Weedy rice (Oryza sativa L.) is a troublesome rice (Oryza sativa L.) weed in Italy and in many other rice areas. The objective of this study was to correlate the O. sativa infestation level in northern Italy, the main European rice-growing area, with agricultural practices adopted by farmers by using data obtained from a farmer survey. In 2018 to 2019, a survey was carried out on 98 rice farms chosen to ensure different sizes, different cultivation practices, and variable degrees of O. sativa infestation. The following information was acquired: farm size; area cultivated with Clearfield® varieties; the most-adopted agronomic practices (type of tillage, crop rotation, type of sowing, water management, origin of seeds, adoption of stale seedbed, use of imazamox, presence of O. sativa resistant to imazamox); and level of O. sativa infestation: low (≤5 plants m−2), medium (>5 to 20 plants m−2), and high (>20 plants m−2). The data were analyzed through descriptive statistics and ordinal logistic regression to determine which agronomic practices influenced the level of O. sativa infestation. Farm clustering was also determined through two-step cluster analysis. Rice was cultivated as a monocrop and mainly sown in water, using purchased seeds, in plowed fields. More than half of the farms used the stale seedbed practice, and 63% adopted Clearfield® varieties, while about 45% of the farms reported imazamox-resistant O. sativa. The ordinal logistic regression underlined that use of a stale seedbed was correlated with the infestation level of O. sativa, and the two-step cluster analysis showed that the farms were mainly grouped based on the use of this technique. Most of the farms that used a stale seedbed had higher O. sativa infestation than those that did not use it, meaning that this practice was mainly applied in zones where O. sativa infestations were more serious.

Cloransulam postemergence (POST), diclosulam preemergence (PRE), and flumetsulam preplant incorporated (PPI) and POST were evaluated in six trials at two locations for control of sicklepod and pitted morningglory in soybean. Sicklepod control with cloransulam plus flumetsulam POST was equivalent to chlorimuron POST in seven of eight comparisons both 3 and 6 wk after treatment. Sicklepod control with cloransulam POST was equivalent to chlorimuron in only three of eight comparisons 3 wk after treatment, but late-season control was equivalent in five of six comparisons. Pitted morningglory control with cloransulam alone or in tank-mixture with flumetsulam POST was equivalent to chlorimuron in all comparisons. Control of sicklepod and pitted morningglory was greater in most comparisons when a POST application followed flumetsulam plus trifluralin PPI compared to only trifluralin PPI. In a total PRE stale seedbed system, where all treatments were tank-mixed with pendimethalin plus glyphosate, sicklepod control with all rates of flumetsulam and 26 or 35 g ai/ha diclosulam was equivalent to the standard treatment of imazaquin or metribuzin plus chlorimuron. None of the total PRE programs controlled sicklepod as well as when glyphosate was applied sequentially POST. Pitted morningglory was controlled 83 to 93% with 26 or 35 g/ha diclosulam, equivalent to imazaquin, metribuzin plus chlorimuron, or sequential glyphosate applications 8 wk after the PRE application. Increasing flumetsulam rate increased pitted morningglory control early season, but flumetsulam was not as effective as the other herbicides.

In greenhouse studies, glyphosate [N-(phosphonomethyl)glycine] at 1.0 and 3.0 kg/ha and paraquat (1,1′-dimethyl-4,4-bipyridinium ion) at 0.6 kg/ha were applied to exposed seeds of six grasses and two legume species on continuously wet soil. Glyphosate reduced germination of both legumes and three grasses and reduced seedling growth of all species. Paraquat was toxic only to the grasses. Glyphosate mainly affected germination and growth of legumes when applied directly to their seeds. Reductions also were measured, however, when untreated legume seeds were transferred to glyphosate-treated soil.

There is significant interest from processors in producing organic sweet corn and snap bean. However, large-scale production is necessary for this to be a practical and economical venture for processors. This study focused on the feasibility of managing weeds in organic sweet corn and snap bean, utilizing methods that are practical in large hectarage. Tactics such as rotary hoe, interrow cultivation, and a stale seedbed were evaluated alone or in combination. Hand-weeded and herbicide-based treatments were included for each crop for comparison. Percentage weed control, weed biomass, and crop yield were quantified, and net profit was calculated for each treatment. Organic weed management was feasible in snap bean, with yields similar among several of the organic treatments and the herbicide treatment in all 3 yr of the study. Interrow cultivation was the most effective means of organic weed control in snap bean. Organic weed management was possible in snap bean because it is a short-season crop and an effective competitor with weeds in the crop row. Organic weed management was more difficult in sweet corn because of the longer crop season and poor competition with weeds in the crop row. In sweet corn, the organic treatment involving three interrow cultivations was the only one consistently similar in yield to the herbicide treatments. Higher net profits were attained for most of the organic treatments in both crops because of the organic premium. Market saturation and organic premium adjustments are factors for grower consideration in this potential industry, particularly for sweet corn production.

In the rice–wheat (RW) systems of the Indo-Gangetic Plains of South Asia, conservation tillage practices, including zero-tillage (ZT), are being promoted to address emerging problems such as (1) shortages of labor and water, (2) declining factor productivity, (3) deterioration of soil health, and (4) climate change. Despite multiple benefits of ZT, weed control remains a major challenge to adoption, resulting in more dependence on herbicides for weed control. Alternative management strategies are needed to reduce dependence on herbicides and minimize risks associated with their overuse, including evolution of herbicide resistance. The objectives of this review are to (1) highlight and synthesize research efforts in nonchemical weed management in ZT RW systems and (2) identify future weed ecology and management research needs to facilitate successful adoption of these systems. In ZT RW systems, crop residue can play a central role in suppressing weeds through mulch effects on emergence and seed predation. In ZT rice, wheat residue mulch (5 t ha−1) reduced weed density by 22 to 76% and promoted predation of RW weeds, including littleseed canarygrass and barnyardgrass seeds. For ZT wheat, rice residue mulch (6 to 10 t ha−1) in combination with early sowing reduced emergence of littleseed canarygrass by over 80%. Other promising nonchemical approaches that can be useful in suppressing weeds in ZT RW systems include use of certified seeds, weed-competitive cultivars, stale seedbed practices, living mulches (e.g., sesbania coculture), and water and nutrient management practices that shift weed–crop competition in favor of the crop. However, more research on emergence characteristics and mulching effects of different crop residues on key weeds under ZT, cover cropping, and breeding crops for weed suppression will strengthen nonchemical weed management programs. Efforts are needed to integrate multiple tactics and to evaluate long-term effects of nonchemical weed management practices on RW cropping system sustainability.

Because herbicide and cultivation efficacy is generally density independent, seedling density following these weed control practices will be proportional to the density of germinable seeds in the seedbank. Most farmers would therefore benefit from management practices that reduce seed inputs, increase seed losses, and reduce the probability that remaining seeds establish. Germination, predation, and decay are the primary sources of loss to the seedbank that may respond to management. Farmers have long prepared stale seedbeds in which shallow soil disturbance encourages germination losses. Postdispersal seed predation by vertebrate and invertebrate granivores may cause high rates of seed mortality in a wide range of cropping systems, but seed dispersal asynchronous with predator activity, and seed burial, may limit the overall effect on the seedbank. Although seeds would seem to be an ideal carbon source for soil microorganisms, limited evidence from a study of wild oat suggests that decay may be less responsive to management than germination, and likely predation. A final management objective, supporting a program that aims to reduce seedbank inputs and increase losses, is to reduce the size of the effective seedbank through manipulation of residues and disturbance to reduce the probability of establishment. Incorporation of green manures generally reduces weed establishment, whereas larger-seeded or transplanted crops may better tolerate the residue-mediated changes in the chemical, biological, and physical properties of the soil surface environment. Evidence from no-till systems further support the hypothesis that changes in soil surface conditions may regulate the abundance of “safe sites” for weed establishment, thereby modulating the size of the effective seedbank.

Research was conducted to determine the effects of tillage on fluometuron and norflurazon loss in runoff when applied preemergence in cotton. Cumulative water loss and norflurazon and fluometuron concentrations in runoff were not affected by tillage systems. In 1992, the no-till system had less sediment loss in runoff than the conventional tillage system. Tillage systems did not affect sediment loss in 1993. The highest amount of total fluometuron loss occurred with the conventional tillage system in 1992, whereas the reduced tillage system had the lowest amount in 1993. There were no differences in cumulative norflurazon loss between tillage systems in 1992, and as with fluometuron loss, norflurazon loss in runoff was less with the reduced tillage system in 1993. This research indicates that, while conservation tillage may reduce sediment loss, it may not necessarily be the best management tool for decreasing the loss of herbicides in runoff.

Separate field experiments were conducted to evaluate weed control and cotton response to flumioxazin in North Carolina. Flumioxazin postemergence directed (PD) at 70 g ai/ha applied alone or mixed with glyphosate or MSMA completely controlled common lambsquarters, common ragweed, entireleaf morningglory, ivyleaf morningglory, Palmer amaranth, pitted morningglory, prickly sida, sicklepod, smooth pigweed, and tall morningglory 4 wk after treatment. Glyphosate at 1,120 g ai/ha controlled sicklepod and entireleaf, ivyleaf, pitted, and tall morningglory less than flumioxazin. Weed-free experiments were conducted to evaluate cotton injury, fresh biomass reduction, and yield response to flumioxazin at 70 g ai/ha preplant (PP) and two rates PD. Nine PP applications were made at various timings between 0 and 10 wk prior to planting. Cotton was stunted 12% initially, and midseason cotton biomass was reduced when flumioxazin was applied at planting in 1 yr. Flumioxazin did not injure 15- or 30-cm–tall cotton when applied PD at 36 or 70 g/ha. Cotton yield differed between years, but was not affected by various flumioxazin treatments compared with commercial standards and nontreated controls.

Rice is a principal source of food for more than half of the world population, and more than 90% of rice worldwide is grown and consumed in Asia. A change in establishment method from manual transplanting of rice seedlings to dry-seeded rice (DSR) has occurred in some countries as growers respond to increased costs or decreased availability of labor or water. However, weeds are a major constraint to DSR production because of the absence of the size differential between the crop and the weeds and the suppressive effect of standing water on weed growth at crop establishment. Herbicides are used to control weeds in DSR, but because of concerns about the evolution of herbicide resistance and a scarcity of new and effective herbicides, there is a need to integrate other weed management strategies with herbicide use. In addition, because of the variability in the growth habit of weeds, any single method of weed control cannot provide effective and season-long control in DSR. Various weed management approaches need to be integrated to achieve effective, sustainable, and long-term weed control in DSR. These approaches may include tillage systems; the use of crop residue; the use of weed-competitive cultivars with high-yield potential; appropriate water depth and duration; appropriate agronomic practices, such as row spacing and seeding rates; manual or mechanical weeding; and appropriate herbicide timing, rotation, and combination. This article aims to provide a logical perspective of what can be done to improve weed management strategies in DSR.

New tools for controlling weeds would be useful for soybean production in organic systems. Air-propelled abrasive grit is one such tool that performs well for in-row weed control in corn, but crop safety in soybean is unknown. Responses to abrasion by corn-cob grit of soybean seedlings were examined at VE, VC, VU, V1, V2 (emergence, cotyledon, unifoliate, first trifoliate, and second trifoliate, respectively) and combinations of these growth stages, in both greenhouse and field settings. Seedling leaf areas and dry weights in greenhouse experiments were reduced by treatments that included abrasion at VC, with the primary effect expressed through reductions in the size of the unifoliate leaf. In the field, soybean stand also was reduced by grit applications at VC, especially if followed by a second application at VU or V1. However, soybean yield was not reduced by grit applied at any soybean stage of growth. End-of-season weed dry weights did not differ from hand-weeded checks, and weeds did not impact soybean yields. Thus, abrasive grit for in-row weed control can be applied at least twice at VE through V2 growth stages without lowering soybean yield, but applications at VC probably should be avoided.

Demand for organic food products has consistently increased for more than 20 yr. The largest obstacle to organic soybean production in the southeastern United States is weed management. Current organic soybean production relies on mechanical weed control, including multiple postplant rotary hoe uses. Although postplant rotary hoe use is effective at the weed germination stage, its efficacy is severely compromised by delays due to weather. Preplant rotary hoeing is also a practice that has been utilized for weed control but the effectiveness of this practice to reduce the need for multiple postplant rotary hoeing for organic soybean production in the southeastern United States has not been investigated. Preplant rotary hoe treatments included a weekly rotary hoeing 4 wk before planting, 2 wk before planting, and none. Postplant rotary hoe treatments consisted of zero, one, two, three, and four postplant rotary hoe uses. Weed control was increased with preplant rotary hoeing at Plymouth in 2006 and 2007 but this effect disappeared with the first postplant rotary hoeing. Multiple postplant rotary hoe uses decreased soybean plant populations, decreased soybean canopy height, lowered soybean pod position, and decreased soybean yield. Plant mapping revealed that the percentage of total nodes and pods below 30 cm was increased by increased frequency of postplant rotary hoe use.

Persian darnel control options are limited and unmanaged populations can cause substantial crop yield loss. Integrating crop diversification and higher crop seeding rates into a cropping system might improve Persian darnel management. Field experiments were conducted to determine the effect of different crops and increased crop seeding rates on Persian darnel fecundity. Persian darnel produced up to 2,800 seeds per plant and 53,000 seeds/m2 when grown without competition. Increasing crop density reduced Persian darnel tillers per plant, seed weight, and fecundity. Increasing crop density reduced Persian darnel fecundity 0.4 to 0.2% per spring wheat plant, 0.6 to 0.1% per canola plant, and 16 to 8% per sunflower plant. Persian darnel fecundity was impacted the greatest by reduced weed seedling establishment, which was caused by crop competition and seeding sunflower late in the spring preceded by a nonselective herbicide application. Results indicated delaying the seeding of spring crops or including a late-seeded warm season crop, like sunflower or safflower, in the cropping system is an effective weed management tool for reducing Persian darnel fecundity.

Inoculation with arbuscular mycorrhizal (AM) fungi is a potentially useful tool in agricultural systems with limited options regarding use of synthetic chemicals for fertility and pest control. We tested the response of Allium porrum cv. Lancelot to inoculation with AM fungi in a field high in available P (169 μg g−1 soil) that had been repeatedly cultivated to control weeds. Seedlings were inoculated during the greenhouse production period with a mixed species inoculum produced on-farm in a compost and vermiculite medium with Paspalum notatum Flugge as a nurse host. Inoculated and uninoculated seedlings were the same size at outplanting. Inoculated seedlings were over 2.5-fold greater in shoot weight and shoot P content than uninoculated seedlings at harvest. These results demonstrate the potential yield benefits from inoculation with AM fungi in situations where farm management practices may negatively impact on indigenous populations of AM fungi.