In-Furrow Application of Phosphorus and Silicon Effects on Potato Tuber Yield and Grade.

In soils with low phosphorus (P) availability, P deficiency limits the number of tubers per plant and the size of the tubers of potato (Solanum tuberosum L.) crop. In this condition, silicon (Si) fertilization can improve the use efficiency of applied P and increase tuber yield of potato crop because Si may increase the P availability in soil by competition with P by the same adsorption sites. The aim of this study was to evaluate the effect of in-furrow application of P and Si effects on tuber yield and grade of potato cv. Agata. Three field experiments were carried out in clayey Oxisols with low-medium P_{resin-extractable} content (9 to 28 mg dm^-3), São Paulo State, southeastern region of Brazil. The experimental design was randomized complete blocks in 4x2 factorial scheme, with four replications. Treatments were constituted of four rates of P (0, 125, 250, and 500 kg ha^-1 P₂O₅) combined with absence and presence of Si application (75 kg ha^-1 Si). Phosphorus was supplied as triple superphosphate (41% P₂O₅) and Si as FertiSilica (22.4% of soluble Si) in powder form. Both P and Si fertilizations were applied into planting furrow. In all experiments, P fertilization increased the total tuber yield and yield of tubers larger than 45 mm in diameter, regardless of Si application.Despite major differences were found between the absence of P fertilization and the application of 125 kg P₂O₅ ha^-1, the highest total tuber yields were achieved with rates between 250 and 500 kg P₂O₅ ha^-1. Silicon supplying did not affect the tuber yield and grade of the potato crop.