ILEIA Newsletter • 3.1 • May 1987
Cover crops on acid soils: experiences in the humid tropics
Kurniatun Hairiah; Meine van Noordwijk
In
the humid tropics, the leaching of nitrogen and other nutrients to the subsoil
may occur throughout the growing season. Mixed cropping systems of shallow and
deep rooted crops can therefore be advantageous. On acid soils maize may
develop only shallow root systems; combination with deep-rooted cassava gives a
better nutrient utilization than a monoculture.
In practice these requirements can seldom, if ever, be met by one species. Some experience with various cover crops is presently being obtained in Lampung, S. Sumatra, where Imperata cylindrica forms the major weed problem. Research is being conducted within the framework of a joint research project on nitrogen utilization between our institutes, sponsored by EEC and Dutch directorates of developmental cooperation. Remarks on the general performance of six cover crops is presented in the table; the root system is shown in the accompanying figure. Comparable results for S.E. Nigeria have been reported previously.
Species with creeping stems and fast initial development, as illustrated by Mucuna and to a lesser degree Calopogonium, give good initial weed control. The erect Crotalaria species do not directly cover the soil but may shade out Imperata in the longer run. Mucuna and Calopogonium show a shallow root system, Crotalaria roots go deeper. The other species develop too slow to control all weeds initially, but may be interesting because of a deep root development (Centrosema) or good nodulation (Pueraria). Yield effects of cover crops on a subsequent maize crop are currently being investigated.
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