• Authors:
    • Dresboll, D. B.
    • Thorup-Kristensen, K.
    • Kristensen, H. L.
  • Source: European Journal of Agronomy
  • Volume: 37
  • Issue: 1
  • Year: 2012
  • Summary: One of the core ideas behind organic production is that cropping systems should be less dependent on import of resources, and minimize negative effects on the surrounding environment compared to conventional production. However, even when clearly complying with regulations for organic production, it is not always obvious that these goals are reached. As an example, strong dependence on import of manure is often seen in current organic production, especially in systems producing high value crops such as vegetable crops. The aim of the present study was to test novel approaches to organic rotations, designed to reduce the reliance on import of external resources significantly. We compared a conventional system (C) and an organic system relying on manure import for soil fertility (O1) to two novel systems (O2 and O3) all based on the same crop rotation. The O2 and O3 systems represented new versions of the organic rotation, both relying on green manures and catch crops grown during the autumn after the main crop as their main source of soil fertility, and the O3 system further leaving rows of the green manures to grow as intercrops between vegetable rows to improve the conditions for biodiversity and natural pest regulation in the crops. Reliance on resource import to the systems differed, with average annual import of nitrogen fertilizers of 149, 85, 25 and 25 kg N ha(-1) in the C, O1, O2 and O3 systems, respectively. As expected, the crop yields were lower in the organic system. It differed strongly among crop species, but on average the organic crops yielded c. 82% of conventional yields in all three organic systems, when calculated based on the area actually grown with the main crops. In the O3 system some of the area of the vegetable fields was allocated to intercrops, so vegetable yields calculated based on total land area was only 63% of conventional yields. Differences in quality parameters of the harvested crops, i.e. nutrient content, dry matter content or damages by pests or diseases were few and not systematic, whereas clear effects on nutrient balances and nitrogen leaching indicators were found. Root growth of all crops was studied in the C and O2 system, but only few effects of cropping system on root growth was observed. However, the addition of green manures to the systems almost doubled the average soil exploration by active root systems during the rotation from only 21% in C to 38% in O2 when measured to 2.4m depth. This relates well to the observed differences in subsoil inorganic N content (N-inorg. 1-2 m depth) across the whole rotation (74 and 61 kg N ha(-1) in C and O1 vs. only 22 and 21 kg N ha(-1) in O2 and O3), indicating a strongly reduced N leaching loss in the two systems based on fertility building crops (green manures and catch crops). In short, the main distinctions were not observed between organic and conventional systems (i.e. C vs. O1, O2 and O3). but between systems based mainly on nutrient import vs. systems based mainly on fertility building crops (C and O1 vs. O2 and O3). (C) 2011 Elsevier B.V. All rights reserved.
  • Authors:
    • Satkus, A.
    • Velykis, A.
  • Source: Žemdirbystė (Agriculture)
  • Volume: 99
  • Issue: 1
  • Year: 2012
  • Summary: Research was done at the Joniskelis Experimental Station of the Lithuanian Research Centre for Agriculture and Forestry on a clay loam Endocalcari-Endohypogleyic Cambisol (CMg-n-w-can). The objective of this study was to determine the effects of reduced (shallow ploughing and ploughless tillage) tillage as well as its combinations with supplementary agronomic practices, improving soil conditions - incorporation of lime sludge, cover crop (mixture of white mustard and oilseed radish) for green manure and mulch on the emergence, growth and development of field pea (Pisum sativum L.) crop. Data revealed that shallow ploughing caused the worst field pea emergence in 2008. Ploughless tillage in combination with lime sludge incorporation resulted in a significantly higher soil water content in seedbed layer (0-5 cm) directly after field pea sowing in 2009, better field pea germination within the prolonged droughty post-sowing periods (18 and 20 days respectively in 2008 and 2009) and higher grain yield in 2008 as compared to deep ploughing. Due to the ploughless tillage together with incorporation of the cover crop biomass for the green manure late in autumn, significantly higher soil water content was registered in the seedbed directly after sowing in 2010 and at 5-15 cm depth according to the average data of 2008-2010; however the emergence and growth of field pea under droughty conditions were worse, and yield decreased in 2009 and 2010. Application of ploughless tillage with no supplementary practices resulted in significantly higher soil water content in seedbed directly after field pea sowing in 2010; however, in field pea yield decreased in 2009. Cover crop winter mulch without tillage in autumn led to a significantly higher soil water content in the seedbed directly after sowing in 2010, while the soil water content after field pea emergence at 5-15 cm depth in 2008 and at 15-25 cm depth according to the average data of 2008-2010 was lower, seedbed structure was mostly worse, field pea growth and development were poor and crop yield was lower in all years of study as compared to deep ploughing. Rapid capillary water movement, characteristic of clay loam with predominant silty fractions, could lead to a higher drying of soil layers unloosened in the autumn. Field pea yield was influenced by the amount of rainfall during one month after sowing in a droughty year 2008 and by the soil structure in a seedbed in 2009.
  • Authors:
    • Pruessner, E. G.
    • Stewart, C. E.
    • Follett, R. F.
    • Kimble, J. M.
  • Source: Journal of Soil and Water Conservation
  • Volume: 67
  • Issue: 5
  • Year: 2012
  • Summary: Soils of the US Great Plains contain enormous stocks of soil organic carbon (SOC) and soil organic nitrogen (SON) that are vulnerable to predicted climate and land use change. Climate change scenarios predict a 2.2 degrees C to 3.6 degrees C (4 degrees F to 6.5 degrees F) increase and more variability in precipitation across most of the United States. This study quantifies management effects (native grassland, Conservation Reserve Program [CRP], and cropped) on SOC and SON stocks across the region and assessed soil variables (soil texture, cation exchange capacity and others) and climatic drivers (precipitation and temperature) to predict future changes in carbon (C) and nitrogen (N) stocks. Across all sites, cropped land had significantly lower C and N stocks in the 0 to 5 cm (0 to 2 in) and 0 to 10 cm (0 to 3.9 in) depths than native sites, while CRP sites were intermediate. Mean annual temperature (MAT), the ratio of mean annual precipitation to potential evapotranspiration (MAP:PET), soil bulk density (BD), and clay content were important covariates for SOC and SON stocks within land use. Soil C and N stocks under all three land uses were strongly negatively related to MAT and positively related to MAP:PET, suggesting that they are equally vulnerable to increased temperature and decreasing water availability Based on these empirical relationships, a 1 degrees C (1.8 degrees F) increase in MAT could cause a loss of 486 Tg SOC (536 million tn) and a loss of 180 kg SON ha(-1) (160 lb SON ac(-1)) from the top 10 cm (3.9 in) of soil over 30 years, but the decrease will be mediated by water availability (MAP:PET). Combined, increased temperature and conversion from CRP to cropland could decrease the existing SOC sink, but improved soil management and increased water availability may help offset these losses in the US Great Plains.
  • Authors:
    • Eigenberg, R. A.
    • Hubbard, R. K.
    • Powell, J. M.
    • Torbert, H. A.
    • Woodbury, B. L.
    • Albrecht, S. L.
    • Sistani, K. R.
    • Wienhold, B. J.
    • He, Z. Q.
    • Larkin, R. P.
    • Griffin, T. S.
    • Vandemark, G.
    • Honeycutt, C. W.
    • Fortuna, A. M.
    • Wright, R. J.
    • Alldredge, J. R.
    • Harsh, J. B.
  • Source: Journal of Environmental Quality
  • Volume: 41
  • Issue: 1
  • Year: 2012
  • Summary: Soil biotic and abiotic factors strongly influence nitrogen (N) availability and increases in nitrification rates associated with the application of manure. In this study, we examine the effects of edaphic properties and a dairy ( Bos taurus) slurry amendment on N availability, nitrification rates and nitrifier communities. Soils of variable texture and clay mineralogy were collected from six USDA-ARS research sites and incubated for 28 d with and without dairy slurry applied at a rate of ~300 kg N ha -1. Periodically, subsamples were removed for analyses of 2 M KCl extractable N and nitrification potential, as well as gene copy numbers of ammonia-oxidizing bacteria (AOB) and archaea (AOA). Spearman coefficients for nitrification potentials and AOB copy number were positively correlated with total soil C, total soil N, cation exchange capacity, and clay mineralogy in treatments with and without slurry application. Our data show that the quantity and type of clay minerals present in a soil affect nitrifier populations, nitrification rates, and the release of inorganic N. Nitrogen mineralization, nitrification potentials, and edaphic properties were positively correlated with AOB gene copy numbers. On average, AOA gene copy numbers were an order of magnitude lower than those of AOB across the six soils and did not increase with slurry application. Our research suggests that the two nitrifier communities overlap but have different optimum environmental conditions for growth and activity that are partly determined by the interaction of manure-derived ammonium with soil properties.
  • Authors:
    • Ziadi, N.
    • Gagnon, B.
  • Source: Canadian Journal of Soil Science
  • Volume: 92
  • Issue: 6
  • Year: 2012
  • Summary: Residues from paper and wood mills are a valuable source of nutrients for field crops, but little is known about the effectiveness of repeated applications over many years. A study was initiated at Yamachiche, QC, to assess the effect of continuous applications over 9 yr of combined papermill biosolids (PB), applied alone or with several liming by-products, on grain yield, plant nutrient accumulation, and soil fertility in a loamy soil cropped to grain corn, dry bean, and soybean. The PB treatments (0, 30, and 60 Mg wet ha -1) and liming by-products [calcitic lime (CL), lime mud (LM), wood ash (WA)], and two magnesium residuals, each at 3 Mg wet ha -1 along with (30 Mg PB ha -1) were surface applied annually at post-seeding. In the last 6 yr, the two treatments receiving magnesium residuals were replaced with 90 Mg wet PB ha -1 and mineral N fertilizer (MIN), respectively. Repeated annual applications of LM followed by CL increased soil pH the most (up to 1.4 unit). Crop yields were not significantly affected by treatments in the first 3 yr but subsequent applications of PB at 90 Mg ha -1 increased yields in grain corn (+1.9 Mg ha -1) and dry bean (+0.77 Mg ha -1) relative to the control, while PB with WA increased yield in soybean (+0.85 Mg ha -1). The PB at 30 Mg wet ha -1 with supplemental N (average of 45 kg N ha -1), or at 60 Mg wet ha -1 applied alone, achieved yields comparable with MIN treatment under corn. The PB applications increased soil organic matter and all major soil nutrients except K and Mg. The results of this study indicate that PB and alkaline residuals can be effectively applied to agricultural soils over many years although PB exceeding 60 Mg wet ha -1 yr -1 induce significant nitrate leaching.
  • Authors:
    • Koch, H. J.
    • Gajic, A.
  • Source: Journal of Environmental Quality
  • Volume: 41
  • Issue: 4
  • Year: 2012
  • Summary: Hydrothermal carbonization allows rapid conversion of biomass into a carbon-rich, lignite-like product (hydrochar). It is assumed to have beneficial effects on soil properties and plant growth, but detailed studies are lacking, especially in the field. The objective of our study was to investigate the effect of hydrochar incorporated into arable soils on soil mineral nitrogen (N min) content and sugar beet growth. In 2010-2011, a field and a pot trial were conducted. Hydrochars (field: 10 Mg ha -1; pot: equivalent to 30 Mg ha -1) processed from sugar beet pulp (HSP) and beer draff (HBD) were tested against an untreated control. As a second factor, mineral nitrogen (N) fertilizer level (field: 0, 50, 100, 150 kg N ha -1; pot: 0, 100, 200 mg N kg -1 soil) was varied. In both trials, hydrochars reduced initial sugar beet growth, especially when hydrochar with a high C/N ratio (38, HSP) was combined with a low N fertilizer level; high N supply partly compensated for the reduced seedling growth. Without N fertilization, no extractable N min was present at the end of the pot trial in the HSP treatment, whereas in HBD even more N min was extracted than in the control. This suggests remineralization of previously immobilized N when hydrochar with a low C/N ratio was applied (16, HBD). In the field, beet yield was equal at the high N fertilizer level in HSP and at all N levels in HBD treatment. Our results suggest that hydrochar can decrease plant-available N due to N immobilization. Other potential causes for the observed early growth reduction need to be studied more in detail.
  • Authors:
    • Mitchell, C. D.
    • Sochacki, S. J.
    • George, S. J.
    • Dean, C.
    • Tibbett, M.
    • Stilwell, A. T.
    • Okom, A. E. A.
    • Harper, R. J.
    • Mann, S. S.
    • Dods, K.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 163
  • Year: 2012
  • Summary: In the Western Australian wheatbelt, the restoration of native eucalypt forests for managing degraded agricultural landscapes is a critical part of managing dryland salinity and rebuilding biodiversity. Such reforestation will also sequester carbon. Whereas most investigative emphasis has been on carbon stored in biomass, the effects of reforestation on soil organic carbon (SOC) stores and fertility are not known. Two 26 year old reforestation experiments with four Eucalyptus species ( E. cladocalyx var nana, E. occidentalis, E. sargentii and E. wandoo) were compared with agricultural sites (Field). SOC stores (to 0.3 m depth) ranged between 33 and 55 Mg ha -1, with no statistically significant differences between tree species and adjacent farmland. Farming comprised crop and pasture rotations. In contrast, the reforested plots contained additional carbon in the tree biomass (23-60 Mg ha -1) and litter (19-34 Mg ha -1), with the greatest litter accumulation associated with E. sargentii. Litter represented between 29 and 56% of the biomass carbon and the protection or utilization of this litter in fire-prone, semi-arid farmland will be an important component of carbon management. Exch-Na and Exch-Mg accumulated under E. sargentii and E. occidentalis at one site. The results raise questions about the conclusions of SOC sequestration studies following reforestation based on limited sampling and reiterate the importance of considering litter in reforestation carbon accounts.
  • Authors:
    • Snapp, S. S.
    • Jaikumar, N. S.
    • Murphy, K.
    • Jones, S. S.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 6
  • Year: 2012
  • Summary: Perennial wheat ( Triticum aestivum L. * Thinopyrum spp.) and perennial rye ( Secale cereale L. * S. montanum) are novel hybrid species under development as alternatives to annual cereal crops. We conducted a 2-yr field study with a split plot design to evaluate agronomic performance, including yield, phenology, and biomass production, of perennial accessions of wheat and rye, along with annual analogs. This is one of the first studies to rigorously compare agronomic performance of 2-yr-old plants to 1-yr-old plants in perennial cereals. Perennial wheat produced 1.0 to 1.6 Mg ha -1 grain yield, 50% of annual wheat (2.7 Mg ha -1), while perennial rye produced 1.3 Mg ha -1, 73% of annual rye (1.8 Mg ha -1). Modest yields from perennials relative to annuals reflected lower harvest index, lower yield per tiller, and less kernel mass. One-year-old and 2-yr-old perennial plants had similar seed yields, yield components, and biomass production, indicating that plant age had little effect on these parameters and older plants maintained yield potential. In contrast, phenology did vary with plant age, and showed a shift toward earlier spring growth and later flowering dates in older perennial plants. This illustrates an expanded vegetative period for regrowing plants of these perennial cereals. There appears to be potential for producing an early season forage crop from these cereals, although biomass yields were not high at this site and regrowth was not always reliable. Overall, performance of perennial rye was consistent with a viable new cereal crop. On the other hand, perennial wheat requires further selection for allocation of biomass to grain and vigorous regrowth.
  • Authors:
    • Krumhardt, K. M.
    • Kaplan, J. O.
    • Zimmermann, N. E.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 3
  • Year: 2012
  • Summary: The long residence time of carbon in forests and soils means that both the current state and future behavior of the terrestrial biosphere are influenced by past variability in climate and anthropogenic land use. Over the last half-millennium, European terrestrial ecosystems were affected by the cool temperatures of the Little Ice Age, rising CO 2 concentrations, and human induced deforestation and land abandonment. To quantify the importance of these processes, we performed a series of simulations with the LPJ dynamic vegetation model driven by reconstructed climate, land use, and CO 2 concentrations. Although land use change was the major control on the carbon inventory of Europe over the last 500 years, the current state of the terrestrial biosphere is largely controlled by land use change during the past century. Between 1500 and 2000, climate variability led to temporary sequestration events of up to 3 Pg, whereas increasing atmospheric CO 2 concentrations during the 20th century led to an increase in carbon storage of up to 15 Pg. Anthropogenic land use caused between 25 Pg of carbon emissions and 5 Pg of uptake over the same time period, depending on the historical and spatial pattern of past land use and the timing of the reversal from deforestation to afforestation during the last two centuries. None of the currently existing anthropogenic land use change datasets adequately capture the timing of the forest transition in most European countries as recorded in historical observations. Despite considerable uncertainty, our scenarios indicate that with limited management, extant European forests have the potential to absorb between 5 and 12 Pg of carbon at the present day.
  • Authors:
    • Infante Amate, J.
    • Bernard, C.
    • Vanwalleghem, T.
    • Toloza, A.
    • Chhem-Kieth, S.
    • Mabit, L.
    • Gonzalez de Molina, M.
    • Gomez, J. A.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 159
  • Year: 2012
  • Summary: Soil degradation is a major agrienvironmental issue under Mediterranean climatic conditions. To assess soil erosion magnitude under orchard plantation, soils in an undisturbed area - located within an archaeological protected site in southern Spain - were analysed to establish its physicochemical status, the initial 137Cs fallout and the natural level of radioactivity taking into account the content of naturally occurring radionuclides (NOR). The vertical profiles of NOR mass activities confirmed its non-disturbance. 90% of the 137Cs content was concentrated in the top 20 cm and the physicochemical parameters confirmed as well the undisturbed status of the site. The base-line level of 137Cs was established at 1925250 Bq m -2 with a coefficient of variation of 23% and an allowable error of 11%. This 137Cs background was used to assess soil erosion magnitude in a close orchard field using the 137Cs method. The maximum erosion rates reached 19 t -1 ha -1 yr -1 and a sediment delivery ratio of 29% was evaluated, both values confirming an unsustainable soil loss magnitude due to the combination of water and tillage erosion processes since the 1950s. The radium equivalent activity and the absorbed dose rate results highlighted a difference between eroded and deposition sectors in the cultivated field confirming that these parameters could be used to some extend to assess pedologic processes.