Impact of Biochar on Moisture and Nutrient Retention in Long Island Nurseries

Progress report for LNE19-384R

Project Type: Research Only
Funds awarded in 2019: $83,949.00
Projected End Date: 11/30/2022
Grant Recipient: Cornell Cooperative Extension of Suffolk County
Region: Northeast
State: New York
Project Leader:
Dr. Deborah Aller
Cornell Cooperative Extension of Suffolk County
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Project Information

Project Objective:

This is an innovative project that aims to enhance understanding of biochar’s impact on both field and container nursery production. Working directly with nursery growers in Suffolk County, our goal is to evaluate if biochar can contribute to on-going agricultural stewardship efforts by increasing nutrient availability and soil water retention, and decreasing leaching losses. The knowledge gained would increase accuracy of biochar use recommendations and rates for nursery producers both within the County and regionally.


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  • Mina Vescera (Educator and Researcher)



The goal of this study is to investigate the effects of biochar on nutrient availability and uptake and soil water retention in field and container nursery production. We hypothesize that biochar amendments will enhance moisture status and nutrient uptake by the crops, and hence, decrease runoff and leaching losses ultimately contributing to on-going agricultural stewardship efforts in Suffolk County. We also hypothesize that biochar application rate will impact soil water and nutrient retention, with retention increasing as biochar application rate increases.

Materials and methods:

Field experiments were established at one privet nursery and one Christmas tree farm in 2019. The second field trial will be established at another privet nursery in 2020. Container experiments were established at the Cornell University Long Island Horticultural Research and Extension Center (LIHREC) in Riverhead, NY and a local nursery on the North Fork of Long Island. In April 2019, a preliminary biochar column test was conducted using four different biochar types and a typical sandy loam soil from LI to evaluate which biochar type resulted in the greatest water retention. Results of this preliminary column test supported the use of a hardwood biochar in the field and container experiments. The hardwood biochar came from ARTiChar – Advance Renewable Technology International (Prairie City, IA). All the biochar material was inoculated for five days in a compost tea solution. In June 2019, both the container and field trials were established.

Container Experiments:

Biochar was substituted into the growing media at rates of 10, 20, and 30% by volume. Biochar was incorporated using two different methods (mixed versus layering at the bottom of the substrate). Containers with no biochar served as the control group. Treatments were marked as B10 (biochar at bottom 10%), B20 (biochar at bottom 20%), B30 (biochar at bottom 30%), C (no biochar control), M10 (biochar mixed into media at 10%), M20 (biochar mixed into media at 20%), M30 (biochar mixed into media at 30%). The experiment was arranged as a completely randomized design with each container serving as the experimental unit. Plants studied included boxwood (Buxus Green Mountain), California privet, and switchgrass (Panicum virgatum “Heavy Metal”) and LIHREC and only switchgrass (Panicum virgatum “Heavy Metal”) at the local nursery. Biochar treatments were applied at the time of planting into 1.5 gallon plastic containers in July 2019 for the privet and June 2019 for the switchgrass and 3 gallon containers for the boxwood. The media was a professional grow mix of 35-45% softwood bark with sphagnum peat moss, vermiculite, dolomite limestone, and a wetting agent.

The PourThru procedure (LeBude and Bilderback, 2009) was conducted weekly on all container plants between mid-June and the end of September. This procedure allows for continuous monitoring of container pH and EC levels so plant nutrient status could be monitored and adjusted as needed. Plant heath evaluations of the boxwood plants occurred once per month during the summer on 7/15/2019, 8/19/2019, and 9/9/2019. Data on leaf miner and leaf spot prevalence were collected and an overall plant health rating was given on a scale of 1 to 5. Plant heath evaluations of the switchgrass plants occurred during the summer on 7/15/2019, 8/5/2019, and 8/19/2019. Data on number of flower stems per plant, disease, chlorosis, and overall plant health were also collected. Total leachate was collected from the boxwood and switchgrass containers twice in September and twice in October to measure ammonium and nitrate concentrations. Destructive sampling of the switchgrass containers at LIHREC occurred mid-September to evaluate differences between treatments on shoot and root growth in year one.

In March 2020, an initial PourThru was conducted on the overwintering (2019) boxwood and switchgrass plants prior to fertilizing them for the season. PourThrus were conducted every two weeks to monitor EC, pH, and N levels, and periodic plant health evaluation data were collected on the 2019 plants until they were destructively sampled in mid-June. At that time data were collected on root ball and shoot dry weight. 

Image: Example of a switchgrass root ball with the 30% mixed vs. bottom biochar treatments and control. 


Image: Visual comparison of the aboveground growth for the switchgrass biochar 20% bottom treatment. 

On May 8th, new switchgrass plugs were potted up at both the LIHREC and on-farm nursery site. Again, N leachate and PourThru data were collected every two weeks and monthly plant health evaluations were conducted until September. LIHREC trial plants were destructively sampled in early September, and root and shoot dry weights were measured. Switchgrass plants at the on-farm nursery site were again left to overwinter in a covered hoophouse. At the on-farm nursery, Hobo waterproof temperature sensors were installed in 3 of 5 containers per treatment to continuously monitor container temperature of the substrate through winter and spring until the plants will again be destructively sampled in mid-June. 

Images above: Relative size of temperature sensor (top left), configuration of the sensor (top right), installation of the sensor into a container (bottom left), sensors installed as indicated by the yellow tag (bottom right) 


Field Experiments:  

The field experiments were established using a completely randomized block design with subsamples. Ten consecutive plants per treatment was set as the experimental unit. Prior to biochar application soil samples were collected from each farm. Biochar was applied at rates of 5, 10, and 15 tons/acre and a no biochar control for a total of five replications per treatment to California privet (Ligustrum ovalifolium) and Douglas fir (Pseudotsuga menziesii). One week after applying the biochar, lysimeters were installed in two of five replications in each treatment at both field sites. The two cooperating growers followed their standard practices for weed management and fertility throughout year 1 of the trial.

Additional data were collected on the number of terminal buds on the leader and height for the Douglas firs. Soil health samples that measure the soils physical, chemical, and biological properties were collected from all field sites prior to biochar application. The soil health samples will provide growers with a comprehensive assessment of the quality of their soil and provide them with both short- and long-term management suggestions. Time domain reflectometer (TDR) probes were installed at the two field trials established in 2019 to continuously record soil moisture, electrical conductivity (EC), and soil temperature.

Compost tea used to inoculate the biochar

Mina Vescera potting up switchgrass for the biochar container trial

Using the PourThru method
Biochar application to a field of Douglas Fir Trees
Biochar application to a Privet field
Year 1 privet planting with biochar
Debbie Aller using a soil auger to install lysimeters
Mina Vescera mixing the clay slurry for lysimeter installation
Mina Vescera installing a lysimeter
Installation of the TDR and soil water potential sensors into a Douglas Fir field
TDR probe inserted at a depth of 4"


Year 2 - 2020 Field Updates

Data collection continued throughout 2020 from the two field trials installed in 2019. Unfortunately, the final participating grower located on the South Fork of Long Island that grows California privet was no longer able to participate. However, another grower on the North Fork that grows California privet was willing to participate in the trial. Trial installation was further delayed due to restrictions imposed by the Covid-19 pandemic. But eventually, lysimeters and soil sensors were installed in June and July, respectively, with the biochar treatments installed in early October at the final farm. For all field trials, three plant health evaluations were conducted over the course of the growing season. Lysimeters were checked for soil water extract after every rain event beginning in May and ending in November; soil water samples were kept refrigerated until shipped to a nutrient analysis laboratory for ammonium and nitrate analysis. Soil samples were collected from all growers in September and October. No tissue samples were collected because plants were still too small to collect a large enough sample across all treatments. Similarly, no destructively sampling was conducted in 2020. 

Image: Visual of soil layers found during lysimeter installation at the third North Fork privet grower field.

Soil type is Riverhead sandy loam with mean soil organic matter for control plots of 2.8%(samples from biochar treatments will be collected in spring 2021). From left to right, approximate depths of 0 to 6 inches, 7 to 13 inches, 14 to 20 inches, and 21 to 28 inches.

Image: Installation of the third field trial in early October 2020. Plants are California privet (Ligustrum ovalifolium).

Year 3 - 2021 Updates

Data collection continued throughout 2021 at three field nurseries, one container nursery, and the LIHREC. 

Container Experiments

To measure any potential effects biochar had on overwintering container plants, Hobo waterproof temperature sensors were installed in overwintering switchgrass (Panicum virgatum) containers at the cooperating nursery. Data were continuously recorded from October 2020 until mid-June 2021 from 3 of 5 containers per treatment. Liner plants had been transplanted during the 2020 growing season and were overwintered in a plastic-covered hoop house. In March 2021, an initial PourThru was conducted on the overwintered switchgrass plants prior to fertilizing them for the season. PourThrus were conducted every two weeks thereafter to monitor EC, pH, and N levels. Periodic plant health evaluation data were collected until the plants were destructively sampled in mid-June. Dry root ball and shoot biomass weight were recorded. After weighing, shoots were collected for tissue nutrient analysis.

In May 2021, Japanese forest grass (Hakonechloa macra 'Aureola') and California privet (Ligustrum ovalifolium) liners were potted up at the LIHREC. New switchgrass plugs were potted up at both the LIHREC and the on-farm nursery site. Due to few differences in 2019 and 2020 among treatments, the biochar rate treatments in the 2021 container trials were increased to 20%, 35%, and 50% (v/v) plus a no-biochar control. Further, the bottom biochar treatment was discarded as there were also no differences seen with this method of biochar use in the first two years of the trial. Lastly, we used two different biochars: hardwood biochar and oat hulls biochar. The biochar was charged prior to use by the biochar producer with a fertilizer, brewer yeast, and microbial blend.  

Again, N leachate and PourThru data were collected every two weeks in addition to periodic plant health evaluations. All container plants were destructively sampled at the end of September. Shoot and root dry weight data were collected on all plants.

Field Experiments

Soil samples were collected at the end of the experiment in October. Two replications per treatment were submitted for the Comprehensive Assessment of Soil Health (CASH) test. All replications were analyzed using the Solvita soil health test methods (WoodsEnd Labs, Maine).

The Douglas Fir trees could not be destructively sampled, thus final data collected in mid-September were tree height, number of buds on the leader, and leader height, based on the method described by Hinesley et al., 2000. No data were collected on newly planted trees within each treatment.

Research results and discussion:

Container Experiments:

Year 1 - 2019 results

No differences were found between treatments on shoot growth (Figure 1). Root biomass weight included the weight of the potting media because it could not be separated. Treatment B30 produced significantly more root biomass than B10. No other differences were found between treatments on root biomass.

No trends were found for ammonium and nitrate leachate concentrations based on treatment for both boxwood and switchgrass plants.

Overall, plant health ratings of container plants in year 1 were either 4 or 5, meaning little to no disease issues.

Figure 1

Pictures of all container boxwood and switchgrass plants were taken on 8/20/2019 to visually compare treatments. No visual differences were seen from these side-by-side pictures.

Boxwood plants - treatment with biochar mixed at 30% by volume. Taken 8/20/19

PourThru data (EC and pH) were collected throughout the season. No differences were found between treatments over the season. 

Example of EC data collected during the 2019 growing season for Boxwood container plants


Year 2 - 2020 results

No significant differences were found between treatments on shoot dry weight, pH, EC, number of stems as determined by the plant health evaluations, and foliar nutrient levels for the overwintered 2019 on-farm switchgrass plants. Differences were found after destructive sampling on rootball weight with the control and 20% mixed biochar treatments having a greater rootball dry weight than the 10% bottom and 30% mixed biochar treatments. 

Similarly, for the overwintered 2019 boxwoods at LIHREC no significant differences were found for rootball dry weight, shoot dry weight, foliar nutrient levels, and pH of the leachate. The 20% and 30% bottom biochar treatments were found to have significantly lower EC values over the growing season compared to the control. 

Regarding the switchgrass plants potted up in 2020, no differences were found between any of the treatments for the parameters measured at either location. However, the irrigation management was found to differ significantly between the LIHREC and on-farm location and impacted nutrient leaching levels. This is an issue that must be investigated further next season.  

Field Experiments:

Lysimeter samples were collected from late July to late October from the Christmas tree and California privet production fields. The low-tension, porous-cup lysimeters functioned well in the loamy soils of the Christmas tree production soils, but not in the sandier soils of the California privet production fields. We believe fewer samples were collected from the privet-field lysimeters because the soil was too free-draining at the 18-inch depth location of the porous cup. In 2020 we plan to install shallow low-tension lysimeters to improve data collection.  Fertilizer practices differed by grower. For the Douglas fir trees, a low rate of slow-release, organic fertilizer (3% N) was applied at a rate of 0.1 oz N per tree three times during the growing season (May, June, and September). For the California privet shrubs, one application of conventional, quick-release fertilizer (16%N) was applied in early July at 500 pounds to the row-acre. Table 1 lists ammonium (NH4) and nitrate (NO3) nitrogen levels detected in field lysimeters located at the Christmas tree farm in Douglas fir production fields. Table 2 lists ammonium (NH4) and nitrate (NO3) nitrogen levels detected in field lysimeters located in the California privet production fields. 

Table 1. Ammonium and nitrate nitrogen levels detected in Douglas fir production fields from July 2019 to October 2019, Long Island, New York.

  Ammonium-N (ppm)
TRT* 23-Jul 8-Aug 13-Aug 14-Aug 22-Aug 23-Aug 29-Aug 13-Sep 2-Oct 4-Oct 23-Oct
5 T/A 15.9     14.9 18.8 17.3 17.2 3.2      
10 T/A     15.5   16.9 21.7 22.7 1.3 1.7 0.5 1.4
15 T/A 18.9 17.0 18.5   15.7 19.5 17.1 0.5   2.1 < 0.1
Control 14.0 17.8 20.4   19.3 20.2 15.4 0.9   0.6 4.7
  Nitrate-N (ppm)
5 T/A 25.8     32.4 35.3 35.9 49.7 32.9      
10 T/A     31.7   34.8 33.9 37.7 43.0 37.4 44.1 49.0
15 T/A 20.4 26.5 23.7   34.5 43.6 50.8 51.3   46.1 57.2
Control 34.1 38.9 34.8   48.7 53.9 53.4 52.9   53.6 75.0

*TRT represents "treatment."

T/A refers to "tons/acre.'

Table 2. Ammonium and nitrate nitrogen levels detected in California privet production fields from July 2019 to October 2019, Long Island, New York.

  Ammonium-N (ppm)
TRT* 23-Jul 8-Aug 29-Aug 13-Sep 4-Oct 23-Oct
5 T/A         3.0 1.3
10 T/A     13.0 0.5 3.6 2.1
15 T/A           2.1
Control 23.5 11.2 22.1 0.8 2.5 2.0
  Nitrate-N (ppm)
5 T/A         42.5 51.8
10 T/A     9.1 2.0 24.1 46.1
15 T/A           30.8
Control 40.5 1.1 8.3 2.6 30.2 34.3

Shoot and root data for both species are currently being summarized. (Update 2020) There were no significant differences found across treatments or control with root and shoot dry weights. 


Year 2 - 2020 Field Results

All plants continued to establish well during the 2020 growing season. There were no observable differences in biotic or abiotic issues. Health evaluation data are still in the process of being summarized at this time. Similarly, soil water extract data collected from lysimeters and soil moisture data collected from TDR probes are in the process of being summarized. Soil nutrient analyses showed significant differences in mean soil sodium (Na) base saturation levels in the Douglas fir trial only with the control differing significantly from the 5, 10, and 15 tons/A treatments (F16, 3 = 4.13, p<0.05). Mean soil sodium base saturation for control plots was 1.08%, with the biochar treatments having sodium base saturation levels at 0.88, 0.93, and 0.88 percent for the 5, 10, and 15 tons/A treatments, respectively. 


Year 3 - 2021 preliminary results

No significant differences were found between treatments on soil health indicators as determined by the CASH test at the conclusion of the study. Soil Labile Amino Nitrogen (SLAN) and CO2 burst respiration level were found to be different at one farm. The biochar 15 T/ac treatment was found to result in greater CO2 respiration than the biochar 10 T/ac treatment, but no other differences were found. The biochar 5 T/ac and control treatments had greater levels of organic soil nitrogen as determined by the SLAN test than the biochar 15 T/ac treatment. No other differences were found. These results suggest no clear pattern of biochars impact on soil properties.

No differences were found between treatments on the number of leader buds and height, or tree height, for the Douglas Fir (Pseudotsuga menziesii) trees. California privet shoot biomass data were still being summarized and analyzed at time of writing this report.

For the container trials, no differences were found on shoot and root weight for the 2020 overwintered switchgrass plants. Treatment differences were found on final root dry weight for the container California privet, Japanese forest grass, and switchgrass planted in 2021. However, no consistent effect of biochar rate and type was observed. Shoot weight was different only between treatments in the Japanese forest grass with the oat hull biochar 50% treatment producing significantly less biomass than other the other treatments.

Data analysis is still on-going and all results and conclusions will be presented in the final project report.

Mina Vescera destructively sampling switchgrass

Image: Mina Vescera collecting the shoots of a switchgrass plant before drying. 

Image: Deborah Aller collecting final leaf samples from a California privet plant. 

Research conclusions:

Conclusions will be presented in the final report.

Participation Summary
4 Farmers participating in research

Education & Outreach Activities and Participation Summary

Educational activities:

30 Consultations
1 Curricula, factsheets or educational tools
4 On-farm demonstrations
3 Published press articles, newsletters
15 Webinars / talks / presentations
1 Workshop field days

Participation Summary:

475 Farmers participated
300 Number of agricultural educator or service providers reached through education and outreach activities
Outreach description:

2019 Activities - year 1

An article providing an overview and explanation of the project was published in our local monthly agricultural extension publication (Ag News). This publication is mailed to approximately 325 growers monthly. The article is entitled "New study will look at biochar impacts on water and nutrient retention in nursery production."
Ag News article April 2019

An overview of the project including a discussion about biochar and soil moisture sensors was given to nursery growers attending Cornell University's annual Plant Science Day at LIHREC in July 2019. 

Mina Vescera speaking to growers about the biochar project at Plant Science Day 2019

Mina Vescera attended the Northeast Specialty Crop Water Symposium in December 2019 at the University of Vermont where she presented an overview of biochar and the field trials associated with this project. Talk titled "Evaluating wood-based biochar in field production of woody ornamentals in Long Island nurseries".

2020 Activities - year 2

An article providing an update on the field portion of this trial was published in February 2020 in Ag News. The article is entitled "Evaluating Biochar in Field Production of Ornamental Woody Plants". Ag News Article February 2020

In March 2020, Deborah Aller gave a presentation on "Soil Science, Water Management & Amendments" for the Long Island Arboricultural Association. She discussed biochar and the ongoing research associated with this project for improving tree and plant health in the landscape. 

In lieu of an in-person field day due to the pandemic a four part biochar webinar series was held in November 2020 (Biochar2020 webinar flyer). Biochar basics, the science behind biochar, ornamental nursery applications of biochar, and landscape applications of biochar were discussed by 12 experts from across the United States. We were able to reach over 600 individuals through these virtual events. All the recordings are available for viewing on the New York Soil Health website (Biochar Webinar Series-recordings NY Soil Health Initiative) or this link:

Also, in November 2020 Deborah Aller gave a (virtual) presentation on the 'Potential of Biochar for Use in Nursery Crop Production' at the ASA-CSSA-SSSA International Annual Meeting.

An article providing an update on the container portion of this trial was published in December 2020 in Ag News. The article is entitled "Project Update! Evaluating Biochar for Use in Container Production". Ag News Article Dec2020

2021 - year 3

In 2021, Deborah Aller discussed biochar and shared the current findings of the study at various meetings and workshops including a University of New Hampshire Extension Plant Production Lunch and Learn Series, Stony Brook University Seminar, and the New York Soil Health Specialist Training Workshop series.

Unfortunately, due to uncertainly around the ongoing pandemic no in-person field day was held in 2021.

Deborah Aller giving a biochar presentation at a NYSH Specialist Training in Fall 2021


Project Outcomes

2 Grants applied for that built upon this project
28 New working collaborations
Success stories:

A nursery/landscape/golf course manager from western Long Island is now aware of biochar and its potential benefits and plans to incorporate it into his managed landscapes in the future.

Five vegetable farmers are interested in using biochar on their farms. Also, a local vineyard is interested in producing biochar from vine trimmings and applying it back to the crop. 

Interest in using biochar on farms continues to increase both on Long Island and beyond. Farmers frequently inquiry about the benefits of biochar and possible use on their own farm. 

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.