Assessing the availability of potassium and its quantity-intensity relations under long term conservation agriculture based cereal systems in North-West India

Potassium fertilization is often neglected and /or ignored leading to imbalanced fertilization under intensive cultivation especially in the Indo Gangetic Plains (IGP) in North-West India. Recently conservation agriculture (CA) with crop residue retention has become quite popular among the farmers and land practitioners in India and globally. Crop residues are generally rich in potassium (K) content and its continuous addition under CA may impact K dynamics and supply to crops to some extent. Keeping this in view, a field experiment was conducted to assess the effect of long-term cereal-based CA on K supplying capacity in soil of North-West India. Both routine method (neutral normal ammonium acetate extractable) and quantity-intensity (Q/I) approach were adopted to predict K supply under CA vis-`a-vis conventional agriculture. Available K and Q/I parameters were analyzed after 11 years of an experimental setup consisting of six scenarios i.e. Scenario 1 (Sc1): conventional till rice-wheat cropping system; Scenario 2 (Sc2): partial CA based rice-wheat-mungbean system; Scenario 3 (Sc3): full CA based rice-wheat-mungbean system; Scenario 4 (Sc4): full CA based maize-wheat-mungbean system; Scenario 5 (Sc5) and 6 (Sc6): same as Sc3 and Sc4 but with sub surface drip irrigation system. Results revealed that full CA based scenarios maintained significantly higher (p < 0.05) available K (145 mg kg-1) than Sc1 (86 mg kg-1). However, it was observed that Q/I approach helped in better understanding of K supply under long term CA soils than routine method. Regarding K availability, Sc6 was the best scenario with high values of planar K (0.147 cmol kg-1), labile K (0.325 cmol kg-1) and potential buffering capacity (PBCK) while Sc1 (without K fertilization or residue addition) presented lowest values of Q/I parameters. Partial CA (Sc2) maintained higher labile K (0.368 cmol kg-1) and equilibrium concentration ratio (CRe0K) (1.93(mol L-1) 1/2 x 10-3) but very low PBCK (36.4 cmol kg-1 (mol L-1)-1/2) suggesting that K intensity shall not be sustained for long period of time and lead to soil K depletion over time. However, on an average, all full CA based scenarios maintained higher Q/I pa-rameters over the conventional practice (Sc1), representing better ability to supply K both immediately and over a long period of time to meet crop requirement. The impact of maize-wheat-mungbean cropping system was prominently observed with respect to CRe0Kover rice-wheat-mungbean system; whereas the effect of irrigation method was not significantly distinguishable. The study thus highlights the potential of long term crop residue retention under CA for improving and maintaining K supply to crops.

Automated summary

Potassium fertilization is often overlooked in intensive cultivation, leading to imbalanced fertilization. Conservation agriculture with crop residue retention has become popular in India and globally, which may impact potassium dynamics and supply to crops. A field experiment was conducted to assess the effect of long-term cereal-based conservation agriculture on potassium supplying capacity in soil. Results showed that full conservation agriculture scenarios maintained significantly higher available potassium compared to conventional practice. The study highlights the potential of long-term crop residue retention under conservation agriculture for improving and maintaining potassium supply to crops.