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Accueil du site → Doctorat → États-Unis → 1987 → Cowpea/sorghum intercrop systems in semi-arid Botswana : Assessment of yield, growth, and water use

Colorado State University (1987)

Cowpea/sorghum intercrop systems in semi-arid Botswana : Assessment of yield, growth, and water use

Conniff, Karen Lynn

Titre : Cowpea/sorghum intercrop systems in semi-arid Botswana : Assessment of yield, growth, and water use

Auteur : Conniff, Karen Lynn

Université de soutenance : Colorado State University

Grade : Doctor of Philosophy (PhD) 1987

The predominate influence of rainfall on agriculture in Botswana presents a challenge to both farmers and researchers. Rainfall amounts are low and distribution is erratic, averaging 315 mm during the cropping seasons of 1984-85 and 1985-86. Development of a stable sorghum/cowpea cropping system in these unpredictable and often harst conditions would benefit farmers. Interactions between component crops, cropping systems, and plant population densities can be critical to successful intercropping when water is the greatest limiting resource. Six intercropping experiments were conducted in semi-arid Botswana from 1984 to 1986. Supplemental irrigation was used in two experiments to simulate "non-drought" environmental conditions. Differences in crop and cropping systems performance were evaluated using crop yields, monetary returns, land equivalent ratios, yield stability, growth measurements, and water use relationships. Sorghum (Sorghum bicolor (L.) Moench) and cowpea (Vigna unguiculata (L.) Walp) were sole cropped and intercropped using two intercropping systems, alternate row and within row, and two different cowpea varieties at three population densities. Significant cowpea and sorghum yield differences were obtained between cowpea varieties and cowpea density levels, but not between intercrop systems. Mean land equivalent ratio (LER) across all environments gave an intercrop advantage of 1.16 over sole cropping. ER-7/sorghum contribution to mean LER was 1.36 and Blackeye contribution to LER was 0.98 over the range of environments. Economic returns for the intercrops were greater than sole crop returns at 4 out of 6 locations. Crop water use was measured at two experimental sites, irrigated and rain fed, to observe crop water use patterns of different intercrop systems. Crop evapotranspiration, soil moisture depletion, and basal crop coefficients (Kcb) were calculated for sole and intercropped cowpea and sorghum. Strong negative correlations with yield were obtained between soil moisture deficits at flowering for cowpea and at booting for sorghum. Maximum Kcb for 2 cowpea varieties, sorghum and their intercrops varied in time. Based on the number of days to reach maximum Kcb, there is evidence that in order to reduce crop water stress and thus improve yield under low rainfall conditions, intercrop components should be selected based on a staggered time to peak basal crop coefficient.

Présentation (PROQUEST)

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