Integration of grain and forage legumes in citrus plantation grown at different slope gradients [San Jose, Delmonte, Bulacan, Philippines].
1991
Dhakal D.D.
Field experiments on grain and forage legumes integration in existing citrus plantation [in Quimara Farm, San Jose, Delmonte, Bulacan, Philippines] at slopes ranging from 18 to 40 percent were conducted to evaluate its effects on citrus growth, grain and forage yields, soil fertility, and soil losses. Growth and nutrition (leaf analysis) of citrus were not affected by legume intercrops. However, leaf phosphorus tended to decline. Soil moisture depletion was faster with sod than with legume intercrops in pure stands. Grain yields were high during October planting and total biomass in July planting. When intercropped with forages cowpea grain yield was significantly increased with centrosema in October planting but decreased with siratro in July planting. Age of citrus trees did not affect grain yield and biomass of cowpea intercrop in October planting but apparently reduced grain yield in July planting. The number of pods per plant was considerably less with siratro intercrop in July planting. Herbage yield of 786.0 g/m to the second power and 950.0 g/m to the second power at 45 and 60 day-cutting intervals respectively were obtained from siratro in pure stands while only 420.0 and 540.0 g/m to the second power from centrosema pure stands at the same cutting intervals. Cowpea as intercrop decreased herbage yields of centrosema by 37% and 17% in siratro. Centrosema consistently exhibited higher crude protein and fiber contents than siratro in both seasons. Cutting of forages and seedling of cowpea at the peak of the rainy season accelerated soil losses which ranged from 1.5 to 62.5 g/plot of 5 sq.m. Over 87% of total soil loss occurred during seedling to flowering of cowpea. In spite of the removal of 167 to 395 kg N/ha from grain and forage harvest levels of soil pH, OM, P, and K were not affected by legume intercrops. Organic matter content decreased proportionately with degree of soil losses in experimental plots.
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