Rice Paddy Soil Seedbanks Composition in a Mediterranean Wetland and the Influence of Winter Flooding

[EN] Soil seedbanks are defined in composition and quantity by many environmental factors inherent to a specific area, and they can be an indicator of the potential problems of weeds in crops. In Valencia (Spain), rice is cultivated with continuous flooding during the growing season, and after harvesting, many of the paddy fields are flooded again during the winter. This study investigates the paddy fields' soil seedbank composition in this Mediterranean paddy area and the effect of winter flooding on the soil seedbank. Multispectral images from the Sentinel-2 satellite were used to characterise the water level of paddies in winter. Satellite images facilitated the characterisation of winter flooding in fields. Soil samples from sixty-nine points distributed over 15,000 ha of paddies were used to determine the composition of the seedbank plots. The data were spatially represented by geographic information systems. The species that contributed most to the paddy seedbank were Cyperus difformis L., an important rice weed in the Mediterranean area, and other rice weeds such as Echinochloa sp. and Leptochloa fusca subspecies. Other species with a great contribution to the seedbank are species that develop in paddy fields that produce a large quantity of small seeds, such as Lemna sp., Polypogon monspeliensis (L.) Desf., and Nasturtium officinale R. Br. These species interfere little or do not interfere with the rice crop. The study revealed that in general, flooding reduced seedbank density with differences between species. Furthermore, the influence of winter flooding on the different plant species obtained as well as their distribution maps are a further step in this protected area from the point of view of weed management in rice crop, as well as in the management of this Mediterranean wetland.The Spanish Society ofWeed Science (SEMh) has contributed by granting one of the authors, F. Galan, funding to carry out this research. This research has not received any other external funding.Osca Lluch, JM.; Galán, F.; Moreno-Ramón, H. (2021). Rice Paddy Soil Seedbanks Composition in a Mediterranean Wetland and the Influence of Winter Flooding. Agronomy. 11(6):1-16. https://doi.org/10.3390/agronomy1106119911611

Early agriculture at the crossroads of China and Southeast Asia: Archaeobotanical evidence and radiocarbon dates from Baiyangcun, Yunnan

We report archaeobotanical results from systematic flotation at what is presently the earliest Neolithic site with hard evidence for crop cultivation in the Southwestern Chinese province of Yunnan, at the site of Baiyangcun. Direct AMS dates on rice and millet seeds, included together in a Bayesian model, suggests that sedentary agricultural occupation began ca. 2650 BCE, with cultivation of already domesticated rice (Oryza sativa), broomcorn millet (Panicum miliaceum), and foxtail millet (Setaria italica). Soybean (Glycine cf. max) was also present and presumably cultivated, although it still resembles its wild progenitor in terms of seed size. Additional possible cultivars include melon (Cucumis melo) and an unknown Vigna pulse, while wild gathered resources include fruits and nuts, including hawthorn (Crateagus) and aquatic foxnut (Euryale ferox). Weed flora suggests at least some rice was cultivated in wet (flooded or irrigated fields), while dryland weeds may derive from millet fields. This subsistence system persisted throughout the site's occupation, up to ca. 2050 BCE. These data provide secure evidence for the spread of Chinese Neolithic crops to Yunnan, and provide new evidence for reconstructing possible sources of cereal agriculture in mainland Southeast Asia

Evaluation of Non-Chemical Weed Management Options in Organic Rice Production

Flooding, allelopathic varieties, and non-synthetic herbicides are potential options for weed management in organic rice production. However, little research has been conducted on the effectiveness of these tools for weed management in organic rice production under field conditions. Experiments were conducted from 2016 to 2018 to understand the impact of flooding on the emergence of five major weeds in rice, determine the weed suppressive potential of four potentially allelopathic rice varieties, and evaluate the efficacy of seven non-synthetic herbicides. All weeds but Palmer amaranth emerged at 2.5 cm flooding depth, though the degree of emergence varied across weed species. Weedy rice and barnyardgrass had <10% and <5% emergence, respectively, at 7.5 cm flooding depth. Flooding depth at 2.5 cm delayed the emergence of Amazon sprangletop, Nealley’s sprangletop, barnyardgrass, and weedy rice by 8, 13, 8, and 2 days, respectively. With respect to weed suppressive rice varieties, PI 312777 was the best performing weed suppressive variety in the field with a relative yield of 60% and 81% in 2017 and 2018, respectively compared to a weed-free check. Among the non-synthetic herbicides evaluated, Homeplate® (caprylic acid + capric acid) showed good levels of weed control, causing 93% and 80% injury to broadleaf signalgrass and barnyardgrass, respectively. Rice injury with Homeplate® was substantial (46%) at 14 days after application (DAA), but rice crop recovered from this injury by 21 DAA. Overall, results from this research illustrate that these non-chemical options can be utilized as a part of an integrated weed management program in organic rice production

Evaluation of Non-Chemical Weed Management Options in Organic Rice Production

Flooding, allelopathic varieties, and non-synthetic herbicides are potential options for weed management in organic rice production. However, little research has been conducted on the effectiveness of these tools for weed management in organic rice production under field conditions. Experiments were conducted from 2016 to 2018 to understand the impact of flooding on the emergence of five major weeds in rice, determine the weed suppressive potential of four potentially allelopathic rice varieties, and evaluate the efficacy of seven non-synthetic herbicides. All weeds but Palmer amaranth emerged at 2.5 cm flooding depth, though the degree of emergence varied across weed species. Weedy rice and barnyardgrass had <10% and <5% emergence, respectively, at 7.5 cm flooding depth. Flooding depth at 2.5 cm delayed the emergence of Amazon sprangletop, Nealley’s sprangletop, barnyardgrass, and weedy rice by 8, 13, 8, and 2 days, respectively. With respect to weed suppressive rice varieties, PI 312777 was the best performing weed suppressive variety in the field with a relative yield of 60% and 81% in 2017 and 2018, respectively compared to a weed-free check. Among the non-synthetic herbicides evaluated, Homeplate® (caprylic acid + capric acid) showed good levels of weed control, causing 93% and 80% injury to broadleaf signalgrass and barnyardgrass, respectively. Rice injury with Homeplate® was substantial (46%) at 14 days after application (DAA), but rice crop recovered from this injury by 21 DAA. Overall, results from this research illustrate that these non-chemical options can be utilized as a part of an integrated weed management program in organic rice production

Evaluation of Non-Chemical Weed Management Options in Organic Rice Production

Flooding, allelopathic varieties, and non-synthetic herbicides are potential options for weed management in organic rice production. However, little research has been conducted on the effectiveness of these tools for weed management in organic rice production under field conditions. Experiments were conducted from 2016 to 2018 to understand the impact of flooding on the emergence of five major weeds in rice, determine the weed suppressive potential of four potentially allelopathic rice varieties, and evaluate the efficacy of seven non-synthetic herbicides. All weeds but Palmer amaranth emerged at 2.5 cm flooding depth, though the degree of emergence varied across weed species. Weedy rice and barnyardgrass had <10% and <5% emergence, respectively, at 7.5 cm flooding depth. Flooding depth at 2.5 cm delayed the emergence of Amazon sprangletop, Nealley’s sprangletop, barnyardgrass, and weedy rice by 8, 13, 8, and 2 days, respectively. With respect to weed suppressive rice varieties, PI 312777 was the best performing weed suppressive variety in the field with a relative yield of 60% and 81% in 2017 and 2018, respectively compared to a weed-free check. Among the non-synthetic herbicides evaluated, Homeplate® (caprylic acid + capric acid) showed good levels of weed control, causing 93% and 80% injury to broadleaf signalgrass and barnyardgrass, respectively. Rice injury with Homeplate® was substantial (46%) at 14 days after application (DAA), but rice crop recovered from this injury by 21 DAA. Overall, results from this research illustrate that these non-chemical options can be utilized as a part of an integrated weed management program in organic rice production

Evaluation of Non-Chemical Weed Management Options in Organic Rice Production

Flooding, allelopathic varieties, and non-synthetic herbicides are potential options for weed management in organic rice production. However, little research has been conducted on the effectiveness of these tools for weed management in organic rice production under field conditions. Experiments were conducted from 2016 to 2018 to understand the impact of flooding on the emergence of five major weeds in rice, determine the weed suppressive potential of four potentially allelopathic rice varieties, and evaluate the efficacy of seven non-synthetic herbicides. All weeds but Palmer amaranth emerged at 2.5 cm flooding depth, though the degree of emergence varied across weed species. Weedy rice and barnyardgrass had <10% and <5% emergence, respectively, at 7.5 cm flooding depth. Flooding depth at 2.5 cm delayed the emergence of Amazon sprangletop, Nealley’s sprangletop, barnyardgrass, and weedy rice by 8, 13, 8, and 2 days, respectively. With respect to weed suppressive rice varieties, PI 312777 was the best performing weed suppressive variety in the field with a relative yield of 60% and 81% in 2017 and 2018, respectively compared to a weed-free check. Among the non-synthetic herbicides evaluated, Homeplate® (caprylic acid + capric acid) showed good levels of weed control, causing 93% and 80% injury to broadleaf signalgrass and barnyardgrass, respectively. Rice injury with Homeplate® was substantial (46%) at 14 days after application (DAA), but rice crop recovered from this injury by 21 DAA. Overall, results from this research illustrate that these non-chemical options can be utilized as a part of an integrated weed management program in organic rice production

Evaluation of Provisia Rice in Arkansas Rice Production Systems

With the continued evolution of herbicide resistance, it is becoming more difficult to achieve adequate weed control in Arkansas rice production systems. Thus, new technologies are needed to combat these troublesome weeds. A new non-GMO, herbicide-resistant rice type is under development that is resistant to quizalofop, an acetyl coenzyme A carboxylase (ACCase)-inhibiting herbicide that will allow for selective grass weed control in rice. With the commercialization of this technology by 2018, research was conducted to determine the best fit for quizalofop-resistant rice in current production systems. Experiments included evaluation of off-target movement of quizalofop, determination of plant-back risk from quizalofop application, best rate structure of quizalofop, general efficacy on common grass weeds, and tank-mix interactions of quizalofop with common herbicides used in rice. Overall, the risk for off-target movement of quizalofop on Midsouth grass crops is minimal, with injury only observed under conditions that would be rare in the field. Plant-back risk after quizalofop or other ACCase-inhibiting herbicide applications is relatively low, with only grain sorghum and corn showing potential for injury if planted in quick succession after herbicide application. Quizalofop applications in quizalofop-resistant rice are effective for controlling barnyardgrass, broadleaf signalgrass, and red rice, with the best results from sequential applications of quizalofop at 120 g ai ha-1. A screening of barnyardgrass accessions from across the state of Arkansas proved quizalofop to be an effective graminicides, controlling all accessions evaluated. Tank-mix research for quizalofop and common rice herbicides prove that caution needs to be taken when tank-mixing quizalofop, especially with acetolactate synthase-inhibiting herbicides and auxinic herbicides due to the risk of antagonism. Overall, this research supports that quizalofop-resistant rice can be an effective tool for Arkansas rice producers

Evaluation of Fenclorim Safener for Use in Rice with Group 15 Herbicides

The development of herbicide resistance and the lack of effective herbicides to control problematic weeds has caused Arkansas rice (Oryza sativa L.) production to pursue alternative sites of action. Currently, very long-chain fatty acid elongase inhibitors are not labeled for U.S. rice production but have been widely used for Asian rice production systems. Previous research has demonstrated the utility of acetochlor and pyroxasulfone to provide in-season weed control for Arkansas rice production, but variable crop tolerance has been observed. Additionally, acetochlor at 1,260 g ai ha-1 elicited less rice injury when seeds were treated with a herbicide safener seed treatment of fenclorim at 2.5 g ai kg-1 of seed relative to without the fenclorim seed treatment. Therefore, trials were conducted in 2020 and 2021 to evaluate rice tolerance and weed control with pyroxasulfone, microencapsulated acetochlor, and a fenclorim seed treatment.. In-season applications of acetochlor provided better control of weedy rice and barnyardgrass with earlier application timings and increasing rates. The fenclorim seed treatment enhanced crop tolerance to acetochlor applied delayed-preemergence (DPRE) averaged over acetochlor rate. Also, rice demonstrated good tolerance to acetochlor applied DPRE at 1,260 g ai ha-1 with a fenclorim seed treatment at 2.5 g ai kg-1 of seed, which led to ≤ 19% rice injury, ≥ 88% barnyardgrass control, and ≥ 45% weedy rice control 28 days after treatment. Other studies evaluated the fenclorim seed treatment dose for acetochlor applied DPRE at 1,260 g ai ha-1. The fenclorim seed treatment rate of 2.5 g ai kg-1 of seed reduced rice injury from acetochlor relative to no fenclorim and provided comparable heights and number of shoots to the nontreated check at each evaluation. Increasing from 2.5 to 5 g kg-1 of seed provided no additional improvements for tolerance, and rice tolerance to acetochlor from fenclorim at \u3c 2.5 g kg-1 of seed was inconsistent and not commercially viable due to variable tolerance. Across 16 common Arkansas rice cultivars, DPRE acetochlor at 1,260 g ai ha-1 caused ≤ 24% injury, and rice planted under adverse growing conditions exhibited \u3c 20% injury with acetochlor and fenclorim. Regardless of the fenclorim seed treatment, rice demonstrated good tolerance to fall applications of acetochlor but not pyroxasulfone. Pyroxasulfone at the low and high rate, respectively, caused 39 and 47% injury 28 days after emergence and averaged over the fenclorim seed treatment. Additionally, weedy rice control ranged from 48 to 0% with acetochlor, and the fenclorim seed treatment did not influence weed control. Based on the results of these experiments, the fenclorim seed treatment will provide adequate crop tolerance to microencapsulated acetochlor but not to pyroxasulfone. Additionally, in both studies evaluating weed control, the fenclorim seed treatment did not influence weed control, indicating that the safening response for cultivated rice is not reciprocated to adjacent weeds. Should microencapsulated acetochlor be registered for use in U.S. rice production with the addition of the fenclorim seed treatment, rice producers would have a new, effective site of action to control problematic weeds without compromising crop tolerance