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OSU Extension

College of Food, Agricultural, and Environmental Sciences

September 12, 2017 - 8:00am -- Anonymous

There continue to be questions regarding seeding and mulching of pipeline easements.  The pipeline soil restoration meeting held on August 31 addressed some of these questions so I will recap some of the comments and recommendations provided at that meeting.  Provided that soil was separated into at least three “lifts” (topsoil and 2 subsoil divisions) and then put back on top of the pipeline accordingly, the major obstacle to restoring soil productivity is compaction.  Compaction destroys soil structure and pore space negatively affecting the function of plant roots and the ability of plant roots to uptake nutrients.  Compaction also negatively affects water infiltration and drainage.

Fixing severe soil compaction can require mechanical and biological treatments.  Many pipeline easement contracts require the pipeline company to do deep ripping of the subsoil layer at a depth of 16 inches before the topsoil is replaced back over the pipeline easement.  This mechanical treatment is helpful to break up compaction and provide some soil aeration.  The more critical piece to restoring productivity to compacted soils is returning biological life to the soil.  This involves organic matter, soil microbes and plant roots.  All three are connected.

Soil organic matter helps to build soil structure, including soil aggregates and pore space.  Soil microbes work to mineralize and cycle soil nutrients as well as to help build soil organic matter and soil structure.  Plant roots provide sugars to feed soil microbes and as plant roots move through the soil they play a role in cycling nutrients, breaking up compacted layers, and building soil organic matter.  Adding livestock manures and/or composted plant materials provides organic matter, soil microbes and nutrients to soil.  For those landowners that have the materials, resources and time to make these applications on pipeline easements, it will be beneficial in the restoration process.  Regardless, all landowners need to give some thought to establishing a plant cover on easements.

The goal of establishing a plant cover should be to protect the soil from erosion and to begin to restore soil health and good physical properties to the soil. The Natural Resources Conservation Service (NRCS) has practice standards for cover crops and for critical area planting that list plant species options including soil preparation, species mixes, seeding rates, timing and mulch requirements.  Pipeline easements seem to fit the conditions of highly disturbed sites defined in the critical area planting standards.  That standard relies heavily on grass species to establish a plant cover.  Commonly recommended species include Kentucky bluegrass, tall fescue, perennial ryegrass, annual ryegrass, and orchardgrass.  Some mixture recommendations also include red clover.  Annual crops, including species commonly used as cover crops, are used to help return land back to agronomic row crop production.  This list includes the cereal grains such as winter cereal rye, winter wheat, barley, triticale and oats.  Other common species used as cover crops include annual ryegrass, oilseed radish, turnips, rapeseed, mustards and legumes such as red clover, yellow sweet clover, crimson clover, hairy vetch and winter peas. 

The limiting factor as we look at the calendar is planting date.  We are running out of growing days.  Just putting seed into or on the soil is not enough.  Plants require time to germinate and begin growing.   The value of plants in restoring soil health and productivity is dependent upon the development of a vigorous and well-established root system.  From an erosion control perspective there has to be enough top growth to buffer the soil from the impact of rain droplets and slow down water movement.  According to NRCS Critical Area Standards, perennial grass species should be planted by September 15.

Based on NRCS cover crop standards any planting mix should include a cereal grain.  Given the time of year, oats has the most limitations.  Oats should be planted by September 20. Unlike other winter cereal grains, oats will winterkill.  Winter barley, wheat or triticale can all be planted until about October 20 and winter cereal rye can be seeded until November 1. All will survive the winter and resume growth in the spring.  All cereal grains are rated excellent for erosion control and fair to good on minimizing surface soil compaction.  Annual ryegrass, due to the extensive root system it develops if seeded by September 20, is rated as excellent in minimizing both surface and subsoil compaction.  Oilseed radish is rated as poor for erosion control but good to excellent in minimizing surface and subsoil compaction, however seeding should be completed by September 15 to get the root growth needed to achieve those results.

Mulching, used alone or in combination with planting a cover crop, protects soil from erosion.  It is critical in situations where slope increases the risk of erosion before a planting is established.  It is also critical in situations where a crop is planted late in the year and will not develop enough growth to protect the soil.  The NRCS critical planting standard requires 80 to 90% of the soil covered with mulch. 

Contact the Wayne NRCS and SWCD office at 330-262-2836 for more specifics regarding easement seeding and mulching recommendations.