The response of certain crops to potassium on several soil types in Tennessee

Current fertilizer recommendations are frequently based on the results of rapid chemical soil tests. These chemical tests are designed to measure the more readily soluble and hence supposedly "available" nutrients in the soil. The amounts of such available nutrients that must be present in the soil for satisfactory plant growth must be determined by actual field trials. Only when a sufficient body of data from both field and laboratory research has been correlated can fertilizer recommendations be made safely on the basis of chemical tests alone. For example, if it is found by chemical test that a soil sample contains 150 pounds per acre of a given nutrient and field trials over a period of years have shown that 200 pounds are necessary for proper growth of a certain crop, then fertilizer applications of that nutrient can be expected to give profitable returns on that crop.

Data of the above character have been accumulated by several investigators, though few of them have worked in Tennessee. Results obtained from other areas have limited application in this State since a variation in climatic factors as well as farming and cropping practices might well exert a marked influence on the crop response obtained from a given fertilizer.

A study of the effect of potassium fertilizers on certain crops grown on various soils of Tennessee was started in the spring of 1940 by Davidson (4). He correlated yields with soil tests. The studies he started were continued by the present author through the 1941 season in order to supplement the data available for this State.