Manure - Curse or Resource? Depends on the Fall Conditions!

What a difference a year can make! At the beginning of November 2006, there had been very few opportunities for fall manure application, and options that followed best management practices were limited. Wet, saturated soils combined with late harvest and full manure storages resulted in surface application, sometimes to fields not targeted for manure. Compaction was the consequence and manure seemed to be a curse. 

In contrast, as of early November 2007, many are finished harvest. Fall manure application is nearly completed, with close to immediate incorporation and to soils at ideal moisture levels. After a dry growing season where regular previous manure applications have increased soil organic matter, soil moisture holding capacity and increased crop yields, manure seems to be a more valuable resource. 

With time on our side, the following are a few reminder tips for maximizing the long term value that manure can provide to the field. 

1. The ideal option is still to surface apply manure onto crop residue followed by incorporation of the manure as soon as possible after application. The time interval will depend on soil moisture levels, volume of manure applied, and weather (drying) conditions at time of application.
2. Be aware of application rates, especially in rolling fields or fields nearby to watercourses. A relatively low rate of 5,600 Imperial gallons (6,800 US gal) is equivalent to ¼ inch (6 mm) evenly applied across the spread width. Consider the slope and soil conditions at the time of application. If a quarter inch of rain fell in one minute, where could the manure move or runoff to?
3. Remember to take a manure sample for analysis. With increasing fertilizer prices, the potential reduction in inputs will be appreciated next spring. The best time to take a sample is during application. The sample should represent what went to the field, so it should include several sub samples taken at various intervals during application.
4. Timing of fall application will affect the amount and form of nitrogen in the soil. Fall application of liquid manure during colder conditions will result in higher amounts of nitrogen being available to the following crop. Cold conditions slow down microbial activity, resulting in a slowdown of the conversion of ammonium-N to nitrate-N. For solid manure, the opposite is true. Solid manure applied during early fall will maximize nitrogen available to the next crop since there is more time for soil microorganisms to work on converting the relatively high organic nitrogen portion of the manure.
5. Injection of liquid manure works best in dry soil conditions where macropores are disrupted and manure is fully incorporated throughout the full width of application. The least desirable situation is where high volumes of liquids lay in narrow bands closer to tile drains. Injection into wet soils will increase smearing, especially when combined with high, concentrated volumes being discharged from each injection point.
6. Surface inlets or hickenbottoms act as a direct conduit to surface water. In a wet year, the risk of water contaminated with manure moving through surface inlets increases. In a dry year it is easy to forget about this risk. Separation distances from hickenbottoms or inlets should be the same as for rivers or streams, unless it is certain that manure will be incorporated before the next rainfall event.
7. Liability issues are less likely in a dry fall, however record keeping of where manure was (or was not) applied is important for knowing where additional crop nutrients are required.

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