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Die Bodenkultur - Journal for Land Management, Food and Environment
TAYE BEKELE and W. HÖFNER:
The effects of lime on the availability of phosphate from soil and applied monocalcium phosphate on two tropical soils
The effects of liming in improving the availability of phosphate from soil and applied mono-calcium phosphate was investigated on two acid soils of Ethiopia (Nitosol from Bako and Adet, pH(KCI) 4,4) in comparison to an acid soil from Germany (Gleyed Gray Brown Luvisol from Pettenbrunn, pH(KCI) 4,0). Maize served a test crop. The application of lime to Pettenbrunn soil significantly decreased the plant P-uptake. Wheras its application to Adet and Bako soil gave no significant response. In Pettenbrunn soil, P x lime interaction was positive for dry matter yield and negative for P-uptake, wheras it was negative for both P-uptake and dry matter yield in Adet as well as in Bako soil. The yield depressing effect of lime was more obvious and significant in Adet than in Bako soil. The response of the available-P content of the soil to lime was positive in Adet and Bako soil, but not in Pettenbrunn soil. Additional application of Mg or Zn to both lime and lime + P treated soils had no effect on the dry matter yield, implying that the observed yield depression was not caused by lime induced Mg or Zn deficiencies. The addition of lime had altered the contents of the different P fractions. In all the soils, all the inorganic P-forms, except Ca-P, increased substantially. In Bako and Adet soils, lime when accompained with phosphate applications had no effect on any of the P fractions. Whereas in Pettenbrunn soil it increased the content of water soluble Fe-P and Al-P fractions. No significant response of dry matter yield and P-uptake of maize was obtained to residual lime in all the three soils. Key words: maize, liming, P-uptake, tropical soils.