Crop Response to Phosphate Fertilization and to Residual Phosphate Levels: III. Greenhouse Experiment1
- M. Giskin2,
- J. Hagin3 and
- U. Kafkafi4
The greenhouse experiment was performed as a supplemerit to the field experiments described elsewhere, having in view that crop sequence is faster and that yield response to fertilizers is more likely to be found in such experiments than in the field. The aims of the experiment were to evaluate the build-up or depletion, during continuous cropping, of “available” phosphorus in soils with varying residual phosphate levels and to determine the contribution to yield of freshly applied and residual phosphates.
The pot experiment, with three soils and seven consecutive crops, received super-phosphate in amounts of 0, 19.4, 58.2, and 174.6 ppm P/3 kg soil. After removal of the third crop each of the four initial treatments was divided into four subtreatment groups. Rates of fertilization remained similar.
A linearity of relationships was found between P-uptake and total amount of fertilizer applied, dry matter yield and P extracted by NaHCO3 or water. For all three soils the freshly applied phosphate was more readily “available” than the residual phosphate but there was a decrease in dependence of yield response to freshly applied phosphate when the soil residual phosphate levels were high. In the Neve Yaar soil, the freshly added phosphate, expressed as ppm P in soil, produced roughly the same yield as an equivalent amount of NaHCO3-extractable P. Whereas, in the Lachish soil, approximately two to three times more of fresh P has to be applied in order to approximate the same yield level of NaHCO3-extractable P. This indicates a lower or slower fixation of phosphorus in the Neve Yaar soil and concurs with results found in the field experiments. Thus some quantitative relationship between plant response to freshly applied and residual phosphate was found which was not capable of being calculated from data of the field experiments.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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