Planting and preemergence irrigation procedures to enhance germination of subsurface drip irrigated corn

Subsurface drip irrigation (SDI) is one of the most efficient types of water-saving irrigation technology. However, in regions prone to drought during the planting period, crop germination may be a problem under SDI. A 2-year field experiment was conducted in Chifeng, Inner Mongolia, China, to assess the impacts of two planting methods (PMs), flat planting (FP) and alternate row/bed planting (AP), and four pre-emergence irrigation (PI) levels, 15, 25, 45, and 60 mm on corn germination, grain yield and crop water productivity (WPc) under SDI. The AP method utilized a small lister furrow that was 10 cm deep and the corn seeds were planted 5 cm beneath the lister furrow. The results indicated that the soil water at the depth of 5 cm vertically below the seeds (SM5) was on average 27% higher under AP than under FP 24 hours after PI. The emergence rate under AP initially increased at the lower PI values and then decreased at the highest PI amount (60 mm). The maximum emergence rate (98% on average for two years) was obtained at 45 mm PI under AP. The emergence rate under FP increased with the PI level, but the average two-year emergence rates were all lower than 80%. The two-year average grain yield and the WPc reached maximum values of 15.3 Mg ha-1 and 35.1 kg ha-1 mm-1 at 45 mm and 25 mm PI under AP, respectively. The average emergence rate, yield, and WPc under AP increased by 21%, 24%, and 21%, respectively, compared with those under FP. No significant differences in kernels/ear or kernel mass under AP or FP were caused by different PI levels. An emergence rate of approximately 90% to 95% for corn was obtained when the SM5 was approximately 82% to 90% of field capacity 24 h after PI. In conclusion, AP with suitable PI can increase the corn emergence rate and improve the grain yield and WPc under SDI in areas prone to drought conditions at planting.