Soybean is the world’s most widely grown leguminous crop and is an important source of oil and protein for food and feed in addition to other industrial uses. However, herbicide resistant and troublesome weed control challenges limit yield potential and threaten conservation tillage (CT) systems. Cover crops have been widely adopted as an integrated pest management component in CT systems to suppress weeds and maintain soybean yield potential. A three-year field experiment was conducted to estimate the influence of a cereal rye cover crop following conservation tillage on the critical period for weed control (CPWC) in soybean. The experiment was implemented in a split-plot design in which main plots as conservation tillage following cover crop (CT + CC), conservation tillage following winter fallow (CT + WF) and conventional tillage (CVT), and sub plots were multiple durations of weed free and weed interference. Results showed that the estimated CPWC of CT + CC and CT + WF treatments was 0 weeks and >7 weeks, respectively in 2018. In 2019, the estimated CPWC was 0 weeks, 5.0 weeks, and 1.3 weeks under CT + CC, CT + WF, and CVT treatments, respectively. In 2020, the estimated CPWC was 3.5 weeks, >6.2 weeks, and 0 weeks under CT + CC, CT + WF, and CVT treatments, respectively. The presence of cover crop delayed the CTWR and caused an early beginning of the CWFP compared with CT + WF treatment, hence shortened the CPWC in 2018 and 2019. In conclusion, the CT + WF system did not reduce the weed competition and subsequent yield loss in soybean as compared to CT + CC system.
Our changing climate will likely have serious implications on agriculture production through its effects on food and feed crop yield and quality, forage and livestock production, and pest dynamics, including troublesome weed control. With regards to weeds, climatic variables control many plant physiology functions that impact flowering, fruiting, and seed dormancy; therefore, an altered climate can result in a weed species composition shift within agro-ecosystems. Weed species will likely adapt to a changing climate due to their high phenotypic plasticity and vast genetic diversity. Higher temperatures and CO2 concentrations, and altered moisture conditions, not only affect the growth of weeds, but also impact the effectiveness of herbicides in controlling weeds. Therefore, weed biology, growth characteristics, and their management are predicted to be affected greatly by changing climatic conditions. This manuscript attempted to compile the available information on general principles of weed response to changing climatic conditions, including elevated CO2 and temperature under diverse rainfall patterns and drought. Likewise, we have also attempted to highlight the effect of soil moisture dynamics on the efficacy of various herbicides under diverse agro-ecosystems.
An increasing number of herbicide-resistant weeds, in addition to troublesome weeds, pose a significant challenge for chemical weed control in corn. Simultaneously, high-biomass cover crop adoption has gained popularity among farmers as an efficient weed control strategy. While the critical period of weed control (CPWC) following conventional tillage has been well documented, there is little knowledge of CPWC following high residue cover crops in corn. A two-year field experiment was conducted to estimate the influence of a high biomass crimson clover cover crop and conservation tillage on the critical period of weed control (CPWC) in corn. The experiment was implemented in a split-plot design in which the main plots were conventional tillage (CVT), conservation tillage following winter fallow (CT + WF), and conservation tillage following crimson clover (CT + CC), and the subplot included multiple durations of weedy plots (estimation of critical timing of weed removal (CTWR), i.e., beginning of weed control) and weed-free plots (estimation of critical weed-free period (CWFP), i.e., end of weed control). The results described that the estimated duration of CPWC in three systems, included CT + CC, CT + WF and CVT equals 2.8 weeks, 3.5 weeks, and 4.9 weeks respectively in 2019. In 2020, the predicted value of CTWR under CT + CC equals 3.8 weeks after planting and the predicted values of CWFP were 5.1 and 5.7 weeks after planting under CT + WF and CVT systems, however, the model did not predict some values within the fitted 8 weeks of time. In conclusion, the presence of a crimson clover cover crop delayed the CTWR and caused the early beginning of CWFP and hence shortened CPWC in 2019. During most of the growing season, weed biomass production was less under CT + CC plots than CVT and CT + WF systems of weedy treatment in both years. While weed biomass production fluctuated in CT + CC, CVT and CT + WF systems in weed-free treatment.
Chenopodium album L. and Chenopodium murale L. are two principal weed species, causing substantial damage to numerous winter crops across the globe. For sustainable and resource-efficient management strategies, it is important to understand weeds’ germination behaviour under diverse conditions. For the germination investigations, seeds of both species were incubated for 15 days under different temperatures (10–30 °C), salinity (0–260 mM NaCl), osmotic stress (0–1 MPa), pH (4–10), and heating magnitudes (50–200 °C). The results indicate that the germination rates of C. album and C. murale were 54–95% and 63–97%, respectively, under a temperature range of 10 to 30 °C. The salinity levels for a 50% reduction in the maximum germination (GR50) for C. album and C. murale were 139.9 and 146.3 mM NaCl, respectively. Regarding osmotic stress levels, the GR50 values for C. album and C. murale were 0.44 and 0.43 MPa, respectively. The two species showed >95% germination with exposure to an initial temperature of 75 °C for 5 min; however, seeds exposed to 100 °C and higher temperatures did not show any germination. Furthermore, a drastic reduction in germination was observed when the pH was less than 6.0 and greater than 8.0. The study generated information on the germination biology of two major weed species under diverse ecological scenarios, which may be useful in developing efficient weed management tactics for similar species in future agri-food systems.
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