Western Perspective: SRWC Operations - Field Conversion and Plantation Establishment

Jake Eaton and John Finley, Potlatch, Boardman, OR

Abstract

Potlatch Corporation is in the third year of converting 22,500 acres (9000 hectares) of Northeast Oregon center-pivot irrigated farmland to hybrid poplar Conversion of this acreage will take place over a six year period with approximately 3,800 acres (1500 hectares) of new plantations established annually. The farm will provide a sustainable annual production of fiber beginning in the year 2000 and furnish 208 of the chip fiber for Potlatch's Pulp & Paperboard operations located at Lewiston, Idaho.

The Columbia River provides a stable source of irrigation water that in combination with the area's long sunny days, sandy loam soils, and 190 day frost-free growing season, creates an ideal environment for intensive poplar culture. Drip irrigation allows efficient delivery of water, fertilizer, and some pesticides to individual trees.

With three-year-old trees as our oldest operational age class, the Potlatch western perspective will focus on field conversion to drip irrigation, site preparation, selection and development of planting stock, and plantation establishment. State-of-the-art filtration, pumping, and water delivery systems are used to run the 200,000 gallon per minute irrigation system. Site preparation involves field leveling, soil ripping, and incorporation of pre-emergent herbicide. A rigorous clonal testing program from breeding new material to selections for operational deployment results in new clonal material that is mass propagated at contract stoolbeds. Dormant cuttings are processed and stored until spring planting. Post-planting activities include herbicide and manual release, cultivation, and pest monitoring.

Currently, 8500 acres (3400 hectares) are under management and construction is underway on the 3900 acres (1600 hectares) scheduled for planting in 1997 Early tree performance is meeting expectations, and production levels of a minimum of 40 bone dry tons of clean pulp chips per acre are realistic with a six-year rotation.

Introduction

Potlatch Corporation has acquired two contiguous center-pivot irrigated farms totaling 22,500 acres (9000 ha) near Boardman, Oregon for intensive farming of hybrid poplar. A declining supply of economically available residual chips motivated Potlatch to aggressively develop hvbrid poplar to augment its fiber supply. The decline has resulted from constraints on the Pacific Northwest timber supply brought about by environmental activism and a change in relative priorities of timber harvest versus other uses of public forest lands.

The Northeast Oregon location was selected for its optimal climate for intensive poplar culture. Long sunny days and a 190 day frost-free growing season provide abundant solar radiation. The soils are sandy, extremely well drained and allow year-round operability. The Columbia River provides a secure and dependable long-term source of clean irrigation water. Both farms have well-developed irrigation infrastructures with relatively senior water rights allowing application quantities of 4.5 acre-feet per year. The location also has excellent barge, rail, and truck access.

Ground was broken on the hybrid poplar program in 1993 with the conversion of the first 800 acres (320 ha) to drip irrigation. This acreage was planted in 1994. The 1995 and 1996 plantings were approximately 3800 acres (1500 ha) each and development will continue at this pace through 1999. Beginning in the year 2000, the farm will provide a sustainable annual production of high quality fiber and furnish 20~ of the chip fiber needs for Potlatch's Pulp & Paperboard operations at Lewiston, Idaho. Hybrid poplar fiber will mainly be used in bleached paperboard and tissue based consumer products.

Field Conversion

Potlatch purchased center-pivot irrigated agricultural land developed in the early 1970's. Prior to growing trees the farm land was used to grow a variety of crops including potatoes, onions, corn, wheat, and alfalfa in rotation. Conversion to drip irrigation is a requirement for poplar farming in our desert environment. Drip systems reduce system pressure requirements thus saving electricity, minimize water wasted by evaporation, minimize competing vegetation by reducing the area irrigated, and enable injection of necessary nutrients and some pesticides during the rotation cycle.

The existing center-pivot system presently waters crops in irrigated circles. This leaves corners of native desert outside of the circles that have never been farmed. The corners are very uneven from small sand dunes formed by years of blowing sand collecting around existing sagebrush plants.

Conversion to drip irrigation, inside and outside of the circles, occurs in two separate time frames. Corner conversion activities occur while crops are still maturing in the circles, 18 months before trees are planted. First, corners are mowed and large dunes leveled with a bull dozer. If there is a good grass cover and the ground is reasonably smooth, the area is left undisturbed. Disturbed corners are very susceptible to wind erosion. To prevent erosion, these areas are covered with straw. Specialized equipment shreds straw bales and spreads it evenly over the ground. Following this a grain drill is used to seed a winter wheat cover crop that will hold the soil through the following year. The drill also tucks the straw into the soil, helping to hold it until rainfall germinates the wheat and a cover crop is established. This process is generally completed by December, and these areas are ready for the final site preparation the following August.

Conversion activities inside the farmed circles begin the August prior to planting, when the final crops are being removed. Several activities occur in quick succession. The crop preceding hybrid poplar influences what happens next. Because of strong winds in our area, cover crops to prevent blowing sand and wind erosion are critical. The best crop to follow with hybrid poplar development is wheat. In this case the stubble is left and the fall and winter rains sprout the volunteer wheat resulting in a good cover crop. Potatoes or other row crops leave the field bare. In these instances winter wheat is sown and watered with the center-pivot.

Once the cover crop is established and able to exist until the onset of fall rains, the center-pivots are removed. Pivots are sold to buyers that are responsible for their removal. A quarter-mile long pivot with several towers can be removed in about two days. In coordination with the pivot removal, surveyors are brought in to layout the underground portion of the new drip system. In addition to staking the locations of new pipelines, the fields are surveyed and a grid system of check rows are located to ensure that tree rows are laid out straight.

When the surveying is completed a tractor mounted soil ripper is brought into the field to mark out the tree rows. This equipment rips two rows at a time, 10 feet (3m) apart to a depth of 24-30 inches (60-75cm). The operator works off of the surveyed grid of check rows and uses a marker bar to help locate the next row. If necessary, adjustments are made at the check rows to maintain straight rows ten feet apart. Consistent row spacing is critical to insure adequate space for tractor operation between tree rows. Once ripped the field is ready for irrigation construction.

Irrigation Construction

With 19,000 miles (30,400km) of drip tube and 26 million emitters, clean irrigation water is a must. Water from the Columbia River is moved to the plantations through mainlines and an irrigation canal. Screen filters are installed at pumping stations along the canal. Primary filtration for silt and organic matter takes place here. These filters automatically clean themselves when the sediment load reaches a predetermined level. Down stream of the filters, chlorine is injected into the irrigation stream to control algae.

The drip irrigation system uses the infrastructure of mainlines that supplied water to the old center-pivots. A manifold system is installed at the old pivot point that distributes water, fertilizer, and pest control products to four similar sized blocks. The underground construction begins with trenching and laying pipe on three sides of the block. The submain system is three sided to allow irrigation to be supplied from both ends of the block and facilitate automatic flushing of sediment and other contaminants from the system. Blocks are approximately one-quarter mile square. Flexible hose risers are attached to the below ground submains at the block ends, and serve to bring the water back to the surface. Drip hose will eventually be attached to the risers. Risers are lined up with the rip marks to get the correct row spacing along the pipeline.

Once the submains and riser lines are installed, the manifolds are assembled. The manifold consists of all the hardware necessary to distribute water to each of the four blocks. A master valve regulates mainline pressure to prevent excessive pressure on the drip lines. The manifold has an injection port for fertigation and chemigation. A final filter is installed after the injection port to prevent drip tube contamination from mainline breaks. Electronic valves regulate the flow to each block. Sensors for pressure and flow are also located at the manifold. Irrigation, injection, and system monitoring are all automated and controlled by a central computer.

Site Preparation

All of the field conversion activities take place between August 1 and November 1 of the year prior to planting. Beginning around the first of November, or as soon as soil moisture is adequate, rototilling begins. The rototillers are six feet wide and till 3-4 inches (7-l0 cm) deep. The tillers center on the rip mark and as they till, leave two groove marks on the soil. These marks are one foot apart and indicate where the soil was ripped. Tilling in this pattern leaves a 4 foot (3.2m) strip of cover crop between each tree row. This is done to provide wind protection to the young trees. Installed on the tillers is a sprayer that applies a preemergent herbicide right in front of the tiller. Presently, products with the active ingredient Trifluralin are used. Tilling takes place throughout the winter months as weather allows and is completed by March 1st.

Installation of the drip hose begins in January and is completed by the first of April. The hose arrives from the manufacturer in rolls of predetermined lengths, with emitters or drippers attached along the hose at preset spacings. These emitters are pressure compensating and will put out a constant 0.75 gallons (31) per hour over a range of pressures. These rolls are spooled out by a specialized implement mounted on a tractor. It uncoils three rolls at a time as the tractor moves down the row. Care is taken to lay the hose between the groove marks left by the tiller. This assures that the tree will be planted at the rip mark. Drip hoses and submains are flushed thoroughly before final connections are made. At this point the field is ready to be irrigated.

Clonal Testing

Potlatch's clonal testing program begins with acquisition of new plant material. Our strategy has been to do some breeding of our own and acquire additional clonal material through the research cooperatives we are active in. Further, we are constantly looking world-wide to secure possession of material that has not been tested in our environment. The hybrids we are working with are crosses between four poplar species, including P. trichocarpa, P. deltoides, P. niqra, and P. maximawiczii.

Newly bred clones enter a two-year screening trial, where the top 10-15%, based primarily on volume growth, are selected to move forward to the refinement phase. This three-year trial will begin to evaluate clone suitability to the Boardman environment, wood quality, and also expand our growth analysis work. Again the top 10% move ahead to the final verification test. It's 5-6 year duration is designed to thoroughly evaluate volume growth (including stem form), en-vironmental suitability, wood quality, disease and pest resistance. Current operational clones are included in the test and serve as the basis for comparison. Exceptional material can be identified at any time during the testing sequence and moved to clone banks to facilitate rapid scale-up.

Crosses between P. trichocarpa and P. deltiodes (TxD) and P. deltoides and P. nigra (DXN) have been used operationally. The TXD crosses generally produce the greatest biomass, but may not be as cold hardy as the DxN hybrids. The P. trichocarpa by P. nigra (TxN) crosses have shown great potential in testing and will be included in future operational plantings. To date, crosses between P. trichocarpa and P. maximawiczii (TxM) have not proven suitable to our hot and cold extremes, and our windy environment.

Clone testing is an ongoing process with new material entering different phases of the testing program each year. Many years are needed to confidently select new clones for operational use. Work underway in the Poplar Molecular Genetics Cooperative hopes to compress the testing period by identifying genes for desirable traits at an early age. Marker aided selection would also be valuable to select parents for future breeding.

In spite of long deliberate clonal testing programs, all of the risks associated with deploying new clones can not be eliminated. Extreme environmental conditions or disease and pest adaptations can result in failures. Long-term risks have to be balanced against productivity gains in a comprehensive clonal testing program.

Planting Stock Development

Clonal material is mass propagated at contract nursery stoolbeds. Plant material for stoolbed development comes from company clone banks or outside purchases. Single-bud cuttings, cut from clone bank whips, are greenhouse propagated for stoolbed starter material. More rapid scale-up using a controlled green wood propagation technique is also possible. Extreme care is taken to assure clonal integrity is maintained during scale-up. Suspicious greenhouse and stoolbed material is discarded to avoid contamination.

Depending on the level of scale-up desired, smaller stoolbed cuttings can be saved when processing production cuttings for additional stoolbed development. Stoolbeds are generally planted at a 1 x 1 ft. (30 x 30cm) density and intensively managed to assure proper nutrition and irrigation. The goal is to maximize yields by growing branchless wands with very little taper. Insects and disease are monitored continuously and controlled promptly. At full production one acre of stoolbed will yield around 150,000 operational cuttings.

Wands are processed when dormant. Crews harvest wands in the field and transport them to a processing facility. Most processing is done by hand. Cutters have lopping shears with length and caliper guides to aid in size determination. Generally accepted cutting size specifications for planting East of the Cascade Range are 8-9 inches (20-23cm) in length and 3/8-7/8 inch (lcm-2cm) in caliper. Processing is a labor intensive activity and accounts for 60% of the cutting production cost. Cuttings are double bagged to prevent moisture loss, boxed, and placed in dark cold storage at 28 degrees F.

Plantation Establishment

An average of six different clones are planted each year. Plantations are established in monoclonal blocks. Generally, all four irrigation blocks in a 160 acre (64ha) field are planted with the same clone.

In Northeast Oregon planting begins in early April. Just prior to planting, the fields are sprayed with herbicide. The two tank spray rig eliminates weeds that have escaped in the tilled strips and treats broadleaf weeds in the cover crop strips. All planting is accomplished by contract crews that can hand plant up to 240 acres (96ha) per day. wet spots along the drip tube indicate where to plant. Care is taken to plant the cutting with buds pointing up, the top bud flush with the ground, and within a few inches of the emitter. Planting is completed by late May. After the cuttings have been out for about six weeks, crews go through the plantations to replant any failed cuttings, move the drip tube to the west side of each tree, single multiple stems, and check emitter operation.

The first year after planting is critical to plantation establishment and performance. Hybrid poplar is not a shade tolerant plant. In areas where pre-emergent herbicide activity has been weak, new trees can be rapidly out competed by weeds. Grass competition can be controlled by any of the Fluazifop herbicides (e.g. Fusilade) without damaging the poplar. Unfortunately, at a young age poplar is not compatible with most of the common herbicides. Because of this, manual release may be the only option to remove unwanted vegetation next to the trees. Once trees are established, tractor operated cultivation does occur between tree rows to remove vegetation strips, left to provide wind protection for new trees.

Pest monitoring begins soon after planting. Grasshoppers, wire worms, cut worms, and ants can damage young plants. Although damage from these insect pests is seldom economically significant, grasshoppers can cause defoliation and have been managed with Carbaryl insecticides. Other insect pests monitored for and controlled when necessary during the first year are the cottonwood leaf beetle and various caterpillars. Mammalian pests include deer, gophers, voles, and indirectly coyotes. Deer browse is generally local and tolerated. Gophers eat tree roots and voles can girdle stems. The rodents seem to concentrate damage in local areas and can be held in check by poisonous baits and thorough weed control. Coyotes chew through drip tube resulting in leaks and moisture stress on the trees.

Summary

The level of activity in the plantations decreases after the first year. Irrigation, fertigation, and pest monitoring form the basis of plantation management until harvesting activities begin. Annual stand inventories are conducted on each age class to assess performance and identify problem areas. To date, average growth rates of 40 plus feet (12m) in height and 4-5 inches (10-13cm) DBH have been observed on trees nearing the end of their third growing season. It appears that our target tree size of 6570 feet (20-22m) tall and 8-9 inches (20-23cm) in DBH is realistic with a 6 year rotation.

File posted on March 17, 1998; Date Modified: February 21, 1999