Ameliorants and salt tolerant varieties improve rice-wheat production in soils undergoing sodification with alkali water irrigation in Indo -Gangetic Plains of India

This work evaluates the combine efficacy of chemical (gypsum, Gyp) and/or organic (pressmud, PM) amendments with salt-tolerant varieties (STVs) for ameliorating the deleterious effects of bicarbonate dominated residual alkalinity in irrigation water (RSCiw) on changes in soil properties, plant adaptation mechanisms and crop performance of rice-wheat system (RWS) in Trans Indo-Gangetic Plains. Continuous irrigation with high RSCiw gradually increased the soil pH and exchangeable sodium percentage (ESP) and reduced rice and wheat productivity by 16 and 14%, respectively. Use of Gyp and PM ameliorated RSCiw improved physiological traits of both crops under stress conditions through significant improvement in relative water content (RWC, 6 and 10%); photosynthetic efficiency (Pn, 40 and 36 %); stomatal conductance (gS, 46 and 52%); transpiration rate (E, 72 and 45%); chlorophyll fluorescence (Fv/Fm, 13 and 12%); photon quantum yield (YII, 12 and 6%) and reduced membrane injury index (MII, 23 and 17%) and ionic concentration of Na+/K+ in shoot (48 and 37%) and root (45 and 37%). Highest rice (3.42 t ha(-1)) and wheat (4.30 t ha(-1)) yields were realized with Gyp + PM ameliorated RSCiw elucidating-25% yield advantage compared to unamended control. With increased RSCiw, STVs of aromatic rice (CSR 30 Basmati) and wheat (KRL 210) exhibited better performance owing to lesser yield reduction (12 and 11%) compared to traditional rice (PB 1121; 18%) and wheat (HD 2967; 16%) varieties. This study suggests that growing of STVs with Gyp + PM ameliorated RSC waters can mitigate adverse effects of RSCiw on soil health, improve agro-physiological adaptation and sustain the productivity of RWS. Field applicability of PM as soil ameliorant can help to address its safer disposal vis-a-vis potential alternative to gypsum in long-run. These results can be extended to larger areas undergoing high RSCiw induced soil sodification, further mitigating land and environment degradation in salt affected areas of India and similar agro-ecosystems.

Automated summary

The study shows that the combined use of gypsum and pressmud can ameliorate the deleterious effects of residual alkalinity in irrigation water, leading to improved growth and productivity of rice and wheat crops, especially with salt-tolerant varieties.