Influence of Phosphorus, Potassium and Liming On Yield of Two Alfalfa Genotypes.

Providing an adequate supply of nutrients is important for alfalfa production and is essential to maintain high quality and profitable yields. Lime, P and K fertilizers are the most common issues input for this forage in the high weathered, low-fertile and acids soils of tropical region. Besides the potential of this forage on ruminant livestock system little is known in Brazil about the agronomic performance of alfalfa cultivars and their nutritional requirements. The effects of combined lime and P and K fertilization on alfalfa and its impact on yield were evaluated in a greenhouse study. Two alfalfa genotypes were grown in 3-kg pots with a Red-Yellow Latosol (Typic Hapludox) and were harvested periodically when the crop presented 10% of flowering. Six growing seasons were evaluated. Treatments comprised two alfalfa genotypes (Crioula and LEN4), five levels of P (0, 0.3, 0.9, 1.6, 3.2 g per pot) and K (0, 0.47, 0.94, 1.91, 3.78 g per pot) and two basis saturation (V=60 and 80%) combined in a 2 x 2 x 5 x 5 fractionated factorial design. Phosphorus fertilizer was applied at alfalfa sowing and K fertilizer splitted after alfalfa cuts. Number of stems and plant height were affected by P fertilizer. Genotypes differed on dry matter yield and leaf area, and the best results were obtained with P and K at higher basis saturation levels. Crioula was the most productive at V=80% and did not presented response to K fertilizer at V=60%. LEN4 needed less K fertilizer to get higher yield and presented lower decrease in production at V=60%.