By Marilyn Thelen
As the price of commercial fertilizer rises, traditional cash crop producers are taking a serious look at manure as an alternative to commercial fertilizer.
When utilizing manure for crop production, consider both the give and the take.
The give (advantages):
- An available source of nitrogen, potassium and • phosphorus, and sulfur and other micronutrients.
- Increased soil organic matter.
- Improved soil quality.
- Potentially reduced cost of purchased fertilizer.
- A natural source of nutrients rather than one dependent on fossil fuels.
The take (challenges):
- The N-P-K values vary and are not in the right proportions for crops.
- Soil compaction may be a problem.
- Weed seeds may come with the manure.
- Manure has odor.
The fact that manure comes with several challenges has kept it predominantly on livestock producers’ fields. As fertilizer prices increase, however, the value of the product increases, and we begin to take a serious look at these challenges. Understanding the product and how to manage it to gain the greatest value alleviates the majority of the challenges. In addition, some producers claim even better yields with manure.
The most frequent question is what is the nutrient value of manure? There is no way to guess this, and with the potential value, why would we want to guess? A $30 manure analysis will take the guesswork out. The livestock producer should be able to supply a manure analysis to a crop producer. Manure can easily supply several hundred dollars’ worth of potential nutrients per acre – so don’t guess. Also, don’t guess on the rate -- calibrate spreading equipment and keep records to ensure that the nutrients were applied correctly.
Nitrogen (N) is a key element necessary for crop production and a valuable nutrient in manure. The N in manure is made up of ammonium-N, an inorganic form of nitrogen readily available to crops, and organic N, a slow-release form of nitrogen available to crops over time. Knowing both ammonium and organic N content allows us to manage to maximize the value of manure. Injection or same-day incorporation greatly improves the nitrogen retention; this greatly increases the
value of manure.
Manure analysis will also indicate the amounts of phosphorus (P) and potassium (K) available. Application of manure on fields that will have an economic yield response to P2O5 and K2O will give the best return. Current soil tests are valuable to direct the manure to the most needy fields.
The ratio of N to P in manure does not match the ratio taken up by crops. If you continually apply manure to meet the nitrogen requirement of crops, you may be overloading your phosphorus levels.
Moisture level and nutrient level of manure vary with species, storage type and bedding type. Current manure samples will help determine the value of manure and the application rate needed. This information is essential when determining the value of the product and the distance it can be economically hauled. The greater the nutrient content, the more cost-effective it is to haul the manure.
Soil compaction is a concern. Timing applications to correspond with dry field conditions as well as employing transfer technology to keep spreaders in the field and trucks on the road will help to reduce this concern.
Historically, weed seed in manure and the introduction of new weed seeds to fields was a concern. Current weed control technologies give producers more reliable options for controlling weeds if this occurs.
Being a good steward of the environment and being a good neighbor are also key to successfully using manure in a cropping system. Applying manure at agronomic rates, practicing timely incorporation or injection, planting a cover crop, and employing setbacks and buffers around sensitive areas are all management techniques that not only keep the nutrients in the field but also protect the environment and shelter neighbors from unwelcome odor.
The challenges of using manure as a part of the fertilizer program can be effectively overcome with management. As they say, if there is a will, there is a way. Commercial fertilizer prices are driving the will – management and creativity will define the way.
This article is from the September 2008 issue of the Scoop. To read the whole issue, click here.