Submitted to: Journal of Plant Nutrition
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/7/2013
Publication Date: N/A
Citation: Interpretive Summary: Tall fescue is grown on 0.5 million acres in the Midwest for use as forage for horses, cattle and sheep production. Both yield and quality of fescue forage are improved with adequate nitrogen (N) nutrition. In this study we discovered best practices for applying fertilizer N to maximize N use efficiency of tall fescue. When N was subsurface banded greater N recovery of 42 % was measured in above ground dry matter versus 39% when the same rate of fertilizer was surface broadcasted over the growing crop. In addition using labeled 15-N labeled fertilizer, we documented that as much as 28% of the applied N was found in below ground root and crown tissue. The research also documents that the best method for maximizing N recovery and yield by tall fescue is to apply the N in subsurface bands. Nearly 99.7 % of the total N applied in subsurface bands could be accounted for. When N was applied in a surface top-dressed only 74% of the N applied could be accounted for. The other 26% was assumed to be lost as volatile N gaseous losses (either through ammonia volatilization or denitrification). This is important because this research documents the value of precision N placement and how that placement greatly influences the efficiency of fertilizer N uptake. Also, this manuscript documents methods of fertilizer placement that minimize the potential for contamination of soil and water resources.
Technical Abstract: The method of fertilizer nitrogen(N) application can affect N uptake in tall fescue and therefore its yield and quality. Subsurface-banding (knife) of fertilizer maximizes fescue N uptake in the poorly-drained clay–pan soils of southeastern Kansas. This study was conducted to determine if knifed N results in greater N uptake than the conventional top-dress application method in deep well drained soil of east-central Kansas. The experiment, conducted in a Smolan, silty clay loam soil, was a split-plot with fertilizer N rates of 0, 140 and 280 kg N ha-1 applied as urea-ammonium nitrate (UAN, 28% N), knifed or top-dressed. Soil inorganic N (NH4-N and NO3-N) and N in roots and plant tops were measured at various times during the growing season. At final harvest, most of the knifed N (99.7%) was accounted for in plant tissue (roots and tops) and soil, with more than half of the knifed N remaining as soil inorganic N. With the top-dressed method, 27% was unaccounted for and presumed lost in gaseous form. Knifing fertilizer N in fescue fields of east-central Kansas will maximize the availability of N, reduce potential N losses and increase forage quality.