Poor grain sorghum production after rice improved by phosphorus banded near seed

Replicated field trials conducted in Colusa and Glenn Counties demonstrated that poor growth and production of grain sorghum (milo) the first year after rice may be improved by phosphorus banded near the seed. Treble super phosphate, 11-48-0, 8-24-0, and 10-50-0, improved seedling growth and grain yields when placed with or below seed. After four or more years of continuous rice, P banded near sorghum seed provided economic returns and striking seedling growth responses. Sorghum trials after only two years of rice showed fewer seedling growth differences and variable yield responses to banded P. Soil analysis using critical levels developed on soils with no rice history could not be used to successfully predict yield responses to banded P after rice. Further studies are necessary to answer such questions as: (1) Why are some soils P deficient after rice? (2) How can we predict situations where banded P is effective? (3) What are the optimum rates of P for highest economic returns?