Objectives This study investigated the effects of P application rates on the physicochemical properties and yield of potato starch used for different purposes.

Methods Field experiment was conducted in Heilongjiang Province in 2019 and 2020, using ‘Youjin’ and ‘Kexin 13’ potato cultivars as test materials. The treatments were low (P₂O₅ 45 kg/hm², LP), medium (P₂O₅ 90 kg/hm², MP), and high (P₂O₅ 135 kg/hm², HP) P application rate, with no P application designated as the control (CK). The physicochemical properties and yield of potato starch were determined.

Results P application reduced the amylose content of potato starch by 3.19%−5.14% for ‘Youjin’ and 2.97%−9.05% for ‘Kexin 13’ compared to CK; the decrease in cultivar ‘Youjin’ in 2019 under HP was more pronounced than other treatments. The addition of P to potato starch increased its transparency and swelling capacity while decreasing its solubility. Compared with CK, HP (P<0.05) increased starch transparency by 15.00% (Youjin) and 25.74% (Kexin 13), increased swelling power by 3.94% (Youjin) and 7.90% (Kexin 13), and decreased solubility by 12.23% (Youjin) and 21.84% (Kexin 13). The median diameter (D₅₀) of ‘Youjin’ was the highest under MP treatment (11.58% higher than CK), while ‘Kexin 13’ recorded a decrease in D₅₀ with an increasing P application rate. The D₅₀ of ‘Kexin 13’ in HP was 5.02% lower than CK. However, the D₅₀ of ‘Kexin 13’ was larger than ‘Youjin’. The starch yield of ‘Youjin’ under MP treatment and ‘Kexin 13’ under HP treatment was the highest, corresponding to 31.36% and 29.66% increase compared to CK.

Conclusions Appropriate P fertilizer application rate efficiently increased the dry matter accumulation and starch yield of potato. Further, it can boost amylopectin levels and improve potato starch’s transparency and swelling power. The optimum application rate of P₂O₅ is 90 kg/hm² for ‘Youjin’ and 135 kg/hm² for ‘Kexin 13’.