P2653 Black Willow as Biomass - msucares.com

Black Willow as Biomass

As the United States moves to increase its production This publication is designed to give landowners and
of renewable energy, biomass has become more important, others interested in growing biomass for bioenergy a
especially in the Southeast. Fast-growth tree species, first look at the current black willow research of the MSU
including poplars and willows, have been included with Forestry Department and the USDA Forest Service Center
energy crops, such as switchgrass, miscanthus, and energy for Bottomland Hardwoods Research.
cane.
Testing Planting Stock
Like any crop, trees grow best when matched with the
right soils. It is important to remember that the production In 2009, a test was established on the Mississippi
of biomass must be sustainable. It should also require few Agricultural and Forestry Experiment Station (MAFES) site
inputs, such as fertilizer or irrigation. near Stoneville to examine certain characteristics of black
willows. Specifically, scientists wanted to know how black
Unlike annual crops and poplars, black willows grow willow’s growth was affected by cutting length, cutting
well on soils that remain wet for long periods during the diameter, and depth of planting. They used dormant,
year. Because this type of site is not ideal for crops, it is unrooted planting stock for the tests. They were looking
perfect for growing biomass. In other words, growing for the best cutting size for black willow regeneration.
black willows does not remove land from food production,
but rather uses land that would probably be unprofitable Cutting length was set at 9, 15, and 21 inches. Cutting
otherwise. diameter was set at 3/8, ½, ¾, and 1 inch. The depth of
planting was measured by the length of the cutting left out
In cooperation with the USDA Forest Service Center of the ground. The 9-inch cuttings were planted to a depth
for Bottomland Hardwoods Research, Mississippi State of 4 and 7 inches; the 15-inch cuttings were planted to a
University has been exploring whether black willows depth of 7, 10, and 13 inches; and the 21-inch cuttings were
could be used as a source of biomass. In the past, black planted to a depth of 13, 16, and 19 inches.
willows have not been a sought-after species. As a result,
there is not much research on the species. However, the Cutting diameter, length, and depth of planting did
species has several key traits that make it a good biomass not have a significant effect on survival. In fact, only two
candidate. cuttings died during year 1, resulting in a 99.6 percent
survival for the entire study. This high survival rate shows
For example, black willows grow rapidly, root well, black willow’s excellent rooting characteristics. When the
propagate and coppice easily, and grow well on wet trees were measured after 1 year, researchers saw these
sites. Research on willows in the northeastern and north- trends:
central United States began in the late 1980s. Those studies
focused on shrub willows, many of which are suited to • The longer the cutting, the taller the tree at age 1.
much colder environments than ours is in Mississippi • The diameter of the cuttings and depth of planting did
(Kopp et al. 2001).
not affect height at age 1.
Willows represent a viable model for the northeastern
and north-central United States because the disease The 15-inch cuttings were 0.3 foot taller than the 9-inch
Septoria canker has severely limited the use of hybrid cuttings at age 1. The 21-inch cuttings were 0.7 foot taller
poplars. Septoria is also present in the Lower Mississippi than the 15-inch cuttings at age 1 (Figure 1). Planting
Alluvial Valley, which includes the alluvial soils found shorter cuttings will reduce age-1 height by about 1 foot.
from the junction of the Mississippi and Ohio Rivers to the This difference might seem small, but if you plant a large
Gulf of Mexico. It has killed many hybrid poplars. Eastern number of trees and harvest them when they are 1 to 3
cottonwoods are resistant to the disease but do not grow years old, the difference will add up.
well on wet sites. By contrast, black willows thrive on wet
sites. Today, no disease is known that would impact the
use of black willows.

Figure 1. Age-1 black willow in the 2009 cutting length study near Stoneville during the growing season (left) and
the dormant season (right).

Testing Black Willow Rooting In the first phase of the program, researchers collected
dormant black willow whips from the five different
Researchers examined rooting characteristics, as geographic areas shown in Table 1. Each geographic area
well. They wanted to track the growth of root systems included four stands, with each stand separated by at least
in relationship to bud break. Dormant, unrooted black 1 mile. Researchers collected five trees from each of the
willow cuttings break bud soon after planting in the early four stands and cut the trees into segments for cuttings.
spring (Figure 2). Early bud break could be a problem Thus, researchers collected 20 clones from each geographic
if those cuttings took a long time to produce roots. area, for a total of 100 clones. To provide more uniform
However, because black willows root so quickly, the trees material, these cuttings were placed into a nursery setting
have excellent survival rates. This trait is very important called a stool-bed for 1 year. The harvest of these whips
because trees grown for biomass production may number from the stool-bed provided the cuttings needed to test
thousands per acre. The rooting characteristics shown in each of the 100 clones. The cuttings were then graded for
Figure 2 are typical of dormant unrooted cuttings of black uniformity and planted at two MAFES sites near Stoneville
willows. and Prairie in 2010. Another two test sites were planted in
2011, with one near Hollandale and the other again near
Testing Genetic Material Prairie.

The ability to begin testing at the clonal level is Based on height and diameter performance of these
definitely an advantage. Being able to use various parts of tests, 25 of the best-growing clones were selected and
the tree, such as the stem or limbs, to produce a genetically planted at the MAFES site near the MSU campus. This test
identical individual tree allows researchers to produce differs from the others in that the number of replications
clones and capture the total genetic component. Black is much greater, which provides a more thorough
willows can be cloned from the main stem, known as a understanding of the selected 25 clones.
whip, from 1- to 2-year-old trees. The whip then can be cut
into pieces, known as cuttings, and used for regeneration.

Figure 2. Bud break of a dormant unrooted cutting of black willow 10 days after planting (left). Typical rooting
characteristics of a dormant unrooted black willow cutting, 3 weeks after planting (right).

Table 1. Geographic areas, river systems, and Conclusion
coordinates of the black willow cutting col-
lection program of MSU and the USDA For- Black willow may become a significant biomass
est Service Center for Bottomland Hardwoods species. It has many promising characteristics: rapid
Research. growth and production of vegetation, excellent rooting,
ease of coppice, and ability to grow on sites unsuitable for
Geographic area River system Latitude and longitude most agricultural crops and forest tree species. Although
no genetically superior black willow is currently available,
Tunica, MS Mississippi 34°50’N 90°16’W research is well under way to provide superior planting
stock within the next few years.
Rosedale, MS Mississippi 32°48’N 91°03’W
The research efforts by the MSU Forestry Department
Morgan City, LA Atchafalaya 29°41’N 91°12’W and the USDA Forest Service Center for Bottomland
Hardwoods Research will continue to provide both
College Station, TX Brazos 30°37’N 96°32’W silvicultural and genetic information on black willow as
a dedicated biomass source for biofuel and bioenergy
Liberty, TX Trinity 30°03’N 94°49’W production.

This test was also duplicated in 2013 and 2014 to Literature Cited
provide information on year-to-year differences as well as
environmental differences among the top 25 black willow Kopp, R.F., L.B. Smart, C.A. Maynard, J.G. Isebrands, G.A.
clones selected from the 2010 and 2011 trials. In 2016, the Tuskan, and L.P. Abrahamson. 2001. The development
required data from the 2013 and 2014 tests will be in hand of improved willow clones for eastern North America.
to define the very best of the 25 clones that can be released The Forestry Chronicle. 77 (2): 287-292
for bioenergy plantings.

Publication 2653 (POD-02-16)
By Dr. Randall Rousseau, Extension and Research Professor, Forestry.

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