BORON DEFICIENCY AND TOXICITY IN CROPS GROWN ON SPHAGNUM PEAT SOIL

Abstract

Eight crops were grown in greenhouse experiments on limed and fertilized sphagnum peat soil treated with various rates of borax. All crops, including beans and potatoes which have low requirements, gave marked response to borax when none was present in the chemicals used for correcting soil acidity. Commercial lime apparently provided sufficient boron as an impurity to reduce the response considerably.Boron levels accumulating from successive applications were toxic to sensitive crops like oats and beans, only when heavy rates had been applied. With cabbage, a tolerant crop, the heaviest rate of 600 pounds/acre, applied over a 4-year period, gave no indication of toxicity.Boron deficiency was alleviated and maximum crop yields were obtained at water-soluble soil boron concentrations ranging from 1.5 p.p.m. for beans to 2.8 p.p.m. for lettuce. Toxicity symptoms were apparent at soil levels extending from 4.8 p.p.m. for oats to > 11 p.p.m. for cabbage.Minimum sufficiency concentrations in the plant tissue varied from 12 p.p.m. in beans and potatoes to 32 p.p.m. in spinach. The lowest values associated with toxicity extended from 105 p.p.m. in oats to > 200 p.p.m. in cabbage.