It is difficult to put a percentage on the amount of nitrogen (N) NutriSphere-N protects from loss. NutriSphere-N works to keep ammonium nitrogen in that stable form longer. With the ammonium nitrate portion of the UAN, NutriSphere-N will not have an effect on the nitrogen already in the nitrate form. The nitrate will be subject to leaching, but that problem is not likely under the dry conditions you’ve described. NutriSphere-N will have an effect on the ammonium portion of the liquid UAN. NutriSphere-N slows nitrification, which extends the presence of ammonium N and enhances ammonium uptake by corn. 

For the urea portion of UAN, NutriSphere-N significantly slows, but does not completely stop, urea hydrolysis and possible ammonia volatilization from surface applications. The overall potential for ammonia loss by volatilization still depends upon field and climatic conditions – research shows having NutriSphere-N protection will reduce the risk of loss. 

For the second part of the question, it’s the actual microbes in the soil that break down the polymer chain. So regardless of the amount of soil moisture present at application NutriSphere-N will protect the ammonium N for several months. University and third party independent research has shown almost equal yield results when comparing NutriSphere-N treated N (UAN and urea) applied in the fall and spring.