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University of Nebraska - Lincoln (1988)

Maximizing cereal crop production in Botswana during years of drought

Youngquist Joan B

Titre : Maximizing cereal crop production in Botswana during years of drought

Auteur : Youngquist Joan B

Université de soutenance : University of Nebraska - Lincoln

Grade : Doctor of Philosophy (PhD) 1988

Résumé
Drought severely compounds limitations to crop production faced by the subsistence farmer in semi-arid regions of Africa. The objectives of this experiment were to determine yield components associated with yield stability of grain sorghums (Sorghum bicolor), fodder potentials of cereal crop residues, and cropping system effects on yield of component species in years of drought. Eight grain sorghums, three forage entries (S. almum and S. bicolor x S. sudanense), pearl millet (Pennisetum americanum), cowpea (Vigna unguiculata), and four intercrop combinations were grown in 24 environments where seasonal rainfall was $<$350 mm. The highest mean grain yields were produced by sorghum/millet intercrop (1.309 Mg ha$\sp-1$), and the highest mean stover yields by high density populations of S. almum (5.782 Mg ha$\sp-1$). Grain yield stability of grain sorghums was primarily due to maintenance of head number and seeds per head in poorer environments. Digestibilities of stover were greater than 50% and crude protein values between six and eight percent. Of concern were deficient P levels compounded by high Ca and Mn levels in crop residues. This mineral imbalance could lead to bone abnormalities and reduced fertility in ruminants. Hydrocyanic acid potentials exceeded toxic levels in grain sorghum leaf tissue. A yield advantage due to intercropping as compared to monoculture was not demonstrated for grain or stover yield. Pearl millet maintained grain yield in intercrop by increasing head number to compensate for lower plant densities. Lower sorghum yields in intercrop were due to fewer heads and fewer seeds per head. Cowpea yields in intercrop were lower than in monoculture due a reduction in pods per plant. The results suggest that specific cultivars can be developed for low or for high yielding environments, and that stover mineral content should be monitored. Further research is needed to determine optimum plant densities of compatible species in intercrop. ^

Présentation

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