Sweet potato yield and quality as a function of phosphorus fertilization in different soils1

Phosphorus (P) is an essential nutrient for growth and yield of sweet potatoes; in sandy soils, sweet potato yield and quality may be limited by application of low P doses, mainly in degraded areas. The objective of this work was to evaluate the effect of P doses on yield and quality of sweet potato root tubers grown in tropical sandy soils with different initial P availabilities: 23.2 mg dm-3(high P -crop rotation) and 3.7 mg dm-3 (low P -post degraded pasture). Two experiments were carried out in a randomized block design, with four replicates. The treatments consisted of P doses (0, 22, 44, 88, and 176 kg ha-1) applied to the planting bed. Tuber yield, number and mean weight of tubers, P concentration in leaves and tubers, exported P, as well as the percentage of starch, reducing sugars, total sugars, and sucrose in the tubers were evaluated. P concentration in the soil was evaluated at the end of the experiment. In the area with high P availability (> 20 mg dm-3 -resin), increasing P doses did not increase root tuber yield and decreased root starch concentrations. In the area with low P availability (< 3.7 mg dm-3 -resin), root tuber yield and starch concentration peaked when applying 68 and 33 kg ha-1 of P, respectively. In areas after degraded pasture, with low initial soil P concentration, P fertilization for sweet potato crops should be carried out with a P dose of 68 kg ha-1. In areas with crop rotation and adequate soil P concentration, P fertilization should be carried out to replace the amount of P exported by the harvested root tubers to avoid decreases in soil fertility.

Automated summary

This study evaluated the effect of different phosphorus doses on the yield and quality of sweet potatoes grown in tropical sandy soils. The results showed that increasing phosphorus doses did not increase yield and decreased starch concentration in areas with high phosphorus availability. In areas with low phosphorus availability, moderate phosphorus doses resulted in higher yield and starch concentration. Therefore, phosphorus fertilization should be adjusted based on the initial phosphorus concentration in the soil in different soil types.