Impact of phosphorus rate, soil fumigation, and cultivar on potato yield, quality, phosphorus use efficiency and economic returns in a high phosphorus soil

Phosphorus (P) is a non-renewable resource that will become an economic limiting factor for food production in the future. Potato (Solanum tuberosum L.) is a relatively shallow rooted crop and often responds positively to P fertilizer even in soils with high soil-test P. Therefore, high-rate P fertilizers are commonly applied to produce high tuber yields in commercial potato fields. The purpose of this study was to evaluate the effects of P rate, cultivar, and soil fumigation on potato yield, quality, P uptake, P use efficiency and economic returns under high soil test P conditions. A field study with a split-plot randomized complete block design was conducted in 2021 and 2022, with fumigation treatments (no fumigant or fall-applied metam sodium) being the main plots and cultivars (Ivory Russet or Russet Burbank) as subplots. Each subplot was further divided into five sub-subplots with different P rates: 0, 37, 73, 147 and 220 kg P ha^-1. The results indicated that Russet Burbank produced higher total yield than Ivory Russet. Fumigation significantly increased tuber yield and dry matter percentage. Both cultivars responded to P application and tuber P uptake increased with P rate even under very high soil test P conditions. Both partial factor productivity (PFP) and P recovery efficiency (PRE) were very low and significantly decreased with the P rate. Russet Burbank had higher PFP and PRE than Ivory Russet, and fumigated plots had significantly higher PRE than non-fumigated plots. The tuber yield output and net revenue of Russet Burbank was higher than Ivory Russet, and the highest economic return was obtained in fumigated plots at 147 kg P ha^-1. These results suggest that cultivar selection and control of soil-borne diseases should be considered to optimize P input, tuber yield, and to conserve P resources.