Potassium Effects on Improved Growth, Nodulation, and Nitrogen Fixation of Hairy Vetch1
- J. Q. Lynd,
- Edward A. Hanlon and
- George V. Odell2
Symbiotic N fixation by forage legumes presents practical means for improved pasture productivity. However, soil fertility and plant nutrient deficiencies may greatly limit legume growth, nodulation, and nitrogenase activity levels.
Results from 3 years' field and greenhouse experiments were evaluated to determine the influence of K and P levels with and without Ca on growth, nodulation, nitrogenase (C2H2 reduction) and nodule cytosol components of ‘Madison’ hairy vetch (Vicia villosa Roth) grown in a siliceous thermic Psammentic Paleustalf (Eufaula). Significant increases in both growth and seed yield resulted from application of 50 mg P and 100 mg of K/kg soil. Nodulation and nitrogenase activity (C2H2 reduction) at anthesis (248 day age) were significantly increased with both P and PK treatments. Nitrogenase activity levels correlated with nodule mass with highly significant increases resulting from the K treatment. Phosphorus content of nodule cytosol was significantly increased with 0, 50, 100, 150 mg P/kg soil in factorial combinations with 100 mg of K and 400 mg of Ca/kg soil. Nitrogenase activity levels were increased with all K treatments and effects of K were highly significant influencing every parameter except cytosol Ca. Cytosol Na was reduced inversely to increased K content. Growth increased in quadratic response to 0, 100, 200, and 300 mg of K applied with and without 100 mg of P/kg soil. Highly significant linear increase in nodule weight, nitrogenase activity, and nodule cytosol K resulted with increased K levels without P interaction. Cytosol Ca, Mg, and P were significantly increased, and highly significant decreases in Na resulted with increased K applications. The most reliable response surface by multiple regression with R2 = 0.738 was: nitrogenase = 48.36 nodule weight + 0.1 K − 1.44 top weight − 0.04 Na + 0.01 Ca, C.V. = 27.4%. Nodule weight × nitrogenase correlations were highly significant with negative correlations existing for cytosol Na and every other parameter.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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