Forage tree legumes. IV. Productivity of leucaena/grass mixtures

A field experiment was conducted in a wet tropical environment (Ciawi, West Java, Indonesia) to assess the forage yields of mixtures of leucaena and grasses over a 1 year period in plots which had been established 2 years earlier. The tree legume Leucaena leucocephala cv. Cunningham (plant density 1 m x 0.5 m), cut at either 30 cm or 100 cm, was interplanted with either a short grass (Setaria sphacelata var. splendida) or a tall grass (Pennisetum purpureum). Mineral nutrients were non-limiting. Highest leaf production was in the setaria monoculture (20.8 t ha-l yr-l) and the low-cut leucaena/setaria mixture (18.5 t ha-l yr-1), with the grass dominating production (> 88%) in the latter because of the ability of setaria to gain preferential access to light penetrating between the rows of leucaena early in each growth period. Leucaena shoot production in the low-cut leucaena treatments was reduced from a mean of 8.8 t ha-1 yr-1 in the monocultures to 1.5 t ha-l yr-1 in the mixtures. For the high-cut leucaena treatments, grass leaf yields were lower from the mixtures than from the monocultures but leucaena shoot yields were only reduced from monoculture yields in the mixture with pennisetum. The mixture of setaria and high-cut leucaena produced a considerable yield of setaria leaf (6.2 t ha-1 yr-l) with no reduction in leucaena leaf yields and intercepted a significantly greater percentage of total incident light (64%) than the other three mixtures (42-42%).