Establishing Southern Pine Plantations – Site Preparation Options

1David Dickens – Forest Productivity Associate Professor, 2Bryan McElvany – Treutlen County Extension Coordinator, and

1David Moorhead – Silviculture Professor The University of Georgia 1Warnell School of Forestry and Natural Resources and 2College of

Agriculture and Environmental Sciences Some form of site preparation is needed to establish a southern pine (loblolly, longleaf, slash, Virginia, shortleaf) plantation. This is the case whether the site was just harvested of the last crop of trees, a pasture site, or a former cropland site. Southern pines are shade intolerant, therefore requiring a “free to grow” environment. Southern pines, like all plants have three major requirements: water, sunlight, and nutrients. The site preparation activity(ies) should optimize all three of these requirements. In most cases competition control is the most important objective in preparing a site for planting seedlings of any southern pine species. On soils that are somewhat poorly to very poorly drained (many Atlantic and Gulf Flatwoods soils), mechanical bedding is often needed to ensure adequate seedling survival and early growth. Some site preparation activities can also enhance the plantability of the site by reducing or moving logging debris.

Types of site preparation include: mechanical (chopping, disking, bedding, 3in1 plowing, subsoiling, and ripping), chemical (using soil, foliar, or soil and foliar active herbicides) or combinations of mechanical and chemical treatments.

Table 1. Advantages and disadvantages of mechanical and chemical site preparation Mechanical site preparation Chemical site preparation Generally improves site plantability Generally does not improve site plantability

(without a burn) Negligible to moderate competition control (short lived)

Good to excellent competition control (longer lived)

Slope limitations No slope limitations (when aerially applied) Used for improving soil conditions (ameliorating compaction, aeration, soil moisture status)

Does not improve soil conditions

Can reduce site productivity with certain activities if large amounts of topsoil is moved or displaced

No soil or debris movement, therefore no adverse effect on site productivity

Wider window to perform mechanical site prep Narrow window to optimize chemical site prep Historically, when preparing a site whose last crop was trees (cut-over sites); the first types of site

preparation for pine plantation establishment was prescribe burning (Photo 1) the site or chopping (Photo 2) and burning. Burning generally improves site plantability but can vary greatly intensity and effectiveness. Chopping effectively reduces logging debris and residual trees to ground level, is often followed by a burn, and facilitates site planting. Chopping generally greatly increases hardwood sprouting, in some cases by over 10-fold, therefore is ineffective at competition control by itself. Disking (Photo 3) as a site preparation technique was borrowed from farming practices. Disking improves soil tilth in the first 3 to 8 inches and serves as a short-term form of competition control, but is not recommended for slopes > 8% or somewhat poorly to very poorly soil drainage classes. Bedding (Photo 4) site preparation came along in the late 1960’s and caught on in the early 1970’s. Bedding, like disking, improves soil tilth in the bed and also improves near-term nutrient availability by churning organic matter and topsoil in the bed. Bedding is usually prescribed on somewhat to very poorly drained soils to raise the root zone above a perched water table and increase site plantability. Shearing, rootraking, and windrowing or more recently piling debris can greatly improve site plantability where there is a high

debris level. Depending on operator care, site productivity can be adversely impacted if one or more inches of topsoil are moved into the windrows or piles along with all the debris. Shear, raking and piling or windrowing is usually required prior to disking or bedding. A more recent mechanical activity to come along is 3in1 plowing (Photo 5) where ripping (or subsoiling), disking, and bedding is performed in one pass. This mechanical activity has just about replaced the shear, rake, pile, or windrow then disk or bedding activities where logging debris levels are low to moderate and on better drained soils. Chemical site preparation treatments (Photo 6) using soil, foliar or soil and foliar active herbicides have become quite popular since the 1980’s. Numerous studies in the last 20+ years have shown that on the majority of sites competition control is the single most important site factor to optimize southern pine seedling survival and growth. The most complete (volunteer pine and hardwoods or woody, shrub and herbaceous vegetation) and longest lasting competition control comes with herbicide use. For herbicides to be most effective, dosage and timing are critical. More recently (early 1990’s) tank mixes of herbicides to control a broad spectrum of competing vegetation has proven to be very effective. Since the late 1990’s fall application of tank mixes with a pre-emergence herbicide added to the formulation has further improved competition control, seedling survival, and growth.

Choosing the right site preparation treatment along with the tree species to plant, the seedling

source (for genetic and seedling quality/size attributes), and spacing are considered to be the most important forest management decisions for several reasons. These include: (1) total cost per acre since the establishment phase is usually the most costly expenditure in a rotation, (2) landowner financial constraints, (3) wood and non-wood (i.e. pine straw) products grown, (4) rotation age and number of thinnings, (5) stand uniformity, and (6) future stumpage prices. Choosing the right site preparation prescription is a case by case call. There is no single blanket site preparation prescription. To choose the best site preparation prescription question what is the single most limiting factor to early seedling survival and growth. Is it competition, soil moisture status (excessive, insufficient), nutrient availability (i.e. phosphorus deficient somewhat poorly to very poorly drained Flatwoods soils), or soil tilth (i.e. a hardpan).

Using recent UGA Warnell School of Forestry and Natural Resources research study findings,

chemical (herbicide use) site preparation produces more wood, more valuable wood (Figure 1), and a higher revenue per acre (Figure 2). The chemical site prep treatment also yielded a higher rate of return (10.2%) than the chop and burn (8.3%) or shear, pile, disk (7.7%) site preparation treatments over a wide variety of sites. When in doubt, get advice from a professional forester, Cooperative Extension Service, and/or state forester as to the best site preparation practice for your land.

Photo 1 (upper left) site preparation prescribe burning, photo 2 (upper right) roller chopping site prep, photo 3 (middle left) disking, photo 4 (middle right) bedding, photo 5 (lower right) 3in1 plow, photo 6 (lower right) aerial herbicide application.

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Figure 1. Loblolly pine chemical (pre- and post-plant) and mechanical site preparation

24-year pulpwood (dbh 4-9”) and chip and saw (>9” dbh) volume per acre.

Figure 2. Loblolly pine chemical (pre- and post-plant) and mechanical site preparation

24-year pulpwood (dbh 4-9”) and chip and saw (>9” dbh) value per acre.

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ChopBurn ShearPileDisk HerbBHerb

Pulpwood

Chip&saw

TMS 1st Qtr 2003 Prices:

PW = $18/cd

CNS= $60/cd

TMS 1st Qtr 2003 Prices:

PW = $18/cd

CNS= $60/cd

Costs/ac: Chop, burn, plant $172 Shear, pile, disk, plant $224 Herb, burn, HWC, plant $215