Phosphorus Placement for the Establishment of Alfalfa and Bromegrass1
- R. W. Sheard,
- G. J. Bradshaw and
- D. Lawrence Massey2
Efficient production of forage species is greatly hindered by inadequate stands. The results from a greenhouse and two field experiments using 32P-labeled, monocalcium phosphate showed increased P uptake from fertilizer placed five cm directly below surface sown seed of alfalfa (Medicago saliva 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.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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