Nitrogen fertilization of warm-season turfgrasses irrigated from varying irrigation systems: 2. Carbohydrate and protein content

A 3-year study was conducted at New Mexico State University in Las Cruces, NM, to investigate whether different fertilization treatments affect the carbohydrate and protein content in two warm-season grasses grown using water conservation strategies such as non-potable saline irrigation water and a subsurface irrigation system. Princess 77 bermudagrass (Cynodon dactylon L.) and Sea Spray seashore paspalum (Paspalum vaginatum O. Swartz) were irrigated with either potable (electrical conductivity [EC]=0.6 dSm(-1)) or saline (EC=3.1dSm(-1)) water from either an overhead or a subsurface drip irrigation system. Four different fertilizers were used in this study: liquid slow release, granular slow release, granular urea and urea liquid, at two rates: 10 and 20g Nm(-2)yr(-1) for Sea Spray and 20 and 30g N m(-2)yr(-1) for Princess 77. Carbohydrate (sucrose, starch, total soluble carbohydrates and total non-structural carbohydrates) and protein content of the grasses were measured, and their effect on spring green-up was determined. The total carbohydrate content within the stolons and rhizomes was found to be closely associated with speed of spring green-up, resulting in R-2 values ranging from 0.36 to 0.76. The relationship between green-up and carbohydrate content was similar for both grasses. Fertilizer treatment did not affect carbohydrate content in either grass under either irrigation system. Further analysis revealed that carbohydrate content in February was the best determinant for spring green-up. Other sampling months also showed a significant correlation with spring green-up, but with lower R-2 values.