Submitted to: Plant Nutrition Colloquium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: May 1, 2001
Publication Date: N/A
Interpretive Summary: In acid soils low pH and aluminum toxicity are the major chemical constraints for growth and development of roots. Cultivar/genotypes that have capacity to increase the rhizosphere pH have a better chance of growing and producing higher yields in acidic soils. Experiments were undertaken in controlled growth conditions with acid soil to assess the influence of soil aluminum and potassium on rhizosphere pH changes by two sorghum genotypes differing in aluminum tolerance. Microelectrode technique was used to measure the rhizosphere pH. This technique was successful in detecting the changes in the rhizosphere pH without disturbing the soil. Potassium appears to play a beneficial role in increasing aluminum toxicity tolerance of sensitive genotypes. Selection of genotypes which have the capacity to increase the rhizosphere pH are useful in increasing crop yields in acidic soil. Farmers could apply potassium fertilizer to acid soils to reduce aluminum toxicity and by adapting a aluminum tolerant genotype/cultivars could increase the yield potentials of acid soils.
Research was undertaken to quantify the rhizosphere pH values of two sorghum genotypes differing in aluminum tolerance behavior subjected to varying levels of soil aluminum and potassium and their possible involvement in modification of aluminum tolerance mechanism. Obtained results showed the existence of genetic variability in sorghum genotypes to ochange the rhizosphere pH and the magnitude of these changes might be influenced by the levels of added potassium when aluminum tolerance is present. The use of microelectrodes to estimate the changes in rhizospheric pH appears to be a valuable technique. Potassium ions appear to play an important role to increase aluminum tolerance of sensitive genotypes at above certain potassium concentration in soil.