Fertilizacion de alfalfa con fosforo, potasio y azufre.
1991
Acuna P Hernan | Soto O Patricio | Vidal V Agustin | Martinez R German
Phosphorus, potassium and sulphur were applied on a lucerne sward, cv. Huinca, grown in volcanic soil of Human series (Typic distrandept). The treatments (21) were selected from all combinations of four rates of P (0, 33, 66 and 132 kg/ha per year), four rates of K (0, 42, 84 and 168 kg/ha per year), and four rates of S (0, 30, 60 and 120 kg/ha per year). The experiment was conducted during four growing seasons (1985/86 to 1988/89). A randomized block design, with four replications, and 2.5 x 4 m plots was used. Dry matter (D.M.) production was measured by cutting, four to five times per growing season. The total herbage harvested was analized to determine N,P,K, Ca and Mg uptake. Extractable P and K in soil at 0-10 cm depth was measured before, in the meantime and at the end of the experimental period. Extractable P at different layers, up to 80 cm depth, was measured after the last cut in 1989. Annual D.M. yield increased by 10%, as average of the four growing seasons (16. 9 to 18.7t/ha with 0 and 132 kg/ha of P, respectively). The response was constant between 0 and 132 kg/ha of P and reached 18 kg of D.M. per kg of P applied, in 1987/88. The response of K was also low and it was present since the third growing season. Dry matter production was not affected by S application. The extractable P in soil (0-10 cm depth) tended to decrease, between 1986 and 1989, in the plots without P application; but, when 132 kg/ha per year of P were applied the extractable P reached 29 and 37 ppm in the 0-10 and 0-5 cm layers, respectively. Extractable K in soil decreased from around 150 ppm, in 1986, to 26, in 1989, when 66 or 132 kg/ha of P was applied, or when K rates were 84 or less kg/ha per year. The N yield and P, K, Ca and Mg uptake are discussed.
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