Four different methods were analyzed for the study of N loss from aqueously applied urea due to urease activity in irrigation waters. The Watt and Chisp method was found to be less sensitive than required. The Douglas and Bremner Test was found to be variable in the results obtained. A bubbler constructed for lab use assayed nitrogen volatilized from urease activity but is not adaptable for field studies. An acid trap designed for field studies lacked accuracy. Two tests of six different Arizona agricultural waters both revealed no urease activity. The results obtained with the Douglas and Bremner Test must be interpreted carefully since the urease may have been inactivated by the buildup of end products of the urea decomposition reaction.

A field experiment to determine the effect of acidifying amendments and chiseling on water intake rate was conducted on the University of Arizona Experimental Farm at Marana. There was a total of 24 plots with six replications of each of the following treatments: sulfuric acid, Nitrosul, chiseling, and the control. The soil type was Pima clay loam. Four basin irrigations were applied during the summer of 1973 and the rate of infiltration was recorded for each plot. Chiseling to a depth of 50 cm was done prior to the first irrigation. The acidifying amendments were applied in the water during the first irrigation. Sulfuric acid and Nitrosul treated plots gave in general higher infiltration rates as compared with the control plots, but it was statistically significant only in the second irrigation. No significant response was obtained with chiseling. Soil analyses indicated a slight decrease in pH and SAR, and an increase in water holding capacity with the use of the acidifying amendments. Yields of sudangrass were not significantly different among treatments,