Efficient use of the nitrogen in animal manures is essential for economic and environmental reasons. It requires applying the manure appropriately and making adjustments for this N if commercial fertilizer also is applied. Estimates of the amounts of plant-available N supplied by animal manures commonly are based on amounts of manure-N applied. Adjustments are often made for expected losses of N soon after application. These estimates are made with the knowledge that there is unpredictable variability in amounts of N rendered unavailable by ammonia volatilization, surface runoff, inunobilization, leaching, or denitrification. Although it is known to be substantial, there has been no practical method for addressing this variability. Advances in soil testing and plant analysis have provided new tools for estimating amounts of plant available N in soils. Soil testing for nitrate when com plants are between 6 and 12 in. gives estimates of N availability just before it is needed by the crop. This test can be used to evaluate the N-supplying power of manure applied to cornfields. In this study we use soil testing and yield response measurements to learn more about the relationship between rates of manure-N application and amounts of N available to com. The study centers on liquid swine manure from modem confinement buildings to minimize differences in quality of manure applied.