• Authors:
    • Verhoeven, E.
    • Six, J.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 191
  • Year: 2014
  • Summary: Biochar amendment to soil has been proposed as a mechanism to mitigate climate change through an array of mechanisms; one being the mitigation of soil nitrous oxide (N 2O) emissions. Yet the extent and mechanisms through which this may be achieved in temperate agroecosystems is uncertain. We used a pine chip biochar produced at a moderate temperature (550°C, PC biochar) and a walnut shell biochar produced at a higher temperature (900°C, WS biochar). Biochar was applied at 10 Mg ha -1 to a working commercial wine grape system in North-Central California. The effects of biochar were assessed over two years at two distinct functional locations: the berm and row, which differed in N application and irrigation. N 2O emissions and ancillary soil properties (NH 4+, NO 3, water filled pore space (WFPS), and pH) were closely monitored following management and precipitation events. Soil bulk density, cover crop yield and soil C and N were measured annually to address longer term changes in cropping system and soil properties. In the PC biochar treatment, annual cumulative N 2O emissions were significantly higher than the control treatment each year ( p<0.05); 4.141.14 kg N 2O-N ha -1 yr -1 versus 2.000.66 kg N 2O-N ha -1 yr -1 in year one, and 4.240.74 kg N 2O-N ha -1 yr -1 versus 1.600.28 kg N 2O-N ha -1 yr -1 in year two. Emissions of N 2O in the WS biochar treatment were also higher than the control each year, but differences were not significant. The effect of biochar on N 2O emissions was more pronounced in the row location where annual emissions were significantly higher than the control in one and both years for the WS and PC biochars, respectively ( p<0.05). In the PC biochar treatment, we observed increased N 2O emissions at both functional locations, however increases were more pronounced in the row location where they were in part attributable to increased cover crop N inputs. Differences between treatments in NH 4+, NO 3- and WFPS were mostly not significant. The WS biochar significantly raised soil pH relative to the control ( p<0.05), however in the berm location only, and increased soil pH in this treatment did not correspond to changes in N 2O emissions. Since neither biochar amendment reduced N 2O emissions, our results demonstrate the need to evaluate N 2O emissions at a cropping system scale (e.g. encompassing changes in N inputs and cycling) and in systems where nitrification processes may dominate emissions.
  • Authors:
    • Escobar,N.
    • Ribal,F. J.
    • Clemente,G.
    • Sanjuan,N.
  • Source: Proceedings of the 9th International Conference on Life Cycle Assessment in the Agri-Food Sector
  • Year: 2014
  • Summary: Imported biodiesel has accounted for a large share of the total amount consumed in Spain, the main supplier of which was Argentina at least until anti-dumping duties on biodiesel imports from this origin were approved by the European Commission in November 2013. A consequential LCA is carried out in the present study to compare this pathway, which was the prevailing one until almost 2014, with the alternative of using domestic biodiesel from Used Cooking Oil (UCO). System expansion is performed in order to take the indirect functions of both systems into account, functions arising from interactions between co-products (protein meals) in the animal feed market. The marginal suppliers of these co-products in the international market are identified and emissions from direct and indirect Land Use Change (LUC) are calculated. When they are not considered, imported soybean biodiesel leads to lower GHG emissions, due to the carbon uptake by biomass. However, when global LUC is taken into account, UCO biodiesel generates a much lower impact, because it causes a contraction in the area diverted to biofuel feedstock production in other parts of the world. The results underline the importance of considering emissions from LUC when comparing biodiesel alternatives and, thus, interactions in the global market must be addressed.
  • 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:
    • Parikh, S. J.
    • Six, J.
    • Mukome, F. N. D.
  • Source: Geoderma
  • Volume: 200-201
  • Year: 2013
  • Summary: Land application of biochar, as a strategy to enhance soil fertility and reduce greenhouse gas (GHG) emissions is receiving widespread interest. Short-term soil incubations (29 days) were used to investigate the effects of agriculturally relevant biochar applications from two contrasting feedstocks and temperatures on CO2 and N2O emissions from a fertile agricultural soil amended with different types of fertilizer (organic and synthetic). In addition, the effects of biochar on the denitrification process were examined using an acetylene based method to ascertain N2O and N-2 emissions during denitrification. Complementary incubation experiments without soil (biochar and biochar with compost) examined the impact on natural or amended organic matter (compost) and biochar stability and surface chemistry were also investigated. Batch incubations (25 degrees C) of biochar (softwood pyrolyzed at 410 degrees C [WF410] and 510 degrees C [WF510] and walnut shell pyrolyzed at 900 degrees C [WA(900)]) amended soils were performed to determine emissions of CO2 and N2O due to complete (absence of acetylene [C2H2]) and incomplete denitrification (presence of C2H2). Similarly, GHG emissions from the complementary incubations were also measured. Concurrent biochar surface compositional changes were investigated with attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopy. Biochar effects on CO2 emissions were not significantly different from controls. WA900 biochar (high pH) affects N cycling resulting in significantly higher emissions of N2O under conditions of complete denitrification and of N-2 under conditions examining incomplete denitrification. WF410 (highest H/C ratio and lowest surface area) treatments with compost resulted in higher GHGs emissions which is attributed to a priming effect of the compost organic matter (COM). In addition, WF410 was most susceptible to degradation, evident from infrared spectroscopic analysis of the biochars. Although these results suggest that not all biochars provide substantial benefits as a soil amendment the data do demonstrate potential for development of biochars with beneficial impacts on GHG emission mitigation and enhancement of soil C stocks.
  • Authors:
    • Paustian, K.
    • Ngugi, M. K.
    • Suddick, E. C.
    • Six, J.
  • Source: California Agriculture
  • Volume: 67
  • Issue: 3
  • Year: 2013
  • Summary: California growers could reap financial benefits from the low-carbon economy and cap-and-trade system envisioned by the state's AB 32 law, which seeks to lower greenhouse gas emissions statewide. Growers could gain carbon credits by reducing greenhouse gas emissions and sequestering carbon through reduced tillage and increased biomass residue incorporation. First, however, baseline stocks of soil carbon need to be assessed for various cropping systems and management practices. We designed and set up a pilot soil carbon and land-use monitoring network at several perennial cropping systems in Northern California. We compared soil carbon content in two vineyards and two orchards (walnut and almond), looking at conventional and conservation management practices, as well as in native grassland and oak woodland. We then calculated baseline estimates of the total carbon in almond, wine grape and walnut acreages statewide. The organic walnut orchard had the highest total soil carbon, and no-till vineyards had 27% more carbon in the surface soil than tilled vineyards. We estimated wine grape vineyards are storing significantly more soil carbon per acre than almond and walnut orchards. The data can be used to provide accurate information about soil carbon stocks in perennial cropping systems for a future carbon trading system.
  • Authors:
    • Blanco-Lopez, M. A.
    • Perez-Rodriguez, M.
    • Garcia-Cabello, S.
    • Lopez-Escudero, F. J.
  • Source: European Journal of Plant Pathology
  • Volume: 133
  • Issue: 4
  • Year: 2012
  • Summary: Verticillium dahliae Kleb. causes Verticillium wilts in many herbaceous and woody species. Many hosts of the pathogen are commonly cultivated in Andalucia (southern Spain), particularly major crops such as cotton, vegetables, almond, peach and, particularly, olive, in which the fungus causes Verticillium wilt of olive. Infective structures of the pathogen (microsclerotia), produced in the late phases of the infection cycle in senescent tissues of the infected plants, can be spread over short or long distances by a number of dispersal methods. Irrigation water is one of the factors implicated in this spread of V. dahliae. Indeed, increasing irrigation dosages in crops or an inadequate irrigation schedule have been identified as cultural practices favouring Verticillium wilt onset and severity in olive and other hosts. Most of the cultivated areas in the Guadalquivir Valley of Andalucia are irrigated by pumping stations using modern infrastructures that supply water to thousands of hectares of farm land, which are usually associated with irrigation communities. This study demonstrates that the pathogen survives in the sediment and particles suspended in water used for irrigation in different facilities of an irrigation community, that were involved in distributing water (main canal and reception tank of a investigated pumping station, irrigation pools and sand from filters). Thus microsclerotia moves from the pumping station to individual plots (olive and cotton cultivated farm) as viable microsclerotia, free or embedded in soil particles and plant debris, suspended in the irrigation water, or deposited in the sludge in piping systems or water storage ponds. We have detected amounts of inoculum in the solid pellet samples in these facilities that ranged from 2.7 to 6.7 microsclerotia per gram. Besides this, water from drippers in cultivated plots released into the soil a variable amount of infective propagules of the pathogen over time that accounted for 3.75 microsclerotia/m 3 in some of the recording times. Therefore, irrigation water becomes an important source of inoculum that is very effectively involved in medium and long-distance spread of the pathogen.
  • Authors:
    • Sanderlin, R. S.
    • Melanson, R. A.
    • McTaggart, A. R.
    • Ham, J. H.
  • Source: Plant Disease
  • Volume: 96
  • Issue: 8
  • Year: 2012
  • Summary: Xylella fastidiosa causes disease in a number of economically important crops, ornamental plants, and shade trees, including grapevine, citrus, oleander, and sycamore. In pecan, X. fastidiosa causes pecan bacterial leaf scorch (PBLS), which leads to defoliation and reduces nut yield. No economically effective treatments are available for PBLS. In order to improve PBLS management practices, it is necessary to determine the subspecies of X. fastidiosa strains that infect pecan so that potential sources of inoculum may be identified. Multiprimer polymerase chain reaction (PCR) and phylogenetic analyses using nucleotide sequence data from the 16S-23S rRNA intergenic transcribed spacer (ITS) region and pglA consistently identified strains of X. fastidiosa isolated from pecan as X. fastidiosa subsp. multiplex. Enterobacterial repetitive intergenic consensus PCR and repetitive extragenic palindromic (REP)-PCR analyses were congruent with phylogenetic analyses. REP-PCR analyses indicated genetic variation within strains of X. fastidiosa from pecan. From these same analyses, X. fastidiosa strains from sycamore, grapevine, and oleander from Louisiana were identified as subsp. multiplex, subsp. fastidiosa, and subsp. sandyi, respectively. This study provides additional information about the host ranges of X. fastidiosa subspecies.
  • Authors:
    • Stockert, C. M.
    • Muhammad, S.
    • Alsina, M. M.
    • Schellenberg, D. L.
    • Wolff, M. W.
    • Sanden, B. L.
    • Brown, P. H.
    • Smart, D. R.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 155
  • Year: 2012
  • Summary: The optimum yield-scaled global warming potential (GWP) of perennial crops on arid land requires effective strategies for irrigation and fertilization. In 2009-2010, N 2O emissions and CH 4 oxidation were measured from an almond [ Prunus dulcis (Mill.) D.A. Webb] production system irrigated with nitrogen (N) fertilizers. Individual plots were selected within a randomized complete block design with fertilizer treatments of urea ammonium nitrate (UAN) and calcium ammonium nitrate (CAN). Event-related N 2O emissions from irrigation and fertilization were determined for seasonal periods of post-harvest, winter, spring and summer. Peak N 2O emissions in summer occurred within 24 h after fertilization, and were significantly greater from UAN compared to CAN ( p<0.001). Cumulative N 2O emissions from UAN were on average higher than CAN though not significantly different. Air temperature, water-filled pore space (WFPS), soil ammonium (NH 4+) and soil nitrate (NO 3-) showed significant positive correlation with N 2O emissions and significant negative correlation was found for the number of days after fertilization (DAF). The percentage of N 2O loss from N fertilizer inputs was 0.23% for CAN and 0.35% for UAN while CH 4 oxidation offset 6.0-9.3% of N 2O emissions. Total kernel yield was not significantly different between fertilizer treatments. Yield-scaled GWP for almond from CAN (60.9 kg CO 2eq Mg -1) and UAN (91.9 kg CO 2eq Mg -1) represent the first report of this metric for a perennial crop. These results outline effective irrigation and fertilization strategies to optimize yield-scaled GWP for almond on arid land.
  • Authors:
    • Kussman, R. D.
    • Kremer, R. J.
  • Source: Agroforestry Systems
  • Volume: 83
  • Issue: 2
  • Year: 2011
  • Summary: Intercropping alleys in agroforestry provides an income source until the tree crop produces harvestable yields. However, cultivation of annual crops decreases soil organic matter and increases soil erosion potential, especially on sloping landscapes. Perennial crops maintain a continuous soil cover, increase water infiltration, reduce soil erosion, and improve overall soil quality. The objective of this on-farm study was to assess the effects of a perennial legume, kura clover ( Trifolium ambiguum M. Bieb.), on soil quality in a recently established pecan ( Carya illinoinensis Wangenh. C. Koch) orchard. The pecan-kura clover agroforestry practice was established on deep loess soils of the Missouri River hills landscape. These silt loams are on 2-20% slopes and can be highly erosive. Kura clover, introduced as the alley crop 5 years after pecan planting, was selected based on its perennial growth habit, nitrogen-fixing ability, winter hardiness, high forage quality, and soil conservation properties. Kura clover was seeded in 2001 and harvested for hay annually beginning 2003. Soil quality indicators of total organic C, total N, water-stable aggregates, and selected soil enzymes were determined on surface soil samples collected annually after kura clover establishment. Soil organic C and activities of soil enzymes increased compared with cultivated and grass pasture control soils by the eighth year of establishment. Water-stable aggregation improved by 50% and surface soil shear strength improved significantly ( P<0.05) in alleys compared with control sites. Results illustrate that kura clover as the alley-cropped component improved soil fertility and biological activity through increased organic matter and improved soil structure, and yielded high quality forage valuable for the cattle-feeding operation. Kura clover maintained or improved soil quality, reduced soil erosion potential, and benefited pecan growth by providing a source of soil nitrogen and improving soil structure for adequate water infiltration and aeration.
  • Authors:
    • Miyamoto, S.
    • Nesbitt, M.
  • Source: HortTechnology
  • Volume: 21
  • Issue: 5
  • Year: 2011
  • Summary: Soil salinity management is a factor for successful production of pecan ( Carya illinoinensis) in arid southwestern United States. An exploratory study was performed to evaluate the effect of various soil management practices on salt leaching in basin-irrigated orchards developed on alluvial soils (Torrifluvents, Entisols) of the middle Rio Grande Basin. The practices evaluated were ripping, minimum-till chiseling, and soil profile modification. For ripping, parabolic shanks were passed through the center section (4 to 8 ft wide) between each tree row to a depth ranging from 18 to 36 inches. Minimum-till chisels included 7- and 30-inch shanks, equipped with coulters to reduce break up of the ground surface. Soil profile modification consisted of trenching with a backhoe and profile mixing with a large excavator. The effectiveness of these methods was evaluated by measuring soil salinity and moisture in treated and untreated zones at 17 test sites. Both ripping and minimum-till deep chiseling helped improve salt leaching, and the effectiveness of salt leaching increased as working depths approach the thickness of the clayey layer. However, annual ripping of the center section of each tree row space may not provide wide enough zones to alleviate salt stress to the trees. Straight shanks prune but do not lift tree roots, thus appearing to be better suited for chiseling closer to tree rows. Soil profile modification was highly effective in leaching salts. From the view of minimizing soil aggregate destruction and of maintaining a leveled floor, minimum-till deep chiseling, followed by the use of sand-topdressing and minimum-till shallow chisels for maintenance may prove to be more desirable than conventional ripping, especially in soil types consisting of silty clay loam.