Alfalfa response to phosphorus sources associated to gypsum and liming

Abstract

Phosphorus is one of the most important nutrients in alfalfa production in Brazilian soils. Several P sources are available in the market and the Gafsa phosphate (GP) is considered as efficient and soluble. The efficiency of phosphate fertilizers is affected by soil acidity. The use of GP associated to gypsum can aliviate Al toxicity and reduce soil phosphorus fixation. Therefore, this study was curried out in a glasshouse experiment, aiming to evaluate the efficiency of the triple superphosphate (TS) and GP and GP with gypsum, applied before and after liming at the rates of 50; 100 and 200 mg P dm-3. The soil was classified as a Typic Hapludox. Alfalfa was seeded three times and plants were harvested only once in the first seeding and three times in the third seeding. In the first seeding alfalfa yield (DM) was higher (3.3 g/pot) under TS than GP (1.0 g/pot), but in the third seeding TS produced less (2.4 g/pot) than GP (6.0 g/pot). GP with gypsum with increased DM yield (7.0 g/pot) in relation to GP (3.7 g/pot) in the third seeding. Alfalfa DM was higher under TS applied after liming (5.0 g/pot) than when TS was applied before liming, in the first seeding (3.7 g/pot). GP with or without gypsum presented similar response in terms of DM yield when applied before or after liming.