Yield response curves of Dactylis glomerata L. to addition of phosphorus, nitrogen, potassium, and lime on an xeric heath soil of Tierra del Fuego

Abstract

We studied the response curves of Dactylis glomerata to addition of nitrogen (N), potassium (K), and lime in presence of a range of added phosphorus (P) on an acid xeric heath soil (pH 4.3) of Tierra del Fuego (Argentina). The heath community developed on the soil has dominated by a 50% of cover of an evergreen dwarf shrub (Empetrum rubrum) of very little forage value. Addition of P alone or combined with any of amendments increased significantly the growth of Dactylis. In contrast, absence of P, even supplying 50 ppm of N or K, no increase in growth of Dactylis was detected. This suggested that P was the most important nutrient limiting the growth of forage plants in this heath soil. By fitting response curves, we studied three different aspects: the maximum and the minimum yield approached, and the slope of the response curve to reach the maximum yield. Increasing added P, the maximum yield reached was greatest for N addition, lowest for lime, and intermediate for K and P alone. The minimum yield (absence of added P) did not differ among treatments. Consequently, all response curves were fitted using a common value for the intercept. In addition, liming the soil in presence of added P decreased the slope of the response curve to reach maximum yield. This was mostly ascribed to a decrease of the effectiveness of added P by sorption of P onto the surface of lime applied.