Ryan Christensen and Dr. Bryan G. Hopkins, Plant and Wildlife Science
Landscape managers spend substantial resource, both time and money, maintaining aesthetically pleasing landscapes. In addition, athletic events conducted on natural grass playing surfaces are dependent upon having a healthy turfgrass that provide both cushioning and footing stability. Poor field conditions can lead to career ending injuries of athletes.
Nitrogen (N) is primarily used by homeowners and landscape managers to maintain a lush, green turf. Excess N, however, leads to shallow roots and excess shoot growth, both of which are detrimental to a safe playing field. In addition, excess N has potential to lead to nitrate (NO3-) pollution in water sources, as well as an increase in the emission of nitrous oxide, a potent greenhouse gas. Previous studies have shown that iron (Fe) can help to maintain a green turfgrass, while reducing N application. My study compared a new Fe product, elemental sulfur impregnated with iron (ES-Fe), against current popular Fe fertilizers. The current products are labor intensive and/or ineffective as an Fe source in turfgrass. Our hypothesis was that the ES-Fe would help keep the turfgrass green, while increasing rooting depth, decreasing the need for N application and the detrimental effects caused by excess N application. The current Fe products are either ineffective or very labor/cost intensive. The new ES-Fe was believed to eliminate both of these problems.
The study was conducted over 178 days in the greenhouse at Brigham Young University. Two different varieties of Kentucky bluegrass were used, ‘Everest’ and ‘Limousine’ (provided by Jacklin Seed Company, Post Falls, Idaho). We used a soil that was constructed from different Idaho soils. The goal was to develop a basic soil high in lime content, which is similar to the soils of Utah. Normally, basic soils with high lime have Fe deficiency problems.
The ES-Fe was compared to a controlled check (U) with no Fe application, ferrous sulfate (FS), an iron chelate that was applied to the soil (CS), and an iron chelate applied to the foliage (CF). All of the best management practices were observed, these included planting, watering, fertilizing, and taking clippings. The clippings were collected each time and kept for analysis of shoot growth.
Halfway through the study, no iron chlorosis (or loss of greenness) was observed in any of the trials. To try to induce iron chlorosis, we added calcium carbonate (CaCO3) to the irrigation water to try to induce chlorosis. This resulted in no increase in chlorosis. In addition to adding CaCO3 to the water, we removed the turf from the pots and added CaCO3 directly to the soil. This too resulted in no increase in iron chlorosis.
At the conclusion of the study, the turfgrass was harvested for analysis. The shoots were separated from the roots and analyzed separately. Both the shoots and roots were measured for length, then weighed, dried, and weighed again. The results of this process showed no difference among any of the Fe treatments on root and shoot growth.
The clippings were then ground to be analyzed for nutrient content. The ground clippings were digested in nitric-perchloric acid and then analyzed by inductively coupled plasma (ICP, Thermo Electron Corporation, Franklin Maryland) spectroscopy. The results showed that we successfully increased Fe concentrations in the plant through the use of the ES-Fe and the iron chelates. Therefore we successfully showed the ES-Fe is more effective then FS, and could be used to replace the labor/cost intensive chelate products. However, since chlorosis never developed, we determined that through the extensive turfgrass breeding programs, Fe deficiencies have been bred out of these two Kentucky bluegrass cultivars. As a result, the extra expense of Fe application is not needed unless Fe chlorosis develops. These findings will help BYU and other turf managers save money by reducing Fe applications on Kentucky bluegrass. However, if chlorosis does develop, our research shows the ES-Fe can be used to correct the problem.
Our results were presented as a poster at the 2008 ASA-CSSA-SSSA Joint International Annual Meetings that were held in Houston, Texas in October of 2008. In addition to the poster presentation, the results are in the process of being submitted for publication to Crop Science Society of America Journal and Turfgrass Trends. We are hoping to be published by January of 2009.
I learned a lot of valuable lessons from this study. I am graduating in December and will return to my family farm and family owned golf course. The things I learned about Fe application in turfgrass I will be able to apply to my future career. I will be able to save the money on Fe application unless it is needed. I will also be able to use the new ES-Fe fertilizer in replace of the current Fe products if the need arises. I am also interested in looking elsewhere to find ways to reduce N application while maintaining green grass.