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Fluid Journal : Fluid Journal 1999-2001
3 Fluid Journal Summer 1999 bioavailable-P. Greater losses for soluble-P were found in the meso-plots. It is difficult to compare results of our experiments with those previously reported without many qualifying comments. Losses of NO3-N under the relatively extreme conditions imposed in this study were generally greater than under field conditions of other studies. Timing of greatest losses relative to rainfall, however, was similar. Greatest losses followed closely behind application when there was rainfall after application. In other studies, subsurface flow accounted for most of the losses. Only surface flow was analyzed in our study. Looking ahead Data collected in this study may be useful as estimates of maximum losses from runoff under similar farming practices. Such estimates are desirable in efforts to determine the loss potential of fertilizers under varying conditions. The data in this study suggest that experiments can be accomplished in micro-plots much more economically than is possible in meso-plots of the size used in this experiment or even larger plots that attempt to approximate a watershed. Dr. Gascho and Dr. Hook are professors, Crop and Soil Sciences, University of Georgia; Dr Wauchope is a chemist, Dr. Dowler is a weed scientist, and Dr. Johnson is a nematologist, USDA/ARS, Nematodes, Weeds, and Crops Research Unit; Dr. Truman is a soils scientist, USDA/ARS, Southeast Watershed Research Lab; Sumner an agricultural engineer, USDA/ARS, Insect Biology and Population Management Research Lab, Tifton; Dr. Davis is an associate pro-fessor, Soil and Crop Sciences Depart-ment, Colorado State University. Figure 2. Losses of NO3-N, soluble-P, and bioavailable-P as percent of applies N and P, data means of two replications and two years, Gascho, et al. , University of G e orgia, 1992-93. Micro-plots 4 4 2 3 0 1 2 3 NO -N 3 NO -N 3 Soluble-P Soluble-P Bio available-P Bio available-P Loss (% of applied) Loss (% of applied) -2 0 -20 0 1 1 0 20 20 40 40 Day Day Meso-plots 60 60 80 80 100 100 120 120
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