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Available potassium in orchard soils as affected by a heavy straw mulch

Wander, I.W., Gourley, J.H.
Agronomy journal 1938 v.30 no.5 pp. 438-446
tillage, Pyrus communis, Poa, potassium, loam soils, NPK fertilizers, orchards, soil fertility, soil depth, exchangeable potassium, cover crops, straw mulches, Ohio
Data are here presented to show the amount of available potassium under three different systems of culture, viz., mulch, sod, and cultivation with cover crops, which have been maintained over a relatively long period of time on a Wooster silt loam soil. The investigations included both fertilized and unfertilized plats. Both a quick test and a method including the quantitative determination replaceable potassium were used. On plats under grass and clean cultivation with cover crops and treated with a potash fertilizer, it was found through "quick" tests that there had not been any appreciable downward movement of available potassium beyond a depth of 6 inches. The treatments have covered a period of 10 years during which there has been an increasing rate of potash application. At the present time (1938) potash fertilizers are applied at the rate of nearly 300 pounds per acre per year on the area under the trees. The data obtained by quantitatively determining the replaceable potassium of soil under a heavy mulch that has been maintained for a period of 22 to 38 years, upon which no potassium had been added other than that supplied by the mulch, showed that available potassium was very high to a depth of from 24 to 32 inches. This is in contrast to a lesser amount found under the adjacent bluegrass sod and a much smaller amount found under plats in cultivation with cover crops. Available potassium was found to be "low" to "very low" in a nearby unfertilized field plat which was taken as a check on the cultivated plats.