• Authors:
    • da Silva, D. A.
    • Ferreira de Souza, L. C.
    • Tadeu Vitorino, A. C.
    • Goncalves, M. C.
  • Source: Bragantia
  • Volume: 70
  • Issue: 1
  • Year: 2011
  • Summary: Soil physical degradation, like compaction, reduces water movement and root development. Soil structure is considered one of most importance to agriculture and closely related to it are other fundamental properties in soil-plant relationship. The objective of this study was to evaluate the effect of crop sequences on physical attributes. The research was realized in 2004/05 and 2005/06 growing seasons, in a Typic Clayey Rhodic Hopludox, under eight years of no-tillage system, at Dourados (MS). The experiment was a randomized complete block design, with three replications. Treatments were constituted by cover crops: sunflower (Helianthus annuus L.), sunnhemp (Crotalaria juncea L.), hairy vetch (Vicia villosa Roth), mixture of sunnhemp + black oat (Avena strigosa Schreb), and mixture of black oat + hairy vetch + oilseed radish (Raphanus sativus L. Var. oliferus Metzg). Differences were not observed in soil density, porosity and aggregation rate when it was cultivated with sunflower, hairy vetch, sunnhemp, or the mixtures. Differences were observed in soil physical properties between 0-5 cm layer and 5-10cm 10-20 cm layers, but no differences between 5-10 cm and 10-20cm layers. Soil carbon trend to higher contents in crops with high production of surface residues, although differences in carbon contents were insufficient to modify aggregation.
  • Authors:
    • de Campos, B. -H. C.
    • Carneiro Amado, T. J.
    • Bayer, C.
    • da Silveira Nicoloso, R.
    • Fiorin, J. E.
  • Source: Revista Brasileira de Ciência do Solo
  • Volume: 35
  • Issue: 3
  • Year: 2011
  • Summary: Soil organic matter (SOM) plays a crucial role in soil quality and can act as an atmospheric C-CO2 sink under conservationist management systems. This study aimed to evaluate the long-term effects (19 years) of tillage (CT-conventional tillage and NT-no tillage) and crop rotations (R0-monoculture system, R1-winter crop rotation, and R2- intensive crop rotation) on total, particulate and mineral-associated organic carbon (C) stocks of an originally degraded Red Oxisol in Cruz Alta, RS, Southern Brazil. The climate is humid subtropical Cfa 2a (Koppen classification), the mean annual precipitation 1,774 mm and mean annual temperature 19.2 degrees C. The plots were divided into four segments, of which each was sampled in the layers 0-0.05, 0.05-0.10, 0.10-0.20, and 0.20-0.30 m. Sampling was performed manually by opening small trenches. The SOM pools were determined by physical fractionation. Soil C stocks had a linear relationship with annual crop C inputs, regardless of the tillage systems. Thus, soil disturbance had a minor effect on SOM turnover. In the 0-0.30 m layer, soil C sequestration ranged from 0 to 0.51 Mg ha(-1) yr(-1), using the CT R0 treatment as base-line; crop rotation systems had more influence on soil stock C than tillage systems. The mean C sequestration rate of the cropping systems was 0.13 Mg ha(-1) y(-1) higher in NT than CT. This result was associated to the higher C input by crops due to the improvement in soil quality under long-term no-tillage. The particulate C fraction was a sensitive indicator of soil management quality, while mineral-associated organic C was the main pool of atmospheric C fixed in this clayey Oxisol. The C retention in this stable SOM fraction accounts for 81 and 89% of total C sequestration in the treatments NT R1 and NT R2, respectively, in relation to the same cropping systems under CT. The highest C management index was observed in NT R2, confirming the capacity of this soil management practice to improve the soil C stock qualitatively in relation to CT R0. The results highlighted the diversification of crop rotation with cover crops as a crucial strategy for atmospheric C-CO2 sequestration and SOM quality improvement in highly weathered subtropical Oxisols.
  • Authors:
    • Devine, S.
    • Markewitz, D.
    • Hendrix, P.
    • Coleman, D.
  • Source: Forest Science
  • Volume: 57
  • Issue: 1
  • Year: 2011
  • Summary: Forest succession (FS) and no-till (NT) agriculture are generally assumed to have a beneficial effect on surficial soil organic C (SOC) stocks compared with conventional tillage (CT) management; however, land use effects to depths >30 cm remain uncertain. In this research we compared SOC contents and composition to 2 m under CT, NT, and FS at the 30-year Horseshoe Bend agroecosystem experiment in Athens, Georgia, USA. Soils from 0 to 2 m were fractionated into particulate organic C (POC) (53-2000 m) and fine C (<53 m) fractions, and bulk soil delta 13C signatures were determined. Soils from 0 to 28 cm were dry- and wet-sieved to estimate aggregate stability. Soil solutions were also collected at 0, 15, and 100 cm for dissolved organic C (DOC) analysis. Full-profile (0-2 m) SOC storage is 52 Mg ha -1 in CT, 60 Mg ha -1 in NT, and 62 Mg ha -1 in FS. Significant differences are limited to 0-5 cm and are linked to enhanced aggregate stability under NT and FS. Increases in subsoil POC under FS and changes in soil delta 13C and C/N ratio indicate that substantial subsoil C cycling has occurred. DOC fluxes at 0 cm were significantly greater under NT (200 kg ha -1 year -1) and FS (210 kg ha -1 year -1) than under CT (80 kg ha -1 year -1). DOC fluxes at 15 cm are estimated to be 20 kg ha -1 year -1 under CT and NT and 40 kg ha -1 year -1 under FS. At 100 cm, DOC fluxes are 2 kg ha -1 year -1, regardless of land use. An increase in FS POC of 2 Mg ha -1 from 15 to 100 cm outweighs cumulative differences in DOC input to this layer, implicating deep forest rooting and bioturbation as active mechanisms in subsoil C change. Whereas differences in SOC content were concentrated near the surface, dynamic changes in C cycling extend well below the plow layer.
  • Authors:
    • Diaz-Rossello, R.
    • Duran, H.
  • Source: Agrociencia
  • Volume: 15
  • Issue: 2
  • Year: 2011
  • Summary: Pastoral dairy farming systems in Uruguay exhibit an accelerated process of intensification with major changes in soil management during the last four decades. However, the production systems were always based on the same concept of sustainable rotations of annual forage crops and perennial grasses sown in association with legumes. The soil organic carbon (OC) in the plots of the Dairy Experimental Farm at La Estanzuela was monitored since 1974 up to 2010. Those records quantify the effect on OC dynamics of four production systems with different soil management carried out in long periods. This information is extremely relevant considering that survey studies showed that commercial dairy farming systems followed the same general pathway of technical changes. The extreme modification in tillage, animal stocking rate and feed imported to the farm determined two contrasting periods in the OC dynamics. Heavy losses of OC were estimated at an average of 0.89 Mg ha -1 year -1 during a first period of 17 years. This tendency was reversed for the following 18 years when OC increased at 0.94 Mg ha -1 year -1. Three major management factors are discussed to explain the fast build up of OC: the progressive tillage reduction, improvements in pasture and forage crop productivity and imported feed coming into the system. The large OC and N gains in semi-confinement paddocks are discussed as an opportunity to capitalize the high nutrient availability in the soil for crop production.
  • Authors:
    • dos Santos, N. Z.
    • Dieckow, J.
    • Bayer, C.
    • Molin, R.
    • Favaretto, N.
    • Pauletti, V.
    • Piva, J. T.
  • Source: Soil & Tillage Research
  • Volume: 111
  • Issue: 2
  • Year: 2011
  • Summary: To improve C sequestration in no-till soils requires further development of crop rotations with high phytomass-C additions. The objectives of this study were (i) to assess long-term (17 years) contributions of cover crop- or forage-based no-till rotations and their related shoot and root additions to the accumulation of C in bulk and in physical fractions of a subtropical Ferralsol (20-cm depth); and (ii) infer if these rotations promote C sequestration and reach an eventual C saturation level in the soil. A wheat (Triticum aestivum L., winter crop)-soybean (Glycine max (L.) Merr, summer crop) succession was the baseline system. The soil under alfalfa (Medicago sativa L, hay forage) intercropped every three years with maize (Zea mays L., summer crop) had the highest C accumulation (0.44 Mg C ha(-1) year(-1)). The bi-annual rotation of ryegrass (Lolium multiflorum Lam., hay winter forage)-maize-ryegrass-soybean had a soil C sequestration of 0.32 Mg C ha(-1) year(-1). Among the two bi-annual cover crop-based rotations, the vetch (Vicia villosa Roth, winter cover crop)-maize-wheat-soybean rotation added 7.58 Mg C ha(-1) year(-1) as shoot plus root and sequestered 0.28 Mg C ha(-1) year(-1). The counterpart grass-based rotation of oat (Avena strigosa Schreb., winter cover crop)-maize-wheat-soybean sequestered only 0.16 Mg C ha(-1) year(-1), although adding 13% more C (8.56 Mg ha(-1) year(-1)). The vetch legume-based rotation, with a relative conversion factor (RCF) of 0.147, was more efficient in converting biomass C into sequestered soil C than oat grass-based rotation (RCF = 0.057). Soil C stocks showed a close relationship (R(2) = 0.72-0.98, P < 0.10) with root C addition, a poor relationship with total C addition and no relationship with shoot C addition. This suggests a more effective role of root than shoot additions in C accumulation in this no-till soil. Most of the C accumulation took place in the mineral-associated organic matter (71-95%, in the 0-5 cm layer) compared to the particulate organic matter. The asymptotic relationship between root C addition and C stocks in bulk soil and in mineral-associated fraction supports the idea of C saturation. In conclusion, forages or legume cover crops contribute to C sequestration in no-till tropical Ferrasols, and most of this contribution is from roots and stored in the mineral-associated fraction. This combination of soil and rotations can reach an eventual soil C saturation.
  • Authors:
    • Duboc, O.
    • Zehetner, F.
    • Gerzabek, M. H.
  • Source: Journal of Sustainable Agriculture
  • Volume: 35
  • Issue: 6
  • Year: 2011
  • Summary: The increase in crop production brought by the green revolution in India is now shadowed by new challenges related to soil degradation (e.g., erosion, decline of soil organic matter content, salinization) and scarcity of water resources. The present work particularly discusses the contribution of no-till and organic farming, which are increasingly being adopted in India, to meet the increasing food demand in a sustainable way. Under no-till, erosion is reduced to rates close to those found in natural ecosystems, provided enough mulch is retained at the surface which is usually not the case in India, because of competing uses, for example, fodder, fuel, construction material, and also crop residue burning for land preparation. No-till should therefore not be considered separately from complementary measures, aiming at retaining mulch on the soil surface. Efficient recycling of organic material needs to be implemented concomitantly with diversifying fodder and fuel sources which requires enhancing the multifunctionality of farming systems. These prerequisites make it difficult for farmers to adopt no-till, particularly the poorer ones for whom experimentation with new techniques often involve unbearable financial risks. Organic farming apprehends the farm as an organism, and is thus a good option to improve sustainability as introduced above, by e.g., closing nutrient cycling. However, organic farming typically implies tillage for weed control (no chemical herbicides). "Natural farming," as promoted by Fukuoka (197834. Fukuoka, M. 1978. The one-straw revolution: an introduction to natural farming, Rodale Press. View all references) combines no-till with organic farming. An overview of available literature on Indian experiences with "natural farming," most of it originating from unconventional sources (i.e., reports available on Internet, but no peer reviewed literature) indicates that crop yields can compare well with the highest yields in a particular region. Increased productivity and environmental benefits are also often mentioned. The limited accuracy of these sources makes it necessary to pursue further investigations, and we conclude with propositions for future work in this context. This should start with a rigorous assessment of existing " natural farming" systems regarding their productivity and environmental benefits, in order to demonstrate its potential before starting projects that promote the system for broader adoption.
  • Authors:
    • Fisher, K. A.
    • Momen, B.
    • Kratochvil, R. J.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 2
  • Year: 2011
  • Summary: Agricultural nutrient runoff to the Chesapeake Bay has been under intense scrutiny for more than a decade in Maryland. One method for capturing these nutrients, especially N, is the use of winter cover crops. This study compared various broadcast cover crop treatments with and without soil incorporation to planting winter cover crop seed with a no-till drill. Seedling emergence and N uptake were the dependent variables measured for two planting dates and seven planting methods. The effects of planting date and planting method for winter wheat ( Triticum aestivum L.) and cereal rye ( Secale cereale L.) following corn ( Zea mays L.) harvest were investigated at two locations. The study was conducted over two winter cover crop growing seasons: 2007-2008 and 2008-2009. Treatments that incorporated the seed into the soil consistently established better stands of cover crops and took up more N regardless of fluctuations in temperature, rainfall, and planting date. Early planted cover crops consistently took up more N than those planted on the later planting date. Performance of the broadcast treatments was highly dependent on rainfall and mild temperatures for success, but did take up notable amounts of N when planted early under good growing conditions. The few differences that were found in the N uptake between wheat and rye within the same planting treatment always indicated that the rye achieved better N uptake than wheat.
  • Authors:
    • Franzluebbers, A. J.
    • Causarano, H. J.
    • Norfleet, M. L.
  • Source: Plant and Soil
  • Volume: 338
  • Issue: 1-2
  • Year: 2011
  • Summary: Prediction of soil organic C sequestration with adoption of various conservation agricultural management approaches is needed to meet the emerging market for environmental services provided by agricultural land stewardship. The soil conditioning index (SCI) is a relatively simple model used by the USDA-Natural Resources Conservation Service to predict qualitative changes in soil organic matter. Our objective was to develop a quantitative relationship between soil organic C derived from published field studies in the southeastern USA and SCI scores predicted from matching management conditions. We found that soil organic C sequestration (at 20 +/- 5 cm depth) could be reliably related to SCI across a diversity of studies in the region using the regression slope: 1.65 Mg C ha(-1) SCI(-1) [which translated into a rate of 0.25 +/- 0.04 Mg C ha(-1) yr(-1) SCI(-1) (mean +/- standard error of 31 slope estimates)]. The calibration of soil organic C on SCI scores will allow SCI to become a quantitative tool for natural resource professionals to predict soil organic C sequestration for farmers wanting to adopt conservation practices.
  • Authors:
    • Gatiboni, L. C.
    • Meirelles Coimbra, J. L.
    • Nicoloso Denardin, R. B.
    • Wildner, L. do P.
  • Source: Revista Brasileira de Ciência do Solo
  • Volume: 35
  • Issue: 4
  • Year: 2011
  • Summary: The decomposition of plant residues is a biological process mediated by soil fauna, but few studies have been done evaluating its dynamics in time during the process of disappearance of straw. This study was carried out in Chapeco, in southern Brazil, with the objective of monitoring modifications in soil fauna populations and the C content in the soil microbial biomass (C-SMB) during the decomposition of winter cover crop residues in a no-till system. The following treatments were tested: 1) Black oat straw (Avena strigosa Schreb.); 2) Rye straw (Secale cereale L.); 3) Common vetch straw (Vicia sativa L.). The cover crops were grown until full flowering and then cut mechanically with a rolling stalk chopper. The soil fauna and C content in soil microbial biomass (C-SMB) were assessed during the period of straw decomposition, from October 2006 to February 2007. To evaluate CsmB by the irradiation-extraction method, soil samples from the 0-10 cm layer were used, collected on eight dates, from before until 100 days after residue chopping. The soil fauna was collected with pitfall traps on seven dates up to 85 days after residue chopping. The phytomass decomposition of common vetch was faster than of black oat and rye residues. The C-SMB decreased during the process of straw decomposition, fastest in the treatment with common vetch. In the common vetch treatment, the diversity of the soil fauna was reduced at the end of the decomposition process.
  • Authors:
    • Rickman, R. W.
    • Liang, Y.
    • Albrecht, S. L.
    • Machado, S.
    • Kang, S.
    • Gollany, H. T.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 1
  • Year: 2011
  • Summary: Long-term field experiments (LTE) are ideal for predicting the influence of agricultural management on soil organic carbon (SOC) dynamics and examining biofuel crop residue removal policy questions. Our objectives were (i) to simulate SOC dynamics in LTE soils under various climates, crop rotations, fertilizer or organic amendments, and crop residue managements using the CQESTR model and (ii) to predict the potential of no-tillage (NT) management to maintain SOC stocks while removing crop residue. Classical LTEs at Champaign, IL (1876), Columbia, MO (1888), Lethbridge, AB (1911), Breton, AB (1930), and Pendleton, OR (1931) were selected for their documented history of management practice and periodic soil organic matter (SOM) measurements. Management practices ranged from monoculture to 2- or 3-yr crop rotations, manure, no fertilizer or fertilizer additions, and crop residue returned, burned, or harvested. Measured and CQESTR predicted SOC stocks under diverse agronomic practices, mean annual temperature (2.1-19 degrees C), precipitation (402-973 mm), and SOC (5.89-33.58 g SOC kg(-1)) at the LTE sites were significantly related (r(2) = 0.94, n = 186, P < 0.0001) with a slope not significantly different than 1. The simulation results indicated that the quantities of crop residue that can be sustainably harvested without jeopardizing SOC stocks were influenced by initial SOC stocks, crop rotation intensity, tillage practices, crop yield, and climate. Manure or a cover crop/intensified crop rotation under NT are options to mitigate loss of crop residue C, as using fertilizer alone is insufficient to overcome residue removal impact on SOC stocks.