Iron for Nitrogen: Maximizing Color and Minimizing Growth of Bentgrass Putting Greens through Prescribed Nitrogen and Iron Formulations.

Intensive nitrogen (N) fertilization of golf course putting greens (PGs) encourages excessive shoot growth while potentially limiting root growth and subsequent nitrate recovery. Field experiments investigated partial substitution of N by iron in fertility programs of creeping bentgrass (Agrostis stolonifera L. ¡®Penn A-4¡¯) managed as PGs. Either sand- or soil-based PGs were treated with combinations of iron at rates of 0 to 4.9 kg ha^-1 mo^-1 (as FeSO₄∙7H₂O) and N at rates of 14.6 to 43.9 kg ha^-1 mo^-1 (as NH₄NO₃), every 6 or 12 d, May to Oct. 2007. Turfgrass color, canopy density, clipping yield, tissue nutrient levels, root length density, and root mass were measured to evaluate growth and visual quality. Fertilizer N use efficiency was calculated to indirectly assess nitrate leaching potential. Compared to the 12-d reapplication frequency, the 6-d frequency produced darker green color (P=0.155) and higher canopy density (P=0.004). Meanwhile, more frequent fertilizer application reduced variability observed across clipping yield collections. Iron rate substantially contributed to green color regardless of soil type. Clipping yields increased with N rate on both PGs, but response relative to the incremental N rates employed in this study was greater on the sand-based PG. Nitrogen showed little effect on canopy color at low iron rates; however, N and iron combinations demonstrated a positive synergetic effect on green color at higher iron rates. Supplementing intermediate N rates with iron fostered darker green PG canopy color, yet concomitant increases in clipping yield and/or canopy density were not observed.