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Yield and Quality of Alfalfa as Influenced by Additions of S to P and K Fertilizations under Greenhouse Conditions

Y. A. Martel, J. Zizka
Agronomy journal 1977 v.69 no.4 pp. 531-535
Haplorthods, Humaquepts, Medicago sativa, NPK fertilizers, alfalfa, clay, dry matter accumulation, fertilizer application, greenhouse production, greenhouses, potassium fertilizers, rain, sandy loam soils, sandy soils, silty clay soils, sulfur, sulfur fertilizers, superphosphate, Quebec
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.