YIELD OF DRY MATTER AND NITROGEN FROM TOPS AND ROOTS OF SWEETCLOVER, ALFALFA AND RED CLOVER AT FIVE STAGES OF GROWTH

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Abstract
Sweetclover (Melilotus officinalis L.), alfalfa (Medicago sativa L.), and red clover (Trifolium pratense L.) were grown to determine their value for returning nitrogen to the soil at two locations in northeastern Saskatchewan from 1956 to 1960. Yields of dry matter and nitrogen in the top growth and in the roots were determined for each crop at rive stages of growth. The legumes were seeded m association with a fertilized and an unfertilized companion crop of wheat (Triticum aestivum L.).Sweetclover produced the greatest yield of top growth at all harvest dates. The root weights of alfalfa and red clover had surpassed those of sweetclover by July 15 (full-bloom stage) and September 15 (mature-seed stage), respectively. Percent nitrogen in the top growth of the legumes ranged from 1.87 to 2.61% on September 15 of the first year and from 2.58 to 2.89% by June 15 of the second year. After June 15, a sharp decline in percent nitrogen of the top growth occurred, especially in sweetclover. Percent nitrogen of the root growth of sweetclover also declined rapidly after June 15, while that of alfalfa and red clover increased.If sweetclover, alfalfa or red clover were used for green manure in late June or early July of the second year, a return of 70 to 90, 60 to 95 and 50 to 75 kg N/ha, respectively, would have occurred. If a crop of hay or silage was removed and only the stubble used for green manure, the average nitrogen returns to the soil from sweetclover, alfalfa and red clover would have been 10, 20, and 15 kg N/ha, respectively.Fertilizer increased the yield of the companion crop and reduced the yield of the legumes.
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