Effect of tillage and fertilization on water use efficiency of maize in dryland conditions

As crop production in rain-fed systems is highly dependent on natural rainfall, making full use of rainfall and increasing water use efficiency are the main modes of dryland farming. Spring maize is one of the main grain crops in Weibei drylands where the plowing induces greater soil water evaporation. Conventional tillage is conducive for high water use efficiency in dryland farming. A study on fertilization and tillage in a field experiment was conducted in Weibei highlands in 2013-2015 to determine the effects of tillage and fertilization on soil water consumption and water use efficiency of spring maize in Weibei drylands. A total of six treatments were processed in the experiment — conventional tillage with low fertilization (A1), no-tillage with high fertilization (A2), subsoiling with balanced fertilization (A3), conventional tillage without fertilization (B1), no-tillage without fertilization (B2) and subsoiling without fertilization (B3). Soil water moisture in the 0-200 cm layer during fallow period and maize growth stages was measured and also grain yield under different treatments measured. The results showed that: 1) conservation tillage significantly improved soil water storage during fallow period. Compared with B1, B2 and B3 treatments increased oil water storage by 23.39 mm and 27.73 mm, respectively. 2). Conservation tillage increased soil water storage during the growth stage. Compared with B1, B2 and B3 enhanced water storage in the 0-200 cm by 13.41 mm and 15.70 mm, respectively. Compared with A1, A2 and A3 improved soil water storage by 13.15 mm and 19.54 mm, respectively. During the experiment, balanced fertilization effectively improved average soil water storage for the whole growth period by 6.79 mm. 3) Conservation tillage combination with fertilization increased grain yield and water use efficiency. Compared with B1 treatment, B3 improved grain yield by 212-576 kg·hm^-2 and increased water use efficiency (WUE) by 0.83-2.21 kg·hm^-2·mm^-1 (P < 0.05). Also compared with A1, A3 treatment increased grain yield by 659-1 495 kg·hm^-2 and WUE by 0.65-3.82 kg×hm^-2·mm^-1 (P < 0.05). Balanced fertilization had the highest grain yield and WUE. Compared with low and high fertilization, balanced fertilization increased grain yield by 1 268-2 682 kg·hm^-2, and improved WUE by 0.08-4.45 kg×hm^-2·mm^-1 (P < 0.05). Correlation analysis showed a significant positive correlation between grain yield and soil water consumption during grain-filling stage. It was also noted that conservation tillage improved soil water storage in the early growth, increased soil water storage during tasseling-grain filling stage and promoted WUE at critical periods to increase grain yield. Thus, the combination of subsoiling with balanced fertilization was a suitable tillage system for enhancing grain yield and WUE in Weibei drylands.