To determine soil phosphorus transformations that have occurred as a result of cropping practices and fertilizer practices. To determine seasonal changes of the different pools of soil phosphorus as a result of cropping practices and fertilizer practices. To conduct growth chamber studies to develop an understanding of the influence of plant roots and root exudates on the proportions and amounts of plant available phosphorus in the different pools of phosphorus in soil. To determine if a new laboratory test can be developed for accurately measuring plant available soil phosphorus.