Progress report for LNC19-417
Towards Resilient and Sustainable Grape Production in the North Central Region with Renewable Mulching Systems: Freezing stress, which could damage plant parts or kill whole vines, is the main challenge of grape production in cold regions in the U.S., including the North Central Region (NCR) leading to crop and vine losses. Soil hilling is a standard and somewhat effective cold protection practice for preventing vine loss. However, its negative impact on the soil-vine environment is a continuing problem because it contributes to soil degradation and declining vine health. Plant-based mulching is an alternative winter protection method that has not been widely adopted due to the cost of mulch and unavailability of specialized equipment in the market for its application. We propose to solve this problem by accomplishing the following objectives: 1) evaluate the efficacy and horticultural and environmental benefits of different types of renewable biomass mulch, 2) develop a mechanized prototype for mulch delivery, 3) engage local growers, throughout the life of the project, with the development/testing of a sustainable mulching system in their vineyards, and 4) evaluate the cost effectiveness of locally grown plant species and new mulching system compared to soil hilling. We expect that an optimum mulch, which provides winter protection while improving soil quality and vine performance, will be identified. We will also fabricate a mechanized apparatus that will deliver the mulch of choice. We will enhance producers’ knowledge and empowerment through education and engagement with project planning and execution. In the long-term, we predict that renewable biomass mulching will become an integral vineyard practice towards a resilient and sustainable grape production in the NCR.
Growers will learn about biomass mulches and their horticultural and environmental benefits through the following deliverables: 1) workshops/field days to educate about renewable biomass mulches and demonstrate a prototype for its application. 2) presentations at the annual Ohio Grape & Wine Conference (in 2021 and 2022), 3) production of two factsheets that summarize the pros and cons of each mulch and cost analysis of its application.
- Growers will use mulching and increase profits by reducing negative impacts on soil and vine productivity.
- Growers will be confident to adopt mulching with the gained knowledge of its cost-benefit.
Economic importance of grape and impact of cold damage on the industry: Grapes are the most valuable horticultural crop in the U.S., with a farm gate value of more than $6 billion (www.nass.usda.gov). The grape-wine industry in NCR has expanded rapidly in recent years with >1,000 wineries and annual economic impact of >$5 billion. Growing interest in this cash crop is driven by the steady increase of wine consumption in the U.S. (www.wineinstitute.org), the high value of winegrapes as an alternative and profitable crop in the NCR (Dami et al. 2005), and its adaptability to lands that are unsuitable for row crop production. The continued success of this industry relies on a sustainable grape production by mitigating crop/vine loss due to cold damage. In the U.S., cold damage is by far the most devastating weather event to fruit production, accounting for an average of $250 million/year of insurance payments for crop loss to grape and fruit growers (www.rma.usda.gov). In Ohio, grape growers have experienced major consecutive freezing damage episodes over the last ten years with unprecedented crop losses valued at $12 million following the “polar vortex” event in 2014 (Dami and Lewis 2014).
Winter protection by soil hilling and its limitations: To prevent complete vine loss, and due to its insulating properties, hilling with soil is cost-effective and has been the industry standard for winter protection for decades (Zabadal et al., 2007). Though effective for winter protection, soil hilling has several agricultural concerns involving its negative impacts on grapevine health. Plows can cause direct mechanical trunk damage, increasing disease susceptibility (Zabadal et al., 2007). It can also lead to excessive root pruning thus restrict root growth, reduce nutrient availability, and result in scion rooting. Higher weed pressure has also been correlated with soil hilling (Jiang et al., 2008). The repeated practices of soil hilling and de-hilling (removing hilled soil from vines in the spring) is destructive to soil physical, chemical, and biological features. It increases soil erosion and nutrient/pesticide runoff potential (Fu et al., 2006). It collapses soil pores resulting in compacted soil which restricts root growth and access to water and nutrients, and decreases water infiltration leading to ponding of water and damaged roots (Alspach, n.d., Zabadal et al., 2007).
Mulching in vineyards & soil quality: Unlike soil hilling, mulching adds organic matter, physically protects the soil, and intercepts soil contaminants which increases soil quality. This study will focus on several indicators of soil quality including soil organic matter, compaction, and water infiltration. Soil organic matter (SOM) is a major contributor to soil quality. It increases the cation exchange capacity of the soil, stabilizes soil aggregation, enhances soil water holding capacity and the ability to adsorb pesticides and other pollutants (Cooperband, 2002). SOM also supports soil trophic complexity which can have plant growth promoting, disease suppressing, and carbon sequestering effects (Moebius-Clune et al., 2016). Straw and other alternatives also reduce erosion by intercepting falling raindrops. Additionally, mulches were found to buffer temperatures as much as 12 °C higher than air temperatures (Zabadal et al., 2007) which effectively protects susceptible grapevine parts.
Mulches in vineyards have been shown to suppress weeds, retain moisture, enable nutrient release, increase organic matter, and increase yeast available nitrogen in grape juice (Agnew et al., 2001). DeVetter et al. (2015) evaluated four weed management strategies and found that straw mulch-treated soils had higher water content, organic matter, aggregate stability and biological activity, and reduced weed populations. Plant-based mulching is not new and has been tested as an alternate winter protection method. However, mulch has not been widely adopted due to its cost and the unavailability of specialized equipment for application. Commercial mulchers are primarily used for fertilizer application, are not designed for winter protection, and are not cost effective for small vineyards (<10 acres) in the NCR.
- Evaluate the efficacy and horticultural and environmental benefits of different types of renewable biomass mulch
- Developing a mechanized prototype for mulch delivery
- Engaging local growers throughout the project with the development/testing of a sustainable mulching system in their vineyards
- Evaluating the cost effectiveness of locally grown plant species and new mulching system compared to soil hilling
In Year 1, we have addressed the first three objectives and accomplishments are summarized below.
1. Evaluation of the Efficacy and Horticultural and Environmental Benefits of Different Types of Renewable Biomass Mulch
Experimental Sites and Treatments:
Three locations were used for this trial, one at the OSU research vineyard and the others at two commercial vineyards. Due to similarity of findings and for brevity, only the results from a commercial vineyard located in Geneva, Ohio, are presented. Cabernet franc, a commercially important variety was used.
To determine the efficacy of different types of renewable biomass, plant-based mulches were acquired and tested. Aloterra, an industry partner, provided Miscanthus for evaluation against commonly known mulches of Wheat Straw and Corn Stover in comparison to the conventional winter protection method of Soil Hilling to determine mulching impacts on grapevine physiology (growth, yield, fruit quality), health (crown gall incidence, scion rooting), and soil quality (moisture, compaction, infiltration, health indicators). Wheat Straw was used from small rectangular bales. Corn Stover was used from grinding round bales to a 1” particle size. Miscanthus was categorized into ‘chopped’ (~1” particle size) and ‘fine’ (< 1/4” particle size) and used at different experimental sites. All three different types of mulch were sent for Compost Analysis at a commercial laboratory to determine their nutrient content prior to application. Thus, the different mulch and soil treatments for the study included: Wheat Straw, Miscanthus (chopped), Miscanthus (fine), Corn Stover, and Soil Hill. Three treatments (Wheat Straw, Miscanthus, and Soil Hill) were used at the Geneva vineyard.
The grapevine rows at the commercial site were spaced 9 ft between the rows and 4 ft between the vines. The mulch and soil treatments were applied in November 2019. The mulch treatments were applied in mounds of 8” height, 2 ft around each vine and spread out at a height of around 3” in between the vines through an entire panel (Figures 1). Wheat Straw was applied from the small bales: 8” was removed from the bale along the bale length and was applied on either side of the graft union and 3” was applied in between the vines. Care was taken to spread the wheat straw in order to cover the graft unions as the mulch was applied from bales which were not shredded.
The amount of mulch applied for each treatment replicate was noted to conduct an economic impact analysis of the mulching method for winter protection as well as to determine the amount of mulch that needs to be reapplied for the following year after conducting a mulch height analysis on the amount mulch that receded through the winter.
Mulching Impact on Soil Environment:
Temperature monitoring for winter protection: A temperature sensor capable of measuring the temperature at two different locations was fabricated into measuring temperatures at 0” and 4” from ground level and was placed approximately 6” from the grapevine base in the center of the row (Figure 2). The sensors recorded the temperatures at 30-minute intervals and one sensor per treatment was installed for each of the Wheat Straw, Miscanthus (chopped), and Soil Hill treatments. The temperature sensors were installed in November 2019 and were kept in place through the winter and removed in Spring 2020 to give a complete picture of winter protection of grapevines. Air temperature was monitored at 5 ft above the ground level using HOBO temperature sensor (Onset Computer Corporation, Bourne, MA) attached to one of the panels along with a solar radiation shield at 30-minute intervals in order to overlay the ambient air temperature with respect to the mulch and soil temperatures (Figure 3).
Soil Moisture: A time-domain reflectometer (TDR) soil moisture meter (Spectrum Technologies, Inc., Aurora, IL) was used to measure soil moisture at approximately 2” depth increments in July 2020. The soil moisture meter probes were inserted in the soil under the mulch covers as well as de-hilled soil approximately 6” from the graft unions. The probes were capable of recording soil moisture content at 1.5”, 3”, 4.8” and 8” below the ground level. At least three observations of soil moisture at each depth were recorded for each treatment-replicate.
Infiltration: Soil infiltration rate (unsaturated hydraulic conductivity) was measured in July 2020. The mini-disk infiltrometer was placed on the soil under the mulch covers and de-hilled soil, approximately 6” from the graft unions, and the amount of water infiltrated was recorded with respect to time for each treatment (Zhang, R. (1997). The suction on the mini-disk infiltrometer was adjusted according to the rate of infiltration. The cumulative infiltration was plotted against the square root of time and a hydraulic conductivity (K) value was determined taking into consideration the respective parameters for the soil type from Van Genuchten tables (Dane et al., 2002; Dohnal et al., 2010). The soil type was classified as silty clay loam for the experimental site. One measurement was made with the mini-disk infiltrometer per each treatment replicate.
Soil Compaction: Surface and subsurface hardness was measured in July 2020 at 2” intervals of depth when the soil was at field capacity (approximately 48 hours following a soaking rain event) using a FieldScout field penetrometer (Spectrum Technologies, Inc., Aurora, IL). The soil compaction field penetrometer probe was inserted in the soil under the mulch covers as well as de-hilled soil approximately 6” from the graft unions in order to record the soil hardness at a certain depth. The probe was capable of recording soil compaction at 2” depth intervals. One observation of soil compaction was made for each treatment replicate up to 16” depth. A 1/2” cone was used for all measurements.
Tissue Nutrients: Tissue nutrients were determined by analyzing the nutrient content in petioles. A total of 60 petioles per treatment-replicate were collected in September 2020 at approximately 80% veraison for the Cabernet Franc variety at Ferrante and sent for nutrient content analysis at a commercial lab.
Soil Nutrients: Soil samples of approximately 1 lb. per treatment replicate (~1/4 lb. per randomly selected vine) were collected using a soil probe (JMC Soil Samplers, Newton, IA), the samples consisting of soil profiles up to 8” depth below the ground level collected at approximately 6” distance from the grapevine. Soil samples were collected in early-November of 2020 and were sent to Brookside Labs (New Bremen, OH) for standard nutrient analysis (pH, Cation Exchange Capacity, macronutrients, and micronutrients). Soil macro-nutrients along with the cation exchange capacity (which measures the soil’s ability to supply Ca, Mg, and K nutrients) for all the treatments are summarized in Table 3.
Soil Health: Active Soil Organic Matter (SOM) was measured through soil respiration, soil protein and active carbon analyses. Collectively these measurements provide insight into biologically-driven C and N dynamics in the soil.
Soil Erosion: Soil erosion was determined using soil aggregate method in Dr. Culman lab.
Mulching Impact on Weeds and Grapevine Physiology:
Weed Infestation: A thorough weed study was conducted in July 2020 at Ferrante. Weed cover percentage was estimated in the 3-ft wide vine rows between the first and last vine of each treatment replicate which included two panels of 24 ft each based on the amount of area that was under weed cover. Weed biomass was harvested in eight 1/4 m2 quadrats centered in each row for each treatment replicate around vines 1, 2, 3 and 4 in each panel in order to measure ‘around-vine’ weed biomass. Weed biomass was also harvested in eight 1/4 m2 quadrats centered in each row and placed in between vines 1-2, 2-3, 3-4 and 4-5 in each of the two panels for each treatment replicate in order to measure ‘inter-vine’ weed biomass.
Yield: Vine yield was measured at harvest time. The yield components consisted of collecting and recording cluster count per vine, crop weight per vine, and 100-berry weight for each treatment-replicate. Cabernet Franc was harvested in October 2020 and the yield components data were collected for at least four observations per treatment-replicate at Ferrante vineyard.
Fruit Quality: Fruit quality was determined by crushing 100 berry samples and measuring juice sugars, pH and acidity. The 100 berry samples were collected from each treatment replicate at the time of harvest in October 2020.
Scion Rooting and Crown Gall Incidence: Vine health was assessed by evaluating crown gall incidence and scion rooting per vine in late summer. The bacterial disease (crown gall) is associated with the occurrence of winter damage when the graft unions are unprotected from the cold temperatures and mechanical damage by the hilling/de-hilling equipment (Zabadal et al. 2007).
Vine Growth: Vine growth was assessed by collecting and weighing 1-year old cane prunings per vine in early spring. Due to the onset of the COVID-19 pandemic in March 2020 and the state-imposed lockdown, the pruning weights data at Ferrante vineyard were not collected due to the time sensitive nature of the data to be collected and the need to collect the pruning weight data in April. As such, the pruning weight data for 2019-2020 for the commercial vineyards in order to establish a baseline is not available. The vine growth in the 2020 growing season was assessed by collecting and weighing 1-year old cane prunings per vine in early spring (March 2021). Pruning weight per vine was collected for at least four vines per treatment replicate in each block for the Cabernet Franc.
Mulch Replenishment (Mulch Height):
In order to reduce cost of annual mulch application, we did not remove the mulches after winter, like is the case with soil (dehilling). Instead, we kept the mulches for the second season. However, w recorded how much was lost by measuring the mulch mound height. using a pair of 3 ft steel rulers.
2. Developing a Mechanized Prototype for Mulch Delivery:
We will design and develop a mechanized apparatus that delivers mulch from small square bales (22-in wide x 16-in high x 44-in long). The design can be adopted for large round (up to 6-ft diameter and 5-ft length) and square (up to 4-ft wide, 4-ft high and 8-ft long) bales. However, due to time and resource constraints of the proposed project we will develop a prototype for mulching small square bales only. Based on feedback from growers at the focus group meeting, our engineer team has developed a general blue print of a mechanized mulching equipment prototype that will comprise of: (i) frame to hold the baled biomass and shredder. The frame will be 30-in wide and 60-in long to accommodate both bale and shredder; (ii) baled biomass shredder. The shredder will be enclosed within the housing and powered with a tractor PTO. It will consist of a cylindrical rotor shaft with sickle-type cutter blades spaced evenly throughout the length of the shaft. The other specifications of the shredder, such as shaft and rotor diameter, blade angle and spacing, and housing dimensions, will be designed and used for prototype development; (iii) controlled rate bale feeder for shredder. We will develop the mechanism to feed bale to the shredder at a controlled rate using a hydraulic system; and (iv) mulch discharge device. The mulch discharge mechanism will comprise of a blower and a snout, and the discharge rate will be controlled by the shredder throughput.
3. Engaging Local Growers with Project Execution:
Grower’s willingness to adopt a methodology will be assessed via a researcher developed questionnaire in a pre-post test approach. The questionnaire will measure a grower’s perceptions of the innovation. Potential adopters of the technology will complete the questionnaire before engaging in the development process. Those same growers will then be involved with researchers to provide feedback and test the prototypes for their usability. Grower perceptions of their engagement with the process will also be assessed throughout via focus group discussions. Upon completion of the technology, growers will be given the post-questionnaire gauging their perceptions of the technology to assess their likelihood to adopt the technology. A control group of potential adopters, external to the technology development, will also be given the questionnaire to assess their likelihood to adopt the technology. This pre-post test approach will demonstrate the impact of grower involvement in technology development and their willingness to adopt.
- Evaluation of the efficacy and horticultural and environmental benefits of different types of renewable biomass mulch
Mulching Impact on Soil Environment:
Temperature monitoring for winter protection: It can be observed that all the mulch treatments provided adequate winter protection at the 0” and 4” height from ground compared to the conventional standard of soil hilling treatment. The temperatures at 0” from the ground level and 4” from the ground level were practically identical and > 32 °F for the Soil Hilling treatment throughout the winter period which would be the objective of any material being used to provide winter protection for grafted grapevines. The different mulches used in the study achieved this goal with the exception of Wheat Straw temperatures at 4” level being more deviant from the 0” level, although the temperature ranges were in the safe zone (> 28 °F) for providing the winter protection and preventing damage.
Soil Moisture: Preliminary results suggest that the soil moisture improves with soil depth. Further, all mulches had higher water content than the soil treatment. It was visually evident that the mulch cover retains soil moisture compared to bare soil. This confirms our hypothesis that mulch retains more moisture thus prevents soil dehydration and possible water stress of grapevines during dry periods in the summer.
Infiltration: The hydraulic conductivity was significant across the mulch treatments. Miscanthus had a significantly greater hydraulic conductivity compared to the Soil Hill treatment. Although Wheat Straw hydraulic conductivity was slightly greater than that of Soil Hill treatment, it was not significantly different.
Soil Compaction: Preliminary analysis suggests that the soil compaction decreased when mulch was applied.
Tissue Nutrients: Mulch treatment was significant on the Phosphorus, Potassium, and Sulfur content of the petioles and insignificant on the Nitrogen, Magnesium, and Calcium content. Miscanthus had a significantly greater P content whereas Wheat Straw had a significantly greater K content compared to all other treatments. According to the specific element recommendations for grapes (Dami et al. 2005, Wolf 2008) the N content was slightly below normal for all the mulch treatments; P content was above normal for all the treatments with Miscanthus having maximum P content; K content was in the normal range for all the treatments except for Wheat Straw which had slightly above normal K content; Mg content was excessive for all the treatments; and Ca content was in the normal range for all the mulch treatments.
Mulch treatment was insignificant for all the micro-nutrients. According to the specific element recommendations for grapes from petioles (Dami et al. 2005), Boron and Copper content were in the normal range, Manganese and Zinc contents were above normal, and Iron content was slightly below normal for all the treatments.
Soil Nutrients: CEC was not significantly different among all the treatments. Wheat Straw had significantly higher K content compared to all other treatments. According to the desirable range of soil macro-nutrients for grapes (Dami et al. 2005), P was below normal, K (wheat straw) and Mg were above normal, and Ca was normal.
There were no significant differences in soil micro-nutrients, except for Fe and Zn, among all treatments (Table 4). According to the desirable range of soil micro-nutrients for grapes (Dami et al. 2005), B was normal; Cu and Zn were above normal; and Fe, Mn, and Al were excessive.
The combination of soil and tissue nutrient status gives us a better assessment of how to manage nutrients in grapevines. For soil nutrient content, all macro- and micro-nutrients are available within or near the desirable range. K in Wheat Straw was above normal in both soil and tissue samples, suggesting that the Wheat Straw mulch may be adding more K in the soil. This may not be desirable since K has negative impact on fruit quality. This needs further investigation in 2021. Based on the soil-nutrient analysis results, there is no need to adjust nutrients with fertilizer amendment in 2021. Further, even though tissue N was low in all treatments, vine vigor (or size) is best judged in combination with pruning weights (see vine vigor section below). Nevertheless, Miscanthus had the lowest tissue N and this may be of concern. We plan to amend this treatment with N fertilizer in 2021. We will also measure N status at bloom, which may be a better indicator of N status.
Soil Health: SOM was not significantly different among treatments even though the Wheat straw showed an increased trend of POXC and mineralized C. Mineralizable carbon content is an indicator of short-term soil nutrient availability for plants. POXC and mineralizable carbon can be predictors of yield, vine vigor and fruit quality, however, this has not been established yet for grapevines. Soil pH values were 6.3-6.6 thus, within the optimum range for vinifera varieties such as Cabernet franc.
Soil Erosion: All mulch treatments increased the wet stable macro-aggregates above the mean for medium textured soils. For silt loams (6-18 CEC) with an aggregate stability of approximately 75%, a good POXC value is 580 mg/kg. POXC for Wheat Straw alone was above this value at Ferrante (Table 6). Soil aggregate stability below 25% is considered poor physical quality, 30 to 50% is considered low to medium physical quality, 50 to 75% medium to good physical quality, and above 80% is considered excellent physical quality, scaled over similar textured soils (Almajmaie et al., 2017). The soils at Ferrante had approximately 70-80% aggregate stability. Presence of more large soil macro-aggregates for the mulch treatments indicates lesser probability of soil erosion, faster infiltration, and a diverse habitat for micro-organisms in the soil (Mikha and Rice, 2004). Soil aggregate stability is considered as an indicator of soil health which protects organic matter, increases soil porosity and moisture availability and decreases soil compaction (Sundermeier and Shedekar, 2018).
Mulching Impact on Weeds and Grapevine Physiology
Weed Infestation: The mulch treatments were significant for the percentage weed cover and the ‘around-vine’ dry weight of grasses. Wheat Straw and Miscanthus treatments significantly reduced the percentage weed cover compared to the Soil Hill treatment at the 0.05 level and 0.10 level, respectively. Both mulch treatments significantly reduced the ‘around-vine’ dry weight of grasses and broadleaves at the 0.05 level and 0.10 level, respectively, compared to the Soil Hill treatment. The total weed dry weight was significantly reduced by Wheat Straw at the 0.05 level compared to Soil Hill treatment with Miscanthus also having a lower mean compared to Soil Hill. It must be noted that, for the Soil Hill (commercial standard) treatment there were pre-emergence and post-emergence herbicides applied which is the conventional practice. For the mulch treatments, however, no herbicides were applied, yet comparable reduction in weed cover and weed biomass to Soil Hilling treatment with herbicides was achieved. Therefore, we can conclude that application of mulch significantly reduced the overall weed growth. The reduction in the amount of herbicides applied and their manifestation into reduced costs will be detailed and a herbicide management plan specific to the mulch treatments will be established while conducting the techno-economic analysis for the mulching practice.
Yield: The mean estimated yield for Soil Hill, Miscanthus, and Wheat Straw were 5.6, 5.1, and 5.9 ton/acre respectively. Mulch treatment was insignificant on the 2020 yield and there were no significant differences between the yield for the different treatments. This suggests that mulch did not affect the yield of the grapevines and thus can be considered as a viable alternative to the conventional method of soil hilling without any deleterious effect on yield.
Fruit Quality: Mulch treatment was significant on the observed overall soluble solids (SS) of Cabernet Franc. Mulch treatment was insignificant on rest of the fruit quality parameters of berry pH, titratable acidity (TA), and fruit maturity index (SS/TA*10). Miscanthus mulch had significantly greater SS compared to Wheat Straw and was observed to be higher than the Soil Hill treatment. The variation in SS is attributed to crop size rather than treatment effect. In fact, vines with larger crop size tend to ripen the fruit later.
Scion Rooting and Crown Gall Incidence: No evident crown gall incidence was noted for all mulch treatments at all the experimental sites. This was expected since the winter of 2020 was mild. Scion rooting readily occurs if soil is left over the graft union. Scion rooting defeats the purpose of the rootstock and the vine size may gradually decline. With the mulching practice, since the mulches were of different types and particle sizes and were kept in place without removal around the graft unions, scion rooting per vine was evaluated at all the experimental sites. Scion rooting was evaluated in August 2020, by recording the number of scion roots per vine which were over 1.5” in length. The number of scion roots of length greater than 1.5” for each treatment were recorded. Scion rooting produced by Miscanthus and Wheat Straw mulch treatments left in place around graft unions were not significantly different from Soil Hill treatment which was removed from around the graft unions by de-hilling after the winter.
Vine Growth: Pruning weight in Miscanthus was significantly lower than that in soil or wheat Straw. Significantly lower pruning weights can be attributed to significantly lower Nitrogen content found in the tissue nutrients. It is suggested that Miscanthus mulch may have caused a reduction in vine vigor or size. Even though it is too early to draw conclusions, this may not be desirable as the mulch may weaken the vines unless additional N fertilizer is applied. Thus, the fertilizer management for miscanthus should be adjusted accordingly for desired increase in pruning weight. All vines from different treatments produced crop loads within the desirable range.
Mulch Replenishment (Mulch Height):
The mean mulch height when the treatments were applied in November 2019 was 8” from ground level. The mulch height measurements were collected from a constant distance of 6” horizontal distance for each vine. There was an overall decrease in the mulch heights for all the treatments from November 2019 to May 2020, although this decrease was not significant. In fall 2020, we replenished the mulches to the 8” height and we kept record of mulch amounts added for each treatment.
2. Developing a Mechanized Prototype for Mulch Delivery
Based on feedback from growers at the focus group meeting in February 2002, our engineering team has developed a general blueprint of a mechanized mulching equipment prototype that comprise of: (i) frame to hold the baled biomass and shredder; (ii) baled biomass shredder; (iii) controlled rate bale feeder for shredder; and (iv) mulch discharge device. After a thorough research, we found that there are some equipment in the market that already possess multiple features needed in the prototype. So, rather than re-invenit the wheel and to minimize cost and maximize efficiency, we purchased an equipment with the above features and that could deliver large size bales. Our plan is to retrofit this equipment and add the missing features to come up with a new prototype that satisfies the needs of grape growers (based on their input). It is our objective to complete these modifications and have the prototype ready this summer-fall (pending on pandemic situation) to test in the field.
3. Engaging Local Growers with Project Execution
We have used three-prong approach to engage growers with our project.
- Focus group: Feb 2020, discussion of project execution and sought input on prototype. We invited about a dozen of growers that own/manage small, medium, and large vineyards. Two cooperating growers who were involved since proposal write-up were also invited to participate at this focus group. We presented the project objectives and sought input on the mulching prototype. We received significant feedback that we used in our next step.
- Stakeholder baseline survey: Grower’s willingness to adopt mulching was assessed via a researcher developed questionnaire in a pre-post test approach. The questionnaire measured a grower’s perceptions of the innovation. Potential adopters of the technology completed the questionnaire before engaging in the development process. Those same growers will then be involved with researchers to provide feedback and test the prototypes for their usability. Grower perceptions of their engagement with the process will also be assessed throughout via focus group discussions. Upon completion of the technology, growers will be given the post-questionnaire gauging their perceptions of the technology to assess their likelihood to adopt the technology. A control group of potential adopters, external to the technology development, will also be given the questionnaire to assess their likelihood to adopt the technology. This pre-post test approach will demonstrate the impact of grower involvement in technology development and their willingness to adopt. Thus far, we conducted a pre-test survey.
- On-Farm Trials: Three cooperating growers hosted our mulch trials in commercial setting. Actually, the results presented in this report were collected from a commercial vineyard in Geneva, Ohio. It is our plan to continue the project at these commercial vineyards and repeat the trial during the 2020-2021 season.
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The results obtained during the 2019-2020 season from the three experimental sites with the mulching project are summarized below:
- All mulch treatments provided adequate winter protection comparable to the conventional standard of Soil Hill to the grapevines by keeping the temperatures around the graft union > 28 ° Wheat Straw mulch was more sensitive to the fluctuation of air temperature; however, it was concluded that this would be resolved by reducing the particle size through shredding of the straw bales.
- The mulch treatments produced yield and fruit quality comparable to the conventional method of Soil Hill. The yield and fruit quality parameters produced by the mulch treatments were in the desired range for respective varieties.
- From the tissue nutrient analysis, it was observed that the mulch treatments, in general, would reduce the amount of one or two macro-nutrients that are needed to be applied as part of the fertilizer management for the grapevines. This would potentially reduce the costs associated with the fertilizer application for the grapevines which will be analyzed in detail while conducting a techno-economic analysis.
- The mulch treatments, in general, reduced significantly the amount of weeds with no herbicide application compared to the conventional standard of Soil Hill with pre- and post-emergence herbicides. This would significantly reduce the costs associated with the herbicide application for the grapevines which will be analyzed in detail while conducting a techno-economic analysis.
- There was increased scion rooting observed with the Miscanthus (fine) mulch, however, the scion roots were brown and not functional. The scion rooting issue can be resolved by manipulating the particle size of the mulch applied.
- There was, in general, improved soil quality in terms of infiltration, moisture retention, and compaction due to the mulch treatments compared to the conventional standard of Soil Hill treatment. Soil health parameters seem to trend towards improvement in mulched treatments. However, we need a second year of data to confirm our findings.
- The mulch heights were tracked over the 2019-2020 season and the results showed that mulch can be intact around the graft unions for long periods of time. It is, however, recommended to replenish the mulch to achieve desired mulch heights after every growing season.
17 February 2020: Organized a focus group meeting and presented “Novel delivery system for vineyard mulching” at the Ohio Grape & Wine Conference, held in Dublin, Ohio. There were 15 in attendance representing grape growers that own/manage different size vineyards. The purpose of the meeting was to introduce the project and topic of vineyard mulching with focus on gathering feedback from stakeholders on developing a mulching prototype.
5 March 2020: Presented a project update titled: “Vineyard mulching: Is it worth it?” at the Northeast Ohio Winter Grape School hosted by Stonegait Winery, Madison, OH. There were 35 attendees, most were grape growers. This educational event was held in-person, just prior to the state-lockdown due to COVID pandemic. The purpose of the presentation was to educate about the topic of mulching in vineyards and introduce the project.
4 March 2021: Presented an update about the project titled: “Vineyard Mulching Project Research Update” at the OSU Winter Grape School. Due to COVID, this Zoom educational event was virtual. There were 38 attendees, most were grape growers. Preliminary findings of the mulching project were shared.
Educational & Outreach Activities
Activities above are educational events described in another section. Pending on the COVID situation, we plan to conduct a field demonstration.
- Vineyard mulching, benefits
It is too early to propose changes before finalizing findings and conclusions.