Effect of Soil Moisture Tension and Amendments on Yields and on Herbage N, P, and S Concentrations of Alfalfa1

Abstract

AbstractLow protein concentration has been observed in alfalfa herbage grown on Gray Wooded Luvisol soils, particularly in cool, wet years. Nutrient deficiencies of N, P, and S also occur on these soils. The objectives of this experiment were to determine how soil moisture and soil type interact with amendments to increase yield and change N, P, and S concentrations in alfalfa (Medicago media Pers.) herbage grown in the greenhouse.Three Gray Wooded Luvisols, Typic Cryoboralf (Arborfield clay, Garrick clay loam, Mollic Cryoboralf, and Waitville loam) and one Dark Gray Luvisol soil (Nipawin sandy clay loam) × two soil moisture tensions (100 and 151 millibars) were main treatments. Amendments of cattle manure, sedge peat, and wheat straw were applied on subplots at 2.5y0 of soil weight. Additional subplots of a control and nitrate (70 μg N/g soil before each crop) were added. Two crops of barley (Hordeum vulgare L.) and one of rape (Brassica napus L.) were grown before ‘Rambler’ alfalfa.Yield of alfalfa was significantly related to moisture use (r2 = 77% in cut 1; r2 = 78% in cut 2). Moisture use by alfalfa was higher with cattle manure incorporated in the heavier textured Garrick clay loam and Arborfield clay soils than for other amendments or soil types. The manure treatment applied to Garrick clay loam and Arborfield clay soils under low soil moisture tension (LSMT = 100 millibars) produced the highest herbage yields.In the first‐cut only, N concentration of alfalfa herbage was higher under high soil moisture tension (HSMT = 151 millibars) than LSMT (5.0 vs. 4.8% N) and was higher for ammonium nitrate than for manure or peat amended soils. Concentration of P in alfalfa herbage was significantly higher under LSMT than HSMT. Concentration of S in herbage was significantly lower under LSMT than under HSMT only for cut 1.In general, LSMT interacting with soil type and amendments markedly increased alfalfa yields, reduced N and S, and increased P concentration in herbage as compared with HSMT.