Sub-soil plastic film mulch promotes the growth and yield improvement of winter wheat in coastal saline-alkali soil

Crop yields are seriously threatened in saline-alkali areas with shallow groundwater levels and high evaporation. Mulching can effectively alleviate salt stress on crops in drylands, but there is limited research on winter wheat (Triticum aestivum L.) mulching in coastal saline-alkali areas. To investigate the effect of plastic film mulching on the growth and yield of wheat in coastal saline-alkali soil, three field management measures were designed: bare ground (CK), plastic film mulch (PM), and sub-soil plastic film mulch (PMF). Compared with CK, PM and PMF significantly increased wheat grain yield by 128.2%-313.2% and 187.8%-537.0%, respectively, over the two study stages. The movement of salt to the surface is inhibited after mulching; as a result, PMF and PM significantly decreased the electric conductivity in shallow soil (0-20 cm) by 31.1% and 23.8%, on average, compared to CK, resulting in a significant increase in dry matter accumulation (DM) for winter wheat throughout the growing season. Moreover, PMF increased the overall DM by increasing the dry matter accumulation per plant (DMP), while PM achieved a similar effect to PMF by increasing the number of tillers. Compared with PM, PMF had a better inhibitory effect on shallow soil salinity, significantly increasing the effective number of spikes, effective tillering rate, DMP, and spike weight at harvest; promoting vegetative and reproductive growth of wheat fields; and ultimately increasing yield. PMF can be used to improve winter wheat production in coastal saline-alkali soils. Film mulching will inhibit the concentration of deep salt in coastal saline-alkali land to the surface.There is a significant negative correlation between shallow soil salinity and dry matter accumulation (DM) of winter wheat.Film mulching will promote the tillering ability and the DM of winter wheat.Higher dry matter accumulation per plant and rate of the available tillering are the reasons why the DM of sub-soil plastic film mulch is higher than plastic film mulch.Plastic film mulching mainly achieves yield growth by increasing the number of spikes.