• Authors:
    • Deckers, J.
    • Govaerts, B.
    • Nyssen, J.
    • Araya, T.
    • Cornelis, W. M.
  • Source: Soil and Tillage Research
  • Volume: 148
  • Year: 2015
  • Summary: Field water conservation practices are a way to build resilience against drought by increasing productive green water through reducing runoff and evaporation and thereby boosting crop yield. A field study was undertaken on permanently kept rainfed experimental plots established in 2005 on a vertisol in order to evaluate two resource saving cropping systems based on conservation agriculture (CA) that integrate in situ soil and water conservation tillage practices (derdero+ and terwah+) as compared to a conventional system in terms of soil moisture, runoff, water loss (drainage and evapotranspiration together), water productivity and crop yield. The experimental layout was a randomized complete block design with three replications and a plot size of 5m×19m. The farming systems differed in tillage practice, but all had wheat, teff, barley and grass pea crops grown in rotation. The tillage treatments were (i) derdero+ (DER+) with a furrow and permanent raised bed planting system, plowed only by refreshing the furrow once at planting with no tillage on top of the permanently kept raised beds, 30% standing crop straw retention, and with ~20% of the crop residue being covered with soil during refreshing the furrow at planting, (ii) terwah+ (TER+) with furrows made at 1.5m intervals, plowed once at planting, 30% standing crop straw retention and fresh broad beds, and crop residue being partly covered with soil during tillage at planting, and (iii) conventional tillage (CT) with a minimum of three plain tillage operations and complete removal of crop straw. All plowing as well as the maintenance of the furrows of the permanent raised beds was done using a local ard plow called mahresha. Glyphosate was sprayed at 2lha-1 to control weeds before crop emergence, starting from 2007 with DER+ and TER+. Runoff was collected at the lower end of each plot in calibrated runoff collectors after each runoff event. Soil-water content was measured using the gravimetric method at 5-6 day intervals. Normalized Difference Vegetation Index (NDVI) was measured in the field at several phenological stages, using a handheld GreenSeeker™ Optical Sensor Unit. Soil-water storage (0-80cm soil depth) during the growing season was always highest with DER+ followed by TER+ and CT, whereas the opposite trend was observed for runoff. On the other hand, deep drainage and evapotranspiration was always highest in the DER+ compared to CT. NDVI records throughout the growing season were significantly highest with DER+ for wheat and grass pea, while the highest values were observed with TER+ when under teff. These values were directly proportional to the above ground crop biomass and yield. The grain and straw yield of wheat in 2009 was increased from 1.6 and 3.7tha-1 with CT to 2.6 and 5.2tha-1 with DER+, respectively. Our study demonstrates that field water conservation tillage practices that incorporate CA principles are effectively increasing green water in the root zone available for crops and thus, improve crop productivity and yields substantially on vertisols in drylands without other inputs.
  • Authors:
    • Tyler, D. D.
    • Keyser, P. D.
    • Allen, F. L.
    • Reed, D. L.
    • Taylor, A. M.
    • Ashworth, A. J.
  • Source: JOURNAL OF CLEANER PRODUCTION
  • Volume: 87
  • Year: 2015
  • Summary: As the use of second-generation biofuel crops increases, so do questions about sustainability, particularly their potential to affect fossil energy consumption and greenhouse gas emissions. This study used a life-. cycle approach to compare environmental impacts associated with three switchgrass (Panicum virgatum L) production scenarios: i) regional production from a pool of Tennessee farmers based on in-field inputs and biomass yield; ii) varying nitrogen (N)-input levels from a replicated field study for 8-yrs i.e., a 100% and 9% decrease, and an 81% and 172% increase from 'baseline levels' of N inputs used under objective i; and, iii) a legume-intercrop system compared to baseline levels in order to determine effects of displacing synthetic-N with legumes. When compared across all agricultural inputs, nitrogen fertilizer production and breakdown resulted in the greatest environmental impacts. Although fertilization increased lignocellulosic yields, a 100% reduction in N-inputs from baseline levels reduced the formation of carbon, methane, and nitrous oxides per unit of production, (or dry tonne of biomass over 10-yrs) compared to a 172% increase. Switchgrass yield response indicated a 'less is more' scenario, as inputs beyond the current recommended input level (67 kg N ha(-1)) are not environmentally remunerating. During switchgrass biomass production, inputs with lesser impacts included phosphorus, herbicides, pesticides, and diesel fuel. Legume-intercropping reduced greenhouse gas emissions and groundwater acidification (5% and 27% reduction in global warming potential and formation of acidifying species, respectively) compared with the 67 kg N ha irate. Although N-fertilizers impact environmental sustainability of regional switchgrass feedstock production, environmental consequences can be reduced under proper N-management i.e., <= 67 kg N ha(-1) or legume intercropping. However, given that the aim of second-generation feedstocks is to reduce the current reliance on fossil fuels, their production still requires fossil energy-based inputs. Consequently, greenhouse gas reductions and the extent of cleaner feedstock production during the agricultural biofuel supply chain is contingent upon input management and optimizing synthetic fertilizer usage. (C) 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license.
  • Authors:
    • McCorkell, B.
    • McHenry, M.
    • Hulugalle, N.
    • Kristiansen, P.
    • Bajgai, Y.
  • Source: NUTRIENT CYCLING IN AGROECOSYSTEMS
  • Volume: 101
  • Issue: 1
  • Year: 2015
  • Summary: Despite scant crop residue input, tillage to control weeds in vegetable systems reduces soil organic carbon (SOC) levels. We hypothesized that vegetable production systems could be made more resistant to the negative effects of tillage on SOC by including a high-residue crop in rotation. Effect of sweet corn (Zea mays L. var. rugosa) residue incorporation in a corn-cabbage (Brassica oleracea L.) rotation in two soil management systems (SMS) (organic or conventional) in two soil types [a Chromosol (Alfisol) and a Vertosol (Vertisol)] on SOC and microbial biomass C (MBC) levels was tested for 2 years. Confounded factors (weed management and fertilisers) in the field experiment were separated in a multi-factorial laboratory experiment. In the field, total organic C (TOC) concentration was increased by 6.5 % in the 0-0.1 m depth by incorporating residue; however SMS exhibited inconsistent results. Organic fertilisers increased TOC whilst simulated tillage decreased it in laboratory. Soil MBC data showed that the biological fertility of soil can be improved by incorporating residues or by combining residue with organic fertiliser. In field residue incorporation in soil increased TOC, but organic fertilisers behaved inconsistently. However, in a laboratory microcosm, both residue and organic fertilisers individually mitigated tillage-induced loss of TOC.
  • Authors:
    • Piccolo, M. D. C.
    • Vieira, F. C. B.
    • Zanatta, J. A.
    • Gomes, J.
    • Bayer, C.
    • Dieckow, J.
    • Six, J.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 146
  • Issue: Pt. B
  • Year: 2015
  • Summary: Soil nitrous oxide (N2O) emissions are affected by management practices, but little information is available on the interactive effects of tillage, cropping systems and N sources in tropical and subtropical soils. In an 18-yr old experiment located in a subtropical Acrisol of Southern Brazil we conducted a sequence of two trials. The 1-year trial (October 2003-2004) was set to evaluate the long-term effects of tillage [CT: conventional; and NT: no-tillage] and cropping systems [O/M: black oat (Avena strigosa Schreb.)/maize (Zea mays L.); and V/M: vetch (Vicia sativa L.)/maize] on soil N2O emissions, either in the post-management period (45 days after desiccation and knife-rolling of winter cover crops) or in the whole year. The second and short-term trial (October-November 2004) was carried out to compare the impact of N sources [urea (mineral) and legume-residue of vetch (biologically fixed), both at 180kgNha-1] on soil N2O emissions during 53 days after cover-crop management. Air sampling was carried out by static chambers and N2O analysis by gas chromatography. In the 45-day post-management period of the 1-year trial, soil N2O emissions were practically not affected by tillage systems, but increased 4 times due to vetch residues (average of 0.40±0.08kgNha-1 in V/M versus 0.10±0.05kgNha-1 in O/M) and related with soil contents of NO3 --N, NH4 +-N, and dissolved organic C (DOC). Over the whole year, soil N2O emissions under CT were similar for grass- and legume-based cropping systems and averaged 0.43±0.17kgNha-1, while NT exacerbated N2O emissions in the legume-based cropping system (0.80±0.07kgNha-1 in V/M versus -0.07±0.06kgNha-1 in O/M). Maize yield was not affected by tillage, but increased from 2.32Mgha-1 in O/M to 4.44Mgha-1 in V/M. Yield-scaled N2O emissions varied from -33g N2O-NMg-1 grain in NT O/M to 179g N2O-NMg-1 grain in NT V/M, and were intermediate in CT soil (106 and 156g N2O-NMg-1grain in V/M and O/M cropping systems, respectively). In the short-term trial, the N2O emitted in excess relative to the control treatment (O/M without N fertilizer) was at least 3 times greater with urea-N (0.44% of applied N) than with legume-residue-Nsource (0.13% of applied N). Yield-scaled N2O emission after vetch residues management (67gNMg-1 grain) was half of that after urea-N application (152gNMg-1 grain). Partially supplying the maize N requirements with winter legume cover-crops may be a feasible strategy to mitigate soil N2O emissions in the subtropical conservation agriculture.
  • Authors:
    • Paustian, K.
    • Bernoux, M.
  • Source: Soil Carbon: Science, Management and Policy for Multiple Benefits
  • Year: 2015
  • Summary: Terrestrial ecosystems play a major role in regulating the concentrations of three greenhouse gases (CO 2, CH 4 and N 2O), of which CO 2 is the most important in terms of the impact on the global radiative balance. Soils play a major role in the global carbon (C) cycle and CO 2 dynamics; thus, management of soil carbon appears essential and more and more inevitable. The capacity of natural and managed agroecosystems to remove carbon dioxide from the atmosphere in a manner that is not immediately re-emitted into the atmosphere is known as carbon sequestration: carbon dioxide is absorbed by vegetation through photosynthesis and stored as carbon in biomass and soils, and released through autotrophic and heterotrophic respiration. Forests, croplands and grasslands can store large amounts of carbon in soils for relatively long periods. Soils are the larger terrestrial pool of organic carbon. Moreover, soil carbon sequestration is beneficial for soil quality, both over the short term and long term, and can be achieved through land management practices adapted to the specific site characteristics. The ability of soils to sequester carbon depends on climate, soil type, vegetation cover and land management practices. According to the fourth assessment report of the Intergovernmental Panel on Climate Change (IPCC), the total technical greenhouse gas (GHG) mitigation potential of agriculture (considering all gases and sources) is estimated to be in the range 4.5-6 Gt CO 2-equivalent year -1 by 2030. Estimates indicate that many of these options are of relatively low cost and generate significant co-benefits in the form of improved agricultural production systems, resilience and other ecosystem services. Moreover, many of the technical options are readily available and could be deployed immediately. About 90% of this potential can be achieved by soil C sequestration through cropland management, grazing land management, restoration of organic soils and degraded lands, and water management in rainfed and irrigated croplands. In most cases, such management practices include the management of organic residues produced on site or coming from outside the field or the farm. It has been estimated that the global world production of residues in the agriculture sector is about 3.8 Pg C and, to date, the use of this resource has not been optimized; a large part is still being burned. Over the past two decades, other practices have been tested and are still controversial, such as biochar or chipped ramial wood application in cultivated fields. Biochar is a stabile carbon amendment, produced from pyrolysis of biomass, which may increase biomass productivity as well as sequester C from the source biomass. The scientific validation of these practices is still incomplete. Full participation of the agricultural sector in GHG mitigation still faces some challenges and barriers related to measurement, monitoring and reporting requirements in C offset markets. Further improvements are needed in methodologies and approaches that would help project designers and policy makers to integrate significant mitigation effects in agriculture development projects.
  • Authors:
    • Höper, H.
    • Liebersbach, H.
    • Beyer, C.
  • Source: Journal of Plant Nutrition and Soil Science
  • Volume: 178
  • Issue: 1
  • Year: 2015
  • Summary: To date there is still a lack of reliable data on greenhouse gas emissions from drained fens needed to determine the climatic relevance of land use and land use change on peatlands and to supply the National Inventory Report for the German Greenhouse Gas Inventory. In this study we present the results of monthly-based multiyear measurements of CO2, N2O and CH4 flux rates in two drained agriculturally used fen ecosystems in NW Germany (cropland and grassland) over a period of 4.5 y using transparent and opaque closed chambers. CO2 exchange was modelled at high resolution with temperature and photosynthetic active radiation. The measured and modelled values fit very well (R2 ≥ 0.93). Annual GHG and Global Warming Potential (GWP) balances were determined. Net CO2 emissions at the cropland and grassland sites were similarly high, taking into account changes in management; net ecosystem C balance amounted to about 4.0 to 5.0 Mg C ha-1 y-1. Emissions of N2O and CH4 were low at both sites. The mean GWP balance for a time frame of 100 y (GWP100) amounted to about 17.0 to 19.0 Mg CO2-eq. ha-1 y-1. The unexpectedly low greenhouse gas emissions from the cropland site are attributed to the high water table and a change in crop management. The change from corn for silage to corn-cob mix lead transiently to rather small greenhouse gas emissions. The study confirms the need for multiyear measurements taking climatic and management variation into account.
  • Authors:
    • Anand, M. H.
    • Byju, G.
    • Moorthy, S. N.
  • Source: COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS
  • Volume: 46
  • Issue: 2
  • Year: 2015
  • Summary: A glasshouse incubation experiment was conducted to study the carbon (C) and nitrogen (N) mineralization of municipal solid waste compost (MSWC) added at differential rates to a laterite soil where cassava has been continuously cultivated for the past 10 years. The rate of C mineralization from added substrates increased with increasing rates of addition of MSWC. Available N significantly increased with increase in the rate of application of MSWC. There was a decreasing trend in E 465/E 665 ratio of humic acid as we increased the rate of application of MSWC from 2.5 to 20 t ha -1. The Cross Polarization Magic Angle Spinning (CPMAS) 13C NMR spectral analysis revealed that there are differences in the rate of humification of added MSWC, and application of MSWC at 15 t ha -1 resulted in least humification with the greatest alkyl C, lowest aromatic C, and greater O-alkyl C content. The decomposition rate (R) was found to be greater for this treatment. The residual C in soil was found to increase over time coincident with greater rates of MSWC application, indicating increased C stabilization, which could improve soil quality.
  • Authors:
    • Riseman, A.
    • Chapagain, T.
  • Source: NUTRIENT CYCLING IN AGROECOSYSTEMS
  • Volume: 101
  • Issue: 1
  • Year: 2015
  • Summary: Enhancing soil organic carbon (SOC), nitrogen (N) and water use efficiency (WUE) are significant challenges in intensive wheat production. An intercropping system combining wheat and grain legumes may help maintain SOC, soil mineral N and WUE while also providing an opportunity to sequester carbon (C) in low input organic systems. We grew wheat (Triticum aestivum cv. 'Scarlet') as a monoculture and intercropped with either common bean (Phaseolus vulgaris cv. 'Red Kidney', or cv. 'Black Turtle'), or fava bean (Vicia faba cv. 'Bell') in rows of 1:1, 2 wheat: 1 bean or broadcast arrangement without fertilizers for 2 years to assess the effects of genotype and spatial arrangement on biological nitrogen fixation and seasonal transfer, WUE, gross ecosystem photosynthesis (GEP), and net ecosystem productivity (NEP). Stable isotope methods (C-13 and N-15 natural abundance) were used to quantify C and N within the plant and soil system. Field CO2 exchange measurements used a dynamic closed transparent chamber connected to a portable CO2 analyzer. Intercropped plots had higher percent N derived from symbiotic N-2 fixation, and increased C and N accumulation compared to monocultured wheat. The fava bean cv. Bell intercrops showed increased nodulation (60-80 % more nodules) and percent N derived from symbiotic N-2 fixation (10-12 % higher) compared to common beans resulting in the fixation of 74 kg N ha(-1) biologically from the 1:1 arrangement. The highest rate of N-transfer (13 %) was observed in the wheat-fava bean cv. Bell combination when planted in the 1:1 arrangement. All intercrops accumulated more N in shoot biomass compared to monoculture wheat with wheat-fava bean cv. Bell (1:1 arrangement) accumulating the highest N (34 kg N ha(-1), i.e., 176 % higher) and C (214 g C m(-2) year(-1), i.e., 26 % higher). All plots fixed the most CO2 (i.e., greatest GEP) during mid-growth stage (50 days after seeding i.e., prior to flowering) however, wheat-fava bean cv. Bell in the 1:1 arrangement displayed the greatest NEP sequestering C at the seasonal daytime average rate of 208 mg C m(-2) h(-1) (i.e., 7 % higher than wheat monoculture plots). Intrinsic WUE of wheat, as indicated by delta C-13, was also improved when grown with fava bean cv. Bell or common bean cv. Red Kidney. This study demonstrated that intercropping wheat and fava bean is an effective strategy to achieve greater nitrogen fixation and transfer to the wheat counterparts, higher WUE, and ecosystem productivity than wheat monocultures in areas with low soil N and C. Furthermore, the wheat-fava bean cv. Bell (1:1 arrangement) was more productive than either the 2:1 or mixed planting arrangements.
  • Authors:
    • Chuine, I.
    • Regniere, J.
    • Crespo-Perez, V.
    • Rebaudo, F.
    • Dangles, O.
  • Source: GLOBAL CHANGE BIOLOGY
  • Volume: 21
  • Issue: 1
  • Year: 2015
  • Summary: Climate induced species range shifts might create novel interactions among species that may outweigh direct climatic effects. In an agricultural context, climate change might alter the intensity of competition or facilitation interactions among pests with, potentially, negative consequences on the levels of damage to crop. This could threaten the productivity of agricultural systems and have negative impacts on food security, but has yet been poorly considered in studies. In this contribution, we constructed and evaluated process-based species distribution models for three invasive potato pests in the Tropical Andean Region. These three species have been found to co-occur and interact within the same potato tuber, causing different levels of damage to crop. Our models allowed us to predict the current and future distribution of the species and therefore, to assess how damage to crop might change in the future due to novel interactions. In general, our study revealed the main challenges related to distribution modeling of invasive pests in highly heterogeneous regions. It yielded different results for the three species, both in terms of accuracy and distribution, with one species surviving best at lower altitudes and the other two performing better at higher altitudes. As to future distributions our results suggested that the three species will show different responses to climate change, with one of them expanding to higher altitudes, another contracting its range and the other shifting its distribution to higher altitudes. These changes will result in novel areas of co-occurrence and hence, interactions of the pests, which will cause different levels of damage to crop. Combining population dynamics and species distribution models that incorporate interspecific trade-off relationships in different environments revealed a powerful approach to provide predictions about the response of an assemblage of interacting species to future environmental changes and their impact on process rates.
  • Authors:
    • Freebairn, D. M.
    • Dalal, R. C.
    • Seymour, N. P.
    • Bell, M. J.
    • Moody, P. W.
    • Dang, Y. P.
    • Walker, S. R.
  • Source: Soil and Tillage Research
  • 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.