Potato yield and phosphorus nutrition using humic substances in two soil textures

Abstract: The objective of this work was to evaluate the effect of humic substances (HS) and phosphorus fertilizer on the growth, P uptake, tuber yield, fertilizer P recovery (FPR), and applied P-use efficiency (APUE) of potato (Solanum tuberosum) cultivated in a sandy and in a clayey soils. In both soils, the experiment was carried out in a randomized complete block design, in a 4×3 factorial arrangement, with four replicates. The treatments consisted of four P rates (0, 100, 200, and 400 kg ha-1 P2O5) and of three HS rates (0, 50, and 300 L ha-1). Phosphate fertilization increased the P uptake and tuber yield of potato in both soils. Soil characteristics conditioned the effect of the addition of HS. In the sandy soil, with a lower content of organic matter (OM) than the clayey soil, the addition of HS increases the P uptake and FPR, besides providing a greater tuber yield and APUE, especially under the P absence or with the application of a reduced P rate. In the clayey soil, HS does not affect the response of potato to P fertilization.