Developing low-cost sustainable sweet potato production strategies to facilitate adoption in the mid-south

Final Report for LS09-215

Project Type: Research and Education
Funds awarded in 2009: $185,000.00
Projected End Date: 12/31/2013
Region: Southern
State: Mississippi
Principal Investigator:
Dr. Ramon Arancibia
University of Missouri Extension
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Project Information

Abstract:

The responses of the sweetpotato crop to rotations with winter cover crops and conservational tillage (no till) were investigated in on-farm trials as well as at the experiment station. In addition, participatory adoption of cover crops was promoted and evaluated. Sweetpotato yields after winter cover crops and under conventional or conservational tillage were comparable and in some instances were superior to the conventional fallow treatment. Insect damage was similar among cover crops except for crimson clover which tended to be slightly higher at the research station. Participating farmers in Arkansas and Mississippi have gained knowledge on sustainable production systems and three growers in Mississippi have adopted winter cover crops. The information generated was presented and discussed with farmers through field days and presentations at grower’s meetings. Results were also presented at the National Sweetpotato Collaborators Group meeting and ASHS annual meetings.

Project Objectives:

1. Evaluate sustainable ground management strategies to improve sweetpotato production in a sustainable production system. 2. Develop sweetpotato planting strategies including planting method and type of planting material to increase production efficiency and reduce costs. 3. Promote adoption of sustainable sweetpotato production systems through farmer participation in on-farm research and demonstrations trials, workshops and publications.

Introduction:

The purpose of this project was to review and develop low-cost sustainable production strategies to facilitate adoption of sustainable practices in sweetpotato production. Many barriers to adoption of sustainable production systems have been reported in the southern region, but the fact that there was only one sustainable/organic sweetpotato farmer in Mississippi suggests little or no real incentive to adopt sustainable systems. Since production costs have risen due to increases in prices of inputs and oil, developing low-cost and effective sustainable production practices will be greatly welcomed by the agricultural community, especially small limited-resource farmers. This project was stakeholder driven and was developed with significant input from sweetpotato farmers in Mississippi and Arkansas. The Mississippi Sweetpotato Producer Advisory Committee meets once a year with Mississippi State University (MSU) personnel to communicate their concerns and suggests areas of investigation that would benefit them and the industry. Similarly, personnel at the University of Arkansas at Pine Bluff (UAPB) meet with limited-resource farmers in Arkansas twice a year. Among the main problems expressed by sweetpotato farmers in Mississippi are the lack of effective methods to control soil insect and nematodes, and high production costs. When asked about incorporating sustainable practices that may benefit their production systems, they indicated that “if they solve the problems inexpensively, they would take them in consideration”. In Arkansas, farmers indicated the absence of information on sweetpotato production technologies adapted to their needs. Similar to Mississippi, damage by soil insects is one of the main problems in Arkansas, but limited-resource farmers also indicated the high costs and lack of resources to invest in conventional technologies. Therefore, they expressed the need to develop reliable low-cost production practices adapted to the region. Sustainable sweetpotato production systems can be economically attractive when low-cost and efficient strategies are incorporated into the system. Integrating cover crops into a sweetpotato production system may improve soil fertility, reduce pest pressure and increase land use efficiency while reducing costs. Also, planting costs can be reduced by conservation tillage and by direct planting of root pieces/segments that would eliminate transplanting. To facilitate adoption, however, farmers need to experience a successful sustainable production system. Many pests can reduce quality and yield of sweetpotatoes. Insects and nematodes which damage the roots directly are the most troublesome. Control of these pests with chemicals is expensive and ineffective once the insect have reached the storage root below the soil surface. Conventional sweetpotato production is based on prophylactic use of pesticides against flying stages of insect pest, but for soil insects like sugarcane beetle (Eutheola humilis rugiceps) and wireworms (Coleoptera: Elateridae) sprays have proven ineffective. In Mississippi sugarcane beetle has become an important sweetpotato pest, particularly late in the season prior to harvest. Therefore, strategies to reduce pest incidence is needed. Many genera of plant-parasitic nematodes are associated with sweetpotato, but Meloidogyne (root-knot nematode) and Rotylenchulus (reniform nematode) have been associated with significant yield losses. Round to spindle swellings (galls) in fibrous root are the most evident symptoms of root-knot nematodes in sweetpotato. Longitudinal cracks similar to growth cracks are common on fleshy roots. Although reniform nematodes affect sweetpotato, the symptoms are not as obvious and can be confused with other pathogens. The use of soil pesticides such as Temik and K-PAM are recommended to manage nematodes, but in addition to environmental concerns they are expensive and unaffordable for most sweetpotato farmers. Therefore, low-cost sustainable management strategies designed to reduce nematode incidence will be welcomed by farmers. Cover crops are used in agronomic and horticultural cropping systems to reduce erosion, improve soil fertility, conserve soil moisture, and improve soil health in addition to other benefits. Deep rooted cover crops and high organic matter enhance soil biological activity and helps recycling soil nutrients, thus avoiding the potential for deep percolation. In addition, legume cover crops in their symbiotic association with Rhizobium species fix atmospheric nitrogen that is incorporated into the soil for use by the following crop. Therefore, production costs can be reduced by enhancing fertility and reducing or eliminating nitrogen fertilization. By improving soil health, cover crops can reduce pest incidence, hence, the incidence of sweetpotato soil pests and pesticide use can be reduced. Cover crops can provide nourishment to beneficial insects for subsequent crops or produce potent biocides that would impact soil pests. Studies have shown that the number of predaceous (beneficial) arthropods increases significantly when cultural tactics such as crop residues are not incorporated. In addition, Brassica cover crops can be used to suppress soil pests such as nematodes due to production of biocides such as glucosinolates. Some grasses can also be used as nematode suppressive crops. Therefore, cover crops may reduce pest incidence and pesticide use in sweetpotato which will increase yield, maximize profitability and promote environmental stewardship. Cost for conventional sweetpotato production is high leaving little room for error. Production starts with bedding seed roots to produce slips for field planting. This means that the farmer loses the opportunity to sell or has to buy seedstock to bed for slip production next year. Production of slips in beds requires bed preparation, in many cases under protected/heated structures, for roots to sprout early in the spring. When shoots have reached 12 in., slips are hand-cut for planting in the field which requires time and labor. Large scale operations use mechanized cutting and planting systems. At least 9 workers are necessary to operate a four-row transplanter. Therefore, bedding and planting sweetpotato slips not only shorten the growing season by 1 to 2 months limiting yield and profitability, but requires a great deal of investment in equipment, facilities, labor and inputs. Land preparation and fertilization are also costly. It includes multiple tillage events designed to leave a loose bed. Tillage events may include sub-soiling, disking, hilling, and then cultivation after planting. Fertilizer recommendations depend on soil tests, but high amounts of potassium are applied to sweetpotato. All these practices not only require equipment, energy and time, but increases erosion and soil degradation. Labor demands escalate as harvest begins. Roots are picked up by hand after the row is opened up by a digger or turning plow in some regions. Other areas use a semi-mechanical riding harvester manned by 8-10 workers who stand along a conveyor belt and pick the storage roots off the vines, sort, and place them into bins for curing and storage. In all, labor from bedding through harvest runs about 25-40% of total cost. Therefore, developing low-cost sustainable strategies to eliminate slip production and transplanting will reduce costs and increase crop profitability with a positive impact in the environment and the community. Direct field planting of propagules (root, root pieces and root segments) instead of transplanting slips is expected to reduce production costs incurred in labor, time, and energy. History indicates that planting storage root pieces is possible because sweetpotato crops were produced using root-pieces prior to the early 1900s. However, planting storage root pieces usually does not result in the development of new storage roots, but in an enlargement of the planted root piece which is not acceptable for fresh market. Although direct planting storage root pieces has been studied for some time to our knowledge pencil root segments have not been evaluated. Planting sweetpotato pencil root segments grown in the field could be accomplished at low cost for the farmer. Pencil roots (<15mm diameter) are long non-swollen roots originated from young thick or thin adventitious roots grown under conditions that are conducive to lignification of the stele. This type of propagule is limited in their capacity to enlarge and may favor development of storage roots from new adventitious roots. Therefore, developing a process to produce inexpensive propagules for direct field planting is easily justified by the potential economic benefit to the growers and the industry.

Cooperators

Click linked name(s) to expand
  • William Burdine
  • Fred Musser
  • Obadiah Njue
  • Mark Shankle

Research

Materials and methods:

This is a collaborative project between Mississippi State University and the University of Arkansas at Pine Bluff. On-farm research and demonstration trials were conducted in Mississippi and Arkansas at participating farms. The main research trial was conducted with a sustainable production system approach at the Pontotoc Ridge-Flatwoods Branch Experiment Station, Mississippi State University. Studies were conducted on Falkner silt loam (Fine-silty, siliceous, thermic Aquic Paledalfs) soils which is representative of soils in the Mississippi sweetpotato production area. An economic assessment to support the developing strategies was performed. Partial budgeting was used to assess the marginal benefit of the additional investment incurred when incorporating sustainable practices in sweetpotato production. Objective 1: Evaluate sustainable ground management strategies to improve sweetpotato production in a sustainable production system. Experiment 1- Selected winter cover crops along with a control fallow treatment were evaluated for 3 years on their effect on summer sweetpotato production. Winter cover crops were selected based on their potential advantages in suppressing nematodes and weeds, attracting beneficial insects, and on their role as source of N. Cover crops were wheat (Triticum aestivum), ryegrass (Lolium multiflorum), mustard (Sinapsis alba), radish (Raphanus sativus), rape (B. rapa), crimson clover (Trifolium incarnatum), and hairy vetch (Vicia villosa). Cover crops used in three on-farm trials were wheat, ryegrass, hairy vetch, crimson clover and radish. All cover crops were planted in the fall each year at recommended densities to optimize weed suppression and were incorporated 2-3 weeks prior to planting sweetpotato in the next spring. The experimental design was randomized complete block with cover crops as treatments (plots) and three or four replications depending on location. At the research station, cover crop plots were 18 by 18 m and six sweetpotato rows (6 m long and 1 m apart) were planted in the center of the plots. Alleys 12 m-wide were left between plots and disked two to three times in the season to keep it weed free. At the on-farm studies, cover crop plots were 30 by 30 m and all planted with sweetpotato after incorporation. The relatively large plot size and wide alleys were intended to isolate treatments and minimize movement of pest and beneficial arthropods among plots. Experiment 2- Selected cover crops (wheat, crimson clover, and hairy vetch) in combination with sweetpotato planting under conservational tillage (no till) were evaluated for 3 years to reduce the cost of land preparation which is associated with energy dependence. In this trial, cover crops were flail mowed 1-2 weeks prior to planting. A sweetpotato planter was modified to cut through the surface residue with a coulter and a shank followed by the planter that places the slips in the ground and closing it with lateral wheels. Cover crops were not fertilized, but sweetpotato was fertilized prior to planting based on recommendation by the soil tests. The experimental design was split plot with till/no till as the main treatments (plots) and cover crops as the secondary effect (subplots) with four replications. Evaluation- The effect of cover crops and/or conservational tillage on soil characteristics, beneficial and key pest insect species, and nematodes was evaluated during the trials. Cover crop biomass and changes in soil organic matter, CEC, pH, and nitrate were evaluated after incorporation. Sweetpotato nutritional status and growth were monitored also to determine the response to selected cover crops and reduced tillage. Sweetpotato yield and quality (USDA classification) was evaluated also to determine the responses to cover crops and conservational tillage. Beneficial insects including coccinellids (ladybird beetles) and carabids (ground beetles) as well as key sweetpotato pests including whitefringed beetles, cucumber beetles, click beetles, flea beetles, and lepidopteran insects were monitored with sweep-nets and sticky cards in the cover crops as well as in the sweetpotato crop to associate their incidence with specific cover crops. Ladybird beetle populations were visually counted to determine the number of adults per plant. Carabid beetles are usually nocturnal and abundant, so pitfall traps were used for monitoring carabid and other ground beetles. Oat traps were used to determine populations of wireworms. At harvest, 50 potatoes from each treatment and replicate were inspected for insect damage to associate the incidence with cover crop treatment. In addition, to evaluate effect of the cover crops on nematodes, soil samples were collected prior to the establishment of the cover crop and prior to sweetpotato planting and submitted to Mississippi State University for analysis and species identification. Objective 2. Develop sweetpotato planting strategies including planting method and type of planting material to increase production efficiency and reduce costs. Pencil root segments (4 to 6 inches) and small storage roots of no commercial value were evaluated as planting material and compared with conventional slip planting. Experiments were conducted at the Pontotoc Ridge-Flatwoods Experiment Station, Mississippi State University. Experiment 1- In 2009, small storage roots and pencil roots segments of Beauregard sweetpotato were stored overwinter under commercial conditions (60oF, 70%-80% RH) to determine storability of the propagation material. The quality of the planting material after winter storage was evaluated visually. Direct planting of pre-sprouted and non-sprouted (control) roots was conducted by hand at the same spacing as slip planting (1 m between row and 0.30 m within row spacing). Roots and root segments were placed 15 cm deep in the row. Emergence and sprouting after 4 weeks was determined. At harvest, the number and weight of new storage roots formed from the sprouts and old storage roots were evaluated. The experimental design was randomized complete block with planting material as treatments (plots) with three replications. Experiment 2- Planting depth of seed roots to inhibit growth of the old storage root and promote storage root initiation was investigated in 2011. As the seed root is placed deeper in the ground, it is expected an inhibition of growth. Two commercial varieties for fresh market (Beauregard, Evangeline) were used. Seed roots were planted at 5 and 2 inches deep (from the top of the root) on flat ground. Once roots sprouted and shoots were about 12 inches long, rows were hipped up to partially cover the base of the shoots and promote adventitious rooting. Actual planting depth was about 7 and 10 inches deep. At harvest, yield of old and new storage roots were evaluated. The experimental design was a split plot with planting depth as treatments (plots) and varieties as secondary effect (subplots) with four replications. Experiment 3- A variety trial was conducted to determine differences in the ability to reduce growth of the old seed root and suitability for direct planting. Two commercial varieties for fresh market (Beauregard and Covington) and two feedstock varieties (03-007 and 06-312) were used. Seed roots were planted at 2 inches deep in flat ground and the beds formed after as described above. Actual planting depth was about 6 inches deep. At harvest, number and weight of old and new storage roots and marketable yield were determined. The experimental design was a randomized complete block with varieties as the main treatment (plots) with four replications. Objective 3: Promote adoption of sustainable sweetpotato production systems through farmer participation in on-farm research and demonstrations trials, workshops and publications. On-farm research and demonstration trials were implemented (5 in MS and 4 in AR) to demonstrate and promote adoption of sustainable production practices. Field days, workshops, and presentations at grower’s meetings and professional associations were the venues to disseminate the information generated. On-farm research and demonstration trials were implemented also to applied sustainable strategies based on the participating farmer interests. - Penick farms in Vardaman, MS, Mr. Langston has a 100-acre organic sweetpotato production system in Chickasaw Co., MS. A one year cover crop trial with 5 species was conducted in the organic field. Then hairy vetch and sweet pea were adopted as winter cover crops. - Stephen Bailey manages a family operated 250-acre farm in Webster Co., MS. He tested and adopted a mixture of radish and hairy vetch cover crops to manage nematodes, soil fertility and tilth in his field. - Jamie Earp manages a 400 acre family farm in Chickasaw Co., MS. He assisted in the 3-year on-farm trial with five cover crops to increase soil organic matter. - Norman Clark manage 100 acres of sweetpotato in Calhoun Co., MS. Assited in the on-farm trial with five cover crops including Brassicas to suppress nematodes. - At Nature Son, William Reed manages a 30 acres organic vegetable farm in Lee Co. He began growing organic sweetpotato in the last two years. - Stephen Walker in Jefferson County, AR, incorporated cover crop to reduce pest incidence towards reducing the dependence on synthetic pesticide use. - Isiah Cline near Pine Bluff, AR is transitioning to organic farming and incorporated cover crops to improve soil fertility and reduce cost of sweetpotato down. - Shirley Bradley in Phillips County, AR, incorporated cover crops with the potential to reduce the dependence on synthetic pesticides and fertilizers. - Jimmie Edwards in Jefferson County, AR, incorporated cover crops to reduce production costs and with potential to reduce pest pressure and increase soil fertility.

Research results and discussion:

Objective 1: Evaluate sustainable ground management strategies to improve sweetpotato production in a sustainable production system. Experiment 1- Three years of on-farm and station trials with winter cover crops incorporated prior to sweetpotato planting were evaluated. Cover crops tested were legumes (crimson clover and hairy vetch), grasses (wheat and ryegrass) and Brassicas (radish, rape and mustard). Biomass production varied each year depending on time of planting in the fall. Cover crops planted early in the fall (Sept. 2010) resulted in biomass production of 4-6 ton/acre for legumes in comparison to late planting (Nov. 2009) which resulted in 1-2 ton/acre. Legumes, radish and rape produced consistently more biomass than weedy fallow. Among them, legumes and radish were the best biomass producers. Wheat and ryegrass biomass production was inconsistent: the same or larger than weedy fallow depending on location and year. Mustard produced the same biomass as weedy fallow in all situations/locations. There was a positive but inconsistent response in soil organic matter to cover crops. Total soil organic matter was the same among all cover crops and weedy fallow. Although organic matter appeared to have a slight positive response to vetch, radish and grasses in 2011, this was inconsistent and in year three differences were not detected. Therefore, total soil organic matter was maintained throughout the three years of this study suggesting that the amount of biomass incorporated was insufficient to increase soil organic matter. Similarly, soil pH and cation exchange capacity (CEC) were the same among cover crops and weedy fallow. There were differences in soil nitrate among cover crops and weedy fallow. The soil nitrate content in weedy fallow was similar among the years and ranged between 24 and 40 ppm. Soil nitrate were consistently reduced after wheat and ryegrass cover crops in comparison to weedy fallow. Soil nitrate after Brassica cover crops, however, was inconsistent: it was reduced, the same or increased depending on year and location. In contrast, soil nitrate after legume cover crops was the same in 2010, but increased in the second and third year (2011 and 2012) in comparison to weedy fallow. This is useful information for sustainability of sweetpotato since it requires 40 to 60 lb/acre nitrogen and legume cover crops may provide 60 to 150 lb/acre nitrogen depending on biomass production. Brassica cover crops were tested for their effect on nematode population at the station and at two on-farm studies. Root-knot nematodes were practically undetectable in all sites and years during the study. Reniform nematode populations at the research station and one on-farm study were not detected in 2010. In both sites, reniform populations increased by 2012 after three years of sweetpotato ranging between 0 and 300/pt soil. In the on-farm studies, reniform population was reduced only in the radish cover crop. At the research station, however, there were no differences among cover crops. In the second on-farm study, reniform nematode populations were high (500 to 3000/pt soil) and there were no differences among cover crops species. Sweetpotato yield was the same among cover crops in 2010 and 2011. Sweetpotato yield is classified in US No.1 (the most valuable category for fresh market) canners and jumbo (destined to processing). Total marketable yield corresponded to the total of the three categories. In 2010, US No.1 yield ranged between 150 and 230 bushel/acre, and marketable yield ranged between 250 and 350 bushel/acre. In 2011, US No.1 ranged between 200 and 350 bushel/acre, and marketable yield ranged between 350 and 500 bushel/acre. In both years US No.1 and total marketable yield were the same among cover crops and weedy fallow. In 2012, however, sweetpotato yield increased in the on-farm trial with radish (320 and 500 bushel/acre for US No.1 and marketable yield, respectively), ryegrass (380 and 580 bushel/acre for US No.1 and marketable yield, respectively) and wheat (385 and 590 bushel/acre for US No.1 and marketable yield, respectively) in comparison to weedy fallow (200 and 420 bushel/acre for US No.1 and marketable yield, respectively). At the research station, US No.1 yield ranged between 250 and 510 bushel/acre and marketable yield ranged between 360 and 700 bushel/acre. There were no differences among cover crops and weedy fallow. This suggests that adopting winter cover crops does not reduced sweetpotato yield the following summer, but may increase it in the long run. Pitfall traps. Arthropod densities varied within treatments at each location. At Pontotoc, cover crop had an impact on arthropod densities. Among the cover crops tested under tilled conditions, the mustard cover crop had fewer ground beetles, June beetles and parasitoids than most other covers, but had among the highest numbers of sweet potato flea beetles and ants. The wheat cover crop had low numbers of click beetles, sweet potato flea beetles and ground beetles. The ryegrass + rape cover crop had high numbers of sweet potato flea beetle and click beetles, but low numbers of spiders. The radish + vetch cover had few sweetpotato flea beetles, but had high numbers of June beetles. Fallow ground without any insecticide had high numbers of ground beetles, but low numbers of click beetles. In contrast, fallow with an insecticide had high numbers of spiders, but low numbers of ants. The crimson clover cover led to high numbers of ants and low numbers of June beetles. Parasitoids were more abundant following rape as a cover, and less abundant following hairy vetch as a cover. Of the insects monitored, the only group strongly impacted by a Daikon radish cover crop was ants, which were less abundant. At the Chickasaw County location1 (conventional field), densities of sweet potato flea beetle, click beetle, June beetles and ants were very low. The other arthropods were more abundant there were no differences among cover crops. At the Chickasaw County 2 location (organic field), different cover crops were grown during 2010 and 2011, so the years were analyzed independently. The cover crop made no difference on any insect during 2010. In 2011 the farmer planted half of the field to peas and half to hairy vetch. Evaluation of soil insects indicated that field peas supported the highest densities of carabids, parasitoids and ants. Insect Damage at harvest. Insect damage on sweetpotatoes at harvest at the Pontotoc location was combined over the three years except for white grub damage which was only present during 2012. The cover crop treatments were only significantly different in the abundance of large wireworm holes, with hairy vetch having more large holes than most other treatments. At the Chicksaw County 1 location, there was virtually no damage on any treatments during 2011 and 2012, so only 2010 data are reported. During 2010, the rape cover crop resulted in higher levels of Diabrotica and wireworm damage compared to the other treatments. However, insect damage was high in all treatments, so there was no significant difference in the percentage of potatoes without any damage. At the Chickasaw 2 location, there were significant differences among cover crops in all categories during both 2010 and 2011. In 2010, mustard was the best performer. In2011, hairy vetch had fewer large holes and higher proportion of undamaged storage roots. Experiment 2- Three years conservational tillage (no till) trials were conducted at the experiment station to evaluate the adaptability of sweetpotato to no till planting after winter cover crop and fallow. Cover crop biomass production was similar to conventional tillage and varied depending on cover crop and time of planting. Changes in organic matter, CEC and pH by conservational tillage were not detected in this study. Planting sweetpotato slips under no tillage conditions was achieved with a modified mechanical sweetpotato transplanter. A coulter and a sub-soiling shank were included to break the ground and open a slit which facilitated planting into the stale bed. This resulted in better plant stand and growth. In addition, access to planting in plots with conservational tillage was sooner than conventionally cultivated field, in particular after a heavy rain. Conservational tillage appears to have no detrimental effect on yield and yield classification. In 2010, sweetpotato yield was reduced under no tillage, except for hairy vetch, mainly due to poor plant stand. This yield reduction under no-tillage was not detected in 2011 and 2012. Two factors may have been involved in good plant stand: use of the modified no-till planter and soil moisture. Again in 2012, conservational tillage had no detrimental effect on yield. Our results suggest that cover crops and conservational tillage may help in soil conservation and improvement, and in reducing production costs without sacrificing yield. However, soil type and moisture at planting may play a role in the success of the conservational tillage system. Tillage system had an impact on insect population in the pitfall traps. There was an increase in populations of spiders in the no-till system. Click beetle increased in fallow and the mix of clover and ryegrass under no till. Ants were reduced in vetch and in the mix of clover and ryegrass both under no-till. Tillage impacted the proportion of storage root damaged by insect. There were fewer large holes which resulted in a greater percentage of potatoes without any insect damage. Objective 2. Develop sweetpotato planting strategies including planting method and type of planting material to increase production efficiency and reduce costs. Experiment 1- Direct planting of sweetpotato seed roots was investigated in Mississippi to reduce planting costs. Storability of small storage roots under commercial conditions (60oF, 70%-80% RH) was similar to marketable storage roots. In contrast, storability of pencil root segments was poor. Pencil roots segments were mostly dry (62%) and rotten (38%) suggesting that pencil roots require improved storage condition. In 2010, pre-sprouted and non-sprouted Beauregard seed roots and pencil root segments were hand planted in raised beds. Emergence of pencil root segments was poor (less than 5%). Emergence of pre-sprouted and non-sprouted seed roots was 95% and 55%, respectively. The average number of shoots was 6 to 8 shoots/root. New storage roots were initiated out of the adventitious roots emerged from the underground section of these shoots, but the old mother roots continued to grow as well. Therefore, old and new storage roots were harvested and evaluated. Yield of new and old storage roots from pre-sprouted root seed were 400 and 360 bushel/acre, respectively, and yield of non-sprouted root seed was 382 and 180 bushel/acre, respectively. This confirms previous studies recommending a pre-sprouting treatment of root for seed. However, the large yield of old overgrown mother roots with no commercial value may have been in detriment of new storage root yield. Experiment 2- In 2011 direct planting focused on planting depth in flat ground and covering the base of the shoots after emergence. Yield of old and new storage roots in Evangeline were not affected by planting depth and averaged 387 and 139 bushel/acre, respectively. In contrast, yield of Beauregard old roots planted at 7 and 10 inches deep was 534 and 246 bushel/acre, respectively. Therefore, planting seed roots deeper appears to reduce development of old mother plants. However, this effect was not reflected in increased yield of new roots. Planting in flat ground and later covering the base of the shoots with soil appears to have potential in direct planting seed roots. Experiment 3- A variety trial was conducted to determine suitability for direct planting. Storage roots were planted in flat ground and hipped after they sprouted to inhibit growth of the old root and promote development of new storage roots. There were differences in growth of old seed root among varieties and consequently suitability for direct planting. Yield of old seed root in Beauregard was similar to the marketable yield of new storage roots (346 and 318 bushel/acre, respectively) indicating that Beauregard is not suitable for direct planting. The old seed root of 03-007 also continue to grow but to a lesser extent than Beauregard. Yield of old seed root and new marketable storage roots were 223 and 572 bushel/acre, respectively. In contrast, old seed root growth of Covington and 06-312 was minimal to none with yield of 51 and 21 bushel/acre, respectively. Marketable yield for Covington and 06-312 was 269 and 489 bushel/acre, respectively. Therefore, Covington and 06-312 appear to be more suitable for direct planting. Objective 3: Promote adoption of sustainable sweetpotato production systems through farmer participation in on-farm research and demonstrations trials, workshops and publications. During this project, sustainable practices have been promoted in Mississippi and Arkansas through on-farm demonstration studies with cover crops, one to one discussion with participating growers and a workshop. On-farm research and demonstration trials were implemented to applied sustainable strategies based on the participating farmer interests. The on-farm studies and the participating farmers were available and received visitors interested in learning about their experiences. The outcome from the on-farm studies are: - Stephen Bailey has adopted a mixture of radish, ryegrass and hairy vetch cover crops to manage nematodes, soil fertility and tilth in his field for two years already. Mr. Bailey is innovative, well known among sweetpotato growers and has shared his experiences with other growers. It is expected that other growers would follow his initiative to adopt cover crops. - Jamie Earp has assisted in the on-farm trial with five cover crops for three years to increase soil organic matter. The effect on insect population and damage to roots were evaluated also in this on-farm trial. Mr. Earp is a former president of the MS aweetpotato Council and has shared his experiences with other farmers. - At Penick farms in Vardaman, MS, Mr. Langston assisted in the on-farm cover crops trial the first year. In the second year he tested and adopted hairy vetch and sweet pea in the 100-acre organic field to integrate cover crop rotations and improve soil fertility. Also, insect populations and damage to roots were compared with an adjacent conventional field. Penick Produce is one of the largest conventional sweetpotato producers and shippers in Mississippi and is well known for taking innovative approaches to improve sustainability in the industry. He has and always willing to share his experiences with growers. - Norman Clark is also a former president of the MS sweetpotato Council willing to share his experiences in production. The on-farm trial with five cover crops including Brassicas to suppress nematodes was conducted in his field because of the high nematode population. However the test with sweetpotato was not completed. - At Nature Son, William Reed has established a rotation with cover crops in his organic farm and 2 years ago he incorporated sweetpotato to the production system. The effect of organic management on insect damage was evaluated in this trial in 2013. - Stephen Walker (Jefferson County, AR) has adopted sustainable practices in his vegetable operation. He learned of the low incidence of insects, increased yield of crops after cover crops, and less fertilizer requirements. - Isiah Cline near Pine Bluff, AR is transitioning to organic farming and incorporated cover crops to improve soil fertility and reduce cost of sweetpotato down. - Shirley Bradley (Phillips County, AR) found minimal insect damage to sweetpotato roots and improved soil quality after cover crops. - Jimmie Edwards (Jefferson County, AR) incorporated cover crops to reduce production costs and with potential to reduce pest pressure and increase soil fertility. Participating farmers in Mississippi and Arkansas over these three years have gained knowledge on cover crops and sustainable production of sweetpotatoes. In Mississippi, two of the initial three participating farmers have continued planting cover crops in their fields. These represent an 80 acre conventional field and a 100 acre organic field. In Arkansas, farmers continued cover crops rotations on their own and have indicated that they will continue to share the practice with other farmers. One sustainability workshop and two field tours showcasing the on-station research trial were conducted. The workshop focused on cover crops and sustainable soil management in addition to pest and weed management. The field tour at the Pontotoc Ridge-Flatwoods Experiment Station showcased the cover crop and the conservational tillage trials. Similarly, two vegetable production workshops to discuss sustainable production systems were conducted. Two of the project’s contact farmers participated and shared their sustainable production experiences. In addition, results of the cover crop trials were presented and discussed with farmers at the Sustainable Agriculture Working Group (SAWG) meeting in Little Rock, AR in 2012 and 2013, every year at the Mississippi Sweetpotato Production Meeting in Pittsboro, MS, every year at the Mississippi Sweetpotato Producer Advisory Council (PAC) meeting in Verona, MS, and at the MS Fruit & Vegetable Growers/Agritourism Conference & Trade Show in Jackson, MS in 2012. In addition, results were presented every year to peers at the National Sweetpotato Collaborators Group meetings and at the ASHS meetings.

Participation Summary

Educational & Outreach Activities

Participation Summary:

Education/outreach description:

Main, J.L., R.A. Arancibia and W.B. Evans. 2013. Cover Crops and Tillage Systems: Three Years of Impacts on Soil Characteristics and Sweetpotato Yield in North Mississippi ASHS Annual conference, July 22-25, Palm Desert, CA. Main, J.L., R.A. Arancibia and W.B. Evans. 2013. Cover Crops in Conventional Tillage System: Three Years of Impacts on Soil Characteristics and Sweetpotato Yield in North Mississippi. ASHS Annual conference, July 22-25, Palm Desert, CA. Main, J.L., X. Wang, L.B. Grelen, and R.A. Arancibia. 2013. Three years of winter cover crops effect on soil characteristics and sweetpotato production in North Mississippi. NSPCG/SR-ASHS annual meeting, February 2-3, Orlando, FL. Main,J.L. and R.A. Arancibia. 2013. Three years sweetpotato production with winter cover crops and stale beds in North Mississippi. NSPCG/SR-ASHS annual meeting, February 2-3, Orlando, FL. Main, J. and R.A. Arancibia, 2013. Cover Crops and Tillage Practices; Third Year Impacts on Soil Characteristics and Sweetpotato Yield in North Mississippi 22th SSAWG Conference, January 24-26, Little Rock, AR Main, J. and R.A. Arancibia, 2012. Winter Cover Crops Effect on Soil Characteristics and Sweetpotato Production in North Mississippi. NSPCG/SR-ASHS annual meeting, February 4-5, Birmingham, AL. HortScience 47:S41 Main, J. and R.A. Arancibia, 2012. Use of Stale Beds in North Mississippi Sweetpotato Production. NSPCG/SR-ASHS annual meeting, February 4-5, Birmingham, AL. HortScience 47:S42 Babu, A., F.R. Musser, J.T. Reed, R.A. Arancibia and J. Main, 2012. Evaluation of Cover Crops and Tillage Systems as IPM Components for Sustainable Sweetpotato Production Systems. NSPCG/SR-ASHS annual meeting, February 4-5, Birmingham, AL. HortScience 47:S42 Main, J.L. and R.A. Arancibia, 2012. Cover Crops and Tillage; Second Year Impacts on Soil Characteristics and Sweetpotato Yield in North Mississippi. 21th SSAWG Conference, January 18-21, Little Rock, AR Arancibia R.A. and J.L. Main 2011. First Year Cover Crops In Mississippi Increased Soil Organic Matter In Conventionally Managed Sweetpotato, but Had No Effect On Yield. HortScience 46(9):S364 Babu, A., F. Musser, J. Reed and R. Arancibia. 2011. Impact of cover crops on sweet potato insects. Entomol. Soc. of America annual meeting, Nov. 14, Reno, NV Main, J., R.A. Arancibia and M. Shankle. 2011. First year results of various cover crops on Mississippi sweet potato production. Annual meeting of the NSCG, January 22-23, 2011, Orange Beach, AL http://www.nscg.viazivitamu.org/

Project Outcomes

Project outcomes:

This project has evaluated and generated information about the benefits of adopting sustainable practices adapted to the Southern region that are cost efficient and promote stewardship of the farm land. Three participating farmers in Mississippi (Bailey, Penick and Reed) have adopted winter/spring cover crops as part of their sweetpotato production system for two consecutive years. On-farm studies allowed farmers to experience and gain knowledge on cover crops and sustainable practices so they could take informed decision to adopt the practices. Two of the participating Mississippi growers are or have been members of the MS Sweetpotato Council and are well known among sweetpotato farmers who look up to them for innovative production practices. Therefore, it is expected that more farmers will learn about sustainable production practices in Mississippi. Information on conservational tillage and direct seed-root planting was generated. These technologies look promising in reducing production costs and would impact directly on the energy requirements and the environment. However, conservational tillage was not part of the on-farm studies. Conservational tillage may be more beneficial to the processing industry which has expanded significantly in the last two years because of the health attributes of sweetpotato. This technology may help in reducing the high production cost that still act as a barrier to further expansion. Although direct planting has the potential to reduce costs, developing suitable varieties for direct planting is essential. The major accomplishment of this project in Arkansas is that three, namely, Mr. Walker, Mr. Cline and Mr. Bradley (husband of the late Mrs. Bradley) have adopted the concept of sustainable production of sweetpotatoes using cover crops. They now clearly understand the benefits of cover crops in vegetable crop production systems. They understand and also shared their knowledge on the benefits of use of cover crops in their vegetable crop production systems. None grew sweetpotatoes before this project but have incorporated sweetpotato to their operation. The participating farmers are now experienced master trainers in the use of sustainable production methods. With the exception of the late Mrs. Edwards all of our contact farmers have expressed great satisfaction with the sustainable production system. This may be considered as 100% adoption rate. See attached letters from two the contact farmers.

Economic Analysis

Cover crops: Yield of sweetpotato after cover crops was similar to the weedy fallow in the first 2 years, but increased with radish, ryegrass and wheat in the on-farm study in the third year. Therefore under the farmer conditions in the third year, the average net income (gross income minus costs) with these three cover crops increased by $870/acre in comparison to the weedy fallow. The average net return to the additional investment ($135/acre) of incorporating cover crops was 6.4 times for this year. Continuation of this type of trial and testing the effect on nematode populations would provide more information about their relationship with improved yield. No-till: A brief economic assessment of planting into stale beds indicated that only the two spring disk-harrows can be saved since fall ground preparation will still be needed for cover crops and bed formation. Each disk-harrowing cost $17.5/acre, so planting costs may be reduced by $35/acre. An additional advantage is the prompt access to the field to plant after a rain. Direct planting: The economic assessment of direct planting small seed roots should be taken with caution because the complications derived from the excessive growth of the mother root in detriment of the new marketable roots. Covington appeared to be more suitable than Beauregard, but the yield of marketable roots was reduced in comparison to yield from conventional slip planted crop and the assessment indicated that is not feasible. Therefore, potential for direct planting will require development of suitable high yielding varieties.

Farmer Adoption

The success of this project is determined by the number of growers that adopt the new technology. In Mississippi, two of the initial participating sweetpotato growers (R. Langston at Penick Produce and S. Bailey) have adopted winter cover crops in their production systems for two years now. In addition, Will Reed at Nature Son has already established a rotation program with winter cover crops in his organic vegetable farm. Now he has included sweetpotato to his production system. The third participating sweetpotato farmer liked the results, but is yet to adopt the practice. The major accomplishment of this project is that three, namely, Mr. Walker, Mr. Cline and Mr. Bradley (husband of the late Mrs. Bradley) have adopted the concept of sustainable production of sweetpotatoes using cover crops. They now clearly understand the benefits of cover crops in vegetable crop production systems. With the exception of the late Mrs. Edwards all of our contact farmers have expressed great satisfaction with the sustainable production system. This may be considered as 100% adoption rate. See attached letters from two the contact farmers.

Recommendations:

Areas needing additional study

The use of Brassica cover crop to suppress nematode population and its effect on sweetpotato production still need further investigation. The land with high nematode population was rotated to other crop so the evaluation with sweetpotato was not completed. A long term sweetpotato study that includes rotation with Brassica cover crops in a heavily infested field is warranted. Similarly, studies to optimize nitrogen fertilization when using legume cover crops is needed to establish the economic feasibility for its adoption. Results of using conservational tillage indicate that is a promising technology to improve stewardship of the land and to reduce insect damage and cost. It had less insect damage than roots from conventionally tilled crop. Further studies are needed to adjust to different conditions and fertilization programs as well as to corroborate the reduced insect damage. Additional studies on direct planting with suitable varieties is warranted. Improving this technology may benefit directly the processing sector to be able to expand the market.

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.