• Authors:
    • Kennedy, A. C.
    • Bary, A. I.
    • Cogger, C. G.
    • Fortuna, A. M.
  • Source: Journal of Environmental Quality
  • Volume: 42
  • Issue: 6
  • Year: 2013
  • Summary: Biosolids have the potential to improve degraded soils in grain-fallow rotations. Our objectives were to determine if repeated biosolids applications in wheat ( Triticum aestivum L.) - fallow could supply adequate but not excessive N for grain production and increase soil C without creating a high risk of P loss. A replicated on-farm experiment was established in 1994 in central Washington, comparing anaerobically digested biosolids with anhydrous NH 3 and a zero-N control. Biosolids were applied at 5, 7, and 9 Mg ha -1 every fourth year through 2010 and incorporated 10 cm deep, while anhydrous NH 3 plots received 56 kg ha -1 N every second year. Grain yield and protein were determined. Soil chemical, biological, and bulk density analyses were made in 2012. Medium and high biosolids rates significantly increased grain yield (3.63 vs. 3.13 Mg ha -1) and protein (103 vs. 85 g kg -1) compared with anhydrous NH 3 averaged across all crops. The medium biosolids rate had significantly lower bulk density (1.05 vs. 1.22 g kg -1) and greater total C (0-10-cm depth) (16.9 vs. 9.4 g kg -1), mineralizable N (156 vs. 52 mg kg -1), and extractable P (114 vs. 16 mg kg -1) than anhydrous NH 3. The P index site vulnerability increased from low for anhydrous NH 3 to medium for the biosolids treatments. Soil NO 3-N was nearly always <10 mg N kg -1 soil (0-30-cm depth). Medium and high biosolids rates significantly increased bacteria/fungi ratios, Gram-negative bacteria, and anaerobic bacteria markers compared with anhydrous NH 3. Biosolids can be an agronomically and environmentally sound management practice in wheat-fallow systems.
  • Authors:
    • Green, J. M.
    • Snapp, S. S.
    • Culman, S. W.
    • Gentry, L. E.
  • Source: Agronomy Journal
  • Volume: 105
  • Issue: 2
  • Year: 2013
  • Summary: Labile soil organic matter plays an extremely important role in crop nutrient acquisition, but quantifying this pool can be prohibitively expensive to farmers. A better understanding of rapid and inexpensive measures of labile organic matter could lead to new tools for predicting soil N supply and crop performance. Toward this end, we quantified several simple measures of labile C and N over the course of the corn ( Zea mays L.) growing season in a long-term systems trial to determine:(i) the temporal dynamics of these measures, (ii) the long-term response of these measures to management, and (iii) the capacity of these measures to predict corn agronomic performance. We found that all labile soil measures (permanganate oxidizable carbon [POXC], C mineralization, N mineralization, and soil inorganic N) varied temporally and responded to long-term differences in management. Corn grain and vegetative biomass also responded to long-term treatment differences and these differences were strongly related to the measured labile soil C and N fractions. The history of crop rotation had a greater influence than management regime on all soil measures, with the exception of POXC. Of all the measures, C mineralization was the best predictor of agronomic performance both individually ( r=0.61-0.78, depending on corn stage), and when modeled with multiple indicators (six out of nine models). The results presented here demonstrate the strong relationship between crop growth and labile organic matter dynamics, and provide further evidence that C mineralization is an inexpensive, but sensitive predictor of corn agronomic performance.
  • Authors:
    • Mynsberge, A. R.
    • Greenberg, J. A.
    • Swanson, A. K.
    • Abatzoglou, J.
    • Dobrowski, S. Z.
    • Holden, Z. A.
    • Schwartz, M. K.
  • Source: Global Change Biology
  • Volume: 19
  • Issue: 1
  • Year: 2013
  • Summary: Rapid climate change has the potential to affect economic, social, and biological systems. A concern for species conservation is whether or not the rate of on-going climate change will exceed the rate at which species can adapt or move to suitable environments. Here we assess the climate velocity (both climate displacement rate and direction) for minimum temperature, actual evapotranspiration, and climatic water deficit (deficit) over the contiguous US during the 20th century (1916-2005). Vectors for these variables demonstrate a complex mosaic of patterns that vary spatially and temporally and are dependent on the spatial resolution of input climate data. Velocities for variables that characterize the climatic water balance were similar in magnitude to that derived from temperature, but frequently differed in direction resulting in the divergence of climate vectors through time. Our results strain expectations of poleward and upslope migration over the past century due to warming. Instead, they suggest that a more full understanding of changes in multiple climatic factors, in addition to temperature, may help explain unexpected or conflicting observational evidence of climate-driven species range shifts during the 20th century.
  • Authors:
    • Soulis, J.
    • Eells, J. C.
  • Source: Journal of Soil and Water Conservation
  • Volume: 68
  • Issue: 5
  • Year: 2013
  • Authors:
    • Baker, J. M.
    • Schultz, N. M.
    • Fassbinder, J. J.
    • Griffis, T. J.
  • Source: Journal of Environmental Quality
  • Volume: 42
  • Issue: 2
  • Year: 2013
  • Summary: Continuous measurement of soil N 2O emissions is needed to constrain N 2O budget and emission factors. Here, we describe the performance of a low-power Teledyne N 2O analyzer and automated chamber system, powered by wind and solar, that can continuously measure soil N 2O emissions. Laboratory testing of the analyzer revealed significant temperature sensitivity, causing zero drift of -10.6 nmol mol -1°C -1. However, temperature-induced span drift was negligible, so the associated error in flux measurement for a typical chamber sampling period was on the order of 0.016 nmol m -2 s -2. The 1-Hz precision of the analyzer over a 10-min averaging interval, after wavelet decomposition, was 1.5 nmol mol -1, equal to that of a tunable diode laser N 2O analyzer. The solar/wind hybrid power system performed well during summer, but system failures increased in frequency in spring and fall, usually at night. Although increased battery storage capacity would decrease down time, supplemental power from additional sources may be needed to continuously run the system during spring and fall. The hourly flux data were numerically subsampled at weekly intervals to assess the accuracy of integrated estimates derived from manually sampling static chambers. Weekly sampling was simulated for each of the five weekdays and for various times during each day. For each weekday, the cumulative N emissions estimate using only morning measurements was similar (within 15%) to the estimate using only afternoon measurements. Often, weekly sampling partially or completely missed large episodic N 2O emissions that continuous automated chamber measurements captured, causing weekly measurements to underestimate cumulative N emissions for 9 of the 10 sampling scenarios.
  • Authors:
    • Smith, P.
    • Williams, M.
    • Forristal, D.
    • Lanigan, G.
    • Osborne, B.
    • Abdalla, M.
    • Jones, M. B.
  • Source: Soil Use and Management
  • Volume: 29
  • Issue: 2
  • Year: 2013
  • Summary: Conservation tillage (CT) is an umbrella term encompassing many types of tillage and residue management systems that aim to achieve sustainable and profitable agriculture. Through a global review of CT research, the objective of this paper was to investigate the impacts of CT on greenhouse gas (GHG) emissions. Based on the analysis presented, CT should be developed within the context of specific climates and soils. A number of potential disadvantages in adopting CT practices were identified, relating mainly to enhanced nitrous oxide emissions, together with a number of advantages that would justify its wider adoption. Almost all studies examined showed that the adoption of CT practices reduced carbon dioxide emissions, while also contributing to increases in soil organic carbon and improvements in soil structure.
  • Authors:
    • Gimeno, B. S.
    • Gattinger, A.
    • Lassaletta, L.
    • Aguilera, E.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 168
  • Year: 2013
  • Summary: Mediterranean croplands are seasonally dry agroecosystems with low soil organic carbon (SOC) content and high risk of land degradation and desertification. The increase in SOC is of special interest in these systems, as it can help to build resilience for climate change adaptation while contributing to mitigate global warming through the sequestration of atmospheric carbon (C). We compared SOC change and C sequestration under a number of recommended management practices (RMPs) with neighboring conventional plots under Mediterranean climate (174 data sets from 79 references). The highest response in C sequestration was achieved by those practices applying largest amounts of C inputs (land treatment and organic amendments). Conservation tillage practices (no-tillage and reduced tillage) induced lower effect sizes but significantly promoted C sequestration, whereas no effect and negative net sequestration rates were observed for slurry applications and unfertilized treatments, respectively. Practices combining external organic amendments with cover crops or conservation tillage (combined management practices and organic management) showed very good performance in C sequestration. We studied separately the changes in SOC under organic management, with 80 data sets from 30 references. The results also suggest that the degree of intensification in C input rate is the main driver behind the relative C accumulation in organic treatments. Thus, highest net C sequestration rates were observed in most eco-intensive groups, such as "irrigated", "horticulture" and controlled experiments ("plot scale"). (C) 2013 Elsevier B.V. All rights reserved.
  • Authors:
    • Smart, D. R.
    • Fanton-Borges, A. C.
    • Alsina, M. M.
  • Source: Ecosphere
  • Volume: 4
  • Issue: 1
  • Year: 2013
  • Summary: Nitrogen fertilizer applied to soil is the primary source of the greenhouse gas (GHG) nitrous oxide (N2O). The assessment of N2O emissions, or net fluxes of the GHG methane (CH4), are lacking for upland, arid agricultural ecosystems worldwide. In California, where rates of application for nitrogen (N) can exceed 300 kg per hectare for N-intensive fruit and nut crops (>2 million acres), liquid N fertilizers applied through microirrigation systems (fertigation) represent the predominant method of N fertilization. Little information is available for how these concentrated and spatially discrete N solution applications influence N2O emissions and net CH4 fluxes (the sum of methanogenic and methanotrophic activity). In this study we examined soil N2O-N emissions and net CH4 fluxes for drip and stationary microsprinklers, two of the most widely used fertigation emitters, in an almond orchard where 235.5 kg N/ha were applied during the season of measurement (2009-2010). We accomplished this by modeling the spatial patterns of N2O and CH4 at the scale of meters and centimeters using simple mathematical approaches. For two applications of 33.6 kg/ha and three applications of 56.1 kg/ha targeted to the phenologic stages with highest tree N demand, the spatial patterns of N2O fluxes were similar to the emitter water distribution pattern and independent of temperature and fertilizer N form applied. Net CH4 fluxes were extremely low and there was no discernible spatial pattern, but areas kept dry (driveways between tree rows) generally consumed CH4 while it was produced in the microirrigation wet-up area. The N2O-N emissions for fertigation events at the scale of days, and over a season, were significantly higher from the drip irrigated orchard (1.6 +/- 0.7 kg N2O-N ha(-1) yr(-1)) than a microsprinkler irrigated orchard (0.6 +/- 0.3 kg N2O-N ha(-1) yr(-1)). N2O emissions and net CH4 fluxes were only significantly correlated with soil water filled pore space and not with mineral-N. The correlation was much better for N2O emissions. Our results greatly improve our ability to scale N2O production to the orchard level, and provide growers with a tool for lowering almond orchard carbon and nitrogen footprints.
  • Authors:
    • Benbi, D. K.
  • Source: Journal of Crop Improvement OR Combating Climate Change: An Agricultural Perspective, Ch. 5 OR Greenhouse gas emissions from U.S. agriculture and forestry: A review of emission sources, controlling factors, and mitigation potential. Interim report to
  • Volume: 27
  • Issue: 6
  • Year: 2013
  • Summary: The anthropogenic emission of greenhouse gases (GHGs), that is, carbon dioxide (CO 2), methane (CH 4), and nitrous oxide (N 2O), is bringing about major changes to the global environment. Whereas most of the emissions come from combustion of fossil fuels and industrial processes, agriculture accounts for 10%-12% of the total anthropogenic emission of GHGs. Emissions from agriculture amount to 5.1-6.1 Gt CO 2-eq/year, including 3.3 Gt CO 2-eq/year as CH 4 and 2.8 Gt CO 2-eq as N 2O. Of the total non-CO 2 emissions from agriculture, N 2O emissions from soils and CH 4 emissions from enteric fermentation comprise 38% and 32%, respectively. Biomass burning, rice agriculture, and manure management account for 12%, 11%, and 7% of the emissions, respectively. Compared with 1990, agricultural emissions of CH 4 and N 2O have increased by nearly 17%, representing a mean emissions increase of about 60 Mt CO 2-eq/year. The adoption of improved management practices and mitigation technologies could help in reducing emissions. The strategies for lowering CO 2 emissions include reducing the global energy use, developing low- or no-carbon fuel, and sequestering CO 2 through natural and engineering techniques. Because engineering techniques are still in developmental stages, C sequestration in soil and vegetation is considered a viable option. Management practices that increase carbon input to the soil or reduce C loss, or both, lead to net carbon sequestration in soils. Appropriate water and nutrient management, cultural practices, and choice of crop cultivars can help reduce CH 4 emissions from rice fields. Practices that improve N-use efficiency can reduce N 2O emissions and indirectly reduce GHG emissions from N fertilizer manufacture. The global technical GHG mitigation potential from agriculture by 2030 is estimated to be 5.5-6.0 Gt CO 2-eq/year. Realizing this potential will require the adoption of best available management practices with reference to soil type and LU system.
  • Authors:
    • Blanco-Canqui, H.
  • Source: BioEnergy Research
  • Volume: 6
  • Issue: 1
  • Year: 2013
  • Summary: Crop residue removal for bioenergy can deplete soil organic carbon (SOC) pools. Management strategies to counteract the adverse effects of residue removal on SOC pools have not been, however, widely discussed. This paper reviews potential practices that can be used to offset the SOC lost with residue removal. Literature indicates that practices including no-till cover crops, manure and compost application, and return of biofuel co-products increase SOC pools and may thus be used to offset some SOC loss. No-till rotations that include semi-perennial grasses or legumes also offer a promise to promote soil-profile C sequestration and improve soil resilience after residue removal. No-till cover crops can sequester between 0.10 and 1 Mg ha(-1) per year of SOC relative to no-till without cover crops, depending on cover crop species, soil type, and precipitation input. Animal manure and compost contain about 15 % of C and thus their addition to soil can enhance SOC pools and boost soil biological activity. Similarly, application of biofuel co-products such as biochar, which contain between 45 % and 85 % of C depending on the feedstock source and processing method, can enhance long-term C sequestration. These mitigation strategies may maintain SOC pools under partial residue removal in no-till soils but are unlikely to replace all the SOC lost if residue is removed at excessive rates. More field research and modeling efforts are needed to assess the magnitude at which the different mitigation strategies can overcome SOC loss with crop residue removal.