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

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 4x3 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.