TITLE:
In-Season Side-Dressing of Urea and Ammonium Nitrate to Cotton on No-Till Soils with High Residual Nitrogen and Pre-Plant Nitrogen Application
AUTHORS:
Xinhua Yin
KEYWORDS:
UAN, Side-Dress, Cotton, Yield, N Consumption
JOURNAL NAME:
Open Journal of Soil Science,
Vol.5 No.11,
November
26,
2015
ABSTRACT: It is essential to develop innovative approaches
that can apply N more efficiently. The objective of this study was to examine
in-season side-dress urea and ammonium nitrate (UAN) applications to cotton on
no-till soils with high residual N fertility. A field trial was conducted near
Milan, TN in 2011 and 2012 with strip plots in a RCB design with three
replicates. The following six in-season side-dress fluid UAN treatments were
compared: 1) zero N; 2) low uniform-rate N application of 56 kg·N·haǃ
3) high uniform-rate N application of 78.4 kg·N·haǃ 4) ordinary
variable-rate N application algorithm for each sub plot based on the average
Normalized Difference Vegetation Index (NDVI) value in that sub plot; 5)
reversed variable-rate N application algorithm for each sub plot based on
average NDVI of that sub plot; and 6) N application rate based on the average
NDVI value in each strip plot. All plots received 26 kg·N·haǃ as
diammonium phosphate before cotton planting each year. Leaf N concentrations were
mostly enhanced with all side-dress N applications ranging from 56 to 78 kg·N·haǃ relative to zero N during early to late bloom although this upland field had
high initial soil N fertility and received pre-plant application of 26 kg·N·haǃ across the treatments each year. However, NDVI, plant height, and lint yield were
rarely improved with side-dress N application. The three variable-rate N
application algorithms consumed 7.8 to 12.3 kg·haǃ more N than the
low uniform-rate application of 56 kg·N·haǃ, but 10.1 to 14.6 kg·haǃ less N than the high uniform rate of 78.4 kg·N·haǃ. Our results
indicate that the current N recommendations for cotton in Tennessee may be too
high on upland soils with high initial N fertility.