Response of dryland maize yield to fertilization rate and planting density at different sowing dates in early-maturity areas

In order to determine the response of dryland maize sown at different dates to fertilization rate and planting density in early-maturity regions, consecutive field experiments were carried out in 2010 and 2011. The experiment studied the effects of sowing dates autumn plowing and early sowing (APES) and conventional sowing (control), fertilization rates and planting densities on the indicators of dryland maize yield. The study aimed to improve yield through highly efficient and compact planting techniques. Results showed that maize grain yield (GY), harvest index (HI) and water use efficiency (WUE) under APES with a certain degree of summer drought in 2010 increased respectively by 9.0%, 7.1% and 6.4% over the control (P < 0.01). The 100-grain weight (HGW, P < 0.01) and kernel ratio (KR, P < 0.05) were also greater than those of the control. GY, HI and WUE under APES in the rainy year of 2011 significantly increased (P < 0.01) respectively by 13.1%, 8.8% and 8.5% over the control. Grain number per spike (P < 0.05) and HGW (P < 0.01) were significantly greater than those of the control. GY and shoot biomass (SB) increased with increasing fertilization rate. However, yield under APES in 2010 decreased with excessive fertilization rate. For the rainy year of 2011, GY under fertilization treatment was significantly greater than that under non-fertilization treatment, while no significant difference was noted in GY among different fertilization treatments. The results suggested that APES with low fertilization rate favored high yields. With increasing planting density, maize GY and SB dynamics in 2010 tracked a quadratic parabolic curve. Plant density of 75 000 plants·hm^-2 gave the highest yield under APES. This suggested that while yields under APES increased at higher planting density in dry year, increasing planting density severely limited yield under the control. In wet year of 2011, GY and SB increased with increasing planting density. However, as planting density was above 75 000 plants·hm^-2, GY no longer significantly increased. In dry year of 2010, the effect of planting density on yield under APES was weaker than that under the control, which generally favored high yield under APES. While fertilization rate and planting density had a significant interactive effect on yield in dry year, such interactive effect was insignificant in wet year. Thus compared with present maize cultivation practices, early sowing during optimum period, low fertilization rate and appropriate planting density was an efficient maize cultivation technique for high yield.