Phosphorus and micronutrient sources for potato

Potatoes(Solarium tuberosum L.) were grown on two sites of St. Johns’ fine sandy soil (sandy, siliceous hyperthermic Typic Haplaquod) during 1980 and 1981, to evaluate the effects of four P sources and four micronutrient sources on crop production. Mehlich-I (0.05 M HC1 + 0.025 M H₂S0₄) extractable Cu (0.1 to 0.2 ppm), Mn (1.0 to 1.4 ppm), and P (8 to 15 ppm) were considered low. In both seasons, tuber yields were increased with an application of P. Yields were significantly lower with diammonium phosphate (DAP) than with liquid poly-P, liquid ortho-P or triple superphosphate (TSP) P sources. In both seasons, application of Cu, Fe, Mn, Zn, B and Mo did not increase yield over treatment without micronutrients added. Plant-leaf and shoot-tissue P concentrations were increased by the application of P and were higher with DAP than with the other P sources. Micronutrient applications decreased leaf and shoot P concentrations and increased Zn concentrations in one of the two years. Applications of P increased the soil Mehlich-I extractable P and Zn and micronutrient applications increased Cu, Zn, and Mn. Increases in extractable P and Zn were greater with DAP and TSP than with liquid poly-P and ortho-P. Soil Cu increases were greater with frit and sulfate than with chelates and oxide micronutrient sources, Zn was lower with chelates than with the other three sources, and Mn concentrations were highest with sulfate, lowest with frit, and intermediate with chelate and sulfate micronutrient sources.