Phosphorus Placement for the Establishment of Alfalfa and Bromegrass 1

Efficient production of forage species is greatly hindered by inadequate stands. The results from a greenhouse and two field experiments using 32 P‐labeled, monocalcium phosphate showed increased P uptake from fertilizer placed five cm directly below surface sown seed of alfalfa ( Medicago sativa L.) or bromegrass ( Bromus insrmis L.). Dispersing the P throughout the soil volume, localizing the P on the soil surface, or moving the band laterally from a position directly below the seed, all decreased fertilizer P uptake, and as a result reduced the weight of individual seedlings of both species from that obtained where the fertilizer P was placed directly below the seed. Fifteen days after seeding, alfalfa and bromegrass seedlings emerging directly over the fertilizer band obtained 50 to 56% of their P content from the fertilizer. Only 2.5 to 6.5% of total P was obtained from the fertilizer where the band was located 3 cm laterally, and none from bands located at a 6 or 9 cm lateral displacement. The root system of the two species did not reach the 9 cm band until 29 days after planting. Fifty days after planting, 10 to 14% of the P was derived from the fertilizer band in plants grown with a 9‐cm lateral displacement of the fertilizer band, in contrast to half the P absorbed from the fertilizer by plants grown directly over the fertilizer band. The increased utilization of fertilizer P by both grass and legume species at a very early stage in growth when the fertilizer is banded directly below the seed will result in more vigorous seedlings, and greatly reduce the hazards of forage establishment.