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Beltsville, MD, United States

Ziska L.H.,Crop Systems and Global Change Laboratory
Field Crops Research

Differential responses of crops and weeds to anthropogenic climatic change may alter competition and crop yields. Here we examine the role of current and projected increases in carbon dioxide concentration [CO 2], on soybean growth and seed yield with and without competition from Canada thistle (Cirsium arvense, a common perennial weed in soybean farming systems), over a 3-year period using no-tillage (i.e., no physical cultivation for weed removal) practices. Weed control was implemented by applying herbicide (glyphosate) as a pre-emergent treatment at the beginning of each growing season. Under a weed-free condition, round-up ready soybean demonstrated a significant response of seed yield and total above-ground biomass to elevated [CO 2], but no synergistic effect of no-till over time on the response of biomass or yield to [CO 2] was observed. Average above-ground weight of Canada thistle was significantly greater at elevated [CO 2] for 2008 and 2009, and establishment of thistle increased as a function of [CO 2] over time even with pre-emergent applications of glyphosate. Although the presence of Canada thistle reduced seed yield and biomass of soybean for both CO 2 treatments from 2007 to 2009, the reduction was higher for the elevated [CO 2] treatment, and a significant [CO 2]×Canada thistle interaction was observed for these parameters. Overall, these are the first data to indicate that perennial weeds associated with no-tillage practices could be a greater impediment to crop yields and harder to control chemically in response to rising levels of atmospheric carbon dioxide. © 2010. Source

LaHue G.T.,University of California at Davis | Chaney R.L.,Crop Systems and Global Change Laboratory | Adviento-Borbe M.A.,Delta Water Management Research Unit | Linquist B.A.,University of California at Davis
Agriculture, Ecosystems and Environment

Rice (Oryza sativa L.) cultivation is critically important for global food security, yet it also represents a significant fraction of agricultural greenhouse gas (GHG) emissions and water resource use. Alternate wetting and drying (AWD) of rice fields has been shown to reduce both methane (CH4) emissions and water use, but its effect on grain yield is variable. In this three-year study we measured CH4 and nitrous oxide (N2O) emissions, rice grain total arsenic (As) concentrations, yield response to N rate, and grain yield from two AWD treatments (drill-seeded and water-seeded) and a conventionally managed water-seeded treatment (control). Grain yields (average = 10 Mg ha-1) were similar or higher in the AWD treatments compared to the control and required similar or lower N rates to achieve these yields. Furthermore, AWD reduced growing season CH4 emissions by 60-87% while maintaining low annual N2O emissions (average = 0.38 kg N2O-N ha-1); N2O emissions accounted for <15% of the annual global warming potential (GWP) in all treatments. Fallow season emissions did not vary by treatment and accounted for 22-53% of annual CH4 emissions and approximately one third of annual GWP on average. The AWD treatments reduced annual GWP by 57-74% and growing season yield-scaled GWP by 59-88%. Milled grain total As, which averaged 0.114 mg kg-1 in the control, was reduced by 59-65% in the AWD treatments. These results show that AWD has the potential to mitigate GHG emissions associated with rice cultivation and reduce rice grain total As concentrations without sacrificing grain yield or requiring higher N inputs; however future research needs to focus on adapting AWD to field scales if adoption of this technology is to be realized. © 2016 Elsevier B.V. Source

Linquist B.A.,University of California at Davis | Anders M.M.,University of Arkansas | Adviento-Borbe M.A.A.,University of California at Davis | Chaney R.L.,Crop Systems and Global Change Laboratory | And 3 more authors.
Global Change Biology

Agriculture is faced with the challenge of providing healthy food for a growing population at minimal environmental cost. Rice (Oryza sativa), the staple crop for the largest number of people on earth, is grown under flooded soil conditions and uses more water and has higher greenhouse gas (GHG) emissions than most crops. The objective of this study was to test the hypothesis that alternate wetting and drying (AWD - flooding the soil and then allowing to dry down before being reflooded) water management practices will maintain grain yields and concurrently reduce water use, greenhouse gas emissions and arsenic (As) levels in rice. Various treatments ranging in frequency and duration of AWD practices were evaluated at three locations over 2 years. Relative to the flooded control treatment and depending on the AWD treatment, yields were reduced by <1-13%; water-use efficiency was improved by 18-63%, global warming potential (GWP of CH4 and N2O emissions) reduced by 45-90%, and grain As concentrations reduced by up to 64%. In general, as the severity of AWD increased by allowing the soil to dry out more between flood events, yields declined while the other benefits increased. The reduction in GWP was mostly attributed to a reduction in CH4 emissions as changes in N2O emissions were minimal among treatments. When AWD was practiced early in the growing season followed by flooding for remainder of season, similar yields as the flooded control were obtained but reduced water use (18%), GWP (45%) and yield-scaled GWP (45%); although grain As concentrations were similar or higher. This highlights that multiple environmental benefits can be realized without sacrificing yield but there may be trade-offs to consider. Importantly, adoption of these practices will require that they are economically attractive and can be adapted to field scales. © 2014 John Wiley & Sons Ltd. Source

Fleisher D.H.,Crop Systems and Global Change Laboratory | Barnaby J.,Crop Systems and Global Change Laboratory | Sicher R.,Crop Systems and Global Change Laboratory | Resop J.P.,Crop Systems and Global Change Laboratory | And 2 more authors.
Agricultural and Forest Meteorology

Climate change predictions include increased frequency of episodic drought in many potato (Solanum tuberosum L.) producing regions in the world. Quantitative data on potato response to periodic drought under elevated atmospheric carbon dioxide (CO2) conditions is lacking, but is needed to improve crop modeling tools suitable for investigating adaptation strategies. Two experiments E1 and E2 were conducted in sunlit soil-plant-atmosphere research (SPAR) chambers to evaluate effects of short-term drought cycles at ambient and twice-ambient CO2. Experiments were conducted in the same growing season, but at different planting dates in order to further examine effects of variation in solar radiation during the drought periods (daily average photosynthetically active radiation of 43.9molm-2d-1 in E1 and 24.7molm-2d-1 in E2). Drought cycles were applied at post-tuber initiation (R) or at both vegetative and post tuber-initiation (VR) stages. While total dry matter in E1 was nearly twice that of E2 as a result of the radiation differences, relative responses to drought and CO2 were consistent. Total dry matter production was reduced proportionately based on the number of drought cycles, with twice-droughted VR plants producing less biomass than non-droughted controls. Harvest index and the ratio of tuber to total dry matter growth rate increased with drought frequency, suggesting that tuber sink strength was higher for VR plants than R. Harvest index, the ratio of tuber to total plant growth rate, and tuber dry matter for VR and R treated plants were also higher at elevated versus ambient CO2. Water use efficiency for water deficient versus water sufficient plants was correlated with harvest index and also increased at the higher CO2 concentration. As there was also little influence of drought or CO2 on leaf extension characteristics, differences in dry matter production and allometric responses were assumed to predominantly be a function of assimilation rate and carbon partitioning. These results confirm potato drought sensitivity in terms of yield response is influenced by developmental stage and CO2 regardless of light environment, and provide necessary data for calibration and testing modeling tools for climate change studies. © 2013. Source

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