ORGANIC AND INORGANIC SOURCES OF PHOSPHORUS ON GROWTH AND PHOSPHORUS UPTAKE IN SORGHUM GENOTYPES

Information about plant responses to different sources of phosphorus (P) is limited. Sorghum [Sorghum bicolor (L.) Moench] genotypes were grown with low levels of organic and inorganic sources of P in nutrient solution and soil to determine the availability of P from different P compounds and to note genotype differences for dry matter yield and P uptake. Plants grown in nutrient solution and soil with organic sources of P (ethylammonium, glyceryl, and phenyl phosphates) produced more dry matter and had higher P contents than plants grown with inorganic sources of P [potassium dihydrogen, calcium (tribasic and pyro), ferric, and aluminum phosphates]. Plants grown with the inorganic sources of P had higher P efficiency values (dry matter produced per unit P taken up) than plants grown with organic sources of P. Phosphorus from organic compounds appeared to be more readily avialable to sorghum plants than P from inorganic compounds. Of the inbred genotypes studied, NB9040 was the most responsible and SC33-9-8-E4, TX415, and CK60-Korgi were the least responsive to low P.