Effects of straw layer and flue gas desulfurization gypsum treatments on soil salinity and sodicity in relation to sunflower yield

Abstract

Burying a straw layer in the subsoil has been proposed for cutting the capillary movement of soil water and salt in saline soils, and flue gas desulfurization (FGD) gypsum has been widely used for reclaiming the productivity of alkali soils. However, the available information on the combination of these two approaches with respect to the amelioration of saline–alkali soils is limited. A 2-year field experiment was conducted on the Hetao Plain of China to evaluate the combined effects of straw layers (0, 6, 12 and 18 t ha−1) at a depth of 30 cm and FGD gypsum (0 and 0.75 t ha−1) mixed into the topsoil (0–20 cm) on soil physicochemical properties and sunflower yields. The soil water content, which increased at planting but decreased at harvest in the overlying (0–30 cm) soil in both years, was affected mainly by the straw layer. The soil electrical conductivity (EC) and exchangeable absorption percentage (ESP) after the straw treatments were markedly lower than those obtained after the non-straw treatments, and the soil pH at planting was positively affected. The positive effects of the straw layer on soil salinity and sodicity increased with increasing rates. Compared with the individual straw applications, the combined applications increased the reductive effects on ESP and pH, but increased the EC at planting. Additionally, compared with the non-gypsum controls, the combined applications increased the sunflower yields by 17.4% in 2015 and 20.4% in 2016. These results suggest that a dense straw layer combined with the appropriate application of FGD gypsum can substantially reduce both soil salinity and sodicity and increase the sunflower yield.