If upland rice production is to be sustained on sloping land, soil erosion and fertility decline must be addressed. Where soil profiles are deep, hedgerows of Gliricidia sepium and Cassia spectabilis, planted on the contour, reduce soil erosion by promoting terrace formation and overcome fertility depletion by providing nutrient rich biomass. G. sepium and C. spectabilis established by seed survived better than by cuttings. Although increased hedgerow biomass was initially obtained when both species were intercropped, intense competition was observed in established hedgerows. Consequently, mixing both species at high planting density is not recommended as C. spectabilis, a non-fixing legume, may deplete soil-N reserves. In acid soils, biomass production of G. sepium was significantly increased when lime (6 t/ha) was applied. On 18 to 30% slopes, upland rice and maize production improved along fertility and moisture gradients. Rice yields were increased when biomass of G. sepium was incorporated into the soil, up to an optimum level equivalent to 40 kg N/ha. Mulching C. spectabilis increased maize productivity during the drought prone second season. Competition was observed at the hedgerow-crop interface particularly at the upper one as a result of terracing. Although green manuring increased crop yield, broadleaf weeds, seedling maggot, stemborer and blast also increased. Strategies to manage hedgerow biomass that minimize these problems need to be developed.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.41035 |
| Date | January 1992 |
| Creators | MacLean, Richard Havelock |
| Contributors | Watson, A. K. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Plant Science.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001324209, proquestno: NN87909, Theses scanned by UMI/ProQuest. |
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