Unearthing Growth Secrets: Biochar and Cover Crops May Boost Yield in Sweet Corn Study

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Melia Braun and Jennifer A. A. Gubbels at Augustana University, Sioux Falls, SD and Evaluating the Effect of Biochar Application Combined with Cover Cropping on Soil Properties and Sweet Corn Yield

ARTi donated woodchip biochar for a project in Canton, South Dakota that sought to study how biochar would work with cover crops to affect soil properties and sweet corn yields. Cover crops are plants grown primarily to benefit the soil rather than for harvest. They are typically used to prevent soil erosion, improve soil fertility, suppress weeds, and enhance biodiversity.

Cover Crops in Northwestern South Dakota. Photo by Mieko Alley, Soil Conservation Technician, with the USDA Natural Resources Conservation Service, Bison, SD., USDA NRCS South Dakota

It has been demonstrated that cover crops and biochar both can enhance soil health and weed control. However, although cover crops can reduce weeds, they also can reduce yields. Biochar can enhance crop yield, help retain more water, and enhance soil health. While both cover crops and biochar have advantages, there is little to no research that combines the two practices. Jennifer and Melia’s project intended to address this under-examined topic. 

The study aimed to compare the effects of charged biochar and cover crops on soil nutrient availability and plant nutrient uptake in sweet corn. The study found no significant difference in weekly leaf count between treatments, indicating similar growth patterns. Biochar with weed control produced more cobs and increased their weight compared to no biochar with weed control. This trend was also observed in cover crop treatments with and without biochar. Although the results were not significant, the trends suggest that biochar may have provided water and nutrients during development, leading to increased yield and weight. The researchers will continue the study for another season to gather more data that may show a significant difference.  

“Our plan is to test biochar in combination with cover crops to control weeds using sweet corn as our primary crop.

The first step in adding the biochar.


Jennifer had a number of questions for us prior to the project that included biochar to manure ratio, how much and how deeply it should be applied. We recommended a ratio for biochar and compost of 1:1, with a 2:1 ratio for manure with a bit of water, to keep it moist but not wet. Additionally, we suggested inoculating the blend in the plot they were going to use to plant, allowing it to mature there for 2 weeks before planting. This way, manure will provide and allow nutrients and microorganisms to thrive. We recommended applying 3 to 4 inches of the blend on the top. There are 2 types of applications, general and localized in the planting row. However, we recommended using the general application by applying between 3 – 4 inches of the blend on top and then water abundantly.

The four 7’x7′ plots in the study with two of them having biochar. 


Adding the biochar to the treatment plots


Materials and Techniques

Two plots, each containing the same four treatments, were placed in 14 x 14 square foot plots. Biochar (44.8 lbs. per plot), obtained from ARTi, was charged (applied to and mixed with the topsoil) for two weeks before planting. Charging provides the biochar with needed microbial colonies. An early variety of sweet corn was used to ensure that the sweet corn will be ready in late July. Radishes were chosen as the cover crop due to the easy accessibility of seeds and were planted after the corn emerged. We measured emergence, number of leaves, fresh weight of cobs and stalks, and dry weight of stalks. Soil samples were analysed for nutrients and water-holding capacity at the beginning and end of the season. Field experiments were conducted at Good Life Farms in Canton.

The study found that biochar with weed control and cover cropping treatments increased the fresh weight of stalks in plot 1 and both plots. However, the dry weight of all biochar treatments was less than those without biochar, suggesting that biochar may increase water retention for plants. This research suggests that further studies could investigate the impact of biochar on plant growth, although statistical evidence is not available.

Plans for Future Research

Further research will aim to determine the impact of biochar on soil and crop growth. To achieve this, rye was planted as a cover crop in September 2023 for planned emergence in spring 2024. This is to be followed by planting sweet corn. Rye is a strong competitor of weeds. In order to not disturb the soil structure, no till practices will be observed next season. No-till practices in agriculture involve planting crops without disturbing the soil through tillage and in addition to preserving soil structure can also help to suppress weed growth, retain moisture, and reduce erosion. Biochar’s long-term effects on crops and soil are also crucial, therefore, year-over-year data collection is essential. Different soil types, such as heavy clay or loamy, may require different amounts of biochar for maximum benefit. These studies will be useful before adding biochar to the soil, as it cannot be removed once added.

More information on Augustana University’s Biology Research & Grants programs can be found here: (link)


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