Pine Wood Chips As An Alternative To Perlite In Greenhouse Substrates: Fertilization Requirements

In our last article (June 2014 issue), we discussed our research findings evaluating the activity and efficacy of plant growth regulator drench applications to a substrate amended with 20 percent pine wood chip (PWC) aggregates. To continue with our theme in highlighting the use of PWC aggregates (Figure 1) as an alternative to replace perlite in greenhouse substrates (Figure 2), this article will focus on evaluating the fertility requirements.

 

 

Proper Fertilization Can Minimize Nutrient Loss

While communicating with growers around the United States, it is all too common to hear them express a level of uncertainty about the use of wood-based substrates or components as an alternative for peat and pine bark. In the past, the perception and reluctance to use wood-based materials in growing mixes has derived from stories concerning the use of sawdust and resulting nitrogen (N)-deficient crops.

Since the initial concept to use saw dust as a substrate or substrate component, numerous universities have developed techniques to process wood, thus yielding wood components that have been intensively studied and reported as successful. However, consistent with previous reports about sawdust and crop health, researchers observed that plant growth in substrates composed of wood, or large portions of wood, had a tendency to become N–deficient as a result of high rates of N immobilization.

Such reports evaluated and compared the plant growth of multiple floriculture and nursery plants grown in 100 percent wood-based substrates to traditional peat or pine-bark-based substrates. Results of these studies indicated similar or minor differences in growth if plants were irrigated and fertilized more often in the 100 percent wood substrates, compared to peat or pine-bark-based substrates.

Generally, reduced plant growth in wood-based substrates is only a concern when fertility levels (primarily N) are below optimal recommended levels for plant growth and development. For example, work by Wright et al., (2008) found that ‘Baton Rouge’ chrysanthemums grown in a 100 percent wood-based substrate required an additional 100 ppm N, compared to plants grown in a peat-lite substrate composed of 45 percent peat, 15 percent perlite, 15 percent vermiculite and 25 percent bark (by volume).

Therefore, to counteract microbial N immobilization from a wood-based substrate or a substrate containing wood, growers must use a fertilization program that will supply additional nutrients needed by plants and minimize nutrient waste and loss from leaching. However, to our knowledge there is no information available regarding fertility recommendations for optimal plant growth in peat-based substrates amended with PWC.

Perlite Versus PWC Aggregates In Peat-Based Substrates

At North Carolina State University, we have developed a wood processing technique that produces bilocular and non-fibrous PWC aggregates as a perlite replacement. We investigated peat-based substrates formulated with 10 percent, 20 percent or 30 percent perlite or PWC aggregates. However, based on conversations with growers to determine the most common substrate formulation, we will present and discuss our findings of the substrates amended with either 20 percent perlite or PWC aggregates (Figure 3).

We prepared our peat-based substrates by amending either 20 percent perlite or PWC aggregates (by volume) and adjusted substrate pH to 5.8. Two plant species were trialed: ‘Profusion Orange’ zinnia and ‘Moonsong Deep Orange’ African marigolds (Figure 4, A and B). For zinnia, seeds were double sown directly into the substrates and after six days, seedlings were thinned to one seedling per pot, whereas the African marigold plugs were transplanted into the prepared substrates.

At each irrigation event, drip rings (Figure 5) were used to fertilize each plant with either a constant liquid feed rate of 100, 200 or 300 ppm N, provided by equal N combinations of Peters Professional 20N-10P-20K Peat-Lite Special containing 8.1 percent ammonium (NH4-N) and 11.9 percent nitrate (NO3-N) and Ultrasol Cal-Mag 13N-0.9P-10.8K Water Soluble Seedling Plus containing 0.3 percent NH4-N and 12.7 percent NO3-N. Using the Pour-Thru method, we extracted and measured substrate solution pH and electrical conductivity (EC) with a handheld Hanna pH meter on a weekly basis for six weeks. For each species at the first sign of anthesis, a final growth index (GI) [(height + widest width + perpendicular width) ÷ 3] and plant dry mass were determined.

Fertility Recommendations For PWC-Amended Substrates

Results of our study indicate substrate solution EC levels and pH values as recommended by Whipker, et al., (2001) can be achieved for optimal plant growth in PWC-amended substrates. At 200 ppm N, zinnia substrate solution EC was similar for both perlite- and PWC-amended substrates. For zinnia plants grown in perlite-amended substrates, recommended EC levels were maintained from 14 to 42 days after planting (DAP), while PWC-amended substrates maintained recommended EC levels from 14 to 49 DAP. A steady decline of EC levels from 14 to 49 DAP was observed when plants were fertilized with the insufficient N rate of 100 ppm N, compared to a steady increase in EC levels when plants received 300 ppm N.

Substrate solution EC of marigold plants was not influenced by aggregate type but rather by increasing N rate and followed a similar trend to the zinnias. For both species, substrate solution pH was influenced by increasing N rate and followed the normal response of decreasing pH with increasing N rate.

The recommended substrate solution pH 6.2 to 6.5 for both zinnia and marigold plants, was achieved in both substrates, when fertilized at 100 ppm N. The substrate solution pH of both species did not reach recommended pH values when fertilized with 200 or 300 ppm N. Maximum plant growth for zinnia (Figure 6) and marigold (Figure 7) was obtained when plants received 200 and 300 ppm N, respectively, and overall maximum shoot dry weight of both species, was determined when plants were fertilized with 200 ppm N.

Based on the results of this study and visual quality of plants grown in PWC-amended substrates, it is recommended that plants be fertilized with a water soluble fertilizer between 100 to 200 ppm N, without any additional N needed for optimal plant growth. The absence of significant nitrogen tie-up (immobilization) in substrates containing 30 percent PWC (or less) is most likely the result of the large particle size of the PWC aggregates. The PWC particles are larger and have less surface area than wood substrate components that have been previously developed/processed and evaluated in the past by researchers in the US. The uniqueness of the particle size of PWC is not fibrous like previous pine tree substrate materials, hence the lack of degradation and nitrogen depletion observed during greenhouse production.

When substituting PWC for perlite in greenhouse substrates, no adjustments to cultural practices or production of zinnia and marigold plants are needed. However, frequent monitoring of substrate solution EC and pH is recommended, as well as matching a suitable fertility program to the crop. The fertility recommendation provided here can maintain proper substrate solution EC levels and pH values, provide maximum plant growth and reduce excess N applied to zinnia and marigold plants grown in substrates amended with 20 percent PWC (by volume).

References:

Whipker, B.E., J.M. Dole, I.J. Cavin, J.L. Gibson, W.C. Fonteno, P.V. Nelson, D.S. Pitchey and D.A. Bailey. 2001. Plant root zone management. N.C. Community Flower Grower’s Association, Raleigh, N.C.

Wright, R.D., B.E. Jackson, J.F. Browder, and J.G. Latimer. 2008. Growth of chrysanthemum in a pine tree substance requires additional fertilizer. HortTechnology 18:111-115.

Topics:

Leave a Reply

More From Uncategorized...
Lavandula 'Meerlo' (Sunset Western Garden Collection)

March 3, 2015

Why You Will Still Grow Today’s Big Perennial 10 Years From Now

What will be the next big perennial? Breeders say it takes more than a splashy plant to distinguish itself in the market. Therefore, the question is not what will be the next big perennial, but rather what perennial performs well enough in the garden to have staying power in the market for years to come.

Read More

March 2, 2015

Avoid Surprises On The Delivery Dock

A call in advance about problems with a plant shipment to a retailer you supply goes a long way toward customer satisfaction.

Read More
Janeen Wright

March 2, 2015

Deliver Plant Quality That Trumps Price [Opinion]

The industry's goal is to have loyal customers who return to the same plants time and time again, not because of price, but owing to a plant brand that shouts top-notch garden performance and is synonymous with excellence, which gives them the secure knowledge that their investment will be worth every hard-earned cent.

Read More
Latest Stories

February 11, 2015

Benchmarks: Find Your Game-Changer

Refuse to accept the status quo in your organization. Explore possibilities until you find what works best for your company.

Read More

February 2, 2015

Variety Showcase: A Dainty Debutante

Lychnis flos-cuculi ‘Petite Jenny’ is a dwarf form of the popular Blooms of Bressingham® variety Lychnis ‘Jenny.’ This double-flowered little beauty was discovered by Paul Gooderham at Bressingham in a patch of its parent, ‘Jenny.’ ‘Petite Jenny’ produces masses of large, fluffy, double flowers like ‘Jenny,’ but with a more diminutive habit. The species goes by the common name “ragged robin,” but there’s nothing unkempt about ‘Petite Jenny’. An easy-to-grow, tidy little plant, it is suitable for any sunny or lightly shaded border and is also a good container candidate. Garden Performance Mass of bright pink double blooms beginning in mid-May. Sterile blooms provide a longer flowering period Erect, leafy flowering stems Forms compact, bushy clumps just 14” tall with an 18” spread Attracts bees, butterflies, hummingbirds and is deer-resistant Ideal for containers, front of borders, informal cottage gardens and as cut flowers Sun or part shade USDA Hardiness Zones 5 to […]

Read More

January 20, 2015

Register Now For Biocontrols 2015 Conference & Trad…

The first-ever conference, sponsored by Meister Media Worldwide and the Biopesticide Industry Alliance, March 3-5, offers hands-on, real-world technical advice on biocontrols to help you craft a “softer” pest management program focused on resistance management, MRLs and results.

Read More

October 6, 2014

Fighting Fall Foliar Disease: The Best Defense Is A Goo…

Managing foliar diseases starts with evaluating the greenhouse environment. Virginia Brubaker, GGS Pro Technical support supervisor for Griffin Greenhouse Supplies, shares some ways you can defend against fall foliar diseases.

Read More

July 11, 2014

Highlights From The 2013 USDA Floriculture Crops Summar…

The U.S. Department of Agriculture released its 2013 Floriculture Crops Summary in June. Here are some of the main findings.

Read More

June 16, 2014

Pine Wood Chips As An Alternative To Perlite In Greenho…

This is the third article of the four article series highlighting the production and use of pine wood chips as aggregates in greenhouse substrates. We found growers do not need to adjust their production practices when 20% pine wood chips are utilized as a perlite replacement.

Read More

June 4, 2014

Hortilux To Service Philips Indal Supplemental Lighting…

Hortilux Schréder (Hortilux) will be undertaking the warranty and service work for existing Philips Indal supplemental lighting systems for greenhouse horticulture. To deliver this service, Hortilux is taking over the entire stock of parts and production tools from Philips Indal Horticulture, so Hortilux is able to provide the full range of service and maintenance on these supplemental lighting systems, even after they are no longer covered by warranty. In North America, this will fall under the domain of PL Light Systems Canada Inc., a division of Dool Industries and a sister-company of Hortilux. In North America, PL Light Systems will contact the existing Philips Indal horticultural clients and work with them to quantify their service and maintenance needs. PL Light Systems offers a wide range of service and maintenance services, including on site supplemental lighting measurements, lamp and reflector measurements, trouble-shooting and repair maintenance and automated reflector cleaning services. These […]

Read More

May 29, 2014

Country Raisin’s Joins HGTV HOME Plant Collection…

The HGTV HOME Plant Collection announced Country Raisin's as a new annuals grower for 2014.

Read More

April 24, 2014

ePlantSource Announces Five New Partnerships

ePlantSource has announced the addition of five new suppliers to the list of partner companies who provide their products on ePlantSource.com. The additional partners will offer customers new products as well as expanded options for programs and locations.

Read More

April 16, 2014

Update: House Approves Bill To Raise ACA Full-Time Defi…

The U.S. House of Representatives passed legislation on April 3 that would raise the definition of full-time employment under the Affordable Care Act (ACA) to 40 hours per week.

Read More

March 27, 2014

Amidst Drought, Solar Desalination Allows California Wa…

California's Panoche Water District has implemented a solar desalination facility in response to the need for cost-effective solutions that would ensure the availability of sustainable water in the vital agricultural region. The facility, located in Firebaugh, Calif., utilizes renewable desalination technology from WaterFX.

Read More

March 14, 2014

Adaptive Plastics Announces Laurie Stribling Will Move …

Adaptive Plastics, Inc. has announced the promotion of Laurie Stribling to a newly created outside sales position. In her new position, Stribling will drive sales of Solexx greenhouse covering to commercial greenhouse and nursery growers.

Read More

March 14, 2014

BASF Empress Intrinsic Brand Fungicide Approved For Use…

BASF Empress Intrinsic brand fungicide has received supplemental labeling from the U.S. Environmental Protection Agency (EPA) for use on herbaceous and woody plants in greenhouse, nursery container and field production in New York.

Read More
Nicotiana 'Starlight Avatar' from Bioglow is the world's first light-producing plant.

January 31, 2014

Auction For ‘Starlight Avatar’ Went Live To…

BioGlow's auction went live on January 31 for nicotiana 'Starlight Avatar,' the world's first light producing plant.

Read More

January 29, 2014

U.S. Farm Bill Passed In The House After Years Of Indus…

The Farm Bill passed in the House of Representatives on January 29, and could be voted on as early as January 30 in the Senate.

Read More

January 2, 2014

MSU To Host 2014 Independent Plant Breeders Conference,…

If you want an opportunity to learn from and network with other plant breeders, new product development and market gurus and intellectual property experts, consider attending the 2014 Independent Plant Breeders Conference, October 30 to November 2, 2014. Held at the Amway Grand Plaza in Grand Rapids, Mich., educational sessions will fill the first two days, focused on helping independent breeders be successful, from technical aspects of breeding through product development and marketing. The final day will include tours of Western Michigan nurseries, garden centers and horticultural landmarks. Sessions will cover topics including: Basic and advanced plant breeding techniques Managing a breeding program Bringing selections to market Intellectual property management Market trends A formal agenda, list of sessions and registration details will be released in the spring. Meanwhile, if you have questions, contact Michigan State University’s Ryan Warner. Find information on hotel accommodations here. Independent Plant Breeders & Students of […]

Read More

November 19, 2013

Greenhouse Grower’s 2014 State Of The Indu…

Greenhouse Grower's State Of The Industry Survey is now open and we need your input. From crop and sales trends to the issues that keep you up at night, your responses to the survey are the basis for our annual State Of The Industry Report in the January issue.

Read More

November 19, 2013

Suntory Reveals Its 2014 Consumer Advertising Plans

To help growers and retailers prepare for the coming spring season, Suntory Flowers announces its multimedia consumer advertising plans for 2014. Leading lifestyle publications where advertising will appear include: • Better Homes & Gardens – April issue (Sun Parasol) • Southern Living – March issue (Sun Parasol) • Sunset – March issue (Sun Parasol) – Plus an extensive digital campaign March through May beginning with Senetti, then transitioning to Sun Parasol. Publications that already engage the avid gardener, where advertising will appear include: • Country Gardens – Early Spring (Senetti) and Spring (Sun Parasol) back covers • Fine Gardening – January/February (Senetti), March/April (Senetti), May/June (Sun Parasol) issues and the Container Gardening issue (Sun Parasol). A multi-faceted digital campaign will run March through May, starting with Senetti and then transitioning to Sun Parasol, while also featuring key annuals in The Suntory Collection. • Inspirations  – the official publication published by […]

Read More