IMPROVING ORGANIC CROPPING SYSTEMS FOR NORTH CAROLINA

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 1001945
• Project Start Date: Nov 5, 2013
• Project End Date: Sep 30, 2018
• Program Code: [(N/A)]- (N/A)

Recipient Organization
NORTH CAROLINA STATE UNIV
(N/A)
RALEIGH,NC 27695

Performing Department
Crop Science

Non Technical Summary
Organic grain cultivation continues to increase in the Southeastern and mid-Atlantic regions (Dimitri 2008; Hamilton and Rzewnicki 2007a). In North Carolina, the number of organic field crop growers has expanded considerably within the last two years and farms are rapidly expanding their acreage. An informal census in North Carolina estimates the acreage of corn, soybean, and wheat expanded from 950 acres in 2006 to 12,000 acres in 2011. Pest management and the use of crop breeding to address pests are cited by these farmers as one of their top concerns during panel discussions and in surveys. Other concerns are reducing tillage, and diversifying the number of organic crops. The public at large is also increasing interested in the environmental impact of agriculture, include the greenhouse gas emissions from farming. This project coalesces research on all of these topics.

Animal Health Component

100%

Research Effort Categories

Basic

(N/A)

Applied

100%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
102	1820	1070	33%
102	1510	1070	33%
102	1542	1070	34%

Knowledge Area
102 - Soil, Plant, Water, Nutrient Relationships;

Subject Of Investigation
1510 - Corn; 1542 - Soft red wheat; 1820 - Soybean;

Field Of Science
1070 - Ecology;

Keywords

organic

corn

soybeans

wheat

Goals / Objectives
Goals: 1. Collaborate with plant breeders to develop cultivars suitable for organic systems. 2. Reduce tillage on organic farms. 3. Find alternative crops to lengthen rotations and enhance profitability of North Carolina's organic farmers. Plant Breeding for Organic Systems Organic grain cultivation continues to increase in the Southeastern and mid-Atlantic regions (Dimitri 2008; Hamilton and Rzewnicki 2007a). In North Carolina, the number of organic field crop growers has expanded considerably within the last two years and farms are rapidly expanding their acreage. An informal census in North Carolina estimates the acreage of corn, soybean, and wheat expanded from 950 acres in 2006 to 12,000 acres in 2011. Pest management and the use of crop breeding to address pests are cited by these farmers as one of their top concerns during panel discussions and in surveys. The overwhelming majority of breeding is done by private industry with the use of pesticides and for corn and soybeans with transgenic technology (Baenziger et al. 2006; Egli 2008; Gepts and Hancock 2006; Heisey et al. 2001). Pest management challenges specific to organic production are not addressed in these breeding protocols (Ceccarelli 1994; Lammert et al. 1998; Van Bueren et al. 2002). Furthermore, Southeastern producers do not receive much industry attention in the development of crop varieties because of their smaller market as compared to the Midwestern grain market. The industrial variety development model is moving toward fewer varieties for larger regions (Heisey et al. 2001). Organic producers are often pressured to use varieties inappropriate for the Southeastern climate or pest populations because of limited seed options permitted under organic certification guidelines. Climate change could exacerbate this problem as Midwestern climates and Southeastern climates diverge further (Alexandrov and Hoogenboom 2000). As public breeding efforts continue to shrink while private breeding and use of patented genes expands (Stuber and Hancock 2008; Gepts and Hancock 2006), available germplasm for organic producers or even non-GMO producers is limited and often outdated. The looming crisis to agriculture posed by endangered public crop breeding programs is aggravated by the transformation of applied breeding programs at many universities into genetic research programs (Knight 2002) as breeding has become dominated by private companies. There is a great need to expand public breeding programs to address regional needs of non-GMO and organic producers in the Southeast (Heisey et al. 2001). Reducing tillage on organic farms Generally, soils in organic production have shown an increase in organic matter, water infiltration rates, water holding capacity, carbon sequestration and sheer resistance (Marriott and Wander 2006; Venterea et al. 2006; Colla et al. 2000). However, organic grain production requires more tillage than conventional production because weed control is achieved by cultivation rather than herbicide use. Organic corn and soybeans are typically cultivated 6 to 10 times during the growing season, presenting concerns over soil conservation. A new, innovative approach to organic grain production developed by the Rodale Institute (in southeast Pennsylvania) shows considerable promise for weed control without tillage, dramatically reducing soil erosion concerns associated with North Carolina's expanding organic grains industry. The "roll kill/no-till" approach involves planting a cover crop before a grain crop (a small grain before soybeans or a legume before corn) and roll-killing the cover with a heavy roller with crimping blades attached to the roller in a chevron pattern. The roller crimps and lays down the cover crop when the crop is at full bloom, effectively killing the cover crop. The row crop is no-till planted directly into the rolled down cover crop. Weeds are smothered by the cover crop mulch, eliminating the need for cultivation. Research on the roll kill/no-till approach in the Southeast is critical to enabling effective producer adoption in this region. Key issues to address include: 1) evaluation of species and cultivars of cover crop that match the region's planting dates. The flowering of the cover crop must coincide with planting dates for each crop because the roller will not kill the cover crop if it is rolled before flowering; waiting too late will allow the cover crop to set seed, 2) modification of the no-till planter to deal with the amount of cover crop mulch that can be grown in the Southeast. Growing conditions are more favorable here for winter cover crops and the amount of mulch can often exceed 9,000kg ha-1, and 3), evaluation of options for controlling weeds if any break through the mulch layer. While this has not been a concern in the Northeast, mulches decompose faster here due to the increased heat and humidity. Lack of post emergent weed control options has been the largest barrier to adoption of roll kill/no-till systems here. Alternative Crops CanolaAnother crop organic farmers are increasingly interested in is canola. Organic farmers are interested in canola partly because of the potential for canola to be a fumigant crop before high value crops like tobacco or sweet potatoes. Organic canola oil is sought after in NC as an additive to organic layer feed by Braswell Milling (Nashville, NC). They use 1 ton per month in their ration and would be willing to buy the oil in-state, if it was available from NC farmers. Canola meal is also sought after for use in dairy rations, and with a regular supply in the state, the 7 Organic Valley Coop dairies would be willing to cooperatively buy meal. AgStrong, a crusher in northeast Georgia, is offering contracts to North Carolina farmers that appear more profitable than organic wheat. Because most canola production is in mid and western Canada and the northern U.S., where it easily cross-pollinates with GM canola, it is rendered unusable for organic agriculture. Therefore, organic canola meal and oil is difficult to come by as a feed stuff. In the eastern U.S., however, little to no canola is grown, so organic purity is easy to achieve. Like wheat, canola should take relatively little management in comparison to organic soybeans and corn. No post-plant cultivation for weeds is needed. The ease of these winter crops makes them more environmentally sustainable as there is less soil disturbance than with other grain crops, tobacco, or vegetable production. Equipment for planting and harvesting canola is the same as for wheat. Farmers would not need any new equipment to produce this crop if they have been growing wheat, and nearly all organic tobacco and grain farms in NC have been growing wheat. Stevia The need for high-value replacement crops for current and former tobacco producers has been an ongoing concern. We propose to investigate the feasibility for the introduction and development of best management practices for the high intensity sweetener stevia. Stevia is a plant of the Asteraceae (sunflower) family whose leaves have been used as a sweetener in South America for hundreds of years. Stevia extracts are the first all-natural, zero calorie, high intensity sweetener providing: zero calories, low Glycemic index, heat stable, pH stable, shelf stable, non GMO, Kosher and Halal and cost competitive on a sucrose equivalency sweetening unit. The US is the largest single market for high purity stevia extracts, with consumption of approximately 65% of the global market. Importantly, stevia extracts also have been accepted in the European Union as a food and beverage ingredient, which will further expand the global market for stevia extracts over the next three to five years.

Project Methods
Plant Breeding for Organic Systems Farmers have identified multiple breeding targets specific to organic systems including: Develop double cross corn hybrids to allow for easier production of organic corn seed. Single cross hybrids are more expensive to produce organically. Increase the ability of wheat to compete with Italian ryegrass, the predominant weed in the region. Select for resistance to seedling diseases in peanuts where decades of seed treatment use have allowed genetic drift away from resistant types. Find soybean lines with rapidly expanding canopies to allow better early season competition with weeds. Create corn hybrids that are incompatible with GMO varieties to avoid cross contamination issues. In conjunction with plant breeders in each of these commodities, we are developing new cultivars and testing already developed cultivars under organic conditions. Reducing Tillage We will establish three research sites at research stations in distinct geographic regions of the state. We will roll cover crops and plant corn and soybeans at the appropriate time for each region. Some of the legume cultivars will not have flowered yet while others will. We will evaluate the cover crop stands, effectiveness of roll-killing the cover crop, and the cover they provide as mulch to the grain crop. Farmers attending field days will be able to see the effect of these differences in flowering time on how well the cover crop is killed. For between row weeds, the most cost effective option is a new design in high residue cultivators. Flat knives on this equipment cut just beneath the soil surface to kill weeds without disturbing surface residue. We will evaluate the efficacy and cost effectiveness of this supplemental weed control method, as well as how often it is required. We will also measure environmental impacts on soil quality. Water infiltration, water holding capacity, bulk density, carbon sequestration, and soil aggregate stability will be measured at the end of the season on plots in the roll kill/no-till system and compared to soils treated with the standard routine of intensive tillage. A comparison set of monitoring plots will also be established on nearby land managed with continuous no-till for at least 10 years. Two of our three farmers manage their non-organic land in continuous no-till and the third farmer has no-till nearby. We will find fields within the same soil series to serve as comparisons. Alternative Crops Canola North Carolina has very little experience with this crop under conventional conditions, and no experience organically. We have, however an excellent opportunity with a local crusher offering organic contracts. AgStrong, in northeast Georgia, is offering North Carolina growers contracts that appear highly profitable assuming we can produce reasonable yields here. The first research issues were established by a meeting between farmers and buyers and the following experimental protocol was laid out: Seeding Rates: 3,6,9,12 seeds per square foot Row Spacing: 6.7", 13.3", 26.7" Nitrogen: 40 lbs/ac N in fall, 120 lbs/ac N and 40 lbs/ac sulfur in early spring Cultivation: between row sweep cultivator 1 to 2 times on 26.7" row spacing Mulitple locations and years of this experiment will establish expected yield for organic farmers and give them basic guidance on production practices. Stevia We are exploring multiple means of producing this crop both conventionally and organically given the market demand for both. The following study design will be employed: Four weed control strategies. Two will be herbicide based and two will be organic. Three disease management strategies: a) no treatment check, b) scout and spray with organic fungicides if needed, and c) scout and spray with conventional fungicides if needed 2 harvest schedules: 1 vs. 2 harvests 4 replications = Total of 96 plots Planting and Plot size Transplants will be planted flat, in 30" rows at 39,000 plants per acre. Fertility 2.5 tons of chicken litter preplant, another 2.5 tons in early June and another 2.5 tons in mid-August. Harvesting Late June and mid-September vs. mid-September only. Expected Outcomes and Grant's Effectiveness Evaluated: Development of production methods for stevia in NC will generate interest in the crop and market. Organic and conventional farmers in the state will use this information to produce stevia. They will include stevia in crop rotation with tobacco or other crops, and value per acre is potentially high compared to most rotation crops. We expect up to 10 tobacco growers will plant this crop in 2013, and the market will attract at least 200 acres, with the goal of 400 acres, of production by 2014. Effectiveness of this project will be judged by how many growers adopt production as well as how well satisfied they are with production information coming from this project. Impacts on farmers, workers, NC economy, Natural Resources, etc. Stevia is a new and alternative specialty crop for this region. Information from this project will allow farmers to successfully produce and manage the crop. Farmers who chose to grow Stevia will have a ready market for the product in the state, with potentially high profit margins. If successful, this project will improve NC farm business and promote agricultural industry in the state. Tobacco rotations can be improved by adding Stevia. A perennial crop improves soil quality, fertility, and weed management in subsequent years. It also helps prevent erosion, and its use is favorable for certification and natural resource conservation.

Progress 11/05/13 to 09/30/18

Outputs
Target Audience:Organic farmers in North Carolina and in similary systems nationwide and the extension agents that work with them. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?A winter conference and summer field day has been offered to organic farmers and extension professionals every year. Each event draws 150-200 people. Agent only training is provided to extension at annual in-service training events. How have the results been disseminated to communities of interest?Website: https://organiccommodities.ces.ncsu.edu/ Organic commodities production guide available as hardcopy: https://content.ces.ncsu.edu/north-carolina-organic-commodities-production-guide What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Plant Breeding for Organic Corn NC State began a collaboration with the University of Guadalajara to identify new sources of Dominant Gametophytic Factors (DGF's). That collaboration has been highly successful and has resulted in our ability to provide new source of pollen blockage to breeders around the country. Our aggressive shipment of these seeds to other public breeders and publication of the new DGF's was done to prevent patenting of these genes at the request of our University of Guadalajara colleagues(Jones et al. 2016). Soybeans We have developed protocols to screen soybeans for competitiveness with weeds. Multiple methods of measuring soybean canopies were tested to predict their competitive ability.Directly measuring competitive ability, as done in this study, is extremely expensive as it involves growing the crop in competition with weeds and then separating crop and weed biomass to assess the outcome. Fortunately, one of the techniques, overhead image analysis of the soybean canopy combined with pixel counting software, was sufficiently predictive to allow it to serve as an indirect measure of competitive ability. We utilized this approach to screen 45 entries chosen to represent as wide a range in growth patterns as possible. Heritable variation in competitive ability is present in soybean and we have used these results to screen germplasm from the national soybean collection and our advanced lines from the USDA NC soybean breeding program. Wheat Research was initiated to: a) identify protocols for screening wheat genotypes for competitiveness with ryegrass in field trials and b) to evaluate genetic diversity in eastern US wheat varieties for allelopathic activity against ryegrass (Wu et al. 2001). Allelopathic wheat lines exude chemicals from their roots that prevent the germination and growth of weeds (Lemerle et al. 2001). Wheat to rye biomass ratio prior to harvest was correlated with various visual, spectral signal and overhead photography measurements taken during the growing season. The number of ryegrass heads per square meter was highly correlated with biomass ratio and early growth pattern during the October to March period influenced ryegrass growth (Worthington et al. 2013) We trialed 60 cultivars and advanced lines two years in a row to screen for ryegrass suppression. The best genotype from that experiment (Featherstone VA258) suppressed ryegrass by 44% (Worthington et al. 2015). Considering the minimal cost to farmer of switching varieties, this additional tool in the fight against ryegrass can be instantly adopted by growers. We have continued to refine exactly what traits make the most competitive wheat. Molecular marker searches have revealed that day length sensitivity genes are the most correlated, more evidence that early to elongate in the spring varieties with a highly erect habit are the most competitive. Selection for these traits is possible while still maintaining a medium maturity wheat that will not risk late frosts. Alternative Crops Canola Low seeding rates provided the highest yields in the 26.7 inch row spacing. Disease pressure and intra-row competition are both possible explanations for yield declines experienced at the higher seeding rates in the wider row spacing. In the 13.3 inch row spacing, yields were also higher with the lower seeding rates. As with the 26.7 inch row spacing, disease pressure and intra-row competition could be possible explanations for yield declines at the higher seeding rates. At the majority of the locations, the highest yields were obtained with the 6.7 inch row spacing at the highest seeding rate (15 lbs/acre). 9 lbs/acre also yielded very well at the 6.7 in row spacing. Weed coverage was lowest in the 26.7 inch row spacing's receiving between row cultivations. At many locations early spring weeds, reaching up to 90% weed coverage in some locations, ended up naturally dying out and not proving to be a large issue for harvest. Fields which have previously been planted with a vetch cover crop should be avoided for canola growth because vetch can become a serious problem for canola harvest. At Salisbury, a high yielding location, some lodging occurred across all row spacing's beginning at seeding rates of 9 lbs/acre. Reducing Tillage To be able to determine which cover crops work well in the Southeast and compliment the planting schedule for corn and soybean, we planted 20 varieties of rye and legume cover crops at 7 locations from the NC Piedmont to the Tidewater region. We planted 14 legume cover crop varieties, including berseem clover, subterranean clover, sweet clover, crimson clover, hairy vetch, common vetch, winter pea and blue lupine, and we planted 6 varieties of rye. Cover crop stands were evaluated, and all the legume cover crops were rolled on two to three different dates from early April to early May in order to see how rolling and planting match up with full-bloom for cover crop kill. Only the crimson clover varieties and two hairy vetch varieties were killed during the 2nd and 3rd roll dates. Corn was no-till planted into the rolled legume cover crops. Corn yielded an average of 128 bu/acre under the hairy vetch cover crop, and 69 bu/acre under the crimson clover cover crop. The six varieties of rye were rolled on 2 roll dates (mid-May and late-May). Soybeans (NC Roy, maturity group 6) were immediately planted into the rolled rye. Regardless of roll date, all rye varieties were killed successfully. Soybeans emerged well from the rye mulches, and weeds were slow to break through. Soybean yields in the rolled rye were not significantly different from conventional tilled, weed-free soybeans. Additional weed control methods were trialed at each research station and consisted of organic herbicides (corn gluten meal and clove oil) and high-residue cultivation. The rolled rye mulch alone controlled weeds very well, though at some sites, cultivation or the organic herbicides also performed well. Soybean yields were between 30 and 35 bu/acre under all rye varieties. Greenhouse Gas Emissions in Organic Trace gas emissions: Continuous measurements of nitrous oxide (N2O) emission study were performed in six different farming systems with three replicates at Center for Environmental Farming Systems (CEFS), Goldsboro, NC. These systems include Organic clean-till, Organic reduced-till, Organic long-rotation, Conventional clean-till, Conventional no-till, and Conventional long-rotation. A static gas chamber technique was employed to collect N2O emitted from soils. Gas sampling started right after corn seeds were sowed, and takes place 24-48 hours after every rainfall event greater than 0.5 inch within 24 hours. In general, N2O flux rates tended to be higher in the conventional clean-till system than conventional no-till and organic-reduced till systems, with the N2O emission rate being nearly twice much in the former than in the two systems. Soil carbon and nitrogen dynamics: We analyzed soil samples collected before planting and during the growing season to monitor the soil C and N dynamics, in particular, the labile C and extractable N. In general, organic C, particularly labile C was higher in organic than conventional systems, but extractable N was strongly affected by organic or mineral N inputs, which was closely related to N2O emissions. The duration of each farming practice also affected the dynamics of soil labile C and N and microbes. Soil C dynamics and mycorrhizal fungi: We found that mycorrhizal infection of both corn and soybean roots tended to be lower in organic than conventional soils. However, a greenhouse experiment that assessed mycorrhizal effects on N2O emissions showed that mycorrhizal fungi significantly reduced N2O emissions in organic soils but had no effects in conventional soils with high N inputs, suggesting that infection rate may have underestimated the contribution of mycorrhizal fungi in N retention.

Publications

• Type: Journal Articles Status: Published Year Published: 2015 Citation: Worthington, M., S.C. Reberg-Horton, G. Brown-Guedira, D. Jordan, R. Weisz, and J. P. Murphy. 2015. Morphological Traits Associated with Superior Weed Suppressive Ability of Winter Wheat against Italian Ryegrass. Crop Science 55:50-56
• Type: Journal Articles Status: Published Year Published: 2015 Citation: Worthington, M., S.C. Reberg-Horton, G. Brown-Guedira, D. Jordan, R. Weisz, and J. P. Murphy. 2015. Relative Contributions of Allelopathy and Competitive Traits to the Weed Suppressive Ability of Winter Wheat Lines against Italian Ryegrass. Crop Science 55:57-64.
• Type: Journal Articles Status: Published Year Published: 2016 Citation: Atwell, R.A. and S.C. Reberg-Horton. 2016. Row spacing and seeding rate effects on canola population, weed competition, and yield in winter organic canola production. Agronomy Journal 108:2425-2432.
• Type: Journal Articles Status: Published Year Published: 2018 Citation: Liebman, A.M., J. Grossman, M. Brown, M.S. Wells, S.C. Reberg-Horton, W. Shi. 2018. Legume cover crops and tillage impact nitrogen dynamics in organic corn production. Agronomy Journal 110: 1045-1057
• Type: Journal Articles Status: Published Year Published: 2017 Citation: Vann, R., S. Reberg-Horton, H. Poffenbarger, G. Zinati, J. Moyer and S. Mirsky. 2017. Starter fertilizer for managing cover-crop-based organic corn. Agronomy Journal 109: 2214-2 222.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Wells, M.S., S.C. Reberg-Horton, and S.B. Mirsky. 2014. Cultural strategies for managing weeds and soil moisture in cover crop-based no-till soybean production. Weed Science 62:501-511
• Type: Journal Articles Status: Published Year Published: 2017 Citation: Wells, M.S., S.C. Reberg-Horton, S.B. Mirsky, J.E. Maul, and S. Hu. 2017. In situ validation of fungal N translocation to cereal rye mulches under no-till soybean production. Plant and Soil 410:153-165.
• Type: Journal Articles Status: Published Year Published: 2016 Citation: Wells, M.S., S.C. Reberg-Horton, and S.B. Mirsky. 2016. Planting date impacts on soil water management, plant growth and weeds in cover-crop-based no-till corn production. Agronomy Journal 108:162-170.
• Type: Journal Articles Status: Published Year Published: 2016 Citation: Wells, M.S., C. Brinton, and S.C. Reberg-Horton. 2016. Weed suppression and soybean yield in a no-till cover-crop mulched system as influenced by six rye cultivars. Renewable Agriculture and Food Systems 31:429-440.
• Type: Journal Articles Status: Published Year Published: 2014 Citation: Parr, M., J.M. Grossman, S.C. Reberg-Horton, C. Brinton, and C.R. Crozier. 2014. Roller-crimper termination for legume cover crops in North Carolina: impacts on nutrient availability to a succeeding corn crop. Communications in Soil Science and Plant Analysis 45:1106-1119.
• Type: Journal Articles Status: Published Year Published: 2017 Citation: Wu, K., Chen, D., Tu, C., Qiu, Y., Burkey, K.O., Reberg-Horton, S.C., Peng, S. and Hu, S., 2017. CO2-induced alterations in plant nitrate utilization and root exudation stimulate N2O emissions. Soil Biology and Biochemistry, 106, pp.9-17.
• Type: Journal Articles Status: Published Year Published: 2019 Citation: Qiu, Y., Jiang, Y., Guo, L., Zhang, L., Burkey, K.O., Zobel, R.W., Reberg-Horton, S.C., Shew, H.D. and Hu, S., 2019. Shifts in the Composition and Activities of Denitrifiers Dominate CO2 Stimulation of N2O Emissions. Environmental science & technology, 53(19), pp.11204-11213.
• Type: Journal Articles Status: Published Year Published: 2020 Citation: Xiao, R., Qiu, Y., Tao, J., Zhang, X., Chen, H., Reberg?Horton, S.C., Shi, W., Shew, H.D., Zhang, Y. and Hu, S., 2020. Biological controls over the abundances of terrestrial ammonia oxidizers. Global Ecology and Biogeography, 29(2), pp.384-399.