There are many different agricultural best management practices (BMPs) that can be used to address nonpoint source pollution from cropping, livestock, pastures, and silviculture. While some of the more common types of BMPs are discussed here, IDEM Section 319 grantees should also consult IDEM’s Agricultural Guidance for information on grant eligible BMPs. The guidance also details how pollutant load reductions are calculated for several popular agricultural BMPs.
Conservation Easements
A conservation easement is a legal agreement between a landowner and a land trust that restricts how a property can be used according to the landowner’s express wishes. The easement stays with the title to the property, allowing the property to remain in private ownership and to be used for purposes consistent with the conservation values of the property. The terms of the easement remain intact if the property is sold or bequeathed, thus requiring all future owners to abide by the terms of the agreement.
Conservation easements provide lasting protection to land and can be a valuable watershed management tool. While Section 319 cannot reimburse property owners for property value lost due to an easement, certain administrative costs associated with creating the easement are eligible. Likewise, certain administrative costs associated with purchasing land for permanent protection are eligible. See IDEM’s Urban BMP Guidance for details and more information.
Cover Crops
Cover crops prevent erosion, control weeds, and improve soil quality between plantings of primary crops, such as corn and soybeans. By planting cover crops, producers protect their topsoil during the winter months, increase soil nutrient levels, reduce fertilizer needs and protect their fields from weeds and insects. The economic incentive of cover crops can be calculated by weighing their cost against the nutrients and herbicides a landowner would typically apply.
Drainage Management
Drainage management uses water level control structures in conjunction with existing drainage tiles to maintain or decrease a field’s water table depending on the water needs of the crop. The system is most effective on slopes of zero to one percent. When used properly, drainage management conserves water, reduces nutrient loss to streams and increases yields.
Grid Sampling
Grid Sampling is a systematic approach to nutrient application on large farm fields. Historically, farmers counted rows and visually scanned their fields for atypical areas. Today, computers and guidance systems divide larger fields into squares or rectangles called "grid cells." Soil samples are collected from each cell and global positioning systems adjust the volume of nutrients being applied to the cell.
Manure Injection
Manure is a valuable nutrient and traditionally has been spread on fields as an inexpensive, convenient, and natural alternative to man-made fertilizers. However, manure can create water quality problems when it is misapplied. As livestock production becomes a larger part of Indiana’s agricultural economy, manure is sometimes field applied because that is the easiest disposal method, not because its nutrients are needed. This can lead to nutrient run-off and leaching into the ground water. Manure applied during the winter often sits on frozen ground and quickly runs off after small precipitation events.
Liquid manure injection offers a number of advantages over traditional techniques:
- Fewer odors;
- Ability to place nutrients directly into the seedbed; and,
- Reduced loss of fertilizer value.
Manure Staging
Before manure is applied to fields, it sometimes sits in fields or other staging areas until the farmer is ready to use it. Uncovered staging areas expose the manure to rain events and can lead to significant run-off. Manure staging facilities, typically a three sided structure with a roof, solve this problem. The facilities may also be used to compost litter and expired livestock.
Reduced Tillage Practices
Traditionally, land was plowed, or tilled, between plantings. The tilling would remove all vegetation and roots left from the previous harvest and leave the soil bare and unprotected from the forces of erosion. Conservation tillage reduces soil erosion, reduces the use of fertilizer by removing the need to plow, and leaves more organic matter on the fields. In most cases, it also is a relatively inexpensive BMP when compared to the acreage it benefits and pollutant load reductions it creates.
Rotational Grazing
Land must produce large volumes of grass and other plants in order to obtain maximum profits from pasture grazing. To use pastureland most effectively, intensive rotation grazing is suggested for many facilities.
The intensive rotational grazing system can be implemented by using short-duration grazing, rapid grazing, cell grazing and strip grazing. Pastures are fenced off into paddocks and animals are rotated between the paddocks according to the forage available and forage growth rate. Short grazing periods can increase the carrying capacity of the pasture without plants being damaged. Healthy plants lead to a less erosion-prone pasture.
System of Best Management Practices
U.S. EPA strongly recommends using systems of BMPs to improve water quality at a site whenever possible. The goal is to position two or more complementary BMPs on the landscape to create the maximum water quality benefit. For instance, reduced tillage combined with a water level control structure for drainage tiles reduces soil run-off, as well as decreasing the flow of storm water and nutrients to streams.
Two-Stage Ditches
When a ditch is modified to a two-stage design, narrow flat areas called benches are added to both sides of the stream. These benches allow the stream to meander and create room for water to collect during high flows. As water flows onto the benches and slows down, pollutants drop out, scouring decreases, and the soil and vegetation on the benches cleanse the water. Benefits to the landowner include a more stable stream, less undercutting of trees and increased wildlife habitat in streams and near ditches. Two-stage ditches may also significantly increase the time between ditch dredgings. Information on two-stage ditches can be found at: NRCS Stream Restoration Design Manual, Chapter 10 and G. E. Powell, et al. “Two stage channel systems: Part 1, a practical approach to sizing agricultural ditches” Journal of Soil and Water Conservation. Volume 62, Number 4, pgs. 277-296.