15. Effects of two underseed species, medicago polymorpha l. And scorpiurus muricatus l.,on the yield of main crop (durum wheat) and subsequent crop (teff) under humid moisture regimes in Ethiopia.
J. Agronomy & Crop Science, 168, 1992, pp. 249-254
The objective of the study was to record quantitative effects of two underseed species - Medicago polymorpha L. and Scorpiurus muricatus L. - on the shoot and grain dry matter of main crop (competitive effects) and succesive crop (residual effects). Both species are abundant annual leguminous weeds in the Ethiopian highlands.
Depending on the site factors, agronomic and technical measures at hand, mixed cropping systems may serve widely differing purposes: In vast areas of the Ethiopian highlands (>1500 mm NN) which are mainly characterized by semipermanent cropping systems they could especially contribute to erosion control and to restoration or stabilization of soil fertility.
The highlands are exposed to a considerable population density and its continuous increase leads to declining proportions of pasture fallows and to the cultivation of steep slopes which in turn drastically increases the risk of soil erosion.
Apart from a lowering of soil erosion risks and a preservation of the soil's N- and C-pool leguminous underseed species are suggested to increase water permeability due to an improved soil structure.
Two successive greenhouse trials have been carried out in two factorial designs with three replications.
The leguminous weed species which are widely distributed in annual crops of the Ethiopian highlands have been studied with varying coverage with regard to their suitability as underseeds and with wheat (Triticum turgidum [L.] Thell. var. durum [Desf.] MacKey) as a main crop. The competitive effects of Scorpiurus muricatus L. on the grain yield of wheat were smaller than those of Medicago polymorpha L. (-14.1% and -23.6% respectively, compared with the underseed free control) which is mainly ascribed to differences in their speed of development and shoot height. The residual effects of the underseed's root masses on the grain yield of the successive teff crop (Eragrostis tef [Zucc.] Trotter) were significantly higher with Scorpiurus muricatus (+99.3%) than with
Medicago polymorpha (+63.6%).
Leguminous underseed species adapted to the above described environments should be able to perform in waterlogged sites. This could possibly also have some ameliorative effects, if the combination of main crop with underseed species leads to an increased evapotranspiration rate compared with single crop cultivation and if it improves soil aeration through increased soil organic matter content.
Per se S. muricatus fits better as an underseed partner than M. polymorpha, due to its lower competitive power and due to its even stronger positive residual effects on the successive teff crop.
Moreover it was found out by inquiries of Ethiopian farmers that both species serve as a feed for livestock and that S. muricatus is preferably grazed on harvested fields.
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Latin America, survey, Honduras, intercropping, beans, sorghum, maize, environment, management practices, on-farm research, rainfall, temperature, soils, planting, cultivars, CATIE
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