Studies on mixtures of dwarf sorghum and beans (Phaseolus vulgaris) with particular reference to plant population

Abstract

SUMMARYAn experiment is described in which the possible yield benefits of mixing dwarf sorghum and beans were examined under intensive farming conditions. A ‘replacement series’ of pure sorghum, two-thirds sorghum/one-third beans, one-third sorghum/twothirds beans and pure beans was used at four plant populations. A high level of nitrogen was applied to the sorghum to eliminate the effects of nitrogen transfer from the beans.Yields of the mixtures were up to 55% higher than could be achieved by growing the crops separately. As with some earlier maize/beans experiments (Willey & Osiru, 1972), it is concluded that these yield increases must have been due to a greater utilization of environmental resources. It is suggested that the main factors which made this possible were probably the different rooting depths of the two crops and their different growth cycles.In agreement with the earlier experiments, mixtures which consisted of two-thirds sorghum/one -third beans gave greatest yield increases at high populations and also had a higher optimum population than the pure stands. However, no such trends were apparent in the mixtures which consisted of one-third sorghum/two-thirds beans.For both species intra-specific competition was greater than inter-specific competition. In contrast to the earlier maize/beans experiments, the relative interspecific competitive abilities of the species changed with change in the initial proportions of species in the mixtures. In the two-thirds sorghum/one-third beans mixtures the sorghum was the more competitive species, whilst in the one-third sorghum/two-thirds beans mixtures the bean was the more competitive species. Also in contrast to the maize/beans experiments, these relative competitive abilities were not affected by change in theoverall plant population pressure.

Nitrogen transfer and dry matter production in soybean and sorghum mixed cropping system at different population densities

“…These findings are in agreement with those of Osiru and Willey (1972) who reported that when component crops are present in approximately equal numbers, productivity and efficiency appear to be determined by the more aggressive crop, usually the cereal.…”

Yields and nitrogen nutrition of intercropped maize and ricebean (Vigna umbellata [Thumb.] Ohwi and Ohashi)

“…The yield advantage of intercrops is a reflection of a better use of resources than monocultures (Osiru and Willey, 1972;Spitter, 1980;Trenbath, 1986). Nitrogen fixation is undoubtedly one important factor in the advantage of legume/nonlegume intercrops or pasture mixtures (Harper, 1977;Vallis, 1978;Willey, 1979).…”

EFFECT OF MIXED CROPPING ON SOME INSECT PESTS OF BRASSICAS; REDUCED BREVICORYNE BRASSICAE INFESTATIONS AND INFLUENCES ON EPIGEAL PREDATORS AND THE DISTURBANCE OF OVIPOSITION BEHAVIOUR IN DELIA BRASSICAE

“…Competition occurred from direct competition for soil moisture (O'Donnell & Coaker, 1975), plant nutrients and light (Ryan et al, 1980). These effects have been experienced in other mixed cropping situations but the combined yields of the 2 crops can often be higher than those of either crop grown in monoculture (Evans, 1960;Evans & Sreedharan, 1962;Grimes, 1963) mainly due to greater root interpenetration between the crops and more efficient use of incident radiation (Osiru & Willey, 1972;Trenbath, 1974). Further work is required on the agronomy of intercropping brassicas to evaluate the most cost-effective spacings to provide acceptable yields and reduce insecticidal treatments, and on the use of intercropping generally as a cultural method for insect pest management.…”