Performing Department
Plant and Soil Sciences
Non Technical Summary
As acreage devoted to industrial hemp increases across the US, it is incumbent upon agricultural scientists to understand the impact that incorporation of hemp into management systems will have on rotational crop yield and agroecosystem services such as soil health and function. Further, there is a dramatic paucity of knowledge in general on industrial hemp and its agronomic value. The proposed work will establish a necessary framework for studying industrial hemp, generate knowledge on the sustainability of industrial hemp as a rotation crop, train scientists in hemp agronomy and agroecosystem services, and strengthen collaborative work between the two land-grant institutions in the state of Kentucky. This project will incorporate both hemp for fiber and hemp for grain into conventional crop rotations (corn-wheat-soybean) at two established Kentucky research farm sites. The impact of hemp on grain crop yield, as well as on hemp fiber biomass will be assessed to determine profitability, and identify changes to provisioning services compared to a conventional rotation. Agroecosystem services related to sustainability and soil health and function will be measured, including soil physical, chemical, and biological parameters. Weed pressure and diversity will be measured to determine how the lack of allowable pesticide use on hemp impacts weeds in hemp and subsequent crops
Animal Health Component
0%
Research Effort Categories
Basic
75%
Applied
25%
Developmental
(N/A)
Goals / Objectives
As acreage devoted to industrial hemp increases across the US, it is incumbent upon agricultural scientists to understand the impact that incorporation of hemp into management systems will have on rotational crop yield and agroecosystem services such as soil health and function. Further, there is a dramatic paucity of knowledge in general on industrial hemp and its agronomic value. The proposed work will establish a necessary framework for studying industrial hemp, generate knowledge on the sustainability of industrial hemp as a rotation crop, train scientists in hemp agronomy and agroecosystem services, and strengthen collaborative work between the two land-grant institutions in the state of Kentucky. This project will incorporate both hemp for fiber and hemp for grain into conventional crop rotations (corn-wheat-soybean) at two established Kentucky research farm sites. The impact of hemp on grain crop yield, as well as on hemp fiber biomass will be assessed to determine profitability, and identify changes to provisioning services compared to a conventional rotation. Agroecosystem services related to sustainability and soil health and function will be measured, including soil physical, chemical, and biological parameters. Weed pressure and diversity will be measured to determine how the lack of allowable pesticide use on hemp impacts weeds in hemp and subsequent crops.
Project Methods
To test our hypothesis, that incorporating hemp into traditional Kentucky crop rotations will have a positive effect on agroecosystem regulating and supporting services, such as promoting soil carbon accumulation and reducing soil-to-atmosphere greenhouse gas fluxes, and will not negatively impact provisioning services, such as crop yield of subsequent rotations, we will deploy a crop rotation scheme including fiber and grain hemp at two field sites in Kentucky.Five replicate blocks of the six crop rotation treatments will be planted at each site, in a randomized complete block design. Plots will be 17 ft x 30 ft, and will include 10 ft buffers. All crops will be planted by standard no-till practices to be consistent with how grain and fiber hemp are typically managed in Kentucky rotations. Each crop (corn, soybean, grain hemp, fiber hemp) will be harvested at maturity and/or when field moisture levels support storage. One 5m2 area within each plot will be hand-harvested to determine crop yields and will be reported in dry yield/A. Harvest sample area will be randomly selected avoiding no less than two border rows in the y plane and 1m in the x plane. For fiber hemp plots the stalks will be cut from the defined harvest area and weighed to determine fresh weight. The stalks will be loosely bundled, tagged, and returned to the harvest area for retting. The remaining border area will be cut and left to ret in place. After 3 to 4 weeks of retting, stalks from the defined harvest area will be weighed again to estimate retted stalk yields and then dried in crop dryer to determine dry weight yield. Retted stalks in the border area will be removed to simulate complete harvest. Grain hemp yield will be determined by hand harvesting grain heads in the defined harvest area, drying and threshing with a stationary thresher. Grain heads will be removed from the border areas to simulate a complete grain harvest. Remaining crop residue (leaves, stalks) will be chopped in place and left on the plot similar to crop residue management for corn and soybean. Winter wheat will be established as a cover crop for all treatments post-harvest, and is not used here as a harvested commodity crop. We have chosen to use a cover crop to provide uniformity to treatments, and to be in line with common agricultural practices in Kentucky.Aim 1: Impact of industrial hemp rotation on crop productivity and profitabilityTo test our hypothesis that incorporation of hemp into the common corn-wheat-soybean rotation will not negatively impact the yield of commodity crops, we will measure biomass or grain production of crops in our experimental crop rotation scheme. A profitability model will be set up to assess profitability of all experimental crop rotation schemes. Data will be analyzed using a mixed linear model (Proc Mixed) procedure in the SAS statistical package (SAS Institute, v.9.1., Cary, NC). Yield, biomass, and root production will be analyzed using crop rotation treatment as a fixed effect and block as a random effect. Overall F-tests will be used to assess significant differences between treatments, and when significant, pairwise comparisons using protected LSD will be performed. Normality and homogeneity of variance will be assessed on all measured parameters, with transformation occurring as necessary.Aim 2: Impact of industrial hemp on weed pressure and diversityWe will assess whether incorporation of hemp into traditional Kentucky crop rotations affects weed abundance and diversity in subsequent crops. To do so, we will randomly locate two 0.5m2 quadrats within the interior of each plot and visually estimate cover (to 1%) of all weed species present. Weed species richness per sampling period will be calculated (sum of all weed species encountered in a plot) and is a representation of species diversity.The same Proc Mixed linear models as developed for the yield methods will be utilized here, except in this case a repeated measures time element will be incorporated for relevant parameters (e.g., for weed abundance over the two or more time periods sampled per crop rotation). It is possible that a non-metric multi-dimensional scaling ordination approach might help visualize some of the trends in the data, in which case we will utilize PC-ORD.Aim 3: Impact of industrial hemp on soil health and functioningWe hypothesize that incorporation of hemp into Kentucky crop rotations will have a positive impact on soil health parameters and soil functioning. We will measure a variety of soil chemical, biological, and physical parameters across our experimental design.Soil chemical parameters - Soil pH, extractable cations, total N and soil test P and K will be measured on composite 0-10cm samples taken upon experiment initiation and then at harvest for all subsequent crops for each crop rotation treatment at both sites (total soil samples = 480). We will sample one meter deep soil core from each plot at the initiation and end of the project for quantification of any deeper changes in these parameters. These will be sent to Regulatory Services on the UK campus for routine soil analysis and processed using standard procedures (http://soils.rs.uky.edu/ ).Soil biological parameters - In order to assess differences in microbiota across crop rotations, culture-independent bacterial community analysis will be carried out on rhizosphere samples from each plot at each site during the wheat crop for each year. We also will measure both AMF root colonization rates and soil extraradical hyphal length. We will utilize a 1412 Infrared Photoacoustic Spectroscopy gas analyzer (Innova Air Tech Instruments, Ballerup, Denmark) which is equipped to measure CO2 and N2O simultaneously. Soil organic matter parameters - We will measure several organic matter pools on a sub-sample of the same surface, 0-10cm composite soil samples that will be taken for the soil fertility analyses. We will measure permanganate oxidizeable carbon according to published procedures (Weil, Islam et al., 2003). We will also perform organic matter separations as per (Six, Elliot et al., 2000) and determine total C and macro- and micro-aggregate C (Iqbal, Siegrist et al., 2012). Soil aggregate stability - We will measure aggregate stability on each plot at the beginning of the trial and following the final harvest as an indicator of the cumulative effects of carbon flux on soil structure in the different rotations. Ten soil cores (5 cm diameter) will be collected from the 0-10 cm depth of each plot, gently broken apart by hand and passed through a 10 mm sieve to remove large rocks and roots. Samples will be kept at field moisture and stored at 4° C until wet sieving. Samples will be wet sieved through a series of sieves to obtain four aggregate size fractions: (i) > 2000 µm (large macroaggregates), (ii) 250 to 2000 µm (small macroaggregates), (iii) 53 to 250 µm (microaggregates), and (iv) < 3 µm (silt plus clay-sized particles) (Elliott, 1986).The same statistical approach developed for the previous aims will also be deployed here - linear mixed models including a repeated measures design if/when appropriate and ordinations for multidimensional data, such as the bacterial community analyses. Data resulting from microbial community analysis will be linked to measured soil biological and chemical parameters using MRPP and ordination analysis to identify statistically significant trends relating microbial communities (16S rRNA data) to functional gene data (qPCR data), AMF data, greenhouse gas emission, and soil chemistry as outlined above (see, for example, Law, Fisher, et al., 2016).