02261nam a2200301 a 450000100080000000500110000800800410001910000190006024500920007926000440017130000100021550000180022552015430024365000150178665000090180165000160181065000120182665000130183865000090185165000090186065300170186965300200188665300080190665300110191465300140192565300120193965300080195114590422006-06-01       1983    bl uuuu  m   00u1 u    #d1 aBORKERT, C. M.  aMechanistic modeling of phosphate placement to maximize phosphate recovery by soybeans.  aWest Lafayette: Purdue Universityc1983  a175p.  aPh.D. Thesis.  aPrevious research has shown inconsistent results from P fertilizer placement. The objective of this research was to study the effect on the mechanisms governing P uptake when fertilizer is placed in various volume fractions of the soil. Experiments were conducted in pots in a controlled climate chamber. Kinetic parameters for P uptake, root distribution and morphology and soil supply parameters were measured. Increasing rate of P added to the soil increased P concentration in soil solution (Cl) and the P diffusion coefficient (De), while decreasing the buffer power (b). The initial rate of added P increased root length and decreased root radius, while higher rates of P depressed root growth. Rate of P uptake (influx) increased as Cl increased, however, yield reached a maximum and then decreased when Cl became very high. The effects of P placement on soil and plant parameters were studied by decreasing the soil volume to which the same rate of P per pot was added. Values of soil parameters were determined for both P fertilized and unfertilized soil. Adding P fertilizer to decreasing soil volumes stimulated root growth in the fertilized portion while the root redius became smaller in this zone. The relation between volume fraction of the soil fertilized by P and fraction of the total root length that was in the fertilized soil could be described by Y = X 0.70, where X is the proportion of the soil volume treated with P and Y is the predicted proportion of total root length in the P treated soil. In a split-root ...  aphosphorus  asoil  aCrescimento  aFosfato  aFósforo  aSoja  aSolo  aAvailability  aDisponibilidade  aEUA  aGrowth  aPhosphate  aSoybean  aUSA