Studies in Mixed Cropping. I. Seasonal Differences in Relative Productivity of Crop Mixtures and Pure Stands in the Kenya Highlands

Abstract

An experiment is described in which the productivity of maize-bean and maize-potato mixtures in alternate rows was compared with pure stands of the component species in four cropping seasons. In seasons with low rainfall, yield from the mixtures fell short of that from pure stands, but in one exceptionally wet season a yield advantage was found for maize-bean mixtures. The poor performance of mixtures in low rainfall seasons appeared to result from large reductions in maize yield attributable to competition from the potato or bean. In the one high-rainfall season, no such reduction in maize yield occurred. An implication of these findings for farming systems with mixed cropping is discussed. Webster and Wilson (1966) concluded that in most experiments on mixed cropping in the tropics, more than one acre of pure stand was required to produce the yield of one acre of the mixed crop and concluded that for the tropical small-scale farmer, there was no advantage to be gained by replacing the traditional practice of mixed cropping. Reports from Africa appearing since 1966 have generally substantiated Webster and Wilson's conclusions. Willey and Osiru (1972) found that yields of mixtures of maize and beans were up to 38% greater than could be achieved from pure stands in an area of Uganda with a short but fairly reliable rainy season and the advantages were even greater with mixtures of beans and sorghum (Osiru and Willey, 1972). These results are important because the yield of all pure stand comparisons was high, thus confounding the opinion that mixed cropping is only of value at low levels of crop management or fertility. In a climate with a long rainy season in N. Nigeria, Andrews (1972) showed total yield advantages of up to 80% from mixtures of sorghum with millet or cowpea. This paper presents the yield results of trials carried out over four seasons with maize-bean and maize-potato mixtures in alternate rows in the Highlands of Kenya. The area has two rainy seasons per year; the long rains usually begin at the end of March, continue until the end of May and are followed by a cool, cloudy, dry period and the short rains begin in late October, continue until the end of the year and are followed by a warm, bright dry season. Both seasons are highly unreliable, both in the quantity of rain and its duration. MATERIALS AND METHODSThe experiment was located at the Kabete Field Station (i° 15'S, 36 0 44'E) of the Faculty of Agriculture, University of Nairobi at an altitude of 1815 m. 12

Sunflower–Soybean Intercrop Productivity under Different Water Conditions and Sowing Managements

“…In agreement with Fisher (1977), the relative grain yield advantage of intercropping was higher as water availability increased during the growing season (Fig. 6).…”

Analysis of maize–common bean intercrops in semi-arid Kenya

“…Maize-bean intercrops commonly fail to show a yield advantage in semi-arid areas of Kenya (Nadar 1983;Nadar & Faught 1983), or elsewhere in Kenya in seasons of low rainfall (Fisher 1977), so our data from the short rains are not exceptional. Stewart & Kashasha (1983) have stated that no benefit from mixed cropping can be expected in areas receiving < 300 mm of rain per season.…”

Comparing the Feasibilities of Pearlmillet‐Based Intercropping Systems Supplied with Varying Levels of Nitrogen and Phosphorus

“…LER, as de®ned by Willey and Osiru (1972), is the total land area required under single cropping to give the yields obtained in the intercropping mixture. The LER values were calculated as per the formula given by Fisher (1977). For a valid comparison of yield data, yields of intercrops were converted into pearlmillet grain equivalents based on market prices at the time of harvest and added to the PM yield to obtain the relative yield potential of dierent intercrop combinations.…”