The Application of the Relationship Between Fructan and Protein for N Recommendations in Turfgrass.

The Application of the Relationship Between Fructan and Protein for N Recommendations in Turfgrass T. L. Housley, P. Kongsila, J. Nemitz, K. S. Walker and C. A. Bigelow Agronomy Department Purdue University Lawns represent the greatest managed turf sector in the US. Over fertilization of turf has the potential to be an important contributor to ground water quality. Providing nitrogen fertility recommendations to homeowners can prevent over fertilization and contamination of ground water. The relationship between fructan and nitrogen has been used in commercial testing to determine mid-season nitrogen application rates in wheat (McGrath et al. 1997, New Phytol. 136:145-152). Utilization of this testing has resulted in improvements in quality and yield of wheat (McGrath et al. 1995, Proc. 45th Australian Cereal Chemistry Conference pp. 538-541). Research presented here tests the hypothesis that the relationship of fructan to protein nitrogen can be used to determine nitrogen fertility recommendations for cool season turf grass. Differences in tissue protein nitrogen were generated by varying fertilizer application over two years to Kentucky bluegrass, perennial ryegrass and tall fescue (Walker et. al. 2007, Crop Sci. 47:1225-1236). Significant differences in average leaf N and dry matter yield was found in each species. Perennial ryegrass and tall fescue are fructan containing turf species. Differences in protein and fructan content are expected and will be determined colormetrically on freeze dried tissue. Total C and N in the tissue will also be presented. The wave lengths most representative of tissue fructan, protein, total C and N will be identified using NIR. An equation accounting for the relationship between fructan content and protein nitrogen will be presented. This equation will be compared to that used commercially for mid-season nitrogen recommendation in wheat. The potential for Commercial utilization of this NIR equation for nitrogen fertility recommendations in turf will be discussed.