Rhizosphere management technology at the core of starter phosphorus fertilizer and ammonium sulfate topdressing increases lint yield and phosphorus efficiency in cotton production under mulched fertigation system

Objective Excessive phosphorus (P) fertilizer application is common in the cotton production of Xinjiang, causing low P efficiencies and low benefit of cotton production. We established a rhizosphere management technology to reduce the P fertilizer input and maintain the high yield of cotton at the same time.

Methods In the five main cotton (Gossypium hirsutum) production areas inXinjiang, the phosphorous application amounts in Shihezi, Changji, and 184 tuan were 26%–111% beyond the recommondation, and in Beiwucha and Liuhudi were even 2.32 and 2.92 times of the recommondation. Comparison field experiments were employed in the five cotton production areas in 2020, taking the conventional P fertilizer practice as control (CK), and the rhizosphere management as treatment (RM). The core of the RM was determing P input by the cotton yield-target recommendation, most P fertilizer was basal applied and a certain amount of P and ammonium sulfate (AS) was applied before germination of cotton as starter fertilizer, and AS was topdressed with drip irrigation at bud and boll stage of cotton to induce rhizosphere acidification. The lint yield, and biomass of the organs were weighed at harvest, the N and P contents in the organs were analyzed, and the partial factor productivity of N (PFP_N) and P (PFP_P) fertilizer, P surplus and earnings were calculated, respectively.

Results  RM treatments were recorded similar lint yields (3263 kg/hm²) to CK (3292 kg/hm²), without significant impaction on the aboveground biomass distribution, N and P uptake, and seed cotton P content, thereby increased PFP_P by 81.3%. RM treatment reduced P surplus by 74.9% on average, the P surplus was as low as 3.6 kg/hm² under RM treatment in experimental site Changji where no basal P fertilizer was applied. At the target lint yield level of 3.1–3.5 t/hm², RM treatment reduced 16.6% of N and 56.5% of P fertilizer input, thus decreased N and P fertilizer cost by 40.7%, saving 2082 yuan/hm², and increased net income by 1845 yuan/hm². In the high fertilizer input sites Beiwucha and Liuhudi, RM treatment reduced N and P fertilizer cost by 3993, and 4464 yuan/hm², and increased the net income by 2931 and 4367 yuan/hm², respectively.

Conclusions The rhizosphere management technology reduced more than half of the total P input while kept the high cotton lint yield, so increased the P fertilizer efficiency and decreased P surplus greatly. The cotton net profit was increased significantly as the decrease of fertilizer cost. So, the rhizosphere management technology is recommended in the nutrient management of cotton production in Xinjiang.