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Agronomy Journal Abstract -

Fertilizer Effects on Crop Removal of P and K in ‘Coastal’ Bermudagrass Forage1


This article in AJ

  1. Vol. 77 No. 1, p. 110-114
    Received: Feb 17, 1984

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  1. J. L. Day and
  2. M. B. Parker2



In 1959, an N-P-K ratio of 9.1-1-3.8 (4-1-2 N-P2O5-K2O ratio) was proposed as the proper nutrient balance for fertilizing ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.] for forage, but nutrient removal in forage was not taken into consideration with this ratio. The purpose of the study was to determine fertilizer effects on removal of P and K in ‘Coastal’ bermudagrass forage using increments of a fixed N-P-K ratio and high rates of P and K over a range of N rates. An established sod which had not received fertilizer for at least 5 years was selected for the 3-year study. The soil was a Fuquay loamy sand (loamy, siliceous, thermic arenic Plinthic Paleudult) which was medium in P and low in K. Annual treatments for the first 2 years were 84,168,336, and 672 kg N ha−1 applied with P and K in a 9.1-1-5.7 N-P-K ratio (4-1-3 N-P2O5-K2O ratio). In the 3rd year 73.6 kg P ha−1 and 420 kg K ha−1 were applied uniformly at all N rates. The 9.1-1-5.7 N-P-K ratio supplied inadequate amounts of P and K to compensnte for crop removal at the lower fertilizer rates but were excessive at the higher fertilizer rates. The N-P-K ratio required the 3rd year to supply P and K equivalent to that removed in the forage ranged from 6.4-1-6.5 for the 84 kg N ha−1 treatment to 14.4-1-7.9 for the 672 kg N ha−1 treatment. This study indicates that the use of regression equations for determining P and K needs for Coastal bermudagrass is a more suitable method than the N-P-K ratio method.

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