High Weed Pressure Research Articles

Soil and weed management effects on floral hemp (Cannabis sativa L.) production and cannabinoid content

AbstractMany floral hemp (Cannabis sativa L.) growers rely on tillage and black plastic mulch to prepare soil for transplants, warm the soil, and control weeds. However, plastic waste and its high cost to growers drive the need for research to assess alternative weed and soil management practices. Experiments were conducted at two Maine locations in 2021 and 2022 to compare cover crop soil and weed management systems on hemp production, cannabinoid concentrations, and yield. Experimental treatments included (1) tilled raised bed‐black plastic mulch, (2) biweekly cultivation, (3) no weed control, and (4) mowed no‐till mowed winter rye (Secale cereale L. Aroostook). Experimental sites received twice the 30‐year monthly average rainfall in July and September 2021 leading to poorer production versus typical 2022 long‐term average rainfall. Ice damage reduced winter rye biomass in 2022 at University of Maine Rogers Farm, leading to several significant year by location and year by weed management interactions. Hemp grown in the no‐till winter rye mulch developed more slowly, produced lower yields, and had higher weed densities than cultivated or black plastic mulch treatments. Plant size, yield, and cannabinoid content were generally equivalent where weeds were controlled. Raised bed‐black plastic soil and weed management were most effective under excessively wet conditions to reduce soil moisture and improve drainage. Cannabinoid concentrations did not increase under high weed pressure, but cannabinoid yield was influenced by flower production, which was significantly lower in the mowed rye mulch and control treatments. Blending raised bed production with efficient cultivation warrants research attention.

A survey of ethofumesate resistant annual bluegrass (Poa annua) on US golf courses

AbstractAnnual bluegrass (Poa annua L.) is the most troublesome weed on golf courses in the US. Many agronomic practices intended to promote high‐quality playing surfaces favor the growth and development of annual bluegrass, resulting in high weed pressure. One commonly used herbicide for annual bluegrass control on golf courses is ethofumesate, which is a very long chain fatty acid inhibitor. Annual bluegrass resistance to this herbicide is documented and confirmed in grass seed production systems, but potential resistance on golf courses was previously unknown. The objective of this study was to determine the frequency and magnitude of potential ethofumesate resistance from a sample of US golf courses. A dose‐response experiment was initiated at Purdue University using 30 annual bluegrass populations collected from Alabama, California, Indiana, and Oregon golf courses. Ten ethofumesate doses included 0, 0.5, 1.0, 2.5, 5.0, 7.5, 10.0, 15.0, 20.0, and 40.0 lb a.i. acre−1, with 1.0 to 2.0 a.i. acre−1 as the standard label application rate for perennial ryegrass turf. A low level of resistance (R/S < 3) was found in several populations collected in each state. The mean effective dose necessary to kill 50% of the populations (ED50) was 5.1, 9.2, 3.5, and 3.4 lb a.i. acre−1 for populations from Alabama, California, Indiana, and Oregon, respectively. The most resistant population originated from California, with an ED50 of 13.2 lb a.i. acre−1. To reduce selection pressure from ethofumesate populations, golf course superintendents are encouraged to develop site‐specific weed control programs that rotate herbicide sites of action, as well as utilize diverse control tactics.

Hemp Seed Yield Responses to Nitrogen Fertility Rates

Industrial hemp (Cannabis sativa L.) holds promise as a crop for more sustainable supply chains given its potential as a source of high-strength fibers, adsorbents, and nutrient-dense feedstuffs. Developing nutrient management guidelines for hemp will be an important part of optimizing the crop’s sustainability attributes. This study measured hemp seed yield in response to N fertilization rate (0, 60, 120, 180, and 240 kg N ha−1). Treatments were tested with four hemp cultivars (‘Joey’ and ‘Grandi’ in 2020, 2021, and 2022 and ‘NWG 2463’ and ‘NWG 4113’ in 2023) in Virginia. Nitrogen input influenced (p ≤ 0.0177) seed yield in all four experimental years, although the pattern of response varied substantially. In 2020, following delayed seeding, hemp showed a weak quadratic (p = 0.0113) response to N inputs, with peak yield (1640 kg ha−1) occurring with 120 kg N ha−1. In 2021, hemp displayed a strong linear (p < 0.0001) response to N inputs, with the highest seed yield (2510 kg ha−1) at 240 kg N ha−1. In 2022, a season characterized by low precipitation and high weed pressure, a weak, linear (p = 0.0111) response to the N rate was observed. The greatest seed yield (380 kg ha−1) was again observed with 240 kg N ha−1. In 2023, weed pressure remained an issue, but the response to N was strong and linear (p < 0.0001), with the greatest seed yield (831 kg ha−1) again measured at 240 kg N ha−1. These findings indicate hemp can be quite responsive to N inputs but that the magnitude of response is sensitive to other factors such as available soil moisture, weed pressure, and growing period.

Towards the development of cover crop - reduced tillage systems without herbicides and synthetic fertilizers in onion cultivation: Promising but challenges remain

Cover crops with reduced tillage technology (CC-RT) can foster soil health and functioning, a crucial agroecological principle in any transition strategy to more sustainable agricultural systems. However, CC-RT commonly strongly relies on herbicides and synthetic fertilizers, and vegetable crop yields are variable and often low. We assessed the effects of two tillage systems (RT and conventional tillage) and the application of native effective microorganisms (NEM) on onion crop growth and development, yield, N-status, weed pressure, and soil physico-chemical and biological quality after a summer CC, without using herbicides or synthetic fertilizers. Using a participatory research strategy, we conducted a two-year experiment at an experimental station and a one-year trial on two commercial farms. Onion yields were generally low (between 10 and 16 Mg ha−1) and lower in 2019 than in 2020, and lower in RT than in CT in 2020. The relatively low yields in 2019 and RT were associated with poor crop growth and development and leaf-N concentrations below the critical threshold in the early stages of crop development. Soil bulk density was not limiting crop growth in any treatment. Soil mineral N was lower in 2019 than in 2020 and did not significantly differ between treatments. Soil biological activity was higher in RT than in CT. Although the CC residue soil cover in the early stages of the onion crop in RT was more than 50%, RT had a higher weed pressure than CT, which was reversed later in the growing season. The NEM application did not significantly affect most crop, weed, and soil variables. In conclusion, a reduced tillage system for onions without herbicides and synthetic fertilizers is within reach. However, further research is needed to manage weeds and soil N supply dynamics to make CC-RT feasible for no or low agrochemical input systems.

Sidahermaphrodita establishment on highly weed-infested soil using biodegradable mulch film

The sustainable production of plant biomass for energy and material application within a growing bioeconomy is crucial to overcome the dependence on fossil resources. The perennial industrial crop Sida hermaphrodita L. var. Rusby (Sida) was subject of various investigations as a promising biogenic energy carrier, though its field establishment in the juvenile plant stage is challenging. While suitable chemical measures to suppress weeds in Sida are only scarcely available, the use of herbicides for weed control contradicts the sustainability in bioenergy provision. Therefore, this study aimed for an improved Sida plant establishing method using biodegradable mulch film on highly weed-infested soil. During the year of trial establishment, Sida growth under mulch film treatment was highly improved, resulting in 264% (±49%) higher shoots and 683% (±361%) higher ground cover by Sida compared to the control on bare soil where manual weed treatment was applied only, with weeds significantly reduced in number, size, and ground cover. Employing mulch film for the successful field establishment of Sida proved to be a promising approach as it effectively suppressed weeds despite high weed pressure, resulting in significant growth promotion of Sida.

Results of weed surveys in greening plants

Greening crops play an essential role in Hungary's agriculture. Weeds can also cause many problems during the development of greening plants. Our research aimed to evaluate the weed control properties of greening crops sown with different germination rates. Analysis of the effect of crop rotations on weed density. Comparison of weed growth in control, fertilised and greened areas. In October of 2021, a weed survey was carried out in lupin (Lupinus albus L.), common vetch (Vicia sativa L.), oil radish (Raphanus sativus var. oleiferus L.) and buckwheat (Fagopyrum eculentum Moench). During the weed survey, we determined the different weed species and their abundance. In terms of seed rates, the higher seed rates for lupin, oil radish, and buckwheat may be worth choosing for weed suppression. Plots in rotation III had the lowest weed incidence of all greening crops. The probable reason for this finding is that there was no prior greening in rotation III. For greening, the choice of buckwheat and oil radish will result in higher weed pressure. The most important weeds were the cereals sown before the greening crop. Fertilised plots had minimally fewer weeds than control plots. Research results show the difficulties of weed control in herbicide-free greening crops.

Effects of frequency of the stale seedbed after autumn or spring ploughing on weed density and composition in sown lemon balm

AbstractWeed management in organic farming needs to integrate a wide range of preventive tools. Here we tested the stale seed bed technique in field experiments with organic lemon balm. In a two‐factorial trial, four intensities of stale seedbed after either autumn or spring ploughing were tested in 2019/2020 and 2020/2021 on alluvial loams of the research farm Wiesengut in the Rhineland, Germany. Increasing the number of stale seedbed passes did not promote weed emergence before sowing in 2020 due to serious spring drought; in 2021 only the two last stale seedbed passes in later spring caused extra weed flushes, while cold weather conditions in early spring prevented weed response to the earlier passes. Despite the differences in the number of germinating weeds in 2021 before sowing, intensification of the stale seedbed had no decreasing effect on weed density in lemon balm after sowing. However, weed species‐specific periods were identified in which the stale seedbed selectively promoted emergence. Autumn ploughing followed by a superficial incorporation of the catch crop in spring resulted in a lower weed emergence than complete residue incorporation by spring ploughing. Seedbank size differed greatly between fields, probably due to crop rotation. The overall weed reducing effect of the tested tillage treatments was low, probably due to high weed pressure on the organic farm. To increase the efficacy of the stale seed bed technique, sufficient soil moisture as well as temperature requirements of the dominating weed flora need to be considered.

Robust detection of headland boundary in paddy fields from continuous RGB-D images using hybrid deep neural networks

Accurate and robust headland boundary detection in the field is crucial for formulating turning strategies for agro-machinery. The headland area is challenging to be detected because of its similar appearance to the farmland, coupled with complex field conditions such as high weed pressure and discontinuous headland edges. In this study, a machine vision-based method for headland boundary detection was proposed, which introduced depth information in addition to RGB images to improve its detection accuracy. A deep learning-based network combining convolutional neural network (CNN) and recurrent neural network (RNN) was constructed for headland semantic segmentation. An interactive attention module (IAM) was proposed to fuse complementary information in RGB-D images adaptively. A time series information processing module (TPM) composed of a set of bidirectional convolution long short-term memories (ConvLSTMs) was used to extract interrelated information from consecutive images. Image preprocessing techniques and a proposed distance-based boundary point clustering algorithm were applied to the headland segmentation mask to obtain the boundary line on the working side of the agro-machinery. Ablation study results confirmed the effectiveness of IAM and TPM in improving the headland segmentation performance. The network presented achieved excellent headland segmentation performance, with a mean intersection over union (mIoU) of up to 95.7%. The mean deviation of boundary line extraction on 256*144 resolution images was 3.57 pixels. The detection rate reached 25.8 frames per second (FPS), which could provide real-time reference lines for agro-machinery turning path planning.

First steps toward developing Lewis flax (Linum lewisii Pursh) as an agronomic crop

Abstract Perennial Lewis flax (Linum lewisii Pursh) has the potential to be grown as a new oilseed crop that could simultaneously meet commodity production, ecosystem service provisioning, and farm resiliency goals. Despite many potential benefits, Lewis flax remains minimally explored as an agronomic crop. Determining agronomic best practices for producing economically relevant stands of Lewis flax is critical to its adoption as an oilseed crop. Several aspects of Lewis flax agronomic production were explored through the lens of adaptive management between 2020 and 2022. Initial field trials aimed at assessing spring-seeded Lewis flax row spacing, plant population density, and intercropping strategies with legumes and grasses failed due to poor establishment. Heavy rains and excessive weed pressure further complicated attempts to reestablish these initial trials. We established additional Lewis flax plots via fall and dormant seeding in response to the failure of our first experiment. This second experiment focused on exploring row spacing, population density, and seeding timing impacts on flax production. Flax yield did not differ among our treatments, averaging 59 kg ha−1. The low yields realized by our field trials may be due to several factors including need for harvest technology optimization, high weed pressure, and need for Lewis flax genetic improvement. Our study is a first step toward developing recommendations for optimal production strategies for Lewis flax in an agronomic context. Continued exploration of methods to improve management and yield of Lewis flax will be critical to its successful development as an agronomic crop.

Weed Density Detection Method Based on a High Weed Pressure Dataset and Improved PSP Net

Weed Density Detection Method Based on a High Weed Pressure Dataset and Improved PSP Net

Relationships between Soil Tillage Systems, Nematode Communities and Weed Seed Predation

Soil tillage is generally recognized as having a negative effect on soil health and weed seed predators. Recent advancements in conservation tillage practices allow for further comparison of how different levels of soil disturbances could influence soil food web communities. Field trials were conducted in 2017 and 2018 at two different sites to measure the effects of four cover crop termination treatments: conventional till (CT), no-till (NT), strip-till following roller-crimping (ST-RC), and strip-till with a living mulch between crop rows (ST-LM) on soil health using nematode community indices as soil health bioindicators. Following cover crop termination, the soil was monitored in the subsequent bell pepper (Capsicum annuum) crop over three sampling dates (June, August, and October). In the ST-RC treatment plots, soil nutrients were enriched (increased Enrichment Index, EI) and the soil food web structure was improved (higher Structure Index, SI) by the mid-season of the 2017 trial. In the 2018 trial, the ST-RC treatment enhanced fungal decomposition pathways (fungivore/fungivore + bacterivore ratio) throughout the bell pepper crop cycle and enhanced bacterial decomposition (abundance of bacterivorous nematodes) by the end of the cropping cycle compared to the no-till treatment, suggesting that the ST-RC treatment can further improve soil health conditions achieved by the NT treatment. Scatter plots of sampling points revealed that the treatments CT and NT had very distinct nematode-weed community assemblages in both trials, with the ST-RC and ST-LM treatments distributed closely with the NT treatment. Multivariate analysis among soil health bioindicators, weed pressure and weed seed predation explained 76.4 and 55.7% of the variance in the 2017 and 2018 trials, respectively. Weed pressure was consistently negatively related to (1) the SI, indicating soil disturbance would lead to more weed pressure; (2) the EI, indicating soil with higher weed pressure was linked to poor soil nutrient cycling, (3) cover crop residues left in the field from conservation tillage, or (4) how well the living mulch of red clover covered the ground. This study did not show that weed seed predation would lead to lower weed pressure but weed seed predation increased as weed biomass increased.

Conservation agriculture for increasing productivity, profitability and water productivity in rice-wheat system of the Eastern Gangetic Plain

There are increasing concerns about the negative effects of conventional tillage (CT), extreme climate events, increased weed incidence, and reduced availability of farm inputs on crop yield and yield stability, profitability, and water productivity in rice-wheat (R−W) systems of the Eastern Gangetic Plains (EGP) in South Asia. Conservation agriculture (CA)-based tillage practices have been proposed in the region to address these concerns. We analysed 84 on-farm trials’ data comparing CA-based practices with farmers’ CT practices in R−W systems of eastern Terai region of Nepal in the EGP. The objectives were to investigate crop and cropping systems productivity, profitability, yield stability, irrigation (WPi) and total water productivity (WP(r+i)), and fertilizer-use efficiencies of three CA- and one CT-based practices in R−W systems. Treatments included: (i) CT-based: puddled transplanted rice - conventional tillage wheat (PTR−CTW); (ii) CA-based: PTR − zero tillage wheat (PTR−ZTW); (iii) CA-based: direct-seeded rice − ZTW (DSR−ZTW); and (iv) CA-based: un-puddled transplanted rice − ZTW (UPTR−ZTW). Results showed that although there were no significant differences in yield of either rice or wheat or R−W system between CA-based and CT treatments, there was a significant reduction in production cost (by 245−369 USD ha−1) mainly due to reduced labor use and increased net gain (188−223 USD ha−1) in all CA-based R−W system. DSR−ZTW showed the highest yield stability and net profit, demonstrating its adaptability in the region. Among the irrigation applicators (35%) in rice, DSR used 107 mm (67 mm higher than PTR) irrigation water with WPi of 70% and 96% of PTR and UPTR, respectively due to the need of additional irrigation for crop establishment. In contrast, among the irrigation applicators (75%) in wheat, due to earlier sowing of ZTW, it required 18% less irrigation water resulting in 9% higher WPi compared to CTW. However, a follow-up study two years after completion of field trials revealed that no local farmers had continued CA-based practices mainly due to high weed pressure, lack of land leveling, inaccessibility of zero-till (ZT) drill machines, and lack of ZT service providers. Effective support systems incentivizing in land leveling, ZT machines, technical knowledge dissemination, and the development of integrated weed management practices for scaling-out strategies are essential to adopt CA-based practices. As the results have great implications to reduce production costs and increase farm profits, save energy and water, increase land and labor productivity, and improve food security of millions of smallholder farmers in the EGP, strong policy support to incentivize farmers to avoid the adoption barriers of CA-based practices is required.

Effect of crop establishment and weed management methods on weed dynamics and productivity of direct-seeded rice in middle Indo-Gangetic Plains

A field experiment was conducted during rainy seasons of 2018 and 2019 at the ICAR-Research Complex for Eastern Region Patna, Bihar to evaluate the effect of crop establishment methods and weed management treatments on weeds and productivity of direct-seeded rice (DSR). The treatments consisted of three upland DSR establishment methods, viz. zerotill direct-seeded rice:(ZT-DSR); conventional-till (CT)-dry DSR (CTDSR) and CTDSR-dust mulching, and three weed pressure maintenance treatments including: low weed pressure: maintained with pre-emergence (PE) application of pendimethalin (1.0 kg/ha) at 2 days after seeding (DAS) followed by (fb) post-emergence (PoE) application of bispyribac–Na (30 g/ha) PoE at 20 DAS fb hand weeding (HW) twice at 30 and 50 DAS; medium weed pressure: maintained with pendimethalin (1.0 kg/ha) PE at 2 DAS fb bispyribac–Na (30 g/ha) PoE at 20 DAS, and high weed pressure: maintained with pendimethalin (1.0 kg/ha) PE alone, in upland DSR under the middle Indo-Gangetic Plains (MIGPs). The major weeds recorded with upland DSR were Cyperus rotundus, Cynodon dactylon, Echinochloa colona, Brachiaria ramosa, Caesulia axillaris and Physalis minima. Significantly the lowest relative weed abundance, weed density and biomass were recorded in CT-DSR-dust mulching compared to ZT-DSR and CTDSR. Among the weed management treatment, maximum weed suppression was recorded in low weed pressure in comparison to medium and high-weed pressure management practices. Significantly higher grain yield (2.14 t/ha) and net returns (₹ 20869/ha) were obtained with CT-DSR-dust mulching. Hence, it may be concluded that for better rice productivity and weed management in upland DSR, CT-DSR-dust mulching with low weed pressure maintenance is the most potential and viable practices under the MIGPs.

Adapting to Climate Change Through Conservation Agriculture: A Gendered Analysis of Eastern Zambia

This study explored the use of conservation agriculture (CA) as a climate adaptation strategy among smallholder farmers in Eastern Zambia. Using 761 household interviews and 33 focus group discussions (FGDs) with smallholder farmers from six districts, data was collected on how smallholder farmers in the region experience climate change, what CA practices they had adopted, and benefits and challenges associated with CA practice. Results show that men and women farmers had similar experiences of climate change, namely late onset of a shortened rainy season, intra-seasonal drought and higher temperatures. Farmers' perceptions of gender-mediated effects of climate change had important nuances. The three most cited effects of climate change on women mentioned by women were lower crop yields, outbreaks of armyworms and reduced livestock fodder. The men thought women were most affected by increased hunger, lower crop yields and reduced domestic water sources. According to the women FGDs, men were most affected through reduced crop yields, increases in livestock diseases and increased hunger. The men self-reported reduced crop yields, reduced water for livestock and outbreaks of armyworms. Both men and women saw CA as having climate change adaptation benefits. For the women, men most benefitted from CA through the high moisture holding capacity of basins, higher crop yields and reduced labor requirements through use of oxen ripping. The men most appreciated the high crop yields, improved soil fertility and reduced costs as less fertilizer is used. The women cited the high moisture holding capacity of basins, high crop yields and improved soil fertility as benefits they most commonly derived from CA, while the men thought the women most benefitted from CA through the higher crop yields, improved soil fertility and crop tolerance to droughts. The study concludes that there is room for CA to serve as a climate smart agricultural system for both men and women smallholder farmers in Eastern Zambia. However, this will require addressing important challenges of high weed pressure, high labor demands, and low access to manure, and CA farming implements. The CA package for Zambia should include access to timely climate information and climate informed crop choices.

Mapping farmer perceptions, Conservation Agriculture practices and on-farm measurements: The role of systems thinking in the process of adoption

CONTEXTConservation Agriculture (CA) usage, particularly in Southern Africa, has remained low with lower yield, higher weed pressure and lower soil quality cited as reasons for ‘disadoption’. OBJECTIVEUsing a detailed case study of 50 farmers in two villages in Cabo Delgado (Northern Mozambique), this study seeks to test the hypothesis that farmers' perceptions of CA are associated with distinctly different ‘mental models’ and if these "ways of thinking" overlap with farmers' identified/self-identified groupings (e.g. CA users, ‘disadopters’ and conventional tillage users). Secondly, we examine whether these different mental models (perceptions) are associated with actual differences in on-farm measurements. Finally, we explore the hypothesis that ‘systems thinking’ (i.e., understanding nonlinear causal relationships and internal feedback loops that drive a complex system) and CA usage are positively associated. METHODSFuzzy Cognitive Mapping (FCM) was used to elicit representations of farmers' mental models. To explore the association between farmers' mental models of CA/conventional practices and on-farm measurements we evaluated cowpea aboveground biomass, yield, weed cover, and soil quality parameters from the farmer's main plot. We drew on network analysis to measure structural metrics of cognitive maps that provide important information about a person's mental model (perceptions) of causal interdependencies of farming dynamics. RESULTS AND CONCLUSIONSWe find evidence of two data-driven distinct clusters of farmers' mental models that are in relative alignment with farmers' identified/self-identified groupings. Cluster 1 mainly consists of conventional users and cluster 2 mainly consists of CA users/disadopters. While no significant differences in socio-demographic variables were observed, clusters of mental models were associated with key differences in on-farm measurements. Importantly, cluster 1, who tended to be conventional users, had lower yields, lower soil cover, significantly lower carbon stock and higher weed coverage than cluster 2. Soil quality indicators were higher in cluster 2 as were farmers' overall revenue per hectare. Moreover, cluster 2 had significantly higher degrees of ‘systems thinking’ (measured through complex network analysis of graphical mental models) than cluster 1 which had higher forms of linear thinking. We argue that higher forms of experiential learning and practice of CA relate to higher degrees of systems thinking and stronger positive perceptions of CA, even among the CA ‘disadopters’. SIGNIFICANCEOur findings highlight the importance of systems thinking abilities and inclusion of biophysical, socio-economic and mental modelling variables rather than simple binary measurements which may have led to erroneous conclusions on CA and thus has implications for how CA is understood and promoted in future.

Differences in Weed Suppression between Two Modern and Two Old Wheat Cultivars at Different Sowing Densities

Crop losses to weeds can be exacerbated in modern agricultural systems because modern crop cultivars have high population yields but low individual competitiveness. High density cropping systems offer the possibility of effectively suppressing weeds by increasing the initial size-asymmetric advantage of crops over the weeds. We tested this hypothesis in an outdoor mesocosm experiment with two old (Cultivar Heshangtou (HST) and Jinbaoyin (JBY)) and two modern (Xihan2 (XH2) and Xihan3 (XH3)) cultivars of spring wheat (Triticum aestivum L.), grown in a uniform pattern at four sowing densities under high weed pressure. Two annuals (Brassica napus and Linum usitatissimum) were used as model weeds sown at the same density in all treatments. Weed growth decreased and wheat yield increased with increasing crop density for all the cultivars, although yield levelled off at the highest densities. The old cultivars suppressed weeds better than the new cultivars at low density, reflecting the decline in individual competitiveness in modern cultivars. At high crop density, however, the modern XH3 suppressed the weeds as well as the old cultivars, supporting the hypothesis that traits that promote weed suppression are different at low vs. high density. Increasing crop density can be an effective way to suppress weed growth in many agricultural systems, and there is great potential for developing genotypes that can do this and produce high yields much better than the cultivars currently available.

Is Tillage a Suitable Option for Weed Management in Conservation Agriculture?

In Europe, conservation agriculture (CA) is currently challenged by higher weed pressure, potential glyphosate ban and reduced crop yield. Based on preliminary results and a critical analysis, we provide insights on how to assess the effect of introducing different levels of tillage intensity, after a long-term CA sequence, on weed communities and crop yield. The experiment compared three types of fallow management (ploughing (CT), reduced tillage (RT), no-till with glyphosate (NT)) on four fields after 17 years of no-plough, which ended with 7 years of CA. The introduction of tillage proved to be a major driver of weed communities before weeding (density, richness and composition) in winter wheat. Weed density and species richness before weeding was greatest in RT, intermediate in CT and lowest in NT. The number of grains per ear and crop yield increased with tillage intensity (+11% for RT, +31% for CT). We provide avenues for future research through detailed methods and key references. Differences in winter wheat productivity were possibly related to enhanced soil structure and increased mineralisation of soil organic matter. Potential benefits of occasional ploughing will depend on the density and composition of the newly upwelled weed seedbank, which will need to be assessed before implementing tillage. From a multicriteria perspective, the long-term benefits associated with CA could largely exceed short-term yield increases associated with occasional tillage. Future studies will need to characterize the impact of occasional tillage operations on the long-term multiperformance of CA systems.

Evaluation of weed competitiveness of direct-seeded rice (Oryza sativa) genotypes under different weed management practices

Performance of eight rice (Oryza sativa L.) genotypes (‘Swarna Shreya’, ‘IR84899-B-179-13-1-1-1’,‘IR83929-BB- 291-2-1-1-2’,‘DRR-42’,‘IR84899-B-183-20-1-1-1’,‘IR84894-143-CRA-17-1’,‘DRR-44’,‘Rajendra Bhagwati’) was evaluated in three weed management practices, i.e. application of pendimethalin @1.0 kg/ha as pre-emergence (PE) at 2 days after sowing (DAS) followed by (fb) bispyribac-Na @30 g/ha as post-emergence (POE) at 20 DAS and two hand weedings (40 and 60 DAS)-low weed pressure; application of pendimethalin @ 1.0 kg/ha as PE fb bispyribac- Na @ 30 g/ha as POE at 20 DAS-medium weed pressure and pendimethalin @ 1.0 kg/ha alone-high weed pressure during rainy seasons of 2016 and 2017 at Patna, Bihar. Application of pendimethalin (PE) followed by bispyribac-Na (POE) and two hand weedings (low weed pressure) significantly reduced weed infestation compared to pendimethalin alone (medium weed pressure). Markedly lower weed density was recorded with ‘IR84899-B-179-13-1-1-1’. Low weed pressure produced 90 and 26% more grain yield (2.53 t/ha) compared to medium (2.01 t/ha) and high weed pressure (1.33 t/ha).Significantly higher grain yield was recorded with ‘IR84899-B-179-13-1-1-1’ (2.32 t/ha) followed by ‘Swarna Shreya’ (2.18 t/ha). Low weed pressure had significantly higher gross returns (45.9×103 `/ha) and net returns (14.1×103 `/ha). Amongst genotypes, ‘IR84899-B-179-13-1-1-1’ had the highest gross returns (44×103 `/ha) and net income (17.6×103 `/ha). Hence, it may be concluded that application of pendimethalin (PE) fb bispyribac-Na (POE) along with hand weeding had significant impact on reduction of weed infestation and helps in achieving the higher grain yield of direct-seeded rice genotypes in eastern India.

Weed Pressure, Yield, and Adhesion of Soil-biodegradable Mulches with Pie Pumpkin (Cucurbita pepo)

A soil-biodegradable mulch (BDM) is designed to be tilled into the soil at the end of the growing season, and is a successful alternative to polyethylene (PE) mulch if it suppresses weeds and improves soil temperature and moisture, crop yield, and fruit quality. This study compared one clear plastic BDM (COX), two black plastic BDMs (BOX and BFO), and two paper BDMs (WGP and AMX) to clear and black plastic PE mulch (CPE and BPE, respectively) for weed control, yield, and mulch adhesion of ‘Cinnamon Girl’ pie pumpkin (Cucurbita pepo) in a Mediterranean climate where increased soil temperature from mulch is desirable. BDMs in this study are advertised as soil-biodegradable, and we tested functionality but not biodegradability. Mulch deterioration during the growing season was measured as percent soil exposure (PSE), and remained low at the end of the growing season for all BDM and PE treatments both years (5% on average) except COX (68%). Weed number and biomass were low early, mid, and late season for all treatments except COX in 2018 and COX and CPE in 2019. Soil temperature with PE mulches (20.7 °C on average) was similar or slightly higher than with plastic BDMs (19.8 °C on average), which was higher than with paper BDMs (18.9 °C on average). Total fruit number and yield were similar for PE mulches (19.3 and 24.5 kg, respectively) and black plastic BDMs (17.3 and 21.2 kg, respectively), which were higher than COX and paper BDMs (15.7 and 19.8 kg, respectively). Mulch adhesion occurred on fruit in all BDM treatments, with more mulch adhesion in BFO in 2018 and WGP in 2019 than in other BDM treatments each year. The number of wipes is a proxy for the impact on harvest labor and can influence overall on-farm profitability. The number of wipes to remove adhered mulch (1.2 wipes on average) was similar for fruit harvested at four times of day (0800, 1000, 1200, and 1400 hr), but more wipes were needed to remove adhered mulch when fruit were stored up to 4 hours postharvest (5.4 wipes). Number of wipes to remove adhered mulch was negatively correlated to the amount of moisture on the fruit surface (R2 = 0.31). Overall, these findings demonstrate that all black plastic and paper BDMs remained intact throughout the growing season and controlled weeds as well as black PE mulch, while clear BDM had higher weed pressure because it degraded during the growing season. Pumpkin yield was similar for black plastic BDMs and PE mulches and lower for clear and paper BDMs. However, all BDMs in this study adhered to the fruit surface and their removal became more difficult as the fruit surface dried.

Seed Priming: An Approach to Enhance Weed Competitiveness and Productivity in Aerobic Rice: A Review

Growing rice under aerobic soil conditions is a promising water-wise technology under the context of ever-mounting water scarcity, but it is subject to poor stand establishment and high weed pressure. This invites severe competition between weeds and rice, thus reducing the crop yields on an average of 50-60 per cent. Early weed control is essential in aerobic rice. Therefore, any effort to mitigate the ill effect of crop-weed competition in the early stages of crop growth will ultimately enhance yield of aerobic rice. So, ‘seed priming’ is one of the best options to manage crop-weed competition in the early stages of crop growth. Seed priming is an approach to add moisture to seeds allowing seeds to be hydrated partially without radicle emergence Beneficial effects of seed priming such as higher germination uniformity, better allometric attributes, rapid stand establishment and vigorous early plant growth were important components for weed competitiveness in aerobic rice. Higher and synchronized emergence of primed seeds can ensure vigorous crop stand with rapid canopy development giving rice plants a preliminary advantage over weeds. Different seed priming methods/ priming agents Viz. hydro, osmo, halo, bio, solid matrix priming have been found effective in increasing the vigour and yield of aerobic rice. Therefore, seed priming is supposed to play a significant role in weed suppression. Seed priming also enhances the grain yield of rice mainly due to more vigorous seedlings resulting in earlier and enhanced resource capture, higher numbers of panicle-bearing tillers due to low mortality of seedlings, improved nutrient and moisture supply.