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Soil testing can make or break 2010 profitability

Jon Erickson Published on 03 February 2010
soil sample bag

If you’re trying to increase the profitability of your dairy by eliminating unnecessary expenditures, you’re not alone. The harsh climate of the dairy industry today has many dairy producers cutting costs wherever they can.

But saving money by reducing fertilizer inputs for corn silage fields could end up costing you more in the end.



Why regular soil tests are needed

A high-tonnage silage corn hybrid removes large amounts of nutrients from the soil. If these nutrients are not replaced on a regular basis, the overall yield potential, silage quality and milk production, can be compromised.

When milk prices were good, dairy producers were more willing and able to apply nutrients required for optimum silage production to their fields. But as fertilizer prices increased and milk prices decreased over the past two years, one of the first line items to be cut from the expense sheet was soil testing and fertilizer application. Producers may have managed to squeak out expected yields by living on the reserve of nutrients within the soil. But by now, if a producer’s regular fertility testing and application program has not been resumed, that “savings account” of nutrients has likely been depleted.

The first step to getting fertility levels back on track is to take a soil sample. A soil sample, like a blood test, helps producers closely monitor the health of their fields. By frequently taking soil samples, producers can preserve the productivity of their land and help to improve profitability across their operations. Soil tests help producers develop a more focused strategy, making it easier to determine how to best spend fertility input dollars or make manure applications based on the nutrients needed most.

Soil samples should be done about every three years. If a producer has multiple farms, the workload can be spread out by testing one-third of the acreage each year. For most areas, the best time to conduct a soil test is in the fall or early spring.

Analyzing soil test results

When analyzing the results of a soil test, dairy producers should look first at soil pH. Soil pH is a key that helps unlock other nutrients in the soil, making them accessible to the plant. In most cases, an ideal pH is 6.8 to 7.2, but it can vary by geography and crops grown in the rotation. Producers should work with a local soil expert to determine the pH level needed to optimize silage production in their area.


Potassium (K) levels also can be determined by a soil test. In silage production, large amounts of K are removed from the soil, but many producers are not applying enough of it in their fertilizer. K is essential for stalk strength, making corn stover a reservoir for K storage. When harvesting corn for grain, the stalk is left behind and recycled in the soil, but when harvesting silage, the stalk is removed. Applying K as potash fertilizer can help replenish the soil with this key nutrient.

Monitoring other key nutrients is equally important for silage production. Other key nutrient levels that should be analyzed via a soil test include phosphorus, sulfur, boron, calcium, magnesium and zinc. A typical soil test will not provide an accurate reading of nitrogen (N) in the soil, so soil nitrate tests should be conducted to determine N needs.

Soil tests make fertility plans more efficient

Producers should follow the fertilizer recommendations for their particular geography and soil type, and using the results of a soil test can help a producer establish a fertility plan that is specifically designed for his or her operation. Although the cost of fertilizer may fluctuate, there are ways to improve the efficiency of a fertilizer investment while maintaining the overall yield potential of a field.

The technology of precision agriculture allows producers to take soil samples using a Global Positioning System (GPS) grid to determine exactly which nutrients are needed and where within a given field. This information can then help producers make better use of their fertilizer dollars. For producers who apply liquid manure, there is a new tool to help protect the applied N in the soil. New Instinct nitrogen stabilizer slows the conversion of nitrogen from the ammonium form to the nitrate form to keep it available at the plant root zone, where it is more accessible to the plant.

Impact on milk production

How does improving the fertility of soil affect your bottom line? Good-quality silage starts with fertile soil. If silage is grown in a nutrient-deprived field, overall yields will be poor and crop quality could suffer. If the quality is poor, the crop will likely be more susceptible to disease and, therefore, more susceptible to mold and mycotoxins. Feeding poor-quality silage to high-producing dairy cows is like trying to put regular gasoline into a sports car that requires premium fuel – when you feed low-quality silage, you will not get the level of milk that your cows are capable of producing.

Managing a fertility plan in a tight dairy market is a tough act to balance. Producers can either pay the high cost of fertilizer up front, or they can try to cut fertilizer from their program and lose on the other end with decreased yield, poor silage quality and reduced milk production. Soil sampling is a critical step to understand the fertility level and needs of a field intended for silage production. Skimping on nutrients is not a wise cost-savings practice when it results in lost yield and decreased cow productivity. To ensure your operation is maximizing its resources, use the results of regular soil tests to assist in developing a fertility plan that can help improve the quality of silage production and overall profitability. PD


Photo courtesy of Kevin Caldwell, AET Consulting

Jon Erickson
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