We have been conducting independent lines of farmer-collaborative research that recently identified promising techniques for reducing hand hoeing costs and decreasing incidences of soil-borne disease in chile pepper (herein “chile”). Specifically, our previous studies have shown that: (1) chile weed densities and hoeing times were reduced by stale seedbeds implemented during the summer prior to chile planting, and (2) soil-borne diseases were less prevalent when a Brassicaceae cover crop (BCC) or mustard seed meal (MSM) was amended to soil. Stale seedbeds, BCC and MSM soil amendments suppress targeted pests by eliminating propagules in soil. Thus, we hypothesize that these techniques can be combined
to produce a single, integrated tactic for improved pest management in chile production. To test this hypothesis, we propose to conduct on-farm studies to determine the effects of stale seedbeds with and without biofumigation (BCC or MSM) on the ecology and economy of
weed and disease control in chile. Field study results will be used in economic analyses that evaluate the costs of stale seedbeds, MSM and BCC relative to the economic gains in subsequent chile production. Budget analyses will be featured in our educational outreach
program that will measure changes in attitude and knowledge on management tactics directed towards pest propagules in soil. As a results of our outreach program, we expect that participants will: 1) understand that soil reservoirs of pest propagules are malleable, 2)
recognize the importance of pest propagule density on pest control outcomes and pest control costs, and 3) appreciate the benefits and limitations of management tactics directed towards reservoirs of pest propagules in soil. As a result of this project, we will develop techniques
that improve the economic viability of chile production operations, and we will teach principles and practices for sustainably depleting soil reservoirs of pest propagules.
The specific research objectives of this project are:
1. Determine the effects of fallow-season stale seedbeds with and without Brassicaceae
biofumigation on chile production factors including incidence of soil-borne disease,
survival of pathogen propagules in soil, weed infestation severity, weed management
requirements, weed seedbank density, and chile yield.
2. Use economic cost-benefit analyses to compare fallow-season stale seedbeds with and
without Brassicaceae biofumigation against conventional practice.
Biofumigation with a Brassicaceae cover crop or mustard seed meal, combined with a fallow-season stale seedbed, decreases survival of soil-borne diseases and reduces weed densities in chile pepper.
Biofumigation with a Brassicaceae cover crop or mustard seed meal, combined with a fallow-season stale seedbed, improves profitability of chile pepper production by decreasing disease-induced yield losses and reducing costs for hand-hoeing.
In 2018, we initiated two replicated field experiments on three farms in southern New Mexico. We also conducted a non-replicated, on-farm field experiment. For all on-farm experiments, farmers contributed to the development of strategies that (1) addressed their specific weed and disease problems, and (2) considered the constraints of their farm operation. Also in 2018, we initiated a series of greenhouse experiments that will guide decisions on procedures for our field studies in spring 2019, and we established a replicated field experiment at a university research farm. The research farm site will (1) provide data that contribute to the understanding of Brassicaceae cover crops and mustard seed meal for chile pepper production, and (2) serve as the focal point for educational activities during a field day in summer 2019.
On-farm, Replicated Experiment 1. Brassicaceae cover crop effects on weeds and disease in chile pepper. A Brassicaceae cover crop (herein abbreviated “BCC”) mixture of Caliente ‘Rojo’ (Brassica juncea cv ‘rojo’) and arugula (Eruca sativa) was seeded at three farms near Columbus, NM (31°47.649’ N, 107°51.483’ W); Deming, NM (32°14.714’ N, 107°51.464’ W); and Hatch, NM (32°35.317’ N, 107°22.008’ W). The nearest two study sites are separated by 52 linear km (32 miles). The BCC was seeded following a sequence of preparatory procedures that included tilling, leveling, and at Deming and Hatch, listing and shaping raised beds. The BCC was seeded at approximately 8 kg ha-1 (7 to 9 lb acre-1) on September 29, 2018 at Deming; November 10, 2018 at Columbus; and October 29, 2018 at Hatch. After seeding, fields were irrigated as needed with subsurface drip.
The BCC is compared against both bare ground and a site-specific cover crop alternative. The three treatments (BCC, bare ground, site-specific alternative) are arranged in a randomized complete block design with three replications. Cover crop alternatives include barley (Hordeum vulgare) at Hatch and Columbus, BCC with wheat (Triticum aestivum) at Deming.
In addition to on-farm study sites, this experiment includes a study site at a university research farm near Las Cruces, NM (NMSU Leyendecker Plant Science Research Center; 32° 12.131′ N, 106° 44.771′ W; herein “Leyendecker”). At this site, BCC and bare ground plots are arranged in a randomized complete block design with three replications. BCC was seeded at Leyendecker on October 11, 2018.
At each site, data on cover crop performance against winter weeds and BCC glucosinolate content will be collected at cover crop termination, which is expected in February 2019. Data on cover crop effects on weed and disease management in chile pepper will be collected during the 2019 chile pepper growing season, which will run from March through October 2019.
On-farm, Replicated Experiment 2. Mustard seed meal effects on weeds and disease in chile pepper. In spring 2019, mustard seed meal (herein abbreviated “MSM”) derived from Brassica juncea ‘Caliente’ will be amended to soil at three farms in southern New Mexico (farms near Columbus, Deming and Hatch, please see “On-farm, Replicated Experiment 1”) and at the university research farm near Las Cruces, NM (i.e., Leyendecker). Following farmer interest in opportunities for MSM applications at different times, this field experiment will evaluate two MSM application times: (1) MSM applied and incorporated 4 weeks before chile pepper seeding, and (2) MSM applications 3 weeks after chile plant emergence. In total, this experiment will feature three treatments (MSM applied 4 weeks before seeding, MSM applied 3 weeks after chile plant emergence, no MSM) arranged in a randomized complete block design with four replications. Response variables will include repeated measurements on chile plant size and photosynthesis, chile population density, weed seedling emergence, time required for hand-hoeing, and disease incidence. We will also determine MSM effects on weed seed survival, soil-borne pathogen survival and chile pepper yield. MSM for this study has been acquired, partitioned and packaged into units that are ready for applications at rates equivalent to 4400 kg ha-1 (3926 lb ac-1).
On-farm, Non-replicated Experiment. A fallow-season stale seedbed was implemented at the farm near Hatch, NM. Unseasonal rain precluded fallow-season stale seedbeds at the farms near Columbus, NM and Deming, NM. The fallow-season stale seedbed was initiated with a sequence of preparatory procedures that included tilling, laser leveling, listing and shaping raised beds into rows. Raised beds were irrigated on September 17, 2018. Weed seedlings were identified to species and counted on October 1, 2018. Weed seedlings were terminated with a broad-spectrum herbicide (glyphosate) on October 9, 2018. On October 29, 2018; cover crops were seeded following procedures described above (please see “On-farm, Replicated Experiment 1”).
Greenhouse experiments. Farmers participating in this study are interested in side-dress applications of MSM during early stages of chile plant development. However, there is little technical guidance for MSM applications after crop emergence (herein “post-emergent applications”). To address this knowledge gap, we initiated a series of greenhouse experiments that will determine the effects of post-emergent applications of MSM on chile plant growth and development. The greenhouse is located at Leyendecker and is set to maintain an air temperature of 24 C (± 3 C) and a photoperiod of 14 hr light and 10 hr dark.
The objective of the first greenhouse experiment was to determine the effects of soil-surface MSM applications (without incorporation) on chile plants at different stages of development. Treatments were factorial combination of MSM rate (0, 2200, and 4400 kg ha-1) and stages of chile plant development (germination, 2-leaf, 4-leaf, and 6-leaf stage). Treatments were arranged on a greenhouse bench in a randomized complete block design with four replications. Experimental units were pots containing field soil (Belen silt loam) and chile seeds buried to the 2-cm depth. Chile plant stage treatments were initiated at different times so that all MSM was applied on one day. Response variables included visual estimates of MSM injury at 7, 14 and 21 days after MSM application, as well as fresh and dry weights of chile plant aboveground biomass at 21 days after MSM application.
The objective of the second greenhouse experiment is to determine if burying MSM protects chile plants from MSM-induced injury. Treatments are factorial combination of MSM rate (0, 2200, and 4400 kg ha-1) and MSM burial (MSM buried, MSM on soil surface). Experimental units are plastic bins with field soil containing a single row of chile plants. Chile plants will be at the 4-leaf stage when MSM is applied. Response variables will be those used in the first greenhouse experiment, as well as repeated measurements of chile plant photosynthesis.
Cost-benefits analysis. Implementation costs for BCC and MSM are being determined with New Mexico State University Crop Enterprise Budgets (http://costsandreturns.nmsu.edu) and in consultation with participating farmers. Chile season hoe times, combined with costs for hand-hoeing (9.50 hr-1, plus taxes), will be used to determine the effects of BCC and MSM on hand-hoeing costs in chile pepper production. BCC and MSM effects on marketable yield will be determined at the conclusion of the 2019 chile growing season. Data on yield, hand-hoeing costs and implementation costs will be integrated to determine if BCC or MSM improves profitability of chile pepper production in 2019.
On-farm, Replicated Experiment 1. Brassicaceae cover crop effects on weeds and disease in chile pepper. BCC establishment differed among study sites. In early December 2018, BCC stands were robust at Deming (106 ± 5 BCC plants m-2, 85 ± s.e. 1.6 % cover) and Leyendecker (241 ± 14 plants m-2, 89 ± s.e. 2.1 % cover), moderately robust at Columbus (85 ± 14 plants m-2, 50 ± 6.7 % cover) and weak at Hatch (85 ± 14 plants m-2, < 5% cover; all data are means ± standard errors). Site-to-site variability in BCC establishment was attributed, in part, to differences in weather that coincided with site-specific planting dates. At Columbus, where BCC was planted on November 10, precipitation shortly after seeding may have inhibited BCC seedling emergence. At Hatch, where BCC was planted on October 29, low temperatures shortly after seeding appears to have hindered growth of BCC seedlings. Although anecdotal, our results suggest that seeding prior to October 15 is necessary for robust BCC stands in southern New Mexico. Further, our results revealed a need for systematic research on the interactions among planting date, weather and BCC establishment in southern New Mexico.
Data on BCC size and glucosinolate content at termination, as well as data on BCC performance against weeds and diseases will be collected in spring and summer 2019.
On-farm, Replicated Experiment 2. Mustard seed meal effects on weeds and disease in chile pepper. Data on MSM effects on weed and disease management in chile pepper will be collected in spring and summer 2019.
On-farm, Non-replicated Experiment. Fallow-season stale seedbeds for reducing weed seedbanks. At the farm near Hatch, the fallow-season stale seedbed successfully reduced seedbanks of weed species that hinder chile pepper production. Most notably, the stale seedbed initiated by irrigation on September 17 caused considerable emergence of black nightshade (Solanum americanum) — a summer annual species that is the primary weed management challenge at this study site. Species-specific plant densities at 22 days after irrigation were as follows (mean ± standard error): black nightshade, 395 ± 31 plants m-2; yellow nutsedge (Cyperus esculentus), 9 ± 2 plants m-2; common lambsquarters (Chenopodium album), 2 ± 1 plants m-2; spurred anoda (Anoda cristata), 1 ± 1 plants m-2; morningglory species (Ipomoea spp.), 1 ± 1 plants m-2; pigweed species (Amaranthus spp.), 1 ± 1 plants m-2; yellow woodsorrel (Oxalis stricta), 1 ± 1 plants m-2. Emerged weeds were terminated prior to flowering. Thus, emerged weeds represent reductions in the potential weed pressure for chile pepper produced in 2019, especially for weed species with annual lifecycles (black nightshade, common lambsquarters, spurred anoda, pigweed and morningglory species, yellow woodsorrel). The farmer was pleased with the initial results of the fallow-season stale seedbed and plans to use the tactic again in the future. This experiment was the farmer’s first experience with fallow-season stale seedbeds.
Greenhouse experiments for developing MSM application procedures. Results from the first greenhouse experiment indicated that chile plants from the 2-leaf to 6-leaf stages were severely injured by MSM applications to the soil surface (Figure-1). Ninety-two percent of the 2-to-6-leaf stage plants were terminated by a post-emergent application of MSM at 4400 kg ha-1. Post-emergent application of MSM at 2200 kg ha-1 killed 67% of chile plants from the 2-leaf to 6-leaf stages.
Severe crop injury from MSM without incorporation was consistent with previous research that determined the biofumigation properties of MSM were attributed to volatile compounds that are toxic to many plant species. With consideration of our forthcoming field experiments, results from the first greenhouse study indicated that farmers making side-dress applications of MSM will need to be cautious because the potential for severe crop injury is high. The second greenhouse study is determining if burying MSM protects chile plants from MSM-induced injury following post-emergent applications. The second greenhouse study is in progress and results are not available at this time.
Changes in awareness and knowledge will be determined at all field day and stakeholder meetings. This will be done with anonymous, written, pre-then-post-tests. Post-tests will also contain questions regarding the probability of implementing or recommending fallow-season stale seedbeds and biofumigation techniques. Pre-then-post-tests will be conducted and reviewed by an extension specialist who has previously utilized these tests. Test format and language will closely follow the “Western Region Sustainable Agriculture Research & Education Program Outreach Survey” provided on the Western SARE website (https://wsaregrants.usu.edu/grants/docs/AppendE.pdf).
Educational & Outreach Activities
Project concepts were presented to farmers and agricultural professionals at the 2018 Sustainable Agriculture Field Day held at the NMSU Leyendecker Plant Science Research Center in June 2018. The presentation included demonstration plots showing mustard seed meal effects on weeds in chile pepper.
The majority of our research will occur in 2019. Because research results are the foundation of our outreach program, most of our outreach activities will occur in 2019 and 2020. Outreach activities scheduled for 2019 include field days for which demonstration plots have already been initiated. In addition, we will develop and distribute print and electronic materials presenting principles and practices of MSM and BCC biofumigation for chile pepper production in New Mexico, and we will give presentations at additional field days and grower group meetings.
Asmita will present research results at the 2019 New Mexico Sustainable Agriculture Conference and prepare abstracts and presentation materials for the annual meetings of the Weed Science Society of American and the Western Society of Weed Science, which will occur in early 2020.
All project cooperators will contribute to the development of manuscripts for submission to refereed journals. Also, all project cooperators will contribute to development, delivery and evaluation of presentations given at stakeholder meetings in early 2020.
- Potential pest-suppressive properties of Brassicaceae cover crops, mustard seed meal soil amendments and fallow-season stale seedbeds.
Research is ongoing and educational activities are in early stages. However, at this time, the three farmers participating in this research have indicated increased knowledge on the potential pest suppressive properties of Brassicaceae cover crops.
In addition, one grower indicated increased knowledge on fallow-season stale seedbeds and intends to adopt this tactic.