The Ways of Fertilizing Phosphorus Affects Its Dynamics and Inorganic Forms in Drip-irrigated Cotton Field

Abstract

【Background and objective】 Soil in most regions in Xinjiang of China are rich in calcium (Ca), and long-term application of phosphate fertilizer could result in chemical reactions between phosphorus (P), Ca and iron, thereby enriching soil P. This could reduce the utilization efficiency of P fertilizer. Since 1997, Xinjiang has promoted mulched drip irrigation-fertilization with the fertilizers directly delivered to the root zone to improve their use efficiency. Due to the poor mobility of P in soil, how to optimize P fertilization to change its form so as to facilitate its uptake by crops is important but remains obscure. The purpose of this paper is to address this knowledge gap. 【Method】 A two-year field experiment was conducted from 2019 to 2020 at a cotton field in Changji, Xinjiang. It consisted of four treatments: basal application of all base fertilizers with topdressing using amino acid solution (DF1), basal application of all base fertilizers with topdressing using microbial fertilizers (DF2), additional application of all base fertilizers with topdressing using amino solution (NF1), additional application of all base fertilizers with topdressing using microbial fertilizers (NF2). In each treatment, soils were sampled at the bud, flower boll, boll opening and harvest stages to measures bioavailable P, microbial P, inorganic P forms and the ultimate cotton yield. 【Result】 NF1 and NF2 significantly increased effective P and microbial P in the 0~20 cm soil at flower boll, boll opening and harvest stages, compared with DF1 and DF2. In terms of inorganic P forms, NF1 and NF2 increased Ca2-P content in 0~20 cm soil at boll stage, reduced Ca10-P and AL-P content at boll stage, and increased Ca8-P content from the bud to boll opening stage first and reduced it at the harvest stage. Soil effective P was positively correlated to Ca2-P and negatively correlated to Ca10-P and AL-P, both at significant level. Topdressing all base fertilizers can significantly increase P input to soil and reduce its conversion to slow-acting P, thereby increasing the effectiveness of P in soil. Compared with basal application of the base fertilizers, topdressing them increased the average cotton yield by 7.5%. 【Conclusion】 Reducing base fertilizer application, precision-applying P fertilizer based on what the cotton requires can increase bioavailable P in soil, reduce P conversion to ineffective P, thereby increasing crop yield.

Keywords

• fertilization method
• bioavailable p
• p classification
• phosphorus accumulation
• drip irrigation