Soil - Root System Nutrient Transfer Mechanism And Its Numerical Simulation

Plant growth involves the interaction of soil and plant properities. Soil is the normal medium for plant root growth. The plant's roots absorb nutrients and water from the soil. The plant's rate of absorption of nutrients involves processes going on in both the plant's root and soil. Each of these processes is impartment in providing nutrients for use by the shoot. A series of experiments were carried out by employing four kinds of soil, including cultivated loessial soil, black lu soil, Lou soil and sand loam soil in Shaanxi province. Mechanisms of nutrient movement at the soil-root system from soil were studied by the method of soil experiment and potted plant cultivate. Use the mechanistic models which simulation of these processes. The main results as follow:1. Soil phosphate diffusion characteristic and influence factors were investigated in three kinds of soil with different soil texture by the method of trace of 32P. The quantify relation of soil phosphate diffusion coefficient (De) with the different soil, soil water content, temperature and soil volume weight were educed by the experiment. The idea of "the temperature coefficient of phosphate diffusion coefficient" which describes the temperature effect of soil P diffusion coefficient was propounded. According to experiments on hydrodynamic dispersion in saturated and unsaturated soils, a method was given for calculated the saturated and unsaturated hydrodynamic dispersion coefficient (Dsh).of adsorption(K+) and non adsorption (NO3-)nutrient. 2. Effect of apply phosphorus fertilization on soil P adsorption characteristic were studied by the method of combinative with adoption soil solution centrifuge and anion exchange resin; The soil P adsorptions model of forecast soil P supply ability was deduced with theoretic; twain were used to describe the two main process of P adsorption and adsorptions in soil, the parameter of soil P supply ability were measured and computed by the lab experiment. 3 .The effect of supply ammonium or nitrate on the mobilization of phosphate, change in pH, and soil P fractionation in interface of soil-root of wheat were studied by the root study container (RSC) technique. Plant -induced changes of soil pH were brought about by application of ammonium-or nitrate-nitrogen. Mobilization of soil P fractionation was assessed by P-depletion profiles of the rhizosphere soil.4. The effect solution P concentration of root medium on corn growth and phosphate uptake kinetics was investigated by P depletion experiment. The quantify relation of maximum P influx (Imax), Michaelis constants (Km), the minimum P concentration (Cmin) with the medium P concentration, plant P content and Ratio of root and shoot. Increase in the supply of P in the solution promoted its uptake and decreased the P utilization rate. The proportions of Zn retained in root increase and accumulate with larger root Zn uptake with the increase of the solution P concentration. But the Zn concentrations retained in shoots and Zn transport rate form root to shoot vary litter with the increase of the solution P concentration. Zn and P concentrations in roots were positively correlated. The uptake NO3－,NH4＋,H2PO4－和K＋kinetics mechanisms and parameter of wheat and barley were measurement by the method of concentration grads. The effects of cooperate and compete between nutrient ions absorption by crops roots were probed into. The effect of supply ammonium or nitrate on the growth, nitrite accumulation, proline content and nutrient ion absorption of cabbage were studied by solution culture experiment. .5. Mechanistic plant nutrient uptake models were established with considering soil nutrient and water current status, plant root morphologic, root uptake kinetics parameter according to the mechanism of nutrient transfer and uptake at soil-root system. The steady nutrient uptake model of Yanai was used to verification of measured corn seedling P absorption under different soil P supply condition in potted plant cultivate. By comparing the measured and mode...