Lysimetric and eddy covariance techniques are commonly used to directly estimate actual crop evapotranspiration ($E{T}_a$). However, these technologies are costly, laborious, and require skills which make in situ ET estimation difficult, particularly in developing countries. With this in mind, an attempt was made to determine $E{T}_a$ and stagewise crop coefficient (K_c) values of transplanted puddled rice using a modified non-weighing paddy lysimeter. The results were compared to indirect methods, viz., FAO Penman–Monteith and pan evaporation. Daily $E{T}_a$ ranged from 1.9 to 8.2 mmday⁻¹, with a mean of 4.02 ± 1.35 mmday⁻¹, and their comparison showed that the FAO Penman–Monteith equation performed well for the coefficient of determination (R² of 0.63), root mean squared error (RMSE = 0.80), and mean absolute percentage error (MAPE = 13.6 %), and was highly correlated with $E{T}_a$ throughout the crop season. However, the pan evaporation approach was underestimated (R² of 0.24; RMSE = 0.98; MAPE = 22.13%) due to a consistent pan coefficient value (0.71), vegetation role and measurement errors. In addition, actual K_c values were obtained as 1.13 ± 0.13, 1.27 ± 0.2, 1.23 ± 0.16, and 0.93 ± 0.18 for the initial, crop development, mid-season, and end-season stages, respectively. These estimated crop coefficient values were higher than FAO K_c values. Statistical analysis results revealed that the overall stagewise-derived average K_c values were in line with FAO values, but different from the derived pan K_c values, although found insignificant at a 5% significance level. In addition, water productivity and agro-meteorological indices were derived to evaluate the cultivar performance in this experiment. Therefore, such a methodology may be used in the absence of weighing lysimeter-derived K_c values. The derived regional K_c values can be applied to improve irrigation scheduling under similar agro-climatic conditions.

Rice-fallow systems in South Asian countries play a pivotal role in increasing agricultural production. However, the productivity of these system is largely challenged by deteriorating soil health and limited residual soil moistures in dry-periods, precluding the possibility of winter and/or spring season crops after rice harvest. This investigation explores the possibilities of including winter and/or spring crops through conservation agriculture (CA)-based management practices and evaluates its effect on soil carbon dynamic, system productivity, energy and carbon budgeting. Field experiments were conducted at a farmer’s field in participatory modes at Chene Village, Jharkhand, India, and had five treatments comprising (1) fallow-land [FL]; (2) transplanted puddle rice (TPR)-fallow (winter)-fallow (summer), a typical cultivation practice of this region [RF]; (3) TPR–conventional-till mustard–conventional-till blackgram [CP]; (4) CA with zero-till transplanted rice (ZTTR)-ZT mustard–ZT blackgram [CA1]; (5) CA with zero-till direct seeded rice (ZTDSR)-ZT mustard–ZT blackgram [CA2]. Results revealed that CA2 comprising full CA practice of growing direct seeded rice, mustard and blackgram under ZT increased total soil organic carbon (TSOC) of 0–0.6 m soil layer by 14.3% and 10.3% over RF and CP, respectively. The C-sequestration rate was higher in CA treatments and varied from 0.55 to 0.64 Mg C ha⁻¹ year⁻¹. The system rice equivalent yield in CA2 during the initial four years was lower than CP but it was 23.7% higher over CP in fifth year. The CA-based system (CA2) enhanced the water productivity of rice, mustard and blackgram by 7.0%, 23.6% and 14.1% over CP, respectively. The CA2 treatment, having higher system productivity, better C-sequestration potential, lower C-footprint, higher energy and water productivity has very good potential for sustaining soil health and crop yield of rice-fallow systems.

Climate-smart agriculture (CSA) practices are becoming increasingly important due to their better adaptability to harsh climatic conditions (in general) and the unpredictability of monsoons in India (in particular). Conventional rice cultivation (e.g., PTR) involves intensive tilling followed by intensive puddling in standing water that destroys the soil aggregation and depletes carbon pools. Therefore, alternative crop establishment methods need to be devised for the sustainability of system productivity, and the suitabilities of potential oilseeds and pulses need to be tested for cropping intensification in rice-fallow regions. Hence, an ongoing experiment (implemented in 2016) was evaluated to identify the appropriate CSA management practices in restoring soil C and physical health under diversified cropping systems in the rice-fallow system of eastern India. Six tillage and crop establishment methods along with residue management were kept as the main plots [zero-till-direct-seeded rice (ZTDSR), conventional-till-DSR (CT-DSR), puddled transplanted rice (PTR), ZTDSR with rice residue retentions (ZTDSR_R+), CTDSR with rice residue retention (CTDSR_R+), PTR with rice residue retention (PTR_R+)] while five winter/post-rainy crops (oilseeds and pulses) were raised in a subplot. In the ZTDSR_R+ production system, soil macro-aggregate (%), macro-aggregate-associated C, MWD, and GMD of aggregates increased by 60.1, 71.3, 42.1, and 17.1%, respectively, in comparison to conventional tillage practices (PTR). The carbon management index (CMI) was 58% more in the ZTDSR_R+ production system compared to PTR. Among the winter crops, chickpeas recorded higher values of soil structural indices and C content. In the PTR production system, system productivity, in terms of rice equivalent yield, was comparable to ZTDSR_R+. ZT with residue retention in rice followed by post-rainy/winter pulses led to higher C content and structural stability of the soil. Thus, CSA management practices can improve the crop productivity as well as soil health of rice-fallow production systems of eastern India and comparable agroecotypes of South Asia.