2013 a good year for new soil testing tech
If you farm in an area where the drought robbed you of crop yield last fall, chances are you've still got nutrients out in your soils. Whether those nutrients eventually make it back into the soil where they're needed depends a lot on whether the drought continues and for how long. So, how do you know how much you should put down this year?
First, it's important to know where you sit, nutrient-wise. And the best way to find that out is by good soil testing, especially in three key areas, says Kansas State University soil fertility expert Dave Mengel. The first one has to do with the most critical nutrient to apply to corn, nitrogen. There's a lot of variability in just how much of the nitrogen you put down last year is still in your field.
"There is probably a significant amount of nitrogen in the soil available now, carryover from last year. If the drought does break here shortly and we get some moisture, the microbial activity will kick in and we'll get a flush of nitrogen mineralized out," Mengel says. "That's something that's going to be need to watched and monitored if at all possible."
The second key soil test in a year following -- and potentially continuing into -- a drought year is potassium. Whether or not you have a deficiency can be tough to grasp. But, if you've got comprehensive soil test records from past years, that's a good starting point, Mengel says.
"We haven't had enough moisture to move potassium out of the cornstalks back into the soil, so soil tests are coming back lower than normal. People are concerned that they've got low potassium or a potash deficiency. And, that may or may not be true," he says. "But, this is a situation where a history of soil test levels is very useful. You will see this where things are going right along, and all of a sudden they'll drop off the table in one of these dry years, then they'll come back. It's just simply the fact that we've got to get some moisture to move that potassium back into the soil. If you've got one of those low tests back, you might want to wait and take another sample after it's rained."
Finally, it's important to test for soil pH. Mengel says in a drought year like the last one, salts can sometimes accumulate in the soil's surface, taking down soil pH levels until rainfall can distribute those salts through the soil and raise pH levels. It's here where he says historical soil test results are valuable in making a decision whether to take action or wait for rain.
Fortunately, there are new tools that can help put off applications to widen the window during which you need to make your nutrient application decisions, Mengel says. Tools like chlorophyll meters and handheld sensors can allow you to sense nutrients in the field and help determine whether you should put down more nitrogen, potash, or other fertilizer.
"There are several things out there to help make that decision and come in later when the corn is waist- or shoulder-high and add more nutrients if they're necessary," Mengel says. "This is a good year to think about new [soil testing] technology and see what's out there."