• Authors:
    • Thapa,R.
    • Chatterjee,A.
    • Johnson,J. M. F.
    • Awale,R.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Nitrogen losses associated with fertilizer application have negative economic and environmental consequences, but urease and nitrification inhibitors have potential to reduce N losses. The effectiveness of these inhibitors has been studied extensively in irrigated but not in rainfed systems. This study was conducted at Glyndon, MN, under rainfed conditions to assess the impact of urease and nitrification inhibitors on NH 3 volatilization, N 2O emissions, and NO 3- concentrations below the spring wheat ( Triticum aestivum L.) rooting zone. Urea (U), urea with urease and nitrification inhibitors (SU), and urea with nitrification inhibitor only (UI) were applied at 146 and 168 kg N ha -1 along with the control treatments. Cumulative NH 3 volatilization was reduced by 26%, N 2O emissions measured 18 d after planting were reduced by 50% with SU, but no significant reduction was observed with UI compared to U. We did not observe a significant effect of higher N rate on N 2O emissions, but lower N application rate (146 kg N ha -1) significantly reduced NH 3 volatilization by 26% compared to 168 kg N ha -1. Nitrate concentration below the rooting zone was reduced by applying N at lower rate and also through the use of SU and UI instead of U. Soil inorganic N intensity was significantly related with cumulative N 2O emissions. Nitrogen source and rate did not influence grain yield and protein content. This single-growing season study under rainfed conditions suggests that fertilizer N-stabilizers can be successfully used to minimize N losses without compromising grain yield and protein content.
  • Authors:
    • Vanhie,M.
    • Deen,W.
    • Bohner,H.
    • Hooker,D. C.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Many soybean [ Glycine max (Merr.)] growers in northern climates are reverting back to some tillage based on perceptions that increasing corn residues interfere with no-till (NT) soybean performance. Field trials were established in southern Ontario, Canada, to investigate the impact of corn residues on soybean among seven tillage strategies (NT, stalk chop, vertical tillage (VT) twice in the fall, fall and spring VT, fall disc plus spring cultivate, fall disc plus fall cultivate, and fall plowed plus spring cultivate), three corn residue removal treatments (none, intermediate, and nearly complete), and two planters (row-unit and drill). Overall, soybean yields were not different between NT and plowed systems, despite delayed development, and cooler/wetter seedbeds where corn residue was not removed. Shallow tillage after corn harvest did not increase yields from NT alone. Removal of corn residue did not increase soybean yields when averaged across tillage systems. However, NT yield was lowered by 0.36 Mg ha -1 when corn stalks were chopped in the fall, but only in the drill-planted treatments. This result was significant since many farmers have purchased corn combine heads that chop stalks in an attempt to manage residue. Soybean planted with a row-unit planter yielded 0.13 Mg ha -1 higher compared to a drill when averaged across tillage-residue treatments; differences between planters were higher when contending with high amounts of corn residue or an uneven soil surface at planting. Our results show that shallow tillage and/or physically removing corn residue did not improve soybean yield compared to NT alone.
  • Authors:
    • Wegner,B. R.
    • Kumar,S.
    • Osborne,S. L.
    • Schumacher,T. E.
    • Vahyala,I. E.
    • Eynard,A.
  • Source: Soil Science Society of America Journal
  • Volume: 79
  • Issue: 4
  • Year: 2015
  • Summary: Excessive removal of crop residue has been shown to degrade soil organic carbon (SOC), and hence soil quality. Our objective was to assess the impacts of corn (Zea mays L.) residue removal and cover crops on various soil quality indicators. The experiment was conducted on a silty clay loam soil with and without a cover crop following three residue removal treatments. The low residue removal (LRR) treatment consisted of harvesting corn grain, leaving all other plant materials on the soil surface. Medium residue removal (MRR) consisted of harvesting grain, then chopping, windrowing and baling the remaining residue. The high residue removal (HRR) consisted of cutting the stalks 0.15 m from the ground and removing essentially all above-ground biomass. Crop residue removal significantly impacted measured soil properties including SOC, but cover cropping had minimal effects. The LRR treatment resulted in higher SOC concentrations and increased aggregate stability compared with other treatments. Residue removal significantly impacted the microbial activity as measured by hydrolysis of fluorescein diacetate (FDA). This study confirmed that HRR rates lead to SOC decomposition and adversely affect soil properties and soil quality. Soil conservation and emerging uses for crop residues must be balanced. Therefore, before making any decision to harvest crop residues, it is essential to have accumulated more C in the residue and supplemental cover crops than is needed to maintain equilibrium SOC levels. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA. All rights reserved.
  • Authors:
    • Winchester,N.
    • Reilly,J. M.
  • Source: Energy Economics
  • Volume: 51
  • Year: 2015
  • Summary: What are the feasibility, costs, and environmental implications of large-scale bioenegry? We investigate this question by developing a detailed representation of bioenergy in a global economy-wide model. We develop a scenario with a global carbon dioxide price, applied to all anthropogenic emissions except those from land use change, that rises from $25 per metric ton in 2015 to $99 in 2050. This creates market conditions favorable to biomass energy, resulting in global non-traditional bioenergy production of ~. 150 exajoules (EJ) in 2050. By comparison, in 2010, global energy production was primarily from coal (138 EJ), oil (171 EJ), and gas (106 EJ). With this policy, 2050 emissions are 42% less in our Base Policy case than our Reference case, although extending the scope of the carbon price to include emissions from land use change would reduce 2050 emissions by 52% relative to the same baseline. Our results from various policy scenarios show that lignocellulosic (LC) ethanol may become the major form of bioenergy, if its production costs fall by amounts predicted in a recent survey and ethanol blending constraints disappear by 2030; however, if its costs remain higher than expected or the ethanol blend wall continues to bind, bioelectricity and bioheat may prevail. Higher LC ethanol costs may also result in the expanded production of first-generation biofuels (ethanol from sugarcane and corn) so that they remain in the fuel mix through 2050. Deforestation occurs if emissions from land use change are not priced, although the availability of biomass residues and improvements in crop yields and conversion efficiencies mitigate pressure on land markets. As regions are linked via international agricultural markets, irrespective of the location of bioenergy production, natural forest decreases are largest in regions with the lowest barriers to deforestation. In 2050, the combination of carbon price and bioenergy production increases food prices by 3.2%-5.2%, with bioenergy accounting for 1.3%-3.5%. © 2015.
  • Authors:
    • Banger,Kamaljit
    • Tian,Hanqin
    • Tao,Bo
    • Ren,Wei
    • Pan,Shufen
    • Dangal,Shree
    • Yang,Jia
  • Source: Climatic Change
  • Volume: 132
  • Issue: 4
  • Year: 2015
  • Summary: India is very important but relatively unexplored region in terms of carbon studies, where significant environmental changes have occurred in the 20th century that can alter terrestrial net primary productivity (NPP). Here, we used a process-based, Dynamic Land Ecosystem Model (DLEM), driven by land cover and land use change (LCLUC), climate change, elevated atmospheric CO2 concentration, atmospheric nitrogen deposition (NDEP), and tropospheric ozone (O-3) pollution to estimate terrestrial NPP in India during 1901-2010. Over the country, terrestrial NPP showed significant inter-annual variations ranging 1.2 Pg C year(-1) to 1.7 Pg C year(-1) during the 1901-2010. Overall, multiple environmental changes have increased terrestrial NPP by 0.23 Pg C year(-1). Elevated atmospheric CO2 concentration has increased NPP by 0.29 Pg C; however climate change has offset a portion of terrestrial NPP (0.11 Pg C) during this study period. On an average, terrestrial NPP reduced by 0.12 Pg C year(-1) in drought years; when precipitation was 100 mm year(-1) lower than long term average, suggesting that terrestrial carbon cycle in India is strongly linked to climate change. LCLUC, including land conversions and cropland management practices, increased terrestrial NPP by 0.043 Pg C year(-1) over the country. Tropospheric O-3 pollution reduced terrestrial NPP by 0.06 Pg C year(-1) and the decrease was comparatively higher in croplands than other biomes after the 1980s. Our results have shown that climate change and tropospheric O-3 pollution may partially offset terrestrial NPP increase caused by elevated CO2 concentration, LCLUC, and NDEP over India.
  • Authors:
    • Guillaume,T.
    • Damris,M.
    • Kuzyakov,Y.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 9
  • Year: 2015
  • Summary: Indonesia lost more tropical forest than all of Brazil in 2012, mainly driven by the rubber, oil palm, and timber industries. Nonetheless, the effects of converting forest to oil palm and rubber plantations on soil organic carbon (SOC) stocks remain unclear. We analyzed SOC losses after lowland rainforest conversion to oil palm, intensive rubber, and extensive rubber plantations in Jambi Province on Sumatra Island. The focus was on two processes: (1) erosion and (2) decomposition of soil organic matter. Carbon contents in the Ah horizon under oil palm and rubber plantations were strongly reduced up to 70% and 62%, respectively. The decrease was lower under extensive rubber plantations (41%). On average, converting forest to plantations led to a loss of 10 Mg C ha -1 after about 15 years of conversion. The C content in the subsoil was similar under the forest and the plantations. We therefore assumed that a shift to higher delta 13C values in plantation subsoil corresponds to the losses from the upper soil layer by erosion. Erosion was estimated by comparing the delta 13C profiles in the soils under forest and under plantations. The estimated erosion was the strongest in oil palm (358 cm) and rubber (3310 cm) plantations. The 13C enrichment of SOC used as a proxy of its turnover indicates a decrease of SOC decomposition rate in the Ah horizon under oil palm plantations after forest conversion. Nonetheless, based on the lack of C input from litter, we expect further losses of SOC in oil palm plantations, which are a less sustainable land use compared to rubber plantations. We conclude that delta 13C depth profiles may be a powerful tool to disentangle soil erosion and SOC mineralization after the conversion of natural ecosystems conversion to intensive plantations when soils show gradual increase of delta 13C values with depth.
  • Authors:
    • Karasawa,Toshihiko
    • Takahashi,Shigeru
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 103
  • Issue: 1
  • Year: 2015
  • Summary: Field experiments were conducted to clarify whether the introduction of several cover crop species increases P uptake of the following wheat and soybean. Four summer cover crops (sorghum, buckwheat, groundnut and crotalaria) and four winter cover crops (oat, rye, vetch and lupin) were tested. Growth and P uptake of succeeding wheat were significantly increased by P fertilizer application and tended to be increased by sorghum, groundnut or crotalaria incorporation, whereas buckwheat did not show positive effects. Growth and P uptake of succeeding soybean were significantly increased by oat or vetch incorporation and tended to be increased by P fertilizer or other cover crop incorporation. These positive effects of cover crops were attributed to the large amount of P incorporation, increase in the P-solubilizing fungal population and/or biomass P in soil. Sorghum, oat, rye and vetch were thought to be suitable cover crops to accelerate P uptake of the following crops since a large amount of P would be incorporated. Sorghum, groundnut and lupin were thought to be suitable cover crops because they increased the indigenous P-solubilizing fungal population in soil. Soil biomass P correlated with P uptake of wheat. Incorporation of suitable cover crops as a P source and activation of indigenous soil microorganisms by the carbon supply were thought to have accelerated P uptake of the following wheat and soybean. It is therefore thought that introduction of suitable cover crops could be an effective means to reduce P fertilizer application for the following crops.
  • Authors:
    • Panday,D.
    • Nkongolo,N. V.
  • Source: Procedia Environmental Sciences
  • Volume: 29
  • Year: 2015
  • Summary: Knowledge of the impact of soil and crop management practices on soil processes is important in the study of greenhouse gases emissions from agricultural fields. We assessed the effect of soil air (pore space indices) and water (content, theta; and potential, Psi) on greenhouse gases emissions in corn/soybean field. The study was conducted in 2011 and 2012 on a silt loam soil at Freeman farm of Lincoln University. Soil samples were collected at four depths: 0-10, 10-20, 20-40 and 40-60 cm and they were oven dried at 105°C for 72 h for the calculation of air filled porosity (AFP), total pore space (TPS) and other soil physical properties. Pore space indices were computed using diffusivity models based on AFP and TPS. Soil samples were later saturated then brought into a pressure plate for measurements of moisture content (theta) at five different water potentials (Psi). Soil air samples for the measurements of greenhouse gases emissions were collected using static and vented chambers of 30 cm height and 20 cm diameter. The concentrations of CO2, CH4 and N2O in soil air samples were determined using a Gas Chromatograph GC-14. Results showed that pore space indices significantly correlated with greenhouse gases fluxes (p<0.05) with correlation coefficient (r) ranged from 0.27 to 0.53. More correlations were found in 2012 than 2011. Similarly, significant correlations were found between greenhouse gases and theta at Psi=0 and Psi=-0.05. Moisture content (theta) held at Psi=0 positively correlated with CO2 (r=0.49), N2O (r=0.64) and negatively correlated with CH4 (r=-0.43) at p<0.05. Soil pore space indices and soil water (content and potential) seem to control greenhouse gases emissions in this soil. Inclusion of these controlling factors in models will certainly improve our understanding of the dynamics of greenhouse gases fluxes from soil.
  • Authors:
    • Thomas,B. W.
    • Sharifi,M.
    • Whalen,J. K.
    • Chantigny,M. H.
  • Source: Soil Science Society of America Journal
  • Volume: 79
  • Issue: 5
  • Year: 2015
  • Summary: Manuring soil alters mineralizable N pools and organic matter fractions, but the magnitude is manure-type and soil-texture specific, complicating prediction of N mineralization. Our objective was to determine the responses of residual soil mineralizable N parameters to manure-type and evaluate their relationships to initial organic C and N fractions, C/N ratios, and mineral N concentrations in sandy loam and silty clay soils after three annual spring applications of manure. Manure types were liquid swine manure (LSM), liquid dairy cattle manure (LCM), or solid poultry manure (SPM), all applied at 90 kg available N ha-1 yr-1. Mineral fertilizer (NPK) and a zero-N control (CTL) were also included. Composite soil samples collected (0-to 20-cm depth) before manure application were aerobically incubated at 25°C for 48 wk. Both soils mineralized N linearly over 48 wk (r2 = 0.96-0.99) and the silty clay soil did not converge to nonlinear, first-order kinetics. Pool I (N mineralized in first 2 wk) was the only mineralizable N pool affected by manure-type, which was depleted by SPM in the sandy loam and increased by LCM in the silty clay. Salt extractable organic N was significantly correlated to Pool I in both soil textures. Only Pool I was significantly correlated with N mineralized over 48 wk in the sandy loam and silty clay soils (r = 0.92 and 0.64, respectively). Overall, readily mineralizable N (Pool I) was the most sensitive and robust indicator of mineralizable N after three annual manure applications to agricultural soils from a humid temperate region. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA. All Rights reserved.
  • Authors:
    • Bailey,Rebecca R.
    • Butts,Thomas R.
    • Lauer,Joseph G.
    • Laboski,Carrie A. M.
    • Kucharik,Christopher J.
    • Davis,Vince M.
  • Source: Weed Science
  • Volume: 63
  • Issue: 4
  • Year: 2015
  • Summary: Nitrous oxide (N2O) is a potent greenhouse gas with implication for climate change. Agriculture accounts for 10% of all greenhouse gas emissions in the United States, but 75% of the country's N2O emissions. In the absence of PRE herbicides, weeds compete with soybean for available soil moisture and inorganic N, and may reduce N2O emissions relative to a weed-free environment. However, after weeds are killed with a POST herbicide, the dead weed residues may stimulate N2O emissions by increasing soil moisture and supplying carbon and nitrogen to microbial denitrifiers. Wider soybean rows often have more weed biomass, and as a result, row width may further impact how weeds influence N2O emissions. To determine this relationship, field studies were conducted in 2013 and 2014 in Arlington, WI. A two-by-two factorial treatment structure of weed management (PRE + POST vs. POST-only) and row width (38 or 76 cm) was arranged in a randomized complete block design with four replications. N2O fluxes were measured from static gas sampling chambers at least weekly starting 2 wk after planting until mid-September, and were compared for the periods before and after weed termination using a repeated measures analysis. N2O fluxes were not influenced by the weed by width interaction or width before termination, after termination, or for the full duration of the study at P <= 0.05. Interestingly, we observed that POST-only treatments had lower fluxes on the sampling day immediately prior to POST application (P = 0.0002), but this was the only incidence where weed influenced N2O fluxes, and overall, average fluxes from PRE + POST and POST-only treatments were not different for any period of the study. Soybean yield was not influenced by width (P = 0.6018) or weed by width (P = 0.5825), but yield was 650 kg ha(-1) higher in the PRE + POST than POST-only treatments (P = 0.0007). These results indicate that herbicide management strategy does not influence N2O emissions from soybean, and the use of a PRE herbicide prevents soybean yield loss. Nomenclature: Soybean; Glycine max (L.) Merr.