S.L. Jat

Selection indices to identify maize (Zea mays L.) hybrids adapted under drought-stress and drought-free conditions in a tropical climate

Abstract. Drought stress is the most important production constraint in maize (Zea mays L.), especially in rainfed agriculture. To improve productivity of rainfed maize, the development of hybrids with tolerance to drought stress is an important objective in maize breeding programs. The present study was undertaken to identify maize hybrids that perform better under drought-stress and drought-free conditions by using various selection indices. These selection indices were calculated on the basis of yield (t ha–1) performance of hybrids measured under drought stress and optimum environments. A set of 38 cultivars was evaluated at 10 environments (representing five each of drought stress and optimum growing conditions). The average reduction in grain yield due to drought stress was 52%. Effects of genotype, environment and their interaction were significant sources of variation in determining grain yield, respectively explaining 5.0–7.4%, 55.0–60.2% and 12.0–15.0% of total variation in yield under drought-stress and drought-free conditions. Of eight selection indices considered for study, three indices such as harmonic mean, geometric mean, and stress tolerance index were identified as suitable for selection of genotypes capable of performing well both under drought-stress and drought-free environments. Drought response index and drought resistance index were found useful in identifying hybrids that performed better under drought stress. Stress susceptibility index was negatively correlated with yield measured under drought stress. Stress susceptibility index could be used as selection index but only in combination with yield performance data under water-deficit conditions in order to identify drought-tolerant hybrids with reasonable productivity. Test weight, shelling percentage, days to maturity, and ear girth were found to be useful traits for improving yield performance across diverse environments. Cultivation of identified drought-tolerant hybrids would be useful to enhance maize productivity in drought-stress environments.

Changes in carbon pools and biological activities of a sandy loam soil under medium-term conservation agriculture and diversified cropping systems: Soil health under conservation agriculture

SUMMARY: Conservation agriculture (CA) practices such as zero tillage (ZT) and permanent raised beds (PB) accelerate deposition of soil organic matter and augment associated biological properties of soil through enhanced inputs of organic carbon. However, the potential benefit of CA under intensive cereal‐based systems for key soil health indicators (such as carbon pools and biological activities) is only partially known. Therefore, we analysed the effect of three medium‐term tillage practices and four intensive crop rotations on selected soil organic carbon pools and microbial properties. The tillage practices consist of ZT, PB and conventional tillage (CT) in main plots and four crop rotations (MWMb, maize–wheat–mungbean; MCS, maize–chickpea–Sesbania; MMuMb, maize–mustard–mungbean; MMS, maize–maize–Sesbania) in subplots. The experimental design was split‐plot with three replications. After 6 years, we observed a significant positive effect of CA practices on soil organic carbon (SOC) content, labile SOC fractions, soil microbial biomass carbon (MBC) and dehydrogenase activity (DHA). The total organic carbon (TOC) was greatly affected by medium‐term tillage and diversified cropping systems; it was larger for CA and MCS and MWMb systems. The interaction effect between tillage and cropping systems for SOC content was not significant at all soil depths. Significantly larger contributions (8.5–25.5%) of labile SOC pools to TOC at various soil depths were recorded in PB and ZT. There was a significant positive effect of CA practices and diversified crop rotations on MBC and DHA at all the soil depths and sampling times, but the interaction effect between tillage and cropping systems was not significant. Thus, our medium‐term (≥ 5‐years) study showed that the combination of CA (PB and ZT) practices and appropriate choice of rotations (MCS and MWMb) appears to be the most appropriate option for restoration and improvement of the soil health of light‐textured Inceptisols through the accumulation of soil organic matter (SOM) and improvement in soil biological properties. HIGHLIGHTS: Effect of conservation agriculture (CA) on soil labile carbon inputs and biological properties. Observed changes in SOC stock and C‐pools at different soil depths after 6 years. Significant effects of tillage and crop rotations observed for labile‐C pools. Adoption of ZT and PB enhanced SOC stock, C‐pools and microbial activity compared to CT.

Long Term Conservation Agriculture and Intensified Cropping Systems: Effect on Growth, Yield, Water and Energy-use Efficiency of Maize in North-Western India

Abstract Conservation agriculture (CA) based best-bet crop management practices may increase crop and water productivity, while conserving and sustaining natural resources. Therefore, we evaluated kharif maize performance in 2014 under long-term tillage practices [permanent bed (PB) and zero tillage (ZT)] with conventional till (CT) as main plots and four irrigated maize based systems [maize-wheat-mungbean (MWMb), maize-chickpea- Sesbania (MCS), maize-mustard-mungbean (MMuMb) and maize-maize- Sesbania (MMS)] in sub plots under an ongoing trial established in 2008. In seventh kharif season at fixed plots the growth parameters, yield attributes, yield, water and energy-use efficiency of maize was maximum in ZT plots. The maize growth parameters were significantly ( p ) superior under ZT and PB compared to CT plots. Maize yield attributes viz. cobs m −2 (7.8), cob length (0.183 m), grain rows cob −1 (13.8) and grains row −1 (35.6) were significantly higher in ZT over to CT, however no-significant effect of cropping systems was found on maize growth and yield attributes. ZT registered maximum maize productivity (4589 kg ha −1 ). However, among the cropping sequences, MCS registered highest maize productivity (4582 kg ha −1 ). In maize, the water-use was reduced by 80.2-120.9 mm ha −1 in ZT and PB plots compared to CT which ultimately enhanced the water-use efficiency by 42.0 and 36.6%, respectively. ZT and PB plots registered increased soil organic carbon (SOC) by 3.5-31.8% in different depths (0-0.45 m) and energy productivity by 32.3-39.9% compared with CT. Overall, our long-term results showed that CA based ZT and PB practices coupled with diversified maize based cropping systems found effective for enhancing the maize yield, soil organic carbon, water and energy-use efficiency in North-Western India.

Specialty Corn for Nutritional Security and Dietary Diversification

Maize contributes more than half of the coarse cereal production in India. The grain is used for various purposes like feed, food, and several industrial purposes. It has tremendous potential to feed millions of hungry people of the African and Latin American countries as 5 % of world’s dietary energy supply comes from maize. In addition, maize has been considered as industrial crop as it is being used as a raw material in many important industries, viz., starch, oil, alcoholic beverages, food sweeteners, pharmaceuticals, cosmetics, textile, paper, film, tire, food processing, packing, biofuel, etc. for developing hundreds of industrial products. Apart from these, quality protein maize (QPM) is being grown to meet the nutritional requirement of underprivileged. Besides these uses, sweet corn (SC) and baby corn (BC) are used for ensuring livelihood and green fodder security in peri-urban areas while popcorn (PC) is used as a nutritional alternative snack, etc.