Objectives The contribution of long-term application of green manure to soil fertility and crop yield of irrigated desert soil in Hexi oasis irrigation area was assessed.
Methods Long-term fertilization experiment in irrigated desert soil of Wuwei started in 1988. The cropping system was wheat / maize intercropping, and the green manure was common vetch. Four treatments were included in the study, green manure combined with phosphorus (GP), green manure combined with nitrogen and phosphorus 1/2 (G + N) P, nitrogen and phosphorus (NP), and blank (control, CK). Soil samples of 0 – 20 cm topsoil were taken in 2018, and pH, organic matter and nutrient contents were determined.
Results GP and 1/2 (G+N) P treatments significantly increased soil fertility and crop yield of irrigated desert soil. Compared with the initial value of the experiment, GP and 1/2 (G + N) P treatments increased soil organic matter by 68.8 % and 56.6 %, increased total nitrogen by 75.8% and 56.3 %, increased total potassium by 16.1 % and 18.0 %, and decreased total phosphorus by 20.3 % and 27.8 %. Compared with NP treatment, GP and 1/2 (G + N) P treatment increased soil organic matter by 29.0 % and 19.6 %, total nitrogen by 43.3 % and 27.4 %, total phosphorus by 18.4 % and 7.2 %, and total potassium by 1.7 % and 3.3 %. The wheat yields of GP and 1/2 (G + N) P treatments were 8.0 % and 6.5 % higher than that of NP treatment, respectively. The maize yields of NP and 1/2 (G + N) P treatments were 20.3 % and 19.8 % higher than that of GP treatment, respectively. The average 31-year fertilizer contribution rates (FCR) of GP and 1/2 (G + N) P treatments were 0.53 and 0.59, respectively, the coefficients of variation (CV) were 0.23 and 0.20, respectively, and the sustainability indexes (SYI) were 0.54 and 0.62, respectively.
Conclusions Combined application of green manure and nitrogen and phosphorus fertilizers can continuously improve soil organic matter, total nitrogen and total potassium content, fertilizer contribution rate, crop yield stability and sustainability. The yields of wheat and maize are significantly correlated with soil total phosphorus and available phosphorus. Therefore, it is a win-win fertilization method for the economic and ecological benefits of wheat and maize production on the irrigated desert soil in Hexi Oasis Irrigation District of Gansu Province to adopt the combined application of green manure and chemical fertilizers.
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