Fluctuations in soil test values for potassium as influenced by time of sampling

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Abstract
Soil samples were taken at frequent intervals in 1975 and 1976 from a factorial set of lime-K treatments initiated in Dec. 1970 to determine the effect time of sampling has on K soil test values. Previous work at this site had shown wide fluctuations in K soil test values due to sample time, thus necessitating a more detailed study than was previously made. Such information is necessary if accurate K fertilizer recommendations are to be made. Samples from 28 unfertilized plots showed that months of sampling significantly affected K soil test values. Soil test values for K were highest in late May and declined as the growing season progressed, remaining low until the relatively higher exchangeable K was re-established the following spring.