• Authors:
    • Siriwardena, G. M.
    • Chamberlain, D. E.
  • Source: Environmental Reviews
  • Volume: 8
  • Issue: 2
  • Year: 2000
  • Summary: Declines in a number of farmland bird species in northern Europe have been linked to agricultural intensification. In this paper, we review the evidence for the effects of agricultural intensification on farmland bird populations using monitoring studies on a single well-studied species, the Eurasian Skylark (Alauda arvensis). Between 1970 and 1998, the Skylark population declined by 44% and this decline was greatest on farmland compared to upland or coastal habitats, yet during that time, reproductive performance per individual nesting attempt improved significantly. Skylarks consistently prefer relatively sparse (spring cereals) or structurally complex (fallow "set-aside"') crops, particularly late in the breeding season when crops that are too tall or dense are abandoned. Outside the breeding season, cereal stubble is the most preferred foraging habitat. Intensification has been characterized by decreases in preferred crops (spring cereals and cereal stubble) and an increase in unfavourable habitats (winter cereals, oilseed rape, and intensively managed or grazed grass). Reduction in the number of breeding attempts due to rapid sward development of winter cereals and the lack of suitable alternative habitats is likely to have been an important factor in the Skylark decline. The decline may also have been driven by decreases in survival outside the breeding season. Management regimes that include spring cereals, cereal stubble, and low-intensity grazing are likely to increase Skylark abundance and will benefit a number of other farmland birds. This review highlights the great value of large-scale monitoring schemes in understanding population declines. However, the factors affecting the post-fledging survival of Skylarks and the effects of crop diversity on Skylark abundance remain to be resolved.
  • Authors:
    • Fernandes, S. V.
    • Martin-Neto, L.
    • Amado, T. J. C.
    • Mielniczuk, J.
    • Bayer, C.
  • Source: Soil & Tillage Research
  • Volume: 54
  • Issue: 1-2
  • Year: 2000
  • Summary: Soil organic matter decline and associated degradation of soil and environmental conditions under conventional tillage in tropical and subtropical regions underline the need to develop sustainable soil management systems. This study aimed first to evaluate the long-term effect (9 years) of two soil-tillage systems (conventional tillage: CT, and no-tillage: NT) and two cropping systems (oat (Avena strigosa Schreb)/maize (Zea mays L.): O/M; and oat+common vetch (Vicia sativa L.)/ maize+cowpea (Vigna unguiculata (L.) Walp): O+V/M+C without N fertilization on total organic carbon (TOC) and total nitrogen (TN) concentrations in a sandy clay loam Acrisol in southern Brazil. The second objective was to assess soil potential for acting as an atmospheric CO2 sink. Under NT an increase of soil TOC and TN concentrations occurred, in both cropping systems, when compared with CT. However, this increase was restricted to soil surface layers and it was higher for O+V/M+C than for O/M, The O+V/M+C under NT, which probably results in the lowest soil organic matter losses (due to erosion and oxidation) and highest addition of crop residues, had 12 Mg ha(-1) more TOC and 0.9 Mg ha(-1) more TN in the 0-30.0 cm depth soil layer, compared with O/M under CT which exhibits highest soil organic matter losses and lowest crop residue additions to the soil. These increments represent TOC and TN accumulation rates of 1.33 and 0.10 Mg ha(-1) per year, respectively. Compared with CT and O/M, this TOC increase under NT and O+V/M+C means a net carbon dioxide removal of about 44 Mg ha(-1) from the atmosphere in 9 years. NT can therefore be considered, as it is in temperate climates, an important management strategy for increasing soil organic matter. In the tropicals and subtropicals, where climatic conditions cause intense biological activity, in order to maintain or increase soil organic matter, improve soil quality and contribute to mitigation of CO2 emissions, NT should be associated with cropping systems resulting in high annual crop residue additions to soil surface. (C) 2000 Elsevier Science B.V. All rights reserved.
  • Authors:
    • Lang, B.
  • Source: Report on farming in the eastern counties of England 1998/99.
  • Year: 2000
  • Summary: The report is divided into two sections. Part I analyses physical and financial data collected from 381 farms in the eastern counties of England (Bedfordshire, Cambridgeshire, Essex, Hertfordshire, South Lincolnshire, Norfolk and Suffolk) for the harvest year 1998. Performance is analysed by district, farm size group and type (mainly cereals, mixed cropping, dairy with arable, pigs and poultry, mixed farms and fen arable). A review of the farming environment in 1998/99 is also included. Part II looks ahead to future policy developments which may result from both internal and external forces. Internal forces include the England Rural Development plan whilst external pressures will arise from World Trade Organization discussions. Key findings are: (i) the lowest farm incomes (for ten years) were recorded on combinable crop and livestock farms; (ii) returns on pig farms declined further; (iii) low prices prevailed for commodity cereals, combinable break crops, milk and all meat; (iv) sterling strengthened against European currencies; (v) exceptional potato prices were available in 1998 restoring fortunes of Fen Arable and Mixed Cropping farms; and (vi) borrowing was inexpensive in a year when indebtedness by farm business increased.
  • Authors:
    • Nacci, S.
    • Ramos, M. C.
    • Pla, I.
  • Source: Soil Science
  • Volume: 165
  • Issue: 5
  • Year: 2000
  • Summary: In the vineyards of the Anoia-Alt Penedes region of NE Spain, erosion problems arising from a combination of soil and climate characteristics and their relief have been accelerated in the last few decades as a consequence of new cropping/planting patterns and soil management practices involving continuous tillage, which leaves the soil bare most of the time. In the rain-fed vineyards of the area, rainfall water conservation in situ has also become a problem that influences the production of high quality wine. The determination of the actual and potential erosion processes required for rational selection, design, and application of soil and water conservation practices requires identification and quantification of the hydrological properties and processes that induce runoff and soil erosion. Laboratory studies in 10 representative surface soils of the region, using simulated rainfall, proved that erosion losses were highly related to the surface sealing susceptibility of the soils, which reduced minimum rainfall water intake rates to 1 to 7 mm h(-1) or less after only 10 minutes of rainfall. This susceptibility was highly correlated with the high silt and low organic matter content of the soils. In most of the soils, surface protection by a cover was found to increase the minimum rainfall water intake rate 50 to 200 times. A simple laboratory test, based on the measurement of saturated hydraulic conductivity and the time to reach its minimum value, measured efficiently the sealing susceptibility of the studied soils and the relative effect of a protective cover. The minimum value of saturated hydraulic conductivity was highly correlated to runoff and soil erosion losses in soil boxes under simulated rainfall.
  • Authors:
    • Düring, R. A.
    • Tebrügge, F.
  • Source: Soil & Tillage Research
  • Volume: 53
  • Issue: 1
  • Year: 1999
  • Summary: This paper reviews research performed at the Justus-Liebig-University of Giessen, Germany into the impact of different tillage systems on soil properties and quality. The impact of intensive soil tillage treatments on several soil properties was described by means of selected data obtained through long-term interdisciplinary research. The experiments were based on comparative application (long-term, up to 18 years investigations) of the respective tillage options on different soils (e.g. Eutric Cambisol, Eutric Fluvisol) ranging in texture from sand to a silt loam. These soils are located at five field sites with different crop rotations in the central German state of Hesse. Tillage intensity of the systems was considered to decrease in the following sequence: Conventional plough tillage (CT), reduced tillage (RT), and no-tillage (NT). For elucidating the impact of tillage intensity, the tillage extremes CT and NT were compared. Physical conditions of soil as influenced by the application of RT were considered to be intermediate between CT and NT. In general, bulk density in the upper layer of NT soils was increased, resulting in a decrease in the amount of coarse pores, and a lower saturated hydraulic conductivity when compared with the CT and RT soils. Surface cover by crop residues and higher aggregate stability under NT protected soil fertility by avoiding surface sealing and erosion. Lateral losses of herbicides were also reduced under NT conditions, whereas the susceptibility for preferential vertical transport of herbicides needs further evaluation. Accumulation of organic matter and nutrients near the soil surface under NT and RT were favorable consequences of not inverting the soil and by maintaining a mulch layer on the surface. Those improvements were associated with enhanced biological activities in NT and RT topsoils. Increased earthworm activity in NT treatments was associated with a system of continuous macropores which improved water infiltration rates. Earthworms support decomposition and incorporation of straw. Soils which have not been tilled for many years were more resistant to vehicle passage; consequently, the compaction by traffic was lower. Penetration resistance curves indicate that a uniformly stable structure had developed over the years in NT soils. Overall, the results show that RT and NT were beneficial to the investigated soil properties. If crop rotation, machinery, and plant protection are well adapted for the introduction of conservation tillage, these systems may replace conventional ploughing systems in many cases in German agriculture. (C) 1999 Elsevier Science B.V. All rights reserved.
  • Authors:
    • Siriwardena, G. M.
    • Bradbury, R. B.
    • Wilson, J. D.
    • Krebs, J. R.
  • Source: Nature
  • Volume: 400
  • Year: 1999
  • Authors:
    • Collins, C.
    • Chalmers, A. G.
    • Froment, M. A.
    • Grylls, J. P.
  • Source: The Journal of Agricultural Science
  • Volume: 133
  • Year: 1999
  • Summary: The effect of a range of one-year set-aside treatments on soil mineral nitrogen (SMN), during the set-aside period and in a following wheat crop were studied in a phased experiment at five sites from 1987 to 1991. Ground cover options permitted under the UK government's 'set-aside' scheme, including natural regeneration, autumn sown Italian ryegrass (Lolium multiflorum), spring-sown legumes and cultivated fallow, were compared with a control treatment of continuous cereals managed with fertilizer inputs. In the first of three phases in this experiment, an uncultivated fallow (kept weed-free) and autumn-sown forage rape (Brassica napus) were included as extra treatments. There were large differences in total SMN (0.0-0.9 m) between sites, ranging from 16 to 205 kg N/ha, reflecting differences in soil type, which ranged from clays to sands, and previous cropping husbandry. Differences in SMN between set-aside treatments during the first winter of the set-aside year were small, but increased during the following summer. Amounts of SMN were greatest after cultivated fallow (46-178 kg N/ha) and least after ryegrass (26-111 kg N/ha). Natural regeneration and spring sown legumes were more variable in their effect on SMN. Compared to continuous cereals, there was a build up in SMN during bare fallow, but a reduction under ryegrass, prior to returning to wheat cropping in the autumn after set-aside. SMN results suggest there was an increased nitrate leaching risk for bare fallow and natural regeneration set-aside, compared to sown ryegrass covers, in the winter following ploughing out of set-aside. This risk could be minimized by earlier sowing of winter cereals following set-aside or sowing with winter oilseed rape rather than cereals to maximize crop nitrogen (N) uptake, during the autumn growth period. Averaged across five sites, residual SMN supply in the spring of first test year cereal crops for all set-aside treatments was similar to that for continuous cereals, suggesting over-winter losses by N leaching or immobilization. The low residual N fertility after rotational set-aside suggested that following crop N recommendations should be the same as for continuous cereals. Amounts of SMN were less each year in spring than in the preceding autumn in both the set-aside and first test cereal crops. The results suggested that a ryegrass cover appeared to be the most environmentally favourable option for rotational set-aside management, as it minimized the amount of readily leachable N both during and immediately after the set-aside period.
  • Authors:
    • Smith, J. U.
    • Glendining, M. J.
    • Powlson, D. S.
    • Smith, P.
  • Source: Global Change Biology
  • Volume: 4
  • Issue: 6
  • Year: 1998
  • Summary: In this paper we estimate the European potential for carbon mitigation of no-till farming using results from European tillage experiments. Our calculations suggest some potential in terms of (a) reduced agricultural fossil fuel emissions, and (b) increased soil carbon sequestration. We estimate that 100% conversion to no-till farming would be likely to sequester about 23 Tg C y-1 in the European Union or about 43 Tg C y-1 in the wider Europe (excluding the former Soviet Union). In addition, up to 3.2 Tg C y-1 could be saved in agricultural fossil fuel emissions. Compared to estimates of the potential for carbon sequestration of other carbon mitigation options, no-till agriculture shows nearly twice the potential of scenarios whereby soils are amended with organic materials. Our calculations suggest that 100% conversion to no-till agriculture in Europe could mitigate all fossil fuel-carbon emissions from agriculture in Europe. However, this is equivalent to only about 4.1% of total anthropogenic CO2-carbon produced annually in Europe (excluding the former Soviet Union) which in turn is equivalent to about 0.8% of global annual anthropogenic CO2-carbon emissions.
  • Authors:
    • Pfadenhauer, J.
    • Klemisch, M.
    • Wild, U.
  • Source: European Journal of Soil Science
  • Volume: 49
  • Issue: 2
  • Year: 1998
  • Summary: Trace gas fluxes of N2O and CH4 were measured weekly over 12 months on cultivated peaty soils in southern Germany using a closed chamber technique. The aim was to quantify the effects of management intensity and of soil and climatic factors on the seasonal variation and the total annual exchange rates of these gases between the soil and the atmosphere. The four experimental sites had been drained for many decades and used as meadows (fertilized and unfertilized) and arable land (fertilized and unfertilized), respectively. Total annual N2O-N losses amounted to 4.2, 15.6, 19.8 and 56.4 kg ha(-1) year(-1) for the fertilized meadow, the fertilized field, the unfertilized meadow and the unfertilized field, respectively. Emission of N2O occurred mainly in the winter when the groundwater level was high. At all sites maximum emission rates were induced by frost. The largest annual N2O emission by far occurred from the unfertilized field where the soil pH was low (4.0). At this site 71% of the seasonal variation of N2O emission rates could be explained by changes in the groundwater level and soil nitrate content. A significant relationship between N2O emission rates and these factors was also obtained for the other sites, which had a soil pH between 5.1 and 5.8, though the relation was weak (R-2 = 15-27%). All sites were net sinks for atmospheric methane. Up to 78% of the seasonal variation in CH4 flux rates could be explained by changes in the groundwater level. The total annual CH4-C uptake was significantly affected by agricultural land use with greater CH4 consumption occurring on the meadows (1043 and 833 g ha(-1)) and less on the cultivated fields (209 and 213 g ha(-1)).
  • Authors:
    • Willison, T. W.
    • Poulton, P. R.
    • Murphy, D. V.
    • Howe, M.
    • Hargreaves, P.
    • Bradbury, N. J.
    • Bailey, N. J.
    • Goulding, K. W. T.
  • Source: New Phytologist
  • Volume: 139
  • Issue: 1
  • Year: 1998
  • Summary: Human activity has greatly perturbed the nitrogen cycle through increased fixation by legumes, by energy and fertilizer production, and by the mobilization of N from long-term storage pools. This extra reactive N is readily transported through the environment, and there is increasing evidence that it is changing ecosystems through eutrophication and acidification. Rothamsted Experimental Station, UK has been involved in research on N cycling in ecosystems since its inception in 1843. Measurements of precipitation composition at Rothamsted, made since 1853, show an increase of nitrate and ammonium N in precipitation from 1 and 3 kg N ha(-1) yr(-1) respectively, in 1855 to a maximum of 8 and 10 kg N ha(-1) yr(-1) in 1980, decreasing to 4 and 5 kg N ha(-1) y(-1) today. Nitrogen inputs via dry deposition do, however, remain high. Recent measurements with diffusion tubes and filter packs show large concentrations of nitrogen dioxide of c. 20 mu g m(-3) in winter and c. 10 mu g m(-3) in summer; the difference is linked to the use of central heating, and with variations in wind direction and pollutant source. Concentrations of nitric acid and particulate N exhibit maxima of 1.5 and 2 mu g m(-3) in summer and winter, respectively. Concentrations of ammonia are small, barely rising above 1 mu g m(-3). Taking deposition velocities from the literature gives a total deposition of all measured N species to winter cereals of 43.3 kg N ha(-1) yr(-1), 84 % as oxidized species, 79 % dry deposited. The fate of this N deposited to the very long-term Broadbalk Continuous Wheat Experiment at Rothamsted has been simulated using the SUNDIAL N-cycling model: at equilibrium, after 154 yr of the experiment and with N deposition increasing from c. 10 kg ha(-1) yr(-1) in 1843 to 45 kg ha(-1) yr(-1) today, c. 5 % is leached, 12% is denitrified, 30% immobilized in the soil organic matter and 53 % taken off in the crop. The 'efficiency of use' of the deposited N decreases, and losses and immobilization increase as the amount of fertilizer N increases. The deposited N itself, and the acidification that is associated with it (from the nitric acid, ammonia and ammonium), has reduced the number of plant species on the 140-yr-old Park Grass hay meadow. It has also reduced methane oxidation rates in soil by c. 15 % under arable land and 30 % under woodland, and has caused N saturation of local woodland ecosystems: nitrous oxide emission rates of up to 1.4 kg ha(-1) yr(-1) are equivalent to those from arable land receiving > 200 kg N ha(-1) yr(-1), and in proportion to the excess N deposited; measurements of N cycling processes and pools using N-15 pool dilution techniques show a large nitrate pool and enhanced rates of nitrification relative to immobilization. Ratios of gross nitrification:gross immobilization might prove to be good indices of N saturation.