Carry-over of residual soil moisture with mulching and conservation tillage practices for sowing of rainfed wheat (Triticum aestivum L.) in north-west India

Lack of adequate seed-zone moisture is a major problem in the timely sowing of wheat (Triticum aestivum L.) after maize (Zea mays L.) in rainfed areas of north-west India. Field experiments were conducted during 1993–1997 in an acid Alfisol (typic Hapludalf) in north-west India to conserve rainwater in situ by using four combinations of mulch and tillage practices, and using the conserved moisture for sowing of wheat at different dates. Fresh lantana (Lantana camara L.) biomass was used as mulch during standing crop of maize before the recede of monsoon rains (LNT) or at maize harvest (LNTmh). Conservation (CT, opening of furrow with hand plough for seeding plus mulch) and conventional tillage (CC, preparation of fine seed-bed by digging soil to 12–15 cm depth) were the two tillage treatments. Treatment combinations during 1993 and 1994 were: LNT+CT, LNT+CC, LNTmh+CT and CC; during 1995 and 1996, LNTmh+CT was replaced with CC+LNT treatment. Wheat was sown at three dates, viz. early (S1, mid-October), timely (S2, mid-November) and late (S3, mid-December). Annual mean temperature of the area varies between 8.2°C in January and 28.0°C in June, and annual rainfall (1969–1997) between 1385 and 3259 mm. Mulching during standing crop of maize (LNT+CT and LNT+CC) was most effective in conserving rainwater. Mulching at maize harvest (LNTmh+CT) is either as good or inferior to mulching in the standing crop of maize, depending on the rainfall events. The LNT+CT and LNT+CC, on an average, conserved more water than CC by 7.8 mm in 0–7.5 cm soil layer and by 15.1 mm in 0–45 cm soil layer at S1, 9.2 and 22.2 mm at S2, and 7.1 and 15.0 mm at S3 sowing date, respectively. The corresponding values of moisture conserved with LNTmh+CT over CC were 7.4 and 8.2 mm at S1, 3.6 and 20.1 mm at S2, and 3.9 and 5.8 mm at S3, respectively. The LNT+CT and LNT+CC always produced significantly higher wheat grain yield (0.58–2.96 Mg ha−1) than CC (0.36–1.78 Mg ha−1); except at S2 during the first cropping cycle where wheat yield was statistically the same with all the three treatments. The LNTmh+CT and CC+LNT, in general, produced higher wheat yield than CC. The LNT+CT produced significantly higher wheat yield (1.93–2.84 Mg ha−1 ) than LNT+CC (1.58–2.62 Mg ha−1) during third cropping cycle onwards, while during the first two years, the yield response varied with tillage system and date of sowing. Mulching significantly increased maize yield during third cropping cycle onwards. After four cropping cycles, organic carbon content in 0–15 cm soil layer of mulched plots (LNT+CT, LNT+CC and CC+LNT) was significantly higher (11.3–12.3 g kg−1) than control (CC) plots (9.0 g kg−1).