• Authors:
    • Antille,D. L.
    • Chamen,W. C. T.
    • Tullberg,J. N.
    • Lal,R.
  • Source: Transactions of the ASABE
  • Volume: 58
  • Issue: 3
  • Year: 2015
  • Summary: The drive toward adoption of conservation agriculture to reduce costs and increase production sustainably causes concern due to the potentially negative effects of increased soil compaction. Soil compaction reduces aeration, water infiltration, and saturated hydraulic conductivity and increases the risk of waterlogging. Controlled traffic farming (CTF) is a system in which: (1) all machinery has the same or modular working and track width so that field traffic can be confined to the least possible area of permanent traffic lanes, (2) all machinery is capable of precise guidance along those permanent traffic lanes, and (3) the layout of the permanent traffic lanes is designed to optimize surface drainage and logistics. Without CTF, varying equipment operating and track widths translate into random traffic patterns, which can cover up to 85% of the cultivated field area each time a crop is produced. Nitrous oxide (N2O) is the greatest contributor to agriculture's greenhouse gas (GHG) emissions from cropping, and research suggests that its production increases significantly under conditions of high (>60%) water-filled porosity when nitrate (mainly from fertilizer N) and carbon (usually from crop residues) are available. Self-amelioration of soils affected by compaction occurs slowly from the surface downward; however, the rate of amelioration decreases with increase in depth. Consequently, all soils in non-CTF systems in mechanized agriculture are prone to some degree of compaction, which compromises water infiltration, increases the frequency and duration of waterlogged conditions, reduces gaseous exchange between soil and the atmosphere, inhibits root penetration and exploitation of nutrients and water in the subsoil, and enhances N2O emissions. Adoption of CTF increases soil porosity in the range of 5% to 70%, water infiltration by a factor of 4, and saturated hydraulic conductivity by a factor of 2. The greater cropping opportunity and enhanced crop growth for given fertilizer and rainfall inputs offered by CTF, coupled with no-tillage, provide potential for enhanced soil carbon sequestration. Reduced need and intensity of tillage, where compaction is avoided, also helps protect soil organic matter in stable aggregates, which may otherwise be exposed and oxidized. There is both circumstantial and direct evidence to suggest that improved soil structural conditions and aeration offered by CTF can reduce N2O emissions by 20% to 50% compared with non-CTF. It is not compaction per se that increases the risk of N2O emissions but rather the increased risk of waterlogging and increase in water-filled pore space. There may be an elevated risk of GHG emissions from the relatively small area of permanent traffic lanes (typically <20% of total cultivated area) if these are not managed appropriately. Quantification of the benefits of compaction avoidance in terms of GHG emissions may be possible through the use of well-developed models. © 2015 American Society of Agricultural and Biological Engineers.
  • Authors:
    • Bagley,Justin E.
    • Miller,Jesse
    • Bernacchi,Carl J.
  • Source: Plant Cell Environment
  • Volume: 38
  • Issue: 9
  • Year: 2015
  • Summary: The potential impacts of climate change in the Midwest United States present unprecedented challenges to regional agriculture. In response to these challenges, a variety of climate-smart agricultural methodologies have been proposed to retain or improve crop yields, reduce agricultural greenhouse gas emissions, retain soil quality and increase climate resilience of agricultural systems. One component that is commonly neglected when assessing the environmental impacts of climate-smart agriculture is the biophysical impacts, where changes in ecosystem fluxes and storage of moisture and energy lead to perturbations in local climate and water availability. Using a combination of observational data and an agroecosystem model, a series of climate-smart agricultural scenarios were assessed to determine the biophysical impacts these techniques have in the Midwest United States. The first scenario extended the growing season for existing crops using future temperature and CO2 concentrations. The second scenario examined the biophysical impacts of no-till agriculture and the impacts of annually retaining crop debris. Finally, the third scenario evaluated the potential impacts that the adoption of perennial cultivars had on biophysical quantities. Each of these scenarios was found to have significant biophysical impacts. However, the timing and magnitude of the biophysical impacts differed between scenarios. This study assessed the biophysical impacts of several climate-smart agricultural practices in the Midwest United States. Specifically we investigated the biophysical impacts of adapting crops to extended growing season length, expanding no-till agriculture, and the adoption of perennial cultivars. We found that each of these practices had significant biophysical impacts, but the seasonality and extent of the impacts differed between scenarios.
  • Authors:
    • Eleto Torres,Carlos M. M.
    • Kohmann,Marta M.
    • Fraisse,Clyde W.
  • Source: Agricultural Systems
  • Volume: 137
  • Year: 2015
  • Summary: Agriculture is an important source of greenhouse gases (GHG), especially from crop production practices and enteric fermentation by ruminant livestock. Improved production practices in agriculture and increase in terrestrial carbon sinks are alternatives for mitigating GHG emissions in agriculture. The objective of this study was to estimate GHG emissions from hypothetical farm enterprise combinations in the southeastern United States with a mix of cropland and livestock production and estimate the area of forest plantation necessary to offset these emissions. Four different farm enterprise combinations (Cotton; Maize; Peanut; Wheat + Livestock + Forest) with different production practices were considered in the study resulting in different emission scenarios. We assumed typical production practices of farm operations in the region with 100 ha of cropland area and a herd of 50 cows. GHG emissions were calculated regarding production, storage and transportation of agrochemicals (pre-farm) and farm activities such as fertilization, machinery operation and irrigation (on-farm). Simulated total farm GHG emissions for the different farm enterprise combinations and production practices ranged from 348.8 t CO(2)e year(-1) to 765.6 t CO(2)e year(-1). The estimated forest area required to neutralize these emissions ranged from 19 ha to 40 ha. In general, enterprise combinations with more intense production practices that include the use of irrigation resulted in higher total emissions but lower emissions per unit of commodity produced. (C) 2015 Elsevier Ltd. All rights reserved.
  • Authors:
    • Feng ZhaoZhong
    • Rutting,T.
    • Pleijel,H.
    • Wallin,G.
    • Reich,P. B.
    • Kammann,C. I.
    • Newton,P. C. D.
    • Kobayashi,K.
    • Luo YunJian
    • Uddling,J.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 8
  • Year: 2015
  • Summary: A key part of the uncertainty in terrestrial feedbacks on climate change is related to how and to what extent nitrogen (N) availability constrains the stimulation of terrestrial productivity by elevated CO 2 (eCO 2), and whether or not this constraint will become stronger over time. We explored the ecosystem-scale relationship between responses of plant productivity and N acquisition to eCO 2 in free-air CO 2 enrichment (FACE) experiments in grassland, cropland and forest ecosystems and found that: (i) in all three ecosystem types, this relationship was positive, linear and strong ( r2=0.68), but exhibited a negative intercept such that plant N acquisition was decreased by 10% when eCO 2 caused neutral or modest changes in productivity. As the ecosystems were markedly N limited, plants with minimal productivity responses to eCO 2 likely acquired less N than ambient CO 2-grown counterparts because access was decreased, and not because demand was lower. (ii) Plant N concentration was lower under eCO 2, and this decrease was independent of the presence or magnitude of eCO 2-induced productivity enhancement, refuting the long-held hypothesis that this effect results from growth dilution. (iii) Effects of eCO 2 on productivity and N acquisition did not diminish over time, while the typical eCO 2-induced decrease in plant N concentration did. Our results suggest that, at the decennial timescale covered by FACE studies, N limitation of eCO 2-induced terrestrial productivity enhancement is associated with negative effects of eCO 2 on plant N acquisition rather than with growth dilution of plant N or processes leading to progressive N limitation.
  • Authors:
    • Fumagalli,Mattia
  • Source: Italian Journal of Agrometeorology
  • Volume: 20
  • Issue: 1
  • Year: 2015
  • Summary: Intensive maize production in Lombardy region (northern Italy) is widespread and requires big amounts of input, especially nitrogen (N), thus leading to potential environmental risks. Starting from farm survey data the current work aims to evaluate how alternative N management options for reducing losses can be effective in climate change mitigation. Under current management (ACT) of typical continuous maize cropping systems across the region, the greenhouse gases (GHG) emissions from the production of inorganic fertilisers and from direct and indirect N2O released after N application accounted for, on average, 67% of the total GHG emissions. The adoption of the best N management plans (FERT scenario), reduced GHG emissions and C-footprint (expressed per unit of agricultural product) by 27 and 26%, respectively. Furthermore, the double cropping system (two crops harvested in 12 months - ROT scenario) strongly increased GHG emissions in comparison with the only cultivation of a summer crop. However, the high productivity of this system, led to a C-footprint lower than the ACT one and still higher than the FERT one. The current work highlights the opportunities for carbon mitigation offered by changes on field N management, without significantly impact the yield.
  • Authors:
    • Irani,S.
    • Majidi,M. M.
    • Mirlohi,A.
    • Zargar,M.
    • Karami,M.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: The physiological basis of genetic variation in drought response and its association with forage yield and drought tolerance indices is not clear in sainfoin ( Onobrychis viciifolia Scop.). In this study, 100 sainfoin genotypes from 10 ecotypes were clonally propagated and evaluated under non-stressed and water deficit conditions during 2 yr. Physiological traits including chlorophyll a, chlorophyll b, total chlorophyll, carotenoid content, proline content, relative water content (RWC), catalase (CAT), ascorbate peroxidase (APX), superoxide dismutase (SOD) activity, dry matter yield (DMY), and stress tolerance index (STI) were studied. Large genotypic variation was observed among ecotypes for most of the studied traits indicating that selection in this germplasm would be useful. The results showed that water deficit greatly influenced physiological traits that affected forage production. Water deficit decreased DMY and RWC while significantly increasing carotenoid content, free proline content, CAT, APX, and SOD activity in both years. The relationship between dry matter yield and STI with proline content showed that ecotypes with high DMY and STI under water deficit conditions had higher proline accumulation in their leaves. With regard to the STI and principal component analysis (PCA), ecotypes Baft, Najafabad, and Sirjan were found to be drought tolerant or moderately drought tolerant. These ecotypes showed significantly higher values for proline content under water deficit conditions.
  • Authors:
    • Jani,Arun D.
    • Grossman,Julie M.
    • Smyth,Thomas J.
    • Hu,Shuijin
  • Source: Plant and Soil
  • Volume: 393
  • Issue: 1-2
  • Year: 2015
  • Summary: Legume cover crops are primarily grown for their contribution to soil N pools, but the effect that this added N has on cover crop root decomposition and N release is poorly understood. Our primary objective was to determine the effect that soil N and root diameter size have on root decomposition and N release. We determined coarse (> 1-mm diameter) and fine (< 1-mm diameter) root distribution for crimson clover (Trifolium incarnatum) and hairy vetch (Vicia villosa Roth) using greenhouse-grown plants, and followed with a 12-week incubation in which coarse and fine roots from both species were incubated under natural and elevated (200 kg ha(-1)) soil N levels. Crimson clover and hairy vetch consisted primarily of fine roots (a parts per thousand yen79 %), which decomposed and released N faster than coarse roots. Soil N addition had a small positive effect on root decomposition, but an inconsistent effect on root N release. There was a net increase in soil inorganic N for all treatments after 12 weeks. These results improved our understanding of decomposition and N release from crimson clover and hairy vetch roots, and are valuable to farmers seeking to better manage soil C and N pools.
  • Authors:
    • Northupl,B. K.
    • Rao,S. C.
  • Source: Crop Economics, Production & Management
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Continuous winter wheat ( Triticum aestivum L. em Thell.) is the foundation for most US Southern Great Plains (SGP) agriculture. Inorganic N fertilizers are important to wheat production, but increasing N prices have caused producers to reconsider growing legumes during summer fallow for green N. This study was conducted during 2008 to 2012 to determine the potential for using lablab [ Lablab purpureus (L.) Sweet cv. Rio Verde] to support wheat under conventional and no-till management compared with soybean [ Glycine max (L.) Merr. cv. Laredo] and three inorganic fertilizer treatments (none, 40, and 80 kg N ha -1). Legume seeds were inoculated and sown after wheat harvest each year, grown from June to August, and terminated in early September. Wheat was then sown with or without preplant tillage and grown to maturity. Grain yield, N concentration, and N accumulated in grain were analyzed to define N treatment, tillage system, and year effects. The amount and distribution of precipitation during 2008 to 2012 varied from 53 to 92% and 63 to 160% of the long-term averages for wheat (688 mm) and legume (162 mm) phases. Tillage effects were nonsignificant ( P<0.76), but N treatment * year interactions were significant for grain yield, N concentration, and N accumulated in grain ( P<0.01). The legumes resulted in some single-year increases in grain yield, but the overall yield response was inconsistent. The legume treatments reduced N concentration in wheat grain compared with the unfertilized control. These results show that neither legume was an effective short-term (≤4-yr) N source for systems of continuous wheat production in the SGP.
  • Authors:
    • Shi,Feng
    • Ge,Quansheng
    • Yang,Bao
    • Li,Jianping
    • Yang,Fengmei
    • Ljungqvist,Fredrik Charpentier
    • Solomina,Olga
    • Nakatsuka,Takeshi
    • Wang,Ninglian
    • Zhao,Sen
    • Xu,Chenxi
    • Fang,Keyan
    • Sano,Masaki
    • Chu,Guoqiang
    • Fan,Zexin
    • Gaire,Narayan P.
    • Zafar,Muhammad Usama
  • Source: Climatic Change
  • Volume: 131
  • Issue: 4
  • Year: 2015
  • Summary: To investigate climate variability in Asia during the last millennium, the spatial and temporal evolution of summer (June-July-August; JJA) temperature in eastern and south-central Asia is reconstructed using multi-proxy records and the regularized expectation maximization (RegEM) algorithm with truncated total least squares (TTLS), under a point-by-point regression (PPR) framework. The temperature index reconstructions show that the late 20th century was the warmest period in Asia over the past millennium. The temperature field reconstructions illustrate that temperatures in central, eastern, and southern China during the 11th and 13th centuries, and in western Asia during the 12th century, were significantly higher than those in other regions, and comparable to levels in the 20th century. Except for the most recent warming, all identified warm events showed distinct regional expressions and none were uniform over the entire reconstruction area. The main finding of the study is that spatial temperature patterns have, on centennial time-scales, varied greatly over the last millennium. Moreover, seven climate model simulations, from the Coupled Model Intercomparison Project Phase 5 (CMIP5), over the same region of Asia, are all consistent with the temperature index reconstruction at the 99 % confidence level. Only spatial temperature patterns extracted as the first empirical orthogonal function (EOF) from the GISS-E2-R and MPI-ESM-P model simulations are significant and consistent with the temperature field reconstruction over the past millennium in Asia at the 90 % confidence level. This indicates that both the reconstruction and the simulations depict the temporal climate variability well over the past millennium. However, the spatial simulation or reconstruction capability of climate variability over the past millennium could be still limited. For reconstruction, some grid points do not pass validation tests and reveal the need for more proxies with high temporal resolution, accurate dating, and sensitive temperature signals, especially in central Asia and before AD 1400.
  • Authors:
    • van Dijl,E. A.
    • Grogan,K. A.
    • Borisova,T.
  • Source: Journal of Soil and Water Conservation
  • Volume: 70
  • Issue: 4
  • Year: 2015
  • Summary: In the United States, Florida ranks second among states for both value and land area of vegetable production, but this production is affected by periodic droughts. Florida has experienced at least one severe and widespread drought every decade since 1900, and climate change projections show that meteorological droughts will occur more often in the future. While drought and climate change affect the supply side, population growth is expected to affect the demand side of water availability. Given these threats to future water availability, the adoption of drought adaptation and water conservation measures is of increasing importance in Florida. Using a 2013 survey of Florida vegetable growers, this paper addresses two main components of this problem. First, we assess the current rates of adoption of drought adaptation measures. Second, we analyze which factors influence or impede the adoption of these measures to provide policy recommendations to increase adoption in the future. We find low rates of adoption of adaptations, ranging from 13% to 55%, and factors determining who adopts a given adaptation vary by adaptation. Factors can have opposite effects on the probability of adoption across different adaptations. Unlike most previous work, we find that growers with more education have lower rates of adoption of water augmentation measures, and lack of land ownership does not necessarily impede adoption of adaptations with large initial investment.