Nitrogen Relationships of Three Tropical Forage Legumes in Pure Stands and in Grass Mixtures1
- A. S. Whitney,
- Y. Kanehiro and
- G. D. Sherman2
The capacities of three tropical forage legumes to fix atmospheric N and to transfer fixed N to two associated grasses were evaluated over a 12-month period under continuously moist climate in Hawaii. Desmodium canum, Centrosema pubescens and D. intortum were grown alone and in combination with napier grass (Pennisetum purpureum) and pangola grass (Digitaria decumbens) in polyethylene-lined plots filled with fresh volcanic cinders.
The grasses averaged 4,400 pounds DM/acre, and the legumes yielded on the average as follows: D, canum 3,530, C. pubescens 6,720; and D. intortum 16,710 pounds/acre. Forage N yields plus root N levels indicated that N fixation by D. canum averaged less than 85 pounds N/acre, and that no transfer of N from D. canum to either grass occurred. C. pubescens fixed 240 pounds N/acre in pure stand and about 110 pounds N when grown with grasses. Some transfer of N from centro to the grasses was noted during a long (6-month) growing period, amounting to 6–11% of the N fixed during that period. Intortum fixed 340 pounds N/acre in 12 months, and 5% or less of this was transferred to the associated grasses.
The nitrogen transfer observed apparently involved N released by both the aerial and sub-aerial portions of the legume plants.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © . .