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Agronomy Journal Abstract -

Organic Matter Relationship to Soil Nutrient Status and Aluminum Toxicity in Alfalfa1


This article in AJ

  1. Vol. 77 No. 5, p. 735-738
    Received: Nov 26, 1984

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  1. D. I. Kapland and
  2. G. O. Estes2



The objective of this investigation was to evaluate in unaltered soils the relationship of organic matter (OM) to soil nutrient levels and aluminum (Al) toxicity to alfalfa. The Ap and B2l horizons from 12 agricultural soils were collected from throughout New Hampshire. The pH range of the soils was 4.91 to 6.60, exchangeable Al was 0.01 to 0.89 cmol (p+) kg−1, organic matter was 6.6 to 81.6 g/kg, and textures ranged from sandy to silt loams. Four kilograms of each soil were potted and seeded to alfalfa (Medicago sativa L.) in a greenhouse experiment. The level of soil OM was highly correlated with top dry weights of 3-week old alfalfa and top and root dry weights of 9-week old alfalfa. Increases in OM levels also resulted in corresponding increases in exchangeable soil calcium, magnesium, potassium, extractable phosphorus (Bray l), total nitrogen, and cation exchange capacity (CEC). A significant amount of variation in the top dry weights of 3-week old plants and in the top and root dryweights of 9-week old plants was accounted for by taking into consideration the interaction of Al and organic matter. With the use of three-dimensional computer plotting programs, the critical Al level of alfalfa was correlated with soil OM levels (r=0.883). An incremental increase of 1% in soil OM on a dry-weight basis (starting from about zero) increased critical Al levels by 0.3 cmol (p+) kg−1

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