Over the next few years there exists the opportunity to have a major impact on upland habitat as well as address a more cosmopolitan social goal of improving water quality. This opportunity exists through a U.S. Department of Agriculture (USDA) Farm Bill program, the continuous Conservation Reserve Program (CRP). More specifically, conservation buffers are being promoted using this program. The USDA has set a goal to establish 2 million miles of conservation buffers by the year 2002.
WHAT DOES THIS GOAL MEAN FOR LANDOWNERS?

WHAT ARE CONSERVATION BUFFERS?

Conservation buffers are best described as strips or small areas of land in permanent vegetation, conservation buffers help control potential pollutants and manage other environmental concerns. Filter strips, field borders, grassed waterways, field windbreaks, shelterbelts, contour grass strips and riparian (streamside) buffers are all examples of conservation buffers.

LOOKS GOOD, SOUNDS GOOD, SO WHAT'S THE PROBLEM?

Unfortunately the USDA doesn't differentiate between wildlife friendly vegetative cover and just plain ground cover. In their eyes fescue or smooth brome is just as effective as any other vegetative cover type. In addition these areas are considered critical area seedings and call for seeding rates twice, or in some cases more, the normal amount. To fully realize the potential for this program to upland wildlife it is important that the proper vegetation be planted on these buffers. Although I am concerned about using too much seed, I am not as concerned about that as using the wrong kind of seed. It is therefore inherently more important to get native grasses planted on as many of these filter strips, grassed waterways, field borders, contour grass strips, and riparian buffers as possible. WHY NATIVE GRASSES, WHY ARE THEY BETTER?

I though you'd never ask. We all know that native grasses provide superior habitat to introduced exotic cool season grasses, or at least I'd hope you know. I'm going to consider that a given. Not only do they provide better habitat but they are better at doing the job buffers were designed to do, trap sediment and filter agricultural chemicals. I am going to base my discussion on a study and resulting publication, Design and Placement of a Multi-Species Riparian Buffer Strip System, by R.C. Schultz, J.P. Colletti, W.W. Simpkins, C.W. Mize, and M.L. Thompson, Iowa State University, Ames, Iowa from the Proceedings of the Third North American Agroforestry Conference, 16-18 August, 1993. The study took place in Iowa.

Buffers are not a new concept. Historically they have been planted primarily to introduced cool season grasses, at least through the midwest, midsouth and much of the south. The authors of the paper state, "Even with these best management practices in place substantial quantities of sediment and chemicals can still make their way into the riparian zone along streams and lakes. However in those watersheds where the riparian vegetation is maintained as a well-managed native community most of the sediment and agricultural chemicals from the upland are filtered before they reach the stream." Based upon these observations a study was conducted to look at the effectiveness of a buffer strip design which included native trees, shrubs and switchgrass. This design was compared to "pasture grasses similar to those that were present on areas grazed prior to the study." Since the study took place in Iowa I am assuming the pasture grasses were most likely smooth brome. I am going to talk primarily about the results as related to the switchgrass and make some inferences from that.

In addition to the effectiveness of the switchgrass in performing the functions of a buffer, researchers also looked at biomass production as a means to relate production that might be useful to a landowner. The theory being that biomass could be harvested to provide some benefit for the landowner while not compromising the integrity of the buffer and its functions. The study found that the biomass produced by the switchgrass was almost twice as great as that of the pasture grasses and much larger than that of the trees.

Probably the most compelling information was gathered in relation to the root biomass. Cores of soil were removed from between tree rows and shrub rows, from the center of switchgrass and control(pasture grass) plots and from soybeans and corn. Roots were extracted from the core samples by depth, dried and weighed. In the upper 17 inches of soil the root biomass was calculated as: soybeans 294#/a, corn 285#/a, pasture grass 1,514#/a, switchgrass 10,688#/a, ninebark 3,317#/a, silver maple 7,571#/a, poplar 3,117#/a and willow 8,640#/a. Switchgrass, by far and away, produced more biomass in the upper 17 inches of soil than any of the other vegetation, by more than a ton per acre. Keep in mind here the important comparison is between the pasture grass and switchgrass, where switch had 7 times more root mass. Now think of that in terms of stabilizing the soil, the amount of interface available to remove nutrients and agricultural chemicals and infiltration created by root structure in the soil profile. Root biomass at 17 to 30 inches for pasture grass and switchgrass was; pasture grass 303#/a and switchgrass 1,692 #/a. Root biomass at 30 to 43 inches was; pasture grass 267#/a and switchgrass 1,247#/a. Though switchgrass root biomass decreased significantly from 17 inches to 30 inches it did not decrease significantly from 30 to 40 inches. Compared to the pasture grass root biomass there was still 5 times more root structure at the lowest measurement. The study reports, "The greater root biomass of the switchgrass at the lower depths....provides more surface area for absorbing soil solution. This coupled with an above ground biomass which is almost twice that of pasture grass makes switchgrass far superior for trapping sediment and absorbing the water which infiltrates into the soil as a result of the slowed surface water movement."

The physical attributes of switchgrass have been proven but what about the performance? Measurements of nitrate nitrogen and atrazine concentrations were taken from within the crop fields, at the field-switchgrass interface, switchgrass-shrub interface and shrub-tree interface. Significant reductions in both nitrate nitrogen and atrazine were recorded at the field border and shrub borders, indicating the switchgrass was doing its job as a filter. In field nitrate nitrogen concentrations above 12 milligrams per liter were measured while concentrations in the buffer strip never exceeded 2 mg/l. In a June 29 sample, in field atrazine levels were near 4mg/l, at the field-switchgrass interface 3.4 mg/l, and at the switchgrass-shrub interface 2.2 mg/l, showing a significant decrease, nearly half, once the ground water had passed through the switchgrass strip. The switchgrass strip was approximately 23 feet wide.

I'd like to point out that though I have only focused on the switchgrass in this study, switchgrass strips were only part of a multi-species buffer strip. The design of the buffer strip as applied was for use as a riparian buffer strip and without the rest of the vegetative components, shrub strips and trees, will not function to help stabilize the stream channel as well as provide the filtering capabilities. The entire buffer design is approximately 66 feet wide. I did want to single out the switchgrass to point out it's soil holding capabilities as shown by the root biomass figures and ability to filter out agricultural chemicals. All too often introduced exotics are prescribed for buffers when it is obvious, as shown in this study, natives are better. Not just from the wildlife perspective but from the functional aspect as well.

I believe other natives would function as well as the switchgrass, though the root biomass might not be as much with big bluestem or indiangrass, particularly in the upper 17 inches of soil, it would most likely be greater, deeper. I do think however, their ability to absorb nutrients and agricultural chemicals to be as good.

Using native grasses as buffers is a natural application. In addition to the information presented above, native grasses are generally more tolerant of many of the agricultural chemicals than the exotic introduced species. From the habitat perspective, the use of native grasses in these borders, at least to quail, is providing habitat where habitat is sorely needed. Quail are an edge species. Planting native grasses in these field borders, contour grass strips, filter strips, grassed waterways and riparian buffers not only creates additional edge, it establishes nesting cover, escape cover, brood cover and roosting cover adjacent to additional preferred habitat, namely crop fields.

Quail use crop fields as bugging areas for their broods, dusting and loafing and feed on the grain either purposly left in the field or watse from the harvesting process. Furthermore, there is some recent research that indicates these field borders also serve as a nursery and refuge for beneficial insects that feed upon destructive crop pests, adding yet another reason to plant native grasses in conservation buffers.

Now that you know natives are better, be sure to let landowners and USDA know. If they ask, refer them to the research I referenced. Don't miss this opportunity that stands before us.

For more information about the continuous CRP contact the USDA - NRCS office in your county.