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Levels and Sources of Potassium for Alfalfa as Influenced by Temperature 1
Author(s) -
Smith Dale
Publication year - 1971
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1971.00021962006300030045x
Subject(s) - potassium , shoot , chemistry , medicago sativa , zoology , agronomy , horticulture , biology , organic chemistry
Studies were conducted with KCl and K 2 SO 4 as K sources (0, 336, and 672 kg/ha of added K) for alfalfa ( Medicago sativa L.) grown to first flower in growth chambers at 21/15 C day/night temperatures. Growth and mineral composition of alfalfa at first flower in three temperature regimes (27/21, 21/15, and 15/10 C) also were studied in low‐K soil with 0, 168, 336, and 672 kg/ha of K added as K2SO4. KCl applied at high rates (672 kg/ha of K) to soil containing 205 kg/ha of exchangeable K caused damage to alfalfa plants grown in pots, presumably from the Cl ion. No injury was noted with K 2 O 4 . K 2 SO 4 applied (168, 336, and 672 kg/ha of K) to soil containing 120 kg/ha of exchangeable K increased herbage, root, and total plant yields, plant heights, and shoot numbers at the first flower growth stage. Largest increases occurred with the first increment of K and when grown at cool temperatures. Percentage of K in the herbage was highest at all rates of applied K in the warmest temperature regime (27/21 C day/night temperatures) and lowest in the coldest regime (15/10 C). Percentages of K in the herbage grown at 15/10 C were all below K‐sufficiency (2.20%) at all rates of K. Higher levels of exchangeable K are needed in the soil under cool than under warm temperatures in order for the plant to obtain sufficient K for maximum growth and production.