Effects of phosphorus application on yield, quality and phosphorus use efficiency of edible sweetpotato: A case study of Xushu 32

To explore the appropriate amount of phosphorus (P) fertilizer and improve economic yield and P use efficiency of edible sweetpotato, we took Xushu 32 as an example and compared the effects of different P application rates on yield, quality, P accumulation and P use efficiency of edible sweetpotato based on a two-year field experiment (soil available P content was 31.70 mg·kg^-1) from 2018 to 2019. There were five P application levels (P₂O₅), including 0 (P₀), 25 (P₂₅), 50 (P₅₀), 75 (P₇₅) and 100 kg·hm^-2(P₁₀₀). The results showed that, 1) compared with P₀, P application significantly increased the yield of fresh sweetpotao and commodity potato, with the effects being the stongest under P₇₅ treatment, followed by P₅₀ treatment. However, there was no significant difference between the two treatments. 2) P application significantly increased the contents of starch and reducing sugar in storage root. The contents of soluble sugar and protein increased significantly under P₅₀ treatment. 3) Du-ring the growth period of 90 to 120 d, P fertilizer supply significantly increased P accumulation and dry matter accumulation of sweetpotato. 4) The apparent P use efficiency (APUE) decreased with increasing P application rates, while P agronomic efficiency (PAE) increased first and then decreased with the increases of P application rates, which was significantly higher under P₅₀ than other treatments. Taking into account the yield, quality, economic yield and P utilization rate of edible sweetpotato, the optimal dosage of P₂O₅ is 50 kg·hm^-2 under the experimental conditions.