• Authors:
    • Sawyer, J. E.
    • Miguez, F.
    • Barker, D. W.
    • Mitchell, D. C.
    • Iqbal, J.
    • Pantoja, J.
    • Castellano, M. J.
  • Source: Web Of Knowledge
  • Volume: 44
  • Issue: 3
  • Year: 2015
  • Summary: Little information exists on the potential for N fertilizer application to corn ( Zea mays L.) to affect N 2O emissions during subsequent unfertilized crops in a rotation. To determine if N fertilizer application to corn affects N 2O emissions during subsequent crops in rotation, we measured N 2O emissions for 3 yr (2011-2013) in an Iowa, corn-soybean [ Glycine max (L.) Merr.] rotation with three N fertilizer rates applied to corn (0 kg N ha -1, the recommended rate of 135 kg N ha -1, and a high rate of 225 kg N ha -1); soybean received no N fertilizer. We further investigated the potential for a winter cereal rye ( Secale cereale L.) cover crop to interact with N fertilizer rate to affect N 2O emissions from both crops. The cover crop did not consistently affect N 2O emissions. Across all years and irrespective of cover crop, N fertilizer application above the recommended rate resulted in a 16% increase in mean N 2O flux rate during the corn phase of the rotation. In 2 of the 3 yr, N fertilizer application to corn (0-225 kg N ha -1) did not affect mean N 2O flux rates from the subsequent unfertilized soybean crop. However, in 1 yr after a drought, mean N 2O flux rates from the soybean crops that received 135 and 225 kg N ha -1 N application in the corn year were 35 and 70% higher than those from the soybean crop that received no N application in the corn year. Our results are consistent with previous studies demonstrating that cover crop effects on N 2O emissions are not easily generalizable. When N fertilizer affects N 2O emissions during a subsequent unfertilized crop, it will be important to determine if total fertilizer-induced N 2O emissions are altered or only spread across a greater period of time.
  • Authors:
    • Woodward, R.
    • Jones, M.
    • Stoller, J.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 1
  • Year: 2015
  • Summary: Spatial variation from soil and related factors often affects the outcome of agronomic field experiments. The randomized complete block (RCB) is the most prevalent design despite inefficiencies that can result in inflated error terms. Experimental designs such as the Latin square (LS) allow for bidirectional blocking and offer the potential to account for spatial variability better. The objectives of this research were to investigate the occurrence of two-way gradients in agronomic field trials and compare the estimated relative efficiency (ERE) of a LS to a RCB. Thirty LS trials were evaluated in 10 states during 2013 across the midwestern United States investigating crop yields of corn ( Zea mays L.), soybean [ Glycine max (L.) Merr.], and sorghum [ Sorghum bicolor (L.) Moench]. The results show that 47% of the trials exhibited a two-way gradient, indicating this characteristic is widespread across a large geographic region. Overall, the ERE was increased in 70% of the trials by using the LS design. A lower ERE occurred in 7% of the trials conducted using a LS. Multiple gradients appear common in agronomic field plot trials and enough variation existed between the two blocking directions to justify the use of a LS design. Our data indicate the LS offers a low risk, high reward option of experimental design for controlling spatial heterogeneity and increasing precision. When possible, the LS design should be used in field experiments where the trial area appears uniform and gradients to block against are not obvious.
  • 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:
    • Freycon, V.
    • Laumonier, Y.
    • Locatelli, B.
    • Labriere, N.
    • Bernoux, M.
  • Source: Agricultural Journal
  • Volume: 203
  • Year: 2015
  • Summary: Healthy soils provide a wide range of ecosystem services. But soil erosion (one component of land degradation) jeopardizes the sustainable delivery of these services worldwide, and particularly in the humid tropics where erosion potential is high due to heavy rainfall. The Millennium Ecosystem Assessment pointed out the role of poor land-use and management choices in increasing land degradation. We hypothesized that land use has a limited influence on soil erosion provided vegetation cover is developed enough or good management practices are implemented. We systematically reviewed the literature to study how soil and vegetation management influence soil erosion control in the humid tropics. More than 3600 measurements of soil loss from 55 references covering 21 countries were compiled. Quantitative analysis of the collected data revealed that soil erosion in the humid tropics is dramatically concentrated in space (over landscape elements of bare soil) and time (e.g. during crop rotation). No land use is erosion-prone per se, but creation of bare soil elements in the landscape through particular land uses and other human activities (e.g. skid trails and logging roads) should be avoided as much as possible. Implementation of sound practices of soil and vegetation management (e.g. contour planting, no-till farming and use of vegetative buffer strips) can reduce erosion by up to 99%. With limited financial and technical means, natural resource managers and policy makers can therefore help decrease soil loss at a large scale by promoting wise management of highly erosion-prone landscape elements and enhancing the use of low-erosion-inducing practices.
  • Authors:
    • Wang, X.
    • Zhang, T.
    • Liu, J.
    • Ding, C.
    • Li, X.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 1
  • Year: 2015
  • Summary: Peanut ( Arachis hypogaea L.) yield and quality are seriously compromised by consecutive monoculturing in southeastern China. This work investigated the population size and community structure of soil nematodes in 3-, 6-, and 20-yr-old peanut monoculturing systems. A grass pasture was used as the control. The results showed that continuous peanut monocropping had detrimental effects on the soil nematode abundance and functional composition compared with the control. The reductions in the abundance of total and microbivorous nematodes with increasing years of monocropping are likely to reduce bioturbation and nutrient mineralization, and an elevated abundance of plant parasitic nematodes may result in serious damage to peanut roots, thus aggravating root rot. Furthermore, the significant variations in soil nematode functional indices across the three monocropped peanut fields may produce negative effects on sustainable agroecosystems. Our study also contributes to the identification of locally applicable indicator species of soil nematodes, i.e., Tylenchus, Doryllium, and Mesorhabditis, which can be applied in the assessment of soil status within monocropped peanut fields. Our results suggest that the soil nematode community exhibits evident responses to peanut monocropping.
  • Authors:
    • Zheng, X.
    • Wang, K.
    • Yao, Z.
    • Liu, C.
  • Source: Science Article
  • Volume: 203
  • Year: 2015
  • Summary: Global nitrogen fertilizer consumption is expected to continue to increase. To explore effective mitigation strategies, a deeper understanding of the responses of nitrogen use efficiency, nitric oxide (NO) emission and the NO direct emission factor (EF d) to increasing fertilization rates is needed. A gradient of fertilization rates (0, 135, 270, 430, 650 and 850 kg N ha -1 yr -1 in the form of urea, hereafter referred to as N0, N135, N270, N430, N650 and N850, respectively) was used to fully represent the nitrogen application levels in the wheat-maize rotational cropping system that has been widely adopted in China. The annual NO emissions ranged from 0.430.04 (N0) to 2.640.35 kg N ha -1 yr -1 (N850) and linearly increased with increasing fertilization rates ( P<0.01). The high pH and low carbon availability in the calcareous soil limited NO production; thus, low EF d values (0.26-0.36%) were observed. The partial factor productivity of applied nitrogen (PFP N) rapidly decreased with increasing fertilization rates; the relationship could be characterized by a rectangular hyperbolic function ( P<0.01). The expected trade-off between EF d and PFP N was not observed. The on-farm PFP N was only 333 kg grain kg -1 N (N430), highlighting the necessity of optimizing current management strategies. Based on a review of previous studies, a comprehensive optimized management strategy is recommended to obtain the maximum benefits for multiple goals of a wheat-maize cropping system. However, consecutive field observations and model studies are still needed to validate the long-term effects of this management strategy.
  • Authors:
    • Salgado-Garcia, S.
    • Aguirre-Rivera, J. R.
    • Ortiz-Ceballos, A. I.
    • Ortiz-Ceballos, G.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 1
  • Year: 2015
  • Summary: In Central America, the traditional cropping system milpa de ano (summer season) and tornamilpa (winter season) were compared over 3 yr (2007-2009). Our experimental objectives were to measure the performance of a maize ( Zea mays L.)-velvet bean [ Mucuna pruriens (L.) DC. subsp. utilis (Wight) Burck] milpa system throughout the summer and winter cultivation, to detect any problems associated with velvet bean use, and to determine the contribution of this tropical legume to soil fertility and maize productivity. In each crop season (separated in space and time) we used a completely randomized design with a 2*2 factorial arrangement of treatments with five repetitions each: without velvet bean and without fertilizer (-V-F), with velvet bean and without fertilizer (+V-F), without velvet bean and with fertilizer (-V+F), and with velvet bean and with fertilizer (+V+F). Results showed that in the winter milpas the presence of velvet bean significantly increased the soil pH, organic matter content, total N, and decreased soil bulk density. In both cycles (winter and summer), treatment with velvet bean (+V) produced higher grain yield, while the treatment without velvet bean (-V) had a lower production. We concluded that the use of velvet bean in the winter milpa contributed to the restoration of soil fertility and increased yield maize in agricultural systems of the small-holder farmers based on low external input.
  • Authors:
    • Baruah, K. K.
    • Bhattacharya, S. S.
    • Saikia, J.
  • Source: Journal
  • Volume: 203
  • Year: 2015
  • Summary: Management of soil in agricultural ecosystem is considered to be important in maintaining soil health and soil carbon storage. Various combinations of inorganic fertilizers, FYM and crop residues were assessed in a wheat crop grown in alluvial soil for two consecutive years. We studied several attributes like soil organic carbon (SOC), soil total carbon (TC), soil carbon storage (SCS), soil moisture content (SMC), easily mineralizable N along with above ground and below ground biomass, photosynthetic rate and grain yields during various growth stages. Wheat biomass yield was increased with application of organic amendments, while carbon assimilation by plant photosynthesis during the reproductive stages enhanced with increment of SOC. We recorded about ~10.88% and 10.52% organic SCS in soil depth of 0-15 cm and about ~11.50% and 12.46% in soil depth of 15-30 cm under 100% NPK + CR + FYM and 80% NPK + CR + FYM treatments, respectively. Hence, CR and FYM in combination can maintain SOC stock considerably and 80% NPK + CR + FYM substitutes 20% inorganic fertilizer without compromising crop growth and development.
  • Authors:
    • Rey,A.
  • Source: Article
  • Volume: 21
  • Issue: 5
  • Year: 2015
  • Summary: Widespread recognition of the importance of soil CO 2 efflux as a major source of CO 2 to the atmosphere has led to active research. A large soil respiration database and recent reviews have compiled data, methods, and current challenges. This study highlights some deficiencies for a proper understanding of soil CO 2 efflux focusing on processes of soil CO 2 production and transport that have not received enough attention in the current soil respiration literature. It has mostly been assumed that soil CO 2 efflux is the result of biological processes (i.e. soil respiration), but recent studies demonstrate that pedochemical and geological processes, such as geothermal and volcanic CO 2 degassing, are potentially important in some areas. Besides the microbial decomposition of litter, solar radiation is responsible for photodegradation or photochemical degradation of litter. Diffusion is considered to be the main mechanism of CO 2 transport in the soil, but changes in atmospheric pressure and thermal convection may also be important mechanisms driving soil CO 2 efflux greater than diffusion under certain conditions. Lateral fluxes of carbon as dissolved organic and inorganic carbon occur and may cause an underestimation of soil CO 2 efflux. Traditionally soil CO 2 efflux has been measured with accumulation chambers assuming that the main transport mechanism is diffusion. New techniques are available such as improved automated chambers, CO 2 concentration profiles and isotopic techniques that may help to elucidate the sources of carbon from soils. We need to develop specific and standardized methods for different CO 2 sources to quantify this flux on a global scale. Biogeochemical models should include biological and non-biological CO 2 production processes before we can predict the response of soil CO 2 efflux to climate change. Improving our understanding of the processes involved in soil CO 2 efflux should be a research priority given the importance of this flux in the global carbon budget.
  • Authors:
    • Strzepek, K.
    • Schlosser, A.
  • Source: Article
  • Volume: 130
  • Issue: 1
  • Year: 2015
  • Summary: Projections of regional changes in surface-air temperature and precipitation, in response to unconstrained emissions as well as a climate mitigation policy, for the Zambezi River Basin (ZRB) are presented. These projections are cast in a probabilistic context through a hybrid technique that combines the projections of the MIT Integrated Global System Model (IGSM) to pattern-change kernels from climate-model results of the Coupled Model Intercomparison Project (CMIP). Distributional changes of precipitation and surface-air temperature averaged over the western and eastern ZRB are considered. Overall, the most significant response to climate policy is seen in the spring. Frequency distributions of precipitation change for the unconstrained emission scenario indicate a majority of the outcomes to be drier by 2050, although the distribution spans both increased and decreased precipitation. Through climate policy, the distributions' total range of outcomes collapses considerably, and perhaps more importantly, the mode of the distribution aligns with zero precipitation change. For surface-air temperature, climate policy consistently reduces the modal value of warming, and this reduction is strongest for the western ZRB. Climate policy also considerably abates the occurrence of the most extreme temperature increases, but the minimum warming in the distributions is less affected.