Accumulation of calcium magnesium in rhizosphere of barley 75 15 Available Available Ca(mM) 50 10 Ca 25 5 0 5 10 15 Distance from root surface(mm) Roussef Chino 1987
Accumulation of calcium & magnesium in rhizosphere of barley 0 5 10 15 Distance from root surface (mm) 15 10 5 Available Mg (mM) 75 50 25 Mg Ca Available Ca (mM) Roussef & Chino 1987
Gradients in the rhizosphere Longitudinal lateral gradients: Nutrient concentration .+ PH changes Depend on many factors e.g Form of n nutrition Soil ph buffering capacity Production of organic amino acids Microbial activity
Gradients in the rhizosphere Longitudinal & lateral gradients: Mycorrhizal & other fungi - concentrations & composition - population density & composition pH changes Depend on many factors e.g. • Form of N nutrition • Soil pH buffering capacity • Production of organic & amino acids • Microbial activity
Efect of n form on the rhizosphere pH of barley 200 kg N/ha H+ uptake(or 1A OH- hydroxyl H+ release release)during during NH4 NO assimilation assimilation 1B NO NH. Romheld 1986
Römheld 1986 200 kg N/ha Effect of N form on the rhizosphere pH of barley NO3 - NH4 + H+ uptake (or OH- hydroxyl release) during NO3 - assimilation H+ release during NH4 + assimilation
Soil nitrate concentration& rhizosphere pH of maize 1A 3A 3B 3C 3D 1cm 75 125 200 400 NO3-N(kg/ha) Romheld 1986
Soil nitrate concentration & rhizosphere pH of maize Römheld 1986 NO3 -N (kg/ha) 75 125 200 400
Rhizosphere pH of chickpea(鹰觜豆) with Nh4+ supply in soil and different CaCO3 addition 60 5A iIcm 5B 5C ‰CaCO 1.5 3.0 6.0 Romheld 1986 Increasing soil pH buffering
Römheld 1986 Rhizosphere pH of chickpea(鹰觜豆) with NH4 + supply in soil and different CaCO3 addition % CaCO3 1.5 3.0 6.0 Increasing soil pH & buffering