Bakhsh,A., Kanwar,R.S. and Baker,J.L.(2010): N-application methods and precipitation pattern effects on subsurface drainage nitrate losses and crop yields. Water Air Soil Pollut., 212, 65-76.yŒ©‚遨z
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wAbstract
@Diverting the infiltrating water away from the zone of N application can reduce nitrate-nitrogen (NO3-N) leaching losses to groundwater from agricultural fields. This study was conducted from 2001 through 2005 to determine the effects of N-application methods using a localized compaction and doming (LCD) applicator and spoke injector on NO3-N leaching losses to subsurface drainage water and corn (Zea mays L.)-soybean (Glycine max L.) yields. The field experiments were conducted at the Iowa State University's northeastern research center near Nashua, Iowa, on corn-soybean rotation plots under chisel plow system having subsurface drainage etilef system installed in 1979. The soils at the site are glacial till derived soils. The N-application rates of 168 kg-N ha-1 were applied to corn for both the treatments each replicated three times in a randomized complex block design. For combined 5 years, the LCD N-applicator in comparison with spoke injector showed lower flow weighted NO3-N concentrations in tile water (16.8 vs. 20.1 mg L-1) from corn plots, greater tile flow (66 vs. 49 mm), almost equivalent NO3-N leaching loss with tile water (11.5 vs. 11.3 kg-N ha-1) and similar corn grain yields (11.17 vs. 11.37 Mg ha-1), respectively, although treatments effects were found to be non-significant (p=0.05) statistically. The analysis, however, revealed that amount and temporal distribution of the growing season precipitation also affected the tile flow, NO3-N leaching loss to subsurface drain water, and corn-soybean yields. Moreover, the spatial variability effects from plot to plot in some cases, resulted in differences of tile flow and NO3-N leaching losses in the range of three to four times despite being treated with the same management practices. These results indicate that the LCD N-applicator in comparison with spoke injector resulted in lower flow weighted NO3-N concentrations in subsurface drain water of corn plots; however, strategies need to be developed to reduce the offsite transport of nitrate leaching losses during early spring period from March through June.

Keywords: LCD N-applicator; Spoke injector; Subsurface drainage; Water qualityx

1. Introduction
2. Materials and methods
@2.1. Experimental treatments
@2.2. Subsurface drainage system and data collection
@2.3. Statistical analysis
3. Results and discussion
@3.1. Precipitation effects on tile flow and NO3-N leaching losses
@3.2. Treatment effects on tile flow and NO3-N leaching losses
@3.3. Spatial and temporal variability effects on tile flow and NO3-N leaching loss
@3.4. Corn-soybean yields
4. Summary and conclusions
References


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