Crop yields and soil organic matter pools in zero-till direct-seeded rice-based cropping systems as influenced by fertigation levels in the Indo-Gangetic plains in India

Fertigation in rice-based cropping systems is catching up the attention of farmers for producing high yield of crops and improved fertilizer use efficiency. As fertigation with different combinations of irrigation and nitrogen (N) levels can interact with depth of rooting system of different crops as well as soil tillage, this study was carried out in 2017 in the fourth year of on an on-going long-term experiment initiated in the summer (Kharif) season of 2014 to understand the effect of fertigation on soil organic carbon pools and yield in zero-till direct-seeded rice-based cropping systems. The experiment was laid out in a split plot design with three levels of fertigation as main plots: N @ 20 kg ha(-1) in rice through fertigation followed by 200 mm irrigation in post rice crops (W-1), N @ 40 kg ha(-1,) in rice through fertigation followed by 300 mm irrigation in post rice crops (W-2), N @ 60 kg ha(-1,) in rice through fertigation followed by 400 mm irrigation in post rice crops (W-3). The sub-plot treatments consisted of zero till direct seeded durum wheat, barley, chickpea, linseed, lentil and lathyrus crops after rice. The rice crop was also under zero till direct seeded cultivation system. The highest grain yield of rice was observed in the rice-lathyrus cropping system with treatment W-3 where N was applied in three equal splits, first being basal application and the two subsequent applications through surface inline drip irrigation. Both in surface and sub-surface soil layers, soil carbon stock, carbon pools and aggregate associated carbon were found to be more in the legume based cropping systems and with W-3 fertigation regime than in other cereal based cropping systems. The grain yield was found negatively and highly significantly correlated with less labile pool (r=-0.63**) whereas very labile pool was positively significantly correlated with labile (r = 0.89**), less labile (r = 0.53**) and non-labile (r = 0.91**) pools of carbon. Overall, fertigation levels influenced the crop yield and soil organic matter in zero-till direct-seeded rice-based cropping systems.