Boron in the irrigation waters and alkaline calcareous soils of Arizona with particular reference to its effects on plants

Abstract

In a partial survey of Arizona waters, surface waters tested were found to be lower than the accepted toxicity level for most crops. Some of the pumped irrigation water analyzed contained excessive amounts of boron; but in most oases the availability of alternate sources permits blending of waters so that the problem is obviated. Analyses bf plant materials show that a correlation exists between the amount of boron in irrigation water and the amount of boron taken up by the plant.. Foliar toxicity symptoms sometimes are evident Studies were conducted which showed that the amount of boron fixed by a soil is a function of soil texture, as well as the boron concentration of the equilibrium solution with which the soil is in contact. When the, equilibrium concentration of the boron in the two phases was plotted, a linear relationship existed in which the slope of the fixation curves for heavy soils contrasted with that for light textured soils. Data are at hand which indicate that boron fixation is a temporary process, pending percolation of boron-free water through the soil, the release of boron being enhanced when the percolating water has a low pH value. In sand cultures of cotton and sunflower plants grown in media containing a range of boron and lime concentrations, the results were interpreted to best advantage by use of the calcium: boron ratio; this fluctuates widely, as does the yield, when boron is limiting in a soil. Calcium carbonate amelioral to some extent the toxic effect of boron in plants.