Sign up for email alerts of new Fluid Journal issues!
Fluid Journal : Early Spring 2013
The Fluid Journal Early Spring 2013 17 lint yield and NDVI, and between NDVI and crop N nutrition status • If there is a significant relationship between cotton yield and canopy NDVI, then algorithms will be developed for variable-rate N applications within a field based on the relationship between lint yield and NDVI. The algorithms for variable-rate N applications compared with the uniform-rate N application system in terms of consumption and lint yield. In 2011, our work focused on objectives 2and3. Methodology Location. Experiment was conducted on a private farm in Gibson County in western Tennessee. Treatments. Five N application rates of 0, 40, 80, 120, and 160 lbs/A were evaluated as sidedress N. Plots were 38-foot wide strips running the length of the field in a randomized complete block design with three replicates. Each strip plot in this test was divided into eight 100-foot-long sub plots. Planting. Dates of cotton planting and N treatment implementation are presented in Table 1. Cotton was planted in 38-inch rows. Summing up Correlations. The correlations of lint yield with canopy NDVI were statistically significant at early square and early, mid, and late bloom stages (Table 2). The correlations of lint yield with leaf N were significant at mid and late bloom stages (Table 2). There was significant correlation of leaf N with canopy NDVI at mid and late bloom stages (Table 2). Overall the determination coefficient (R2) values for the above correlations in 2011 were similar to those in 2010, but lower than those in 2009, which suggests that the correlations of lint yields with canopy NDVI and leaf N vary with years. GIS maps. Arc View GIS maps of canopy NDVI, leaf N, lint yields, and post- harvest soil N at Gibson are presented in Maps 1 through 10. The lint yield maps show that spatial variations in lint yield did exist within most strip plots. Visually, it seemed lint yield had a better correlation with canopy NDVI at late bloom (August 17) than the other growth stages. The post-harvest soil N map (Map 10) indicates that the sidedress N treatments implemented early in the season did not show evident impacts on soil nitrate Figure 1: Moran's I and scatter plot of residual lint yield (N treatment effects on yields excluded) at Gibson in 2011. Table 1. Major operations performed at Gibson in 2011. List of operations performed Date performed Cotton planting 5/21/2011 Side dress liquid nitrogen treatments 6/15/2011 Collected early square leaf samples 7/5/2011 Collected early bloom leaf samples 7/27/2011 Collected mid-bloom leaf samples 8/4/2011 Collected late bloom leaf samples 8/17/2011 Recorded canopy NDVI at early square 7/5/2011 Recorded canopy NDVI at early bloom 7/27/2011 Recorded canopy NDVI at mid-bloom 8/4/2011 Recorded canopy NDVI at late bloom 8/17/2011 Dried and ground all leaf samples & shipped them for analyses 10/14/2011 Harvested center 6 rows of each 12-row plot 10/1/2011 Collected seed cotton samples for lint quality 10/1/2011 Collected 2 ft. post-harvest soil samples 11/10/2011 Dried and ground all soil samples & shipped them for analysis 12/6/2011
Late Spring 2013