Progress report for GNE24-320
Project Information
Cover cropping is an agricultural practice that benefits soil chemical, physical, and biological properties. Cover crops have the added potential to be harvested as high-quality livestock forage. Crops, such as Cereal Rye and Australian Winter Pea are commonly utilized for forage in Midwestern states and can be used to displace corn and other grains imported to balance rations. The loss of cover crop residue when fed as forage, while economically beneficial for farmers, could potentially have effects on silage corn yield, soil microbial biomass and community structure, and soil health in general. The objective of this research is to evaluate cereal rye and winter pea for forage quality at two different growth stages, while also evaluating the effects of residue management on subsequent crop growth and soil chemical and biological properties. A split plot design with 4 replications will be conducted with main plot as 3 cover crop treatments and subplot as three residue management treatments. The three species treatments are monocultures of cereal rye, winter pea, and no cover crop. The three residue management treatments are cover crop harvested at boot stage, cover crop harvested at anthesis, and residue terminated and retained in the field. The result of this research will provide new knowledge on the best time to harvest cover crop for forage based on nutritional factors and the impact of retaining residue in their fields compared to the removal of residue at two different growth stages on silage corn yields and soil bacterial biomass and community structure.
- Evaluate the performance of different cover crop species and residue management on ground cover, cover crop biomass, weed suppression, and link these impacts on the subsequent crop biomass.
- Evaluate different cover crop species for dairy forage quality for two different growth stages, boot stage and anthesis. Investigate the impact of cover crop species and residue management on soil chemical properties and soil microbial diversity, community composition, and abundance, and link these impacts on nutrient cycling, nutrient uptake by corn, and corn silage yield.
The purpose of this project is to investigate the effects of two cover crop species, cereal rye and Australian winter pea, and their residue management on forage quality, subsequent crop biomass, and soil microorganisms. This project focus is driven by the Northeast SARE outcome statement. The goal of this project is to provide Connecticut and North-East dairy farmers with sustainable and economically viable methods to manage cover crops in their silage corn monocultural rotational agroecosystems. Research has shown that cover cropping is a sustainable agricultural practice that provides benefits to the soil-plant-atmosphere systems, such as the prevention of soil erosion, reduced nutrient leaching, weed suppression, carbon sequestration, and improved soil chemical, physical, and biological health (Kim et al., 2020; Koudahe et al., 2022; Wooliver and Jagadamma, 2023). Different species of cover crops affect these soil properties in various degrees (Fageria et al., 2007). In addition to cover crop benefits on soil health, cover crops can generate a second source of highly digestible forage for livestock. Harvesting cover crops can be economically profitable for farmers and reduce the amount of additional purchased feed (Sadeghpour et al., 2021).
Cereal cover crops are known for their ability to reduce nutrient leaching and erosion through the capture of residual nutrients, as well as their ability to suppress weeds (Fageria et al., 2007). Cereal rye produces large biomass, is a nitrogen (N) scavenger, and an excellent weed control cover crop. Cereal rye is a favorable cover crop for forage due to its earlier maturity when compared to other popular grass cover crops like triticale or wheat (Landry et al., 2019).
Legume cover crops are used for their benefits in supplying N to the subsequent crop due to their symbiosis with nitrogen-fixing microorganisms. This can reduce the amount of N fertilizer application that is needed (Fageria et al., 2007). Legumes that produce more biomass, will fix more N (Koudahe et al., 2022). Legumes such as clovers, peas, and hairy vetch are excellent N fixating plants, although peas produce larger biomass than clovers and are not as invasive as hairy vetch. Exploration of Australian winter peas as a cover crop in Connecticut is due to their forage potential and protein content (Han et al., 2013).
Connecticut dairy farmers want to utilize a cover crop that has high forage potential to supplement silage corn and hay feed yields. Winter pea and cereal rye can supplement traditional livestock feeds (Vann, 2024). This is important because cropland in Connecticut for dairy farming is on a decline. Double cropping with a high-quality forage crop could be used to supplement the declining land availability (Department of Economic and Community Development & Department of Ag., 2009). This project will focus on cover crop harvest times at boot stage and anthesis to determine which growth stage produces the best quality forage in Connecticut.
Soil microorganisms are essential for several nutrient cycling processes, the turnover of organic matter, and soil health. Cover crops can be used to promote beneficial soil microorganisms (Finney et al., 2017; Gao et al., 2022). Plant communities are a primary source of carbon for microbial growth, therefore crop management is key for the promotion of microbial community growth and activity. The usage of cover cropping has been shown to positively impact microbial biomass since cover crop residue provides carbon to microbial communities during times where fields might otherwise be fallow (Adetunji, 2020; Finney et al., 2017). The removal of cover crop residue for forage may have implications on the degree of ecosystem services that they offer (Sadeghpour et al., 2021). Another focus of this study will be to investigate the effects of residue removal compared to residue retained on soil microbial biomass and community structure and its impact on nutrient cycling, and subsequent crop yields in Connecticut.
The results of this project will inform Connecticut dairy farmers of the best time to harvest cover crop for forage based on nutritional factors, the impact of retaining residue in their fields compared to the removal of residue at two different growth stages on silage corn yields and soil bacterial biomass and community structure.
Research
- Evaluate the performance of different cover crop species and residue management on ground cover, cover crop biomass, weed suppression, and link these impacts on the subsequent crop biomass.
This research experiment will take place on the University of Connecticut Research Farm located in Storrs, CT in a no-till field. The experimental design is a split plot strip trial design with four replications. The main plot is three cover crop species treatments and the subplot is three residue management treatments. The three cover crop treatments are Cereal Rye (Danko Variety) seeded at 117 kg ha-1, Australian Winter Pea seeded at 100 kg ha-1, and no cover crop. The cover crop will be planted using a no-till drill at a planting date of September 29th or earlier, depending on silage corn harvest date. Fall 2024 cover crop treatments were seeded on October 2nd, 2024. Nora Doonan and Dr. Haiying Tao are conducting planting date and seeding rate experiments using cereal rye and winter pea to inform of the best planting date and seeding rate for these cover crops in CT. One year data collection on cereal rye suggests that a planting date of September 29 and October 15 are more optimal than a later planting date of October 31 and a seeding rate of 56 kg hectare-1 or greater is more optimal for biomass production and weed suppression. The three residue management treatments are cover crop residue retained in field, residue harvested at boot stage, and residue harvested at anthesis. Each experimental unit is 3.35 by 25.3 meters. The cover crop treatment where residue is retained in the field will be terminated at anthesis, which is a typical practice in CT, using a roller crimper or herbicide. Residue treatments that will be harvested at boot stage or anthesis will be removed by a cutting machine that will cut stalks four inches from the soil surface. Corn will be planted using a two-row no-till drill seeder two weeks after CC termination. Fertility management for corn will follow the UConn recommendations. Cover crop will be fertilized if there are deficiencies.
Fall cover crop plant population counts will be conducted two to three weeks after the cover crop planting date. One representative 0.25 meter-squared quadrat will randomly be placed in each experimental unit. The quadrats will be aligned to include three rows of cover crop seedlings. The number of individual plants growing in the quadrat will be counted and two corners of the quadrat will be marked with plastic marking flags so that these quadrats may be utilized in the spring. Fall 2024 plant population counts were conducted on October 21st, 2024. Ground cover estimates will be made at spring green-up in late-March to early-April at Zadoks 22-29/Feekes 3 growth stage using the previously established 0.25 meter-squared quadrats. PVC piping will be cut to size and aligned with the two flagged corners to guarantee each photo is cropped at the same dimensions. A mini white board indicating the plot number will be placed next to the quadrat. Using a digital camera, a picture of the 0.25 meter-squared quadrat will be taken including the whiteboard. The camera will be held horizontal to the ground above the quadrat. In addition, the top three dominant weed species in the quadrat will be recorded. Images will be processed for fractional green canopy cover and weed pressure. Spring destruction biomass harvest will be conducted at cover crop anthesis, which is estimated to occur in mid-May at Zadocks 65/Feekes 10.5.2. The permanent 0.25 meter-squared quadrates will be used and all aboveground biomass in the quadrat will be clipped, both cover crop and existing weeds, and placed into a labeled paper bag. The predominant weed species will be noted (top three weed species, ranked) and the weeds will be separated from the cover crop. The cover crop and weed biomass will be dried and weighed. The weight will be recorded.
Corn planting will be conducted after cover crop termination. A short season corn, 88 day relative maturity, will be planted using a two-row no-till planter with row spacing of 30 inches. The corn will be planted at a seeding rate of 79,040 seeds ha-1. Corn biomass sampling will be conducted at anthesis. Ten representative plants will be sampled from each plot and samples will be oven dried at 62°C for 72 hours, weighed, and ground (Pavinato et al., 2017). Corn harvest will be conducted using a six-row header when the corn is at optimum stage for harvesting, determined by the milkline of a kernel. The optimal milkline is 1/4-3/4 of the kernel, indicating that the corn is at good moisture level (Israelsen et al., 2009). Data will be analyzed using appropriate procedures (such as ANOVA and regression) in SAS and R software.
- Evaluate different cover crop species for dairy forage quality for two different growth stages, boot stage and anthesis.
A destructive biomass harvest will be conducted at boot stage and anthesis. The cover crop will be cut four inches from the soil surface. This cut height is common for commercial harvest equipment in CT. A representative subsample of the cover crop will be collected at each growth stage and weighed for wet weight. It will be stored in a -20°C freezer to prevent chemical changes and shipped overnight to a commercial laboratory for testing. Cover crop forage will be tested for dry matter, crude protein, acid detergent fiber (ADF), neutral detergent fiber (NDF), lignin, fat, ash, non-fiber carbohydrates (NFC), relative feed value (RFV), total digestible nutrients (TDN), net energy for lactation (NEl), net energy-maintenance (NEm), net energy for gain (NEg), metabolized energy (ME), digestible energy (DE), and minerals (Ca, P, Mg, K, Na, Fe, Zn, Cu, Mn, Mo, and S). The remainder of cover crop at each growth stage will be removed from the field, not including the residue retained treatment. Data will be analyzed using appropriate procedures (such as ANOVA and regression) in SAS and R software.
- Investigate the impact of cover crop species and residue management on soil chemical properties and soil microbial diversity, community composition, and abundance, and link these impacts on nutrient cycling, nutrient uptake by corn, and corn silage yield.
Soil sampling, processing, storage, and lab analysis procedure for analysis of soil chemical properties will follow the standard protocol described on Recommended Soil Testing Procedures for the Northeastern United States (University of Delaware Cooperative Extension, 2011). Fall 2024 baseline fertility samples were collected at 15 cm depth on the date of cover crop planting. Soil total nitrogen and carbon will be analyzed using combustion methods on a Elementar CN Analyzer, soil phosphorus will be analyzed using modified Morgan method, soil mineral N will be analyzed using 1M KCl method.
Biological soil sampling will be conducted at cover crop anthesis (Finney et al., 2017). Soil samples will be collected between and within cover crop rows. Three soil cores will be collected from within cover crop rows and three soil cores will be collected between cover crop rows. The total of six cores will be stored and homogenized in the same zip lock bag. Latex gloves will be worn during sampling and equipment will be sterilized between each sampling using 70% ethanol. Samples will be stored in a cooler over ice packs in the field and for transportation. Each sample will be divided into two potions. One portion will be stored at -80°C until the microbiome analysis and another portion will be stored at -20°C until soil chemical analysis.
The standard protocol for soil microbiome sampling, processing, and lab analysis procedure will follow the standard protocol described in Schlatter et al. (2020). DNA will be extracted using the Qiagen DNeasy PowerSoil Pro extraction kit (Qiagen, Hilden, Germany) following manufacturer’s protocols. The V4 region of the 16S rRNA gene will be sequenced at the UConn Microbial Analysis, Resources, and Services facility (MARS). DNA extracts will be quantified using the Quant-iT PicoGreen kit and 30 ng of extracted DNA will be used as a template for amplifying the V4 region of the 16S rRNA gene. The V4 region will be amplified using 515F and 806R with Illumina adapters and dual indices. The PCR cycle will consist of incubation at 95°C for 3.5 minutes, 30 cycles of 30 s at 95°C, 30 s at 50°C, and 90 s at 72°C, with a final extension at 72°C for 10 minutes. The PCR products will be normalized based on the concentration of DNA from 250-400 bp and then pooled. The pooled PCR products will be cleaned using the Omega Bio-Tek Mag-Bind Beads according to the manufacturer’s protocol using 0.8x beads to PCR product. The cleaned pool will be sequenced on the MiSeq using v2 2x250 base pair kit (Illumina, Inc., San Diego, CA). qPCR will be utilized to obtain absolute abundance of organisms using a MARS 16S standard for bacteria.
Sequences will be processed in Mothur (v. 1.47.0). Sequences will be trimmed to remove low quality read areas, paired-end sequences will be merged, and chimeras will be removed. Sequences will be assigned taxonomically with the Silva reference database (Quast et al., 2012). Sequences identified as chloroplast and mitochondria will be removed. The pairwise distances between all aligned sequences will be calculated and sequences will be clustered into OTUs based on distances. The Shannon diversity index will be calculated to measure alpha diversity using phyloseq package (v 1.42.0) in R (v. 4.2.0). Samples will be rarefied to the depth of the lowest sample prior to analysis. The soil microbiome for each treatment will be characterized using relative abundance of multiple taxonomic levels. Differential abundance analysis will be conducted using the DeSeq2 package (v. 1.38.3) in R.
Cereal rye was seeded at a seeding rate of 117 kg ha-1 (43,871 seeds kg -1) and produced a mean fall plant population count of 1,960,000 seedling ha-1. Winter pea was seeded at a seeding rate of 100 kg ha-1 (7,716 seeds kg -1) and produced a mean fall plant population count of 920,000 seedling ha-1 (Table 1, Figures 1 & 2).
Figure 1. Cereal rye cover crop populations in fall 2024. The photos were taken on November 6th, 2024.
Figure 2. Winter pea cover crop populations in fall 2024. The photos were taken on November 6th, 2024.
Table 1. Means of fall plant population counts.
| Cover Crop Species | Fall Plant Population Counts (seedling hectare-1) |
| Cereal Rye | 1,960,000 |
| Winter Pea | 920,000 |
Data are displayed as means (n = 12).