Abstract
This study investigates the impact of phosphorus fertilization on the yield and quality of various alfalfa (Medicago sativa L.) varieties grown in light chestnut soils. Conducted over a three-year period from 2013 to 2015, the research was carried out in the Karasay district of the Almaty region under irrigated conditions. The experiment included six alfalfa varieties: NS Alfa, VS Banat, Mediana, Nera, Niagara, and Kokoray. Four phosphorus treatments were applied: control (no phosphorus), 60 kg/ha (P60), 90 kg/ha (P90), and 120 kg/ha (P120), using double superphosphate as the phosphorus source. The results demonstrated that phosphorus fertilization significantly enhanced both the yield and quality of alfalfa. Across all varieties, the highest yield was observed with the application of 120 kg/ha phosphorus. For instance, NS Alfa's yield increased from 283.3 c/ha in the control to 349.7 c/ha with P120, reflecting a 23% increase. Similarly, VS Banat and Mediana exhibited yield increases of 23% and 25%, respectively, at the highest phosphorus level. The study also revealed improvements in the nutritional quality of alfalfa hay. Crude protein content increased from 20.3% to 22.0% in NS Alfa, while digestible protein content rose from 11.20% to 12.40%. Other quality parameters, including fat and carotene content, also improved significantly with higher phosphorus levels. Moreover, the availability of nitrate nitrogen and mobile phosphorus in the soil increased progressively with higher phosphorus application rates, contributing to better nutrient uptake and overall plant health. This research underscores the importance of phosphorus fertilization in maximizing alfalfa yield and quality. The findings suggest that the optimal phosphorus application rate for enhancing alfalfa production in light chestnut soils is 120 kg/ha, providing valuable insights for sustainable agricultural practices in similar agro-ecological zones.