Deep tillage and residue mulch effects on productivity and water and nitrogen economy of spring maize in north-west India

Alarming decline of groundwater levels in last two decades in Punjab state of north-west India has limited the scope of high water-requiring, but otherwise profitable spring maize crop. This water limitation also calls for optimizing use of fertilizer nitrogen (N). Interventions like tillage and residue management help to address these constraints. This study examined the effects of deep tillage, irrigation, residue mulch and N regimes on root growth, water use, N uptake and productivity of spring maize in a sub-tropical environment. Combinations of two tillage systems viz., deep tillage (DT) and conventional tillage (CT), with two irrigation regimes viz., irrigation water to pan evaporation ratio of 1.0 (I-1.0) and 0.5 (I-0.5) in main plots; and combinations of four N rates viz., 0 (N-0), 50 (N-1), 100 (N-2) and 150 (N-3) kg ha(-1) with two mulch rates viz., 0 (M-0) and 6 t ha(-1) (M) in subplots were randomized with three replications. Deep tillage reduced soil penetration resistance and caused denser rooting than CT. Residue mulch decreased maximum soil temperature by 3.5-8.5 degrees C resulting in better root growth. Root mass at silking in CTI1.0MN3(1.46 t ha(-1)) was comparable to that in DTI1.0M0N3 (1.48 t ha(-1)) suggesting that deep tillage and mulch had similar effects. Interaction effects of irrigation and N on grain yield were significant. Mean yield increased from 4.3 t ha(-1) in No to 7.0 t ha(-1) in N-3 in I-1.0 regime; while in I-0.5 regime, yield increased from 19 t ha(-1) in No to 5.5 t ha(-1) in N-2 and declined thereafter. Deep tillage and mulch modified this synergism by causing greater yield increase in I0.5N3 than in I1.0N3 regime. Comparable grain yield in CTM0I1.0N3 (6.3 t ha(-1)) and DTM0I0.5N2 (6.2 t ha(-1)) indicate that same yield could be realized with less water and N in DT than in CT regime.