Multi-location evaluation of field pea in Indian climates: eco-phenological dynamics, crop-environment relationships, and identification of mega-environments.

Characterization of crop-growing environments in relation to crop's genotypic performance is crucial to harness positive genotype-by-environment interactions (GEI) in systematic breeding programs. Given that, the study aimed to delineate the impact of diverse environments on crop phenology and yield traits of dwarf-statured field pea, pinpointing location(s) favoring higher yield and distinctiveness within breeding lines. We tested twelve field pea breeding lines across twenty locations in India, covering Central Zone (CZ), North Western Plain Zone (NWPZ), North Eastern Plain Zone (NEPZ), and Northern Hill Zone (NHZ). Across these locations, maximum and minimum temperatures during flowering (TMAXF, TMINF) and reproductive period (TMAXRP, TMINRP) ranged 18.9-28.3, 3.3-18.0, 15.0-30.8, and 7.9-22.1oC, respectively. Meanwhile, notable variations in phenological and agronomic traits (coefficient of variation) were observed: flowering (31%), days to maturity (21%), reproductive period (18%), grain yield (48%), and 100-seed weight (18%). Combined ANOVA demonstrated an oversized impact of environment (81%) on yield, while genotype and GEI effects were 2% and 14%, respectively. The variables TMINF, TMINRP, and cumulative growing degree-day showed positive correlations with yield, while extended vegetative and maturity durations negatively influenced yield (p < 0.05). Additionally, linear mixed-models and PCA results explained that instability in crop phenology had significant influence on field pea yield. Seed weight was markedly varied within the locations (9.9-20.8 g) and both higher and lower seed weights were associated with lower yields (Optimal = 17.1 g). HA-GGE biplot-based on environment focus-scaling demonstrated three mega-environments and specific locations viz. Kota (CZ), SK Nagar (CZ), Raipur (CZ), Sehore (CZ), and Pantnagar (NWPZ) as the ideal testing-environments with high efficiency in selecting new genotypes with wider adaptability. The study findings highlight distinct impact of environments on crop phenology and agronomic traits of field pea (dwarf-type), hold substantial value in designing efficient field pea (dwarf-type) breeding program at mega-environment scale.

Delineating the role of plant stature towards heat stress tolerance in field pea (Pisum sativum L.).

Terminal heat stress severely affects field pea production in tropical climates. Identifying and characterizing marker-trait(s) remain vital for breeding heat-tolerant cultivars of field pea. Field pea genotypes are highly variable for plant stature; however, the significance of plant stature for yield stability under high-temperature conditions is not yet well understood. The study aimed to investigate the sensitivity and significance of plant stature toward yield sustainability of field pea under high-temperature environments. A panel of 150 diverse genotypes with variable plant statures [dwarf (<50 cm), semi-dwarf (50-80 cm), medium-tall (80-150 cm)] were grown under late sowing-induced high-temperature environments for two consecutive years (2017-2019). During the first year of the experiment, the late sown crops (15 and 30 days) were exposed to high-temperatures at flowering (+3.5 to +8.1 °C) and grain-filling (+3.3 to +6.1 °C) over timely sown crops. Likewise, elevated temperature during flowering (+3.7 to +5.2 °C) and grain filling (+5.4 to +9.9 °C) were recorded in late-sown environments (delayed by 27 and 54 days) in the next year. Medium-tall genotypes had longer grain-filling duration (7-10%), higher pod-bearing nodes (8-18%) and yield (22-55%), and lower yield losses (13-18%) over semi-dwarf and dwarf genotypes under high-temperature environments. Significant associations of plant height with yield, yield loss, and heat-susceptibility index in high-temperature environments suggested higher heat tolerance capacity of tall-type plants compared to dwarf and semi-dwarf types. GGEbiplot analysis revealed that the heat-tolerant genotypes were all medium tall-type (mean = 108 cm), while the heat-susceptible genotypes were mostly dwarf in stature. Hence, tall-type genotypes had better adaptability to high-temperature environments. Henceforth, the breeding approach for high-temperature tolerance in field pea may be designed by embracing tall-type backgrounds over dwarf plant to develop climate resilient cultivars.

Potential of conservation agriculture modules for energy conservation and sustainability of rice-based production systems of Indo-Gangetic Plain region.

Rice-based cropping systems are the most energy-intensive production systems in South Asia. Sustainability of the rice-based cropping systems is nowadays questioned with declining natural resource base, soil degradation, environmental pollution, and declining factor productivity. As a consequence, the search for energy and resource conservation agro-techniques is increasing for sustainable and cleaner production. Conservation agriculture (CA) practices have been recommended for resource conservation, soil health restoration and sustaining crop productivity. The present study aimed to assess the different CA modules in rice-based cropping systems for energy conservation, energy productivity, and to define energy-economic relations. A field experiment consisted of four different tillage-based crop establishment practices (puddled-transplanted rice followed by (fb) conventional-till maize/wheat (CTTPR-CT), non-puddled transplanted rice fb zero-till maize/wheat (NPTPR-ZT), zero-till transplanted rice fb zero-till maize/wheat (ZTTPR-ZT), zero-till direct-seeded rice fb zero-till maize/wheat (ZTDSR-ZT)), with two residue management treatments (residue removal, residue retention) in rice-wheat and rice-maize rotations were evaluated for energy budgeting and energy-economic relations. Conservation-tillage treatments (NPTPR-ZT, ZTTPR-ZT, and ZTDSR-ZT) reduced the energy requirements over conventional tillage treatments, with the greater reduction in ZTTPR-ZT and ZTDSR-ZT treatments. Savings of energy in conservation-tillage treatments were attributed to reduced energy use in land preparation (69-100%) and irrigation (23-27%), which consumed a large amount of fuel energy. Conservation-tillage treatments increased grain and straw/stover yields of crops, eventually increased the output energy (6-16%), net energy (14-26%), energy ratio (25-33%), and energy productivity (23-34%) as compared with CTTPR-CT. For these energy parameters, the treatment order was ZTDSR-ZT ≥ ZTTPR-ZT > NPTPR-ZT > CTTPR-CT (p < 0.05). Crop residue retention reduced net energy, energy ratio, and energy productivity when compared with residue removal. Our results of energy-economic relations favored the "conservative hypothesis," which envisages that energy and monetary investments are not essentially the determinants of crop productivity. Thus, zero tillage-based crop establishments (ZTTPR-ZT, ZTDSR-ZT) in rice-based production systems could be the sustainable alternative to conventional tillage-based agriculture (CTTPR-CT) as they conserved non-renewable energy sources, reduced water requirement, and increased crop productivity.

Crop rotation and tillage management options for sustainable intensification of rice-fallow agro-ecosystem in eastern India.

Presently, rice-fallows are targeted for cropping intensification in South Asia. Rice-fallows a rainfed mono-cropping system remain fallow after rice due to lack of irrigation facilities and poor socio-economic condition of the farmers. Nevertheless, there is the scope of including ecologically adaptable winter crops in water-limited rice-fallow conditions with effective moisture conservation practices. The study aimed to identify the winter-crops that are adaptable and productive in rice-fallow conditions and to evaluate the different tillage-based crop establishment practices for soil moisture conservation, grain yield, economics, and sustainability parameters. Six different crop establishment and residue management (CERM) practices viz., zero-tillage direct seeded rice (ZTDSR), zero-tillage transplanted rice (ZTTPR), puddled transplanted rice (PTR), ZTDSR with rice residue retention (ZTDSRR+), ZTTPR with rice residue retention (ZTTPRR+), PTR with rice residue retention (PTRR+) as main-plot treatment and five winter crops (chickpea, lentil, safflower, linseed, and mustard) as sub-plot treatment were evaluated in a split-plot design. The productivity of grain legumes (chickpea and lentil) was higher over oilseed crops in rice-fallow conditions with an order of chickpea > lentil > safflower > mustard > linseed. Among the CERM practices, ZTDSRR+ and ZTDSR treatments increased the grain yield of all the winter crops over PTR treatment, which was primarily attributed to higher soil moisture retention for an extended period. Grain yield increment with conservation tillage practices was highly prominent in safflower (190%) followed by lentil (93%) and chickpea (70%). Rice grain yield was higher (7-35%) under PTR treatment followed by ZTDSR treatment. Conservation tillage practices (ZTDSR, ZTTPR) reduced energy use (11-20%) and increased the energy ratio over conventional tillage practice (PTR), higher in rice-safflower, rice-lentil and rice-chickpea rotations. Higher net return was attained in rice-safflower and rice-chickpea rotations with ZTDSRR+ treatment. Predicted emission of greenhouse gases was markedly reduced in ZTDSR treatment (30%) compared to ZTTPR and PTR treatments. Hence, the study suggests that cropping intensification of rice-fallows with the inclusion of winter crops like chickpea, lentil, and safflower following conservation tillage practices (ZTDSRR+ in particular) could be the strategic options for achieving the higher system productivity, economic returns, and energy use efficiency with the reduced emission of greenhouse gases.

Sustainable intensification of rice fallows of Eastern India with suitable winter crop and appropriate crop establishment technique.

Rice fallow, a rainfed lowland agro-ecology, is presently gaining particular attention for sustainable cropping intensification in the South Asia. Nevertheless, cropping intensification of rice-fallow areas is largely challenged by non-availability of irrigation, the poor financial status of farmers and soil constraints. Indeed, fast depletion of the soil residual moisture remains the primary obstacle for growing a crop in succession in rice fallows. A field investigation was carried out to identify the most adaptable rice-winter crop rotation and to customize appropriate crop establishment practice for a winter crop that could conserve the soil moisture. Treatments comprised of three crop establishment practices for winter crops [utera (relay cropping, i.e. broadcasting of seeds in standing rice crop 15 days before harvesting), zero tillage (ZT) and ZT with mulching (ZTM)], and five post-rainy-season crops (lentil, chickpea, lathyrus, mustard and linseed). Results showed that lathyrus and lentil could be the potential winter crop in the rice-fallow condition of Eastern India. Except for mustard crop, the productivity of all the winter crops was higher in utera cropping, which was primarily attributed to early crop growth and higher soil moisture content over ZT and ZTM treatments. The higher water use efficiency was recorded under utera cropping over ZT and ZTM treatments. Higher system productivity (system rice equivalent yield) in rice-utera lathyrus (9.3 t ha-1) and rice-utera lentil (8.1 t ha-1) led to higher net returns and production efficiency over other treatments (winter crop × crop establishment practice). Benefits of rice residue mulching were prominent in lentil, mustard and linseed crop productivity. Energy use efficiency of different crop establishment practices follows the trend of utera > ZT > ZTM (p < 0.05), being highest in rice-utera lathyrus (5.3) followed by rice-utera lentil (4.8) crop rotations. The simulated data shows that winter crops grown under utera led to less emission of greenhouse gas (GHG) and low global warming potential (GWP) as compared to ZT and ZTM treatments. Rice-lathyrus, rice-lentil and rice-chickpea systems had lower N2O emission than rice-mustard and rice-linseed rotations. Hence, lathyrus and lentil could be included in rice fallows ideally with utera for sustainable cropping intensification and improving the farmers' income in Eastern India.

Impact of conservation tillage in rice-based cropping systems on soil aggregation, carbon pools and nutrients.

Tillage intensive cropping practices have deteriorated soil physical quality and decreased soil organic carbon (SOC) levels in rice-growing areas of South Asia. Consequently, crop productivity has declined over the years demonstrating the need for sustainable alternatives. Given that, a field experiment was conducted for six years to assess the impact of four tillage based crop establishment treatments [puddled transplant rice followed by conventional tillage in wheat/maize (CTTPR-CT), non-puddled transplant rice followed by zero-tillage in wheat/maize (NPTPR-ZT), zero-till transplant rice followed by zero-tillage in wheat/maize (ZTTPR-ZT), zero-tillage direct seeded rice followed by zero-tillage in wheat/maize (ZTDSR-ZT)], two residue management treatments [residue removal, residue retention (~33%)], and two cropping systems [rice-wheat, rice-maize] on soil aggregation, carbon pools, nutrient availability, and crop productivity. After six years of rotation, in top 0.2 m soil depth, zero-till crop establishment treatments (ZTTPR-ZT and ZTDSR-ZT) had higher (p < 0.05) total organic carbon (TOC) over conventional tillage treatment (CTTPR-CT). Zero-till crop establishment treatments increased very-labile C faction (Cfrac 1) by 21% followed by labile fraction (Cfrac 2) (16%), non-labile fraction (Cfrac 4) (13%) and less-labile fraction (Cfrac 3) (7%). Notably, higher passive C-pool in conservation tillage practices over CTTPR-CT suggests that conservation tillage could stabilize the recalcitrant form of carbon that persists longer in the soil. Meantime, zero-till crop establishment treatments had higher (p < 0.05) water stable macro-aggregates, macro-aggregates: micro-aggregates ratio and aggregate carbon content over CTTPR-CT. The treatment NPTPR-ZT significantly increased soil quality parameters over CTTPR-CT. However, the effect was not as prominent as that of ZTTPR-ZT and ZTDSR-ZT. Retention of crop residue increased (p < 0.05) TOC (12%) and soil available nutrients mainly available-P (16%), followed by available-K (12%), DTPA-extractable Zn (11%), and available-S (6%) over residue removal treatment. The constructive changes in soil properties following conservation tillage and crop residue retention led to increased crop productivity over conventional CTTPR-CT. Therefore, conservation tillage (particularly ZTTPR-ZT and ZTDSR-ZT) and crop residue retention could be recommended in tropical rice-based cropping systems for improving soil quality and production sustainability.