Solid-solution partitioning of micronutrients Zn, Cu and B in tropical soils: Mechanistic and empirical models

Trace elements such as zinc (Zn), copper (Cu) and boron (B) are important micronutrients for crop production. Their bioavailability is essential to crops yield quantity quality in many tropical soils. Nutrient depends partly on the soil nutrient status, particular reactive soluble fractions. Adsorption/desorption precipitation/dissolution processes control partitioning of pool over solid solution phase. However, so far solid-solution trace has mostly been studied temperate often contaminated We studied, therefore, Zn, Cu B 172 soils from Burundi, Rwanda Kenya, using extensive characterization combination with multi-surface modelling two types empirical Freundlich type partition relations. Our aim was enhance understanding chemical that three these tropics a model, use this knowledge benchmark develop relations require less input data more convenient tools predicting concentration based existing data. show generic model applied performs similarly Zn previous studies The speciation dominated by adsorption organic matter, an increased importance metal (hydr)oxides increasing pH. Given its generally low concentrations soils, dissolved matter found be only Cu. mainly at pH, pH became important. overestimated most samples, which we attributed inaccurate estimation B. Interestingly, variation observed modeled expressed Kd among relatively small (?1 log L kg?1), consistently controlled concentration. Generally, optimized resulted smaller prediction error compared models. optimized, overestimation lowest concentrations, underestimation highest all elements. Partition parameters Kf n robust predictions since not related actual measured study easy-to-use contents can therefore current information Sub-Saharan Africa.