Subsidiary crops is a generic term for all crops which are grown primarily for their ecological services. They are recommended as an important part of an environmentally-sustainable system of crop production improving soil fertility and structure, suppression of weeds, pests and disease thereby reducing the need for mineral fertilizers, herbicides fungicides and insecticides (Teasdale 1998; Masiunas, 1998). The other advantages of subsidiary crops are the enrichment of the soil in organic matter (Koch, 1990) and improvement of some physical properties such as soil structure moisture retention and reduction of soil compaction (Nicholson and Wien, 1983; Wiles et al., 1989). Nitrogen-fixing plants are particularly beneficial as they ‘fix’ atmospheric nitrogen into a form that is readily available to the crop. On the other hand subsidiary crops compete with cash crops for light, moisture and nutrients and for this reason often reduce the crop yield (Henning, 1998).
Examples of the beneficial effects of subsidiary crops include: • Suppressing weeds • Protecting soil from rain or runoff • Improving soil aggregate stability • Reducing surface crusting • Adding active organic matter to soil • Breaking hardpan • Fixing nitrogen • Scavenging soil nitrogen • Suppressing soil diseases and pests
Subsidiary crops comprise:
- Henning V. 1998. Wirkung von Untersaaten in Sellerie und Wirsing auf den Ertrag. Gartenbauwissen 63(1), 7–14.
- Koch W. 1990. Untersaaten in Herbst-Gemüse-Kulturen. Gemüse 12, 561–564.
- Nicholson A.G., Wien H.C. 1983. Screening of turfgrass and clovers for use of living mulches in sweet corn and cabbage. Journal of the American Society for Horticultural Science. 108: 1071-1076.
- Teasdale, J.R. 1988. Weed suppression by hairy vetch residue. Proceedings of the Northeastern Weed Science Society 42:73.
- Wiles L.J., Wiliam R.D., Crabtree G.D., Radosevich S.R., 1989. Analyzing competition, between living mulch and a vegetable crop in an interplanting system. Journal of the American Society for Horticultural Science. 114, 1029–1034.