EFFETS DES REGIMES HYDRIQUES ET DES pH DU SOL SUR LA REPONSE AU MOLYBDENE DE LA LUZERNE

Abstract

The objectives of this study were to determine the changes in response of alfalfa (cv. Saranac) to molydbenum applications from variations in soil pH and soil moisture. To achieve these ends the test crop was grown on three replicates of the following treatments: Three soils (Ste Rosalie clay, Greensboro loam and Danby sandy loam) adjusted to approximately pH 5.0, 6.5, and 7.5 fertilized at 0.0, 0.1, 0.2 and 0.3 mg Mo kg−1 of soil and maintained at three moisture levels: dry, optimal and saturated. Yields were not affected by molybdenum applications regardless of soil type, soil pH or soil moisture regimes. Mo content of alfalfa increased linearly with rates of Mo from 0.2 ppm to 23 ppm Mo. Liming soil to pH 7.2 produced the same increase of Mo content in alfalfa as applying Mo at the rate of 0.2 mg kg−1 to acid soils. Mo content of alfalfa was also slightly increased by soil moisture. A Mo content of 20 ppm or more was obtained as a result of the combined effect of molybdenum application, liming and soil moisture regimes. The exchangeable Mo content found in soils after the experiment increased with rate of Mo but decreased with increasing soil pH. The uptake of molybdenum was increased so much by liming that the Mo left in soil after cropping was decreased as soil pH increased. Key words: Mo content of soil, Mo content of alfalfa, soil pH, soil moisture, alfalfa