Effect of planting density on deep soil water and maize yield on the Loess Plateau of China

Dryland farmers tend to increase maize plant density with drought and density stress tolerance hybrids to achieve higher grain yield in recent years. However, could this strategy improve yield or water use efficiency (WUE) and be sustainable without decreasing deep soil water in drought-prone environments is not clear. A 4-year of successive field study was carried out with three different drought and density stress tolerance maize hybrids and four plant density arrange from 52,500 to 97,500 plants ha−1. To quantify the responses of grain yield formation and WUE to increasing plant density under various rainfall condition and evaluate the effect on deep soil water balance. Results showed that using of drought and density stress tolerance hybrids could achieve higher grain yield and WUE with higher plant density in normal years, which was associated with an increase in kernels number per square meter. But in dry year, as fewer water was available during reproductive growth stage in higher plant density, grain yield and WUE was gradually decreased with increasing plant density, especially in density stress sensitive hybrid. Soil water balance at 0 to 200 cm depth was not broken by high plant density from the perspective of same water availability at sowing in each year, despite of the lower soil water content during maize growth stage. However, high plant density tended to consume more deep soil water which was hardly been replenished by precipitation, especially in high density tolerance hybrids. Hence, higher density that exceed 60000 plants ha−1 couple with drought and density stress tolerance hybrids is a potential way to improve maize production in dryland, but it increases the risk of deep soil desiccation.