Regulation of whole field soil-plastic mulching with bunch planting and whole field sand mulching with flat planting on soil moisture and yield of spring wheat in semiarid dryland areas

Whole field soil-plastic mulching with bunch planting is a firstly spreading wheat cultivation technique in Gansu Province. Domestic studies have shown significant increases in yields of wheat, flax and other crops under this cultivation mode. Previous researches mainly focused on the cultivation techniques and yield effects, with little documentation of the mechanism of yield increase. To address this knowledge gap, field experiments were conducted to explore the regulation of whole field soil-plastic mulching with bunch planting (PM) and whole field sand mulching with flat planting (SM) on soil moisture content and yield of spring wheat in semiarid dryland areas. The results showed that compared to uncovered and flat planting (CK), PM and SM significantly improved soil moisture conditions in the 0?40 cm soil layer. This was especially noticeable in dry years, which supported early growth of wheat by enhancing water use in the 0-200 cm soil layer after wheat emergence. The maximum soil water used by wheat under PM was from 60-80 cm and that under both SM and CK was from 40-60 cm in the first year (median water year) of wheat cultivation. In the second year (less water year) of cultivation, the maximum soil water used under PM was from 120-180 cm and that under both SM and CK was from 60-80 cm. After two years of continuous cultivation, the depth of used water under PM increased from 120 cm to 200 cm, that under SM increased from 120 cm to 140 cm and that under CK remained unchanged. Leisure efficiency of PM was the highest, followed by SM and then CK. Leisure efficiency of each treatment decreased with increasing years of wheat cultivation. In summary, PM and SM improved the moisture environment of the soil in early wheat growth period, promoted water use after wheat emergence and accelerated the use of deep soil moisture. Compared with CK, PM and SM increased wheat yield by 48.77%-815.79% and 49.41%-702.24%, respectively. But with increasing years of cultivation, the depth of used water deepened and leisure efficiency decreased, with negative impacts on soil water balance.