Phosphorus running off into lakes contributes to blue-green algal growth. That's not news. But what happened on a large lake in Ohio last year is big news. The 'perfect storm' of dry weather and phosphorus runoff produced an algal bloom on this large commercial lake that literally shut down businesses and closed beaches. Now, homeowners and shopkeepers around the lake are in the process of considering a class action lawsuit against farmers in the watershed since the root cause was phosphorus that ran off from land in the watershed and eventually into the lake.
Barry Fisher doesn't like to be an alarmist, but he believes Indiana farmers ought to reexamine their strategies on phosphorus usage while they have a chance, before someone tries to tell them what they can or can't do in some instances. Fisher is the state resource agronomist with the Natural Resources Conservation Service.
The area in Ohio where this occurred is heavy in livestock. Manure from livestock operations can contribute to the problem if it's not applied properly, or if it's applied so frequently on the same land that phosphorus levels are allowed to build to extremely high levels. It's also an issue that no-tillers must address, Fisher says, whether they have livestock or not.
"We know that we've created a concentrated zone of nutrients, including phosphorus, near the surface,' he says. "Studies done so far indicate that it hasn't actually affected yields. However, it does mean that there is a large concentration of phosphorus lying near the surface that could be subject to movement during a rain event."
If you don't know where your soil test levels are as far as concentration of nutrients in the profile, Fisher advises working with a consultant and pulling zero to three inch deep and three to six inch deep soil samples to find out. It might also be time to consider putting phosphorus back in the starter instead of broadcasting so much of it.
"We've also got to stay away from practices like applying fertilizer, especially phosphorus, on frozen ground," Fisher emphasizes. "If you get a heavy rain, you're going to lose most of that phosphorus, and it's going to wind up in the creek. It doesn't help anyone if that happens."
Cover crops, especially deep-rooted ones like annual ryegrass, may help move P down through the profile over time, Fisher says. It may also be time to consider abandoning the practice of applying all the fertilizer for two crops in one year, in favor of single, annual applications just ahead of the crop that's going to use the fertilizer, he says.
"And if you're doing some sort of tillage, such as the new vertical tillage, apply your phosphorus fertilizer first," he says. "That will at least give you a chance to work some of it into the soil rather than leaving it all on the surface where it's more susceptible to loss."