Testing nitrogen and iron based compounds as environmentally safer alternative to control broadleaf weeds in turfgrass

Turfgrass is an important component of urban and rural lawns and landscapes. However, broadleaf weeds such as dandelions (Taraxacum officinale Weber ex. F.H. Wigg) and white clovers (Trifolium repens L.) pose major challenges to the health and aesthetics of turfgrass fields. Traditional chemical weed control methods, such as 2,4-dichlorophenoxyacetic acid (2,4-D) herbicides, are commonly used, but their safety and environmental impacts are contentious. Seeking environmentally friendly alternatives, this research investigated the effectiveness of nitrogen and iron compounds as nutrient management methods for weed control. In a two-phase experiment; the first was conducted on a mix of cool season turfgrasses (included perennial ryegrass (Lolium perenne L.), Kentucky bluegrass (Poa pratensis L.) and creeping red fescue (Festuca rubra L.)) grown in plastic containers under controlled conditions in the greenhouse. The treatment application included individual nitrogen (1 = urea and 2 = ammonium sulphate) and iron (3 = chelated iron and 4 = iron sulphate) compounds and their combinations (5 = urea × chelated iron, 6 = urea × iron sulphate, 7 = ammonium sulphate × chelated iron, 8 = ammonium sulphate × iron sulphate) contrasted with 9 = a conventional synthetic herbicide (Killex) and a 10 = control (no application) treatment. Weekly assessments over a 12-week period revealed that the combination of ammonium sulphate × iron sulphate had overall best results for weed control and turfgrass quality indicators, and thus was the most effective in inhibiting the growth of dandelions and white clovers while improving the health of turfgrass. The second part, following the greenhouse studies, tested the efficacy of the ammonium sulphate × iron sulphate treatment versus Killex and a control (no application) treatment under natural open environmental conditions at two sites (site 1: no shade vs. site 2: partial shade) with existing broadleaf weeds. The ammonium sulphate × iron sulphate treatment combination resulted in significant reduction in weed cover (66% and 33% in sites 1 and 2, respectively) as well as yielded superior turfgrass quality (based on visual quality ratings and photosynthetic capacity recorded) as compared to both Killex and the control treatments. Overall, the results of this research demonstrate that the combination of ammonium sulphate × iron sulphate is a promising nutrient management solution capable of achieving both aesthetic goals of weed control and turfgrass quality.