Q I continue to hear about nitrates and leaching into the groundwater. It seems every time this is mentioned, the turfgrass industry is highlighted. How can I be sure I'm not part of the problem? — via the Internet

A Nitrates in groundwater do continue to be an issue, especially in areas with higher rainfall and coarse soils; however, it can be a problem in any area if practices are not properly implemented. There are a number of practices that can be modified with little effort, which will result in reduced opportunity for nitrogen run-off. Water-soluble fertilizers are more likely to leach than slow-release ones simply because they dissolve quicker. If you must use water-soluble sources of nitrogen, consider breaking up the application into two or more split applications. Whenever possible, use slow-release forms of nitrogen. During cooler temperatures, choose IBDU or SCU sources, as their release does not depend solely on microbes. Microbial activity slows as the temperature falls. During warmer temperatures, UF and organic fertilizers can be added to your list of choices. Soil texture, too, greatly affects runoff and leaching potential. Soils higher in clay are less likely to leach, but if they are compact, runoff is an issue. Soils higher in sand content are more likely to leach, less likely to runoff. Adjust application rate and irrigation schedule to account for your soil texture. On sandier soils, perform more frequent, smaller applications of nitrogen. Different grass species have varying nitrogen requirements. Bermudagrass responds to higher amounts of nitrogen than zoysiagrass. Know your turfgrass and apply the minimum nitrogen needed to maintain a healthy turf. Shorter mowing heights lead to smaller root system, which decreases the ability to take up available nitrogen. Mow at the tallest height possible given your turf and its function. If green-up is needed, but the potential for run-off is high (higher irrigation needed to help recover from high traffic or rainier season), try an application of iron. Iron works well for mid-summer green up and to produce early spring green up. Biostimulants have also proven effective for greening up turf, in lieu of nitrogen application.


Q I'd like to try organic fertilizers for my turf, but how do I know if or when they break down enough to fertilize the turf? — St. Louis, Mo.

A With water-soluble fertilizers, you know the release occurs as soon as the granules are dissolved; slow-release fertilizers are nicely researched and provide us with a release table based of course on a particular temperature. Natural fertilizers can be a bit trickier, but no less effective. Research continues that shows a large portion of the nitrogen is released within two to four weeks. A recent study that looked at seabird guano, hydrolyzed fish powder, feather meal and blood meal found that within two weeks between 47 and 60 percent of organic nitrogen had been mineralized and released. Quicker than water soluble fertilizer? Probably not. But for maintenance applications, organic fertilizers can fill a need. If you need faster action, you might try a small amount of water-soluble fertilizer coupled with your natural source. Other sources might behave differently. Give them a try and see how they work in your situation.

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