• Authors:
    • Andersen, M. N.
    • Kirk, H. G.
    • Nielsen, K. L.
    • Korup, K.
    • Kaminski, K. P.
    • Topbjerg, H. B.
    • Liu, F. L.
  • Source: ACTA AGRICULTURAE SCANDINAVICA SECTION B-SOIL AND PLANT SCIENCE
  • Volume: 65
  • Issue: 5
  • Year: 2015
  • Summary: A drought screening experiment focusing on intrinsic water use efficiency (WUEi) was carried out among 132 clones belonging to a dihaploid potato mapping population. The clones were exposed to progressive soil drying during a five-day period in a greenhouse pot experiment. Analysis of the underlying variables was done based on a multivariate data analysis strategy. The strategy successfully divided the clones into WUEi performance categories. Differences between clonal WUEi responses were traced back to differences in the net photosynthetic rate. Stomatal conductance (g(s)) did not vary significantly between the clones. Leaf abscisic acid (ABA) concentration and leaf water potential were found to reflect known isohydric behaviour for potato, and a non-linear relationship could be established for g(s) and leaf ABA concentration across the WUEi groups. Similarly, a common non-linear relationship between leaf ABA concentration and soil water potential was found. The latter findings suggest that the investigated population did not harbour significant genetic variation as to ABA production as function of soil desiccation level or with respect to the sensitivity of stomatal aperture vis-a-vis leaf ABA concentration and soil water potential.
  • Authors:
    • Damerau,Kerstin
    • van Vliet,Oscar P. R.
    • Patt,Anthony G.
  • Source: Climatic Change
  • Volume: 130
  • Issue: 2
  • Year: 2015
  • Summary: The Middle East and North Africa (MENA) region stands out globally both for the immensity of its energy resources, and the paucity of its freshwater resources. Most energy extraction and conversion technologies have associated freshwater demand, and in the MENA region these account for 2 % of the available sustainable supply. We examine how this demand could change over the 21st century, assuming growth in population and economic output, and considering three alternative pathways for energy efficiency, carbon intensity, and energy exports from the region. We find that in the pathway marked by improved efficiency, a transition to renewable energy sources, and declining energy exports, water consumption for energy is twice as high as today's values by the end of the century. By contrast, in the pathway marked by continued commitment to fossil resource extraction, use, and export, water demand for energy might rise by a factor of five. If the region were to maintain high levels of energy exports, but would substitute the export of fossil fuels by an equivalent amount of electricity derived from sunlight, a freshwater volume comparable to the household needs of up to 195 million people could be saved.
  • Authors:
    • Ramos-Cairo, P. A.
    • Frois de Andrade, M. A.
    • Santos, J. L.
  • Source: Agriculture Journal
  • Volume: 49
  • Issue: 2
  • Year: 2015
  • Summary: Nitrogen (N) and potassium (K) are the major nutrients required for coffee plants growth and development. Soil water deficit reduces nutrients uptake, causing negative effects on photosynthesis and water relations of plants. Within certain limits, the increase in N and K concentration in soil solution could result in higher nutrient uptake, softening physiological disturbs caused by the water deficit. This study aimed to evaluate water relations and photosynthesis of young coffee plants grown in 16 L pots in a greenhouse. Treatments were three N and three K doses: conventional (urea 12 g plant -1 and KCl 4 g plant -1), doubled and tripled; and two water regimes: irrigated (soil at field capacity) and non-irrigated. Thus, treatments were arranged in a factorial 3*3*2, with three replicates in a completely randomized design. Water stress effects on leaf water potential and relative water content are softened by increase in N and K doses. However, transpiration, stomatal conductance and net photosynthesis are decreased by water stress, regardless of N and K doses. Increase in K doses reduces transpiration and stomatal conductance, regardless of water regime. This study suggests that increases in N and K could partially protect young coffee plants against the water stress, as they contribute to mitigate negative effects in plant water status; however, they do not prevent a decrease in net photosynthesis.
  • Authors:
    • Fransen, S.
    • Okwany, R. O.
    • Girma, K.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 1
  • Year: 2015
  • Summary: Managing the soil profile NO 3-N through crop selection and irrigation is an important consideration for the sustainable production of cellulosic biofuel feedstock crops. Data from two seasons were collected and analyzed from a 4-yr study conducted in Prosser, WA, to assess the effect of biofuel feedstock grasses and irrigation levels on soil profile NO 3-N. The experimental design was a split plot with three replications. The main plots had three irrigation levels (60, 80, and 100% evapotranspiration, ET), and the subplots contained three cultivars of switchgrass ( Panicum virgatum L.) and gamagrass ( Tripsacum dactyloides L.) cultivars. Soil and root samples were collected in fall 2011 (Season1) and winter of 2012 (Season2). Soil profile NO 3-N concentrations were highest at the lowest irrigation levels. In Season1, the soil profile NO 3-N concentration averaged over depths was 1.7 mg kg -1 for the switchgrass cultivars and 5.6 mg kg -1 for gamagrass. In Season2, the concentrations were 1.4 and 2.2 mg kg -1 for the switchgrass cultivars and gamagrass, respectively. We found a significant correlation between switchgrass root mass and soil profile NO 3-N; r=0.63-Kanlow; r=0.58-Blackwell; and r=0.46-Shawnee. Our results suggest that soil profile NO 3-N was lower under the switchgrass cultivars than gamagrass. More root mass and NO 3-N were accumulated at lower irrigation levels. The results reported here can help in developing practical decision tools for managing fertilizer N in biomass biofuel crops.
  • Authors:
    • Li, Z.
    • Chen, G.
    • Wang, L.
    • Zhang, L.
    • Yang, Y.
    • Sheng, H.
    • Zhou, C.
    • Han, K.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 1
  • Year: 2015
  • Summary: Increasing water and N use efficiency and lowering environmental pollution are primary concerns for both agricultural production and environmental quality in northwestern China. A 2-yr field experiment was conducted to assess and model the effects of irrigation, N, and plant density on maize ( Zea mays L.) when N fertilizer and irrigation were separated in an alternating furrow irrigation system. Regression modeling (a ternary quadratic equation) showed that N fertilization positively affected yield, water use efficiency, N uptake, soil NO 3-N, and NH 3 volatilization. Irrigation improved yield, N uptake, and increased soil NO 3-N in the deeper soil layer (0.6-2.0 m) but reduced water use efficiency, NH 3 volatilization, and soil NO 3-N in the 0- to 0.6-m soil layer. Planting density positively affected yield, water use efficiency, and N uptake but negatively influenced NH 3 volatilization and soil NO 3-N. The combination of 255 kg N ha -1 N fertilizer, 100 mm of irrigation water, and 59,467 plants ha -1 in 2010 and 245 kg N ha -1 N fertilizer, 98 mm of irrigation water, and 58,376 plants ha -1 in 2011 resulted in maximum income for maize yield (7245 kg ha -1 in 2010 and 6972 kg ha -1 in 2011). However, environmental and agronomic objectives did not match. Specifically, the combination of N, irrigation rate, and plant density with maximum yield increased N leaching and NH 3 losses, whereas the combination lowering environmental pollution due to N losses caused a reduction in yield. Therefore, the trade-off in management of N, irrigation, and planting density was emphasized for both environmental and agronomic benefits in our study.
  • Authors:
    • Schaffer, B.
    • Munoz-Carpena, R.
    • Migliaccio, K. W.
    • Kisekka, I.
    • Khare,Y.
  • Source: Research Article
  • Volume: 29
  • Issue: 5
  • Year: 2015
  • Summary: In shallow water table-controlled environments, surface water management impacts groundwater table levels and soil water dynamics. The study goal was to simulate soil water dynamics in response to canal stage raises considering uncertainty in measured soil water content. Water and Agrochemicals in the soil, crop and Vadose Environment (WAVE) was applied to simulate unsaturated flow above a shallow aquifer. Global sensitivity analysis was performed to identify model input factors with the greatest influence on predicted soil water content. Nash-Sutcliffe increased and Root Mean Square Error reduced when uncertainties in measured data were considered in goodness-of-fit calculations using measurement probability distributions and probable asymmetric error boundaries, implying that appropriate model performance evaluation should be carried out using uncertainty ranges instead of single values. Although uncertainty in the experimental measured data limited evaluation of the absolute predictions by the model, WAVE was found a useful exploratory tool for estimating temporal variation in soil water content. Visual analysis of soil water content time series under proposed changes in canal stage management indicated that sites with land surface elevation of less than 2.0-m NGVD29 were predicted to periodically experience saturated conditions in the root zone and shortening of the growing season if canal stage is raised more than 9 cm and maintained at this level. The models developed could be combined with high-resolution digital elevation models in future studies to identify areas with the greatest risk of experiencing saturated root zone. The study also highlighted the need to incorporate measurement uncertainty when evaluating performance of unsaturated flow models.
  • Authors:
    • Gizaw, Mesgana
    • Gan, Thian Yew
    • Kuo, Chun-Chao
  • Source: Article
  • Volume: 130
  • Issue: 2
  • Year: 2015
  • Summary: Under the effect of climate change, warming likely means that there will be more water vapour in the atmosphere and extreme storms are expected to occur more frequently and with greater severity, resulting in municipal Intensity-Duration-Frequency (IDF) curves with higher intensities and shorter return periods. A regional climate model, MM5 (the Pennsylvania State University / National Center for Atmospheric Research numerical model), was set up in a one-way, three-domain nested framework to simulate future summer (May to August) precipitation of central Alberta. MM5 is forced with climate data of four Global Climate Models, CGCM3, ECHAM5, CCSM3, and MIROC3.2, for the baseline 1971-2000 and 2011-2100 based on the Special Report on Emissions Scenarios A2, A1B, and B1 of Intergovernmental Panel on Climate Change. Due to the bias of MM5's simulations, a quantile-quantile bias correction method and a regional frequency analysis is applied to derive projected grid-based IDF curves for central Alberta. In addition, future trends of air temperature and precipitable water, which affect storm pattern and intensity, are investigated. Future IDF curves show a wide range of increased intensities especially for storms of short durations (a parts per thousand currency sign1-h). Conversely, future IDF curves are expected to shift upward because of increased air temperature and precipitable water which are projected to be about 2.9 A degrees C and 29 % in average by 2071-2100, respectively. Our results imply that the impact of climate change could increase the future risk of flooding in central Alberta.
  • Authors:
    • Helmers, M. J.
    • Kostel, J. A.
    • James, D. E.
    • Boomer, K. M. B.
    • Porter, S. A.
    • Tomer, M. D.
    • Isenhart, T. M.
    • McLellan, E.
  • Source: Agronomy Journal
  • Volume: 44
  • Issue: 3
  • Year: 2015
  • Summary: Spatial data on soils, land use, and topography, combined with knowledge of conservation effectiveness, can be used to identify alternatives to reduce nutrient discharge from small (hydrologic unit code [HUC]12) watersheds. Databases comprising soil attributes, agricultural land use, and light detection and ranging-derived elevation models were developed for two glaciated midwestern HUC12 watersheds: Iowa's Beaver Creek watershed has an older dissected landscape, and Lime Creek in Illinois is young and less dissected. Subsurface drainage is common in both watersheds. We identified locations for conservation practices, including in-field practices (grassed waterways), edge-of-field practices (nutrient-removal wetlands, saturated buffers), and drainage-water management, by applying terrain analyses, geographic criteria, and cross-classifications to field- and watershed-scale geographic data. Cover crops were randomly distributed to fields without geographic prioritization. A set of alternative planning scenarios was developed to represent a variety of extents of implementation among these practices. The scenarios were assessed for nutrient reduction potential using a spreadsheet approach to calculate the average nutrient-removal efficiency required among the practices included in each scenario to achieve a 40% NO 3-N reduction. Results were evaluated in the context of the Iowa Nutrient Reduction Strategy, which reviewed nutrient-removal efficiencies of practices and established the 40% NO 3-N reduction as Iowa's target for Gulf of Mexico hypoxia mitigation by agriculture. In both test watersheds, planning scenarios that could potentially achieve the targeted NO 3-N reduction but remove <5% of cropland from production were identified. Cover crops and nutrient removal wetlands were common to these scenarios. This approach provides an interim technology to assist local watershed planning and could provide planning scenarios to evaluate using watershed simulation models. A set of ArcGIS tools is being released to enable transfer of this mapping technology.
  • Authors:
    • Normand,F.
    • Lauri,P. E.
    • Legave,J. M.
  • Source: Acta Horticulturae
  • Volume: 1075
  • Year: 2015
  • Summary: Climate change is becoming an observed reality, very likely due to the increase of anthropogenic greenhouse gas concentration. Since a few decades, several research teams around the world carry out a huge work to model the future climatic change during the 21st century, based on several scenarios of greenhouse gas emission. We have to expect rise in average temperatures, in atmospheric CO 2 concentration, in soil salinity in some areas, and lower and more irregular rainfall. The climate variability and the frequency of extreme events (scorching heat, heavy rainfall, drought, hurricane) are also expected to rise. Climate change is therefore a great concern for agriculture. Mango is one of the most widely cultivated and popular fruits in these regions for its economic and nutritional values. It is the fifth most cultivated fruit in the world. It is consequently justified to wonder about the impact of climate change on the mango tree and about the consequences on mango production and cultivation. The lack of crop model for mango prevents the prediction of the effects of climate change on mango tree development and production. They are then assessed on the basis of our current knowledge on the influence of climatic variables on mango tree development and production. We describe the influence of climatic variables on processes of agronomical importance for the mango tree: photosynthesis, vegetative and reproductive development, fruit quality. We then review the climate changes predicted for two areas of mango production and draw the possible consequences for mango cultivation. Finally, we propose some research ways to adapt mango cultivation to climate change in the coming decades, such as cultivar and rootstock selection, and improvement of cultural practices. The interest of developing a mango crop model is discussed.
  • Authors:
    • Buentgen,Ulf
    • Tegel,Willy
    • Carrer,Marco
    • Krusic,Paul J.
    • Hayes,Michael
    • Esper,Jan
  • Source: Climatic Change
  • Volume: 131
  • Issue: 2
  • Year: 2015
  • Summary: Wetter et al. (2014; hereinafter W14) conclude that western Europe experienced significantly higher temperatures in AD 1540 compared to all other years in the instrumental record, including the summer heat waves of 2003 and 2010 (Schar et al. 2004; Barriopedro et al. 2011). Based on 300+ first-hand documentary weather reports, the authors argue that large parts of Europe were hit by an unprecedented, 11-month-long, 'Megadrought' in 1540 exceeding all recorded and reconstructed levels, and falling outside the probability range of state-of-the-art palaeoclimate model simulations. Despite compiling, transforming and interpreting an exceptional pool of documentary evidence, W14 neglected to systematically analyse the existing collection of European tree ring-based climate reconstructions. An independent comparison of their findings from societal entries against natural proxy archives, however, would have been beneficial. For example, Pauling et al. (2006), already identified low precipitation amounts in 1540 derived mainly from tree-ring analyses, a study not cited in W14. In this reply we look into some of the tree-ring data available back to 1540 and before, and demonstrate that W14's conclusion regarding the inability of natural proxy archives to record climate extremes is not defensible.