WSU-Puyallup

USDA SARE grant, pending

Project Contact and Coordinator:

Dr. Jon D. Johnson, 7612 Pioneer Way E., Puyallup, WA 98371
Tel. 253.445.4522; Fax. 253.445.4569; Email: poplar@wsu.edu

The proposed research will determine the feasibility of using fast growing hybrid poplar trees as an alternative crop for the application of liquid manure waste generated by dairy operations while at the same time produce a product that can generate additional farm income. Hybrid poplars can be integrated into existing manure management systems to utilize nutrients, as a buffer adjacent to environmentally sensitive areas including riparian and wetland areas, and as a odor barrier between farms and adjoining properties. The advantages of using hybrid poplar are: 1) high nitrogen requirement (>350 kg N/ha/y); 2) high transpiration rates to minimize leaching into the ground water; 3) deep root system (2 to 5m) with an extensive fine root mat at soil surface to maximize nutrient uptake; 4) minimal maintenance cost once established; 5) functionally longer application season due to perennial root system; and, 6) ability to generate farm income by harvesting trees after 8-10 years. The project objectives are to quantify nitrogen uptake from applied liquid manure by hybrid poplar plantations over time; determine nutrient uptake efficiencies of specific hybrid poplar clones; establish the maximum application rate (nitrogen load) and effective application season, and; provide demonstration areas for technology transfer to interested farmers.

A ten acre site at the Washington State University Research Dairy located in Buckley, Washington will be planted with 4 fast growing commercial hybrid poplar clones in a randomized block design. Clones will be nested within manure treatments consisting of a control, 1x, 2x or 4x level of manure solution applied at a rate based on tree uptake (1x) with each block replicated 4 times. The manure solution will be pumped from the storage lagoon through a 50-mesh filter to micro-sprinklers arranged throughout the plots. In each plot, 24 measurement trees will be sampled every two months for growth. Ten soil cores will be taken to estimate root biomass and N concentration. Litter traps will determine leaf fall and N recycling to the soil. Quarterly, four soil samples from each clone-manure treatment combination will be collected for complete physiochemical analysis and soil solutions from 30 and 150 cm will be analyzed for N to determine leaching. In addition, parallel measurements will be taken in existing poplar plantings at the Carnation and Wilcox Farms to further quantify manure nutrient uptake rates of different application systems on different soils.

Results from this project will document an inexpensive means for managing dairy manure waste while protecting ground and surface water from non-point pollution. By implementing this nutrient management alternative, many existing dairy farms in western Washington, and throughout the western region, will be able to manage their animal waste more economically while protecting the environment. The results will be transferred by publishing in peer-reviewed journals, presentations at national and regional meetings as well as by hosting visits at the demonstration site at the WSU Buckley Dairy for dairy farmers from throughout the western states.

The proposed research will determine the feasibility of using fast growing hybrid poplar trees as an alternative crop for the application of liquid manure waste generated by dairy operations while at the same time produce a product that can generate additional farm income. In this proposal, a stand of hybrid poplars will be established at the Washington State University Research Dairy located in Buckley, Washington (near Puyallup) to quantify annual N uptake rates for comparison with existing annual crops used in dairy manure management and will provide a demonstration area for technology transfer to dairy farmers. We will also use existing poplar plantings at the Carnation and Wilcox Farms to further quantify manure nutrient uptake rates in different application systems on different soils. As part of this research, we will identify specific poplar hybrids that have high N uptake rates, determine the duration of the effective application season and the optimum application rates in order to maximize manure utilization.

Management of manure nutrients associated with dairy farming is becoming critical to farm survival due to increasing regulations associated with surface and ground water non-point pollution (Alberts et al. 1978). In the states of Washington and Oregon, the issue of declining salmon populations, and the listing of some of these salmonoid species as endangered, has the potential of severely curtailing all agricultural activities including dairy operations. The use of hybrid poplars in an integrated manure management system has a number of advantages over existing systems. Poplar plantations can be integrated into existing manure management practices as a crop to utilize nutrients from the manure, as a buffer between farm operations and adjacent environmentally sensitive areas including riparian and wetland areas, and as a odor barrier between farms and adjoining properties. The advantages of using hybrid poplar are: 1) high nitrogen requirement (350 kg N/ha/y in two clones studied) resulting from their rapid growth; 2) high transpiration rates (up to 38 acre-inches per growing season in Washington state) that minimize nutrient leaching out of root zone and into the ground water; 3) deep root system (2 to 5m) with an extensive fine root mat at soil surface to maximize water and nutrient uptake throughout the soil profile; 4) minimal cost to maintain the crop once established due to perennial growth habit and ability of the trees to coppice (vegetatively sprout) after harvesting; 5) functionally longer application season due to longer growing season and a perennial root system; and, 6) ability to harvest the trees after 8-10 years for fiber or solid wood products providing additional revenue for the farmer.

Nutrients derived from animal manure has been shown to contribute to non-point pollution of ground water and ultimately leading to the degradation of the water quality of our streams and rivers (Alberts et al. 1978, Burwell et al. 1985, Chesters and Schierow 1985, Meyers et al. 1985). Nitrogen is one of the important nutrients that have been identified as originating from animal manure. Using DAFOSYM (Rotz et al. 1989), a simulation model of dairy nutrient management, Johnson et al. (1999) reported that between 30 and 60 kg N/ha was lost to ground water annually, representing between 3,000 kg N/yr and 13,000 kg N/yr for a medium (<100 ha) and a large (>200 ha) western Washington dairy farm, respectively. These values represent nitrogen loss under the best nutrient management conditions, suggesting that in reality, much more N is being lost to the ground water.

The use of fast growing trees to take up excess nutrients derived from waste coming from municipal and industrial treatment facilities has been demonstrated (Brockway and Urie 1983), and has been suggested for managing dairy waste. However, to date, no research has been conducted to quantify the amounts of nitrogen the trees are capable of removing, to identify which hybrids are the most efficient in N uptake, to determine maximum application rates or the duration N can be applied over the year.

Hybrid poplars represent some of the fastest growing trees in world (Dickman and Stuart 1983) and such growth is accompanied by the accumulation of large quantities of nutrients, especially nitrogen. Nutritional requirements and uptake rates of hybrid poplars have been studied in only a few hybrids (Heilman and Stettler, 1996). A one hectare stand of four year old hybrid poplar was estimated to contain 410 kg N, 100 kg P and 270 kg Ca . Annual nitrogen uptake rate at age four was estimated to be 350 kg/ha. Much of this uptake is due to the stand’s rapid growth and the tremendous leaf area that is produced by the trees. In addition, the presence of trees in a riparian buffer was found to increase the amount of N taken up during the winter, presumably by increased bacterial denitrification, resulting from the leaf litter returned to the soil (Haycock and Pinay 1993).

A fertilized four-year old stand of hybrid poplar had an annual biomass production of 70 Mg/ha/y with a leaf area index of 13.5 m²/m² (Heilman and Stettler, 1996) and averaged 15 - 18 m tall with diameters of 12 - 13 cm. After growing for 10 years in western Washington, these trees can grow to over 24 m tall with diameters of 25 cm which could provide merchantable size logs for various high value wood products such as plywood, oriented strand board and millwork.

The goal of the project is to demonstrate the feasibility of using hybrid poplar trees to effectively manage dairy waste while growing a crop that can provide additional farm income.

Specific objectives are to:

Quantify nitrogen uptake from applied manure solutions by hybrid poplar plantations over time;

Determine nutrient uptake efficiencies of specific hybrid poplar clones;

Establish the maximum application rate (nitrogen load) and effective application season;

Provide demonstration areas for technology transfer to interested farmers.