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 etilef 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 qualityx
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