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Capture manure’s value

As livestock and crop producers look at ways to manage tight crop production margins, many re-evaluate how manure resources might play into the bottom line. A quick calculation for liquid swine manure production reveals Iowa produces about $259,407,390 worth of nitrogen (N), phosphorus (P), and potassium (K) on an annual basis.

Capture manure’s value


As livestock and crop producers look at ways to manage tight crop production margins, many re-evaluate how manure resources might play into the bottom line. A quick calculation for liquid swine manure production reveals Iowa produces about $259,407,390 worth of nitrogen (N), phosphorus (P), and potassium (K) on an annual basis.

That’s $260 million worth of fertilizer inputs, which if managed correctly, can replace commercial fertilizer needs. You can do the same calculations for the poultry, beef and dairy industry. The following strategies briefly look at how you can capture that value.

Measure the need, calculate value. To measure the need, and subsequently value, we must take soil samples and have them tested to determine each field’s nutrient needs. If the soil tests high to very high, the manure P and K may not have much value to our cropping system, as we would not expect to see a crop response to extra nutrients. Value will come from the N and the micronutrients.

Access to solid and bedded manure may also improve physical properties of the soil, such as increasing water-holding capacity and infiltration. We also need to measure the nutrients in manure by taking frequent, good-quality manure samples. Manure sampling can show a large range in variability, but consistent sampling will provide more confidence over time. These two measurements are the keys to using manure as a nutrient resource.

Manage to reduce loss. Understanding nutrient availability to the crop can help you manage to reduce nutrient loss. Availability of nutrients is how we compare the manure nutrient supply for crops as compared to the nutrient supply provided by commercial fertilizer. Availability means the nutrients are ready for immediate use by the plant.

Commercial fertilizers are considered 100% available for plant use, and some manure sources have a higher ammonium-N concentration and are considered readily available for plant use. Loss is the physical, or biochemical, processes that cause nutrients to move off site where they are not available for plant use. Losses occur in ways we have some degree of control over and can manage. Understanding the difference between nutrient availability and loss helps us better manage the risk described below.

Actively manage risk. Timing, application location, application methods and managing for weather provide the most effective way to manage risk and reduce loss of nutrients:

Timing. If we recognize liquid swine manure N is 90% to 100% available, why then do we apply it so early in the fall when we don’t have a growing crop to use the N? Our goal should be to apply that source of manure when soil temperatures are cooling to reduce the rate of nitrification. If we can keep the N as ammonium-N, which is positively charged and attracted to the negatively charged soil, we keep that N source in place. The ammonium form does not leach. If soil temperatures are warm, the ammonium-N converts to nitrate. Nitrate moves easily in water. If we get a lot of rain in the fall or spring, we increase the chances of leaching.

Application location. Consider slope and proximity to water sources. If you surface-apply manure and get rain or snow melt that moves manure sources off the slope, physical loss of nutrients occurs.

Application methods. Injection or incorporation of manure into soil reduces volatile losses of N and can reduce runoff losses of P. However, one must weigh the risk of increased erosion to the benefits of reducing other forms of nutrient loss.

Weather. Avoid application of manure when rain is coming. Do not apply manure nutrients from any source in the winter on frozen or snow-covered ground.

Add an income stream. Selling or distributing manure gets those nutrients to acres that need them. Work with neighboring crop producers to access additional acres for manure distribution. Stay abreast of current manure plan requirements and other rules, such as manure leases, to maximize use of those nutrients.

Revise your growth strategy. Planning to expand your livestock operation? Do you own or rent enough acres for manure application? Can you secure adequate acres through manure agreements with neighbors? How far can you haul the manure to acres that need those nutrients?

Know the rules. Manure management is highly regulated. It is an expensive business if you do not know the regulations or choose not to follow them. Stay engaged with legislative action and current trends. Review your manure management plans, recordkeeping, emergency action plans and day-to-day routine.


Rieck-Hinz is the ISU Extension field agronomist in north- central Iowa.

Looking at corn
and climate

A February webinar conducted by Iowa State University explored results of the Climate and Corn-based Cropping Systems Coordinated Ag Project. Researchers at ISU and other universities have been working on this project since 2011 and have documented 130 findings. The webinar explains the major findings and offers recommendations on various corn production practices. Find it at Topics include tillage and drainage water management, cover crops, and farmer adaptation of practices to cope with impacts of climate change.

The five-year USDA research project is nearing completion. It is led by Lois Wright Morton, an ISU sociology professor. In 2011, Morton convened 140 researchers from 10 land-grant universities in the Corn Belt, along with researchers from USDA’s Ag Research Service, to begin a study of farmers’ perceptions and farming practices.

The various practices they studied have potential to provide resilience in times of drought, reduce soil and nutrient losses under saturated soil conditions, decrease field nitrogen losses, and retain carbon in the soil and ensure crop and soil productivity. The researchers collected measurements at 35 field sites with diverse landscapes and soils, and evaluated surveys of thousands of Midwest farmers. They entered all of this into one database for the team’s use.

More than 60 fact sheets, videos and other publications are found at In 2016, the researchers will continue studying and compiling data and publish recommendations.

This article published in the March, 2016 edition of WALLACES FARMER.

All rights reserved. Copyright Farm Progress Cos. 2016.

Nutrient Management

Crop Management

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