Final report for SW18-059
This project determined real-world benefits and limitations of false seedbeds and mustard-based techniques for weed control and disease management in chile pepper in New Mexico. We hypothesized that false seedbeds implemented the summer prior to chile pepper seeding (herein “fallow season false seedbeds) can be combined with an overwinter mustard cover crop to produce a single, integrated tactic for improved pest management on commercial chile pepper fields in New Mexico. We also hypothesized that mustard seed meal (MSM) added to soil before or after chile pepper seeding can suppress weeds and soil-borne diseases without harming chile pepper plants. To test the first hypothesis, we measured the performance of mustard cover crops at sites with, and sites without, fallow season stale seedbeds. To test our second hypothesis, we conducted field and greenhouse studies to determine the efficacy and crop safety of MSM amendments made before or after chile seeding. Our results indicated that fallow season false seedbeds may not be compatible with a mustard cover crop because late-summer false seedbeds did not provide sufficient time for growth of the mustard cover crop before frost. This was disappointing because fallow season false seedbeds reduce hoeing requirements in chile, and mustard cover crops are components of pest management strategies for solanaceous crops outside of New Mexico. At sites where mustard cover crops grew successfully, buried-seed tests indicated that mustard cover crops potentially suppressed weeds in chile; however, this weed suppressive potential is not fully realized because of a lack of knowledge on best management practices for terminating a mustard cover crop preceding chile pepper in New Mexico.
Results from the mustard seed meal studies indicated that MSM applications three weeks prior to chile pepper seeding reduced weed densities and hoeing times early in the chile pepper growing season. MSM spread on the soil surface after crop emergence caused irrecoverable injury to chile pepper plants; however, chile pepper plants were not permanently injured, and fruit yield was not reduced, when MSM was incorporated in soil after crop emergence. MSM applications after crop emergence suppressed emergence of Palmer amaranth (Amaranthus palmeri) and growth of Phytophthora capsici, which are common pest problems during the middle and later phases of chile pepper production in New Mexico.
Our educational outreach program included presentations at field days and stakeholder meetings. Total attendance across all outreach events exceeded 1100 people. Farmers and agricultural professionals who completed pre-then-post tests indicated that our presentations promoted understanding of the benefits and limitations of mustard cover crops and MSM amendments for weed and disease management in chile pepper. Personal interactions with farmers indicated enthusiasm for fallow season stale seedbeds, and suggested adoption of this cultural strategy for suppressing weeds in chile pepper.
- Through on-farm research, determine if fallow-season false seedbeds can precede an overwinter mustard cover crop that reduces incidence of soil-borne disease, weed infestation severity, and weed management requirements in chile pepper.
- Develop safe and effective strategies for using mustard seed meal to control weeds and soil-borne diseases in chile pepper.
- Communicate the benefits and limitations of fallow season stale seedbeds, mustard cover crops, and mustard seed meal for weed and disease management in chile pepper.
- (Educator and Researcher)
- (Educator and Researcher)
- A false seedbed implemented the summer prior to chile pepper seeding can be combined with an overwinter mustard cover crop to produce a single, integrated tactic for improved pest management on commercial chile fields in New Mexico.
- Under real-world conditions, a mustard cover crop that is incorporated into soil improves pest management programs for chile pepper by inhibiting weeds and reducing incidence of soil-borne disease.
- Mustard seed meal added to soil before or after chile pepper seeding suppresses weeds and soil-borne diseases without harming chile plants.
To better understand the potential for combining a mustard cover crop with fallow season false seedbeds, we conducted a non-replicated, on-farm field experiment. Unseasonal rain prevented fallow-season false seedbeds at other farms. To study mustard cover crops without fallow season stale seedbeds, we conducted a replicated field experiments at a university research farm and three farms in southern New Mexico. Collaborating farmers contributed to the development of cover crop procedures so that cover crop treatments (1) addressed their specific weed and disease problems, and (2) considered the constraints of their farm operation. To study mustard seed meal amendments for chile pepper, we conducted greenhouse experiments, on-farm experiments, and replicated field experiments at university research farms. Research farm experiments served as focal points for educational activities during university field days in summer 2019 and summer 2021.
Study sites for the project included commercial farms near Columbus, NM; Deming, NM; and Las Uvas, NM. Study sites also included university research farms near Las Cruces, NM (NMSU Leyendecker Plant Science Research Center; herein “Leyendecker”) and Los Lunas, NM (NMSU Agricultural Science Center at Los Lunas, NM; herein “Los Lunas”).
Methods addressing hypothesis 1: a mustard cover crop be grown after a fallow season false seedbed. A fallow-season false seedbed was implemented at the farm near Las Uvas, NM. Unseasonal rain precluded fallow-season false seedbeds at the farms near Columbus, NM and Deming, NM. The fallow-season false 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 for methods addressing hypothesis 2.
Methods addressing hypothesis 2: mustard cover crops suppress weeds and disease in chile pepper. A mustard cover crop mixture of Caliente ‘Rojo’ (Brassica juncea cv ‘rojo’) and arugula (Eruca sativa) was seeded at farms near Columbus, NM; Deming, NM; and Las Uvas, NM. The nearest two study sites were separated by 52 linear km (32 miles). The mustard cover crop was seeded following preparatory procedures that included disking, and at Columbus shaping raised beds. The mustard cover crop was seeded at approximately 8 kg ha-1 (6 to 9 lb acre-1) on September 29, 2018 at Deming; November 10, 2018 at Columbus; and October 29, 2018 at Las Uvas. After seeding, fields were irrigated as needed with subsurface drip.
The mustard cover crop was compared against bare ground, and a site-specific cover crop alternative. The three treatments (mustard cover crop, bare ground, site-specific alternative) were arranged in a randomized complete block design with three replications. Cover crop alternatives included barley (Hordeum vulgare) at Las Uvas and Columbus, mustard with wheat (Triticum aestivum) at Deming.
In addition to on-farm study sites, this experiment included a study site at a university research farm (Leyendecker). At this site, mustard cover crop and bare ground plots were arranged in a randomized complete block design with three replications. The mustard cover crop was seeded at Leyendecker on October 11, 2018.
At each site, data on weed biomass, mustard biomass and mustard glucosinolate content were collected at cover crop termination. Cover crops were terminated on February 22, 2019 at Deming; February 14, 2019 at Columbus; March 5, 2019 at Las Uvas; March 15, 2019 at Leyendecker. Additional data on cover crop effects on weeds and soil-borne diseases were collected during the 2019 chile pepper growing season. Measurements of mustard cover crop effects on weeds included the following three response variables: (1) survival and germinability of Palmer amaranth seeds buried in soil immediately after mustard cover crop termination, (2) repeated measurements of weed density in permanent, rectangular sampling frames, and (3) the time required for one individual to hoe 6-m sections of crop row. Measurements of mustard cover crop effects on soil-borne diseases were determined with repeated measurements of disease incidence in permanent, 10-m transects. Mustard cover crop effects on chile pepper plant vigor were determined with greenhouse assays that used soil collected from fields after incorporation of cover crop residues, but before the irrigation that stimulated degradation of cover crop residues in the field.
Implementation costs for mustard cover crops were determined with New Mexico State University Crop Enterprise Budgets (http://costsandreturns.nmsu.edu) and in consultation with participating farmers. We intended to assess benefits derived from mustard cover crops by considering mustard cover crop effects on hand-hoeing and chile pepper fruit yield. However, results indicated that the mustard cover crop did not affect hand hoeing costs or chile pepper fruit yield.
Methods addressing hypothesis 3: mustard seed meal (MSM) added to soil before or after chile pepper seeding suppresses weeds and soil-borne diseases in chile pepper.
MSM applications before chile pepper seeding. To determine if pre-plant applications of MSM suppress weeds and soil-borne diseases in chile pepper, a field study was conducted at Leyendecker. In spring 2019, a field was prepared for planting by disking, smoothing and laser leveling in February. On March 22, MSM was applied by hand in 1 x 10 m plots. A completely randomized design with four replications was used. Treatments were the following three MSM rates: 0 kg ha-1 (nontreated control), 2200 kg ha-1, and 4400 kg ha-1. The beds were listed immediately following MSM application, which incorporated the MSM into the soil. Listed rows were spaced 1 m apart. After listing, moisture sensors equipped with data loggers were placed in each replication, with sensors buried at the 5-cm and 20-cm depths. Sensors were programmed to simultaneously record soil moisture every 60 min. On the same day as MSM application, the field was irrigated using standard flood furrow irrigation technique.
At 25 days after irrigation, the field was further prepared for the planting of chile. The field was disked again to break clods and then ring-rolled to form the beds for seeding. Chile pepper (cultivar ‘Sandia’) was seeded at 7 kg ha-1 without pre-emergence herbicides or fungicides on April 24, which was 32 days after MSM application. The field was then irrigated seven times and cultivated once before thinning on June 14. The field was then cultivated, irrigated and fertilized using urea ammonium nitrate applied through the irrigation water. The field was irrigated five more times before harvesting on August 29 and again on September 19. Weed seedling counts were taken six times at 14 d intervals in permanent quadrats (0.25 x 1 m) that were positioned on tops of beds. All weed seedlings were identified to species and removed at the time of counting. The time required for one individual to hoe 6-m of row (herein “hand hoeing time”) was determined six times throughout the season. In spring 2020, this study was initiated on a commercial farm near Anthony, NM. However, a work stoppage caused by the COVID-19 pandemic prevented completion the on-farm study on pre-plant applications of MSM.
MSM applications after chile pepper seeding. Farmers participating in this study expressed interest in side-dress applications of MSM during middle phases of the chile pepper growing season. However, prior to this project, there was little technical guidance for MSM applications after crop emergence. To address this knowledge gap, we conducted: 1) a series of greenhouse experiments that determined optimal application methods for post-emergence applications of MSM in chile pepper, and 2) field experiments to evaluate the potential for crop injury and yield loss from post-emergence applications of MSM.
Greenhouse experiments. 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 stage treatments were initiated at different times so that all MSM was applied on the same day. Response variables included chile plant aboveground biomass at 21 days after MSM application.
The objective of the second greenhouse experiment was to determine whether incorporating MSM in soil protects chile plants from MSM-induced injury. Treatments were factorial combination of MSM rate (0, 2200, and 4400 kg ha-1) and MSM location (MSM buried, MSM on soil surface). Experimental units were plastic bins with field soil containing a single row of chile plants. At the time of application, chile plants had 6 to 8 leaves — equivalent to the developmental stage when chile pepper crop is typically thinned. MSM-induced injury was assessed with response variables including repeated measured of chile plant photosynthesis, as well as plant fresh weight, dry weight, height and leaf area at 14 days after MSM application.
Field experiment. This experiment was conducted at collaborator farms near Deming, NM and Las Uvas, NM, as well as university research farms including Leyendecker and the NMSU Agricultural Science Center at Los Lunas, NM (herein “Los Lunas”). At each site, two MSM rates (4400 kg ha-1, 2200 kg ha-1) were each applied to four plots paired with non-treated control plots. At the time of application, chile plants were 36 to 42 cm tall. Based on insights obtained from our greenhouse studies, MSM was applied and incorporated in soil between neighboring chile rows (Figure 1). Immediately following MSM incorporation, all plots were watered by hand with sprinkling canisters. The irrigation volume was 15 L plot-1, which was sufficient to saturate the upper 7 cm of soil.
To ensure that the MSM rates were sufficient for weed control, we measured weed responses to MSM with two response variables: 1) ambient weed emergence from 0.25 m2 quadrats centrally located in study plots, and 2) Palmer amaranth emergence from PVC pipes positioned in study plots after MSM application, but prior to irrigation. Each PVC pipe contained 50 Palmer amaranth seeds buried 1-3 cm from the soil surface. Response variables also included visual assessments of MSM injury to chile at 14 and 28 days after application, as well as chile pepper yield.
Results for hypothesis 1: a mustard cover crop can be grown after a fallow season false seedbed. The fallow-season false seedbed successfully reduced seedbanks of weed species that hinder chile pepper production at the farm near Las Uvas. Most notably, the false 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 weed pressure for chile pepper grown in 2019, especially for resident 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 false seedbed and plans to use the tactic again in the future.
Although the fallow season false seedbed reduced the number of weed seeds in soil, it did not support the mustard cover crop that was seeded after the fallow season stale seedbed. This is known from comparisons of mustard cover crop establishment among study sites. In early December 2018, the mustard cover crop was robust at Deming (106 ± s.e. 5 plants m-2, 85 ± s.e. 1.6 % cover) and Leyendecker (241 ± s.e. 14 plants m-2, 89 ± s.e. 2.1 % cover), moderately robust at Columbus (85 ± s.e. 14 plants m-2, 50 ± s.e. 6.7 %) and weak at Las Uvas (85 ± s.e. 14 plants m-2, < 5% cover). Low biomass for the mustard cover crop at Las Uvas was caused by a frost shortly after seeding. This frost was not entirely unexpected considering the typical time for first frost at Las Uvas (Table 1). Although disappointing, the Las Uvas results indicate the need to seed a mustard cover crop well before the expected first frost. Because mustard cover crop seeding at Las Uvas was delayed by the false seedbed operation, Las Uvas results suggest that false seedbeds implement in late-summer do not provide sufficient time for mustard cover crop seeding.
Results for hypothesis 2: mustard cover crops suppress weeds and disease in chile pepper.
Site-to-site differences in mustard cover crop vigor in December persisted to spring. For three sites (Columbus, Deming and Leyendecker), mustard cover crop aboveground biomass at termination ranged from 463 to 597 g m-2 (Table 1), which was comparable to published reports of mustard biomass in other regions of the United States (Weed Science 53:695-701; Agronomy Journal 108:151–161; Agronomy Journal 107:1235–1249), but less than maximum levels of mustard cover crop biomass reported in the SARE publication “Managing Cover Crops Profitably, 3rd edition” (approximately 900 g m-2). At Columbus, mustard cover crop biomass at termination was greater than the biomass for the site-specific alternative (barley). At Deming, mustard cover crop biomass was equivalent to the biomass of the site-specific alternative (mustard with wheat).
In general, mustard cover crops suppressed winter weeds (Table 1) and contained sinigrin — the primary pesticidal compound in the particular mustard species — at concentrations consistent with previous reports (Table 2). At sites where the mustard cover crop established (Columbus, Deming, Leyendecker), incorporated mustard residues reduced the number of Palmer amaranth seeds in soil (Figure 2). Palmer amaranth seeds that persisted in mustard residue were less germinable than seeds retrieved from soil without the mustard residues, suggesting that mustard residues induced secondary dormancy in Palmer amaranth seeds.
At Columbus, the effects of mustard cover crops on weeds and disease in chile pepper was not determined because all chile pepper plants were intentionally terminated shortly after emergence. Chile pepper plants were terminated because the farmer collaborator determined that the stand was not sufficient for strong yield, which was consistent with statewide reports of relatively few acres of chile in excellent condition (Figure 3). The farmer collaborator did not attribute poor chile pepper performance to a specific cover crop, as demonstrated by the termination of chile pepper across the entire field. Following chile pepper termination, the field at Columbus was seeded in cotton that was managed conventionally. For this cotton crop, early season weeds and soil-borne diseases were not affected by cover crop treatment.
At Deming, cover crop treatment did not affect the following variables in the chile pepper growing season: chile pepper stand density at 3 weeks after emergence; weed densities at 3, 6, and 9 weeks after chile pepper emergence; hoe times at 3, 6, and 9 weeks after chile pepper emergence; disease incidence at 13, 15, and 16 weeks after chile pepper emergence; and chile pepper fruit yield collected at 19 weeks after chile pepper emergence. Similarly, weed densities, hoe times, or disease incidence were not affected by cover crop treatment at Las Uvas.
Although the mustard cover crop did not affect the response variables considered in this study, the mustard cover crop may still have influenced chile pepper production at Deming. The farmer collaborator in Deming indicated that the mustard cover crop likely harbored insects that were damaging to the chile crop. Most notably, the farmer collaborator suspects that beet leafhoppers (Circulifer tenellus) in the mustard cover crop persisted after cover crop termination and transmitted a curtovirus to cause curly top disease in chile. Such an occurrence would be consistent with previous research indicating that Brassicaceae plants in the U.S. Southwest are hosts for both beat leafhoppers and the beet curly top virus (Southwestern Entomologist 28:117-182; Plant Disease 89:480-486). In our study, we were not able to detect mustard cover crop-induced curly top in chile because the viral disease, which is transmitted by leaf hoppers, was prevalent across the entire field and not confined to mustard plots. However, additional data collected supports the farmer’s hypothesis. Specifically, at 16 weeks after chile pepper emergence in the mustard cover crop field, chile pepper stand density (8.6 plants 10-m row-1) was lower and more variable (coefficient of variation, 53.6%) than chile pepper stand density in a nearby field that did not follow a mustard cover crop (16 plants 10-m row-1; coefficient of variation, 13.4%). Further, the farmer collaborator indicated that the chile pepper yield in the mustard cover crop field was 40% lower than nearby chile pepper fields without the mustard cover crop.
Initial economic analyses indicated that the cost of growing and terminating the mustard cover crop ranged from $104 to $158 acre-1. This was considerably more expensive than cover crop production costs presented in the SARE Technical Bulletin “Cover Crop Cover Crop Economics: Opportunities to Improve Your Bottom Line in Row Crops.” In this study, the maximum cost for cover crop production occurred at Columbus where the cost for mustard cover crop termination was $121 acre-1. The high cost for mustard termination at Columbus was caused by the sequence of tillage operations needed to terminate the cover crop on raised beds. At Deming, where the mustard cover crop was not grown on raised beds, the cost for cover crop termination and subsequent soil preparation for chile pepper was $51 acre-1. These results reveal the difficulty in terminating the mustard cover crop on raised beds.
At Leyendecker, the weed community was comprised of Palmer amaranth (Amaranthus palmeri), Wrights groundcherry (Physalis acutafolia), spurred anoda (Anoda cristata), junglerice (Echinochloa colona) and large crabgrass (Digitaria sanguinalis). The mustard cover crop incorporated into soil reduced broadleaf and grass weed densities, as well as hoe times at 3 weeks after chile seeding (Figure 4). The weed suppressive effect of the mustard cover crop was diminished by 6 weeks after chile pepper seeding. Disease incidence data are not reported because there was no occurrence of soil-borne disease in this field.
In the greenhouse, soil with mustard cover crop residues produced larger chile pepper plants than soil without mustard residues (Table 3). This is consistent with a previous study that determined that relative growth rates of onion (Allium cepa) and celery (Apium graveolens) were greater in soils with yellow mustard cover crop residues as compared with soils without mustard cover crop residues (J. Sustain. Agric. 34, 2–14). Chile pepper plants grown in soil without mustard residues exhibited symptoms of wilting diseases (Table 3). This wilting contributed to reductions in chile plant height for chile pepper plants grown in bare ground soils. Wilting of some plants in bare ground soils was likely caused by a soil-borne pathogen; however, laboratory cultures of chile plants with wilt symptoms did not show Verticillium dahliae pathogen.
Results for hypothesis 3: mustard seed meal (MSM) added to soil before or after chile pepper seeding suppresses weeds and soil-borne diseases in chile pepper.
MSM applications before chile pepper seeding.
MSM amendments to the soil reduced weed density and hoe times early in the chile growing season (Figure 5). Weeds at the study site included Palmer amaranth, Wrights groundcherry, spurred anoda, and ground spurge, as well as several grasses that were unidentifiable to the species level at the seedling stage. MSM at 4400 kg ha-1 reduced overall weed seedling emergence by 71% and hand-hoeing time by 35% compared to the untreated control on May 30th. MSM at 4400 kg ha-1 reduced hand-hoeing time on June 19, but MSM effects were not significant on July 18th. There were also no significant differences in yield across treatments which is generally consistent with the literature (Weed Technology 9:669-675).
MSM applications after chile pepper seeding.
Greenhouse experiment. 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. Ninety-two percent of the 2-to-6-leaf stage plants were terminated by MSM at 4400 kg ha-1. 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.
Results from the second greenhouse study indicated that MSM injury on chile was reduced or eliminated by incorporating MSM in soil. Specifically, greenhouse study results indicated that MSM at 4400 kg ha-1 on the soil surface caused lasting reductions in chile plant photosynthesis; but, photosynthetic rates recovered from initial injury when MSM at 4400 kg ha-1 was buried (Figure 6). For MSM at 2200 kg ha-1, surface applications initially reduced photosynthesis, whereas buried applications generally did not affect photosynthetic rates in chile plants. Reductions in photosynthesis caused by MSM on the soil surface resulted in diminished plants at 14 days after application (Figure 7). Together, the greenhouse experiments indicated that burying MSM protects chile plants from damage that can occur from post-emergence applications of MSM. We applied this knowledge to our field study where we evaluated the potential for crop injury and yield loss from post-emergence applications of MSM.
Field experiment. Post-emergence applications of MSM provided varying degrees of weed control, with weed control generally higher for MSM at 4400 kg ha-1 (Table 4) compared to MSM at 2200 kg ha-1 (Table 5). For both rates and at all sites, post-emergence applications of MSM did not cause visual injury and did not reduce chile pepper yield (Table 4, Table 5). These results are promising because (1) this represents one of the first reports of safe, effective application of MSM after crop emergence, (2) if not controlled, weeds that emerge during the middle phases of the chile pepper season severely reduce both yield and harvest efficiency, and (3) farmer collaborators on this project specifically asked for strategies to apply MSM after chile pepper emergence.
Based on the results from our greenhouse and field studies, the following are six general considerations for New Mexico chile pepper farmers attempting to suppress weeds and soil-borne diseases with a mustard cover crop:
- A mustard cover crop mixture of Caliente ‘Rojo’ (Brassica juncea cv ‘rojo’) and arugula (Eruca sativa) can suppress weeds and reduce hoeing requirements in chile pepper. However, this weed suppressive potential might not be fully realized because of a lack of knowledge on best management practices for growing and terminating the mustard cover crop.
- A mustard cover crop should be seeded several weeks before the expected date for first frost. This means that a mustard cover crop may not be compatible with false seedbeds performed in late summer or early fall.
- Previous research determined that mustard cover crops require 410 to 820 g m-2 of dry aboveground biomass at termination to suppress pests through green manuring (Weed Science 45: 439-445). According to this literature-based estimate for biomass requirements, and considering the results of this study, a fall-seeded mustard cover crop in southern New Mexico produces enough biomass for green manuring in spring, provided the mustard cover crop is planted on time to avoid frost shortly after seeding.
- If terminated and incorporated several weeks before chile pepper seeding, an overwinter mustard cover crop can inhibit small seeded summer annual weeds, but not adversely affect chile pepper plants.
- A mustard cover crop on raised beds is difficult and expensive to terminate. Growing a mustard cover crop on flat ground is recommended.
- A mustard cover crop may harbor insects that are damaging to chile pepper. In addition to beet leafhoppers (Circulifer tenellus), mustard cover crops in this study were found to harbor cabbage aphids (Lipaphis spp.) and harlequin bugs (Murgantia histrionica).
False seedbeds implemented the summer before planting are promising techniques for reducing labor requirements for weeding in chile pepper production. To implement false seedbeds for improved weed management in chile pepper, we recommend that farmers:
- Prepare chile pepper seedbeds shortly after harvesting crops in early-to-mid summer. Crops typically harvested in summer in New Mexico include, but are not limited to, barley (Hordeum vulgare), wheat (Triticum aestivum), and onion (Allium cepa).
- After seedbed preparation, irrigate to stimulate weed germination and emergence. Although more information is needed on the relationship between irrigation frequency and false seedbed benefits, previous research suggests that one or two irrigation events are sufficient for reducing hand hoeing costs in chile pepper.
- Terminate newly emerged weeds with shallow tillage.
- If tillage is not preferred, newly emerged weeds can be terminated with herbicides or propane flamers instead of shallow tillage.
Mustard seed meal (MSM) is a biopesticide that simultaneously targets weeds and soil-borne diseases. MSM can be used in conventional and organic cropping systems, although the price for MSM may limit this pest management technique to organic chile production. For chile pepper farmers considering MSM as a tool to reduce weed densities and hand hoeing requirements early in the growing chile pepper growing season, the following three points should be studied:
- This project observed weed control benefits with MSM applied at 1962 lb acre-1 (2200 kg ha-1) and 3925 lb acre-1 (4400 kg ha-1).
- To apply MSM before chile pepper seeding, distribute MSM to flat ground before rows are listed. Then, list to incorporate MSM and irrigate to saturation.
- To avoid injury to young chile pepper plants, pre-plant applications of MSM should be made at least 25 days before chile pepper seeding.
MSM can also be applied after crop emergence. These post-emergence applications of MSM target late-season weeds and soil-borne pathogens. For MSM applications after chile pepper emergence, the MSM should be incorporated into soil that occurs between crop rows. Incorporating MSM into soil minimizes risk of injury to chile pepper plants.
Education and Outreach
Project concepts and results were presented to farmers and agricultural professionals at the following six field days:
- 2018 Sustainable Agriculture Field Day held at the New Mexico State University, Leyendecker Plant Science Research Center (75 attendees).
- 2018 Chile Pepper Field Day held at the New Mexico State University, Agricultural Science Center at Los Lunas (93 attendees)
- 2019 Sustainable Agriculture Field Day held at the New Mexico State University, Fabian Garcia Science Center (55 attendees)
- 2019 Annual Field Day held at the New Mexico State University, Agricultural Science Center at Los Lunas (≈200 attendees)
- 2021 Annual Field Day held at the New Mexico State University, Agricultural Science Center at Los Lunas (214 attendees)
- 2021 Annual Field Day held at the New Mexico State University, Leyendecker Plant Science Research Center (110 attendees)
In addition, project concepts and results were also presented at the following stakeholder meeting:
- 2020 New Mexico Chile Conference (402 attendees)
This project was presented at a public open house hosted by the New Mexico State University, College of Agricultural, Consumer and Environmental Sciences in April 2019. Conclusions from this project will be shared with stakeholders at the 2022 New Mexico Chile Conference.
Most field day presentations included demonstration plots showing weed responses to mustard-based techniques. Field days also featured posters (Figure 8) and handouts (Figure 9). The 2019 Annual Field Day at Los Lunas included a request for additional farmer collaborators. Seven farmers provided contact information and expressed interest in hosting on-farm evaluations of mustard seed meal as a pest management tool for chile pepper. An on-farm evaluation was initiated in spring 2020, but not completed because of work stoppages associated with the COVID-19 pandemic. The presentation at the 2020 New Mexico Chile Conference included a poster that was awarded the best student poster at the conference (Figure 10).
At field days and stakeholder meetings, changes in awareness and knowledge were determined with anonymous, pre-then-post-tests. Post-tests also contained questions regarding the probability of implementing or recommending fallow-season false seedbeds and/or mustard-based techniques for pest control. Unfortunately, few attendees completed pre-then-post-test in entirety. Of all field day events, the 2019 Sustainable Agriculture Field Day provided the most comprehensive evaluation of learning amongst attendees. For the 2019 Sustainable Agriculture Field Day, pre-tests indicated that 68% of attendees had a poor understanding of mustard cover crops, 11% had a good understanding of mustard cover crops and 0% had an excellent understanding of mustard cover crops. After the field day program, 47% had a good understanding of mustard cover crops and 42% had an excellent understanding of mustard cover crops.
Results were shared with the scientific community through an abstract and poster presentation at the 2019 Annual Meeting of the American Society of Agronomy, the Crop Science Society of America, and the Soil Science Society of America (Poster Number 1370; Figure 10). Also, results from this study were presented as papers at the joint annual meeting of the Weed Science Society of American and the Western Society of Weed Science in March 2020 (Abstract 476), and the 2021 Annual Meeting of the Western Society of Weed Science (Abstract 127). The study on MSM applications after chile pepper seeding has been published as an open access, peer-reviewed article in the scientific journal HortScience (https://doi.org/10.21273/HORTSCI15461-20).
Two technical publications were submitted to the New Mexico State University, Agricultural Experiment Station for peer review. Pending acceptance, these technical publications will be available for free and published as peer-reviewed extension articles by New Mexico State University. The two article present the lessons learned from the studies that evaluated false seedbeds combined with mustard cover crops. Currently, the two articles are titled: 1) Mustard cover crops seeded several weeks before first frost produce enough biomass for green manuring in spring, and 2) Observations on technical challenges for overwintering and terminating mustard cover crops in southern New Mexico. Manuscripts were submitted for review on August 24, 2021.
Education and Outreach Outcomes
- Benefits and limitations for using mustard cover crops to suppress weeds and soil-borne diseases that challenge chile pepper production in New Mexico.
- Novel application techniques for using mustard seed meal (MSM) to suppress weeds and soil-borne diseases in New Mexico chile pepper.
- New cultural strategies (fallow season false seedbeds) for suppressing annual weeds in chile pepper production.
Educational activities are ongoing. At this time, farmers have indicated increased knowledge on the limits and potential for Brassicaceae cover crops, mustard seed meal and fallow-season stale seedbeds.
Personal conversations indicated farmer adoption of fallow-season stale seedbeds.
- Chile Pepper Sensitivity to Mustard Seed Meal Applied after Crop Emergence (Peer-reviewed Journal Article)
- Mustard Seed Meal for Weed Control in Chile Pepper (Fact Sheet)