability of farmers and the availability of affordable nutritious food especially in developing countries.

Accelerating genetic gains in legumes for the development of prosperous smallholder agriculture: integrating genomics, phenotyping, systems modelling and agronomy.

India ranks first in rainfed agriculture globally in both area (86 Mha) and the value of produce. Rainfed regions in India contribute substantially toward food grain production including 44% of rice, 87% of coarse cereals (sorghum (Sorghum bicolor), pearl millet (Pennisetum glaucum), maize (Zea mays)), and 85% of food legumes, 72% of oilseeds, 65% of cotton, and 90% of minor millets. Overall, the rainfed areas produce 40% of the food grains, support two-thirds of the livestock population, and are critical to food security, equity, and sustainability...

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Potential and Challenges of Rainfed Farming in India

In India, cultivation of legumes forms an integral part of the rainfed production systems; however, their productivity over the years has remained low and unstable. Soybean and groundnut are the major oilseed crops and pigeonpea and chickpea are the major pulse crops of the country. In the present study, we have: a) characterized the distribution of these legumes in different production zones, agro-ecological zones (AEZs) and states of India; b) estimated the rainfed (water-limited) potential, achievable and current levels of farmers’ yields; c) quantified yield gaps between farmers’ yields and rainfed potential yields; and d) suggested possible ways to abridge the yield gaps. Using CROPGRO and APSIM (for pigeonpea) suite of crop models and historical weather data, rainfed potential yields and water balance of the four legumes were estimated for selected locations representing different production zones in India. The simulated rainfed potential yields were supplemented with the research station yield data of rainfed trials of the All India Coordinated Research Projects (AICRP) for respective crops. Achievable yields of the crops for the locations were taken from the Front Line Demonstrations conducted on-farm with improved technology. District average yields were considered as the farmers’ yields. Based on these data, the yield gaps between potential and achievable yields (YG I), between achievable and farmers’ yields (YG II) and total yield gaps between potential and farmers’ yields were estimated. The farmers’ average yield of crops is 1040 kg ha-1 for soybean, 1150 kg ha-1 for groundnut, 690 kg ha-1 for pigeonpea and 800 kg ha-1 for chickpea in India. Large spatial and temporal variability was observed in the yield gaps of the four legumes across the production zones. Total yield gap for the production zones ranged from 850 to 1320 kg ha-1 for soybean, 1180 to 2010 kg ha-1 for groundnut, 550 to 770 kg ha-1 for pigeonpea and 610 to 1150 kg ha-1 for chickpea. YG II formed a significant part of the total yield gap of the four legumes, indicating the need to scale-up the improved crop production technologies from on-farm demonstration sites to farmers in the production zones. Total yield gaps of legumes for the AEZs and states of India were in the similar range as for the production zones. Simulated rainfed potential yields and total yield gaps across different locations for the four legumes showed a positive and significant curvilinear relationship with crop season rainfall. Estimated surface runoff constituted 11 to 54% of total rainfall received during growing period of the rainy season legumes. To abridge the yield gaps of legumes, integrated watershed management approach comprising of in-situ soil and water conservation, water harvesting and groundwater recharging for supplemental irrigation and improved crop management technologies is needed.

Yield Gap Analysis of Soybean, Groundnut, Pigeonpea and Chickpea in India Using Simulation Modeling:Global Theme on Agroecosystems Report no. 31

Climate change is one of the major challenges in 21st century faced by Agriculture in India, more
so in the Semi-Arid Tropics (SAT) of the country. In recent years, natural and anthropogenic factors have
impacted climate variability and contributed to a large extent to climate change. Based on one degree
gridded data of India Meteorological Department (IMD) for 34 years (1971-2004), climatic water balances
are computed for 351 pixels in India and used for classifying in to six climate types following Thornthwaite’s
moisture regime classification and areas falling under different climatic zones in India are delineated.
Considerable changes in the country’s climate area observed between the two periods; 1971-90 and
1991-2004. Increased semi-arid area by 8.45 M ha in five states viz., Madhya Pradesh, Bihar, Uttar
Pradesh, Karnataka and Punjab, and decreased semi-arid area by 5 M ha in eleven states, contributed
to overall increase in SAT area of 3.45 M ha in the country.Overall, there has been a net reduction of
10.71 M ha in the dry sub-humid area in the country. Results indicated that dryness and wetness are
increasing in different parts of the country in the place of moderate climates existing earlier in these
regions. ICRISAT’s Hypothesis of Hope through Integrated Genetic and Natural Resources Management
(IGNRM) using climate ready crops and Integrated Watershed Management could be a potential adaptation
strategy by bridging the yield gaps for developing climate resilient agriculture in the country.

A V R K Rao

Papers

Yield Gap Analysis of Soybean, Groundnut, Pigeonpea and Chickpea in India Using Simulation Modeling:Global Theme on Agroecosystems Report no. 31

Increased arid and semi-arid areas in India with associated shifts during 1971-2004