Soil and foliar characterization for Prosopis clones on sites with contrasting productivity in semi-arid South Texas.
Following greenhouse studies of Prosopis spp., a thornless P. alba clone from California was grown at 2 non-irrigated field sites in Texas, USA. At Kingsville (682 mm rainfall, soil a fine-loamed Hidalgo series, Typic Calciustoll) it produced 21.7 dry t/ha in its third growing season, while at Zachry Ranch (560 mm rainfall, with fine-loamed Copita series, Ustollic Calciorthid) it only produced 3.22 t/ha. These differences suggested that fertility as well as rainfall must have limited productivity. Field foliar concn. of N, P, K, Ca, Mg, Na, Fe, Mn, Zn and Cu were compared with previously established sufficiency rates of these nutrients. Based on foliar analyses, only Cu would have been limiting at Zachry Ranch, whereas based on soil standards for maize, P, Fe and Zn would have been. Foliar P, K, Na, Fe, Mn, Zn and Cu were highly correlated with soil silt content, and significant negative correlations occurred between Olsen's test for available soil P and every foliar nutrient except Ca and Mg. With such discrepancies between leaf and soil diagnostic criteria, the author cautions against basing fertilizer recommendations for tree legumes on standard soil tests.