Suhas P. Wani

AFLP-based molecular characterization of an elite germplasm collection of Jatropha curcas L., a biofuel plant.

Amplified fragment length polymorphism (AFLP) was employed to assess the diversity in the elite germplasm collection of Jatropha curcas, which has gained tremendous significance as a biofuel plant in India and many other countries recently. Forty-eight accessions, collected from six different states of India, were used with seven AFLP primer combinations that generated a total of 770 fragments with an average of 110 fragments per primer combination. A total of 680 (88%) fragments showed polymorphism in the germplasm analyzed, of which 59 (8.7%) fragments were unique (accession specific) and 108 (15.9%) fragments were rare (present in less than 10% accessions). In order to assess the discriminatory power of seven primer combinations used, a variety of marker attributes like polymorphism information content (PIC), marker index (MI) and resolving power (RP) values were calculated. Although the PIC values ranged from 0.20 (E-ACA/M-CAA) to 0.34 (E-ACT/M-CTT) with an average of 0.26 per primer combination and the MI values were observed in the range of 17.60 (E-ACA/M-CAA) to 32.30 (E-ACT/M-CTT) with an average of 25.13 per primer combination, the RP was recognized the real attribute for AFLP to determine the discriminatory power of the primer combination. The RP values for different primer combinations varied from 23.11 (E-ACA/M-CAA) to 46.82 (E-ACT/M-CTT) with an average of 35.21. Genotyping data obtained for all 680 polymorphic fragments were used to group the accessions analyzed using the UPGMA-phenogram and principal component analysis (PCA). Majority of groups obtained in phenogram and PCA contained accessions as per geographical locations. In general, accessions coming from Andhra Pradesh were found diverse as these were scattered in different groups, whereas accessions coming from Chhattisgarh showed occurrence of higher number of unique/rare fragments. Molecular diversity estimated in the present study combined with the datasets on other morphological/agronomic traits will be very useful for selecting the appropriate accessions for plant improvement through conventional as well as molecular breeding approaches.

Rainfed agriculture: unlocking the potential

1. Rainfed Agriculture - Past Trends and Future Prospects 2. Zooming in on the Global Hotspots of Rainfed Agriculture in Water Constrained Environments 3. Water Resource Implications of Upgrading Rainfed Agriculture - Focus on Green and Blue Water Trade-offs 4. Tectonics-climate Linked Natural Soil Degradation and its Impact in Rainfed Agriculture: Indian Experience 5. Determinants of Crop Growth and Yield in a Changing Climate 6. Yield Gap Analysis: Modeling of Achievable Yields at Farm Level 7. Can Rainfed Agriculture Feed the World? - An Assessment of Potentials and Risk 8. Opportunities for Improving Crop-water Productivity Through Genetic Enhancement of Dryland Crops 9. Water Harvesting for Improved Rainfed Agriculture in the Dry Environments 10. Supplemental Irrigation for Improved Rainfed Agriculture: In WANA Region 11. Opportunities for Water Harvesting and Supplemental Irrigation for Improving Rainfed Agriculture in Semi-arid Areas 12. Integrated Farm Management Practices and Up Scaling the Impact for Increased Productivity of Rainfed Systems 13. Challenges of Adoption and Adaptation of Land and Water Management Options in Smallholder Agriculture: Synthesis of Lessons and Experiences 14. Scaling-out Community Watershed Management for Multiple Benefits in Rainfed Areas.

Rainfed agriculture: past trends and future prospects

This chapter discusses the past and present trends and future direction of rainfed agriculture. Topics covered include: the relationship between rainfed agriculture and water stress; crop yields in rainfed areas; constraints in rainfed agriculture areas; the potential of rainfed agriculture; and the new paradigm in rainfed agriculture.

Plant-growth-promoting rhizobacteria: drought stress alleviators to ameliorate crop production in drylands

Drylands are known for being a drought stressed environment, which is an alarming constraint to crop productivity. To rescue plant growth in such stressful conditions, plant-growth-promoting rhizobacteria (PGPR) are a bulwark against drought stress and imperilled sustainability of agriculture in drylands. PGPR mitigates the impact of drought stress on plants through a process called rhizobacterial-induced drought endurance and resilience (RIDER), which includes physiological and biochemical changes. Various RIDER mechanisms include modification in phytohormonal levels, antioxidant defense, bacterial exopolysaccharides (EPS), and those associated with metabolic adjustments encompass accumulation of several compatible organic solutes like sugars, amino acids and polyamines. Production of heat-shock proteins (HSPs), dehydrins and volatile organic compounds (VOCs) also plays significant role in the acquisition of drought tolerance. Selection, screening and application of drought-stress-tolerant PGPRs to crops can help to overcome productivity limits in drylands.

Enhancing agricultural productivity and rural incomes through sustainable use of natural resources in the Semi Arid Tropics

BACKGROUND A participatory watershed management approach is one of the tested, sustainable and eco-friendly options to upgrade rain-fed agriculture to meet growing food demand along with additional multiple benefits in terms of improving livelihoods, addressing equity issues and biodiversity concerns. RESULTS Watershed interventions at study sites in Thailand (Tad Fa and Wang Chai) and India (Kothapally) effectively reduced runoff and the associated soil loss. Such interventions at Xiaoxincun (China) and Wang Chai improved groundwater recharging and availability. Enhanced productive transpiration increased rainwater use efficiency for crop production by 13-29% at Xiaoxincun; 13-160% at Lucheba (China), 32-37% at Tad Fa and 23-46% at Wang Chai and by two to five times at Kothapally. Watershed interventions increased significantly the additional net returns from crop production as compared with the pre-watershed intervention period. Increased water availability opened up options for crop diversification with high-value crops, including increased forage production and boosted livestock-based livelihoods. CONCLUSION In dryland tropics, integrated watershed management approach enabled farmers to diversify the systems along with increasing agricultural productivity through increased water availability, while conserving the natural resource base. Household incomes increased substantially, leading to improved living and building the resilience of the community and natural resources.

Evaluation and application of the CROPGRO-Soybean simulation model in a Vertic Inceptisol

Crop simulation models are valuable research tools in agricultural decision making. In order to increase its general applicability, models need to be evaluated in diverse conditions. To achieve this, CROPGRO-Soybean model was evaluated on Vertic Inceptisols in a climatically variable semi-arid tropical condition. The model predicted reasonably the temporal changes in leaf area index, biomass and grain yield. The model was used to develop yield–evapotranspiration (ET) relationship, and to assess the influence of soil water-storage capacity on yield. Yield was linearly related to ET and was reduced non-linearly as soil depth decreased. The yield reduction was minimal when depth decreased from 90 to 67 cm but severe reduction occurred when depth decreased below 45 cm. There exists a threshold soil depth (37 cm), below which crop productivity in Vertic Inceptisols cannot be sustained, even in good rainfall years. There is an urgent need to develop sustainable natural resource management technology to prevent further degradation of Vertic Inceptisol. CROPGRO-Soybean model can be successfully used as a research tool to evaluate the risks associated in adapting such technologies.

Soybean–chickpea rotation on Vertic Inceptisols: I. Effect of soil depth and landform on light interception, water balance and crop yields

During 1995-1997 a field study was conducted at the ICRISAT Centre, Patancheru, Andhra Pradesh, India, on a Vertic Inceptisol watershed to study the effect of two soil depths, shallow (<50 cm soil depth) and medium-deep (=50 cm soil depth), and two landform treatments, flat and broadbed-and-furrow (BBF) systems, on productivity and resource-use efficiency of a soyabeans-chickpeas rotation. Soyabeans grown on flat landform on medium-deep soil had a higher leaf area index and more light interception compared with the soyabeans grown on the BBF landform. This resulted in an increase in mean seed yield for the flat landform (2.12 t/ha) compared with the BBF landform (1.87 t/ha). However, the landform treatments on shallow soil did not affect soyabean yields. The soyabean yield was higher on the medium-deep soil (1.76 t/ha) than on the shallow soil (1.55 t/ha) during 1995-1996, but were not different during 1996-1997. In both years chickpea yields and total system productivity (soyabean + chickpea yields) were greater on medium-deep soil than on the shallow soil. Total run-off was higher on the flat landform (25% of seasonal rainfall) than on the BBF landform (20% of seasonal rainfall). This concomitantly increased profile water content (10-30 mm) of both soils in BBF compared with the flat landform treatment during 1995-1996, but not during 1996-1997. Deep drainage was higher in the BBF landform than in flat, especially for the shallow soil. Across landforms and soil depths, water use (evapotranspiration) by soyabeans-chickpeas rotation during 1996-1997 ranged from 496 to 563 mm, which accounted for 54-61% of the rainfall. These results indicate that while the BBF system is useful in decreasing run-off and increasing infiltration of rainfall on Vertic Inceptisols, there is a need to increase light use by soyabeans on BBF during the rainy season to increase its productivity. A watershed-based farming system needs to be adopted to capture significant amount of rain water lost as run-off and deep drainage. The stored water can be used for supplemental irrigation to increase productivity of soyabean-based systems leading to overall increases in resource-use efficiency, crop productivity and sustainability.

Yield gap analysis: modelling of achievable yields at farm level

This chapter quantifies the potential yields and yield gaps between the potential and the actual yields obtained by the farmers for the major rainfed crops grown in the selected countries in South and South East Asia (India, Thailand and Vietnam), SSA and the West Asia and North Africa (WANA) region, where food security is increasingly threatened because of expected increase in population and degradation of natural resources. This analysis is expected to help identify the opportunities and constraints for yield improvement with the implementation of the improved crop production and natural resource management technologies for the rainfed regions.

Soybean–chickpea rotation on Vertic Inceptisols II. Long-term simulation of water balance and crop yields

A field study was conducted on a Vertic Inceptisol during 1995-1997 seasons at the ICRISAT Centre, Patancheru, India, to study the effect of two landforms (broadbed-and-furrow (BBF) and flat) and two soil depths (shallow and medium-deep) on crop yield and water balance of a soyabean-chickpea rotation. Using two seasons experimental data, a soyabean-chickpea sequencing model was evaluated and used to extrapolate the results over 22 years of historical weather records. The simulation results showed that in 70% of years total runoff for BBF was >35 mm (range 35-190 mm) compared with >60 mm (range 60-260 mm) for flat on the shallow soil. In contrast on the medium-deep soil it was >70 mm (range 70-280 mm) for BBF compared with >80 mm (range 80-320 mm) for the flat landform. The decrease in runoff on BBF resulted in a concomitant increase in deep drainage for both soils. In 70% of years, deep drainage was >60 mm (range 60-390 mm) for the shallow soil and ranged from 10 to 280 mm for the medium-deep soil. In 70% of years, the simulated soyabean yields were >2.2 t/ha (range 2.2-3.0 t/ha) and were not influenced by landform or soil depth. In the low rainfall years, yields were marginally higher for the BBF than for the flat landform, especially on the shallow soil. Simulated chickpea yields were higher for the medium-deep soil than for the shallow soil. In most years, marginally higher chickpea yields were simulated for the BBF than for the flat landform on both soil types. In 70% of years, the chickpea yields were >0.5 t/ha (range 0.5-1.5 t/ha) for the shallow soil, and >0.8 t/ha (range 0.8-1.96 t/ha) for the medium-deep soil. Total productivity of a soyabean-chickpea rotation was >3.0 t/ha (range 3.0-4.15 t/ha) for the shallow soil and >3.45 t/ha (range 3.45-4.7 t/ha) for the medium-deep soil in 70% of years. These results showed that in most years BBF increased rainfall infiltration into the soil and had marginal effect on yields of soyabeans and chickpeas. Crop yields on Vertic Inceptisols can be further increased and sustained by adopting appropriate rain water management practices for exploiting surface runoff and deep drainage water as supplemental irrigation to crops in a watershed setting.

Balanced and integrated nutrient management for enhancedand economic food production: case study from rainfed semi-arid tropics in India

Soil degradation in the semi-arid tropics (SAT) is mainly responsible for low crop and water productivity. In Madhya Pradesh and Rajasthan states in India, the soil analyses of farmers’ fields revealed widespread deficiencies of S (9–96%), B (17–100%) and Zn (22–97%) along with that of P (25–92%). Soil organic C was deficient in 7–84% fields indicating specifically N deficiencies and poor soil health in general. During on-farm evaluations in rainy seasons 2010 and 2011, the soil test based addition of deficient nutrient fertilizers as balanced nutrition (BN) increased crop yields by 6–40% (benefit to cost ratios of 0.81–4.28) through enhanced rainwater use efficiency. The integrated nutrient management (INM), however, decreased the use of chemical fertilizers in BN by up to 50% through on-farm produced vermicompost and recorded yields at par or more than BN with far better benefit to cost ratios (2.26–10.2). Soybean grain S and Zn contents improved with INM. Applied S, B, Zn and vermicompost showed residual benefits as increased crop yields for succeeding three seasons. Hence, results showed INM/BN was economically beneficial for producing more food, while leading to resilience building of SAT production systems.