Second year results using biochar as a soil amendment in a high-tunnel, poly bag growth system

The objective was to determine if using biochar a second year has an effect on yield and quality of the vegetables in a high tunnel production, polybag system.

Objectives

To determine if using biochar a second year has an effect on yield and quality of cucumber (Cucumis sativus, cv. Diva), tomato (Solanum lycopersicum, cv. Brickyard), basil (Ocimum basilicum, cv. Italian Large Leaf), Swiss chard (Beta vulgaris subsp. cicla, cv. Technicolor), snap dragon (Antirrhinum majus, cv. Rocket Mix) and lettuce (Lactuca sativa, cv. Tropicana) in a high tunnel production, polybag system.

Summary

Using a soil mix containing 0, 0.5, 1, 2, 4, or 8% by volume of biochar to Morgan’s 301 mix had little effect on yield and quality of cucumber, tomato, Swiss chard, basil, lettuce and snap dragons grown in a high tunnel, poly bag production system. The only statistical difference determined was in number two fruit in Diva cucumber. 

Methods

Soil Mix

In 2014 Biochar was combined with Morgan’s 301 Mix at a volume ratio of 0, 0.5%, 1%, 2%, 4% and 8% and placed into five-gallon poly bags. Biochar was supplied by Biogenic Reagents and met the following standards: 

Surface Area:           400 m2/g (min)

Ash                             5% (max)

Volatile matter           5% (max)

Carbon                       90% (min)

pH                               7-9 

Biochar was combined with Morgan’s 301 by placing the appropriate ratios into a cement mixer and tumbling until they were well mixed. The mix was then placed into the bags. The mix was moistened and allowed to sit a minimum of two weeks before planting. Bags with the soil mix were overwintered in the high tunnel. 

Planting

Six crop species were evaluated in 2015: cucumber (Cucumis sativus, cv. Diva), tomato (Solanum lycopersicum, cv. Brickyard), basil (Ocimum basilicum, cv. Italian Large Leaf), Swiss chard (Beta vulgaris subsp. cicla, cv. Technicolor), snap dragon (Antirrhinum majus, cv. Rocket Mix) and lettuce (Lactuca sativa, cv. Tropicana). The tomato was set as a transplant on 5 June, one plant per bag. Cucumber and Swiss chard were direct seeded 8 June, one seed per bag for cucumber and three seed per bag for Swiss chard. Snapdragons were planted 5 June, three plants per bag. Basil and lettuce were set as transplants, three plants per bag on 8 June. Weeds and plant debris from the previous year was removed prior to planting. 

Fertilizer

Plants were fertilized weekly with liquid 28-0-0 and 0-0-30 at a rate of 1# nitrogen and 2# potassium/acre/day. Fertilization began the week of 6 June and ended the week of 24 August. Brandt GH Vegetable Mix Extra was also added weekly at a rate of one quart/acre to supply Mg (2%) B (1%), Cu (0.25%), Fe (1.75%, Mn (0.5%) and Zn (0.5%). 

Weed control

Weeds were controlled by covering the ground in the tunnel with black ground cloth. 

Plant care

Plots were irrigated as needed through a drip irrigation system. No insect control was needed but it was necessary to control downy mildew through Ranman applications on the cucumbers. 

Harvest and data collection

Plots were harvested at the suitable stage for that species and graded according to commercial standards (tomato and cucumber), weighed (lettuce, Swiss chard, basil) or number of marketable flowers counted (snap dragons). Plots were standardized to one or three plants per bag and the data subjected to statistical analysis. The trial was planted and analyzed as a completely randomized design with four replications. Each plot consisted of four, 5-gallon poly bags.

Results

Just as in 2014, biochar treatments largely had no effect on the species evaluated and the traits measured (Table 1). The only significant difference was for weight of cucumber number two fruit. Reasons for lack of separation are unclear. Previous biochar studies have found no differences the first year but significant differences in subsequent years and that is why this trial was repeated over the two year period. Biochar has a greater effect in low organic matter and low nutrition soils. Morgan’s 301 is a high organic soil mix containing a significant amount of nutrients since cow manure is a main component. High initial nutrient and organic matter levels could explain the lack of separation. Fertilizer was applied in 2015 since previous trials using Morgan’s 301 a second year gave poor plant performance if no additional nutrients were supplied; especially micronutrients and plants were already showing low fertility symptoms at the end of 2014. Perhaps separation would have been observed if this was not done.

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