• Authors:
    • Wang, J.
    • Mei, X.
    • Zhang, Y.
    • Yan, C.
    • Chen, B.
    • Liu, E.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 79
  • Issue: 2
  • Year: 2015
  • Summary: Tillage practices affect soil organic carbon (SOC) pools, which in turn influence soil ecosystem processes. In this study we measured the effects of long-term conventional tillage (CT) and no-till (NT) practices on SOC and its fraction over the winter wheat growing season in surface and subsurface soils. Soil samples were taken during five physiological stages of winter wheat growth to a depth of 60 cm from the long-term (19 yr) experimental station on Loess Plateau in China. While the SOC content increased slowly in the surface soils during winter wheat growth with the NT treatment, it showed less fluctuation with the CT treatment. On average, NT treatment resulted in 82 and 53% higher SOC content in depth of 0 to 5 and 5 to 10 cm than CT treatment (P < 0.05). However, seasonal variations in microbial biomass carbon (MBC) and particulate organic carbon (POC) were similar under NT and CT, and showed maximum values in before-winter anthesis stage. The dissolved organic carbon (DOC) trend was highest before sowing, decreased before the winter and jointed stages, and increased again during the anthesis stage. Particulate organic carbon, MBC, and DOC were all significantly higher with NT than with CT in the upper 10 cm. Soil depth affected SOC and its fraction which decreased from surface to subsurface soil. The POC, MBC, and DOC were highly correlated with the SOC. This study demonstrated that measurements of the effect of tillage practices on SOC based on SOC fractions should include both seasonal changes and profile distribution.
  • Authors:
    • Wilhelm, S.
    • Zheng, J.
    • Brummer, J. E.
    • Qian, Y.
    • Wang, L.
    • Parton, W. J.
  • Source: Biomass and Bioenergy
  • Volume: 75
  • Year: 2015
  • Summary: Long-term information on switchgrass (Panicum virgatum L.) as a biomass energy crop grown on marginally saline soil and the associated impacts on soil carbon (C) and nitrogen (N) dynamics, greenhouse gas (GHG) emissions, and best management practices (BMPs) are limited. In this study, we employed the DAYCENT model, based on a 4-year switchgrass field experiment, to evaluate the long-term biomass yield potential and environmental impacts, and further to develop BMPs for switchgrass in a semi-arid region.The model showed that long-term (14-year) annual mean biomass yields were 9.6 and 5.2Mgha-1 for irrigated and rainfed switchgrass systems, respectively. The simulated biomass yields correlated well with field-measured biomass with r2 values of 0.99 and 0.89 for irrigated and rainfed systems, respectively. Soil organic carbon (SOC) and soil total nitrogen (STN) accumulated rapidly after switchgrass establishment, with mean accrual rates of 0.99-1.13MgCha-1yr-1 and 0.04-0.08MgNha-1yr-1, respectively. Based on the outputs of numerous long-term model simulations with variable irrigation water supplies and N rates, the irrigation regime and N rate with the highest yield to input ratio were chosen as BMPs. The DAYCENT model predicted-BMP was irrigating every 14 days at 70% potential evapotranspiration combined with an N rate of 67kgha-1yr-1. Switchgrass established and produced biomass reasonably well in this semi-arid region; however, appropriate irrigation and N fertilization were needed for optimal biomass yield. Switchgrass had a great potential to sequester C into soils with low N2O emissions while supplying significant quantities of biomass for biofuel synthesis.
  • Authors:
    • Lemke, R. L.
    • Drury, C. F.
    • Smith, W. N.
    • Yang, J. Y.
    • Li, Z. T.
    • Grant, B.
    • He, W. T.
    • Li, X. G.
  • Source: NUTRIENT CYCLING IN AGROECOSYSTEMS
  • Volume: 101
  • Issue: 3
  • Year: 2015
  • Summary: The overall performance of the Decision Support System for Agrotechnology Transfer-Cropping System Model (DSSAT-CSM) was evaluated for simulating wheat (Triticum aestivum L.) yield, grain N uptake, soil organic C (SOC) and N (SON), soil water and nitrate-N (NO3-N) dynamics. The data used was from a long-term (1967-2005) spring wheat experiment conducted at Swift Current, Saskatchewan in the semi-arid Canadian prairies. Four treatments were selected: (1) continuous wheat receiving N and P fertilizer, Cont-W(NP); (2) continuous wheat receiving P only, Cont-W(P); and each phase of a fallow wheat rotation receiving N and P fertilizer, (3) W-F(NP) and (4) F-W(NP). The simulated grain yields matched the measurements well, with high d (0.74-0.83) and EF (0.16-0.33). The grain N uptake was also simulated satisfactorily with RMSE of 14-17 kg N ha(-1) and d of 0.66-0.81. DSSAT simulated topsoil (0-0.15 m) SOC and SON well in the drier period (1967-1991), whereas it underestimated SOC in the more humid period (1991-2003). The DSSAT successfully simulated soil water and NO3-N dynamics in 0-0.15 m depth, whereas it overestimated soil water and NO3-N in the deep layers and consequently underestimated NO3-N leaching, suggesting that further improvements in soil water module should be made for the semi-arid climatic conditions in Canadian prairies. Sensitivity results showed that soil water content was sensitive to both lower soil water and upper drainage limits in this study. The performances of DSSAT model to yield and soil dynamics were comparable with other models.
  • Authors:
    • Maghsoodi, M.
    • Razmjoo, J.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 1
  • Year: 2015
  • Summary: Physiological markers may provide a shortcut for identifying drought tolerance in alfalfa ( Medicago sativa L.). Thus, the objective of this study was to understand physiological properties of alfalfa to assess drought tolerance of its cultivars. Ten alfalfa cultivars (Qomi, Isfahani, Hamedani, Bami, Ordobadi, Gharayonje, Nikshahri, Yazdi, Baghdadi, and Cody) and four irrigation regimes (55, 65, 75, and 85% depletion of available soil water) were arranged as split plot in a completely randomized block design with three replications to determine the chlorophyll, carotenoid, soluble sugars, proline, relative water contents, and herbage yield response of alfalfa cultivars to drought stress. Physiological and herbage yield traits were drought level-cultivar-specific and discriminated the cultivars based on their drought tolerance. Based on the correlation between drought tolerance and measured traits at the highest drought level, carotenoid content ( r=0.94), was the most important marker followed by relative water content ( r=0.92) and soluble sugars content ( r=0.89), respectively, and Baghdadi was the most drought tolerant cultivar. The results showed that the physiological markers may be used to identify alfalfa germplasms for drought tolerance.
  • Authors:
    • Dang,Y. P.
    • Moody,P. W.
    • Bell,M. J.
    • Seymour,N. P.
    • Dalal,R. C.
    • Freebairn,D. M.
    • Walker,S. R.
  • Source: Soil & Tillage Research
  • Volume: 152
  • Year: 2015
  • Summary: In semi-arid sub-tropical areas, a number of studies concerning no-till (NT) farming systems have demonstrated advantages in economic, environmental and soil quality aspects over conventional tillage (CT). However, adoption of continuous NT has contributed to the build-up of herbicide resistant weed populations, increased incidence of soil- and stubble-borne diseases, and stratification of nutrients and organic carbon near the soil surface. Some farmers often resort to an occasional strategic tillage (ST) to manage these problems of NT systems. However, farmers who practice strict NT systems are concerned that even one-time tillage may undo positive soil condition benefits of NT farming systems. We reviewed the pros and cons of the use of occasional ST in NT farming systems. Impacts of occasional ST on agronomy, soil and environment are site-specific and depend on many interacting soil, climatic and management conditions. Most studies conducted in North America and Europe suggest that introducing occasional ST in continuous NT farming systems could improve productivity and profitability in the short term; however in the long-term, the impact is negligible or may be negative. The short term impacts immediately following occasional ST on soil and environment include reduced protective cover, soil loss by erosion, increased runoff, loss of C and water, and reduced microbial activity with little or no detrimental impact in the long-term. A potential negative effect immediately following ST would be reduced plant available water which may result in unreliability of crop sowing in variable seasons. The occurrence of rainfall between the ST and sowing or immediately after the sowing is necessary to replenish soil water lost from the seed zone. Timing of ST is likely to be critical and must be balanced with optimising soil water prior to seeding. The impact of occasional ST varies with the tillage implement used; for example, inversion tillage using mouldboard tillage results in greater impacts as compared to chisel or disc. Opportunities for future research on occasional ST with the most commonly used implements such as tine and/or disc in Australia's northern grains-growing region are presented in the context of agronomy, soil and the environment. Crown Copyright (C) 2014 Published by Elsevier B.V. All rights reserved.
  • Authors:
    • Adams,H. D.
    • Collins,A. D.
    • Briggs,S. P.
    • Vennetier,M.
    • Dickman,L. T.
    • Sevanto,S. A.
    • Garcia-Forner,N.
    • Powers,H. H.
    • McDowell,N. G.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 11
  • Year: 2015
  • Summary: Higher temperatures associated with climate change are anticipated to trigger an earlier start to the growing season, which could increase the terrestrial C sink strength. Greater variability in the amount and timing of precipitation is also expected with higher temperatures, bringing increased drought stress to many ecosystems. We experimentally assessed the effects of higher temperature and drought on the foliar phenology and shoot growth of mature trees of two semiarid conifer species. We exposed field-grown trees to a ~45% reduction in precipitation with a rain-out structure ('drought'), a ~4.8 °C temperature increase with open-top chambers ('heat'), and a combination of both simultaneously ('drought+heat'). Over the 2013 growing season, drought, heat, and drought+heat treatments reduced shoot and needle growth in pinon pine ( Pinus edulis) by ≥39%, while juniper ( Juniperus monosperma) had low growth and little response to these treatments. Needle emergence on primary axis branches of pinon pine was delayed in heat, drought, and drought+heat treatments by 19-57 days, while secondary axis branches were less likely to produce needles in the heat treatment, and produced no needles at all in the drought+heat treatment. Growth of shoots and needles, and the timing of needle emergence correlated inversely with xylem water tension and positively with nonstructural carbohydrate concentrations. Our findings demonstrate the potential for delayed phenological development and reduced growth with higher temperatures and drought in tree species that are vulnerable to drought and reveal potential mechanistic links to physiological stress responses. Climate change projections of an earlier and longer growing season with higher temperatures, and consequent increases in terrestrial C sink strength, may be incorrect for regions where plants will face increased drought stress with climate change.
  • Authors:
    • Almagro, M.
    • Albaladejo, J.
    • Garcia-Franco, N.
    • Martínez-Mena, M.
  • Source: Research Article
  • Volume: 153
  • Issue: 153
  • Year: 2015
  • Summary: Semiarid Mediterranean agroecosystems need the implementation of sustainable land management (SLM) practices in order to maintain acceptable levels of soil organic matter (SOM). The application of SLM practices helps to maintain soil structure and physical-chemical protection of soil organic carbon (SOC), hence improving soil carbon sequestration and mitigating CO2 emissions to the atmosphere. In an organic, rain-fed almond (Prunus dulcis Mill., var. Ferragnes) orchard under reduced tillage (RT), as the habitual management practice during the 14 years immediately preceding the experiment, we studied the effect of two agricultural management practices on soil aggregate distribution and SOC stabilization after four years of implementation. The implemented practices were (1) reduced tillage with a mix of Vicia sativa L. and Avena sativa L. as green manure (RTG) and (2) no-tillage (NT). Four aggregate size classes were differentiated by wet sieving (large and small macroaggregates, microaggregates, and the silt plus clay fraction), and the microaggregates occluded within small macroaggregates (SMm) were isolated. In addition, three organic C fractions were separated within the small macroaggregates and microaggregates, using a density fractionation method: free light fraction (free LF-C), intra-aggregate particulate OM (iPOM-C), and organic C associated with the mineral fraction (mineral-C). The results show that the combination of reduced tillage plus green manure (RTG) was the most-efficient SLM practice for SOC sequestration. The total SOC increased by about 14% in the surface layer (0-5cm depth) when compared to RT. Furthermore, green manure counteracted the effect of tillage on soil aggregate rupture. The plant residue inputs from green manure and their incorporation into the soil by reduced tillage promoted the formation of new aggregates and activated the subsequent physical-chemical protection of OC. The latter mechanism occurred mainly in the fine iPOM-C occluded within microaggregates and mineral-C occluded within small macroaggregates fractions, which together contributed to an increase of up to 30% in the OC concentration in the bulk soil. No-tillage favored the OC accumulation in the mineral-C within the small macroaggregates and in the fine iPOM-C occluded within microaggregates in the surface layer, and in the mineral-C occluded within the small macroaggregates and microaggregates at 5-15cm depth, but four years of cessation of tillage were not enough to significantly increase the total OC in the bulk soil. © 2015 Elsevier B.V..
  • Authors:
    • Tanaka, D.
    • Nichols, K.
    • Schmer, M.
    • Archer, D.
    • Hendrickson, J.
    • Liebig, M.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 6
  • Year: 2015
  • Summary: Cover crops can expand ecosystem services, though sound management recommendations for their use within semiarid cropping systems is currently constrained by a lack of information. This study was conducted to determine agroecosystem responses to late-summer seeded cover crops under no-till management, with particular emphasis on soil attributes. Short-term effects of late-summer seeded cover crops on soil water, available N, near-surface soil quality, and residue cover were investigated during three consecutive years on the Area IV Soil Conservation Districts Research Farm near Mandan, ND. Mean aboveground cover crop biomass was highly variable across years (1430, 96, and 937 kg ha -1 in 2008, 2009, and 2010, respectively), and was strongly affected by precipitation received within 14 d following cover crop seeding. During years with appreciable biomass production (2008 and 2010), cover crops significantly reduced available N in the 0.9-m depth the following spring ( P=0.0291 and 0.0464, respectively). Cover crop effects on soil water were subtle, and no differences in soil water were found between cover crop treatments and a no cover crop control before seeding cash crops the following spring. Late-summer seeded cover crops did not affect near-surface soil properties or soil coverage by residue. Soil responses to late-summer seeded cover crops did not differ between cover crop mixtures and monocultures. Late-summer seeded cover crops may enhance ecosystem services provided by semiarid cropping systems through biomass production and N conservation, though achieving these benefits in a consistent manner appears dependent on timely precipitation following cover crop seeding.
  • Authors:
    • Liang, L.
    • Jia, Z.
    • Wang, X.
  • Source: Soil and Tillage Research
  • Volume: 153
  • Year: 2015
  • Summary: Field experiments were conducted in 2008-2010 in the Loess Plateau of China to study the effects of straw incorporation on maize growth and biomass water use efficiency (WUE) under semi-arid condition in dark loessial soil. Low (LS 4.5tha-1), medium (MS 9.0tha-1), and high (HS 13.5 tha-1) levels of straw were incorporated into the surface soil combined with fixed levels of inorganic fertilizers (CK) as control. Straw incorporation compared with CK significantly improved biomass yield at the tasseling-maturity stage of maize and WUE at the jointing-ten leaf collar and the tasseling-grain filling stages. WUEs with LS and MS treatments were significantly lower than that with CK at the ten leaf collar-tasseling stage, although the WUEs with MS and HS treatments were significantly higher in the whole growth period. HS treatment compared with LS treatment significantly increased biomass yield at the ten leaf collar-maturity stage and WUE at the jointing-tasseling stage. Meanwhile, MS and HS treatments compared with LS treatment significantly increased the biomass yield at the late grow period. Straw incorporation significantly improved WUE at the sowing-jointing stage and soil organic carbon relative to CK. Biomass yield at the ten leaf collar stage and WUE in whole growth period with LS treatment were significantly higher compared with CK. WUE at the ten leaf collar-tasseling and the grain filling-maturity stages were significantly higher with HS treatment compared with CK. In the long term, the rational straw incorporation level in improving maize biomass yield and WUE was 9.0tha-1. © 2015 Elsevier B.V..
  • Authors:
    • Mauro, R.
    • Agnello, M.
    • Pesce, G.
    • Sortino, O.
    • Mauromicale, G.
  • Source: Industrial Crops and Products
  • Volume: 57
  • Year: 2014
  • Summary: Increasing the use of renewable energies as biomass offers significant opportunities for Europe to reduce greenhouse gas emission and secure its energy supply. To ensure that bioenergy develops in environmentally-compatible way, the availability of crops, such as perennials, adapted to cropping systems based on minimal production inputs and marginal lands with medium-low soil fertility, is strongly needed. To examine the potential ability in terms of biomass, achenes, and energy yield and the possible role in soil fertility conservation of two botanical varieties (cultivated and wild cardoon) of the C-3 Asteraceae, Cynara cardunculus L, a long-term experiment (seven cropping seasons) was carried out in a marginal farmland of Sicily (Southern Italy), with low soil fertility and without external inputs as fertilization, irrigation, weed and pest control from the second season onward. Under these conditions C. cardunculus improved soil fertility by increasing the soil organic matter content, organic C content, total nitrogen, assimilable P2O5 and exchangeable K, giving an annual harvestable biomass and energy yield of 14.6 t ha(-1) and 275 GJ ha(-1) (cultivated cardoon) and 7.4 t ha(-1) and 138 GJ ha(-1) (wild cardoon). The harvest time, in the third 10-day of August, allowed a very low biomass moisture, about 11% in cultivated cardoon and 7% in wild cardoon. Cultivated cardoon was capable of producing high yields until fifth season, therefore is indicated for medium long-time cropping systems. Wild cardoon showed a most stable yield pattern and plant survival over seasons, suggesting its particular suitability for perennial cropping systems of Mediterranean marginal areas. For these reasons, we have undertaken a breeding program aimed to improve the crop performances in terms of both biomass and energy yield (wild cardoon) and to stabilize the biomass production characteristics during crop ageing (cultivated cardoon). (C) 2014 Elsevier B.V. All rights reserved.