EVALUATION OF LOCALIZED COMPACTION AND DOMING TO REDUCE ANION LEACHING LOSSES USING LYSIMETERS

Fertilizer N that leaches from the root zone is not available for upta ke by plants and can be transported to surface waters by subsurface dr ains, where it is considered a contaminant. Localized soil compaction and doming (LCD) to divert precipitation or irrigation water around th e zone of fertilizer injection may be one way to reduce nitrate (NO3-) leaching from agricultural fields. This study was designed to determi ne whether anion tracer transport through soil profiles to subsurface drains could be delayed by modified application methods, specifically (i) injection using a conventional knife shank; (ii) broadcast applica tion; and (iii) injection and covering using an LCD injector, Three fl uorobenzoate tracers, which move similarly to NO3- through soil, were applied to eight lysimeters at 63 kg ha(-1) using the three applicatio n treatments. Each treatment contained an individual tracer. Two rainf all intensity treatments were imposed, four lysimeters per rainfall in tensity treatment. All lysimeters received 50 mm of simulated rain 3 d after chemical application. A storm of this magnitude occurs once in 5 yr in Iowa. There were no differences in cumulative tracer leaching between the different rainfall intensity treatments, At the end of 6 m o, 5% of the tracer applied by a conventional knife shank leached to t he subsurface drains, 4% applied as broadcast leached, and 1% applied by the LCD leached. At 18 mo, corresponding values were 25, 17, and 13 %, These results suggested that soil modification in the fertilizer in jection zone was a simple and effective way to reduce anion leaching.