Changes Of Paddy Soil Phosphorus And Potassium Under Different Fertilization Conditions Of The Long Term Experiment And Their Effect On The Uptake Of Rice's Phosphorus And Potassium Nutrient And On The Rice Yield

This thesis was consisted of three sections: (1) Changes of soil phosphorus under different fertilization conditions of the long term experiment;(2) Changes of soil potassium under different fertilization conditions of the long term experiment and (3) The effect of changes of soil phosphorus and potassium under different fertilization conditions of the long term experiment.Till the later rice (LR) season in 2000, the long term experiment initiated in the 1997 early rice (ER) season at the Experiment Station in Jinhua had been carried out for eight seasons and the another long term experiment in Shimen farm started with 1998 LR also lasted for five seasons. Soil fertility of the Experiment Station declined rapidly in this experiment with pronounced K deficiency particularly in the LR crop, and P deficiency particularly in the ER crop, and the Experiment of Shimen farm had a pronounced K but no P deficiency.Both experiments included the comparison of hybrid and conventional rice. All crop residues were removed in the experiment, and paddy soil samples were collected after each LR crop. The analytical data of the paddy soil samples were worked out in laboratory. Plant samples were also harvested to analyze for uptake of rice' s nutrient and crop yield. The main results showed:1. Under different fertilization conditions, paddy soil phosphorus and potassium became lower after several crop seasons than before, and the different fractionations of soil phosphorus and potassium had different changes. There was a very rapid decline in paddy soil phosphorus and potassium with no fertilization contrast to the decline under fertilization conditions.2. Uptake of rice' s phosphorus and potassium nutrient also declined rapidly after several crop seasons with no fertilization, and the speed at which45the paddy soil phosphorus and potassium decrease under fertilization conditions was also slower than they do with no fertilization.3. Changes of paddy soil phosphorus and potassium under different fertilization conditions had some different effects on rice yield. The different fractionation' s characterization of paddy soil phosphorus and potassium which was changeable under different fertilization conditions showed that the change of season and fertilization conditions could affect rice yield in some certain way.