Row Middle Management

The ground cover in an orchard must be managed just as the tree canopy is managed. The orchard floor can be divided into two distinct areas: the area between the tree rows, and the area directly underneath the trees. Row middle management in Pennsylvania orchards traditionally has fallen into three broad categories: (1) clean cultivation, (2) trashy cultivation, and (3) planting a permanent cover crop. The first two are no longer recommended because they tend to destroy soil structure by increasing soil compaction and erosion. They also create an ideal seedbed for the establishment of broadleaved perennial and annual weeds, which serve as a reservoir for viruses. The vast majority of commercial orchards in Pennsylvania are grown under a ground management system of a sod row middle with a vegetation-free zone underneath the trees. Sod between the rows prevents soil erosion, provides traction for equipment, adds organic matter to the soil, improves soil moisture and structure, and can be a site for beneficial predatory insects.

Grass covers used in row middles tend to grow rapidly and require frequent mowing. Perennial ryegrass, K-31 tall fescue, and clover are covers that have been traditionally grown in Pennsylvania orchards; however, a number of newly developed turfgrasses have been found to perform well as slow-growing cover crops. Because they grow more slowly, these new grasses require fewer mowings. They tolerate low-fertility soils, poor growing conditions, and heavy traffic, and they grow densely enough to crowd out weeds.

The addition of clover or other legumes is not recommended for orchard row middles. While they may provide additional nitrogen to the orchard, the release of that nitrogen is unpredictable. Legumes also can serve as reservoirs for tomato ringspot virus, which causes stem pitting in peaches and apple union necrosis in pome fruit.
A relatively recent criterion of grass cultivar quality is the presence of endophytes. Endophyte-enhanced varieties are recommended over those without endophytes. Endophytes are fungi that live within the grass plant and deter certain turf insects from feeding. Some species and varieties have naturally high levels of endophytes. Penn State researchers have been evaluating these grasses primarily for use in ornamental nurseries. This research and other observations made around the state indicate that hard fescue, chewings fescue, creeping red fescue, and slow-growing, turf-type perennial ryegrass can be used with success in orchard row middles. Each type may contain many acceptable cultivars. New cultivars regularly become available; check with your local supplier.

Using these grasses successfully depends on proper establishment practices. Failure to follow the steps below may result in a cover that is too sparse to be effective.

• Eliminate perennial weeds before planting. During their establishment phase, slow-growing grasses do not compete well with perennial weeds.
• Have soil tested and amended according to crop needs. Apply 20 to 40 pounds of actual nitrogen per acre when the cover is being established.
• Thoroughly work the soil before seeding. Any broadcast machine will do. Do not cover the seed with soil.
• A cyclone spreader, drop spreader, or Brillion seeder is recommended for planting seed. If a grain drill is used, disconnect the hoses at the grain box and let the seed fall to the ground. The light, fine seed of the fescues will not fall through the hoses.
• Seed the grass at a rate of 20 to 60 pounds per acre. The higher rates will produce a faster cover.
• The best time to seed is late August to late September. The next best time is mid-March to early May. If planted in spring, slow-growing grasses will not compete well with weeds the first growing season.
• Limit weed competition the year of planting by mowing weeds before they reach 10 inches tall. Timely applications of 2,4-D will prevent broadleaved weeds from becoming established.
• If desired, you may want to add a nurse crop of oats in the seeding mix at a rate of 5 pounds per acre to help establish a covering to prevent erosion.

Other comments
• To remain effective, turf-type perennial ryes need two applications of nitrogen each year at 40 pounds per acre. All others need an application of nitrogen only every other year.
• Chewings fescue and creeping red fescue grow taller than hard fescues and mat down more, but they seem to establish faster.