Rate and Placement of Phosphorus for Small Grains 1

THROUGHOUT the United States, the phosphorus fertilizer needs of small grains usually are supplied at the time of seeding. Where forage crops also are seeded with small grain, as is common practice in the northern sections, initial fertilization practices are influenced by the need for supplying nutrients to both crops. In these areas, supplemental topdressing of phosphorus and potassium on leguminous meadow, as well as of nitrogen on grass, often is recommended. A large acreage of fall-seeded small grain is grown in the South. While all phosphorus is supplied at time of seeding, frequently only a portion of the nitrogen is supplied then, with the remainder being topdressed in late winter or early spring. The result is less leaching of nitrogen by winter rains and more efficient use of the applied nitrogen fertilizer. The possibility of delayed application of phosphorus fertilizer for small grains has received little attention. Such a practice, if feasible, would provide alternative means of fertilization. The added flexibility would be advantageous to fertilizer producers as well as farmers. In regard to placement of phosphorus for small grain, it is commonly observed that band placement near the seed is more effective than broadcast application. Prummel (5), for example, found that band placement of phosphorus 2 cm. from the seed was 2.5 times more effective in Holland than broadcasting. Mattingly and Weddowson (3) found greater percent recovery in England from band-applied P at all stages of growth of barley than from topdressed P. The purpose of this report is to present the results of a series of field experiments comparing the placement of different sources of phosphate fertilizers compounded into mixtures.