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Phosphorus and Potassium Fertilization of Irrigated Alfalfa on Calcareous Soils: I. Soil Test Maintenance Requirements
Author(s) -
Fixen P. E.,
Ludwick A. E.
Publication year - 1983
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1983.03615995004700010022x
Subject(s) - potash , calcareous , agronomy , potassium , phosphorus , fertilizer , seeding , human fertilization , soil water , medicago sativa , environmental science , crop , zoology , calcareous soils , chemistry , biology , soil science , botany , organic chemistry
Field experiments with irrigated alfalfa ( Medicago sativa L.) were established in far eastern Colorado on a Keith soil and in far western Colorado on a Ravola soil in 1976. Concentrated superphosphate was applied at rates of 25 and 50 kg P/ha annually for 3 years or 75 kg P/ha in a single application at seeding. Muriate of potash was applied at rates of 140 and 280 kg K/ha annually for 3 years or 420 kg K/ha in a single application at seeding. Soil profile changes in NaHCO 3 ‐P and exchangeable K were determined. At a location having low to medium available‐P status (crop response to P expected), 2.2 times the P removed by the alfalfa was required to maintain the initial NaHCO 3 ‐P level. At a location with medium to high available‐P status (no P response expected), only 1.4 times the removed P was required for maintenance. The two locations required a fertilizer K rate of 0.75 and 0.22 times the K removed by alfalfa uptake to maintain their respective initial exchangeable‐K levels. The low maintenance requirement of the latter soil was apparently due to the K minerals present which buffered the exchangeable K near 100 mg·kg −1 .