Effects of N, Temperature, and Moisture Stress on the Growth and Physiology of Creeping Bentgrass and Response to Chelated Iron1

Abstract

AbstractBentgrass (Agrostis palustris Huds.) turf often will improve in turf quality with applications of Fe during various times of the year in the transition zone even though soils contain sufficient levels of this trace element. In this study, 'Penncross' creeping bentgrass was grown in an environmental growth chamber in a factorial arrangement of three chelated Fe rates (iron diethylenetriamine pentaacetate, FeDTPA), two N levels, and three irrigation regimes. Turf was preconditioned to soil moisture stress by allowing soil moisture levels to dry to either 80,50, or 20% of the total unsaturated soil moisture (TUSM) before being irrigated to 100% TUSM. Ambient temperatures and photoperiods within the chamber were altered to simulate a late fall through mid‐summer growth cycle. Foliar applications of FeDTPA increased top growth during cool temperatures, but as temperatures were raised, FeDTPA applications depressed top growth. Net photosynthesis (NP) was also reduced by FeDTPA; however, dark respiration was unchanged. Foliar carbohydrates were increased with FeDTPA and appeared directly related to corresponding top growth reductions. Moisture stress preconditioning did not significantly influence plant response to applications of FeDTPA. However, repeated exposure to low soil moisture tended to reduce foilage yields and increase verdure. This indicated a more decumbent growth habit had resulted from repeated moisture stress. Net photosynthesis decreased as soil moisture levels declined. However, preconditioning turf to low soil moisture did not subsequently influence NP at either low or high soil moisture levels. Dark respiration (DR), was significantly lower for plants previously grown at the lowest irrigation regime regardless of subsequent soil moisture level. This reduction in DR may help account for the increased foliar carbohydrates associated with infrequent irrigation. This study did not show that turf response to FeDTPA was related to interactions with moisture stress. However, turf did adapt both morphologically and physiologically to repeated cycles of low soil moisture.