Environmental Management – or “That was then, this is NOW”
Then versus Now: When I was in college, one agricultural economics professor explained that manure did not have enough fertilizer value to justify the cost of land application. Fertilizer was truly “cheap” then! But, since the farmer had to dispose of manure, the costs had to be considered in farm profitability analysis. That’s what it came down to – manure was a waste disposal issue!
In general, that was the attitude in the ‘60s and ‘70s. Manure was a waste disposal item. In my early Cooperative Extension work, we held conferences where the topic was “Animal Waste Handling”. It was disposed of as quickly and conveniently as possible, usually on fields closest to the barns. Most manure was handled as a solid that contained large quantities of oat or wheat straw bedding. On bedded pack farms, it was disposed of two to four times per year.
The majority of dairy farms had tie stall or stanchion barns so the manure was hauled and spread daily. On those cold, winter days (and tractors often with no cabs), the manure was spread as closely and quickly as possible. This was usually on the well drained soils where the risk of getting “stuck” was the least.
When the weather was absolutely impossible, a well drained site was selected near the road edge and manure was “spread” in a pile close to the highway (or along a well-maintained farm driveway). No one paid much attention to the fact that it ran down the road ditch or nearest stream when snow melt occurred.
Did farmers calculate the value of manure in their fertilizer program? Occasionally, but it was not the common practice. Fertilizer was purchased and manure was considered “insurance”. It was applied every year on the most convenient fields.
Where are we now? When a group of soil test results come across my desk from a dairy or former dairy (or livestock) farm, it is easy to pick out the well drained fields that were close to the barn. Soil test Phosphorus (P) and Potash (K) levels are high. Supplements purchased for animal feed are excellent sources of Nitrogen (N) and P. Proteins and amino acids produce milk, but also produce nutrient enriched manure.
Plan and Recycle: Today we cannot let the nutrients run into the creek with the snowmelt. Those nutrients are crop/plant supplements, but they can also be environmental contaminants. They contribute to weed and algae blooms in the lakes and ponds. Excessive plant (aquatic weed) growth in water contributes to “stagnant” conditions. Nobody wants that! In the worst situations, they can contribute to well water contamination.
On large farms, whole farm nutrient management planning is a requirement. Farmers pay professional consultants to develop plans and employees/operators follow those plans. On smaller farms, the same attention to nutrient planning is desirable.
Fertilizer costs: The cost of plant nutrients has risen to the point where manure nutrients and nutrients from crop residues must be considered. Don’t overspend on fertilizer if it is not needed. Soil testing is the first basis for assessing what is available. Making use of the Pre Sidedress Nitrogen Testing (PSNT) supplements that practice. Put both to work on your farm.
Make use of PSNT: June is the time to pay attention to nitrogen requirements in corn fields. The pre-sidedress nitrogen test (PSNT) is one tool for estimating the nitrogen availability in soil when corn is about to make maximum growth. Early June is the time to take the soil sample for PSNT, when the corn is 6 inches tall.
Many consulting services and vendors offer the PSNT service or you can send a sample to the Cornell Nutrient Analysis Laboratory. Be sure to indicate that it is a PSNT sample. When the sample is taken, dry it as quickly as possible so nitrate levels don’t change due to ongoing bacterial growth in a warm, moist environment. The sample should be taken to a 12 inch depth as nitrate is mobile in the soil and moves up and down with soil moisture fluctuations.
What the numbers mean: Interpret the results with some common sense. Last year soils were cold and mostly wet. PSNT values at sidedress time were generally low, even though enough nitrogen had been applied as fertilizer or manure. With a few warm days and nights, the values went up rapidly.
The chemistry in measuring nitrate levels gives results in parts per million. With a 12 inch sample, the number needs to be multiplied by four because it represents four million pounds of soil. So a value of 20 means there are 80 pounds per acre of available nitrate at the time it was sampled. The soil bacteria that convert fertilizer and organic nitrogen to nitrate are most active in June. The nitrate keeps cranking out. A soil test number of 20 means there may be plenty there to finish the crop.
Err on the sufficiency side: A value of 25 is considered the cutoff where no sidedress nitrogen is recommended, but even that value needs to be assessed with some common sense. Manure and plowed or killed sods provide more nitrate from the organic nitrogen. Fertilizer nitrate is either there or gone. Weather (rain) and temperatures influence nitrate levels at any given sampling point.
On fields with no history of sod or manure, the nitrogen will be needed. On fields with an overload of manure or first year after legume/grass sod, there will be plenty of nitrogen. It is all of those other fields where the PSNT sampling will pay. If you have questions on interpretation, call Nate or Mike.
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