Assessment and mitigation of soil water stress of rainfed lentil (Lens culinaries Medik) through sowing time, tillage and potassic fertilization disparities

In the Indian subcontinent, lentil (Lens culinaries Medik) is cultivated mainly on carry-over residual soil water and nutrients in rainfed rice (Oryza sativa L.)-fallows, coinciding with increasing temperatures during the reproductive period, thus limiting seed yield. A field experiment was conducted in rice fallows with the main plots of two dates of sowing of lentil (early and late) after short and long-duration puddled rice, the sub-plots of three tillage practices after puddled rice viz. no-tillage (NT), minimum tillage (MT) and conventional tillage (CT) with varying rice residues and the sub-sub-plots with four K fertilizer management viz. no K (K0) i.e. control, K as basal (Kb), K as foliar (Kf) and K both as basal and foliar (Kb+f) on an Aeric Haplaquept, clay loam soil of Lower Gangetic Plain during 2016–2017 and 2017–2018 cropping seasons. The objective of the study was to explore the extent of abiotic stresses vis-à-vis study of the effectiveness of the sowing time, tillage and K in mitigation of these stress through reconnoitering the plants rooting behavior, morpho-physiological and biochemical responses reflecting yield and water productivity under the above management practices. Plots with the early sown lentil stored significantly (P < 0.05) 29 % and 17 % higher root zone (0–40 cm) soil water than late sown crops, while NT and MT stored a higher amount of soil water as compared to CT and the CT experienced the intensified stress accounting for 61 % and 74 % during the flowering and pod formation periods. Late sown lentil and NT treatments possessed higher bulk density (BD) of 1.52 and 1.55 Mg m−3 and penetration resistance (PR) of 2.51 MPa than early sown lentil and NT. Root zone soil water storage was significantly and positively correlated with leaf area index (R2 = 0.29; P < 0.05) and relative water content of leaves (R2 = 0.43; P < 0.01). Root growth was also heavily affected by these treatments. Though root length density (RLD), root surface area (RSA), mean root diameter (MRD), root volume (RV), the total number of root tips (TRT) and the total number of root forks (TRF) were improved at early growth of CT, MT produced maximum roots at reproductive stages of lentil. The abundance of soil water increased finer roots, whereas the unavailability of soil water produced coarser roots (> 1.0 mm). Kbf performed the best physiological activity (RWC, LAI, RLD, RSA, RV etc.) followed by Kb. Seasonal evapotranspiration (ETa) was observed 104, 97 and 86.5 mm under early sown NT, MT and CT, and both Kbf and Kb accounted for 89.5 mm of ETa. In respect to the maximum grain yield (14.23 q ha−1) vis-a-vis water productivity (13.15 kg ha−1 mm−1), and the highest improvement of lentil yield by 1.40 q ha−1 with each of 10 mm increment of ETa under early sown lentil at minimum tillage condition managed with K fertilizer as basal and foliar proved to be the best treatment in successful mitigation of abiotic stresses.