Soil Characteristics Related to Production on Subclover-Grass Range

Abstract

In northwestern California moisture is usually not limiting for range production during the annual winter-spring growing season. It is, therefore, important to understand how other site factors, both physical and chemical, affect range production. Ridge regression analysis and simple correlations were used to evaluate range production as related to site slope and elevation; soil depth, texture, bulk density, water holding capacity, and pH; and several chemical measures of soil fertility including available P and S, exchangeable cations, total N and S, and organic matter. Subclover (Trifolium subterraneum L.) - grass production was measured at 17 typical range sites for 4 fertilizer treatments: P0S0, P300S0, P0S90, P300S90 (subscripts = kg/ha). When no fertilizer was applied, soil pH and available P appeared to be the 2 variables most closely related to yield. Forage production increased when P and S fertilizers were applied. When P was applied, exchangeable soil K was the most important variable related to yield; and when S was applied, available P was the variable most closely related to production. When P and S were applied together, available P and K were most closely related to yield. While there was generally a striking response to applied S, our measures of available soil S were poorly related to production.