|Lamb, J - UNIVERSITY OF MINNESOTA|
Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: October 31, 1999
Publication Date: N/A
Technical Abstract: Chlorophyll meters were used to assess N status on irrigated corn from 1993-1998 at the MN MSEA site. Three 1.78 ha fields were part of a corn/soybean/wheat rotation with corn present each year. The soil was a Zimmerman fine sand with <10 g kg(^-1) organic matter. The last 20-50 percent of total N fertilizer applied was scheduled based on a mean of 30 chlorophyll measurements in 60 - 15x18m grid cells. This reduced total N applied on average by 66 kg ha(^-1) compared to a well fertilized area. Yield reductions using this tool ranged from 3.8-33 percent. Chlorophyll measurements were significantly correlated (p<0.01) between dates within a year; the correlation was only moderate. Chlorophyll measurements at VT were not correlated to N uptake at VT. They were moderately correlated to total N uptake and relative yield in 4 of 6 years. N uptake was moderately correlated among years. Relative yield was not always correlated among years.