Ajmer Singh Brar

The over‐exploitation of groundwater in agriculture necessitates the adoption of water‐efficient practices. A field study (2020–2022) under cotton–wheat cropping in semi‐arid Punjab, India, evaluated subsurface drip irrigation (SSDI) with lateral depths (20, 25 and 30 cm), emitter spacings (20, 30 and 40 cm) and irrigation levels (60%, 80% and 100% ETc). Bayesian optimization was used for multicriteria decision‐making. The results revealed wheat sensitivity to lateral depth, with a significant yield reduction at 30 cm compared to 20 cm, whereas the deep root system of cotton mitigated such effects. Overall, SSDI at 80% ETc maintained system productivity (SP; 4343 kg ha ⁻¹ ) and net returns (NR; 2001.1 $ ha ⁻¹ ) comparable to full irrigation, in addition to 20% higher irrigation water productivity (WP). Additionally, it also resulted in 5%, 11%, 5% and 23% greater SP, NR, irrigation and net economic WP, respectively, than the recommended surface drip practice. Furthermore, multiresponse optimization identified 25.5‐cm lateral depth, 31.2‐cm emitter spacing and irrigation at 81% ETc as the optimum combination for SSDI. This configuration optimized productivity, water saving and profitability within permissible drainage losses (RMSE 0.4223). These findings not only underscore the resource conservation potential of SSDI but also demonstrate its capacity to maximize economic and environmental benefits.

Increasing water scarcity and nutrient demand requires efficient irrigation and nutrient management for sustaining the productivity of the basmati rice–wheat cropping system. This study assessed the impacts of two irrigation methods (surface [DI] and subsurface drip irrigation [SDI]), four irrigation schedules (I _15% , I _25% , I _35% and I _45% , i.e., 15%, 25%, 35% and 45% depletion of available water) and two nitrogen doses (100% and 75% of the recommended dose), in comparison with the control (flood irrigation with a 100% recommended dose of nitrogen). Compared with the control, the SDI N ₁₀₀ I _15% , SDI N ₁₀₀ I _25% , DI N ₁₀₀ I _15% and DI N ₁₀₀ I _25% achieved statistically comparable grain yield and yield attributes, with higher water productivity by 10%, 12%, 6% and 9% (pooled from 2021 to 2022 and 2022 to 2023) and irrigation water savings of 185, 255, 145 and 220 mm, respectively, in wheat and basmati rice from 2021 to 2022 and 225, 300, 175 and 265 mm, respectively, in wheat and basmati rice from 2022 to 2023. Furthermore, the highest economic water productivity was recorded in the SDI N ₁₀₀ I _15% treatment (17.03 INR m ⁻³ pooled) over the control (16.61 INR m ⁻³ pooled) in the basmati rice–heat system. These findings highlight the potential of precision irrigation strategies in enhancing water productivity without compromising yield in the basmati rice–wheat system.

Although, crop productivity is determined by several factors like photo-period, moisture and fertility, but it is primarily influenced by temperature. Increasing water scarcity due to high evapo-transpiration is a major concern for crop production. Therefore, a field experiment was planned to evaluate the response of varied irrigation and fertilization levels on agrometeorological indices of cotton-wheat cropping system at the Research Farm, Department of Soil Science, Punjab Agricultural University, Ludhiana for two consecutive years i.e. 2019-2020 and 2020-2021. Higher heat indices were resulted from longer phenophases under well fertilized and watered conditions. Cotton irrigated through subsurface drip at 100% ET_c along with100% RDN and foliar application of nutrients i.e. 2% KNO₃ (4 times) & 1% MgSO₄ (2 times) exhibited higher heat indices i.e. growing degree days, helio-thermal units, photo-thermal units, relative temperature disparity and heat use efficiency over all other treatments, to reach maturity. On the other hand, wheat crop that received 100% irrigation through sub-surface drip irrigation and fertilization along with the residual effect of equivalent quantity of soil applied 2% KNO₃ and 1% MgSO₄, to cotton experienced higher heat indices than to other treatments.

Response of wheat to sowing dates and irrigation regimes was studied at Punjab Agricultural University, Ludhiana during Rabi 2016–17 and 2017–18 for assessing phenological development, heat unit accumulation and their cumulative effect on wheat yield. Both sowing dates and irrigation regimes have marked influence on number of days taken to attain various phenological stages, heat unit accumulation viz., growing degree days (GDD), helio-thermal (HTU) and photothermal (PTU) units in pooled analysis. Wheat sown on 25^th October took maximum calendar days to attain various phenophases starting from tillering to maturity and accumulated highest GDD, HTU and PTU, which further gets reduced with subsequent delay in sowing time. October 25^th sown wheat also resulted in maximum grain yield (5456+631 kg ha⁻¹), which was non-significant with 5^th November but significantly higher than 15^th and 25^th November sowing. Among irrigation regimes, crop irrigated at 1.25 IW:CPE exhibited highest GDD, HTU, PTU and resulted in maximum grain yield. Thus, wheat sown on October 25 and irrigated at 1.25 IW:CPE was found to be the most efficient in terms of highest grain yield and maximum thermal use efficiencies.