Maize Composition in Africa.

In spite of using similar improved crop varieties to Latin America, Asia and Europe, Sub-Saharan Africa has only increased its crop yield by about 30% since 1970 in contrast to a 60-90% increase in the aforementioned regions. This study looked at maize hybrid performance and nutrient efficiencies in N depleted fields where maize hybrids have been grown continuously for 5-9 seasons starting in spring 2010 at different N rates ranging from 0 to 160 kg N/ha in Embu and Kiboko, Kenya and in Harare, Zimbabwe as part of CIMMYT’s Improved Maize for African Soils project. Whole-plant and grain nutrient contents were measured at maturity for each hybrid and N rate combination. While N recovery efficiency (NRE) was high at Kiboko and Harare (at times total plant N uptake almost double the amount of N applied), plant internal N utilization (NIE) was low at all three sites (30-40 kg grain/ kg plant N), limiting the resulting yield. In Embu where NRE levels corresponded to that of modern US hybrids (~50-70 %), the low NIE hindered the hybrids’ response to N fertilizer additions. Low NIE suggested that N was not the sole limiting factor for grain yield. Plant P was found to be deficient in the hybrids in Embu and Harare where soil pH was low (<6) and where Al and Fe levels were high. Plant Mg and Zn concentrations were also deficient in Harare. Low Zn uptake corresponded to low soil Zn levels and excessive Fe uptake. Both Mn and Al were excessive at all three sites in the soil, thus impacting the plants’ ability to respond to environmental stresses such as drought and heat stresses. Soil pH needs to be adjusted and water more effectively managed before the yield benefits of hybrids with enhanced nitrogen use efficiency can be realized.

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See more from this Division: C03 Crop Ecology, Management and Quality
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