• Authors:
    • Strzepek, K.
    • McCluskey, A.
    • Gebretsadik, Y.
    • Fant, C.
  • Source: Article
  • Volume: 130
  • Issue: 1
  • Year: 2015
  • Summary: Many residents of the Zambezi River Valley are dependent on water-related resources. Greenhouse gas (GHG) emissions may cause a significant change to the climate in the Zambezi Basin in the future, but there is much uncertainty about the future climate state. This situation leaves policy makers at a state of urgency to prepare for these changes as well as reduce the impacts of the changes through GHG mitigation strategies. First and foremost, we must better understand the economic sectors most likely impacted and the magnitude of those impacts, given the inherent uncertainty. In this study, we present a suite of models that assess the effects of climate change on water resources for four countries in the Zambezi basin: Malawi, Mozambique, Zambia, and Zimbabwe. We use information from a large ensemble (6800) of climate scenarios for two GHG emission policies which represent a distribution of impacts on water-related sectors, considering emissions uncertainty, climate sensitivity uncertainty, and regional climate uncertainty. Two GHG mitigation scenarios are used to understand the effect of global emissions reduction on the River Basin system out to 2050. Under both climate polices, the majority of the basin will likely be drier, except for a portion in the north around Malawi and northern Zambia. Three Key Performance Indicators are used-flood occurrence, unmet irrigation demand, and hydropower generation-to understand the impact channels of climate change effects on the four countries. We find that floods are likely to be worse in Mozambique, irrigation demands are likely to be unmet in Mozambique and Zimbabwe, and hydropower generation is likely to be reduced in Zambia. We also find that the range of possible impacts is much larger under an unconstrained GHG emissions case than under a strict mitigation strategy, suggesting that GHG mitigation would reduce uncertainties about the future climate state, reducing the risks of extreme changes as compared to the unconstrained emissions case.
  • 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:
    • Wambua, J. M.
    • Mungube, E. O.
    • Njiru, E. N.
    • Gatheru, M.
    • Gichangi, E. M.
    • Wamuongo, J. W.
  • Source: Article
  • Volume: 130
  • Issue: 2
  • Year: 2015
  • Summary: A study was conducted to investigate the intra-seasonal climate variability and change in semi-arid eastern Kenya and also assessed the ability of the households to discern trends in climate and how the perceived trends converge with actual long term weather observations. The study utilised long term climatic data and data collected through interviews of 200 households using a structured questionnaire. The survey data was analysed through descriptive statistics using the Statistical Package for Social Sciences (SPSS) version 12.0. The results of long term climatic data indicated high year-to-year variation in seasonal rainfall with 49.0% and 58% negative anomalies observed in the long and short rainfall seasons respectively. No discernible increasing or decreasing trend in the long- seasonal rainfall was observed over the period of study. However, Long-term temperature data showed high year-to-year variation in annual mean maximum and minimum temperatures with maximum temperature increasing during the period. Long term rainfall data (51 years) showed that 31.4 and 35.3% of the long rains would be classified as good and failed seasons respectively, with the remaining percentage classified as moderate seasons. For the short rains, 15.7 and 43.1 % would be classified as good and failed seasons respectively, with the remaining percentage classified as moderate seasons. Farmers interviewed were able to recollect the past seasons fairly accurately especially the 'good' and 'failed' seasons which corroborated well with the meteorological records. Indigenous knowledge on weather forecasting was reported by 81% of farmers to be helpful in farming decision making especialy on the types of crops to be planted. A better understanding of farmers' perceptions of climate change, ongoing adaptation measures, and the decision-making process would important to inform policies aimed at promoting sustainable adaptation of the agricultural sector.
  • Authors:
    • Olesen, J. E.
    • Munkholm, L. J.
    • Hansen, E. M.
    • Melander, B.
  • Source: Agronomy Journal
  • Volume: 44
  • Issue: 3
  • Year: 2015
  • Summary: Crop management factors, such as tillage, rotation, and straw retention, need to be long-term to allow conclusions on effects on crop yields, nitrate leaching, and carbon sequestration. In 2002, two field experiments, each including four cash crop rotations, were established on soils with 9 and 15% clay, under temperate, coastal climate conditions. Direct drilling and harrowing to two different depths were compared to plowing with respect to yield, nitrate N leaching, and carbon sequestration. For comparison of yields across rotations, grain and seed dry matter yields for each crop were converted to grain equivalents (GE). Leaching was compared to yields by calculating yield-scaled leaching (YSL, g N kg -1 GE), and N balances were calculated as the N input in manure minus the N output in products removed from the fields. Direct drilling reduced yields, but no effect on leaching was found. Straw retention did not significantly increase yields, nor did it reduce leaching, while fodder radish ( Raphanus sativus L.) as a catch crop was capable of reducing nitrate leaching to a low level. Thus, YSL of winter wheat ( Triticum aestivum L.) was higher than for spring barley ( Hordeum vulgare L.) grown after fodder radish due to the efficient catch crop. Soil organic carbon (SOC) did not increase significantly after 7 yr of straw incorporation or noninversion tillage. There was no correlation between N balances calculated for each growing season and N leaching measured in the following percolation period.
  • 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:
    • Biscaia, R. C. M.
    • Araújo, A. G.
    • Merten, G. H.
    • Barbosa, G. M. C.
    • Conte, O.
  • Source: Article
  • Volume: 152
  • Year: 2015
  • Summary: No-till is widely used to control soil erosion in agricultural areas in Brazil and is currently practiced on about 30. Mha. However, studies have shown that no-till is not as efficient in controlling surface runoff losses as it is in reducing soil loss. The objective of this study is to evaluate soil and surface runoff losses on small and large plots with differing slope lengths, cropping sequences and tillage systems in southern Brazil. Surface runoff and soil losses under natural rainfall erosion plots (3.5. ×. 11. m, 3.5. ×. 22. m, 50. ×. 100. m, and 100. ×. 100. m) were evaluated in two experiments in a well-drained Oxisol (>60% clay) with 9% and 7% slopes, respectively. The experiment extended over 14 years comparing 4 different soil management systems: (a) bare soil plots with slope length 22. m; (b) bare soil plots with slope length 11. m; (c) sequence of wheat (Triticum aestivum)/soybean [. Glycine max (L.) Merr] with disk plow. +. lighter off-set disk-harrow (DP+LD); and (d) sequence of wheat/soybean under no-till (NT). In another experiment using large field plots, three soil tillage regimens (DP. +. LD; heavy off-set disk-harrow. +. lighter off-set disk-harrow (HD. +. LD), and NT) were compared over the course of a 5-yr. crop sequence of black oats (Avena estrigosa)/soybean-black oats/corn (Zea mays L.)-wheat/soybean- black oats/soybean -blue lupine (Lupinus angustifolium)/corn. Results for both experiments show that, when compared with conventional soil tillage (DP. +. LD or HD. +. LD), soil losses for NT were >. 70% lower. However, the benefit of reduced surface runoff losses was less evident, suggesting the need to implement additional practices to control surface runoff to avoid transport of pollutants to waterways. © 2015 Elsevier B.V.
  • Authors:
    • Keeton, W. S.
    • Mika, A. M.
  • Source: Research Article
  • Volume: 7
  • Issue: 3
  • Year: 2015
  • Summary: The long-term greenhouse gas emissions implications of wood biomass ('bioenergy') harvests are highly uncertain yet of great significance for climate change mitigation and renewable energy policies. Particularly uncertain are the net carbon (C) effects of multiple harvests staggered spatially and temporally across landscapes where bioenergy is only one of many products. We used field data to formulate bioenergy harvest scenarios, applied them to 362 sites from the Forest Inventory and Analysis database, and projected growth and harvests over 160 years using the Forest Vegetation Simulator. We compared the net cumulative C fluxes, relative to a non-bioenergy baseline, between scenarios when various proportions of the landscape are harvested for bioenergy: 0% (non-bioenergy); 25% (BIO25); 50% (BIO50); or 100% (BIO100), with three levels of intensification. We accounted for C stored in aboveground forest pools and wood products, direct and indirect emissions from wood products and bioenergy, and avoided direct and indirect emissions from fossil fuels. At the end of the simulation period, although 82% of stands were projected to maintain net positive C benefit, net flux remained negative (i.e., net emissions) compared to non-bioenergy harvests for the entire 160-year simulation period. BIO25, BIO50, and BIO100 scenarios resulted in average annual emissions of 2.47, 5.02, and 9.83 Mg C ha -1, respectively. Using bioenergy for heating decreased the emissions relative to electricity generation as did removing additional slash from thinnings between regeneration harvests. However, all bioenergy scenarios resulted in increased net emissions compared to the non-bioenergy harvests. Stands with high initial aboveground live biomass may have higher net emissions from bioenergy harvest. Silvicultural practices such as increasing rotation length and structural retention may result in lower C fluxes from bioenergy harvests. Finally, since passive management resulted in the greatest net C storage, we recommend designation of unharvested reserves to offset emissions from harvested stands.
  • Authors:
    • Kanninen, M.
    • Negash, M.
  • Source: Article
  • Volume: 203
  • Year: 2015
  • Summary: The fifth assessment report of the intergovernmental panel on climate change (IPCC) estimated that by 2040 agroforestry would offer high potential of carbon (C) sequestration in developing countries. However, the role of tropical agroforestry in C sequestration and in climate change mitigation has only recently been recognized by United Nations Framework Convention on Climate Change (UNFCCC). This is partly due to the lack of reliable estimates on the sequestration potential in biomass and soil carbon pools over time. The aim of this study was to analyze the changes in the biomass and soil carbon pools of three indigenous agroforestry systems in south-eastern Rift Valley escrapment of Ethiopia using CO2FIX (v. 3.2) model. The agroforestry systems studied were Enset ( Ensete ventricosum)-tree, Enset-coffee-tree, and Tree-coffee systems. To run the model, empirical data collected from 60 farms (20 farms for each agroforestry system) and literature were used as inputs to parameterize the model. Simulations were run over a period of 50 years. Average simulated total biomass C stocks was the highest for Tree-coffee system (122 Mg C ha -1), followed by the Enset-coffee-tree (114 Mg C ha -1) and Enset-tree system (76 Mg C ha -1). The tree cohort accounted for 89-97% of the total biomass C stocks in all the studied systems, and the reminder was shared by Enset and coffee cohorts. The total average simulated total C stocks (biomass and soil) were 209, 286 and 301 Mg C ha -1 for Enset-tree, Enset-coffee-tree and Tree-coffee systems, respectively. The soil organic carbon (SOC) stocks accounted for 60-64% of the total carbon in the studied systems. Model validation results showed that long-term (10-40 years) simulated biomass C stocks were within the range of measured biomass C stocks for Enset-tree and Enset-coffee-tree systems, but significantly differed for the Tree-coffee system. The simulated soil and total C stocks were within the range of measured values for all the three systems. The CO2FIX model accurately predicted the SOC and total C stocks in the studied indigenous agroforestry systems, but the prediction of the biomass C stocks could be improved by acquiring more accurate input parameter values for running the model.
  • Authors:
    • Kovacs, P.
    • Omonode, R. A.
    • Vyn, T. J.
  • Source: Article
  • Volume: 107
  • Issue: 2
  • Year: 2015
  • Summary: Precision-guided technologies enable corn ( Zea mays L.) growers to apply pre-plant anhydrous ammonia (NH 3) parallel to intended corn rows even when full-width tillage follows NH 3 application. Close, but crop-safe, proximity of NH 3 to corn rows may potentially increase N use efficiency and lower N requirements and nitrous oxide (N 2O) emissions. Experiments in 2011 and 2012 on silty clay loam Mollisol near West Lafayette, IN, assessed area- and yield-scaled N 2O emissions when spring pre-plant NH 3 was applied at recommended (202 kg N ha -1) and reduced rate (145 kg N ha -1), in no-till (NT) and conventional tillage (CT) systems following NT soybean [ Glycine max (L.) Merr.]. Each 12-cm deep NH 3 band was positioned 15 cm from, and parallel to, intended corn rows using precision guidance. Nitrification of NH 3 in application bands was 31% faster under CT than NT. Area- and grain yield-scaled N 2O emissions were N rate dependent in both growing seasons. On average, CT+202 kg N resulted in highest area-scaled (mean=2.45 kg N ha -1) and grain yield-scaled (mean=360 g N Mg -1) N 2O emissions. In contrast, CT+145 kg N had similar yield-scaled emissions as NT+202 and NT+145 kg N, and reduced area-scaled N 2O emissions by 65, 45, and 19% respectively, relative to CT+202 kg N, NT+202 kg N, and NT+145 kg N treatments. These preliminary results suggest that reducing pre-plant NH 3 rates by ~30% under CT has the potential to reduce N 2O emissions without significant yield declines in the CT phase of a NT-CT rotation, despite faster nitrification in CT.
  • 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.