As in other parts of the humid tropics, acid-related problems are the major constraint to crop production on
low-activity clay soils in the humid and sub-humid zones of West Africa. The upland ecosystem of West Africa is
very important to rice production. About 70% of upland rice is grown in the humid zone of the sub-region. To
increase and stabilize rice productivity of the acid uplands at reasonable levels, a strategy is needed that integrates
the use of tolerant cultivars with soil and plant-nutrient management. Research conducted on Alfisols and Ultisols
of the humid-forest and savannah zones in West Africa showed that upland rice is a robust crop, possessing a wide
range of tolerance to acid-soil conditions. Recent research at WARDA showed also that acid-soil tolerance can be
enhanced through interspecific Oryza sativa x O. glaberrima progenies, which not only possess increased tolerance
of acid-soil conditions, but also have superior overall adaptability to diverse upland environments in the sub-region.
Our research on the diagnosis of acid-soil infertility problems on the Ultisols and Alfisols of the humid savannah and
forest zones indicates that P deficiency is the most important nutrient disorder for upland rice. In the forest zone,
response to N depended on the application of P. In the savannah and forest-savannah transition zones, N deficiency
was more important than P deficiency. Among other plant nutrients, the application of Ca and Mg (as plant nutrients)
did not appear initially to improve the performance of acid-tolerant upland rice cultivars. The results from a long-term
study on an Ultisol with four acid-tolerant rice cultivars, revealed that they differed in agronomic and physiological
P efficiencies, and the efficiencies were higher at lower rates of P. The amounts of total P removed in three successive
crops were similar for all four cultivars although P-harvest index was 10 to 12% higher in the P-efficient than the
inefficient cultivars. The differences observed in the P efficiency of the cultivars may be due to variability in internal
efficiency of utilization of P. Overall, our research showed that rice productivity on the acid uplands can be improved
by exploiting synergy between genetic tolerance and new P-management practices.
As in other parts of the humid tropics, acid-related problems are the major constraint to crop production onlow-activity clay soils in the humid and sub-humid zones of West Africa. The upland ecosystem of West Africa isvery important to rice production. About 70% of upland rice is grown in the humid zone of the sub-region. Toincrease and stabilize rice productivity of the acid uplands at reasonable levels, a strategy is needed that integratesthe use of tolerant cultivars with soil and plant-nutrient management. Research conducted on Alfisols and Ultisolsof the humid-forest and savannah zones in West Africa showed that upland rice is a robust crop, possessing a widerange of tolerance to acid-soil conditions. Recent research at WARDA showed also that acid-soil tolerance can beenhanced through interspecific Oryza sativa x O. glaberrima progenies, which not only possess increased toleranceof acid-soil conditions, but also have superior overall adaptability to diverse upland environments in the sub-region.Our research on the diagnosis of acid-soil infertility problems on the Ultisols and Alfisols of the humid savannah andforest zones indicates that P deficiency is the most important nutrient disorder for upland rice. In the forest zone,response to N depended on the application of P. In the savannah and forest-savannah transition zones, N deficiencywas more important than P deficiency. Among other plant nutrients, the application of Ca and Mg (as plant nutrients)did not appear initially to improve the performance of acid-tolerant upland rice cultivars. The results from a long-termstudy on an Ultisol with four acid-tolerant rice cultivars, revealed that they differed in agronomic and physiologicalP efficiencies, and the efficiencies were higher at lower rates of P. The amounts of total P removed in three successivecrops were similar for all four cultivars although P-harvest index was 10 to 12% higher in the P-efficient than theinefficient cultivars. The differences observed in the P efficiency of the cultivars may be due to variability in internalefficiency of utilization of P. Overall, our research showed that rice productivity on the acid uplands can be improvedby exploiting synergy between genetic tolerance and new P-management practices.
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