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.
Objective 1. Screen 10 to 15 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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Objective 1. Screen 10-15 industrial hemp seed cultivars to identify cultivars suitable for planting in North Carolina. Information will be collected on germination, flowering time/set, height, biomass, pest and beneficial insects (predators and pollinators), crop yield, oil and protein content of seeds. (Year 1, Research Farm, NCA&T).
Industrial hemp is a summer annual plant, strongly photosensitive (flowers according to day length; not physiological maturity) with the onset of flowering triggered by shorter days (Consentino et al., 2012). Since most varieties available to U.S growers were developed in Europe or Canada at or above 45 degrees latitude, it is likely that the relatively shorter days found in the U.S will shorten the vegetative period for hemp and limit yields (Clarke and Merlin, 2016). The growth described for varieties at higher latitudes may not reflect growth under North Carolina conditions. Also, there are very few peer-reviewed articles on the effect of pests on industrial hemp although McPartland et al., (2000) describe a wide variety of harmful insects and pathogens potentially found on hemp. No record exists of pests of hemp in NC. Thus there is a clear need to document pests and beneficial insects such as predators and pollinators in industrial hemp in order to begin developing comprehensive pest management programs. In this objective, all four cooperating farmers will make two visits to the experimental plots at the NCA&T university farm (experimental plots) to see the setup and progress of the project and ask questions and, along with the project scientists, make a choice on the best seed cultivars with low pest damage, high pollinator activity and high seed yield/production.
Hypothesis: Hemp cultivars that are adaptable to NC and possess good levels of resistance to major pests and high seed yield can be identified.
Expected outputs: Identification of cultivars with superior attributes for pest incidence and high seed yield for use in objective #2.
Replicated field evaluations will be conducted in Year 1 to assess insect pest incidence and severity and seed yield. In year one, 10-15 hemp seed/grain cultivars will be planted at NCA&T University research farm on raised beds, 2-row plots 10m long, in a RCBD with four replications. No insecticides or fungicides will be applied. Each variety will be evaluated for THC levels to meet the regulatory threshold (0.3%).
(i) Insect sampling to evaluate pest abundance/diversity: Weekly sampling will be conducted to collect a wide variety of arthropod species and functional groups using multiple collection approaches. To monitor for sessile and stationary herbivores and predators, and capture direct pollination efforts, we will conduct two-minute visual census surveys. For more biodiversity, vacuum sampling will be done and pan traps used for pollinators (Dingha and Jackai, 2019) these will supplement the weekly direct counts. Small actively flying insects (predators, parasitoids and other beneficial insects) will be sampled using sticky cards during the seedling phase of the crop. We will monitor ground dwelling insects using pitfall traps. The combined collection protocols will increase our understanding of the functional and numerical profiles of arthropod communities in hemp, something currently lacking in our understanding of hemp-arthropod interactions. Arthropod diversity will be assessed using the Shannon Weaver Diversity Index (H´). Arthropod community composition (both species and functional groups, i.e., herbivore, predator, parasitoid and pollinator) will be determined. Vacuum samples will be taken on separate days to avoid creating population artifacts due to the movement of insects when disturbed. If needed, plants will be scored for phytophagous mites and leaf miner infestation/damage if detected using a 1-5 scale (1= none; 2= 1-25% lower leaves infested and early browning; 3= 26-50% leaves infested and discolored; 4= 51-75; intense discoloration/browning, most of the lower leaves and some younger leaves infested; 5= severe browning/senescence, >75% leaves discolored and with a network of mines/webbing). These are all standard sampling procedures adapted to suit different insects and situations. All measurements will be made on a randomly selected 5-meter row portion of each cultivar. These measurements will provide an initial indications of the existence of field pest resistance in the industrial hemp varieties and to what pest. Pest damage will be assessed and recorded. At maturity, crop will be harvested and data recorded on seed and biomass weight. The average seed weight will be determined by weighing a sample of 500 seeds from each plot (Vera et al., 2006). Data will also be collected on germination rate, flowering time/set and plant height. Seeds will be analyzed for oil and protein content and THC levels will be measured by GC FID at harvest time. Samples of whole seeds would be ground and defatted by extracting with hexane. Protein would be extracted from defatted flours using a Plant Total Protein Extraction Kit (Sigma-Aldrich, St. Louis, USA). The Pierce Bicinchoninic Acid Protein Assay Kit (Thermo-Scientific, Waltham, MA) will be used to determine total protein concentration following manufacturer’s protocol.
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. https://www.bookstore.ksre.ksu.edu/pubs/MF966.pdf . 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.
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