NPK RESIDUAL EFFECTS IN THE PSAMENTIC HAPLUSDALF WITH UNIRRIGATED FORAGE SORGHUM (Sorghum bicolor (L.) Moench) IN ROTATION WITH POTATO (Solanum tuberosum L.)

Abstract

The objectives of this research were to know the residual effects of the macronutrients N P K, applied in the non-irrigated Psamentic Haplusdalf, initially cropped with potato (Solanum tuberosum L.) and later with forage sorghum (Sorghum bicolor (L.) Moench, evaluating dry matter accumulation, plant height, leaf area index, leaf area ratio and the water use efficiency. The trials with sorghum were conducted in 1998 and 2000. It was used a randomized block design with 33 factorial arrangement of the W group of confounding and two replications. The fertilizers were applied from 1995 to 1997, excepting phosphorus, which was applied only in 1995. In 1998 the residual effect of nitrogen over 100kg ha-1 reduced dry matter production and the one for phosphorus increased. However, for the variable water use efficiency, the nitrogen was less efficient than phosphorus. Considering the potassium factor, the only significant response was found for the variable leaf area ratio. In the year 2000, only the nitrogen reduced significantly the variable leaf area ratio. Based on these findings, it is clear that the residual effects of the fertilizers should be considered in future crops, since it means, evidently, economy to farmers.

Keywords

• residual effect of NPK: mineral nutrition
• forage sorghum: productivity