DOI: 10.5061/dryad.vdncjsz8v
title: Data from: Barley cover crops outperform brown mustard for early-season weed control in New Mexico chile pepper

description: Barley (Hordeum vulgare L.) and brown mustard [Brassica juncea (L.)
 Czern.] are winter cover crops known to produce allelochemicals that
 suppress plant growth. Incorporating barley or brown mustard residues into
 the soil before planting a spring-seeded cash crop may suppress
 early-season weeds in the cash crop; however, the comparative levels of
 weed suppression offered by barley and brown mustard cover crops
 incorporated into soil have not been determined. This study analyzed the
 relative capacities of barley and brown mustard cover crops to suppress
 early-season weeds of spring-seeded chile pepper (Capsicum annuum L.).
 Reductions in weed density or hand-hoeing time as a result of barley
 and/or brown mustard cover crop treatment were determined in two chile
 pepper fields in New Mexico over two growing seasons. For cover crop
 species that suppressed weeds in multiple site-years, a controlled
 environment study clarified possible growth stages adversely affected by
 determining the effects of cover crop–amended soil on the germination and
 seedling development of Palmer amaranth (Amaranthus palmeri S. Watson).
 Field study results indicated barley reduced early-season weed densities
 of chile pepper by up to 80 % compared with the noncover control. Barley
 also reduced hoeing time in 3 of 4 site-years without affecting chile
 pepper fruit yield. Mustard cover crops reduced weed density in only 1
 site-year (56 % reduction relative to noncover control) and did not
 decrease hoeing time. The controlled environment study indicated that soil
 amended with barley slowed germination of A. palmeri without inhibiting
 seedling development. The results of this study indicate that a barley
 cover crop is more effective than brown mustard for early-season weed
 control of chile pepper in the southwestern United States.
description: # Data from: Barley cover crops outperform brown mustard for early-season
 weed control in New Mexico chile pepper Dataset DOI:
 [10.5061/dryad.vdncjsz8v](https://doi.org/10.5061/dryad.vdncjsz8v) ##
 Description of the data and file structure The first objective of this
 study was to quantify amounts of aboveground biomass produced by barley
 (*Hordeum vulgare*) and brown mustard (*Brassica juncea*) cover crops
 grown in southern and central New Mexico. The second objective of this
 study was to evaluate barley and brown mustard green manures for their
 effects on weed density, hand-hoeing time, and fruit yield in chile pepper
 (*Capsicum annuum*) seeded after termination of the cover crops. The third
 objective was to determine barley-amended soil effects on germination and
 seedling development of the annual weed, Palmer amaranth (*Amaranthus
 palmeri*). To accomplish Objective 1 and Objective 2, a field study was
 conducted at two sites, with each site including two experimental runs.
 Treatments were arranged in a randomized complete block design with four
 replications. Treatments consisted of barley monocultures, mustard
 monocultures, a barley-mustard combination, and a no cover crop control.
 For each site-year, cover crops were seeded in fall and terminated in
 spring, when chile pepper was subsequently seeded. One day before cover
 crop termination, aboveground cover crop biomass was collected, dried and
 weighed. Cover crops were terminated by mowing. Within 30 to 60 minutes of
 mowing, residues were incorporated into the soil to a depth of 15 cm using
 an offset tandem disc. Then, a lister was used to create raised beds
 approximately 25 cm high and 76 cm wide. Plots were subsequently
 furrow-irrigated to saturate upper soil levels. Three weeks after cover
 crop termination, beds were disked and shaped using a bed shaper,
 approximately 15 % of aboveground cover crop residue remained on the soil
 surface. Chile pepper was seeded using mechanical seeders. Beginning 3
 weeks after sowing chile pepper, weed densities were determined every 2
 weeks for 6 weeks. At each observation time, weeds within two permanently
 established 0.25 m^2^ quadrats in each plot were identified to the species
 level, counted, and removed. Coincident with the second weed-counting
 event, the time required to hand hoe a permanently established 8-m
 transect within each plot was recorded. At the end of the growing season,
 all marketable green fruits were hand harvested along an 8-m transect in
 each plot. Fresh weights of marketable fruits were determined in the field
 and scaled to kg ha ^-1^. To accomplish Objective 3, soil was collected
 from each barley and noncover control plot after mowing and incorporation
 of cover crops, but prior to irrigation. For each site-year, soil samples
 were aggregated within a treatment and homogenized. The effects of
 barley-amended soil on Palmer amaranth germination were determined with a
 three-step process. First, seeds were incubated in soil collected from
 barley or noncover control plots. Next, seeds were removed from soil and
 subjected to germination assays. Finally, time-integrated measures of seed
 germination were determined and compared between the treatments.
 Barley-amended soil was also examined for suppression of Palmer amaranth
 seedling development. This was accomplished by growing Palmer amaranth
 seedlings in barley-amended soil for 28 days and then comparing plant
 heights and growth stages against Palmer amaranth plants grown in soil
 without barley residues.  ### Files and variables #### File:
 AMAPA_seed_germination_data.xlsx **Description:** Spreadsheet contains
 data for Palmer amaranth (*Amaranthus palmeri*, AMAPA) seed germination
 following seed incubation in soil collected from two sites following
 termination of different cover crop treatments. ##### Variables: *
 **Year**: Year in which field soil was collected * **Run**: Experimental
 run, with “1” indicating experimental run one and “2” indicating
 experimental run two. Experimental runs correspond to years in which field
 soil was collected. * **Date**: Day on which germination data were
 collected * **Time**: Time of day in which germination data were collected
 * **Species**: Plant species in study * **Location**: Where cover crops
 were grown and soil collected following cover crop termination.
 “Leyendecker” indicates the New Mexico State University Leyendecker Plant
 Science Research Center. “Los Lunas” indicates the New Mexico State
 University Agricultural Science Center at Los Lunas. * **Treatment**:
 Cover crop treatment, with “Barley” indicating the barley monoculture, and
 “Noncover ”indicating the no cover crop control * **Rep**: Experimental
 replicate * **Germinants**: Number of seeds that completed germination as
 indicated by radicle protrusion through seed coat.  
 
 #### File: AMAPA_seed_germination_data_description.pdf **Description:**
 Companion PDF file for AMAPA_seed_germination_data.xlsx describing the
 content of each column. #### File: AMAPA_seed_viability_data.xlsx
 **Description:** Spreadsheet contains data for Palmer amaranth
 (*Amaranthus palmeri*, AMAPA) seed viability following assays that
 assessed germinability after incubation in soil from different cover crop
 treatments. Cover crops were grown in two sites, two years per site. Soil
 was collected following termination of the cover crops. ##### Variables: *
 **Year**: Year in which field soil was collected * **Run**: Experimental
 run, with “1” indicating experimental run one and “2” indicating
 experimental run two. Experimental runs correspond to years in which field
 soil was collected. * **Species**: Plant species in study * **Location**:
 Where cover crops were grown and soil collected following cover crop
 termination. “Leyendecker” indicates the New Mexico State University
 Leyendecker Plant Science Research Center. “Los Lunas” indicates the New
 Mexico State University Agricultural Science Center at Los Lunas. *
 **Treatment**: Cover crop treatment, with “Barley” indicating the barley
 monoculture, and “Noncover ”indicating the no cover crop control *
 **Rep**: Experimental replicate * **Nongerminated_Total**: Number of seeds
 that did not complete germination in the assay, with completion of
 germination indicated by radicle protrusion. * **Nongerminated_Viable**:
 Number of nongerminated seeds that were viable, with viability determined
 from resistance to applied pressure * **Nongerminated_Nonviable**: Number
 of nongerminated seeds that were not viable. Nonviable seeds collapsed
 under light pressure applied to seed coat. 
 
 #### File: AMAPA_seed_vaibility_data_description.pdf **Description:**
 Companion PDF file for AMAPA_seed_viability_data.xlsx describing the
 content of each column. 
 
 #### File: AMAPA_seedling_development_data.xlsx **Description:**
 Spreadsheet contains data for the development of Palmer amaranth
 (*Amaranthus palmeri*, AMAPA) seedlings grown in soil collected from two
 sites following termination of different cover crop treatments. #####
 Variables: * **Year**: Year in which field soil was collected * **Run**:
 Experimental run, with “1” indicating experimental run one and “2”
 indicating experimental run two. Experimental runs correspond to years in
 which field soil was collected. * **Rep**: Experimental replicate *
 **Location**: Where cover crops were grown and soil collected following
 cover crop termination. “Leyendecker” indicates the New Mexico State
 University Leyendecker Plant Science Research Center. “Los Lunas”
 indicates the New Mexico State University Agricultural Science Center at
 Los Lunas. * **Treatment**: Cover crop treatment, with “Barley” indicating
 the barley monoculture, and “Noncover ”indicating the no cover crop
 control * **Species**: Plant species in study * **Survived**: Plant
 survival through the study period. “Y” indicates plant survival, and “N”
 indicates the plant did not survive to end of the study period. Seedling
 growth assays were twenty eight days in duration. * **Leaf:** Number of
 leaves on an individual plant at the conclusion of the study period. *
 **Height:** Plant height in centimeters at the conclusion of the study
 period. #### #### File: AMAPA_seedling_development_data_description.pdf
 **Description:** Companion PDF file for
 AMAPA_seedling_development_data.xlsx describing the content of each
 column. 
 
 #### File: Cover_crop_biomass_data.xlsx **Description:** Spreadsheet
 contains end-of-season dry weights for mustard and barley cover crops
 grown at two sites in New Mexico, U.S.A. in fall 2021 to spring 2022 and
 fall 2022 to spring 2023.  ##### Variables: * **Location**: Where the
 cover crops were grown, with “Leyendecker” indicating the New Mexico State
 University Leyendecker Plant Science Research Center, and “Los Lunas”
 indicating the New Mexico State University Agricultural Science Center at
 Los Lunas. * **Year**: Year in which cover crop biomass were collected. *
 **Plot_ID**: Plot identification # * **Rep**: Experimental replicate *
 **Treatment**: Cover crop treatment, with “Mustard” indicating the mustard
 monoculture, “Barley” indicating the barley monoculture, “Combo”
 indicating the mustard-barley combination, and “Noncover ”indicating the
 no cover crop control * **Species**: The plant species that was measured,
 with “Mustard” indicating the brown mustard (Barassica juncea) cultivar
 ‘Caliente Rojo’, “Barley” indicating the barley (Hordeum vulgare) cultivar
 ‘Stockford’, and “Noncover ”indicating the no cover crop control. *
 **Weight**: Dry aboveground biomass in units of gram per 0.25 m^2^ 
 
 #### File: Cover_crop_biomass_data_description.pdf **Description:**
 Companion PDF file for Cover_crop_biomass_data.xlsx describing the content
 of each column. 
 
 #### File: Fruit_yield_data.xlsx **Description:** Spreadsheet contains
 fruit yield data for chile pepper grown following different cover crop
 treatments at two sites in New Mexico, U.S.A. in summer 2022 and summer
 2023. ##### Variables: * **Year**: Year in which fruit yield data were
 collected. * **Date**: Day of year on which fruit yield data were
 collected * **Location**: Where the chile pepper was grown, with
 “Leyendecker” indicating the New Mexico State University Leyendecker Plant
 Science Research Center, and “Los Lunas” indicating the New Mexico State
 University Agricultural Science Center at Los Lunas. * **Plot**: Plot
 identification # * **Rep**: Experimental replicate * **Treatment**: Cover
 crop treatment, with “Mustard” indicating the mustard monoculture,
 “Barley” indicating the barley monoculture, “Combo” indicating the
 mustard-barley combination, and “Noncover ”indicating the no cover crop
 control * **Kg_Per_8m**: Fresh weight of chile pepper fruits from 8-m of
 crop row * **Kg_Per_Ha**: Fresh weights of chile pepper fruits from
 experimental plots, scaled to one hectare #### #### File:
 Fruit_yield_data_description.pdf **Description:** Companion PDF file for
 Fruit_yield_data.xlsx describing the content of each column. 
 
 #### File: Hand_hoeing_data.xlsx **Description:** Spreadsheet contains
 hand hoeing data for chile pepper grown following different cover crop
 treatments at two sites in New Mexico, U.S.A. in summer 2022 and summer
 2023.  ##### Variables: * **Year**: Year in which hand hoeing data were
 collected. * **Hoeing**: Sequential hoeing events. Hoeing Event 1 took
 place 48, 36, 26, and 35 days after chile pepper seeding (DAS) for
 Leyendecker 2022, Leyendecker 2023, Los Lunas 2022, and Los Lunas 2023,
 respectively. Hoeing Event 2 took place 60, 50, 40, and 49 DAS for
 Leyendecker 2022, Leyendecker 2023, Los Lunas 2022, and Los Lunas 2023,
 respectively. Hoeing Event 3 occurred 74, 64, 63, and 61 DAS for
 Leyendecker 2022, Leyendecker 2023, Los Lunas 2022, and Los Lunas 2023,
 respectively. * **Location**: Where the chile pepper was grown, with
 “Leyendecker” indicating the New Mexico State University Leyendecker Plant
 Science Research Center, and “Los Lunas” indicating the New Mexico State
 University Agricultural Science Center at Los Lunas. * **Rep**:
 Experimental replicate * **Treatment**: Cover crop treatment, with
 “Mustard” indicating the mustard monoculture, “Barley” indicating the
 barley monoculture, “Combo” indicating the mustard-barley combination, and
 “Noncover ”indicating the no cover crop control * **Plot_ID**: Plot
 identification # * **Minutes**: Number of minutes required for one
 individual to hand hoe an eight meter transect within the plot 
 
 #### File: Hand_hoeing_data_description.pdf **Description:** Companion
 PDF file for Hand_hoeing_data.xlsx describing the content of each column. 
 
 #### File: Weed_density_data.xlsx **Description:** Spreadsheet contains
 weed density data for chile pepper grown following different cover crop
 treatments at two sites in New Mexico, U.S.A. in summer 2022 and summer
 2023.  ##### Variables: * **Year**: Year in which weed density data were
 collected * **Date**: Day on which weed density data were collected *
 **Location**: Where the chile pepper was grown, with “Leyendecker”
 indicating the New Mexico State University Leyendecker Plant Science
 Research Center, and “Los Lunas” indicating the New Mexico State
 University Agricultural Science Center at Los Lunas. * **Rep**:
 Experimental replicate * **Plot_ID**: Plot identification # *
 **Treatment**: Cover crop treatment, with “Mustard” indicating the mustard
 monoculture, “Barley” indicating the barley monoculture, “Combo”
 indicating the mustard-barley combination, and “Noncover ”indicating the
 no cover crop control * **Subplot**: Subplot from which weed density data
 were collected * **Monocots**: Number of monocot weeds per 0.25 m^2^ *
 **Dicots**: Number of dicot weeds per 0.25 m^2^ * **Total**: Total number
 of weeds per 0.25 m^2^ * **Plot_monocots**: Number of monocot weeds
 combined across subplots, resulting in the number of monocot weeds per 0.5
 m^2^ * **Plot_dicots**: Number of dicot weeds combined across subplots,
 resulting in the number of dicot weeds per 0.5 m^2^ * **Plot_total**:
 Total number of weeds combined across subplots, resulting in the total
 number of weeds per 0.5 m^2^ 
 
 #### File: Weed_density_data_description.pdf **Description:** Companion
 PDF file for Weed_density_data.xlsx describing the content of each column.