Education and On-farm Research to Improve Long-term Sustainability of Hemp in the Northeast

Progress report for LNE21-416

Project Type: Research and Education
Funds awarded in 2021: $204,331.00
Projected End Date: 01/31/2024
Grant Recipients: University of Maine Cooperative Extension; University of Vermont
Region: Northeast
State: Maine
Project Leader:
Dr. John Jemison, Jr.
University of Maine Cooperative Extension
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Project Information

Summary:

Problem and Justification:  With the passage of the 2018 Farm Bill, hemp production was legalized creating the opportunity to grow a new crop with the potential to diversify farm income in the Northeast.  Since hemp was illegal for eight decades in the US, growers have limited locally-based research information to draw from to guide production.  Contrary to popular opinion, hemp is a challenging crop to grow well in our humid climate.  With little growing experience and limited research-based fertility and pest management information, hemp farmers and agricultural service providers need information and training on how to grow this crop sustainably.  Growers frequently talk about their “hemp field” as if they have no intention of rotation, and that hemp has few pests and needs little fertility.  This perception must be changed to produce hemp sustainably.  We need experimental data to demonstrate 1) the benefit of adopting sustainable rotation practices; and 2) effective levels of nitrogen (N) to sustain yield and quality, and not harm the environment.  Growers and manufacturers can then offer sustainable, locally-grown hemp products at profitable price points supporting local farms, improving the regional economy, and diversifying farm revenues.

 

Solution and Approach :  Our goal is to involve 100 northeast industrial hemp growers in an intensive 15-hour training program in the winter of 2022 and 2023 and document producers’ improved understanding of the crop’s: 1) legal requirements; 2) unique biology and therapeutic benefits; 3) complicated pest and fertility management; and 4) harvest and post-harvest handling.  These same growers will continue building their knowledge by being involved with field days, virtual office hours, and on-farm trials. The on-farm trials will build their confidence in developing N fertility regimes and build our overall understanding of hemp nutrient demand.  Of the participating farms, 50 will report improved rotations, reduced production costs, and/or improved hemp yields of 200 lbs per acre on 100 acres.  At the research stations, replicated research trials will be conducted to assess the effect of a one-, two-, or three-year crop rotation on hemp yield and quality.  We will also conduct N response trials to better define optimum N rates and fanleaf chlorophyll (SPAD) values and ratios to guide growers’ fertility programs.  To document grower’s improved capacity to produce hemp resulting from the work of this project, we will assess pre- and post-training learning and action data from beneficiaries.  In year 3, we will assess adoption of improved rotation, changed fertility practices, and improved income resulting from this project.

Performance Target:

Of the 100 farmers attending the 15-hour intensive training program, 80 will document improved confidence in hemp production, 50 will report improved rotations, reduced production costs, and/or improved hemp yields of 200 lbs per acre on 50 acres.

Introduction:

Resinous hemp production is new to most of the Northeast with true legalization initiated with the Farm Bill in 2018.  The industry grew rapidly with many people entering the field with little knowledge of farming or this plant.  With 80 years of prohibition, we have no valid fertility recommendations, and very few solid agronomic principles to advise growers.  We need N response data to guide fertility recommendations, and we need information on how crop rotation will affect insect and disease management.  Through our educational program, we will develop a five module, 15-hour educational program to give growers the basics on hemp production, harvest, processing and marketing.  Data from our research trials are informing our training materials. 

Research

Hypothesis:

The need for crop rotation research comes directly from farmers experiencing significant disease issues and yield depression because of no rotation.  What impact does successive years of hemp production have on yield/quality and pest management? What crop types (legume, grass, etc) in rotation with hemp will result in highest yields and lowest pest pressure? The second research question was driven by farmers who want to know what is the impact of nitrogen (N) on yield and pest management and how can they know the crop has sufficient N.  Can a SPAD chlorophyll quick-test improve N management? 

Materials and methods:

Research Design

Crop rotation is a fundamental practice to improve yields and reduce pest incidence in crop production. Yet, many of our growers have small land holdings and practice no or limited rotation.  Growers need to see how hemp yield and quality, pest pressure, and soil health are impacted by successive years of hemp production. 

 

In this study, we will grow hemp for one, two or three years and monitor yield and quality, as well as changes in weed, disease, and insect pressure each year.  Rotation crops will include sweet corn and fava beans.  Hemp will be grown in a three-treatment replicated complete block field trial in both Vermont and Maine.  Hemp will be produced consecutively for three years for the no-rotation treatment.  For the single year rotation, hemp will be grown in year 1 and year 3 with sweet corn as the rotation crop in year 2.  For the two-year rotation, fava beans will be produced year 1, sweet corn in year 2, and hemp year 3.   Sweet corn and fava bean yields will be assessed.  Each hemp plot will have 15 plants per plot (5 plants per row) planted on 6 ft x 6 ft spacing, and the three plants of the center row will be harvested for yield and cannabinoid content.  Whole plant biomass will be measured in the field, one plant chipped for moisture content, and the other two will be hung to dry. Plants will be separated into stems, leaves, and flowers, weighed, and flowers will be analyzed for cannabinoid content. 

 

Hemp will be assessed for weed, insect, and disease incidence severity biweekly at each location. Particularly, we will assess the level of and potential increase in diseases like white mold, powdery mildew and Septoria leaf spot over time as affected by rotation.  Data collected in year three will be key to assess the effect of rotation as the entire field will be planted to hemp.  Hemp yield, cannabinoid content, weed, disease and insect incidence and severity measurements will be subject to analysis of variance with appropriate mean separation techniques. 

 

Before planting in year one and following harvest in year three, soil samples will be collected from each plot and sent to the Cornell Soil Health Laboratory in Ithaca, NY for standard soil quality analysis. Soils will be assessed for a variety of physical, biological, and chemical soil health indicators. Procedures outlined by the lab (https://soilhealth.cals.cornell.edu/).

 

The second field research project will involve developing a chlorophyll SPAD meter test to assess sufficiency of nitrogen (N) management. Recommended N application rate for hemp is approximately 150 lbs N/ac, most often supplied at planting or through irrigation. This rate needs to be verified with N response trials. Excessive N fertility can lead to environmental damage, possibly make hemp more attractive to pests, and may increase THC content at harvest putting farmers at risk of not meeting standards.  An in-field test could help growers know that they had sufficient N particularly after periods of extended rainfall. 

 

Jemison has published a method using SPAD ratios to assess corn N status (Jemison and Lytle, 1995). In that work, the ratio of ear leaf SPAD measurements in the field compared to a high N treatment had to exceed 0.95 to have sufficient N for adequate yield.  In 2020, Jemison worked with two growers to collect preliminary data to develop a similar test in hemp. The initial testing was done a month after transplanting; SPAD readings were taken on the fan leaf where the plant’s branching changes from opposite to alternate to see if plants fertilized similarly across varieties had different color values. Different cultivars were found to have different SPAD values with some appearing more deeply green than others.  But, when we measured the leaf below or two leaves below and took the ratio of two SPAD readings, those ratios were similar in plants fertilized similarly. Similar trends were found in hemp grown in a hoophouse and sampled 6 weeks after transplanting.  In August, a second procedure was implemented where fan leaves 8 nodes from the top of the plant and 15 nodes from the top were sampled.  Again, cultivar chlorophyll differences were observed and the ratio of the lower leaves to the upper leaves were above 0.95 and similar across varieties.  This work needs to be repeated in replicated plots with varying N rates to determine the optimum time to employ this test with the greatest success.  By having replicated rates of N applied to hemp in two locations and three seasons, we will also be able to assess if N rates have an impact on cannibinoid concentrations as well as pest pressure.

 

The experimental design will be a randomized complete block with four replicates. Treatments will be 0, 50, 100, 150, and 200 lbs of N/ac (applied as ammonium sulfate) and applied to each plot prior to transplanting in early June. Plot size will be three rows with five plants per row.   At transplanting and one month after transplanting, plant height and number of nodes will be recorded.  At the node where plants’ branching changes from opposite to alternate, plant height, and leaf chlorophyll will be measured on six plants per plot.  Six measurements of leaf chlorophyll will be made on the first alternate branch fan leaf and an average taken.  The fan leaves at the last opposite branch will be measured similarly and a ratio of the lower to the upper calculated and recorded.  In August, we will conduct a second intensive chlorophyll test evaluation collecting SPAD readings on fan leaves 8 nodes from the top of the plant and fan leaves 6 nodes below that.  Ratios will be calculated.  Insect and disease ratings will be conducted at each sampling time.

 

In late September, the three inner plants of the middle row of will be harvested and subjected to procedures outlined above for the rotation study.  All data will be statistically analyzed using appropriate methods (analysis of variance and regression), and an optimum N rates will be determined for each year and location based on yield response.

 

On-farm research will assess the variability of total N content of hemp fan leaves on farms throughout the northeast.  Farmers participating in the on-line training will have the opportunity to participate in the N tissue-testing project. Farmers will collect the five most fully mature fan leaves just prior to flowering from 25 plants and submit to the UVM Agriculture and Environmental Testing Laboratory.  The individual farm’s N analysis will be displayed in comparison to the aggregated results from other farms and to the established book values and other reports (Bryson & Mills, 2014 ‘Plant Analysis Handbook IV’; Cookson et al., 2019).  This research will help farmers gauge the adequacy of their fertility program and the data will help us modify the published ranges to be specific to northeastern agriculture.

 

2021 Rotation Trial Research Project - Stillwater Maine and Alburgh Vermont.  

These experiments were conducted at the Borderview Farm in Alburgh, VT (UVM) and the University of Maine Witter Center Rogers Farm (UMRF) in Stillwater, Maine. Agronomic information is provided in Tables 1 and 2.

 

Table 1.  Agronomic Information for Resinous Hemp Weed Control Trials - 2021

Location

Borderview Research Farm – Alburgh VT

University of Maine Rogers Farm (UMRF) Stillwater, ME

Soil Type

Benson rocky silt loam soil    

Lamoine silt loam soil

Geographic coordinates

45.009080, -73.309259

44.9297, -68.6959

Previous Crop

Cereal Rye

Onions

Plot size

20 ft x 25 ft

20 ft x 25 ft

Plant spacing

5 ft x 6 ft

5 ft x 6 ft

Hemp variety

1 month old Elektra

1 month old Elektra

Seed sown

5/12/2021

5/6/2021

Planting Date

June 2, 2021

June 3, 2021- hemp

June 6, 2021 – fava bean

Harvest Dates

September 17, 2021

September 27 and 28,  2021

 

Table 2.  Soil specific information for two experiments

Location

Borderview, Alburgh, VT

Rogers Farm Stillwater, ME

Soil pH

7.3

6.6

Soil Organic Matter Content

5.3

3.4%

Soil Phosphorus

65.4 lbs/ac

6.8 lbs/ac

Soil Potassium

552 lbs/ac

348 lbs/ac.   7.9 % exch.

Soil Calcium

6930 lbs/ac

1530 lbs/ac    67 % exch.

 

Methods - Rotation study experimental design - 2021

The study was designed as a rotation study with three treatments:  continuous resinous hemp, resinous hemp in year 1 and year 3 with sweet corn grown between the hemp crops, or resinous hemp grown only in year 3 with fava bean or string beans grown in year one, followed by sweet corn preceding it. The experimental design was a randomized complete block design with hemp or beans as treatments in 2021.  Plots were 20x25 feet (0.005 ha) with hemp grown on six by five foot spacing.  Fava beans, variety Vroma, were grown in Stillwater while green beans, variety ‘Contender’ were grown in Alburgh.  In Stillwater, beans were sown in four plots.  Beans were hand sown between 1.5 and 2 inches deep, 9 inches apart sown in 10 rows 25 feet long.  We irrigated the field with approximately 1 inch of water following sowing, and we had excellent germination with approximately 30 plants per row. In Alburgh, beans were planted with 4 row cone seeder planted 1-2 inches deep, 8 inches apart in 8 rows 20 feet long. No supplemental irrigation was applied to plots.

 

Soil Preparation and fertilization

The trials were initiated in the spring of 2021 with soil preparation in late May. Beans were fertilized with 70 lbs of N as ammonium sulfate, 50 lbs P205 and 50 lbs K20.  Hemp was supplied with 120 lbs of N also as ammonium sulfate, 50 lbs P2O5 as triple super phosphate and 50 lbs K2O as potassium chloride.

 

Seed Germination

Individual hemp seeds were sown one seed per pot into 3.5-inch plastic containers in a greenhouse on 6 May 2021 in Maine. In Vermont individual seeds were sown one seed per cell in Deep 50 cell plug trays on 12 May 2021. Supplemental lighting was provided during the day, and plants were given 18 hours of light.  Soil was watered to keep the soil surface sufficiently moist to effect germination and two fertilizations were made with a low analysis 2-2-2 liquid fertilizer. Plants were grown in the greenhouse for almost four weeks prior to transplanting in the field.

 

Transplanting methods

At four-weeks after sowing, hemp seedlings (variety Elektra) were hardened off and transplanted on 3-Jun at UMRF and 2-Jun at Alburgh respectively.  Hemp plants were transplanted on a 5 x 6 spacing without black plastic.  The field was laid out and transplant locations were flagged out after the P and K had been applied and disked in.  To effect transplanting, a sharpshooter shovel was used to dig a hole approximately 15 cm deep and 15 cm in diameter.  Plants were removed from the container, and the based was dipped in water to saturate the rooting medium.  Then, the plant was placed in the hole and watered in. 

 

 

 

 

 

Plot Management

Weeds were controlled with a walk-behind Power Ox cultivator equipped with three sweeps was used to kill germinating weeds on a biweekly basis.  Weeds in the beans were hand weeded. The Power Ox was directed both down the plot and across the plot to control the weeds biweekly in June, July and August.  When the plants were too large to cultivate between them, weeds were hand hoed.   

 

Data Collection

Plant height, diameter and node number were collected biweekly.  Key sampling times were one-month after transplanting, at flower initiation and just prior to harvest.  Leaf chlorophyll measurements were taken on fan leaves at the first alternate and last opposite leaves (nodes 6 and 7) in early July, and then the fan leaves four and five nodes from the top of the plant were measured using the SPAD meter, and also those eight and nine nodes from the plant tops at flower initiation.  Ratios of the first alternate to last opposite (July) and 4th/5th and 8th / 9th nodes from the top were assessed in August at flower initiation.  As these ratios were always around 1, we felt that the fertility program was appropriate.

 

Insect and diseases were sampled at flower initiation and just before harvest.  The three harvest plants were examined in each replicate, with leaves and flower buds examined.   We noted severity of damage to leaf and to stem/flower.  As this was the first year of the trial, we did not expect treatment differences.

 

Fava bean development was very good in the first month.  By six weeks after planting chocolate spot (Botrytis fabae) set in and growth was reduced due to this.  Only data collected was harvest, and only one harvest was taken as the botrytis set the plants back.

 

 

Harvest Methods

Fava harvest data was collected on the two center rows.  Pods were pulled from plants, weighed and seeds were shucked from each pod and weighed.  Green been harvest data was collected on the two center rows. Pods were pulled from plants during a three-week peak harvest window and weighed.

 

Hemp harvest required collecting the middle three plants from each plot for yield assessment.  For each plant harvested, the whole plant weight was recorded. The largest of the three plants was cut at the plant base approximately 10 cm above the ground surface with loppers, and the plant was weighed and run through a chipper shredder to determine whole plant dry matter and total N content. The other two plants were harvested the following day, weighed and one plant in Maine and both plants in Vermont were separated into individual branches and stripped of fan its fan leaves.  Flowers were separated from individual branches using an MB1 Munch Machine bucker in Maine and a BuckmasterPro bucker in Vermont. In Vermont bucked flower was then fed through the CenturionPro Gladiator Trimmer. Wet bud weight and unmarketable bud weight were recorded. Stems were also collected and weighed.  Flower dry matter content was assessed by collecting a flower subsample and drying the flower sample overnight in a small dehydrator.  In Maine, samples of the dehydrated flower were submitted for cannabidiol (CBD) and tetrahydrocannabinol (THC) and total cannabinoid content at Nova Analytics in Portland; samples in Vermont were analyzed in house at the E.E. Cummings Crop Testing Laboratory.  The percent moisture at harvest was used to calculate total dry matter and flower dry matter yields. The whole plant total N was analyzed at the respective university labs.

 

Data Analysis

Using JMP 16 from SAS, data were analyzed using analysis of variance and appropriate mean separation techniques to assess treatment differences.  We were simply interested in knowing if there was a significant block effect as this was the first year of the rotation study.  In year three, we will be most interested in knowing if yield and quality are affected by rotation. 

 

2021 - Nitrogen response trial research conducted in Stillwater, Maine and Alburgh, Vermont

These experiments were conducted at the Borderview Farm in Alburgh, VT (UVM) and the University of Maine Witter Center Rogers Farm (UMRF) in Stillwater, Maine. Agronomic information is provided in Tables 1 and 2.

 

Table 1.  Agronomic Information for Resinous Hemp Rotation and Nitrogen Management Trials - 2021

Location

Borderview Research Farm – Alburgh VT

University of Maine Rogers Farm (UMRF) Stillwater, ME

Soil Type

Benson rocky silt loam soil    

Lamoine silt loam soil

Geographic coordinates

45.009080, -73.309259

44.9297, -68.6959

Previous Crop

Corn

Peas oats cover crop

Plot size

15 ft x 25 ft

15 ft x 25 ft

Plant spacing

5 ft x 6 ft

5 ft x 6 ft

Hemp variety

1 month old Elektra

1 month old Elektra

Seed sown

5/12/2021

5/6/2021

Planting Date

June 2, 2021

June 3, 2021

Harvest Dates

September 21,22

October 1, 2, and 4

 

Table 2.  Soil specific information for two experiments

Location

Borderview, Alburgh, VT

Rogers Farm Stillwater, ME

Soil pH

6.5

6.0

Soil Organic Matter Content

4.8%

2.8%

Soil Phosphorus

6.8 lbs/ac

5.9 lbs/ac

Soil Potassium

116 lbs/ac

247 lbs/ac.   4.9 % exch.

Soil Calcium

4970 lbs/ac

316 lbs/ac    50.6.0 % exch.

Soil Magnesium

222 lbs/ac

316 lbs/ac    6.1 % exch.

 

Methods - Soil and experimental preparation

The trials were initiated in the spring of 2021 with soil preparation in late May.  The experimental design was a randomized complete block with five N rates (0-200 lbs/ac) and four replications.   Soil was disked and based on soil test recommendations, phosphorus and potassium were broadcast applied at 50 lbs of P2O5 and K2O/ac at UMRF according to soil test results. The Alburgh site was disked and P and K were broadcast applied at 57 lbs of P2O5 and K2O/ac at Borderview Research Farm

 

Seed Germination

Individual hemp seeds were sown one seed per pot into 3.5-inch plastic containers in a greenhouse on 6 May 2021 in Maine. In Vermont individual seeds were sown one seed per cell in Deep 50 cell plug trays on 12 May 2021. Supplemental lighting was provided during the day, and plants were given 18 hours of light.  Soil was watered to keep the soil surface sufficiently moist to effect germination and two fertilizations were made with a low analysis 2-2-2 liquid fertilizer. Plants were grown in the greenhouse for almost four weeks prior to transplanting in the field.

 

Transplanting methods

At four-weeks after sowing, hemp seedlings (variety Elektra) were hardened off and transplanted on 3-Jun at UMRF and 2-Jun at Alburgh respectively.  Hemp plants were transplanted on a 5 x 6 spacing without black plastic.  The field was laid out and transplant locations were flagged out after the P and K had been applied and disked in.  To effect transplanting, a sharpshooter shovel was used to dig a hole approximately 15 cm deep and 15 cm in diameter.  Plants were removed from the container, and the based was dipped in water to saturate the rooting medium.  Then, the plant was placed in the hole and watered in. 

 

Nitrogen Source and Application Method

Ammonium sulfate (21-0-0-24) was applied to each plot at 0, 50, 100, 150, and 200 lbs N/ac.  Gypsum was applied to balance the S in each treatment.  These applications were applied to the field in two applications, just prior to planting and three weeks later to avoid salt or fertilizer injury. 

 

Weeds were controlled through hand weeding and a walk-behind Power Ox cultivator equipped with three sweeps was used to kill germinating weeds on a biweekly basis at both sites. The Power Ox was directed both down the plot and across the plot to control the weeds biweekly in June, July and August.  When the plants were too large to cultivate between them, weeds were hand hoed.   

 

Figures 1 and 2 above are the N Response and Rotation trials conducted at the University of Maine Rogers Farm in 2021

Data Collection

To assess N management treatment effects, plant height, diameter and node number were collected biweekly from both locations.  Key sampling times that we will report on were one-month after transplanting, at flower initiation and just prior to harvest.  Leaf chlorophyll measurements were taken on fan leaves at the first alternate and last opposite leaves (nodes 6 and 7) in early July, and then the fan leaves four from the top of the plant were measured using the SPAD meter, and also those eight from the plant tops at flower initiation.  Ratios of the first alternate to last opposite (July) and 4thand 8th nodes from the top were assessed in August at flower initiation and correlated with fan leaf total N collected from the most recently mature fan leaf near the top of the plant methods described by Cockson et al., 2019 at flower initiation, analyzed for total N. 

Figure 3.  CBD hemp and fava beans from the rotation trial. 

 

On-Farm Sampling

At flower initiation, we visited eight farms in Maine to sample cannabis plants for fan leaf total N and test the leaf chlorophyll test methods using the methods described above.  On one farm, we sampled plants by variety, but on most, since the soils were managed the same, we collected one fan leaf sample across varieties and took average SPAD values and ratios to plot against fan leaf N.  We used these data to plot 8th:4th node SPAD ratios against fan leaf N using a modified Cate-Nelson statistical approach to see what fan leaf N and what ratio would separate the data to maximize the number of points in the upper right and lower left quadrants (Cate and Nelson, 1971).  We could then use those values to assess N status from the UMRF N response trial.  

Figures 4 and 5.  Using Minolta 501 SPAD meter to assess leaf chlorophyll and SPAD ratios to assess N status.

 

Harvest Methods

Harvest required collecting the middle three plants from each plot for yield assessment.  For each plant harvested, the whole plant weight was recorded. The largest of the three plants was cut at the plant base approximately 10 cm above the ground surface with loppers, and the plant was weighed and run through a chipper shredder to determine whole plant dry matter and total N content. The other two plants were harvested the following day, weighed and one plant in Maine and both plants in Vermont were separated into individual branches and stripped of fan its fan leaves.  Flowers were separated from individual branches using an MB1 Munch Machine bucker in Maine and a BuckmasterPro bucker in Vermont. In Vermont bucked flower was then fed through the CenturionPro Gladiator Trimmer.  Wet bud weight and unmarketable bud weight were recorded. Stems were also collected and weighed.  Flower dry matter content was assessed by collecting a flower subsample and drying the flower sample overnight in a small dehydrator.  In Maine, samples of the dehydrated flower were submitted for cannabidiol (CBD) and tetrahydrocannabinol (THC) and total cannabinoid content at Nova Analytics in Portland; samples in Vermont were analyzed in house at the E.E. Cummings Crop Testing Laboratory.  The percent moisture at harvest was used to calculate total dry matter and flower dry matter yields. The whole plant total N was analyzed at the respective university labs.

 

 

Data Analysis

Using JMP 16 from SAS, data were analyzed using analysis of variance and appropriate mean separation techniques to assess treatment differences.  We tested for N Rate, location, N Rate*location.  We used methods described by Cate and Nelson to determine critical nutrient levels.   

Research results and discussion:

Environmental Conditions

The 2021 growing season was one of marked extremes.  Table 3 is a presentation of average temperatures and average rainfall throughout the growing season. In Maine the very low rainfall in May and June and abnormally warm weather in June affected our timing of planting and overall growth response. Following transplanting, no rain fell on the field for more than 14-days.  We did two emergency irrigations in Maine in the N trial providing each plant with approximately a quart of water by hand from a watering can. and we applied about an inch of irrigation by sprinkler in the rotation study,   

In Vermont, similar seasonal trends were observed with below average rainfall and above average temperatures during plant establishment. Potential challenges as a result of these conditions were mitigated through hand watering at transplant as well as supplemental irrigation during this period. This helped to reduce plant variability and allowed for good stand establishment.

 

Table 3a.  Average monthly temperature and rainfall collected at UMRF

Month

Avg Monthly Temperature (C)

30-year average temperature (C)

Monthly Rainfall (mm)

30-yr average rainfall (mm)

April

7.4

3.1

96

81

May

12.2

12.2

48

84

June

19.3

17.2

25

89

July

18.1

20

162

86

August

20.5

18.3

76

81

September

19.5

14.4

216

96

 

 

Table 3b.  Average monthly temperature and rainfall collected at UVM-Alburgh

Month

Avg Monthly Temperature (C)

30-year average temperature (C)

Monthly Rainfall (mm)

30-yr average rainfall (mm)

April

8.9

7.5

89

78

May

14.7

14.7

17

96

June

21.3

19.7

78

108

July

20.1

22.5

74

103

August

23.3

21.5

58

90

September

17.1

17.0

104

93

 

Rotation Study

Hemp Growth and Development

At one month following transplanting, plant height and total node count were collected.  These plants responded to the site and grew rapidly (Table 4), and average hemp height at one month after planting was 62 cm, a full 50% taller than the average height in the nitrogen response trial.  By flower initiation, the resinous hemp plant growth had almost doubled in height, and by harvest the plants were on average about 180 cm tall. 

1

Figures 1a-1b ... Hemp rotation trial - UMRF 2021. 

 

Background insect and disease levels were very low at both locations.  

 

Harvest:  Yield and Cannabinoid Content

In Maine the yield of the Elektra variety in this field was very large.  This is likely because the soil was better than in the N trial.  Plants resembled balls as they were as wider or wider than they were tall. Timely rains pushed flower production, and by harvest these plants averaged almost 20 lbs total plant biomass per plant and the flower production was large at approximately 6.3 lbs per plant.  We also found that the flower CBD and THC production averaged about 122 and 5.5 mg/g. 

 

Loc

Height (cm)

Plant yield

Dry Matter Yield

Flower Yield

Plant Total CBD

Total CBD Flower

Total THC Flower

UMRF

1 mo

Flower

harvest

(lbs)

(mg/g)

2-year

60

114

171

18.95

4.7

6.6

16.4

138

6.4

3-year

65.6

123

191

20.3

5.2

5.9

17.3

107

4.7

p<0.05

NS

NS

*

NS

NS

NS

NS

*

NS

 

 

 

 

 

 

 

 

 

 

UVMA

 

 

 

 

 

 

 

 

 

2-year

***

***

155

16.9

5.61

5.68

 

 

 

3-year

***

***

160

16.1

5.27

5.39

 

 

 

p<0.05

 

 

NS

NS

NS

NS

 

 

 

 

Fava Bean Yield

Fava bean yield was limited due to the botrytis disease setting back plants.  This is Botrytis fava and this is a different botrytis than that which affects hemp.  Yield averaged 1220 lbs of biomass per acre with a seed yield of 580 lbs/ac.

 

String Bean Yield

Across the peak three-week harvest window, string bean plot yields averaged 3698 lbs of biomass per acre.

 

 

Nitrogen Rate Response Trial

Early Growth and Development - Resinous hemp response to N.

At one month following transplanting, plant height, diameter and total node count were collected and the area calculated for each N rate. As well, a Minolta SPAD meter was used to measure leaf chlorophyll on the last opposite leaf and first alternate leaf in each N rate.  The values and the ratios were analyzed and the upper most fan leaf was collected only at UVM in the first set of analyses (Table 4.) There was almost always a significant location effect because there was so little plant available water that the plants did not grow well compared to the Alburgh location.  Thus, the height, node count, SPAD values were all significantly higher in Alburgh, but the effect of N rate was similar across sites.  The only exception was the SPAD ratio value; it was neither affected by N rate or location.  It does not appear that the plant at this early stage will express N deficiency adequately enough for the ratio concept to separate N deficiency and an adequate supply. 

 

Table 4.  Plant growth measures and fan leaf SPAD values at last opposite, first alternate, and the ratio to assess response to fertilizer N sampled in early July 2021.

N Rate

Height (cm)

Node #

Last opposite

First alternate

Ratio FA:LO

Fan Leaf Total

N

0

63

12.6

54.9

56.4

0.97

5.0

50

62.6

12.7

56.2

56.4

0.99

5.0

100

58.1

12.4

56.4

58.5

0.96

4.9

150

63.7

12.8

58.5

59.5

0.98

4.9

200

61.4

12.5

56.6

70.1

0.90

5.0

(p<0.05)

NS

NS

0.1

NS

NS

NS

Location

 

 

 

 

 

 

UMRF

38.3

8.2

50.6

53.8

0.94

***

UVM-Alburgh

84.7

17

62.4

66.6

0.98

4.9

(p<0.05)

***

***

***

**

NS

---

 

 

Flower Initiation – growth and development

By flower initiation, the resinous hemp plant growth had doubled in height (Table 5). 

Table 5.  Plant growth measures and fan leaf SPAD values at 4th node and 8th node from the top of the plant, and the ratio to assess response to fertilizer N sampled in early August 2021.

N Rate

Height (cm)

Node #

4TH node SPAD

8th node SPAD

Ratio

8th to 4th node

Fan Leaf Total N

(mg/g)

0

119

17.1

57.3b

57.7

1.01

35.2

50

119

17.7

58.1b

58.7

1.01

37.7

100

115

15.6

58.6ab

58.6

1.00

37.8

150

117

17.2

59.8ab

56.4

0.94

38.8

200

116

16.6

60.1a

57.9

0.96

34.9

(p<0.05)

NS

NS

*

NS

NS

NS

Location

 

 

 

 

 

 

UMRF

81

13.6

50.6

53.8

0.94

30.8

UVM-Alburgh

154

20.1

63.8

65.1

1.02

42.9

(p<0.05)

***

***

***

***

***

***

 

The growth rates were consistent by treatment.  Although the 100 and 200 lb N rates continued to be slightly smaller, more poorly developed in terms of nodes, these differences were not significant indicating not much of a response of the Elektra cultivar to N by flower initiation (Table 5).

 

Using a specific fan leaf value to assess N status was moderately successful using a Cate-Nelson statistical separation procedure (Cate and Nelson, 1971) (Figure 1a).  With this statistical test, one should ideally use established parameters to separate those N treatments supplying sufficient N from those not supplying enough N.  Given how most plants rob N from the lower part of the plant and mobilize it to the growing points, one would think the 8th node from the top would be a better measure of N status than the 4th node.  Using the 3.5% total N value and 55 SPAD units for the fan leaf on the 8th node from the top of the plant, we can separate into the lower left and upper right quadrants 79% of the time (Figure 1a).  Using one variety and two locations of data, one should expect a higher percentage separation.  When the data were separated by color to their respective locations, almost all of the points in the upper right quadrant were from UVM where more adequate early season soil moisture likely helped the CBD hemp utilize the available nutrients; there was little evidence of deficiency even in the 0-N rate.   

 

Figure 1a – use of 8th node fan leaf SPAD value to predict plant N status

Surprisingly the 4th node SPAD value did a better job to separate sites (Figure 1b). Using 57.5 SPAD units and 3.5 % N on the 4th node from the top of the plant, 86% of the values fell in the appropriate quadrants. If we use 4% for the fan leaf N cutoff (Red line on graph), that success rate increases to 98% effectiveness.  But again, all the points in the upper right quadrant are from the Alburgh location and the remainder are from the Stillwater location.  So, despite the positive separation percentages, one would rather see points from both locations spread across the graph.

Figure 1b – use of 4th node fan leaf SPAD value to predict plant N status

Lastly, the ratio of the 8th to 4th node fan leaf SPAD was not well correlated to fan leaf total N.  Using a Cate-Nelson analysis setting the cut off at the 3.5% Total N value reported by Cockson, 2019 as the critical level, and 0.95 as the SPAD ratio reported by Jemison, 1995, only 75% of the points fell in the appropriate lower left and upper right quadrants, which shows some potential, but again since the UVM points were almost all in one quadrant makes this analysis less encouraging.  Using a 4% cutoff value did not improve the relationship. It will be most useful to see how this relationship works with another year of data. 

Figure 1c.  Relationship of the most fully mature fan leaf Total N to the ratio of the 8th and 4th node fan leaf SPAD values. 

 

On-farm Plant Sampling and Analysis

 

On most of the on-farm sampling done across the 8 sites in Maine, we found a range of N rates used and a range in level of weed management.  Consequently, the N levels in the fully most mature fan leaf and ratios found were quite different from what we found at the research station experiments. 

If we used the average value of the 11 varieties at the Edwards farm as one farm and add the other farms visited and sampled in Maine, the farm averaged 8th node to 4th node SPAD ratios of the on-farm sites plotted against most fully mature fan leaf N sampled across varieties led to a statistically significant relationship (Figure 2a).  

Figure 2a.  Relationship of 8th to 4th node SPAD values to fan leaf total N.

If a Cate-Nelson graph is produced for these same data (Figure 2d), the best separation is found with a fan leaf total N at 3.5% and an 8th to 4th leaf SPAD ratio at 0.9.  More data are needed as there are very few data between the 3.15% total N that we used at the Schoppee farm and 3.5% which could also separate the data as effectively.  So, we will repeat this work on farms across both Maine and Vermont farms next season to assess these levels.

Figure 2b – Ratio of the first alternate to last opposite fan leaf SPAD values as affected by weed management – July 2021.

So, it appears that the ratio of the 8th to the 4th node fan leaf SPAD ratio value works well across farm sites and soil types better than it does within a specific farm.  This will have to be further explored next year.

 

Harvest:  Yield and Cannabinoid Content

Due to timely rains in both August and September, plant growth continued to increase.  Between flower initiation and harvest, plant growth and area doubled again (Table 6a).

Table 6.  Plant growth measures and fan leaf SPAD values at 4th node and 8th node from the top of the plant, and the ratio to assess response to fertilizer N in early October, 2021.

N Rate

Height (cm)

Dia

(cm)

Area

(m2)

Plant Dry Matter

Yield

(kg/plt)

Flower dry matter yield

(g/plt)

Total

CBD flower conc.

(mg/g)

Total

CBD flower yield.

(g/plt)

Total

THC conc.

(mg/g)

Whole

Plant

Total

N

(mg/g)

0

151

157

2.42

1.47

486

159

50.9

6.4

25.7ab

50

145

149

2.19

1.58

544

130

46.2

5.3

23.7a

100

153

157

2.47

1.57

493

133

45.2

5.1

25.3ab

150

146

157

2.3

1.7

513

137

54.7

5.2

28.5b

200

150

155

2.42

1.62

461

131

33.4

4.9

27.5b

p(<0.05)

NS

NS

NS

NS

NS

NS

NS

NS

0.05

Location

 

 

 

 

 

 

 

 

 

UMRF

132

145

1.94

0.958

310

138

46

5.4

25.88

UVM-Alburgh

166

165

2.78

2.22

689

***

***

***

26.4

p(<0.05)

NS

***

***

***

***

NS

NS

NS

NS

 

Too much N applied to CBD hemp has been reported to lead to reduced flower production.  While we found no significant differences in flower dry matter yield, the highest apparent yield was found with 50 lbs N/ac. The flower was yield from the 200 lb N rate application appeared to produce the lowest flower production which would support the reports to not over-apply N to CBD hemp.  There was no difference in total CBD or Total THC flower concentration with the UMRF site yielding on average about 46 and 5.4 mg/g at the UMRF.  The plant cannabinoid concentrations are still to be performed in Vermont.

 

Whole Plant Total N at Harvest

 

Although the UMRF site had increasing Total N at harvest, the UVM location had a more varied final total N at harvest leading to overall no effect of added N on total N content for 2021. 

Figure 3.  Whole plant total N at harvest by nitrogen rate. 

 

 

 

 

Research conclusions:

Short-term Conclusions

The project team learned a tremendous amount this year with respect to resinous hemp production.  We at UM are committed to getting plants out of the greenhouse with less variability in size.  While our soil preparation, fertilizer application, and weed management was consistent between plots, the plant size variability significantly influenced our yield and quality.   

This plant does not readily respond to N like other agronomic crops.  Plant size, yield, or flower yield does not seem, based on one years data, seem to be influenced much by N.  It also does not seem to affect cannabinoid levels.  So this is useful and this will all be incorporated into our educational program conducted this spring. 

Participation Summary
8 Farmers participating in research

Education

Educational approach:

Our key educational effort for the grant, the on-line farmer class, is currently under development.  We are actively building the on-line class modules as of January 2022.  We intend to hold the course starting in 10 weeks.  We expect to have an excellent on-line program for farmers. 

In terms of other educational efforts in 2021, we held one hemp field day at the Rogers' Farm in Stillwater Maine.  We had 12 growers attend, two attended from the hemp program at the Department of Agriculture Conservation and Forestry, five certified crop advisors, and 4 educators.  They witnessed rolling and crimping winter rye as a weed management strategy, we showed them the rotation study, and the nitrogen study.   At the time of the field day - held 7/8/2021, the CBD hemp plants had been in the ground about 5 weeks, and we demonstrated the tools that we used to assess N status.  

In early August, Jemison visited eight farms to collect fan leaves and evaluate the N test which we will report on in a different section.  But, Jemison was able to discuss hemp with growers, promote the educational training for the spring, and address any questions they had on a one-to-one basis.  

 

In Vermont, Dr. Darby and John Bruce conducted a field day an 43 people attended.  They were able to see the nitrogen and rotation trials along with the other trials that they are conducting.  

Milestones

Milestone #1 (click to expand/collapse)
What beneficiaries do and learn:

Recruitment of hemp farmers to participate in the intensive 15 hours hemp-training program will occur through state hemp programs, current networks, and university websites reaching a pool of 1500 stakeholders. Fall 2021 and 2022.

Proposed number of farmer beneficiaries who will participate:
1500
Proposed number of agriculture service provider beneficiaries who will participate:
5
Proposed Completion Date:
October 31, 2022
Status:
In Progress
Accomplishments:

I have contacted the state hemp coordinators in New England, PA and NY for lists of names and emails of licensed growers from 2019, 2020, and 2021.  I will recruit participants a month before the start of the course.  

Milestone #2 (click to expand/collapse)
What beneficiaries do and learn:

125 farmer participants will enroll and agree to complete the entire educational program including online hemp course, field days, and verification of performance target. Enrolled participants will complete a survey to document baseline knowledge. Fall 2021 and 2022.

Proposed number of farmer beneficiaries who will participate:
125
Proposed number of agriculture service provider beneficiaries who will participate:
5
Proposed Completion Date:
October 31, 2022
Status:
In Progress
Accomplishments:

We are in the process of putting the course together.   The course will begin in March.  

Milestone #3 (click to expand/collapse)
What beneficiaries do and learn:

100 hemp farmers will complete the online training course that will allow them to learn about hemp production, regulations, harvest, post-harvest handling, and market options. A minimum of 90% will complete a post course survey and document improved knowledge in the subject areas covered. March 2022 and 2023.

Proposed number of farmer beneficiaries who will participate:
100
Proposed number of agriculture service provider beneficiaries who will participate:
5
Proposed Completion Date:
March 31, 2023
Status:
In Progress
Accomplishments:

We are in the process of putting the course together.   The course will begin in March.  

Milestone #4 (click to expand/collapse)
What beneficiaries do and learn:

100 hemp farmers that complete the course will receive hemp production recordkeeping booklets and be able to participate in virtual office hours to receive one-on-one technical assistance and further develop hemp production skills. 2022 and 2023

Proposed number of farmer beneficiaries who will participate:
100
Proposed Completion Date:
May 31, 2023
Status:
In Progress
Accomplishments:

We are in the process of putting the course together.   The course will begin in March.  

Milestone #5 (click to expand/collapse)
What beneficiaries do and learn:

75 of the hemp farmers that complete the course will participate in on-farm research to verify nutrient concentration ranges of hemp in the northeast and learn to fine-tune their fertility programs. July 2022 and 2023.

Proposed number of farmer beneficiaries who will participate:
75
Proposed Completion Date:
July 31, 2023
Status:
In Progress
Accomplishments:

I offered to visit farms of hemp growers in 2021 and sample their crops for N status if they agreed to participate in the course.  I visited 8 growers in Maine.  

Milestone #6 (click to expand/collapse)
What beneficiaries do and learn:

250 hemp farmers and service providers attend field days and learn about best management practices (rotations, IPM, nutrient management) that will help improve crop productivity. August 2021, 2022, and 2023.

Proposed number of farmer beneficiaries who will participate:
250
Proposed number of agriculture service provider beneficiaries who will participate:
10
Actual number of agriculture service provider beneficiaries who participated:
6
Proposed Completion Date:
August 31, 2023
Status:
In Progress
Accomplishments:

We had 67  people attend the two field day presentations held in Maine and Vermont in 2021.  

Milestone #7 (click to expand/collapse)
What beneficiaries do and learn:

100 farmer participants in the hemp training program will complete the final survey to verify performance target. December 2023.

Proposed number of farmer beneficiaries who will participate:
100
Proposed number of agriculture service provider beneficiaries who will participate:
5
Proposed Completion Date:
December 29, 2023
Status:
In Progress

Performance Target Outcomes

Target #1

Target: number of farmers:
50
Target: change/adoption:

Of the 100 farmers attending our intensive hemp training, 50 will improve crop management skills including crop rotation, improved nitrogen management, and reduced crop loss due to improved pest management.

Target: amount of production affected:

50 acres of CBD hemp production

Target: quantified benefit(s):

The farmers will see improved hemp yield of 200 lbs per acre on 50 acres

Participants

No participants
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.