Interaction of drip-applied potassium with soil nutrients

Assess the effect of drip applied potassium (K) as it interacts with other nuitrients


13 Jun 2001


    Drip irrigation is a highly efficient method of conserving water in areas where water is scarce or costly. In a well-designed and well-managed system, the proper amount of water is applied directly to the root system at a frequency which will lead to a high level of tree performance. Fertilization through drip irrigation provides an opportunity to optimize fertilizer application.

    Continuing research initiated at the Western Agricultural Research Center in 1986 has shown that drip irrigation is an effective, practical method of K application to tart cherries. Potassium deficiency was corrected in the first season of K application. However, in addition to increasing foliar K levels, higher rates of K resulted in a slight but significant decrease in Ca and Mg. The suppression of Ca and Mg uptake by K has been well documented, but it may be intensified in drip irrigation because fertilizer application is concentrated in the root zone.

    Choice of fertilizer material is also more important in K application through drip. The sensitivity of stone fruits to chloride is well documented, so we felt it was important to evaluate several sources of K, including KCl, for application through drip. Overall, our observations raise the question of long-term nutrient interactions when a single nutrient such as K is applied, and indicate a need to define balanced nutrient management through drip irrigation.

    Analysis of xylem sap was found by Dr. Nellie Stark of the U. of Montana Forestry Dept. to be an important tool in determining nutrient status of forest trees. This approach has not been explored extensively for tree fruits, but our preliminary work shows that it is physically feasible. Xylem sap analysis could provide additional insight into K nutrition which incorporated into an ongoing experiment. Xylem sap analysis done in the spring would detect immediate nutrient uptake by the plant, while the standard leaf analysis performed the previous August would reflect the nutrients which had been translocated into the leaf during the growing season. Antagonism between nutrients for root uptake should be very evident when observed by xylem sap analysis. We think that Xylem say analysis, when combined with yield data and standard foliar analysis, will add new dimensions to management of K fertilization.