Effects of different saline-alkali land amendments on soil physicochemical properties and alfalfa growth and yield

Saline land improvement is important in offsetting contradictions between increasing population and declining soil areas. It enhances the quantity and quality of farm production, improves ecological environment and promotes regional development of sustainable agriculture. This study determined the effects of localized saline-alkali soil amendments on heavy saline-alkali soil. The experiment used alfalfa as trial crop to investigate the effects of desulfurized gypsum, Guochan-1 and Guochan-2 amendments on soil physical and chemical property and the emergence rate and fresh yield of alfalfa in waste saline-alkali soils with heavy soda. The effects of desulfurized gypsum on heavy metal contents of soils and leaves and stems of alfalfa were also investigated under field conditions. The experiment was conducted in a complete randomized design with four replicas of each treatment. Four treatments were control (without amendment), Guochan-1 (application rate of 2 250 kg·hm^-2), Guochan-2 (application rate of 7 960 kg·hm^-2) and desulfurized gypsum (application rate of 22 500 kg·hm^-2). The results showed that compared with the control, soil pH reduced by 0.11~1.46, soil density declined by 0.01~0.06 g·cm^-3 and porosity increased by 1.15%~10.15% after application of soil amendments. Furthermore, amendments improved soil perviousness and soil physical and chemical properties. Alfalfa emergence rate increased by 18.4% to 31.7%, fresh biomass of the three crops increased by 18.9%~43.5% and yield significantly increased under amendments over the control. Soil and plant Hg, Pb and Cr contents were significantly influenced by desulfurized gypsum and Guochan-2 appli-cations. Among the three amendments, Guochan-2 amendment produced the best effects regarding saline-alkali soil improvement. Whereas heavy metal content did not exceed Grade-II Soil National Standard for Agricultural Environment Quality, alfalfa Hg, Cd, Pb and Cr contents were within National Standard for Feed Qygienic Quality. This research suggested that among the three sa-line-alkali soil amendments, Guochan-2 produced the best effects. It was therefore recommended for wide application in similar sa-line-alkali soil conditions.