TILLAGE, MULCH AND IRRIGATION EFFECTS ON CORN (ZEA-MAYS L) IN RELATION TO EVAPORATIVE DEMAND

The effects of deep tillage, straw mulching, and irrigation on corn (Z ea mays L.) yield on a loamy sand (mixed, hyperthermic, Typic Ustipsam ment) were studied for early (high evaporativity) and normally sown (r elatively low evaporativity) crop for 3 years in a semi-arid sub-tropi cal monsoon region at Punjab Agricultural University, Ludhiana, India. Treatments included all combinations of two tillage systems (conventi onal tillage - harrowing the soil to a 10-cm depth; deep tillage - chi selling 40 cm deep, 35-40 cm apart), two irrigation regimes (75 mm irr igation when net open pan evaporation accumulated to 75 mm or 50 mm), and two straw mulch rates (0 and 6 Mg ha(-1)). Deep tillage significan tly reduced soil strength (cone index) and caused deeper and denser ro oting than conventional tillage, more so in the dry season and with th e infrequent irrigation regime than in the wet season and frequent irr igation regime. Mulch also improved rooting by influencing the hydroth ermal regime of the soil. Better rooting with deep tillage and/or mulc h helped the crop to extract stored soil water more efficiently, which was reflected in a favourable plant water status (indicated by canopy temperature). Averaged across years, irrigation, and mulch, deep till age increased grain yield by 1.6 Mg ha(-1) for the early season and 0. 5 Mg ha(-1) for the normal season crop over the yield of 2.0 Mg ha(-1) achieved with conventional tillage regardless of season. Yield increa se with mulching was also greater for the early season crop. Crop resp onse to deep tillage and mulching was generally linked to the interpla y between water supply (rain + irrigation) and demand (seasonal evapor ativity) during the growing season. Increasing irrigation frequency in creased crop yield when evaporativity exceeded rainfall early in the g rowing season. The results show that higher corn yields on coarse-text ured soils in these regions may be achieved by advancing the seeding t ime and by using a proper combination of deep tillage, mulch, and irri gation.