4R's of Manure Management

November 30, 2018

The 4Rs of Manure Management from Central Valley Ag on Vimeo.

Many of us have heard of the 4Rs that has been laid out by The Fertilizer Institute and endorsed by a wide variety of players in agriculture such as the American Society of Agronomy, NRCS, and the Ag Retailers Association. The 4Rs means using the right source, at the right rate, applied at the right time and in the right place. It’s an excellent concept for maximizing the benefit of crop nutrients such as nitrogen, phosphorus, potassium, sulfur, zinc, and other nutrients while limiting any negative environmental impact. 

How does that apply to manure management? Well, really, it’s no different. We need to know the nutrient (N, P, K, and more) value of our manure to make sure we know what the product consists of. We need to understand how nutrients cycle and what unique characteristics different manure sources have to understand application timing. We need to take that knowledge about our manure’s characteristics to make good decisions about application rate. We need to place the manure appropriately in our fields to make the most use of its nutrient value while limiting any chance of those nutrients reaching ground or surface waters.  

Let’s talk a little bit more about product. A lot of different types of manure get grouped into the term manure. We say, "hey, this field has low fertility. I wish I could get some manure applied." It’s like manure is some kind of magic fertilizer that will just fix everything in one application. Generally, that is not the case. Today I am looking at a couple of reports on my desk. One is liquid swine manure (product) with 59 lbs of nitrogen per 1,000 gallons of product that will be available for next year’s crop if we inject it into the ground (placement) to keep the ammonia in it from volatizing off. It also has 19lbs of phosphorus as P2O5 in that same 1,000 gallons.  

Let’s say that low fertility field I am going to apply this on is going into corn following soybeans. The field is very low on phosphorus. I have grid sampled it, and the soil test values range from 4 to 25ppm but average only 8 ppm across the entire field. I want to apply this hog manure on it because I know manure will help with my low phosphorus. I figure I need about 170lbs of N to raise 200 bu corn following soybeans. To get there, I am going to apply 3,000 gallons of this manure/acre which will give me 177lbs/acre N. At that rate I will get 57 lbs of P2O5 (19x3) per acre. The problem with this plan is my 200 bu corn crop will take off around 75 lbs of P2O5 and the 55-bushel beans following it will take off another 45 lbs or so. I have actually lost ground. If I want to use this manure source and still address my low P soil, I will need to supplement this manure application with some P fertilizer like MAP or MESZ. If I tried to use this manure to meet my phosphorus needs I would end up significantly overapplying nitrogen which is not the correct thing to do for our environment.

On the other hand, I also have a report on my desk for some beef feedlot manure. It has around 4 lbs of nitrogen per ton applied available for the first year crop and a total of 12.4 lbs of P2O5 per ton. Now if I apply 30 tons/acre of this product I don’t meet my corn’s N needs but will make a large dent in my low phosphorus fertility. I am applying 120 lbs of nitrogen but in this case two of the four pounds per ton available to my first-year crop is ammonium N which will volatize if I do not get it incorporated right away. I am no-till dryland, so that is not an option. I can only take credit for two pounds per ton of nitrogen or 60 lbs total. I will need to purchase another 110 lbs of nitrogen as commercial fertilizer to supplement the manure. The good news is I am applying 372 lbs of P2O5. That will meet the crop removal from my next two crops (120 lbs P2O5) and leave me over 250 lbs P2O5 to build soil test levels on this low fertility field. That 250lbs P2O5 should raise soil test P by around 15 ppm moving my average P level from 8ppm to 23 ppm. That’s what I wanted to accomplish on this field. Feedlot manure is the right product for this field. Since my soil test values vary from 4 ppm to 25ppm before I applied the manure, I would be smart to apply the manure using a VRT prescription to put higher rates in those low testing areas and lower rates in those higher testing areas.

Central Valley Ag can help you accomplish this.  

 By Tim Mundorf, CVA Nutrient Management Lead

Learn more about Nutrient Management at CVA by clicking here

Posted: 11/30/2018 10:25:36 AM by Kelli Reznicek | with 0 comments