The following is the beginning of a three part series on Vegetative Filter Strips (VFS) and their role and use in reducing the potential for nutrient transport from crop and pasture fields due to overland flow. Information was excerpted from "Grassed Filter Strips Can Reduce Losses of Nitrogen and Phosphorus in Runoff", by D. R. Edwards, P. A. Moore, Jr., and T. C. Daniel. The original article appeared in the Better Crops with Plant Food Journal, Volume 80, (1996, No. 4), pages 8 to 11).
A couple of years ago NRCS and MSU personnel (specifically Valerie Oksendahl, Rich Fasching, and Dennis Cash began an investigation of the role of VFS for water quality protection in Montana. Filter strip plots were established at the Bridger Plant Materials Center and the Arthur H. Post Research Farm at MSU. These vegetative filter strip demonstrations have been useful at helping identify the extent to which nutrients and soil microorganisms are transported down slope from livestock manure stockpiles during erosion events. We have observed little movement of either nutrients or microorganisms, due much in part to the uptake characteristics of the plant materials being used and the soil properties. With that introduction.…some findings of the investigation by Edwards, Moore, and Daniel.........
Edwards, et. al., initiated a study to determine the relationship between manure application to pasture land and nutrients in runoff water. Their goal was to determine how nutrient loss in runoff was related to the rate of application of manure and intensity of rainfall following spreading the manure. The VFS crop was fescue and the soil was a silt loam. (Just to add a little interest and diversity, they used broiler litter, poultry manure, and swine manure). The manure was spread when the soil was relatively moist and then rainfall was simulated until runoff occurred for 30 minutes (the plots were only 20 feet wide, not a bad requirement for a VFS).
For one thing, runoff losses were the highest were the greatest amount of water was applied (4 inches per hour) and at the highest rates of manure application. However, nutrient losses amounted to less than 5 percent of the amount of nutrients applied with the manure. This is a good message for livestock producers and dairy operators concerned about containing waste from livestock confinement facilities.
Edwards, et. al, conducted a follow up experiment where they compared the impact of poultry litter, swine manure, and poultry manure with inorganic fertilizer. The researchers were interested in the nutrient losses from the various sources and they were interested in learning how nutrient loss varied with the number of runoff events following manure application.
The researchers found that the nitrogen runoff losses (total N) were generally the same for all sources, i.e., whether it was manure or inorganic fertilizer. This was mainly due to the fact that the nitrogen was more inclined to be leached into the soil rather than carried off sight with the runoff. Conversely, more phosphorus was lost from the plots that received the inorganic fertilizer than with those treated with animal manure.
Some other interesting findings:
§ Considerably more fertilizer and nutrients were lost in the first simulated storm following application than in succeeding storm events.
§ Runoff reached background levels of N and P after 2 or 3 simulated storm events.
§ Most nutrient loss consisted of soluble forms, as opposed to particulate forms. This was especially true for the inorganic fertilizer source. In the case of the manure, most of the particulate material remained in place and was not carried off with the runoff water.
The net result of these investigations was the determination that manure spreading does not seem to contribute substantially to the potential for nutrient runoff, due to high rainfall events when the manure is spread on grassed pastures.
Categories: Filter Strips, Water Quality
Date: 1997