• Authors:
    • Belina, K. M.
    • Steenwerth, K.
  • Source: Applied Soil Ecology
  • Volume: 40
  • Issue: 2
  • Year: 2008
  • Summary: Impacts of soil tillage and cover crops on soil carbon (C) dynamics and microbiological function were investigated in a vineyard grown in California's mediterranean climate. We (1) compared soil organic matter (SOM), C dynamics and microbiological activity of two cover crops [Trios 102 (Triticale x Triosecale) ('Trios'), Merced Rye (Secale cereale) ('Rye')] with cultivation ('Cultivation') and (2) evaluated seasonal effects of soil temperature, water content, and precipitation on soil C dynamics (0-15 cm depth). From treatments established in November 2001, soils were sampled every 2-3 weeks from November 2005 to November 2006. Gravimetric water content (GWC) reflected winter and spring rainfall. Soil temperature did not differ among treatments, reflecting typical seasonal patterns. Few differences in C dynamics between cover crops existed, but microbial biomass C (MBC), dissolved organic C (DOC), and carbon dioxide (CO2) efflux in 'Trios' and 'Rye' were consistently 1.5-4-fold greater than 'Cultivation'. Cover crops were more effective at adding soil C than 'Cultivation'. Seasonal patterns in DOC, and CO2 efflux reflected changes in soil water content, but MBC displayed no temporal response. Decreases in DOC and potential microbial respiration (RESPmic) (i.e., microbially available C) also corresponded to or were preceded by increases in CO2 efflux, suggesting that DOC provided C for microbial respiration. Despite similar MBC, DOC, RESPmic, annual CO2 efflux and aboveground C content between the two cover crops, greater aboveground net primary productivity and SOM in 'Trios' indicated that 'Trios' provided more soil C than 'Rye'.
  • Authors:
    • Laird, D. A.
  • Source: Agronomy Journal
  • Volume: 100
  • Issue: 1
  • Year: 2008
  • Summary: Processing biomass through a distributed network of fast pyrolyzers may be a sustainable platform for producing energy from biomass. Fast pyrolyzers thermally transform biomass into bio-oil, syngas, and charcoal. The syngas could provide the energy needs of the pyrolyzer. Bio-oil is an energy raw material ([~]17 MJ kg-1) that can be burned to generate heat or shipped to a refinery for processing into transportation fuels. Charcoal could also be used to generate energy; however, application of the charcoal co-product to soils may be key to sustainability. Application of charcoal to soils is hypothesized to increase bioavailable water, build soil organic matter, enhance nutrient cycling, lower bulk density, act as a liming agent, and reduce leaching of pesticides and nutrients to surface and ground water. The half-life of C in soil charcoal is in excess of 1000 yr. Hence, soil-applied charcoal will make both a lasting contribution to soil quality and C in the charcoal will be removed from the atmosphere and sequestered for millennia. Assuming the United States can annually produce 1.1 x 109 Mg of biomass from harvestable forest and crop lands, national implementation of The Charcoal Vision would generate enough bio-oil to displace 1.91 billion barrels of fossil fuel oil per year or about 25% of the current U.S. annual oil consumption. The combined C credit for fossil fuel displacement and permanent sequestration, 363 Tg per year, is 10% of the average annual U.S. emissions of CO2-C.
  • Authors:
    • Hepperly, P.
    • LaSalle, T. J.
  • Year: 2008
  • Authors:
    • Diamant, A.
    • Knipping, E.
  • Source: Handout for US EPA Integrated Nitrogen Committee
  • Year: 2008
  • Authors:
    • De Moura, R. L.
    • Klonsky, K. M.
    • Marsh, B. H.
    • Frate, C. A.
  • Source: University of California Cooperative Extension Publication
  • Year: 2008
  • Summary: Sample costs to produce grain corn (field corn for grain) in the southern San Joaquin Valley, California, USA, are shown in this study.
  • Authors:
    • Livingston, P.
    • Klonsky, K. M.
    • Munier, D. J.
    • Schmierer, J. L.
    • Brittan, K. L.
  • Source: University of California Cooperative Extension Publication
  • Year: 2008
  • Summary: Sample costs to produce field corn in the Sacramento Valley of California, USA, are presented in this study.
  • Authors:
    • Eriksen-Hamel, N. S.
    • Angers, D. A.
  • Source: Soil Science Society of America Journal
  • Volume: 72
  • Issue: 5
  • Year: 2008
  • Summary: While the adoption of no-till (NT) usually leads to the accumulation of soil organic C (SOC) in the surface soil layers, a number of studies have shown that this effect is sometimes partly or completely offset by greater SOC content near the bottom of the plow layer under full-inversion tillage (FIT). Our purpose was to review the literature in which SOC profiles have been measured under paired NT and FIT situations. Only replicated and randomized studies directly comparing NT and FIT for >5 yr were considered. Profiles of SOC had to be measured to at least 30 cm. As expected, in most studies SOC content was significantly greater (P < 0.05) under NT than FIT in the surface soil layers. At the 21- to 25-cm soil depth, however, which corresponds to the mean plowing depth for the data set (23 cm), the average SOC content was significantly greater under FIT than NT. Moreover, under FIT, greater SOC content was observed just below the average depth of plowing (26-35 cm). On average, there was 4.9 Mg ha(-1) more SOC under NT than FIT (P = 0.03). Overall, this difference in favor of NT increased significantly but weakly with the duration of the experiment (R-2 = 0.15, P = 0.05). The relative accumulation of SOC at depth under FIT could not be related to soil or climatic variables. Furthermore, the organic matter accumulating at depth under FIT appeared to be present in relatively stable form, but this hypothesis and the mechanisms involved require further investigation.
  • Authors:
    • Ceccarelli, S.
    • Baum, M.
    • This, D.
    • Greco, A.
    • Grando, S.
    • Korff, M.
  • Source: Theoretical and Applied Genetics
  • Volume: 117
  • Issue: 5
  • Year: 2008
  • Summary: The objective of the present study was to identify quantitative trait loci (QTL) influencing agronomic performance across rain fed Mediterranean environments in a recombinant inbred line (RIL) population derived from the barley cultivars ER/Apm and Tadmor. The population was tested in four locations (two in Syria and two in Lebanon) during four consecutive years. This allowed the analysis of marker main effects as well as of marker by location and marker by year within location interactions. The analysis demonstrated the significance of crossover interactions in environments with large differences between locations and between years within locations. Alleles from the parent with the higher yield potential, ER/Apm, were associated with improved performance at all markers exhibiting main effects for grain yield. The coincidence of main effect QTL for plant height and yield indicated that average yield was mainly determined by plant height, where Tadmor's taller plants, being susceptible to lodging, yielded less. However, a number of crossover interactions were detected, in particular for yield, where the Tadmor allele improved yield in the locations with more severe drought stress. The marker with the highest number of cross-over interactions for yield and yield component traits mapped close to the flowering gene Ppd-H2 and a candidate gene for drought tolerance HVA1 on chromosome 1H. Effects of these candidate genes and QTL may be involved in adaptation to severe drought as frequently occurring in the driest regions in the Mediterranean countries. Identification of QTL and genes affecting field performance of barley under drought stress is a first step towards the understanding of the genetics behind drought tolerance.
  • Authors:
    • Diekmann, J.
    • Ryan, J.
    • Pala, M.
    • Singh, M.
  • Source: Experimental Agriculture
  • Volume: 44
  • Issue: 4
  • Year: 2008
  • Summary: With increasing land-use pressure in semi-arid, dryland Middle Eastern agriculture, fallow-based cereal production has given way to cropping intensification, including legume-based rotations along with conservation tillage and on-farm straw disposal. Such agronomic developments can only be biologically and economically assessed in multi-year trials. Thus, this 10-year study examined the influence of tillage systems (conventional and shallow or conservation) and variable stubble management, including compost application, on yields of barley and vetch grown in rotation. Barley yielded higher with compost applied every two or four years than with burning or soil-incorporating the straw and stubble. Barley straw and grain yields were generally higher with the mouldboard plough. Similarly with vetch, treatments involving compost application yielded significantly higher than burning or incorporating the straw and stubble. Despite yearly differences between crop yields, the pattern of treatment differences was consistent. Thus, the cereal-vetch rotation system is sustainable, while excess straw could be used as compost with benefit to the crop. Though there was no clear advantage of the shallow conservation-type tillage, the energy costs are less, thus indicating its possible advantage over conventional deep tillage in such rotational cropping systems.
  • Authors:
    • Pala, M.
    • Rashid, A.
    • Masri, S.
    • Matar, A.
    • Singh, M.
    • Ibrikci, H.
    • Ryan, J.
  • Source: European Journal of Agronomy
  • Volume: 28
  • Issue: 2
  • Year: 2008
  • Summary: Given the complex nature of rainfed cropping systems in Mediterranean agriculture and the dynamic nature of phosphorus (P) in soils, agronomic assessment of P fertilization must be long term in order to consider residual effects. Thus, a 9-year study involved initial relatively large applications of P (0, 50, 100, 150, 200 kg P 2O 5 ha -1) and yearly smaller dressings (0, 15, 30, 45, 60 kg P 2O 5 ha -1) in a trial involving dryland cereals (wheat/barley) in rotation with legumes (chickpea, lentil, or vetch) at three locations with varying mean annual rainfall in northern Syria; Breda (270 mm), Tel Hadya (342 mm) and Jindiress (470 mm). Assessment was made of grain, straw and total biomass yield and crop P uptake and available P (Olsen). While crop responses varied due to seasonal rainfall fluctuations, they tended to decrease with increasing initial available soil P levels (2.7, 6.2, and 4.4 mg kg -1 for Breda, Tel Hadya and Jindiress, respectively). Residual P was not significant for cereals or legumes at any site, but direct P was significant for both crops at Breda and Jindiress, as well as for legumes at Tel Hadya. In contrast, residual and direct P significantly influenced Olsen-P and seasonal and total P uptake. With no P fertilizer, or where minimal amounts (15 kg P 2O 5 ha -1) were applied annually, the balance between applied P and crop P offtake became increasingly negative; after 8 years without applied P, the P balance was -54, -38, -27, -17, and +7 kg ha -1 for the initial (residual) P application of 0, 50, 100, 150, and 200 kg P 20 5, respectively. This was counterbalanced by the higher annual application rates and to a lesser extent the amounts of P applied initially. The study demonstrated the highly variable nature of crop responses to fertilizer P under semi-arid field conditions over several years, with soil moisture from seasonal rainfall being the dominant influence on overall yields. While crop responses may not occur in any given year, especially if available P is near or above critical threshold levels, dryland cropping without P fertilizer is unsustainable in the long run.