3) Biochar Amendment for Productivity

Biochar Amendment to Enhance Tomato and Melon Productivity and Protect

Against Phytophthora Root Rot Disease: 2014-2016

Western SARE Professional + Producer Grant


PI: Britney Hunter

Co-PI(s): Grant Cardon, Marion Murray, Diane Alston, Darren McAvoy, Shawn Olsen

Read the paper:

Preliminary screening of the effect of biochar properties and soil incorporation rate on lettuce growth to guide research and educate the public through extension

BACKGROUND:

YEAR ONE:

Evaluating biochar pyrolysis temperatures and application rates in preparation for the official field study in 2015-16. BIOCHAR APPLICATION DAY! 

Because biochar is a newly marketed product with properties that vary based on production methods and application rate, an initial biochar trial was performed in 2014 in preparation for the field study in 2015-16.  The objective of this study was to identify an appropriate field application rate and pyrolysis temperature to produce biochar for the Western SARE project “Biochar Amendment to Enhance Tomato and Melon Productivity and Protect Against Phytophthora Root Rot Disease”.  The future study will take place in cooperation with 3 local vegetable growers and at the USU Botanical Center in 2015 and 2016.  Lettuce was chosen in 2014 considering a short number of days to harvest and compact size for growing in pots.

METHODS

The Biochar used in this study was made by Western Renewable Technologies (WRT) in Linden, Utah from cherry wood sourced in Utah.  The biochar was divided into three different pyrolysis temperatures: 375°C, 475°C, and 575°C.  After the biochar was produced, half was masticated ¼” size pieces and half was pulverized to a fine powder.  The different chars were applied to silt loam field soil (pH 7.3) in pots at three different rates: 1%, 2%, and 3% by weight.  Fertilizer was added to all pots, and a fertilizer only treatment (no char), and soil-only control treatment was included.

Char samples were soaked in water for two weeks, with 20 grams of Jobes Organic Fertilizer added to “charge” the char.  Biochar samples and field soil was weighed dry before adding water.

Soaked char samples were mixed into silt loam field soil in a large bin, then put in a #3 nursery pot (~3 gallon).  This was very hard when there was too much water, making the soil very muddy.

Irrigation is for 1 minute every day with micro bubblers in each pot.

6 treatments, 3 rates, 3 reps, plus three pots/reps for fertilizer only and three for control.  Treatments: 575C Pulverized, 575C Milled, 475C Pulverized, 475C Milled, 375C Pulverized, 375C Milled.  Pulverized char is very powdery, while the milled is approximately ¼ inch diameter.  Rates were 1%, 2%, 3% char by weight.

Parris Island Cos lettuce seed has sprouted.  Soon we will thin plants to 3 plants per pot, allow them to grow for 9 weeks, then harvest them and take a fresh and dry weight per pot for data analysis.

Lettuce seeds and milled char in silt loam field soil

Data was calculated by taking one weight for each pot containing three plants, then dividing by the number of plants to get an average weight per plant.  

(PRELIMINARY) RESULTS:

Table 1.  Effect of biochar rate, pyrolysis temperature, and particle size on lettuce dry weight per plant.  The black bars reflect standard error, which expresses the variability within each treatment since there were 3 replicates/pots for each treatment.

SUMMARY:

There was a large variability in plant size, which is reflected in the standard error in Table 1.  Variability in the data may be attributed to inconsistency of water due to emitter malfunction on several occasions, and caterpillar feeding early in the development of the lettuce.  Also, the pre-soaking of the biochar led to an excess water, especially in the 1% treatments, which made the soil muddy after incorporation.  Working soil that is muddy significantly degrades the soil structure, and may have affected plant growth in this study.  Because of high variability in the plants and soil quality it is recommended this study be repeated.

However, the data collected here has improved resources needed to make a choice about producing biochar for use in 2015-16.  The biochar produced at 375°C and pulverized to a powder was the only treatment to exceed plant growth above the control at a 2%-3% rate.  Unfortunately, the pulverized char was quite difficult to work with, making it a less desirable option.  The 375°C masticated char at 2% presents a good compromise.  While other treatments had comparable weights, the 375°C is desirable because during production there is higher yield of biochar to wood at a lower temperature.   The study successfully accomplished the mission for 2014 to identify a biochar to use for the grower field trial in 2015-2016.