Biochar Amendment to Enhance Tomato and Melon Productivity and Protect Against Phytophthora Root Rot Disease
Fresh vegetables are important commodities in Utah; 6,560 harvested acres were produced on approximately 700 farms and valued at $16 million in 2007 according to the National Agriculture Statistics Service). Most of these operations are small farms (less than 15 acres) growing high value crops, including sweet corn, melons, and squash, and many are new farms. In a 2010 survey of commercial vegetable producers in Utah (252 responses), managing irrigation and nutrition for crops grown in arid and alkaline soils was among the most pressing need. Growers also identified concern regarding losses due to diseases, in particular soil-borne pathogens such as Phytophthora root rot. This project has involved working with Utah producers and USU Extension faculty to test whether a novel soil amendment called biochar can contribute to sustainable production by improving soil water-holding capacity, crop yield, and disease resistance in tomato and melon, two important crops in the state.
Biochar is a carbon-rich material similar to charcoal, produced by heating plant biomass (such as wood) through the process of pyrolysis in a closed system, under a limited supply of oxygen. Valuable bio-oils and heat energy are also byproducts of pyrolysis, which has led to the expansion of pyrolysis industries in Utah and the west. Biochar is mixed into soil as an amendment to increase nutrient and water retention, provide habitat for biological activity, and to sequester carbon. Biochar can take four to over 100 years to degrade. This property of biochar makes it a desirable amendment because it does not need to be applied every year. Biochar has little nutrient value on its own and is not a replacement for fertilizer. The positive attributes of biochar are seen primarily when biochar is moistened and mixed with an organic amendment or fertilizer. The effects of biochar on plant growth vary among soil types, biochar production practices, and application rates, which makes this study important to evaluating its value for agriculture in Utah and the arid west.
Our cooperating producers include three vegetable farmers, two fruit growers, and the Utah State University Botanical Center in Kaysville. Pettingill Farms in Box Elder County is a 130-acre, diverse, conventionally managed farm that grows fruits and vegetables. Zoe’s Garden in Davis County is a 20-acre, diverse, organically managed farm. Day Farms in Layton is a 90-acre, diverse, conventionally managed vegetable farm. Two Utah County fruit producers agreed to provide fruit tree wood to produce biochar for the project: William McMullin, McMullin Orchard, and Phil Rowley, Southridge Farms. So far we have only collected wood from McMullin Orchard. The USU Botanical Center is partly an Agricultural Experiment Station and partly an Extension education center including buildings, landscapes, and gardens that demonstrate environmental sustainability.
The primary objectives of this project are to engage vegetable producers in testing the effects of locally sourced biochar as a soil ammendment for plant and soil health and to educate the vegetable industry on the project’s findings.
1) Evaluate soil application rates of fruit wood biochar to establish parameters for subsequent trials growing tomatoes and melons on cooperating producer farms.
2) In collaboration with producers, evaluate how biochar amendment at the identified optimal rate influences water holding capacity, crop yield, and overall plant health of tomato and melon.
3) Determine whether the addition of the biochar product applied at the determined rate prevents or reduces susceptibility to the root rot disease caused by the organism Phytophthora.
4) Determine whether the use of soil-applied biochar could provide economic benefits to Utah’s vegetable growers.
5) In collaboration with project producers, prepare and deliver educational programming for other growers and the general public on all aspects of biochar as a soil amendment for vegetable production.
In summer 2014, a greenhouse trial was performed to identify an optimal soil application rate and pyrolysis production temperature to conduct subsequent field studies. Lettuce (Parris Island Cos) was grown in three-gallon plastic pots filled with silt loam field soil and amended with 4-4-4 organic fertilizer and biochar made from Utah-sourced cherry wood. Lettuce was chosen for its quick time to maturity. The biochar was produced by Western Renewable Technologies in Linden, Utah. Three pyrolysis temperatures (375°C, 475°C, and 575°C) and three application rates (1%, 2%, and 3% by weight) were evaluated. Mean dry weight (g) of plants was determined after a single harvest nine weeks after seeding. Lettuce growth was decreased with the addition of biochar in all treatments except 375°C, which is a common short term observation in similar studies. Lettuce grown with biochar applied at a 2% rate and pyrolyzed at 375°C was identified as the target rate for the subsequent field study.
Getting biochar produced for the container trial went smoothly; however there were complications getting a larger quantity produced. In 2014 Britney Hunter (PI) coordinated with William McMullin about picking up one hundred pounds of wood from the orchard. Darren McAvoy (Co-PI) picked up the wood and dropped it at Western Renewables Technology (WRT) in Linden, UT. Britney Hunter (PI) picked up the finished biochar packaged in five gallon buckets several weeks later and it was used for the container trial.
In 2015, 2,000 lbs of wood was requested from McMullin Orchards to create the biochar for the field study. Due to the warm winter, McMullin Orchards was pruning in February and requested we pick up the wood right away. A tree care company was contracted to chip the wood on site and deliver to WRT. The delivery went smoothly; however the wetness of the wood and the long slender twigs caused WRT’s pyrolysis machine to break. In March WRT was fairly confident they could still fulfill the order, but when it came time to plant late May only 50 lbs of cherry wood biochar had been produced. Additional Biochar had to be ordered last minute from a company in Colorado, Confluence Energy. The biochar form Confluence Energy is made from Lodgepole Pine. The biochar was delivered in early June, just in time to get the plants in for the growing season.
Cooperating with growers and planting field trial:
Planning and coordinating the process of planting vegetables on different grower’s fields was quite involved. Meetings were set up to identify the field location with each grower. Britney Hunter (PI), Grant Cardon (Co-PI), and Shawn Olsen Britney (Co-PI) took initial soil samples from each site for analysis to compare changes in fertility over time. Britney flagged off the planting area at each site and coordinated with Co-PI’s to facilitate a planting day. The treatments (Biochar+Fertilizer, Fertilizer Only, Control) were applied within each plot in a randomized design according to statistical guidance from an advisor at Utah State University.
Supplies were gathered over several days, then hauled to the field sites in three vehicles. It took a four hours total with nine people helping to apply the biochar and fertilizer treatments, plant tomatoes and melons, and water plants at three of the sites. The smaller quantity of cherry wood biochar was used to plant the plots at the USU Botanical Center a day earlier. Plants had to be watered by hand using watering cans for the first week after planting at most sites since the growers irrigation schedule was not frequent enough to establish small plants in the June heat. (See images below)
In four weeks initial plant growth data will begin to be collected by a research assistant funded through this grant. Moisture sensors will be purchased and installed to collect soil moisture data for different treatments, and tomato and melon fruit will be weighed so the total yield of tomatoes and melons can also be compared between treatments. The results will be stated in the following year’s annual report.
Phytopthora container trial:
On Monday, June 8, melon and tomato plants were planted into three-gallon pots and placed in a space in the USU Research Greenhouses. The soil used was a peat, vermiculite, perlite mix with no additional amendments. Ten of each crop were potted into soil mix alone, and 10 of each were planted into soil mix amended with 2% biochar (by volume). Each three-gallon pot held 7.5 qt of soil, and a 2% volume was 29.4 cups soil and 0.6 cups char. To make the mix, soil was prepared in batches to make enough for five pots of soil. Plants will be automatically irrigated for the next month, and then inoculated with Phytopthora in mid-July. Measurements will be taken in mid-August. See image below.
- Planting at Pettingill’s Farm
- Planting tomatoes at producer site
- Biochar and fertilizer before mixing at the USU Botanical Center
- Planting at Day Farms
- Lettuce container trial
- Planting tomatoes at producer site with Britney Hunter (PI) and Shawn Olsen (Co-PI)
- Mixing in biochar and fertilizer with small tiller
- Lettuce Container Trial Graph.pptx
- Phytophthora container trial
Impacts and Contributions/Outcomes
The container trial was successful at identifying the best relative application rate and biochar properties for the subsequent field trial.
Results of the container trial were shared with cooperating growers, with interested colleagues, and on the Utah Biomass Resources website (http://utahbiomassresources.org). Results have also been presented locally by Britney Hunter to USU Extension Faculty at the Utah Association of County Agriculture Agents summer meetings. The results successfully engaged other agriculture educators in understanding how biochar affects plant growth when added to soil.
Through grower collaboration, the field trial was successfully planted at four sites including: Pettingill Farms in Willard, Zoe’s Garden in Layton, Day Farms in Layton, and at the USU Botanical Center in Kaysville.
Active interest in our research has been expressed by research collaborators in different states as well as several pyrolysis companies we have worked with, indicating the impact of this research will benefit growers as well as sustainable energy (pyrolysis) industries in the west.
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