Impact of Gliricidia sepium and Cassia spectabilis hedgerows on weeds and insect pests of upland rice

Published source details MacLean R.H., Litsinger J.A., Moody K., Watson A.K. & Libetario E.M. (2003) Impact of Gliricidia sepium and Cassia spectabilis hedgerows on weeds and insect pests of upland rice. Agriculture, Ecosystems & Environment, 94, 275-288.
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This study is summarised as evidence for the following.

	Action	Category
	Use alley cropping Action Link
	Incorporate plant remains into the soil that produce weed-controlling chemicals Action Link

Use alley cropping

A randomised, replicated, controlled trial in 1987-1988 at two sites in Mindinao, Philippines (MacLean et al. 2003) found that the weight of grass and broadleaved weeds averaged 3.4-86.1 g/m² and 0.7-51.3 g/m², respectively, in alley cropped plots of rice Oryza sativa compared to 1.2-16.4 g/m² and 2.6-35.6 g/m² in conventional plots. Grass weight was greater in alley cropped plots than controls at a site with low soil fertility and high erosion. Alley cropped plots had 0.8-25.8 rice seedling maggot Atherigona oryzae eggs/m crop row while conventional plots had 0.8-13.6 eggs. White grubs (Scarabaeidae) appeared less abundant in alley cropped than conventional plots in 1987 (8.5-11.5 larvae/5 m crop row vs. 29.8 larvae at one site, 0.3-0.6 vs. 2.0 larvae at a second site) but numbers were similar between these treatments in 1988. Stem borer damage resulted in 1.7-9.5 deadhearts (dried central rice shoots)/m of row in alley cropped plots compared with 0.78-16.3 deadhearts in conventional plots. Rice stover and grain yields averaged 0.66-6.27 t/ha and 0.09-1.48 (respectively) in alley cropped plots compared with 2.41-3.17 t/ha and 0.23-1.15 in conventional plots. Rice was planted in alleys between gliricidia Gliricidia sepium and cassia Cassia spectabilis hedgerows. Hedgerows followed contour lines and were spaced 3-6 m apart. Twenty-four alley crop plots (across two 0.6 ha sites) were compared with two plots receiving conventional farmers’ practice. Alley crop plots (grouped in this summary) comprised mulched, green manured, mulched and green manured, or non-amended treatments.
Incorporate plant remains into the soil that produce weed-controlling chemicals

A randomised, replicated, controlled trial in 1987-1988 at two sites in Mindinao, Philippines (MacLean et al. 2003) found that weight of broadleaved weeds was higher in plots of rice Oryza sativa amended with gliricidia Gliricidia sepium (averaging 3.8-51.3 g/m²) than non-amended control plots (1.9-20.5 g/m²) in 1988. No difference was found in 1987. Weight of grass weeds was similar between treatments in 1987 and varied between study sites in 1988. Amended plots had more rice seedling maggot Atherigona oryzae eggs (2.7-15.5 eggs/m crop row) than control plots (0.8-8.8 eggs) at one site in 1987-1988, but numbers were similar between treatments at the second site (0.4-25.8 eggs). White grub (Scarabaeidae) numbers were similar between amended and control treatments except at one site in 1988, when they were more abundant in the amended plots (1.7 vs. 1.0 larvae/5 m crop row). Stem borer (Lepidoptera) damage was greater in amended plots (2.4-12.3 vs. 1.4-5.5 deadhearts/m of row) in one of two sites in each year, but otherwise similar. Rice grain yields were higher in amended (0.79-1.51 t/ha) than control (0.09-0.83 t/ha) plots. Rice was planted between hedgerows at two 0.6 ha sites and amended with gliricidia (cut from hedgerows) or left without amendment. Treatments were replicated six times.