Over the last year I’ve been working for Dr. Amy Schmidt, the Manure Lady herself, here at UNL, and even though I grew up farming, this experience has given me a new understanding of how manure impacts soil, crops, and the environment. It also helped me understand better the reason for some of the regulations for manure use and how they are different between here and Germany.

What I’ve learned: The science of manure– it’s not just poop.

Of course, different countries have different farming practices due to different climates, soils, and market demands. Germany is a small country compared to the United States, with a high population density. Therefore, German farmers need to farm as efficiently as possible on the limited land they have available. In the part of Germany where our farm is located, the average yields of winter wheat, the most common crop in Germany, ranged from 126 bu/ac to 133 bu/ac in the last 5 years. To protect the environment from intensive farming practices, the German agriculture sector is heavily regulated. We use manure as a natural fertilizer because it has many benefits for the soil. Manure contains nitrogen, phosphorus, and other nutrients that plants need to grow. Applying manure can reduce erosion and is also an excellent way to increase soil organic matter, which increases the overall soil health. If manure is used properly, it can even save farmers some money.

The right rate

Before applying manure, it is helpful to test the soil to see what it needs. Applying the right rate of manure to the soil is important to prevent over-applying certain nutrients. This would not only harm the plants but also the environment. In Germany, annual soil testing is recommended but it is only required to test each field every six years. Currently, the use of organic fertilizer is limited to 170 kg total N per hectare per year (about 152 lbs. per acre). However, most farmers do not reach the Nitrogen limit because they reach the Phosphorus limit first, which is determined based on a fertilizer requirement calculation. This calculation is based on the average yield of the last 5 years, nutrient levels in the soil, humus content, how much organic fertilizer was applied in the year before and whether you planted cover crops or not.

The right timing

To use manure most efficiently, the timing of application to fields is important. The best time depends on the logistics of a farm, weather, and soil conditions. On our farm in Germany, we apply most of the manure in the spring before planting. The chance of nutrient loss in the spring is lower because manure is available closer to when a growing crop will use the nutrients. However, poor soil conditions can delay manure application and may further delay planting.

We also apply manure in the summer right before we plant cover crops. The great benefit of cover crops is that they can recapture nutrients in livestock manure and keep these nutrients from escaping into lakes, streams, and rivers.

In Germany, some farmers apply manure in the fall before planting winter barley and rape. If a farmer decides to do so, manure needs to be applied no later than October 1. During the colder months, the soil is usually water saturated or frozen, meaning the potential nutrient loss and chance for visible runoffs from fields are high. Since vegetation rests for that part of the year and the plants have no need for nutrients during that time, Germany has set a “blocking period” for arable land and grassland. This means that German farmers are not allowed to apply manure from November 1 to January 31.

Different manure application methods

Liquid or slurry manure has several application options including irrigation, broadcasting on the surface with or without incorporation and injection. Since 2020, German farmers are required to use emission reducing technologies that apply manure directly on the soil or into the soil. This reduces ammonia emissions and increases nitrogen efficiency.

Incorporating manure into the soil is important to reduce nitrogen loss and odors. Broadcasting manure, either solid or liquid, without incorporation, results in higher emission of manure gases and odors. If manure is incorporated by tillage within 6 to 12 hours of the initial application, emissions can be reduced by up to 80%. In Germany, this is not only recommended, but it is required. Slurry manure must be incorporated into the soil within four hours. In regions with increased requirements, manure must be incorporated into the soil within an hour. Injection methods are excluded from this regulation since the manure is already incorporated into the soil.

The regulations Germany introduced in the past years help to lower environmental impacts, reduce odors, and make sure farmers use manure as efficient as possible. However, the regulations also put more pressure on farmers. The time frame in which farmers in Germany are allowed to apply slurry manure to their fields is small. That means livestock producers must store their manure over a long period which can cause challenges. As a result, farmers bring out high amounts of manure from February 1 until planting. Depending on the weather conditions, the soil might be very wet, which increases the risk of getting stuck with the heavy farm equipment.

Everyone learning from different experiences

I’ve learned a lot about manure here in Nebraska, and I hope Nebraskans will be able to learn from my experiences as well. Even though most of the regulations I described are not required in the US, they are recommended. Soil testing, emission reducing technologies, and the fast incorporation of manure into the soil can help increase plant and soil health and ultimately improve yields while having the added benefit of knowing you went the extra mile to protect the environmental resources your community needs.