Cultivation mode of Panax notoginseng causes NH4 + accumulation in planting soil

Abstract

ABSTRACT Excessive application of nitrogen (N) fertilizer causes ammonium toxicity in Panax notoginseng production, but the mechanism of excessive NH4 + accumulation in planting soil remains unclear. To reveal the mechanism, this study investigated the N contents of P. notoginseng planting soils, field and lab experiments were designed to assess the plant growth and antioxidant system of P. notoginseng, as well as the effects on soil nitrification. Results showed approximately 70% of the planting soils had a richness N, total N averaged 1.98 g kg−1, available N averaged 146.94 mg kg−1, NO3 − averaged 27.55 mg kg−1, NH4 + averaged 6.92 mg kg−1. Field experiments showed that P. notoginseng fertilized with 300 kg hm−2 (NH4)2SO4 significantly reduced the yield and antioxidant system enzymes activities. Lab simulations indicated that soil nitrification weakness was mainly affected by N application rate and soil moisture rather than P. notoginseng was planting. Field simulations showed that the shading and covering cultivation mode significantly inhibited the conversion of NH4 + in the soil. Therefore, the external mechanism for NH4 + accumulation in P. notoginseng planting soil is due to weakness soil nitrification, which is induced by the shading and covering cultivation mode together with excessive N application. Abbreviations P. notoginseng, Panax notoginseng; TN, total nitrogen; AN, available nitrogen; WHC, soil water holding capacity; MDA, malondialdehyde; SOD, superoxide dismutase; POD, peroxidase; CAT, catalase; APX, ascorbate peroxidase.