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Soil testing and lime are still the farmers’ best investments for the future

Raymond T. Rivard photograph

As the calendar turns the page to 2017, our local farmers will once again begin planning the new cropping season. 

Barring any shocks to the markets, 2017 looks to be a tight margin year again for corn and soybean growers.

In a recent meeting with Carrie Laboski, UW-Extension soil scientist, the discussion turned to what can we do to manage fertilizer costs in a year like this?

To no surprise, much of what we can do is getting back to the basics.

Soil test — don’t guess

To determine a nutrient application rate, we need to know what is currently available in soil reserves for phosphorus and potassium. While most farmers do a good job maintaining soil test records, there is still room for improvement. To be useful, soil test reports should be four years old or less. Under-fertilization can be just as costly as over-fertilization. Soil testing will help you determine the right rate to apply and in the right places. Soil testing costs as little as 60 cents per-acre, making it one of the best returns on investment a farmer can make.

Low pH can kill crops

Ryan Sterry, Ag Agent, UW-ExtensionA critical piece of information from your soil test reports is soil pH and lime recommendations.

Patches of yellow or stunted crops not due to moisture stress should be investigated for low pH.

This can be especially tricky on rented land, where neither the landowner nor tenant have taken responsibility for managing pH or applying lime.

Soil pH is critical because it plays a key role in nutrient availability, with low pH levels making it difficult for the crop to utilize present nutrients. To achieve maximum return to your fertilizer dollar, also invest in ag lime needs as determined by soil testing.

Legume crops such as alfalfa and soybean are more sensitive to low pH. If you cannot afford to apply lime to all fields that need it, focus on fields that will be in alfalfa or soybeans in the near future. Lime is slow acting, taking up to three years to be fully effective in the soil. Plan ahead legume rotations to apply lime far enough in advance.

Practice the 4 R’s of nutrient stewardship

Right source: Consider both naturally available sources and the characteristics of specific commercial products. A balance of both is oftentimes required. Take available nutrient credits from legume crops and manure applications. Treat manure as if it was as valuable as purchased fertilizer, because it is.

Right rate: Make decisions based on current soil test results and crop demand level.

Right time: Make fertilizer application based on how the crop takes up nutrients, nutrient loss risks, and field operation logistics. Take action to reduce the risks of loss via nitrate leaching or ammonia volatilization. Choose the correct nitrogen formulation based upon price/unit and method of application. Consider split applications of nitrogen when appropriate.

Right place: Address nutrient movement to meet site specific crop needs and limit potential losses from the field. Broadcast, pop-up and banded methods of fertilizer application each has its own unique advantages. Consider the crop, soil conditions, and your tillage system when deciding on fertilizer placement.

Ryan Sterry is the St. Croix County Agriculture Agent

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