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Input Reductions Based on Improved Soil Health
by LuAnn Rolling, District Conservationist

As producers look at yet another year of small corn and soybean profit margins I would like to talk about some ways to reduce inputs and increase profits, all while improving soil health.  I’m going to use the example of Rick Clark, a farmer from Williamsport, Indiana, because he has been dabbling in soil health for many years and keeps detailed records of his 7,000 acre farm.

He began no-tilling soybeans into corn 20 years ago. Five years later he began no-tilling corn and using rye cover crop. Nine years ago Mother Nature forced Rick into trying something new. Due to an extremely wet spring he was not able to terminate his rye ahead of planting as he had been doing and instead was forced to plant into green cover crop.

He found the planting to not be difficult and then became intrigued to know exactly what the cereal rye was contributing in terms of nutrients. He cut a 2-by-2-foot sample down to the ground and overnighted it to a lab for assessment. He found that 28-inch cereal rye contained 134# of N, 30# of P2O5 and 169# of K2O. It also had 10# of Sulfur, 12 of Magnesium and 31 of Calcium all in 6,800# of biomass.

Based on these results he began reducing his inputs. From 2011 to 2018 he was able to do a 27.5% decrease in synthetic nitrogen (N), 91.8% decrease in MAP (monoammonium phosphate) and a 100% decrease in both lime and potash applications - while improving yield averages year on year. Rick says that since 2011, corn has increased an average of 3.9 bushels per acre each year, and soybeans have increased 1.3 bushels per acre.

What does this mean for farmers in Allamakee County?  In general, your soil will have leftover nutrients hanging out in the top 24 inches, such as nitrates, which are vulnerable to leaching. Cover crops can forage this nitrogen and turn it into biomass that can re-release nutrients later when your next cash crop needs it.

One big example for me is a study where they did no added nitrogen for four years on corn plots. Some they planted cover crops on and others they did not.  Cover crops alone accounted for a 25% yield boost.

We are currently working with several producers on planting small grains and after harvest planting a diverse cover crop. Cover crops like hairy vetch and crimson clover are legumes that can add nitrogen that they collect out of the very air we breathe. Not only do they “fix” their own nitrogen needs, they will capture enough to give to a following nitrogen loving cash crop. If you plant your corn into a lush cover crop of hairy vetch, you can account for up to 100 pounds of nitrogen you won’t need to buy

We live in a volatile world with influences in fertilizer prices well out of our range of control. Take for instance the coronavirus, which threatens to impact fertilizers that have their origin in China. We need to consider reducing our dependence on factors we cannot control and consider soil health as our top priority.

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