Yield and Quality of Alfalfa as Influenced by Additions of S to P and K Fertilizations under Greenhouse Conditions
1977
Martel, Y. A. | Zizka, J.
Alfalfa (Medicago sativa L.) obtains sulfur from soil reserve, air, and rainfall. These sources of S may need to be supplemented with fertilizer S in normal superphosphate to produce optimum yields. The objective of this work was to determine the need of alfalfa in S fertilization in relation with the addition of P and K normally used on Quebec soils. Alfalfa ‘Rambler’ was grown in the greenhouse and supplied with P, K, and S. A total of 18 treatments and 3 replicates were used on two types of soils — a Humaquept (silty clay Kamouraska) and a Haplorthod (sandy-loam St. André). Dry matter yields and uptake of N, P, K and S by the crop were significantly increased by the addition of S. The increases were more important on the silty clay than on the sandy loam soil. Responses of alfalfa to S were greater than to the addition of P and K. Critical concentrations of S in the crop were found to be 0.10% on the sandy loam and 0.12% on the silty clay soil and appear to be as good an index as N:S ratios to determine S deficiency in alfalfa. Results of this study showed the importance of S fertilization to improve the output of alfalfa on both clay and sandy soils. They suggest that the growing use of concentrated fertilizers containing little S can lead eventually to deficiencies in the plants if other sources of S are not added to normal P and K fertilization.
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