Tillage, green manuring and crop residue management impacts on crop productivity, potassium use efficiency and potassium fractions under rice-wheat system.

The conventional crop production practices including intensive tillage and open field crop residue burning in world' largest rice-wheat system (RWS) are adversely affecting crop productivity besides deteriorating natural resources and ecosystems' sustainability. In order to improve system productivity, potassium (K) use efficiency and apparent K balance, adoption of conservation tillage in a RWS with residue management is considered highly effective. We therefore, studied the effect of wheat straw retention and green manure (GM) in rice (main plot treatment), and tillage and rice residue management in subsequent wheat (sub-plot treatments) on crop productivity, K use efficiency and its transformation amongst different fractions of variable solubility. These results revealed that rice straw retention along with GM significantly ( < 0.05) increased the rice yields by ∼5.3-6.7% and wheat yields by ∼10.2-16.9%, compared to the conventional tillage (CT) without GM. Green manuring during the intervening period (CTR+GM) significantly increased the rice grain K uptake by ∼36.2% than in plots with no-GM (CTR). However, it increased by ∼29.8% under CTR+GM, compared with CTR-GM treatment. As compared with CTR, CTR+GM significantly increased the reciprocal internal use efficiency of K of rice by 3.8 kg Mg grain yield (∼29.5%). However, CTR+GM increased the RIUE of rice by 3.3 kg Mg grain yield (∼22.4%), compared with no-GM (CTR). Although, apparent K balance was net negative for CTR, ZTW treatments, yet there was decreased K mining of 56-262 kg K ha (∼11.9-61.2%) for CTR and ZTW over CTR and ZTW. The increased crop yield, K uptake and K use efficiency were significantly related to K enrichment in water soluble K, exchangeable K, non-exchangeable-K, hydrochloric acid extractable-K, lattice-K and total K fractions by ∼1.3, 3.4, 18.6, 11.0 and 34.1%, respectively due to residue retention, compared with no residue. Therefore, conventional tillage with puddled transplanted rice (CTR) with wheat residue and green manure during intervening period (CTR+GM), and zero tillage wheat with rice residue retention (ZTW) were emerged as highly valuable technological options for mitigating soil degradation effects under intensive RWS for food grains in north-western India.