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| First, what is your method of application and the conditions when you do it? Broadcast is least accurate and results in the most N loss if not incorporated very shortly after application. The other problem with broadcast is the poor spread pattern. All spreaders dump more in the middle of the spread and less on the edges, like a spray nozzle. You can try to correct for this by overlap.
Secondly, what kind of manure test are you doing? You should have one that gives you values for total NPK in the sample, and also an estimate of the N avalible the first year following application.
I dissagree with the poster who suggests that all N is lost with broadcast application. If put on in the summer or early fall and not incorporated, probably. We haul in the winter and I think that there is a considerable amount of N recovered by the crop. How much -- I don't know. I think more snow on the ground leads to more N retention.
You should determine if your manure source is using phytase as a feed additive or using straight dical. That will change the amount of P. Addition of phytase will take the P down, so you can then add manure to get the N level that you want.
Your maure fields should out yield commercial fertilizer, especially if you are supplementing with N. Your application method could also be the problem. If you are going to rely heavily on manure for fertilizer, you need to spend some money on equipment to do it right --- you need a flowmeter on the spreader. The application rate changes (a lot) even during a single load. The first part of a load dumps much faster than the last --- also, the first has a much higher P content. Also, some sort of injection toolbar will help combat N loss.
We use manure as our major fertilizer source and add about 30# of 28% at planting. Since we adopted this plan, we have not had a field average less than 200 bu corn. However, before we added a flowmeter to the spreader and drag line, we had problems with even application.
It takes a few years of manure history before you see maximum returns. Our highest yeilding fields have had manure for about 30 years. Those fields have P scores in the "excessive" range. The rule in my state is that you can't apply more P than removed by the corp. We usually adjust the manure rate so that we get a little over 100 # P -- that gives us about 150#N from manure (more or less depending on the barn). | |
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Soil Test results with manure
