Development of a Sustainable Cropping System for Industrial Hemp Production by Limited Resource Farmers

Progress report for LS20-333

Project Type: Research and Education
Funds awarded in 2020: $229,933.00
Projected End Date: 03/31/2023
Grant Recipient: North Carolina A&T State University
Region: Southern
State: North Carolina
Principal Investigator:
Dr. Beatrice Dingha
North Carolina A&T State University
Dr. Arnab Bhowmik
North Carolina A&T State University
Louis Jackai
N. Carolina Agricultural and Technical State University
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Project Information


Industrial hemp (Cannabis sativa (L.)) is one of the oldest cultivated plants in the world grown for fiber, oilseed, and pharmaceuticals. After ≥80 years, hemp has been legalized to be grown again in the U.S; however, knowledge needed to grow hemp is limited. Research must now be initiated to ensure farmers are able to make informed decisions and avoid economic losses. The proposed experiments were developed with input from three studies by the PIs. (1). In a 2019 survey, 85% of organic farmers in NC were interested in growing hemp on their farms. Among them, 93% would grow hemp because there is a market, >84% if it fits into their current rotation, has low insect and disease pressure and diversify their farm. (2). We identified cowpea cultivars highly attractive to pollinators that increased crop yield in a vegetable intercropping system. In addition to supporting pollinator activity, cowpea fixes atmospheric nitrogen. This process can contribute a significant amount of N (>45-175lbs N/ha) to the subsequent crop thus improving soil health. (3). An ongoing soil fertility trial indicates hemp requires approximately 50-100lbs N/ha which is within the range reported for cowpea. With the soaring fertilizer prices alternative sources of soil fertility enhancers are going to be needed by farmers. For example, they can use legume such as cowpea, grown either as an intercrop or in rotation with hemp to provide the required N-level to produce higher yields. Crop rotation and intercropping are important cultural practices in crop production and pest management based on the principle of reducing pests and improving soil health. In the proposed system, pollinators would be attracted to cowpea for its nectar and hemp for pollen thus providing important ecosystem services, a component of productivity and as a forage resource. Pollinators as a whole contribute $24 billion and honey bees $15 billion to the U.S economy. However, its role in agricultural enterprise has recently been compromised by the decreasing bee populations. Since 2006, U.S beekeepers have seen >40% decline in honey bee colonies; according to NC State Beekeepers Association, there was >50% loss in 2018, impacting the state's $84 billion agriculture industry. As a countermeasure, one strategy has been to increase abundance of bee forage resources on farmlands. We propose to achieve this through intercropping and rotation using cowpea highly attractive to pollinators. The primary goal of this project is to develop a sustainable research-based strategy and communicate information on pests, pollinator activity, soil health in a cropping system perspective that will help farmers make informed decisions about hemp production. To attain this goal, we propose four specific objectives: a) identify hempseed cultivars suitable to grow in NC-reduced pests, pollinator-attractive and high yielding; b) evaluate integration of hemp into two cropping systems- crop rotation and intercropping; c) evaluate soil health indicators with respect to biological nutrient cycling and microbial community; (d) assess system profitability from best production practices derived from a-c. Overall, the proposed project will enhance hemp production through management strategies that are sustainable and cost-efficient.

Project Objectives:

Objective 1. Screen 4 industrial hemp seed cultivars to identify cultivars with high yields, reduced pests incidence suitable to grow in North Carolina

Objective 2. Evaluate the effect of integrating five agronomically desirable hemp seed cultivars (from objective 1) in an intercropping system that includes Hemp+Cowpea+Pollinator-Dependent-Crop. The pollinator-dependent-crop may include cucurbits (such as water melon, watermelon or squash) or okra.

Objective 3. Measure biological soil health dynamics with respect to microbial nutrient cycling and microbial communities in each of the two systems described in objectives 2 and 4.

Objective 4. Assess system profitability from best production practices used in objective 2 and evaluate the effect of crop rotation at collaborative farmer-managed farm and at NCAT research plot.


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Materials and methods:

Objective 1. Screen 4 industrial hemp seed cultivars to identify cultivars with high yields, reduced pests incidence suitable to grow in North Carolina.

Experimental plots were established at the NC A&T research farm, Greensboro, NC. Four industrial hemp cultivars (Canda, CFX-2, Joey and Henola) were grown at NC A&T on May 18th, 2021. Each treatment was planted in 10 rows, each 7 m long with 7.5 inches inter-row spacing and replicated 4 times in a Randomized Complete Block Design (RCBD).

Insect sampling: Sampling was focused mainly on pests and pollinators (bees). However, other captured beneficial insects were also recorded. Visual observation of insects: For each treatment, the two 10m rows were observed for 2 minutes each for pollinators and other insects. Observations were conducted weekly for eight weeks and data was recorded on the number of insects. Vacuum sampling: This was conducted using a Ryobi insect vacuum (Bioquip Product). The 10m rows for each hemp treatment was vacuumed for 30 s. Samples were placed in Ziploc bags and stored in a refrigerator and later sorted using a microscope. Evaluation of pollinators using pan trap: Pollinators were sampled within each treatment using pan traps. Traps were made from 16oz. polypropylene deli bowls painted with UV-bright fluorescent blue or yellow paint and unpainted 12oz. white styrofoam bowls. The bowls were individually glued onto a 36” plant prop using adhesive and one of each color bowl were placed between the 2 rows within each cowpea variety during the sampling period. Each bowl was filled with approximately 250mL of soapy water solution (2.5mL of detergent in 1-gallon water). Traps were set out early in the morning (8:00 -10:00 am) and collected after 24 hours weekly. Traps were collected in the order they were placed to ensure that all traps were available to insects for the same amount of time. After 24 hours each pan trap was removed and drained and content removed and placed into vials containing 70% ethanol and stored for later identification.

Unlike other crops, hemp grains easily shatter from the seed head and this can result in yield loss. At about 70% maturity plants were bagged as shown below.
Even though plants were bagged, insect pests such as the Leaf-footed bug and the brown marmorated stink bug were observed feeding on the hemp grain through the bags.

Determination of chlorophyll and sugar content in situ: Chlorophyll readings were taken weekly using a chlorophyll meter (Konica SPAD-502Plus). For each hemp treatment, five random plants were selected and measurements taken from one leaf (highest) of each plant. Individual SPAD readings were averaged for each treatment. Data was collected weekly for five weeks. Similarly, the leaf sugar content was obtained from leaves of five random plants using a hand held refractometer weekly beginning June 16 to July 28 for a total of four weeks.

Evaluation of agronomic performance: Plant height is one of the major indicators of plant growth and development. Plant height is positively correlated with plant grain yield, and plant biomass. At 63 days after planting (DAP), the height of 10 random plants from each treatment was measured and recorded. At maturity, about 95 DAP hemp plants were harvested, sun as well as air-dried. Because of the bulk of the harvest, data for this reporting period was collected from five random plants from each treatment and from each block for a total of 20 plants. The seeds were separated from the leaves and stalks by hand and further separated using a USA standard test sieve (12" Sieve #6 and #8). Data on seed, leaf and stalk weight was collected and recorded.


Objective 2. Conduct on-farm validation of five agronomically most desirable hemp seed cultivars from objective 1. These will be intercropped with either squash, watermelon or okra (crops that require pollination and are commonly grown by small farmers) and cowpea. (Year 2, Farmer’s farm and Research Farm at NCA&T).

Inter cropping is essential to improve or at least maintain soil health, and allow farmers to diversify markets. Industrial hemp is a particularly good crop to include in crop rotations because its deep root system enhances soil structure. Inclusion of pollinator-attractive crops such as cowpea as an intercrop in a farming system will increase pollinators and beneficial arthropod activity, soil (N) health, crop yield and farm profitability.

Hypothesis: Inclusion of appropriate cowpea cultivars in hemp cropping system will increase ecological services by pollinator and beneficial arthropods as well as soil health (N), crop yield and farm profitability.
Expected outputs: Increase in crop yields and reduced need for pesticides.

In year two, field experiments will be conducted at NCAT research farm and at the farms of participating farmers to determine which of the five best hemp cultivars from objective 1 will provide the optimal association in a cropping systems. The intercropping system would comprise hemp-cowpea-one other plant species/crop varieties selected among cucurbits, watermelon or okra. One hemp cultivar per farmer and the crop combinations will depend on individual farmer priorities but each will be encouraged to intercrop cowpea-hemp with one of the previously stated crops (Test plants [Tp]). The on-farm demonstrations will be grown by farmers with the help of the PIs. Treatments will consist of 6 different crop combinations: (i) Hemp-cowpea-Tp; (ii) Hemp-cowpea; (iii) Hemp-Tp (iv) cowpea-monocrop (v) hemp-monocrop (vi)Tp-monocrop. Plots will consist of 6 rows for treatment (i) comprising two rows hemp, two rows cowpea and two rows of [Tp]. There will be 6 rows for treatments ii and iii each consisting of three rows hemp and 3 rows of cowpea/Tp. For the controls (iv to vi), plots will consist of 3 rows for each mono-crop. Each row will be 6-10 meters long as land permits. These will be planted in a RBD with 4 replications. In the growers' farms crops will be planted according to each grower's practice (on beds, on the flat, etc.). Each farm will be used as a replication for analysis of results. . All crops will be grown following conventional recommendations for each crop (Kemble et al., 2018). At the NC A&T Research farm data will be collected as in objective one -include a weekly census of pest and beneficial insects, pollinator count. At maturity seed and biomass harvested will be weighed to determine yield. Land Equivalent Ratio (LER) will be calculated to determine the best companion crop combinations from a systems perspective (Songa et al., 2007). Farmers will participate in the management of their respective farms and, with the help of PIs, evaluate the best hemp cultivars with regard to insect pests and overall yield in an intercrop system. Co-operating farmers will attend the Annual Small Farm Week at NC A&T to increase their understanding of industrial hemp production.


Objective 3. Measure biological soil health dynamics in the above system with respect to microbial nutrient cycling and microbial communities. (Year 2 and 3, Research Farm at NCA&T).

Hypothesis: Hemp grown in rotation with cowpea will improve soil health by increasing the diversity of soil microbes resulting in multifunctional soil microbiome.

Expected outputs: Increased soil microbial diversity in hemp-cowpea crop rotation

From the setup in objectives 2 and 4, soil samples will also be collected (0-15 cm) for soil health indicator analysis before crop establishment and annually in late summer/early fall during the second (intercropping experiment objective 2) and third year (crop rotation objective 4) of the experiments. From each plot, ten random soil samples will be collected using a soil probe and composited. Soils will be analyzed for total carbon (C), N, inorganic N, chemically labile soil C pool (Weil et al., 2003) and macro and micronutrients by ICP-OES in Soils and Analytical Laboratories at NC A&T. Biological soil health indicators like soil respiration, microbial active C and N and soil enzymatic activities will be analyzed according to the Haney soil health test protocols (Ward Laboratories Inc., Kearney, NE).

In order to quantify temporal changes in soil microbial community associated with plant growth and rhizosphere development, soil samples will be collected from all the treatments in the cropping systems experiment. At harvest, soil from around the roots and in the central row spacing of the plots from all parts of the rotations will be examined. This will be done by collecting six intact plants (roots and attached soil) and six soil cores (19 mm diam.) along the centerline between plant rows (depth of 7.5 cm). The soil will be removed from plant roots by shaking into plastic bags. The soil will then be placed on ice and returned to the lab, sieved and homogenized then held at -80 C for DNA extraction. Soil DNA will be amplified using protocol by Caporaso et al., (2012) followed by standardization, pooling, and gel purification in order to be shipped to Genomic Sciences Laboratory (Raleigh, NC). Pair ended (2 × 300 bp) sequencing will be performed using Illumina Miseq (Illumina, Inc., San Diego, CA) in order to survey for bacterial 16S rRNA.  All sequences will be analyzed using DADA2 and/or QIIME 2 pipelines and deposited in the GenBank database.


Objective 4. Assess system profitability from best production practices used in objective 2 on demonstration plots setup and managed exclusively by the participating farmers and at the university farm and evaluate the effect of crop rotation by rotating cowpea plots in previous year (objective 2) with hemp and hemp with cowpea. (Year 3, Farmer’s farm and Research Farm at NCA&T).

Hypothesis: The Best Production Practice will reduce pest management inputs and increase crop yields and farm income and increase the likelihood of adoption.

Expected Outputs: Increase profitability and system sustainability through N-fertilizer enhancement, increase crop yield and increased likelihood of wide-scale adoption.

Crop rotation is essential to improve and maintain soil health and also disrupt pest cycles. The use of hemp on continuous soybean cultivation is one example where it has been shown to increase soybean yield in the subsequent year by 10.8% (Liu et al., 2012). In year 3, at the university farm and farmer's farm, demonstration plots would be set up of the best producing treatment [Hemp-cowpea-Tp] from year 2. The best producing treatment (i) [Hemp-cowpea-Tp] evaluated in objective 2 will be planted as in the previous objective and will be replicated at each farmer’s farm and at the university farm. At the same time plots previously grown with cowpea in objective 2 (previous year) will be rotated with hemp and hemp plots with cowpea. As in objective 2, plots will consist of 6 rows for treatment (i) comprising two rows hemp, two rows cowpea and two rows of [Tp]. There will be 6 rows for treatments ii [Hemp-cowpea] and iii [ Hemp-Tp] each consisting of three rows hemp and 3 rows of cowpea or Tp. For the controls (iv to vi), [mono-crops- Hemp, cowpea and Tp] plots will consist of 3 rows for each mono-crop. Each row will be 6-10 meters long as land permits. Data will be collected on pests and beneficial insects, crop yield as earlier described in objective 1 and 2. From data collected, comparison between hemp treatment (intercrop with cowpea and test plant [Tp]) and control (mono-crop of hemp, cowpea and Tp) will be made to estimate including cost analysis of every activity to enable enterprise analysis and partial budgeting of the individual components. At the end of year 3, the BPP (crop rotation or intercropping will be recommended to farmers for adoption. The demonstration plots at the university farm and cooperating farmer’s farm will be used for field day tour where participating farmers and other growers interested in industrial hemp would be invited for farm tour. Up to 15 growers will be invited through NC A&T Cooperative Extension network. In addition, the co-operating farmers will participate in the Small Farm Field Day at NCA&T.

Research results and discussion:

Objective 1. Screen 4 industrial hemp seed cultivars to identify cultivars with high yields, reduced pests incidence suitable to grow in North Carolina. From visual observations, brown marmorated stink bug (BMSB), leafhopper, sweat bee, Japanese beetle, leaf-footed bug and the tarnish plant bug  were the most abundant insects recorded (Fig. 1).

Data from vacuum sampling shows the false chinch bug, leafhopper and the tarnish plant bug were the most abundant insects (Fig. 2).

Overall, combining data from both visual and vacuum sampling our results show leafhopper, BMSB, tarnish plant bug, false chinch bug, sweat bee, Japanese beetles and the leaf-footed bugs were the most abundant insects (Fig. 3).



















During the first seven weeks of direct visual counts, there was a steady increase in the total number of insects observed followed by a decline in the last week (Fig. 4). This increase can be attributed to the presence of more Japanese beetles and leafhoppers in weeks three and four and more BMSB sweat bees and leaf-footed bugs in weeks six and seven compared to the other pollinators (Fig. 4).






During the first five weeks of vacuum sampling there was a steady increase in the number of insects recorded followed by a decline in week six, this was followed by an exponential increase in week seven (Fig. 5). Leafhopper and the tarnish plant bug accounted for the insect abundance in week three and four while the increase in week six and seven was due to the abundance of the false chinch bug (Fig. 5).





Combining insects recorded from both vacuum sampling and direct visual counts, our results show leafhopper, Japanese beetle and the tarnish plant bug were the most abundant insects recorded in weeks one to four while the BMSB, sweat bees, false chinch bug and the leaf-footed bug were most abundant in weeks 5 to eight (Fig. 6).




Direct visual counts show that among the hemp cultivars, there were differences in the abundance and diversity of insects recorded on the crop weekly and during the eight weeks of visual sampling. Weekly record of insects shows more leafhoppers, Japanese beetles and lady beetles were observed during the early sampling dates (weeks one to four) and more BMSB, leaf-footed and sweat bees were recorded during the later part the sampling period (weeks five to eight), (Figs.7a-10b). The plant tarnish bug was recorded throughout the sampling period and it was more abundant on Henola (Fig. 10b). There were more BMSB, leaf-footed bug, Japanese beetle and sweat bees on Joey>Canda>CFX-2>Henola (Figs. 7b, 8b, 9b and 10b).

Sugar Content (% Brix)


16 June 2021

30 June 2021

14 July 2021

28 July 2021
































Chlorophyll Content (SPAD Units) of four industrial hemp cultivars


15 June  2021

29 June 2021

























Participation Summary
4 Farmers participating in research


Educational approach:

N/A at this time.

Project Outcomes

Project outcomes:

N/A at this time.

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.