While warm, clear weather allows us to get lots of field work done, it is not conducive to retention of ammonia from the manure being applied to the fields. Understanding that we often have no choice but to carry out tasks in imperfect conditions, here are some things to keep in mind:
When it’s dry, warm, sunny, and windy, it may take only 3 days to lose 50% of the ammonia nitrogen from unincorporated top-dressed dairy manure. Depending on your manure analysis and rate of application, that could easily mean that you have lost 50 pounds of nitrogen per acre just from ammonia loss! Incorporate if you can. If you cannot, account for the losses accordingly when thinking about nitrogen fertility for the rest of the season for that crop. In corn, a PSNT or the Cornell Adapt-N program can help you determine an optimal sidedress rate.
- This is the type of weather where urease inhibitors (included in urea-containing fertilizers) are more likely to pay you back quickly. Urea that is spread right now can easily be lost via volatilization – up to 15% losses over 10 days at 75⁰F, and more if we get light wetting/drying cycles.
- Manure testing is extremely important even if you expect significant loss. After it gets applied, it is too late to test it! Predicting how much more nitrogen you will need for your crop is impossible unless you know how much went on and you can make an educated determination about how much may have been lost.
- If you want to use the Cornell Adapt-N program to determine your sidedress rates for your corn, you NEED to have your manure tested. This test is designed to be a replacement for the pre-sidedress nitrate test and shows much potential for optimizing N-rates and reducing your work/frustration load.
The quality of any sample (manure or soil) is only as good as the process used to collect it.
- To understand the big picture:manure sampling basics
- The manure sampling protocol described by Dairy One is excellent.
- Cooling the sample slows microbial activity. The more quickly you cool the samples, the more accurate the manure test report will be. Freezing samples soon after collection and prior to sending it to the lab is ideal.
- You can pick up manure sampling kits at your local Extension office or you can print off the forms from the UVM Soils Lab website and use plastic jars of your own. Jars should be plastic, clean, have a wide mouth, and have a volume of about a quart,.
- Jars should be about ¾ full; filling them more can result in the jar rupturing in the freezer….
University of Vermont works with University of Maine for soil and manure testing. Cornell works with Agro-One (a subunit of DairyOne) for soil and manure testing. You can print off the forms necessary for sample submission at: