Four-year effects of soil acidity amelioration on the yields of canola seeds and sweet potato and N fertilizer efficiency in an ultisol

Abstract

A four-year field experiment was conducted in Langxi, Anhui province, China to investigate the ameliorated effects of various amendments on soil acidity, soil fertility properties, yields of canola seeds and sweet potato, nutrients uptake, and nitrogen utilization efficiency by the crops. The nine treatments used were control, lime, alkaline slag (AS), peanut straw (PS), canola straw (CS), organic manure (OM), AS + PS, AS + CS, AS + OM. The chemical fertilizers with 150.0 kg ha−1 N, 150.0 kg ha−1 P2O5, and 150.0 kg ha−1 K2O were applied for all treatments in canola season, while 90.0 kg ha-1 N, 90.0 kg ha−1 P2O5, and 90.0 kg ha−1 K2O in sweet potato season. Application of lime, AS, AS + PS, AS + CS, and AS + OM increased soil pH and decreased soil exchangeable Al3+. AS + OM showed the greatest ameliorating effect on soil acidity, and soil pH of the treatment increased by 0.45 compared with control. Application of AS + OM also led to greater reduction in soil exchangeable Al3+ and greater increase in soil exchangeable calcium and magnesium compared with lime, AS, AS + PS, and AS + CS. Applying amendments alone and combined promoted the physiological nitrogen use efficiency (PNUE) and nitrogen partial factor productivity (PFPN) of canola and sweet potato, thus increased the uptake of N, P, K, Ca, and Mg by the crops, and the yields of canola seeds and sweet potato. The application of AS + OM showed the greatest effect on the PFPN of canola among the treatments, while AS + CS was the best treatment for sweet potato in this aspect. The yield of canola seeds in AS + OM treatment was 2.61 Mg ha-1, and 5.84 times greater than that of control, while that of sweet potato in AS + CS treatment was 8.07 Mg ha-1, and 32% greater than control. In conclusion, AS + CS, AS + PS, and AS + OM were the good way to ameliorate soil acidity, increase use efficiency of nutrients and promote crop production and the AS + OM is the best one in these treatments.