• Authors:
    • Mahdavi, B.
    • Modarres-Sanavy, S. A. M.
    • Dehshiri, A.
  • Source: Agronomy Article
  • Volume: 61
  • Issue: 10
  • Year: 2015
  • Summary: This study was done to evaluate the effects of increasing concentrations of CO2 (CC) on rapeseed. Pot experiments were done with three cultivars (Okapi, Zarfam and RGS003) of rapeseed (Brassica napus) for salinity tolerance. Four levels of salinity (0, 5, 10 and 15dS m(-1)) were tested on the three cultivars at three CC (350, 700 and 1050mmolL(-1)) at the greenhouse of Tarbiat Modares University, Iran, during the crop seasons of 2010 to 2011. Three CCs were considered as three environments and the other two treatments (salinity and cultivar) were tested within these environments in a complete block design arranged as a factorial. Results indicated that photosynthetic rates declined with increasing levels of salinity. Elevated CC significantly increased rates of photosynthesis. The highest CC reduced the impact of salinity on photosynthesis. Increased CC reduced the rate of transpiration, which had the effects of increasing rates of photosynthesis and water use efficiency (WUE); these effects increased vegetative growth and reduced the adverse effects of salinity. Increased CC and salinity reduced harvest index. WUE increased with CC increment, and decreased with salinity elevation.
  • Authors:
    • Chauhan,Y. S.
    • Thorburn,P.
    • Biggs,J. S.
    • Wright,G. C.
  • Source: Research Article
  • Volume: 66
  • Issue: 11
  • Year: 2015
  • Summary: With the aim of increasing peanut production in Australia, the Australian peanut industry has recently considered growing peanuts in rotation with maize at Katherine in the Northern Territory - a location with a semi-arid tropical climate and surplus irrigation capacity. We used the well-validated APSIM model to examine potential agronomic benefits and long-term risks of this strategy under the current and warmer climates of the new region. Yield of the two crops, irrigation requirement, total soil organic carbon (SOC), nitrogen (N) losses and greenhouse gas (GHG) emissions were simulated. Sixteen climate stressors were used; these were generated by using global climate models ECHAM5, GFDL2.1, GFDL2.0 and MRIGCM232 with a median sensitivity under two Special Report of Emissions Scenarios over the 2030 and 2050 timeframes plus current climate (baseline) for Katherine. Effects were compared at three levels of irrigation and three levels of N fertiliser applied to maize grown in rotations of wet-season peanut and dry-season maize (WPDM), and wet-season maize and dry-season peanut (WMDP). The climate stressors projected average temperature increases of 1°C to 2.8°C in the dry (baseline 24.4°C) and wet (baseline 29.5°C) seasons for the 2030 and 2050 timeframes, respectively. Increased temperature caused a reduction in yield of both crops in both rotations. However, the overall yield advantage of WPDM increased from 41% to up to 53% compared with the industry-preferred sequence of WMDP under the worst climate projection. Increased temperature increased the irrigation requirement by up to 11% in WPDM, but caused a smaller reduction in total SOC accumulation and smaller increases in N losses and GHG emission compared with WMDP. We conclude that although increased temperature will reduce productivity and total SOC accumulation, and increase N losses and GHG emissions in Katherine or similar northern Australian environments, the WPDM sequence should be preferable over the industry-preferred sequence because of its overall yield and sustainability advantages in warmer climates. Any limitations of irrigation resulting from climate change could, however, limit these advantages.
  • Authors:
    • Wang, Z.
    • Wang, S.
    • Li, M.
    • Chen, H.
    • Wang, X.
    • Tian, X.
    • Liu, T.
    • Chen, Y.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 6
  • Year: 2015
  • Summary: Revealing the response of cereal yield and water use efficiency (WUE) to water management practices is crucial for achieving high and stable grain yields in drylands. A 3-yr field study was conducted to develop a high-yield, water-saving cultivation strategy for winter wheat in the Loess Plateau of China. The study's treatments included (i) a control (CK), that is, no mulch or fertilizer, (ii) nitrogen and phosphorus fertilizers (NP), (iii) plastic film mulch plus fertilizers (NP+PF), (iv) straw mulch plus fertilizers (NP+S), and (v) plastic film combined with straw mulch plus fertilizers (NP+PF+S). The results indicated that, compared with CK, the NP treatment improved the grain yield (112%) and WUE (96%) of winter wheat but resulted in a 12% reduction in soil water storage after the jointing stage. With the NP+S treatment, there was no difference recorded in grain yield, yield components, or WUE of winter wheat (relative to the NP treatment). With the NP+PF treatment, there was a 53% increase in grain yield, a 46% increase in WUE, and a 21% increase in soil water storage after jointing compared to the NP treatment. The plastic film could also modify soil temperature, resulting in maximized soil water retention. Additionally, the NP+PF and NP+PF+S treatments resulted in similar results. Taking into account agricultural, environmental, and economic factors, in addition to optimal fertilization (NP), plastic film mulch is the recommended practice for maximum yield and water retention in tablelands, whereas plastic film combined with straw mulch is recommended in terraces.
  • Authors:
    • Duniway, M. C.
    • Munson, S. M.
    • Bradford, J. B.
    • Gremer, J. R.
  • Source: Primary Research Article
  • Volume: 21
  • Issue: 11
  • Year: 2015
  • Summary: Climate change predictions include warming and drying trends, which are expected to be particularly pronounced in the southwestern United States. In this region, grassland dynamics are tightly linked to available moisture, yet it has proven difficult to resolve what aspects of climate drive vegetation change. In part, this is because it is unclear how heterogeneity in soils affects plant responses to climate. Here, we combine climate and soil properties with a mechanistic soil water model to explain temporal fluctuations in perennial grass cover, quantify where and the degree to which incorporating soil water dynamics enhances our ability to understand temporal patterns, and explore the potential consequences of climate change by assessing future trajectories of important climate and soil water variables. Our analyses focused on long-term (20-56 years) perennial grass dynamics across the Colorado Plateau, Sonoran, and Chihuahuan Desert regions. Our results suggest that climate variability has negative effects on grass cover, and that precipitation subsidies that extend growing seasons are beneficial. Soil water metrics, including the number of dry days and availability of water from deeper (>30 cm) soil layers, explained additional grass cover variability. While individual climate variables were ranked as more important in explaining grass cover, collectively soil water accounted for 40-60% of the total explained variance. Soil water conditions were more useful for understanding the responses of C 3 than C 4 grass species. Projections of water balance variables under climate change indicate that conditions that currently support perennial grasses will be less common in the future, and these altered conditions will be more pronounced in the Chihuahuan Desert and Colorado Plateau. We conclude that incorporating multiple aspects of climate and accounting for soil variability can improve our ability to understand patterns, identify areas of vulnerability, and predict the future of desert grasslands.
  • Authors:
    • Vervoort, L.
    • Moonen, P.C.
    • Almeida, J.
    • Degerickx, J.
    • Muys, B.
    • Achten, W.M.
  • Source: Global Change Biology Bioenergy
  • Volume: 8
  • Issue: 2
  • Year: 2015
  • Summary: Small-scale Jatropha cultivation and biodiesel production have the potential of contributing to local development, energy security, and greenhouse gas (GHG) mitigation. In recent years however, the GHG mitigation potential of biofuel crops is heavily disputed due to the occurrence of a carbon debt, caused by CO2 emissions from biomass and soil after land-use change (LUC). Most published carbon footprint studies of Jatropha report modeled results based on a very limited database. In particular, little empirical data exist on the effects of Jatropha on biomass and soil C stocks. In this study, we used field data to quantify these C pools in three land uses in Mali, that is, Jatropha plantations, annual cropland, and fallow land, to estimate both the Jatropha C debt and its C sequestration potential. Four-year-old Jatropha plantations hold on average 2.3 Mg C ha-1 in their above- and belowground woody biomass, which is considerably lower compared to results from other regions. This can be explained by the adverse growing conditions and poor local management. No significant soil organic carbon (SOC) sequestration could be demonstrated after 4 years of cultivation. While the conversion of cropland to Jatropha does not entail significant C losses, the replacement of fallow land results in an average C debt of 34.7 Mg C ha-1, mainly caused by biomass removal (73%). Retaining native savannah woodland trees on the field during LUC and improved crop management focusing on SOC conservation can play an important role in reducing Jatropha's C debt. Although planting Jatropha on degraded, carbon-poor cropland results in a limited C debt, the low biomass production, and seed yield attained on these lands reduce Jatropha's potential to sequester C and replace fossil fuels. Therefore, future research should mainly focus on increasing Jatropha's crop productivity in these degraded lands. © 2015 John Wiley & Sons Ltd.
  • Authors:
    • Khan, N.
    • Samad, G.
    • Janjua, P.
  • Source: Njas-Wageningen Journal of Life Sciences
  • Volume: 68
  • Year: 2014
  • Summary: Climate change and its impact on agricultural production is being debated in economic literature in context of different regions. The geographical location of Pakistan is assumed to be vulnerable to climate change. Concentration of greenhouse gases (GHGs) like carbon dioxide, methane and nitrous oxide through human activities has altered the composition of climate. These gases have increased temperature on earth by trapping sun light. This higher temperature in tropical regions may negatively affect the growth process and productivity of wheat. This study aims to look at the impact of climate change on wheat production in Pakistan. The study uses Autoregressive Distributed Lag (ARDL) model to evaluate the impact of global climate change on the production of wheat in Pakistan. The study considers annual data from 1960 to 2009. On the basis of this historical data the study tries to capture the impact of climate change on wheat production up to now. The results of estimation reveal that global climate change doesn't influence the wheat production in Pakistan. However, on the basis of the results some appropriate adaptative measures are proposed to confront any adverse shock to wheat production in Pakistan. (C) 2013 Royal Netherlands Society for Agricultural Sciences. Published by Elsevier B.V. All rights reserved,
  • Authors:
    • Leu, A.
  • Source: Acta Horticulturae
  • Issue: 1018
  • Year: 2014
  • Summary: Soil carbon sequestration using current organic land management methods has the potential to mitigate a substantial proportion of global greenhouse gas emissions. A published peer review study by the Research Institute of Organic Agriculture (FiBL), found that organic farming practices remove 2,000 kg of carbon dioxide from the air each year and sequester it in a hectare of farmland. There is compelling data that significantly higher levels of CO 2 sequestration can be achieved. The Rodale studies have demonstrated that good organic practices can sequester 3596.6 kg of CO 2 per hectare year for around 30 years however when compost is added this increases to 8220.8 kg of CO 2 per hectare year. Other studies show that increasing the levels of soil carbon improves the resilience of farming systems to the increased frequency extreme weather events, such as droughts and heavy rains, that are linked to climate change.
  • Authors:
    • McDonald, A. J.
    • Bishnoi, D. K.
    • Kumar, A.
    • Jat, M. L.
    • Majumdar, K.
    • Sapkota, T. B.
    • Pampolino, M.
  • Source: Field Crops Research
  • Volume: 155
  • Year: 2014
  • Summary: In the high-yielding wheat production systems in Northwest (NW) Indo-Gangetic Plains of India, intensive tillage operations and blanket fertilizer recommendations have led to high production costs, decreased nutrient use efficiency, lower profits and significant environmental externalities. No-tillage (NT) has been increasingly adopted in this region to reduce costs and increase input use efficiency. But, optimal nutrient management practices for NT based wheat production are still poorly understood. Opportunities exist to further enhance the yield, profitability, and resource use efficiency of NT wheat through site-specific nutrient management (SSNM). On-farm trials were conducted in seven districts of Haryana, India for two consecutive years (2010-11 and 2011-12) to evaluate three different approaches to SSNM based on recommendations from the Nutrient Expert (R) (NE) decision support system in NT and conventional tillage (CT) based wheat production systems. Performance of NE based recommendations was evaluated against current state recommendations and farmers' practices for nutrient management. Three SSNM treatments based on NE based recommendation were (1) 'NE80:20' with 80% N applied at planting and 20% at second irrigation (2) 'NE33:33:33' with N split as 33% basal, 33% at Crown Root Initiation (CRI) and 33% at second irrigation; and (3) 'NE80:GS' with N split as 80% basal and further application of N based on optical sensor (Green Seeker (TM))-guided recommendations. Yield, nutrient use efficiency and economic profitability were determined following standard agronomic and economic measurements and calculations. Cool Farm Tool (CET), an empirical model to estimate greenhouse gases (GHGs) from agriculture production, was used to estimate GHG emissions under different treatments. Wheat grain and biomass yield were higher under NT in 2010-11 but no difference was observed in 2011-12. The three NE-based nutrient management strategies increased yield, nutrient use efficiency as well as net return as compared to state recommendation and farmers' fertilization practice. Global warming potential (GWP) of wheat production was also lower with NT system as compared to CT system and NE-based nutrient managements as compared to farmers' fertilization practice. State recommended nutrient management had similar GWP as NE-based nutrient managements except NE80:GS in which GWP was the lowest. Results suggest that no-tillage system along with site-specific approaches for nutrient management can increase yield, nutrient use efficiency and profitability while decreasing GHG from wheat production in NW India.
  • Authors:
    • Wassmann, R.
    • Sharma, D. K.
    • Sharma, P. C.
    • Kumar, V.
    • Sharma, S.
    • Gathala, M.
    • Rai, M.
    • Tirol-Padre, A.
    • Ladha, J.
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 1
  • Year: 2014
  • Summary: Rapid, precise, and globally comparable methods for monitoring greenhouse gas (GHG) fluxes are required for accurate GHG inventories from different cropping systems and management practices. Manual gas sampling followed by gas chromatography (GC) is widely used for measuring GHG fluxes in agricultural fields, but is laborious and time-consuming. The photo-acoustic infrared gas monitoring system (PAS) with on-line gas sampling is an attractive option, although it has not been evaluated for measuring GHG fluxes in cereals in general and rice in particular. We compared N2O, CO2, and CH4 fluxes measured by GC and PAS from agricultural fields under the rice-wheat and maize-wheat systems during the wheat (winter), and maize/rice (monsoon) seasons in Haryana, India. All the PAS readings were corrected for baseline drifts over time and PAS-CH4 (PCH4) readings in flooded rice were corrected for water vapor interferences. The PCH4 readings in ambient air increased by 2.3ppm for every 1000mgcm(-3) increase in water vapor. The daily CO2, N2O, and CH4 fluxes measured by GC and PAS from the same chamber were not different in 93-98% of all the measurements made but the PAS exhibited greater precision for estimates of CO2 and N2O fluxes in wheat and maize, and lower precision for CH4 flux in rice, than GC. The seasonal GC- and PAS-N2O (PN2O) fluxes in wheat and maize were not different but the PAS-CO2 (PCO2) flux in wheat was 14-39% higher than that of GC. In flooded rice, the seasonal PCH4 and PN2O fluxes across N levels were higher than those of GC-CH4 and GC-N2O fluxes by about 2- and 4fold, respectively. The PAS (i) proved to be a suitable alternative to GC for N2O and CO2 flux measurements in wheat, and (ii) showed potential for obtaining accurate measurements of CH4 fluxes in flooded rice after making correction for changes in humidity.
  • Authors:
    • Karlik, J. F.
    • Angevine, W. M.
    • Brioude, J.
    • Park, J. H.
    • Weber, R.
    • Ford, T. B.
    • Fares, S.
    • Ormeno, E.
    • Gentner, D. R.
    • Goldstein, A. H.
  • Source: Atmospheric Chemistry and Physics
  • Volume: 14
  • Issue: 11
  • Year: 2014
  • Summary: Agriculture comprises a substantial, and increasing, fraction of land use in many regions of the world. Emissions from agricultural vegetation and other biogenic and anthropogenic sources react in the atmosphere to produce ozone and secondary organic aerosol, which comprises a substantial fraction of particulate matter (PM2.5). Using data from three measurement campaigns, we examine the magnitude and composition of reactive gas-phase organic carbon emissions from agricultural crops and their potential to impact regional air quality relative to anthropogenic emissions from motor vehicles in California's San Joaquin Valley, which is out of compliance with state and federal standards for tropospheric ozone PM2.5. Emission rates for a suite of terpenoid compounds were measured in a greenhouse for 25 representative crops from California in 2008. Ambient measurements of terpenoids and other biogenic compounds in the volatile and intermediate-volatility organic compound ranges were made in the urban area of Bakersfield and over an orange orchard in a rural area of the San Joaquin Valley during two 2010 seasons: summer and spring flowering. We combined measurements from the orchard site with ozone modeling methods to assess the net effect of the orange trees on regional ozone. When accounting for both emissions of reactive precursors and the deposition of ozone to the orchard, the orange trees are a net source of ozone in the springtime during flowering, and relatively neutral for most of the summer until the fall, when it becomes a sink. Flowering was a major emission event and caused a large increase in emissions including a suite of compounds that had not been measured in the atmosphere before. Such biogenic emission events need to be better parameterized in models as they have significant potential to impact regional air quality since emissions increase by several factors to over an order of magnitude. In regions like the San Joaquin Valley, the mass of biogenic emissions from agricultural crops during the summer (without flowering) and the potential ozone and secondary organic aerosol formation from these emissions are on the same order as anthropogenic emissions from motor vehicles and must be considered in air quality models and secondary pollution control strategies.