Mustard Cover Crop Research Articles

Brassica juncea pre-season cover crops reduce soybean root colonization by Macrophomina phaseolina, the fungus causing charcoal rot

Macrophomina phaseolina (Tassi) Goid. is a soilborne fungus that causes charcoal rot in numerous crop plants, reducing yield and profits. This study assessed the efficacy of pre-season mustard cover crops (Brassica juncea), a chemical fungicide seed treatment, a combination of both, and a non-treated control in a set of varieties that ranged in maturity. In 2016 and 2017, 'AG4135 RR2Y/SR' consistently yielded lower compared to other varieties. Early maturity varieties exhibited reduced yields relative to mid and late maturity pairs in 2016 and 2017. Root colonization was influenced by treatment, with the combined pre-season cover crop and seed treatment exhibiting the lowest colonization rates in 2015, while all treatments had significantly reduced colonization in 2017 compared to untreated controls. Additionally, differences in root colonization were observed among soybean varieties, suggesting genotype-specific responses to disease management strategies. M. phaseolina soil populations showed a marked increase from pre-cover crop to post-soybean harvest underscoring the pathogen's proliferation throughout the growing season. Correlation analyses revealed significant negative relationships between root colonization and yield for untreated controls, suggesting that higher root colonization adversely affected crop performance. These findings suggest that specific treatments may help mitigate M. phaseolina population build-up in roots and soil and indicate that the effectiveness of control measures may be influenced by pathogen variability in response to environmental conditions and management practices. These findings also contribute to our understanding of effective strategies for managing charcoal rot disease and highlights the importance of integrating chemical and biological control methods.

Timing Termination of a Biofumigant Cover Crop for Weed Suppression in Chile Pepper

Overwinter mustard cover crops incorporated into soil may suppress early-season weeds in chile pepper (Capsicum annuum). However, the potential for mustard cover crops to harbor beet leafhoppers (Circulifer tenellus) is a concern because beet leafhoppers transmit beet curly top virus to chile pepper. The objectives of this study were to determine the amounts of a biopesticidal compound (sinigrin) added to soil from ‘Caliente Rojo’ brown mustard (Brassica juncea) cover crops ended on three different days before beet leafhopper flights during spring and to determine the effects of the cover crop termination date on weed densities and hand-hoeing times for chile pepper. To address these objectives, a field study was conducted in southern New Mexico. In 2019–20, the cover crop was ended and incorporated into soil 45, 31, and 17 days before beet leafhopper flights. In 2020–21, cover crop termination occurred 36, 22, and 8 days before beet leafhopper flights. Treatments also included a no cover crop control. Cover crop biomass and sinigrin concentrations were determined at each termination. Chile pepper was seeded 28 days after the third termination date. Weed densities and hand-hoeing times were determined 28 and 56 days after chile pepper seeding. In 2019–20, the third termination (17 days before beet leafhopper flights) yielded the maximum cover crop biomass (820 g⋅m−2) and greatest sinigrin addition to soil (274 mmol⋅m−2). However, only the second termination (31 days before beet leafhopper flights) suppressed weeds in chile pepper. In 2020–21, the third termination (8 days before beet leafhopper flights) yielded the maximum cover crop biomass (591 g⋅m−2) and greatest sinigrin addition to soil (213 mmol⋅m−2), and it was the only treatment that suppressed weeds. No cover crop treatment reduced hand-hoeing times. These results indicate that overwinter mustard cover crops can be ended to evade beet leafhopper flights and suppress weeds in chile pepper.

Suppression of Phytophthora capsici in Chile Pepper Using Brassica juncea and Hordeum vulgare Cover Crop Residues and Trichoderma harzianum as a Biocontrol Agent.

Phytophthora blight, caused by Phytophthora capsici, is a serious disease of many vegetable crops worldwide. In New Mexico, U.S.A., the disease affects chile pepper (Capsicum annuum L.), a major crop in the state. There is no single tool that effectively controls the disease. Continuous research is needed in identifying combination of tools that can reduce the impact of Phytophthora blight. We explored the potential of combining cover crops and biocontrol agents to reduce soilborne diseases. This study aimed to evaluate the effects of Indian mustard (Brassica juncea L.) cover crop on the antagonistic ability of Trichoderma harzianum against P. capsici in vitro and to quantify the impacts of combining soil amendment with residues from B. juncea and barley (Hordeum vulgare L.) cover crops and plastic covering on infection of chile pepper seedlings by P. capsici under greenhouse conditions. Volatiles from macerated tissue of B. juncea significantly reduced P. capsici and T. harzianum growth in the absence of soil by 89.0 and 79.0%, respectively. When incorporated in soils, volatiles from macerated tissue of B. juncea significantly reduced P. capsici and T. harzianum by 33.4 and 7.8%, respectively. T. harzianum was more resilient to B. juncea biofumigation than P. capsici. Significant reduction in disease incidence was observed with B. juncea-fumigated soil, while no disease suppression was observed with soil incorporation of H. vulgare residues. Covering soil with plastic was necessary for increasing the efficacy of B. juncea biofumigation.

Probiotic Bacteria, Anaerobic Soil Disinfestation, and Mustard Cover Crop Biofumigation Suppress Soilborne Disease and Increase Yield of Strawberry in a Perennial Organic Production System.

Black root rot complex and crown rot of strawberry caused by soilborne fungi limit sustainable strawberry production in the northeastern United States, especially in perennial systems, including matted row and plasticulture. As pathogen populations build up over time in the rhizosphere and infect the root system, feeder roots are pruned, which diminishes nutrient and water uptake and causes stunted plant growth or death. Alternative management options are needed for many organic and small growers who can't use chemical fumigants due to new regulations and potential health hazards. Strawberry plug plants were grown on beneficial microbe-inoculated or uninoculated planting mix followed by transplanting in fruiting field plots that either was biofumigated with mustard cover crop (MCC), anaerobically disinfested (ASD), or left untreated. Different combinations of plug plants and field plot treatments were used to determine the efficacy of individual treatments or synergistic effects from combination treatment. Plug plants were transplanted in pretreated plastic mulched raised beds and grown following a typical organically recommended production system. Plants grown on TerraGrow (TG)-inoculated planting mix showed enhanced plant vigor in the fruiting field compared with untreated plants. Weeds that grew through planting holes were significantly (P ≤ 0.045) suppressed in ASD plots compared with untreated plots in the first year. Plants treated with a combination treatment of TG and ASD had significantly higher fruit yield in both years (2019 and 2020), although the difference was greater in the second year. Plant vigor and survival in treated plots except MCC were also significantly higher in the second year compared with the untreated control. Suppression of pathogenic microbes and plant vigor improvement in treated plots appear to be the factors providing beneficial effects and higher net economic return. Taken together, our results suggest that a combination of beneficial microbes and ASD could be an alternative to synthetic fumigation in a perennial strawberry production system.

Biomass Production of an Overwinter Cover Crop with Biofumigation Properties in New Mexico

Soil-borne diseases and weeds can be inhibited by mustard family (Brassicaceae) cover crops that are mowed and incorporated into the soil with tillage—a process referred to as biofumigation. To determine whether a fall-seeded mustard cover crop produces enough biomass to be a biofumigant in spring, this study measured the amount of biomass produced by a mixture of ‘Caliente Rojo’ brown mustard (Brassica juncea) and ‘Nemat’ arugula (Eruca sativa) grown in three commercial fields and a university research farm in southern New Mexico, USA. This study also determined whether the mustard biomass incorporated in the soil inhibits a weed [Palmer amaranth (Amaranthus palmeri)], but does not affect a cash crop adversely [chile pepper (Capsicum annuum)]. Results indicated that, if the mustard cover crop was seeded before the first frost in fall, mustard cover crops produced biomass in quantities sufficient for biofumigation in spring. Mustard biomass incorporated in the soil reduced the survival and germination of Palmer amaranth seeds. Under greenhouse conditions, chile pepper plants grown in soil with mustard cover crop biomass were larger than chile plants grown in soil without mustard biomass. Chile pepper plants in soil with mustard biomass did not show symptoms of Verticillium wilt (Verticillium dahliae), whereas such symptoms were found on about 33% of chile pepper plants in soil without mustard biomass. These results suggest that a fall-seeded mustard cover crop that is tilled into the soil in early spring is a potential pest management technique for chile pepper in New Mexico.

Effect of mustard cover crops on corn growth, yield and soil water storage in southwest Texas

Mustard cover crops can provide multiple soil health benefits but may adversely affect cash crops by depleting soil water. This was tested in a center-pivot irrigated corn cropping system in southwest Texas from 2018 to 2020. Changes in biomass growth of both the cover crops and corn, and soil water content in the root zone were monitored multiple times during the main growth periods of the crops. Upon termination, biomass production of cover crops averaged 4271 kg/ha, with equivalent nitrogen and phosphorus inputs to the soil of 92 kg/ha and 12 kg/ha, respectively. Over 2 years, water use during the main growth period of the mustard cover crops and the fallow area averaged at 1.4 mm/day and 1.1 mm/day, respectively, and water use of corn following the mustard and fallow averaged at 4.0 mm/day and 3.7 mm/day, respectively, although the differences were only marginally significant. Our data suggest that water use of cover crops was affected by their growth patterns. The mustard cover crops depleted soil water in a dry year (2019–2020), but to a less extent in a wet year (2018–2019). In either year, however, corn yield was not reduced in association with cover crop use, although the improved shoot biomass growth in corn associated with mustard cover crops was observed in the wet year but not in the dry year. Mustard cover crops tended to reduce deep drainage during the corn seasons, which has implications in preventing the leaching loss of nitrogen in the crop root zone.

Soil microbial community characteristics in a vineyard ten years after fumigation

AbstractCalifornia is the number one producer of grapes in the United States. Soil fumigation has been used to control soilborne pests and pathogens. However, fumigants can potentially have a negative impact on native soil microbial populations. Given the roles of microorganisms in the soil system, it is important to assess the long‐term impact of fumigation on soil microbial communities, which is currently lacking. The objective of this research was to study the long‐term impact of microbial communities in grapevine (Vitis vinifera L.) replanting situations after fumigation. Soil treatments included methyl bromide (MeBr), Telone C35, InLine, a nonfumigated control, and a mustard (Sinapis alba L.) cover crop in two side‐by‐side field experiments fumigated in 2007 and 2008. Microbial community biomass in 2017 and 2018 did not differ between fumigated and nonfumigated plots at the 0‐ to 30‐cm depth. However, plots with shank‐injected MeBr and Telone C35 applied in 2008 showed significantly reduced microbial biomass in 2018 at deeper depths than subsurface drip‐applied InLine plots. The results show the impact of fumigation on bacterial communities; however, the impact on fungal and arbuscular mycorrhizal fungi (AMF) communities was not evident after 10 years. Furthermore, the effect of depth was apparent on bacterial communities compared with fungal and AMF communities. The data suggest that deep‐rooted grapevines influenced fungal populations, which probably supplied labile C in fumigated and nonfumigated plots. Future research needs to focus collectively on the long‐term effects of fumigation on fruit quality and yield in vineyards, and on soil microbial communities.

Biocontrol agent, biofumigation, and grafting with resistant rootstock suppress soil-borne disease and improve yield of tomato in West Virginia

Organic tomato growers in West Virginia and neighboring states suffer serious economic losses each year due to soil-borne wilt diseases caused by fungal pathogens including Verticillium dahliae. This study determined the efficacies of biological control agents (BCAs – Serenade SOIL and Prestop), bio-fumigants and transplants grafted to a resistant rootstock in suppressing wilt disease in heirloom tomato cv. Mortgage Lifter in a certified organic production system in West Virginia in two consecutive years. Prestop and Serenade treatments resulted in higher seedling vigor at the early stage. However, within 40 days of field set in the fungal pathogen infested soil, grafted transplants (on resistant rootstock Maxifort) had the highest vigor followed by BCA treatments, biofumigation with mustard cover crop and mustard meal and was lowest in nontreated control. All treatments showed significantly lower Verticillium wilt severity index than control except mustard cover crop and Prestop in 2015 and 2016, respectively. Total fruit harvested over a six-week period indicated that yield from all but mustard cover crop treatment were significantly (P < 0.001) higher compared to the nontreated control in 2015. However, results from 2016 indicated that mustard cover crop would work best for both disease suppression and yield enhancement when tissues were well macerated and incorporated immediately in the soil and covered with impervious plastic for up to 10 days. In 2016, all treatments except Prestop produced higher tomato yield than the nontreated control. In general, yield advantage over nontreated were in the order of grafted > bio-fumigation > BCA treatments > nontreated check. Between two BCAs, Bacillus subtilis (Serenade) consistently provided better disease suppression and improved yield compared with Gliocladium catenulatum (Prestop) in both years. Grafted plants produced 9.1 and 10.0 kg tomatoes/plant in 2015 and 2016, respectively, compared with only 5.0 kg in nontreated control. Our results suggest that grafted transplants, biofumigation and selected BCA should be useful for sustainable management of tomato wilt disease in organic production systems. An economic analysis indicated that grafted tomato can provide the greatest net revenue followed by mustard meal biofumigation in farms infested with wilt causing pathogen.

Sparrow Preferences for Winter Cover Crops in California's Central Coast

Agriculture in many regions of the world has reduced bird habitat and abundance, and altered avian community structure. A study was conducted on an organic research farm over two winters (Oct to Mar) in an intensive agricultural region of Salinas Valley, CA to determine how cover crop variety and planting density influenced birds. Cover crops were rye (Secale cereale), a mixture of rye and legumes (Vicia spp., Pisum sativum), and a mustard mixture (Brassica juncea, Sinapis alba). White-crowned Sparrows (Zonotrichia leucophyrs), Savannah Sparrows (Passerculus sandwichensis) and Song Sparrows (Melospiza melodia) were observed both years in the study field. Bird droppings in cover crops were quantified and dissected to determine dietary preferences, and sparrow movement when flushed was determined. Dropping number and weight per m2 were at least 10 times greater in mustard than in rye and in the legume-rye mixture. Droppings were dominated by leaf tissue in mustard versus arthropod tissue in rye and legume-rye. Within cover crop variety, plant density did not have a clear or consistent effect on sparrows. Sparrows flushed from cover crops usually settled in mustard. The White-crowned Sparrow fed on mustard leaves and apparently on weed foliage under mustard. The arthropod-dominated droppings in rye and legume-rye cover crops were consistent with the food preferences of Song and Savannah Sparrows. The White-crowned Sparrow’s clear preference for mustard cover crops is likely due in part to their high dietary needs for sulfur-rich amino acids during the prenuptual molt. This paper provides novel information to help farmers and others understand the cover crop preferences of sparrows, and ways that farmers might use mustard cover crops as trap crops to reduce White-crowned Sparrow feeding damage on winter and spring vegetable crops. It also provides evidence of ecosystems services that these sparrows provide by feeding on weed tissue in winter cover crops.

Effect of Brassica crop-based biofumigation on soilborne disease suppression in woody ornamentals

Soilborne diseases are the most economically important problem for ornamental nursery producers in the southeastern United States. The use of cover crops selected based on their biofumigant activity to improve soilborne disease management in woody ornamental production was assessed. Replicated pot bioassays were established as greenhouse trials in sterilized clay loam soil which had pre-existing populations of Rhizoctonia solani or Phytophthora nicotianae. Selected Brassica crops were seeded directly into the soil and flowering cover crops were incorporated 15 cm deep into the same pots and covered with polyethylene for 2 or 4 weeks. Volatile compounds released during the biofumigation process were collected at different time intervals. Soil type and moisture affected ITC release. Hydrangea or viburnum rooted cuttings were grown in the biofumigated (2 or 4 weeks) and non-biofumigated control pots and root rot disease severity was evaluated at the end of each bioassay. Yellow mustard (Sinapis alba, ‘White gold’), turnip (Brassica rapa, ‘Purple top forage’), arugula (Eruca vesicaria ssp. sativa, ‘Astro’), Mighty mustard (B. juncea, ‘Pacific gold’), rape (B. napus, ‘Dwarf essex’), mustard green (B. carinata, ‘Amara’) and brown mustard (B. juncea, ‘Kodiak’) cover crops were effective in suppressing R. solani and P. nicotianae. Similar disease suppression was observed whether biofumigation was performed for 2 or 4 weeks. Phytotoxicity was not observed on viburnum and hydrangea woody ornamental plants after either the 2 or 4 weeks biofumigation period with any of the tested cover crops. Viburnum and hydrangea grown in mustard green-, arugula- and turnip-incorporated soil had significantly higher whole plant and root fresh weights compared with the inoculated, non-biofumigated control plants. Although mustard green and arugula are not used currently as commercial biofumigation cover crops, they also showed promise for controlling soilborne pathogens of woody ornamental plants under greenhouse conditions.

Impact of Indian mustard growth and incorporation on annual weed population dynamics and communities

SummaryBiofumigation from Brassica cover crops may be used to control soilborne pests and weeds. A study was conducted to understand the influence of biofumigation on key processes of annual weed population dynamics. Five combinations of Indian mustard (M) and oat (O) cover crop treatments were assessed in a 3 year field study at two locations in Québec, Canada. Treatments included four spring/fall cover crop combinations (M/M, M/O, O/M, O/O) and a weedy check control with no cover crop. Prior to mowing and incorporation of cover crops, weed identification, count and biomass measurements were recorded to evaluate the total weed density, to calculate the relative neighbour effect (RNE) and weed diversity metrics and to perform principal co‐ordinates analyses. Indian mustard cover crops had no impact on weed establishment in 2014 due to low biofumigant potential compared to the oat cover crop. In 2015 and 2016, Indian mustard isothiocyanate (ITC) production increased and weed establishment within the Indian mustard cover crop decreased. Moreover, post‐cover crop incorporation decreased the next year spring weed emergence. Allelopathic interference of Indian mustard was significant when plant tissues produced more than 600 μg of allyl‐ITC g−1. It is now possible to rationalise the use of Brassica cover crops and biofumigation for weed control with an enhanced understanding of the impact of biofumigation on key processes of weed population dynamics.

Controlling Soil-Borne Disease in Soybean With a Mustard Cover Crop

Controlling Soil-Borne Disease in Soybean With a Mustard Cover Crop

Effect of white mustard cover crop residue, soil chemical fumigation and Trichoderma spp. root treatment on black-foot disease control in grapevine.

Black-foot disease is one of the main soilborne fungal diseases affecting grapevine production worldwide. Two field experiments were established to evaluate the effect of white mustard cover crop residue amendment and chemical fumigation with propamocarb + fosetyl-Al combined with Trichoderma spp. root treatment on the viability of black-foot inoculum in soil and fungal infection in grafted plants and grapevine seedlings used as bait plants. A total of 876 black-foot pathogen isolates were collected from grafted plants and grapevine seedlings used as bait plants in both fields. White mustard biofumigation reduced inoculum of Dactylonectria torresensis and the incidence and severity of black-foot of grapevine, but no added benefit was obtained when biofumigation was used with Trichoderma spp. root treatments. The effect of white mustard residues and chemical fumigation on populations of D. torresensis propagules in soil was inconsistent, possibly because of varying pretreatment inoculum levels. Biofumigation with white mustard plants has potential for improving control of black-foot disease in grapevines. This control strategy can reduce soil inoculum levels and protect young plants from infection, providing grape growers and nursery propagators with more tools for developing integrated and sustainable control systems. © 2018 Society of Chemical Industry.

Reduced nitrate leaching from an Irish cropland soil under non-inversion tillage with cover cropping greatly outweighs increased dissolved organic nitrogen leaching

Reduced tillage and cover cropping are common measures to minimize leaching losses of nutrients from cropland soils. While the efficiency of these measures for reducing inorganic N leaching has been studied intensively, their effect on dissolved, organically-bound nitrogen (DON) remains unclear. In this study, leaching of nitrate, ammonium and DON from spring barley-based cropping systems, subject to either conventional management (CT = inversion tillage with a winter fallow period), or non-inversion tillage with a winter mustard cover crop (NIT + CC), were assessed using suction cup sampling and modelled drainage volumes. Total dissolved nitrogen losses with drainage from the NIT + CC treatment (2.5 ± 0.2 g N m−2 yr−1) were considerably smaller than those from the conventional treatment with fallow (13.9 ± 0.7 g N m−2 yr−1). As drainage volumes were similar between treatments, differences in total N leaching were mainly associated with larger nitrate concentrations under CT (23.0 ± 1.1 mg N L−1) than under the NIT + CC treatment (5.1 ± 0.3 mg N L−1). The average contribution of DON to total dissolved nitrogen concentration was 3% within the CT treatment, but rose to 19% within the NIT + CC treatment, which was primarily due to the strong reduction in nitrate and to a lesser extent due to the higher concentrations of DON within the NIT + CC treatment (NIT + CC: 0.52 ± 0.04, CT: 0.33 ± 0.04 mg N L−1). Averaged over the two-year study period, the CT system showed a net loss of 9.4 g N m−2 yr−1 whilst an N surplus of 1.7 g N m−2 yr−1 was observed for the NIT + CC system. Here DON accounted for 11% of total N leaching, supporting the notion that it can be an important component of dissolved N losses in agroecosystems. By neglecting DON leaching the N-surplus under NIT + CC would have been overestimated by 18%. In conclusion, our results show that the capacity of winter cover cropping in combination with non-inversion tillage to reduce nitrate leaching far outweighed the higher leaching losses of DON observed. The quantification of DON losses, however, may be essential for a complete picture of the N balance of these and similar cropping systems.

Mustard Cover Crop Growth and Weed Suppression in Organic, Strawberry Furrows in California

Strawberry (Fragaria ×ananassa Duch.) production in California uses plastic mulch–covered beds that provide many benefits such as moisture conservation and weed control. Unfortunately, the mulch can also cause environmental problems by increasing runoff and soil erosion and reducing groundwater recharge. Planting cover crops in bare furrows between the plastic cover beds can help minimize these problems. Furrow cover cropping was evaluated during two growing seasons in organic strawberries in Salinas, CA, using a mustard (Sinapis alba L.) cover crop planted at two seeding rates (1× and 3×). Mustard was planted in November or December after strawberry transplanting and it resulted in average densities per meter of furrow of 54 and 162 mustard plants for the 1× and 3× rates, respectively. The mustard was mowed in February before it shaded the strawberry plants. Increasing the seeding rate increased mustard shoot biomass and height, and reduced the concentration of P in the mustard shoots. Compared with furrows with no cover crop, cover-cropped furrows reduced weed biomass by 29% and 40% in the 1× and 3× seeding rates, respectively, although weeds still accounted for at least 28% of the furrow biomass in the cover-cropped furrows. These results show that growing mustard cover crops in furrows without irrigating the furrows worked well even during years with relatively minimal precipitation. We conclude that 1) mustard densities of ≈150 plants/m furrow will likely provide the most benefits due to greater biomass production, N scavenging, and weed suppression; 2) mowing was an effective way to kill the mustard; and 3) high seeding rates of mustard alone are insufficient to provide adequate weed suppression in strawberry furrows.

Earthworm populations in twelve cover crop and weed management combinations

Earthworm communities were assessed in twelve agronomic treatment combinations at the cessation of a three year winter cover crop–spring barley main crop in Ireland. Agronomic treatments had statistically significant effects on earthworm abundance and biomass; the above-ground biomass of cover crops species and other weed species was also significantly affected. A pea cover crop supported the largest earthworm communities, 221±55 (±SD) individuals m−2 and live biomass 67.4±12.0gm−2, while having the smallest overall mean yield for cover crop biomass, 56.8±56.7g dry matter m−2. By contrast, a mustard cover crop had the largest overall mean yield for cover crop biomass, 195±82.7gm−2, but earthworm populations similar to those in other cover crops and under natural regeneration. The lowest overall mean earthworm biomass (23.1±1.8gm−2) of all agronomic combinations was recorded in a bare fallow treatment which had no overwinter vegetation. Earthworm species numbers between treatments were similar, with endogeic species such as Allolobophora chlorotica, Aporrectodea caliginosa and A. rosea being dominant. The pea cover crop probably supported the largest earthworm populations due to a high quality food supply. Conversely, brassicaceous cover crops such as mustard, while producing large above-ground biomass, did not support larger earthworm populations, but a biofumigation effect was not evident either. In conclusion, various winter cover crops as well as natural regeneration supported similar earthworm populations after a three year cover crop-spring barley main crop cycle, with some evidence for larger and more species-rich populations under some cover crops such as pea and oat, and somewhat smaller populations where no overwinter vegetation was present.

Mustard Cover Crops for Biomass Production and Weed Suppression in the Great Lakes Region

Short‐season cover cropping can be an important weed management tool. To optimize the use of mustard [Sinapis alba L. and Brassica juncea (L.) Czern.] in the Great Lakes region, we assessed planting time effects, mustard biomass production, and weed suppression during mustard growth and after incorporation. The study was conducted in Illinois, Michigan, and New York for spring and fall from 2010 to 2012. Mustard was sown every ∼10 d from mid‐March to early June for spring plantings and from early August to mid‐September for fall plantings. Spring mustard biomass, weed density, community composition, and dry biomass were collected at mustard flowering. Fall mustard biomass, weed density, and dry biomass were collected at season end. Spring mustard biomass ranged from &lt;0.5 to 4 t ha−1. Early fall biomass ranged from 3 to 5.5 t ha−1, and was related to growing degree days (GDD) according to a logistic function. Weed biomass during mustard growth was reduced by at least 50% in 9 of 10 site‐years (90%) for fall‐planted mustard but only 15 of 31 site‐years (48%) in spring plantings. Weed suppression was independent of mustard biomass. The total number of weed seedlings emerging after mustard incorporation was not significantly reduced, but there was a species‐specific response, with a decrease in common lambsquarters (Chenopodium album L.) and grass emergence. The results permit a location‐specific recommendation to plant mustard cover crops 13 to 23 August in the southern Great Lakes Region, and no later than 1 to 10 September for adequate biomass production.

Effect of cover crops on emergence and growth of carrot (Daucus carota L.) in no-plow and traditional tillage

&lt;p&gt;The aim of the experiment was to determine the influence of cover crop biomass incorporated into the soil at different times and using different treatments on carrot emergence and growth. 7 species of cover crops were included in the study: &lt;em&gt;Secale cereale&lt;/em&gt;, &lt;em&gt;Avena sativa&lt;/em&gt;, &lt;em&gt;Vicia sativa&lt;/em&gt;, &lt;em&gt;Sinapis alba&lt;/em&gt;, &lt;em&gt;Phacelia tanacetifolia&lt;/em&gt;, &lt;em&gt;Fagopyrum esculentum&lt;/em&gt;, and &lt;em&gt;Helianthus annuus&lt;/em&gt;. &lt;/p&gt;&lt;p&gt;Number of emerged carrot plants significantly depended on the cover crop used and on the method of pre-winter and spring pre-sowing tillage. Carrot emerged best after a rye or oats cover crop. Regardless of the cover crop species used, the largest number of carrots emerged in cultivation on ridges. In other variants of no-plow tillage, number of seedlings was significantly lower and did not differ from that under traditional plow tillage. The highest leaf rosettes were formed by carrot growing after a rye or oats cover crop. The highest rosettes were produced by carrots in the treatments where tillage was limited to the use of a tillage implement in spring and the lowest ones after pre-winter plowing. The effect of tillage on the emergence and height of carrot leaves largely depended on weather conditions in the successive years of the study. The largest number of leaves was found in carrots grown after a buckwheat cover crop and in cultivation without cover crop, while the smallest one after phacelia and white mustard. Carrots produced the largest number of leaves after a sunflower cover crop and the use of a tillage implement in spring, while the number of leaves was lowest when the mustard biomass was incorporated into the soil in spring. The use of cover crops significantly increased the mass of leaves produced by carrot as compared to the cultivation without cover crop. The largest mass of leaves was produced by carrots grown after the phacelia and mustard cover crops. Conventional plow tillage and pre-winter tillage using a stubble cultivator promoted an increase in the mass of carrot leaves.&lt;/p&gt;

Integrated Biological and Cultural Practices Can Reduce Crop Rotation Period of Organic Strawberries

A team of researchers conducted a replicated on-farm experiment with the break period between strawberry crops (continuous strawberries with broccoli residue incorporation, one-year break, two-year break, three-year break, and seven-year break) as the main plot and cultivar as the split plot in Moss Landing, Central Coastal California. We hypothesized that the use of non-host rotation crops for Verticillium wilt plus bio-fumigation with broccoli, incorporation of mustard cover crop residues, use of relatively resistant strawberry cultivars, and compost application would suppress disease sufficiently to grow strawberries successfully in rotation every two or three years. Although a positive correlation between break period and marketable fruit yield existed, integrated use of biological and cultural practices allowed one to three-year breaks to have a statistically similar yield as seven-year break for this low Verticillium dahliae pressure field over a five-year period.

Assessing the combined use of reduced tillage and cover crops for mitigating greenhouse gas emissions from arable ecosystem

Field management activities have significant impacts on greenhouse gas (GHG) emissions from cropland soils. In this study, the effectiveness of combining reduced tillage with a mustard cover crop (RT–CC) to mitigate present and future GHG emissions from a fertilized spring barley field in the southeast of Ireland was assessed. The field site which had a free-draining sandy loam soil with low soil moisture holding capacity, had been managed for three years prior to measurements under two different tillage systems; conventional (CT) and RT–CC. Field measurements of soil CO2, N2O and CH4 emissions, crop biomass, water filled pore space (WFPS), soil temperature and soil nitrate were made to capture both steady state conditions as well as the management events. Field data were used to validate the DNDC (DeNitrification–DeComposition) model and future GHG emissions under two sets of climate projections were predicted. Although fertilizer use was the same for both treatments the RT–CC treatment had significantly (p<0.05) higher N2O emissions for both present and future climate. However, the inclusion of a cover crop with the RT treatment increased predicted soil organic carbon (SOC), which more than compensated for the higher N2O flux resulting in a lower total GHG balance (TGGB) compared with the CT treatment. Results show that the effectiveness of RT–CC in mitigating GHG emissions will depend crucially on the magnitude of compensatory increases in carbon dioxide uptake by the cover crop that will contribute to a reduction in the total GHG balance.