Fallow Weed Research Articles

Nitrogen scavenging by winter fallow weeds and its availability to rice crops

Weedy fallow presents a promising strategy for nitrogen (N) scavenging and reducing N losses from croplands. The study aimed to (1) reassess the N scavenging potential of winter fallow weeds, specifically foxtail grasses, within rice cropping systems and (2) determine the availability of N scavenged by winter fallow weeds in rice paddies to rice crops. A two-year on-farm investigation (2022 and 2023), a one-year 15N-tracing microplot experiment (2021), and a two-year field experiment (2022 and 2023) were conducted in Hunan Province, China. The on-farm investigation revealed that winter fallow weeds scavenged on average 10.6 g N m–2 in 2022 and 10.9 g N m–2 in 2023. In the 15N-tracing microplot experiment, a 24 % average recovery efficiency of N from winter fallow weeds, applied in conjunction with two rice varieties and two urea-N application rates, was observed. The field experiment showed that total N uptake by rice plants and grain yield of rice crops were linearly and quadratically related to the total N application rate (the sum of N in applied winter fallow weeds and urea), respectively, in both 2022 and 2023. These findings highlight the potential of winter fallow weeds in rice paddies to scavenge N effectively and reveal this scavenged N to be highly available to rice crops. This study offers insights into the dual advantages of winter fallow weeds within rice cropping systems, shedding light on their environmental benefits as well as their positive agronomic outcomes.

Validated simulation of a long-term cropping experiment reveals a pathway for improved productivity

Long-term farming system experiments with comprehensive soil, plant and meteorological data combined with well-validated dynamic farming system models are a powerful combination to evaluate the production and environmental implications of novel innovations in agriculture. A current deficiency is the lack of adequate comprehensive validations for long term crop sequences that capture the dynamics of soil and crop responses without resetting soil conditions, especially for soil mineral nitrogen (Min-N). This reduces confidence in the outcome of scenario analyses for proposed improvements in productivity and sustainability given the central role played by nitrogen (N) dynamics in both processes. We used data from a 30-year long-term experiment (LTE) to validate the APSIM model and achieved excellent predictions for soil and crop responses including the dynamics of Min-N without resetting. A critical step was to ensure that the parameters required for the pools of soil organic matter matched those measured at the site over the full rooting depth (1.6 m) rather than limiting measured values to surface layers and relying on default parameters in deeper layers. In subsequent scenario analyses of agronomic innovations including fallow weed control, earlier sowing and improved N fertiliser strategies, the validated model predicted potential increases in average annual productivity of 1.2 t ha-1 (30%), WUE of 2.0 kg ha-1 mm-1 (30%) and NUE of 13 kg kg-1 (21%) and reductions in average annual N leaching of 8 kg N ha-1 (-33%) and soil organic matter loss of 3.1 t ha-1 (31%) (0–10 cm) could be achieved with specific combinations of synergistic innovations previously investigated separately in shorter-term experiments. Our study represents a rare case of model validation capturing the dynamics of soil water, Min-N, biomass and grain yield in a long-term diverse crop sequence to provide confidence in scenario analyses of production and environmental consequences of agronomic innovations. LTEs provide a valuable resource for such validation, while conclusions drawn from simulation studies that lack comprehensive validation must be considered with caution.

Investigating image-based fallow weed detection performance on Raphanus sativus and Avena sativa at speeds up to 30 km h−1

Site-specific weed control (SSWC) can provide considerable reductions in weed control costs and herbicide usage. Despite the promise of machine vision for SSWC systems and the importance of ground speed in weed control efficacy, there has been little investigation of the role of ground speed and camera characteristics on weed detection performance. Here, we compare the performance of four camera/software combinations using the open-source OpenWeedLocator platform – (1) default settings on a Raspberry Pi HQ camera (HQ1); (2) optimised software settings on a HQ camera (HQ2), (3) optimised software settings on the Raspberry Pi v2 camera (V2); and (4) a global shutter Arducam AR0234 camera (ARD) – at speeds ranging from 5 km h−1 to 30 km h−1. A combined excess green (ExG) and hue, saturation, value (HSV) thresholding algorithm was used for testing under fallow conditions using tillage radish (Raphanus sativus) and forage oats (Avena sativa) as representative broadleaf and grass weeds, respectively. ARD demonstrated the highest recall among camera systems, with up to 100 % recall for tillage radish and 91.6 % for forage oats at 5 km h−1. At 30 km h−1 ARD recall for forage oats declined (P < 0.05) by 12.4 %. There was no significant change for tillage radish. All cameras experienced a decrease in recall as speed increased. The highest rate of decrease was observed for HQ1 with 1.12 % and 0.90 % reductions in recall for every km/h increase in speed for tillage radish and forage oats, respectively. Detection of the ‘grassy’ forage oats was worse (P < 0.05) than the broadleaved tillage radish for all cameras. Despite the variations in recall, HQ1, HQ2, and V2 maintained near-perfect precision at all tested speeds. The variable effect of ground speed and camera system on detection performance of grass and broadleaf weeds, indicates that careful hardware and software considerations must be made when developing SSWC systems.

Modeling long-term transfers of radiocesium in farmland under different tillage and cover crop treatments

The 2011 nuclear accident at Japan's Fukushima Daiichi Nuclear Power Plant (FDNPP) prompted inquiries about the long-term transfer of Cesium-137 (137Cs) from soil to agricultural plants. In this context, numerical modeling is particularly useful for the long-term evaluation of the consequences of agroecosystem contamination. Agricultural practices, such as tillage and cover cropping, play key roles in 137Cs recycling in agroecosystems. In this study, we used 10-year monitoring data to develop a dynamic model to predict 137Cs redistribution (via uptake, litterfall, translocation, and percolation) under different tillage (no-tillage, NT; rotary cultivation, RC; moldboard plow, MP) and cover crop (rye; hairy vetch; fallow weed) treatments. The verification exercise and assessment results indicated the model's reliability, as the temporal dynamics of predicted values agreed with observed values. Tillage significantly influenced the 137Cs distribution in soil, thereby decreasing plant uptake of 137Cs, whereas cover crop exerted a minimal effect on 137Cs cycling. Furthermore, while the 137Cs concentrations in soybean grain under RC and NT treatments were comparable 62 years after the FDNPP accident, the concentration under MP treatment remained consistently the lowest. Despite natural decay being the main cause of the decreased global 137Cs level in the agroecosystem, with minimal losses from percolation to deeper soil layers and soybean harvesting, adopting an appropriate tillage practice was shown to promote a long-term reduction of 137Cs concentration in crops. Finally, to improve the model's accuracy, further research should consider incorporating the effects of soil properties and extreme weather events on 137Cs flow into the model, as these factors are essential for realizing improved agroecosystem predictions.

Looking beyond Glyphosate for Site-Specific Fallow Weed Control in Australian Grain Production

Summer annual weed species in northern Australian summer fallows are frequently present at low densities and, increasingly, are glyphosate-resistant, creating the need for alternative herbicides for site-specific weed control. Alternative non-selective herbicide treatments are effective on problematic summer fallow weeds; however, many are yet to be evaluated as site-specific (spot spraying) treatments. This study aimed to identify herbicides that could be used in place of glyphosate to control larger/mature Chloris virgata and Sonchus oleraceus plants. The response of these weed species to 12 herbicide treatments was evaluated in pot experiments conducted over summer/autumn 2022. Despite herbicide treatments not being consistently effective across both species, there were instances where control was achieved by some herbicide treatments. S. oleraceus was controlled (i.e., ≤10% plant survival) by glufosinate-ammonium, paraquat and also with protoporphyrinogen-oxidase (PPO)-inhibiting herbicides saflufenacil, tiafenacil and trifludimoxazin. However, these results were not consistent in repeated studies or for C. virgata. Glyphosate was the only herbicide that controlled C. virgata. A glyphosate replacement as a spot-spraying treatment was not identified, and until further studies are more successful, alternative approaches are needed to preserve the ongoing effectiveness of this herbicide.

Estimating Carbon Capture Potential of Fallow Weeds in Rice Cropping Systems

Weeds occurred during the fallow season can well perform the function of carbon (C) capture due to receiving little human disturbance. This study aimed to evaluate the C capture potential of fallow weeds in rice (Oryza sativa L.) cropping systems. A six-region, two-year on-farm investigation and a three-year tillage experiment were conducted to estimate C capture in fallow weeds in rice cropping systems. The on-farm investigation showed that the average mean C capture by fallow weeds across six regions and two years reached 112 g m–2. The tillage experiment indicated that no-tillage practices increased C capture by fallow weeds by 80% on average as compared with conventional tillage. The results of this study not only contribute to an understanding of C capture potential of fallow weeds in rice cropping systems, but also provide a reference for including fallow weeds in the estimation of vegetative C sink.

Fallow weed application alters rice yield by changing nitrogen uptake

Summary Fallow weeds can be abundant in rice paddies without any inputs and provide ecosystem services like those of cover crops, such as reducing nitrogen (N) leaching and capturing carbon. Therefore, allowing fallow weeds to grow is a potential alternative to cover crops in rice cropping systems. To evaluate the feasibility of this strategy, the effect of fallow weeds on grain yield in rice needs to be clarified. In this study, 2-year field experiments were conducted to compare N uptake, biomass production, yield components, and grain yield in rice with and without application of fallow weeds (500 g m−2, sun-dried). Results showed that the application of fallow weeds reduced aboveground N uptake and biomass production by 21–30% during the early growth period (from transplanting to mid-tillering) in rice. However, these reductions did not lead to reduced grain yield because they were compensated for or even exceeded by increased aboveground N uptake and biomass production during the middle and late growth periods (from panicle initiation to maturity). In addition, the application of fallow weeds increased spikelets per panicle in rice by 6–7%. These results provide preliminary evidence that fallow weeds may alter yield formation in rice and highlight the need for further investigations of the ecophysiological mechanism underlying the effect of fallow weeds on N uptake in rice.

Reviton and Vida with Tank Mixtures for Fallow Weed Control

Reviton and Vida with Tank Mixtures for Fallow Weed Control

Residual Herbicides Alone and in Combinations for Fallow Weed Control

Residual Herbicides Alone and in Combinations for Fallow Weed Control

Efficiency of control of segetal vegetation in oats in organic agriculture

The article analyzes the results of studies conducted in the stationary experiment of NSC «Institute of Agriculture NAAS» to determine the impact of different systems of basic tillage on weed agrocenosis of oats in single and mixed crops with legumes (oats + diaper). The aim of the research is to establish the influence of different systems of basic tillage on the level of weediness of crops. The technology of growing crops in the experiment is generally accepted and recommended for the research area. The obtained research results convincingly show that from the replacement of fallow plowing by 20–22 cm by autumn disc cultivation by 10–12 cm weediness of oat crops at the time of its tillering increased from 15 to 25 pieces/m2 on average during the research or 40%. It was found that sowing oat-diaper mixture with 25% bean component, regardless of the system of main tillage, is an effective phytocoenotic agro-measure of control of segetal vegetation and reduces by 9–20% weed binary crops compared to monocotyledons. The priority of application of additional agrotechnical measure of control of segetal vegetation in agrocenosis of oats by carrying out spring pre-emergence loosening of soil by non-shelf implements by 6–8 cm was proved, which allowed to significantly reduce weed infestation. In particular, the spring pre-emergence loosening against the background of fallow plowing and autumn shallow disc cultivation weed reduction of oat crops decreased by 18 and 25% and 20 and 26%, respectively.

OpenWeedLocator (OWL): an open-source, low-cost device for fallow weed detection

The use of a fallow phase is an important tool for maximizing crop yield potential in moisture limited agricultural environments, with a focus on removing weeds to optimize fallow efficiency. Repeated whole field herbicide treatments to control low-density weed populations is expensive and wasteful. Site-specific herbicide applications to low-density fallow weed populations is currently facilitated by proprietary, sensor-based spray booms. The use of image analysis for fallow weed detection is an opportunity to develop a system with potential for in-crop weed recognition. Here we present OpenWeedLocator (OWL), an open-source, low-cost and image-based device for fallow weed detection that improves accessibility to this technology for the weed control community. A comprehensive GitHub repository was developed, promoting community engagement with site-specific weed control methods. Validation of OWL as a low-cost tool was achieved using four, existing colour-based algorithms over seven fallow fields in New South Wales, Australia. The four algorithms were similarly effective in detecting weeds with average precision of 79% and recall of 52%. In individual transects up to 92% precision and 74% recall indicate the performance potential of OWL in fallow fields. OWL represents an opportunity to redefine the approach to weed detection by enabling community-driven technology development in agriculture.

Carbon decomposition and nitrogen mineralization of foxtail and milk vetch incorporated into paddy soils for different durations of organic farming

ABSTRACT Foxtail (Alopecurus aequalis) and milk vetch (Astragalus sinicus) are typical winter weeds grown in single-cropping rice fields during the fallow season in central Japan. These winter weeds are generally incorporated into the soil as green manure during plowing, and before rice transplanting, to improve soil fertility and rice yield. To understand the carbon (C) decomposition and nitrogen (N) mineralization behavior of fallow weeds in organic rice farming, we carried out two experiments. Firstly, we examined the effect of adding 1% foxtail to soils that were sampled from fields that were farmed conventionally or organically for different durations (4–12 years). The results showed that net N mineralization of incorporated foxtail was not affected by the duration of organic farming, although the N mineralization of indigenous soil increased with organic farming duration. Secondly, 1% pulverized young and old foxtail (YF and OF; C/N ratios of 47.0 and 54.9, respectively), and milk vetch (YM and OM; C/N ratios of 13.0 and 14.6, respectively), were mixed with soil samples from fields that had been farmed organically for 15 years to determine the role of each plant. More than half of weed C was decomposed during 4 weeks of anaerobic incubation at 30°C. In addition, the net weed C decomposition potentials were significantly higher in YF and YM than those in OF and OM. The lower C/N ratio of milk vetch was contributed to a net N mineralization rate that was 8.4 times higher than that of foxtail. The percentage of N mineralized from milk vetch was significantly higher (about 2.3 times) than that from foxtail. Even though foxtail incorporation can contribute to the growth of organic rice as an N nutrient source, it should be noted that net N immobilization occurred for 2 weeks of incubation at 30°C, and sometimes extended to 4 weeks before net N mineralization became tangible. Considering this early net N immobilization following incorporation of foxtail, it is recommended to wait at least 4 weeks between the start of flooding after weed incorporation and transplanting rice to facilitate initial growth and avoid N exhaustion.

Fallow Weed Control with Liberty and Enlist One Tank Mixtures and Application Timings

Fallow Weed Control with Liberty and Enlist One Tank Mixtures and Application Timings

Fallow Weed Control with Vida Tank Mixtures

Fallow Weed Control with Vida Tank Mixtures

Translated summary of original article “Contribution of fallow weed incorporation to nitrogen supplying capacity of paddy soil under organic farming” in Soil Science and Plant Nutrition

Translated summary of original article “Contribution of fallow weed incorporation to nitrogen supplying capacity of paddy soil under organic farming” in Soil Science and Plant Nutrition

Air-drying and drying-rewetting effects in Japanese Andosols subjected to long-term organic rice farming

ABSTRACT Paddy fields are generally submerged during the growing season and drained in the fallow season, and occasionally stimulating the air-drying effect and drying-rewetting effect on soil nitrogen (N) mineralization and soil carbon (C) decomposition. It is important to understand how these two effects take place in Andosol field under organic farming. To elucidate these effects, we incubated fresh, air-dried, and dried-rewetted paddy soil anaerobically under flooded condition. Soils were from the fields subjected to organic rice farming (ORF) for 4–5 years (4ORF), 8–9 years (8ORF), and 12 years (12ORF) with only rice residues and fallow weeds as organic matter applied, and cnventional rice farming (CRF). Soil samples were collected from plow layer of 0–15 cm depth after the rice harvest. The results showed that air-dried and dried-rewetted treatments could significantly increase N mineralization potential in 8ORF and 12ORF. The air-drying effects were not significantly changed in 4ORF, but significantly increased in 8ORF and 12ORF as compared to CRF. The drying-rewetting effects of C decomposition potentials were highest in 12ORF significantly. The N mineralization potential of air-drying effect showed no significant difference compared to drying-rewetting effect on conventional and organic rice farming. The ratio of C decomposition to N mineralization after 8 weeks incubation was higher in fresh soil (at 7.26–8.61) than those in air-dried (at 4.09–4.35) and dried-rewetted (at 3.94–4.26) soils. These indicated that the easily decomposable soil organic matter under the anaerobic flooded condition from fresh soil was changed by air-drying and drying-rewetting treatments. The slow increase of N mineralization and C decomposition with years of organic farming suggest the slow increase of fallow weed, the biomass of which gradually increase with years. The specific behavior of 12ORF soil suggest the transition of soil condition from a transitional state to an established state.

Weed-sensing technology modifies fallow control of rush skeletonweed (Chondrilla juncea)

AbstractRush skeletonweed is an aggressive perennial weed that establishes itself on land in the Conservation Reserve Program (CRP), and persists during cropping following contract expiration. It depletes critical soil moisture required for yield potential of winter wheat. In a winter wheat/fallow cropping system, weed control is maintained with glyphosate and tillage during conventional fallow, and with herbicides only in no-till fallow. Research was conducted for control of rush skeletonweed at two sites in eastern Washington, Lacrosse and Hay, to compare the effectiveness of a weed-sensing sprayer and broadcast applications of four herbicides (aminopyralid, chlorsulfuron + metsulfuron, clopyralid, and glyphosate). Experimental design was a split-plot with herbicide and application type as main and subplot factors, respectively. Herbicides were applied in the fall at either broadcast or spot-spraying rates depending on sprayer type. Rush skeletonweed density in May was reduced with use of aminopyralid (1.1 plants m−2), glyphosate (1.4 plants m−2), clopyralid (1.7 plants m−2), and chlorsulfuron + metsulfuron (1.8 plants m−2) compared with the nontreated check (2.6 plants m−2). No treatment differences were observed after May 2019. There was no interaction between herbicide and application system. Area covered using the weed-sensing sprayer was, on average, 52% (P &lt; 0.001) less than the broadcast application at the Lacrosse location but only 20% (P = 0.01) at the Hay location. Spray reduction is dependent on foliar cover in relation to weed density and size. At Lacrosse, the weed-sensing sprayer reduced costs for all herbicide treatments except aminopyralid, with savings up to US$6.80 per hectare. At Hay, the weed-sensing sprayer resulted in economic loss for all products because of higher rush skeletonweed density. The weed-sensing sprayer is a viable fallow weed control tool when weed densities are low or patchy.

Tillage based, site-specific weed control for conservation cropping systems

AbstractAustralian conservation cropping systems are practiced on very large farms (approximately 3,000 ha) where herbicides are relied on for effective and timely weed control. In many fields, though, there are low weed densities (e.g., &lt;1.0 plant 10 m−2) and whole-field herbicide treatments are wasteful. For fallow weed control, commercially available weed detection systems provide the opportunity for site-specific herbicide treatments, removing the need for whole-field treatment of fallow fields with low weed densities. Concern about the sustainability of herbicide-reliant weed management systems remain and there has not been interest in the use of weed detection systems for alternative weed control technologies, such as targeted tillage. In this paper, we discuss the use of a targeted tillage technique for site-specific weed control in large-scale crop production systems. Three small-scale prototypes were used for engineering and weed control efficacy testing across a range of species and growth stages. With confidence established in the design approach and a demonstrated 100% weed-control potential, a 6-m wide pre-commercial prototype, the “Weed Chipper,” was built incorporating commercially available weed-detection cameras for practical field-scale evaluation. This testing confirmed very high (90%) weed control efficacies and associated low levels (1.8%) of soil disturbance where the weed density was fewer than 1.0 plant 10 m−2 in a commercial fallow. These data established the suitability of this mechanical approach to weed control for conservation cropping systems. The development of targeted tillage for fallow weed control represents the introduction of site-specific, nonchemical weed control for conservation cropping systems.

Contribution of fallow weed incorporation to nitrogen supplying capacity of paddy soil under organic farming

ABSTRACT We studied soil nitrogen (N) management in a farmer’s organic rice farming in Japan, where the farmer applied no external N but incorporated gramineous fallow weeds and rice residues as in situ N sources. We focused on the effect of fallow weed incorporation on N-supplying capacity of the paddy soil by tracking decomposition of 15N-labeled fallow weeds after incorporation. The result fits well to the first order kinetics with the decomposition rate of 34.3% a year. A model of soil N accumulation and mineralization based on the first order kinetics showed that soil organic N originated from the incorporated weed would become saturated at the level 1.92 folds the annual input of weed N after several consecutive years of the incorporation. Mineralizable soil N (Min-N) of the weed origin would also become saturated after several years accounting for 21.2% of the total Min-N which includes the indigenous soil N from plow layer. We suspended weed incorporation (SWI) in a sub-plot of the fields for two consecutive years to compare Min-N therein with that in another subplot in the same fields subjected to continued weed incorporation (CWI). After 2 years of the suspension treatment, Min-N in SWI decreased to a similar extent as estimated with the soil-N model based on the first-order kinetics, with which we estimated that 16.9% of annual N uptake by the rice plants originated from the weed including 5.9% from the weed incorporated in the same year and 11.0% from that in the past years. N inflow to soil organic N from the weed was very close to N outflow attaining the steady state. The rice yield could thus be sustained by maintaining the soil N-supplying capacity via the internal cycling of fallow weed N.

Yield potential determines Australian wheat growers’ capacity to close yield gaps while mitigating economic risk

Australia’s farmers are among the most efficient in the world, despite a relatively large gap between potential and achieved water-limited grain yield. With wheat yield gaps typically > 1.7 t/ha or 50% of the water-limited yield, it is important to investigate the degree to which this gap may be attributable to (rational) subprofit-maximising input levels in response to risk and risk aversion in many major grain-growing regions, particularly those with lower and more variable rainfall. Here, we use a set of 14 case study sites across the Australian wheatbelt to examine the risk-return profile of several agronomic management practices and show the extent to which the farmers’ risk attitude determines their decision-making. Using a novel profit-risk-utility framework that incorporates crop simulation, probability theory, finance techniques and risk-aversion analysis, we were able to better demonstrate how farmers might select practices that manage economic risk across sites ranging from low to high rainfall. Results varied with risk preference and yield potential. However, there are real opportunities to close the yield gap by adopting non-limiting or near non-limiting nitrogen fertiliser practices and controlling fallow weeds. We show for the first time that yields associated with current best practice can be surpassed for most levels of risk aversion by adopting an emergent practice of optimising the site-specific time of sowing and matching variety to time of sowing. For some sites and risk profiles, the emerging best practice package which includes additional N fertiliser is also profitable under risk. We also propose a modified integrated framework for yield gaps. Here, we distinguish allocative input constrains due to risk aversion from those due to access to resources, and we account for an innovation gap where the current agronomic frontier is shifted upwards by growers successfully, implementing new technologies that are not yet part of current best practice.