Suitable deep sowing increasing emergence rate and promoting summer maize growth in seeding stage under subsurface drip irrigation

Soil water in subsurface drip irrigation condition hardly reaches seed bed of summer maize, and thus greatly affect seed germination and emergence. In order to determine optimal sowing depth of summer maize under subsurface drip irrigation condition, 2 successive field experiments from July to August, and from September to October in 2015 was conducted using a randomized complete block design under rain-proof shelter in the Science and Technology Demonstration Park of Henan Agricultural University(113°38′3″E，34°47′51″N). Different sowing depth was designed including 3, 5, 7, 9 and 11 cm. Each treatment replicated 3 times. During the experiment, germination, plant height, and aboveground biomass accumulation in the seeding stage of maize were investigated. Meanwhile, soil water content was measured before and after irrigation at a 10-cm interval from 10 to 40 cm soil depth and at a 20-cm interval from 40 to 80 cm soil depth, and soil temperature in 5, 10 and 15 cm layer was recorded in the second experiment. The results showed: 1) Soil water content after irrigation was higher than that before irrigation. Soil moisture could infiltrate upward to 10 cm and percolate downward to 80 cm below soil surface when irrigation amount was 450 m³/hm² under subsurface drip irrigation conditions; 2) Seeding germination became delayed when the sowing depth increased except for the treatment of 3-cm sowing depth. Among all the treatments, the sowing depth of 3 and 11 cm had the lowest seeding emergence rate, which decreased by 22.22%-38.89% and 5.88%-11.11% than the sowing depth of 7 cm, respectively. The germination of the former treatments was 1-1.5 d delayed than the latter. Overall, the germination rate of the second experiment was lower than that of the first; 3) The plant height was the lowest in the sowing depth of 3 and 11 d, but the variation coefficient of plant height was the highest. Comparatively, the sowing depth of 7 and 9 d had higher plant height with smaller variation coefficient; 4) Similar with the plant height, the aboveground dry matter was the lowest in the 3 and 11 cm sowing depth, and that of 7 and 9 cm was the highest. The coefficient of variation of the first experiment was 7.95%-20.20%, lower than that of the second experiment (14.09%-22.08%). In sum, the sowing depth of 7 and 9 cm had the highest seeding emergence rate and aboveground dry matter accumulation, and lower variation coefficient of plant height and aboveground dry matter accumulation. Under subsurface drip irrigation condition, 7-9 cm was optimal sowing depth for summer maize cultivation. This study could provide technique information on cultivation of summer maize under subsurface drip irrigation.