Growing Eucalyptus for Pulp and Energy

James A. Rydelius, Simpson Timber Company, Arcata, California

To produce pulpwood for a pulpmill that Simpson Paper Company owns near Anderson, California, Simpson Timber Company began, in 1987, to establish 4,047 ha of short-rotation, intensive- culture Eucalyptus plantations. The plantations are located in the northern Sacramento Valley on agricultural land of marginal quality that, prior to planting, had been used for only six to eight weeks per year each spring for grazing sheep. In this area of very hot and dry summers, it is necessary to irrigate the plantations to assure first year survival and in subsequent years to maximize growth. Because winter time temperatures sometimes drop to as low as 10 degrees to 15 degrees F. (-12 degrees to -9 degrees C), it is also very important to plant species that tolerate, at least to some extent, very cold weather.

Initially, two species, i.e. Eucalyptus camaldulensis and E. viminalis, were selected as being sufficiently cold tolerant while also capable of withstanding, under irrigation, the very hot summer temperatures. The species were, of course, also selected because they are suitable for the manufacturing of quality paper.

For the first five years of this plantation establishment project, the planting stock was grown from seeds obtained in Australia and, in some cases, from seeds collected from other plantations elsewhere in California. As the result of research carried out during these five years, Simpson, by 1992, had successfully developed a tissue culture process of micropropagation for E. camaldulensis. With this process, clones of the most rapidly growing and best formed individual trees are mass produced. Since 1992, therefore, all of the planting stock used for the establishment of these plantations has been of clonal origin with total plantation yields expected to increase dramatically over that which will be realized from plantations established with planting stock grown from seed.

The purpose of this paper is to describe the processes of site preparation, irrigation system design and installation, planting, and subsequent management of the subject plantations which have come to be known as the Tehama Fiber Farm.

As was mentioned above, the Tehama Fiber Farm project involves the establishment of a net 4,047 ha of Eucalyptus plantations. The plan is to grow the plantations on an eight-year rotation which means, then, that approximately one-eighth of that total area, i.e. 506 ha, must be established each year for eight years.

To provide the required summertime water, the plantations are drip irrigated. The topography is too irregular for furrow or flood irrigation. Drip irrigation systems require elaborate engineering that takes into account planned well locations, elevational changes, roads, streams, property boundaries, and various other topographical features. For this project, a system of approximately 506 ha is designed each year. The actual acreage is based on the best compromise of the above-mentioned factors rather than a strict adherence to the 506 ha figure. To minimize the number of wells that must be developed, each irrigation system is comprised of a number of irrigation blocks that can be operated independently of one another. The systems are also designed to allow for the future development of additional wells as water requirements increase with the increasing canopy cover of the developing plantation.

Upon completion of the irrigation system design, the first element of site preparation, i.e. soil ripping, begins. This activity is accomplished during midsummer, when the compacted clay soils, often with hardpans, are very hard and dry. Ripping involves the use of two D-9 Caterpillars pulling, in tandem, three steel shanks with hardened teeth that extend into the soil to a depth of 71 to 81 cm. With the soils so hard and dry, very thorough fracturing of the soil profile, including hardpans, occurs.

Immediately after soil ripping, the area of 506 ± ha is surveyed to accurately locate and mark, on the ground, the exact location of all underground pipes, including main lines, sub mains, valves, and other elements associated with the under-ground portion of the irrigation system. Construction of the system involves trenching, gluing together miles of PVC pipe of various sizes, installing the necessary valves, water filtration equipment, and, of course, the installation of pumps and pump engines.

It is late autumn or early winter when the above described activities are complete. No further activities are scheduled until the following April when the area is disced to eliminate weeds and grasses that germinated during the late winter and spring. With this discing, the area will remain essentially weed and grass free for the remainder of the year because the soil surface is dry without significant chance of additional rain, at least through the remainder of the spring, summer and early autumn.

The discing leaves a very well-prepared surface over which emitter lines are stretched and attached to "risers" that come up from the underground network of pipes that were installed during the previous late summer and early autumn. These emitter lines (and risers), spaced 3 m apart, are oriented as per the irrigation system design. Emitters are spaced at intervals of five feet along the emitter lines. When the emitter lines of each irrigation block (approximately 40.5 ha) are all attached to their respective risers and the ends crimped to prevent water from flowing out of the tubes, the appropriate pumps are started. After five to six hours of pumping, there is an obvious wet spot of soil at each emitter. A Eucalyptus seedling or plantlet is planted at every other wet spot along each emitter line. When completely planted, the spacing between planted spots is approximately 3 x 3 m which results in a plantation density of approximately 1,111 trees per ha.

Under these conditions, survival is surprisingly good with most irrigation blocks in excess of 95 percent and many blocks near 100 percent, even though temperatures at the time of planting may be as high as 32 degrees to 38 degrees C (90 degrees to 100 degrees F). Growth is also excellent with trees reaching 2.4 to 3.7 m by the end of the first growing season. Trees at harvest age are expected to be 24 m tall and 25 to 30 cm in diameter at breast height.

Irrigation during the first year totals approximately 15 ha-cm of applied water. The total is increased to about 31 ha-cm during the second summer and to about 61 ha-cm during the third and all subsequent years. During any given year, the amount will vary as the intent is to provide approximately 50 percent of measured evapotranspiration.

The irrigation system, in addition to delivering water, is used to provide accurately-measured amounts of nitrogen to the plantations. During the first year, approximately 2.7 kg of actual nitrogen is applied. The amount is increased each year until year five when total applied nitrogen is 56 kg per ha. Thereafter, the plantations continue to receive 50 kg of nitrogen per ha per year.

So far, pest problems have been minimal although grasshoppers will sometimes cause serious damage shortly after planting if not controlled. Voles will also damage trees during the second and sometimes third year following planting, but only where conditions of grass and weed cover provide them with a favorable habitat under or near the plantation edge. Vole populations and, therefore, vole damage can be easily controlled by reducing the area of favorable habitat.

This plantation establishment operation is managed by an organization consisting of five people in management and supervisory positions with three additional full-time employees who assist in monitoring plantation growth and who maintain all equipment including the irrigation systems. During the summer months, 10 additional people are employed as irrigators to operate the irrigation systems which must run essentially 24 hours per day to provide the required amounts of water where and when needed.

The irrigation system design is accomplished by contract as is most of the site preparation, irrigation system installation, planting, road construction, road maintenance, and certain other activities such as well drilling and pest control. At times, with contractors on site, the work force will increase to as many as 20 to 30 people or more.

Planting stock is produced in a nursery that is also owned and operated by Simpson Timber Company. Production of the planting stock involves the year-round operation of a tissue culture laboratory employing eight people as well as a four to six month nursery growing period that employs eight to ten people for periods of time when the planting stock is transferred from the tissue culture laboratory to the green houses and when the planting stock is packed for transport to the plantations for planting.

The subject at this conference, i.e. mechanization in short rotation, intensive culture forestry, is of vital interest to Simpson Timber Company as the day rapidly approaches when harvesting and processing of the wood from the Tehama Fiber Farm will begin. Cost-effective mechanization of all processes including tree-felling, accumulating and forwarding will be very important.

Since the primary purpose of these plantations is to produce wood for paper pulp, an improved system of debarking small Eucalyptus logs is needed. Only clean, bark-free wood chips can be used in Simpson's paper pulp making process. Also needed are improved systems for field chipping of the debarked logs.

It is expected that about 30 percent of the above-ground biomass produced, including the bark, will be unsuited for use in the paper pulp making process but will be quite suitable for use as fuel. Efficient systems for separating, processing and transporting the fuel biomass components would also be very helpful. At 30 percent, fuel biomass could amount to as much as 100 to 110 green tons per ha.

File posted on March 5, 1996; Date Modified: February 21, 1999