Nitrogen cycling in a pure grass pasture and a grass-legume mixture on a red latosol in Brazil.
1994
Cadisch G. | Giller K.E. | Schunke R.M.
A nitrogen-balance method and a process-orientated approach, comparing a pure Brachiaria decumbens sward with a B. decumbens-Calopogonium mucunoides mixture, were used to discuss the major pathways of nitrogen in improved tropical grazing systems in the Cerrados of Brazil. Both methods predicted a drain of soil N with the pure grass pasture which could be reversed by introducing a legume into the pasture. A legume N fixation of 31-46 percent (depending on legume utilisation) of total sward above-ground nitrogen accumulation (equivalent to 60-117 kg fixed N2 per ha for this system) was considered to be sufficient to sustain the productivity of the system. Management options that increase N2 fixation and efficient N recycling include optimising grazing management (short rest periods to improve legume persistence), adequate stocking rate (to improve litter recycling), use of less palatable legumes (to improve persistence) which are easily decomposed, and alleviation of nutrient deficiencies (especially P).
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