Mwaipaya, Anyosisye Muyaba Aggrey (1996) Influence of Maize (Zea Mays L.) and Bean (Phaseolus Vulgaris L.) Row Arrangement, Maize Intra-Row Spacing and Bean Sowing Date on Combined Yield When Intercropped. Masters thesis, University of Zambia.
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Abstract
Recently, interest in intercropping studies as a potentially beneficial system of food production in the , tropics has increased. It arises from the realization that monocropping, which involves high capital requirements for machinery and inputs, is too expensive for small scale subsistence farmers, who use diverse mixed crop production strategies and simple technology. As a result of low crop management levels in the production of cultivars with low yield potential, crop yields are generally low. Subsistence farmers make up large proportions of the population in less developed countries of the tropics (World Almanac and Book of Facts, 1986). Furthermore, human populations in the tropics are increasing at such high rates that food deficits are becoming ever more threatening (Food and Agricultural Organiqation of the United Nations, 1984). Therefore, an urgent need exists for research to identify the best ways of exploiting the diverse crop species occurring in tropical environments. Improving the locally popular polycultures by modifying crop canopies, and subsequently the size and shape of land area available for growth to individual plants, are some of the practical possibilities to increase yields. In this study, intercropping is defined as the production of more than one crop in separate rows on a unit of land area, either sown simultaneously or growing together during the major part of their growing periods. It fits thewidespread polyculture food production strategy of resourcepoor farmers in the tropics, especially where arable land and capital are limiting, but where labor is abundant and cheap (Dalrymple, 1971). It is likely to continue being important in the foreseeable future, because of the possibility that it can provide yield advantages compared to sole cropping (Dalrymple, 1971; Norman, 1974; Okigbo and Greenland, 1975). A major cause of yield advantages, and the only one for which there is much evidence to date, is better use of growth resources in intercropping (Kasanaga and Monsi, 1954; Osiru, 1974; International Rice Research Institute, 1975; Crookston and Kent, 1976; Lakhani, 1976). One form of advantage provided by intercropping is higher yields in a given season. Fisher (1976b) reported a clear case of substantial yield advantage in a maize/bean (Zea mays L.) trial at three locations in East Africa. Another alternative advantage is greater stability of yield over different seasons. This is particularly important to subsistence farmers with limited production resources. However, there is limited research evidence to document this form of advantage in practice. It is for this reason that, from evidence of other experiments in different seasons, Fisher (1977) questioned whether greater stability occured if moisture was limiting. Nonetheless, the basis for greater stability of yield over different seasons is that if one crop fails of grows poorly, the other component crop, or trops, can compensate.In addition, there is the possibility of better control of weeds, other pests and diseases. Where a more competitive community of crop plants is provided by intercropping, either in space or time, better weed control, is possible than in sole cropping (Litsinger and Moody, 1975; Rao and Shetty, 1977). Indeed, many instances of better pest and disease control have been reported (Aiyer, 1949; Batra, 1962; International Rice Research Institute, 1972, 1975; Nickel, 1973; Finlay, 1974; Pinchinat et aI, 1975; Baker and Norman, 1975; Crookston and Kent, 1976; Raheja, 1977). Other possible causes of yield advantages in intercropping have also received some research attention. A more continuous leaf cover may give better protection against erosion (Dennison, 1~56; Siddoway and Bonnett, 1975). One crop may provide physical support for another (Aiyer, 1949), and also one crop may provide shelter for another (Rathke and Hegstrom, 1975). Nonetheless, more needs to be known about the response of crops in intercropping situations if optimum polycultures for the tropics can be fully developed and high crop yields sustained. Factors needing research attention are many and complex. They include compatibility of different component crops and crop genotypes under different plant populations and spatial arrangements, relative sowing dates, and requirements for light, moisture, nutrients, herbicides, pesticides etc. Whereas local preferences for specific intercrops vary with location and dietary needs, yieldimprovements can be made by replacing traditional cultivars with properly adapted and genetically higher yielding types. In each case optimum plant populations and spatial arrangements have to be carefully determined, so that excessive competition for light, moisture and soil nutrients, which would tend to reduce yields, does not occur. Where canopies of component crops differ, relay sowing may minimize competition for light. Plant population, spatial arrangement and relative sowing times are fundamental to all considerations of crop competition for growth resources. They deserve a detailed study. The main objective of the study was to investigate the effects of the dominant crop (maize) and the dominated crop (bean) row arrangements, maize intra-row spacing and bean planting dates on com~ined grain yield in intercroppping. In addition to measuring main effects, a secondary objective was to measure effects of factor interactions between treatments. It was deliberately intended to compare the effects of these factors on combined grain yield, with equal precision, to enable ranking of their relative importance. It was the experimenter's wish to estimate the magnitude of the responses and in what direction they indicated. Specifically, it was to determine if there exist any significant differences in crop responses to cropping systems, to crop row arrangements, to maize intra-row spacings and to bean planting dates. If so, are the responses positive or negative, and of what magnitude?
| Item Type: | Thesis (Masters) |
|---|---|
| Subjects: | S Agriculture > S Agriculture (General) |
| Divisions: | Africana |
| Depositing User: | Geoffrey Obatsa |
| Date Deposited: | 13 May 2019 13:03 |
| Last Modified: | 13 May 2019 13:03 |
| URI: | http://thesisbank.jhia.ac.ke/id/eprint/9197 |
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