Reduced Weed Biomass Research Articles

The impact of seasonal variation on occurrence of Fusarium root rot diseases, fly infestations, weeds, herbicide application and yield

Effects of cultivar, herbicide and sowing date on bean fly, Fusarium root rot, weed and productivity were examined during 2015 and 2016 seasons using a split-split-plot design. Sowing delayed from 10-15 May (mid spring) to 25–30 June (early summer) reduced weed biomass up to 49% (2015) and 78% (2016) at flowering, and 79% at maturity in control plots. Herbicides decreased weed biomass up to 79% (2015) and 63% (2016) for first-date sowings of COS16 and Talash cultivars at maturity compared to control. Late June sowings decreased disease incidence up to 75% at maturity. Late sowings indicated greater fly infestation and shorter bean plants compared to earlier sowings. Low 100-seed weight and yield (kg/ha) of bean cultivars were obtained for early sowings. This research advised late sowing of beans in late spring to minimize Fusarium root rot, herbicide applications and weed threats, and improve 100-seed weight and yield for sustainable production.

Economics of reducing Palmer amaranth seed production in dicamba/glufosinate/glyphosate‐resistant soybean

AbstractIncreased prevalence of glyphosate‐resistant (GR) weeds within agronomic cropping systems has led to the readoption of pre‐emergence (PRE) herbicides and use of multiple herbicide‐resistant soybean [Glycine max (L.) Merr.] cultivars. Herbicide programs were evaluated in the recently commercialized dicamba/glyphosate/glufosinate‐resistant (DGGR) soybean for weed control, reduction of Palmer amaranth (Amaranthus palmeri S. Watson) seed production, crop safety, and economic performance. At 35 days after pre‐emergence herbicides, acetochlor plus dicamba plus metribuzin, acetochlor/fomesafen plus dicamba, dicamba plus flumioxazin, and imazethapyr/pyroxasulfone/saflufenacil provided 80–99% control of velvetleaf (Abutilon theophrasti Medik.), Palmer amaranth, common lambsquarters (Chenopodium album L.), and Poaceae species. Evaluation at 14 days after early postemergence herbicides indicated PRE followed by (fb) POST applications of mixtures of acetochlor, dicamba, glufosinate, and glyphosate provided 80–99% weed control compared with 67–93% control in POST‐only programs. Most herbicide programs provided 83–99% control of grass and broadleaf weeds, with 85–91% weed biomass reductions at 28 days after late‐POST. The PRE fb POST programs reduced Palmer amaranth seed production by 94–99%, whereas POST‐only programs provided 75–83% reduction. In 2020, most programs provided gross profit margins ≥US$1,000 ha−1, with glufosinate fb glufosinate and imazethapyr/pyroxasulfone/saflufenacil fb acetochlor plus glufosinate providing $1,481 and $1,466 ha−1, respectively. Benefit/cost ratios ranged between 0.3 and 3.9 in 2019 due to hail but increased to 2.9–10.9 in 2020. Results of this study support use of PRE herbicides with multiple sites of action in DGGR soybean and indicate that glufosinate can provide POST control of GR Palmer amaranth.

Intercropping with service crops provides multiple services in temperate arable systems: a review

Service crops are crops grown to provide services to other cash crops, rather than for production purposes, with the ultimate aim of improving the environmental and production performances of cropping systems. Service crops can be intercropped with cash crops to facilitate interactions between crops and to optimize the use of the cropping season. Many terms exist to describe these practices, which highlights their diversity. However, this diversity of terms may be a source of confusion. Here, we present an overview of the current uses of intercropped service plants in temperate cropping systems, with the main services they provide and their management. (1) First, we show that a limited range of service crop species, mostly from the Fabaceae family, have been studied to date. This finding suggests that the diversity of species and cultivar resources that can be used as service crops has been poorly explored in the literature. In contrast, the combinations of service and cash crops tested appear wider. We address this diversity by defining synchronous intercropping, living mulch and relay intercropping. (2) Then, we show that intercropped service crops can efficiently reduce weed biomass and pest attacks and improve nitrogen cycling, thereby increasing soil fertility and improving crop nutrition. The intensity of these services is positively associated with service crop biomass, but excessive service crop biomass increases the risk of competition with cash crops. (3) The balance between the services and disservices provided can primarily be interpreted in terms of biomass production of coexisting crops. The resulting effect of service crops on cash crop yield is variable and reflects the integration of the effects of the various individual services, together with possible disservices. (4) The diversity in management methods makes it possible to manage this trade-off and to adapt the system to different conditions with a few tested species.

Hot foam: Evaluation of a new, non-chemical weed control option in perennial crops

Hot foam applications represent a new, smart concept in the field of thermal weed control. The aim of this study was to evaluate the efficacy of hot foam and other weed control methods in two olive groves in southern Greece (Pyrgos and Kalamata). The experiment was laid out in a randomized complete block design (RCBD) with six treatments and three replicates. Treatments were applied in the areas between trees, in the row and included mowing with a disc–flail mower, mulching with pruning residues (2.65 kg m–2), glyphosate (at 1,440 g a.e. ha–1), hot foam (13.33 L m–2), pelargonic acid (at 1,088 g a.i. ha–1; twice), and an untreated control. Two experimental runs were conducted at each site using the same treatment list. Malva parviflora L. and Sinapis arvensis L. were the predominant weeds in Pyrgos, while Urtica urens L., Galium aparine L., and Parietaria officinalis L. dominated in Kalamata. Site–experimental runs and treatments significantly affected NDVI and weed biomass (P–Value ≤ 0.001). Hot foam reduced weed biomass by up to 81, 88, 90, and 96% compared to mulching, mowing, pelargonic acid, and the untreated control, respectively. This treatment also reduced M. parviflora biomass by 75–88 and 92–93% compared to mowing and pelargonic acid, respectively, in Pyrgos and P. officinalis biomass by more than 80% in Kalamata compared to the above treatments. In all site–experimental runs, hot foam and glyphosate resulted in the lowest NDVI and weed biomass. The overall performance of hot foam was comparable to glyphosate, suggesting that this method is an environmentally friendly and effective, alternative method to control weeds in olive groves. Further research is required to optimize the use of hot foam for weed control in more perennial crops and under different soil and climatic conditions.

Comparative Analysis of Rice and Weeds and Their Nutrient Partitioning under Various Establishment Methods and Weed Management Practices in Temperate Environment

A research trial was conducted at Agronomy Farm (SKUAST-K, Wadura, Jammu & Kashmir), during kharif 2017 and 2018 to evaluate nutrient removal in rice under various rice establishment methods and weed control measures. The study comprised of two factors: rice establishment techniques {Transplanting (TPR); Direct seeding (DSR) and System of rice intensification (SRI)} as main plot treatments and weed control measures {Butachlor @ 1500 g a.i ha−1 (B); Penoxsulam @ 22.5 g a.i ha−1 (P); Pyrazosulfuron ethyl + Pretilachlor @ 15 and 600 g a.i ha−1 (PP); Bensulfuron methyl + Pretilachlor @ 60 and 600 g a.i ha−1 (BP); 2 Conoweeding/Hand Weeding (CW/HW); Weed free (WF) and weedy check (WC)} as sub-plot treatments meant to evaluate the best establishment method and weed management practice for rice. Over DSR and transplanted rice, the SRI technique yielded a significant increase in dry biomass accumulation (17.04 and 17.20 t ha−1) and grain (7.92 and 8.17 t ha−1) and straw (9.60 and 10.17 t ha−1) yields. Penoxsulam herbicide significantly showed higher grain and straw yield of 8.19 and 8.28 t ha−1 and 10.13 and 10.44 t ha−1, respectively, than other weed management measures by comparing the means using critical difference. TPR excelled in reducing dry weed biomass more than other established methods. All herbicides considerably reduced dry weed biomass, but Penoxsulam herbicide showed the greatest reduction in dry weed biomass and proved superior against complex weed flora. Weeds showed maximum contribution towards total Biomass under DSR, among rice establishment techniques. In contrast, among different weed control measures, it was maximum in weedy check treatment (Untreated Control) and minimum in penoxsulam treatment. SRI significantly excelled in crop (grain and straw) nutrient uptake compared to the DSR and TPR method, although different crop establishment techniques non-significantly influenced nutrient concentrations. Furthermore, penoxsulam treatment demonstrated higher crop (grain and straw) nutrient uptake among the various weed management measures. However, available soil nutrients were observed among establishment techniques, highest in DSR and lowest in SRI. Moreover, direct-seeded rice excelled SRI and transplanted rice in weed nutrient uptake, and among the different herbicidal treatments, penoxsulam recorded the lowest uptake in weeds. Nutrient budgeting demonstrated that DSR showed the maximum percentage of nutrient removal by weeds, and the minimum ratio was in TPR. In contrast, the lowest rate of nutrients removed via weeds were seen in penoxsulam application under various weed management measures.

Weed suppression in cover crop mixtures under contrasted levels of resource availability

Cover crop (CC) mixtures appear as a promising agroecological tool for weed management. Although CC supress weed growth by competing for resources, their suppressive effect under contrasting levels of soil resource availability remains poorly documented. A two field:year experiment was conducted to investigate the weed suppressive effect of four CC mixtures. They were composed of 2 or 8 species including or not legume species and compared to a bare soil control. The experiment included two levels of irrigation and nitrogen fertilisation at CC sowing. The objectives were to assess (i) weed and CC aboveground biomass response to CC mixtures and resource availability, (ii) the weed suppressive effect of CC mixtures across a gradient of CC biomass and (iii) weed community response to CC mixtures and resource availability. CC and weed biomass were mainly influenced by interactions between CC mixtures and fertilisation and between CC mixtures and irrigation, with contrasted effects between field:years. Nitrogen fertilisation increased biomass of non-legume based CC mixtures but this only resulted into a further reduction of weed biomass of little biological relevance. Legume-based CC mixtures suppressed weeds to a greater extent without nitrogen fertilisation in year 2 but not in year 1, possibly due to contrasted initial soil nitrogen availability (lower in year 2). Weed biomass generally benefited more from irrigation than CC mixtures. Among the 33 weed species recorded, weed communities in each plot were dominated by wheat volunteers, Geranium dissectum, Veronica persica and Echinochloa crus-galli, whose biomass varied depending on the interaction between year, CC mixture and resource availability. Our results revealed that competitive outcomes between CC mixtures and weed species were driven by a complex interaction between resource availability and species traits. Further experiments focusing on plant traits should improve our understanding of weed:CC competitive outcomes under various levels of resource availability.

Mucuna pruriens, Crotalaria juncea, and chickpea (Cicer arietinum) have the potential for improving productivity of banana‐based systems in Eastern Democratic Republic of Congo

AbstractIntercropping banana and shorter annual crops in small holder systems is inevitable despite shade being a limitation. Current production is also limited to the wet seasons. Strategies to exploit the spaces under banana shade and drier seasons are crucial for optimal production of these systems. We determined the performance of two legume cover crops, Mucuna pruriens and Crotalaria juncea, and chickpea (Cicer arietinum), a grain legume, under different banana shade levels and over the wet and dry seasons in eastern Democratic Republic of Congo. Banana and legume monocrops served as controls. Shade reduced weed biomass and legume root nodulation, biomass, and grain yields. Chickpea root nodulation had a lower sensitivity to shade (3–9% reduction) compared with mucuna (30–60%) and crotalaria (31–71%). Legume biomass yield declines varied from 37–83%, 56–93%, and 80–98% for mucuna, crotalaria, and chickpea, respectively. Higher nodulation occurred in the rainy compared with the dry season. Biomass yield declines, albeit low occurred in the dry season for mucuna (15%) and crotalaria (30%). In contrast, chickpea biomass and grain yields increased by 394% and 4487%, respectively, in the dry season. A higher banana vegetative growth occurred in the intercropped plots. Land equivalent ratios of 1.15–1.34 under dense shading for mucuna and crotalaria and 1.10–1.62 for chickpea occurred irrespective of the seasons. These findings suggest that these cover crops and chickpea could be exploited to enhance biomass (for fodder, mulch, or manure) and grain yields under banana shade and over the drier seasons.

Improving upon the interrow hoed cereal system: the effects of crop density and row spacing on intrarow weeds and crop parameters in spring barley

AbstractAutomated guidance systems have advanced precise interrow hoeing in narrowly spaced cereals. Compared with other direct mechanical strategies, hoeing provides superior weed control and improved yields. However, weeds in the uncultivated intrarow zone may survive and compete intensely with the crop, causing yield loss. Therefore, improved intrarow weed management strategies in hoed cereals must be investigated. In spring barley (Hordeum vulgare L.), the effect of crop density was assessed at four levels (200, 300, 400, and 500 plants m−2); interrow spacing at two levels (15 and 20 cm), relevant to the abilities of current automated equipment to hoe between narrowly spaced rows; and weed management treatment at three levels (no additional controls, herbicide, and preemergence tine harrowing). All treatments received interrow hoeing, and a surrogate weed (white mustard, Sinapis alba L.) was sown and monitored throughout experiments. The manipulation of crop density was a reliable method for suppressing the growth of intrarow weeds. As barley density increased from the target 200 to 500 plants m−2, percent reduction in intrarow surrogate and ambient weed biomass (g m−2) increased from 49% to 82% and 53% to 99%, respectively. Increasing crop density caused a decrease in grain bulk density (kg hl−1) both years, and grain protein (%) and 1,000-kernel weight (g) in one year; whether these changes constitute a loss in grain quality depends upon end use. While row spacing had no effect on intrarow weeds, crop yields were 7% to 8% lower at 20 cm compared with 15 cm, incentivizing narrow row sowing. Barley yields were unaffected by increasing crop density, and the effect of preemergence tine harrowing was inconsistent. In one year, harrowing reduced surrogate and ambient weed biomass and increased barley yield; however, in another year, ambient weed biomass increased, and harrowing did not affect yield or surrogate weed biomass.

Cereal rye cover crop terminated at crop planting reduces early‐season weed density and biomass in Wisconsin corn–soybean production

AbstractA fall‐established cereal rye (Secale cereale L.) cover crop has potential to provide weed suppression in fields that will be planted with corn (Zea mays L.) and/or soybean [Glycine max (L.) Merr.], reducing the selection pressure for herbicide resistance as part of an integrated weed management approach. However, biomass from an overwintering cover crop can be limited in areas with prolonged cool‐spring growing conditions, like in the Upper Midwest region of the United States. This study was conducted to determine if a cereal rye cover crop grown in Wisconsin and terminated at the time of crop planting could provide effective levels of early‐season weed suppression in corn–soybean systems practicing no‐till soil management. Cover crop biomass, weed biomass, and weed density were assessed at two Wisconsin locations (eight site‐crop‐years total; four site‐years of each corn and soybean) in 2019 and 2020. Cereal rye biomass production at the time of crop planting ranged from 290–1,480 kg ha–1. Overall, no‐till management with a cover crop reduced weed density by 31% and reduced weed biomass by 61% compared with no‐till without a cover crop. These results indicate that the use of a cereal rye cover crop in the Upper Midwest has potential to reduce the exclusive reliance on spring burndown herbicides in no‐till, but limited spring cover crop biomass in this region may diminish the weed‐suppressive effects from this management practice compared with other parts of the United States where higher amounts of cover crop biomass can be achieved at crop planting time.

Evaluation of weed management efficacy of post-emergence herbicides in blackgram under semi-arid Alfisols

The efficacy of a post-emergence herbicides in managing weeds in blackgram was evaluated during summer and rainy (Kharif) seasons of 2016 at University of Agricultural Sciences (UAS), GKVK, Bangalore, India. The experiments were laid in RCBD with three replications comprising of nine treatments. Major weed species observed were: Cyperus rotundus, Eleuisine indica, Dactyloctenium aegyptium, Borreria articularis, Echinochloa colona, Commelina benghalensis, Euphorbia geniculata, Phyllanthus niruri. The post-emergence application (PoE) of sodium acifluorfen 16.5% + clodinafop-propargyl 8% EC (206.25 + 100 g/ha) has attained significantly higher seed and haulm yield of blackgram (1305 and 2088 kg/ha, respectively) in summer 2016 and (1519 and 2253 kg/ha, respectively) in Kharif 2016, followed by sodium acifluorfen 16.5% + clodinafop-propargyl 8% EC (165 + 80 and 123.75 + 60 g/ha) (1192 and 1808 kg/ha, respectively) in summer 2016 and (1425 and 2095 kg/ha, respectively) in Kharif 2016. Similarly the weed control efficiency in summer and kharif 2016 was higher with sodium acifluorfen + clodinafop-propargyl (330 + 160 g/ha) PoE (93.20 and 91.0%, respectively) and it was followed by sodium acifluorfen + clodinafop-propargyl (206.25 + 100 g/ha) PoE (89.51 and 90.24%, respectively) when compared to weedy check. The increased yield was mainly due to a significant reduction in weed density and biomass, without any phytotoxicity to succeeding finger millet crop under semi-arid Alfisols.

Nitrogen and weed management effects on weeds and yield of barley in Kandahar, Afghanistan

Growth and yield of barley (Hordeum vulgare L.) are highly influenced by nutrients and weed management. Nitrogen (N) is the most crucial nutrient to which barley crop responds readily. Efficient management of N and weeds can provide higher yield, better quality, and higher income to the farmers. Therefore, a field experiment was conducted in a split-plot design with three replications during winter season of 2019-20 in the Afghanistan National Agricultural Sciences and Technology University (ANASTU), Kandahar, Afghanistan to evaluate the effect of weed and N management on weeds growth and barley productivity. There were three weed management options in main plots, such as weedy check, herbicide use alone [post-emergence application (PoE) of clodinafop-propargyl 60 g/ha + metsulfuron-methyl 4 g/ha (tank-mix) at 30 days after sowing (DAS)], and integrated weed management (IWM) involving stale seed bed 15 days before sowing + wheat crop residue (2.5 t/ha) retention + clodinafop-propargyl + metsulfuron-methyl (tank-mix) PoE with half of the recommended dose at 30 DAS]. Four N levels (~0, 40, 80 and 120 kg N/ha, i.e., N0, N40, N80 and N120) were included as sub-plot treatments. The IWM led to significantly lower density and biomass of weeds at 40 and 70 DAS and significantly increased weed control efficiency (WCE) and weed control index (WCI). Clodinafop-propargyl (60 g/ ha) + metsulfuron-methyl (4 g/ha) (tank-mix) PoE also resulted in significantly lower density and biomass of weeds and higher WCE and WCI than weedy check at all stages. IWM being at par with clodinafop-propargyl + metsulfuron-methyl (tank-mix) PoE led to higher growth (crop height, dry weight, leaf area index and growth rate) and yield of barley. On the contrary, the effect of nitrogen levels was not significant on the weed density and biomass reduction. N120 and N80 were comparable with respect to growth, yield attributes and yield of barley. Thus, IWM with 80 kg N/ha may be recommended for better weed management and higher barley yield and income in Kandahar, Afghanistan.

Effect of herbicides on weed dynamics and productivity of soybean

A field experiment was conducted at Birsa Agricultural University, Ranchi, Jharkhand, during rainy (Kharif) season of 2019 to study the efficacy of herbicides on weed dynamics and productivity of soybean. The treatments comprised of: post-emergence application (PoE) of imazethapyr 75g/ha at 20 days after sowing (DAS), imazethapyr + imazamox 75 g/ ha PoE 20 DAS, quizalofop-ethyl 50 g/ha PoE 20 DAS, sodium-acifluorfen + clodinafop-propargyl 125 g/ha PoE, imazethapyr + pendimethalin 1.0 kg/ha PoE, hand weeding twice at 20 and 40 DAS, weed free (hand weeding thrice at 20, 40 and 60 DAS), and weedy check. A randomized block design with three replications was used. Quizalofop-ethyl 50 g/ha PoE recorded maximum yield attributes, viz. number of pods /plant (48), number of seeds/pod (2.73), 100 seeds weight (12.46) and yield of soybean (2.15 t/ha) owing to reduced weed biomass and higher weed control efficiency (73.33%) during initial crop growth stage and realized maximum net return (₹ 57221/ha) and B:C ratio (2.34).

Influence of Postemergence Dicamba/Glyphosate Timing and Inclusion of Acetochlor as a Layered Residual on Weed Control and Soybean Yield

Roundup Ready 2 Xtend® [glyphosate- and dicamba-resistant (DR)] soybean is a novel trait option for postemergence (POST) control of herbicide-resistant broadleaf weeds in soybean. With increased use of labeled dicamba products POST in DR soybean and recommendations to include a soil-residual herbicide POST (e.g., layered residual approach), research on how combinations of these approaches influence weed control, weed seed production, and soybean grain yield is warranted. The objective of this research was to evaluate the effects of (1) flumioxazin applied preemergence (PRE) followed by (fb) dicamba plus glyphosate applied POST at different crop developmental stages and (2) acetochlor POST as a layered residual approach on weed control, weed seed production, and soybean yield to determine the optimal POST timing in DR soybean. A field study was conducted in Wisconsin at three sites in 2018 and four sites in 2019 to evaluate flumioxazin (43.4 g ai ha−1, WDG 51%) PRE fb dicamba (560 g ae ha−1, SL) plus glyphosate (1,101 g ae ha−1, SL) POST in DR soybean at three stages: early-POST (EPOST, V1-V2), mid-POST (MPOST, V3-V4), and late-POST (LPOST, V5-V6/R1) with or without a soil-residual herbicide POST (acetochlor, 1,262 g ai ha−1, ME). Weed community composition was site-specific; difficult-to-control broadleaf species included giant ragweed (Ambrosia trifida L.) and waterhemp [Amaranthus tuberculatus (Moq.) J.D. Sauer]. Dicamba plus glyphosate applied MPOST and LPOST provided greater control, weed biomass reduction, and density reduction of giant ragweed and waterhemp when compared with EPOST treatments. Giant ragweed and waterhemp had not reached 100% cumulative emergence at EPOST, and plants that emerged after EPOST produced seed. There was some benefit to including acetochlor as a layered residual at EPOST as indicated by a residual by POST timing interaction for waterhemp density reduction. Complete waterhemp control was not attained at one site-year. For remaining site-years, dicamba plus glyphosate applied MPOST (V3-V4) provided season-long weed control, reduced weed seed production, and optimized soybean grain yield compared with other POST treatments. Results highlight the importance of timely POST applications and suggest utilization of a POST layered residual needs to be timed appropriately for the window of active weed species emergence.

Intercropping red clover with intermediate wheatgrass suppresses weeds without reducing grain yield

AbstractIntermediate wheatgrass (IWG) [Thinopyrum intermedium (Host) Barkworth & Dewey] is the first commercially produced perennial grain crop in the United States. Intercropping legumes with IWG has the potential to enhance dual‐purpose grain and forage production and contribute to weed control in organic management systems. We compared IWG with annual winter wheat (Triticum aestivum L.) in monoculture and intercropped with red clover (Trifolium pratense L.) in a 3‐yr experiment in central New York. Grain yield of IWG was lower than wheat in all years, partly due to lower tiller fertility and seed size in IWG. Compared with grain yield of 1,212 kg ha–1 in the first year, IWG grain yield was 83% (202 kg ha–1) and 64% lower (441 kg ha–1) in the second and third years, respectively. Intermediate wheatgrass straw production increased 40% from 5,541 to 7,785 kg ha–1 over 3 yr while wheat straw yield declined from 5,167 to 3,533 kg ha–1. Red clover did not affect grain or straw yield of either crop but reduced weed biomass and weed species richness. Weed communities in IWG plots were dominated by perennial grasses by the second year of production, whereas annual weeds were dominant in wheat throughout the experiment. Preventing establishment of perennial weeds that will persist in perennial grain cropping systems should be a management priority. High forage production observed when comparing IWG and wheat suggest opportunities for including IWG in integrated crop–livestock systems where IWG's higher forage yield and quality has higher utility.

Weed control for sustaining rice production under dry seeding systems in North-Western India

Identification and adoption of effective weed management practice play a fundamental role for a successful dry-seeded rice (DSR). This field experiment was designed to evaluate the impact of weed control options on weed management, productivity, nutrient uptake, and energetics in DSR. Echinochloa crus-galli (L.) Beauv. was the most dominant species followed by Leptochloa chinensis (L.) Nees. Among the weed control options, sequential applications of pendimethalin (1000 g a.i. ha−1) as pre-emergence and pre-mix combination of penoxsulam (1%) plus cyhalofop-butyl (5%) at 130 g a.i. ha−1 at 25 days after sowing (DAS) led to significant reduction in weed density (82.9%) and biomass (80.1%). This resulted in highest rice grain yield (3.92 t ha−1) and nutrient uptake, resulting in considerably higher energy productivity and lower specific energy. Brown manuring combined with application of metsulfuron methyl (10%) plus chlorimuron ethyl (10%) at 4 g a.i. ha−1 at 40 DAS was also effective in controlling weeds. Based on relative advantages of pendimethalin and penoxsulam plus cyhalofop-butyl in sequence over others, this may be recommended for weed control in DSR.

Cultural Practices and Mechanical Weed Control for the Management of a Low-Diversity Weed Community in Spinach

Low-diversity weed communities are dominated by few species that are highly competitive to crops. The management of such weed communities should rely upon sustainable cultural and non-chemical practices, especially in crops such as spinach (Spinacia oleracea L.), where very few herbicides are available. A two-year field trial (2020 and 2021) was conducted to evaluate different fertilization practices (broadcast and banded), intra-row spacings (15 cm, 11 cm, 7 cm), and mechanical weed control treatments (untreated, one treatment, two treatments) for the management of a low-diversity weed community in spinach. Weed competition severely affected spinach commercial biomass (R2 = 0.845). Compared to broadcast fertilization, banded fertilization reduced weed biomass and improved spinach yield and nitrogen use efficiency. Narrow intra-row spacing (7-cm) reduced weed biomass by 28 and 45% compared to intra-row spacings of 11-cm and 15-cm, respectively. Two mechanical weed control treatments resulted in 49% lower weed biomass compared to a single treatment. Commercial biomass increased with decreasing intra-row spacing (R2 = 0.881) and increasing the number of mechanical treatments (R2 = 0.911). More cultural and non-chemical practices should be evaluated for weed management in spinach, especially at sites infested with low-diversity weed communities.

Can cover crops improve soil ecosystem services in water‐limited environments? A review

AbstractCover crops (CCs) are considered to deliver multiple soil ecosystem services, but such potential could vary by climatic region. This leads to the question: can CCs improve soil ecosystem services in low precipitation regions? To answer this, we reviewed published data up to 27 July 2021 regarding CC impacts on CC biomass production, soil organic C (SOC) accumulation, water and wind erosion, soil water, nitrate leaching potential, soil microbial biomass, weed management, crop yields, and livestock production (i.e., CCs as forage) across regions with <500 mm precipitation. Literature indicates that CCs produce 2.37 ± 2.30 Mg ha−1 of aboveground biomass, but belowground biomass data are unavailable. Cover crops increased soil wet aggregate stability (63% of CC vs. no CC comparisons), suggesting reduced water erosion potential with CCs. Also, CCs reduced nitrate leaching potential (74% of comparisons) and soil water (50%), increased soil microbial biomass (73%), and did not affect dry aggregate stability (67%) and crop yields (56%). Cover crops accumulated SOC in 59% of comparisons. Averaged across all comparisons, CCs accumulated 0.43 Mg SOC ha−1 yr−1 in the upper 30‐cm depth. This SOC accumulation rate is within the range of SOC accumulation across all regions in previous reviews. Cover crops can reduce weed biomass by 89%. Also, when hayed or grazed, CCs could provide net economic returns without negating soil benefits. Overall, CCs improve most soil ecosystem services without many detrimental effects on crop yields in water‐limited environments, although more long‐term (>10 yr) data are needed for definitive conclusions.

Forage legumes exhibit a differential potential to compete against maize and weeds and to restore soil fertility in a maize-forage legume intercrop

ABSTRACT Integrating forage legumes with maize has the potential to restore soil fertility and increase grain yield among smallholder farming systems. A study was conducted over two cropping seasons to determine the effect of intercropping maize with forage legumes on soil fertility restoration, weed biomass and maize yield. Treatments involved: four cropping systems (sole maize, maize-velvet bean, maize-silverleaf, maize-cowpeas) and four fertiliser regimes (no fertiliser, 150 kg ha−1 of compound D fertiliser (7% N: 14% P2O5: 7% K2O) + 150 kg ha−1 ammonium nitrate (34.5% N), 100 kg ha−1 single super phosphate (SSP, 17.5% P2O5) and 200 kg ha−1 SSP). Maize-velvet bean intercropping reduced weed biomass by 80% relative to sole maize and maize-silverleaf intercropping. Maize-cowpea and maize-velvet bean intercropping reduced maize grain yield by 25.9% and 64.7%, respectively, compared to sole maize and maize-silverleaf intercropping. In 2017/2018, maize-silverleaf intercropping increased resin-extractable P2O5 by 60.1% compared to other cropping systems while the three fertiliser treatments increased the levels of this nutrient by 41.9–100%. The results of this study show that intercropping maize with silverleaf has the potential to restore soil fertility and control weeds, without reducing maize grain yield.

Intercropping organic field peas with barley, oats, and mustard improves weed control but has variable effects on grain yield and net returns

Interest in intercropping semi-leafless field peas (Pisum sativum L.) is increasing as a means of weed control in organic production. We evaluated field pea (cv. CDC Amarillo) grown alone or intercropped with three seeding rates of either barley (Hordeum vulgare L.), mustard (Brassica juncea L.), or oat (Avena sativa L.). A full seeding rate of field pea was used in each instance, resulting in an additive intercropping design. Each crop combination was conducted in a separate experiment, three times over two years (2019 and 2020) in Carman, MB. Measurements included crop and weed biomass production, grain yield and quality, and net return. Intercrops reduced weed biomass at maturity from 17% to 44% with barley and oat being more suppressive than mustard. Intercrops also reduced field pea yield from 6% to 26%, but increased field pea seed mass. Barley at the high seeding rate provided the most weed suppression per unit of field pea yield loss (2.62 kg of weed suppression per kg of field pea yield loss) compared with oat (1.29) and mustard (0.87). Barley and mustard intercrops decreased net return compared with monoculture field pea. Under low weed pressure (1150 kg·ha−1 weed biomass at maturity) and earlier seeding, oat intercrops reduced net return. However, under weedy conditions (2649 kg·ha−1) and later seeding, field pea-oat intercrops significantly increased net return. In conclusion, while all three intercrop mixtures reduced weed biomass, reductions in field pea yields were observed, and net return benefits were observed only in certain circumstances.

Cover crop–based, rotational no‐till management tactics influence crop performance in organic transition within the Mid‐Atlantic United States

AbstractReducing the intensityand frequency of tillage in an organic grain system requires an emphasis on utilizing ecological processes to manage pests and fertility. Cover crop–based, organic rotational no‐till (CCORNT) corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] production systems utilize cover crop surface mulch as the primary within‐season weed control tactic. Winter‐sown cereal rye (Secale cereale L.) was grown preceding soybean and hairy vetch (Vicia villosa Roth) mixtures before corn. We conducted a 3‐yr cropping systems experiment in Delaware, Maryland, and Pennsylvania to evaluate crop management (planting date) and integrated weed management (IWM) tactics for CCORNT corn and soybean production in a corn–soybean–winter wheat (Triticum aestivum L.) rotation during the transition to organic. Corn and soybean yields were sensitive to planting date, but optimal planting dates differed among locations. Delayed cover crop termination did not consistently increase total cover crop biomass production or reduce weed biomass levels. High‐residue cultivation reduced total weed biomass across locations, but this IWM tactic produced variable results on cash crop yields. Total weed biomass was negatively correlated to soybean yields but did not influence corn yields. At the Pennsylvania location, delaying corn planting dates was positively correlated with predatory athropod activity‐density, which was positively correlated with corn populations. Assessment of CCORNT practices on short‐term soil health indicators (labile carbon, aggregate stability, entomopathogenic fungi) at the Pennsylvania location produced variable results. Adaptive pest management strategies will need to be used in CCORNT systems within the Mid‐Atlantic United States.