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Abstract  Reduced tillage (RT) agriculture is an effective measure to reduce soil loss from soils susceptible to erosion in the short-term and is claimed to increase the soil organic carbon (SOC) stock. The change in distribution and total SOC stock in the 0–60 cm layer, the stratification of microbial biomass carbon (MB-C) content in the 0–40 cm layer and the carbon (C) mineralization in the upper 0–5 cm layer in silt loam soils in Western Europe with different periods of RT agriculture were evaluated. Ten fields at seven locations, representing the important RT types and maintained for a different number of years, and eight fields under conventional tillage (CT) agriculture with similar soil type and crop rotation were selected. RT agriculture resulted in a higher stratification of SOC in the soil profile than CT agriculture. However, the total SOC stock in the 0–60 cm layer was not changed, even after 20 of years RT agriculture. The MB-C was significantly higher in the 0–10 cm layer under RT agriculture, even after only 5 years, compared to CT agriculture. The higher SOC and MB-C content in the upper 0–5 cm layer of RT fields resulted in a higher C mineralization rate in undisturbed soil in the laboratory. Simulating ploughing by disturbing the soil resulted in inconsistent changes (both lower and higher) of C mineralization rates. A crop rotation with root crops, with heavy soil disturbance every 2 or 3 years at harvest, possibly limited the anticipated positive effect of RT agriculture in our research. [ABSTRACT FROM AUTHOR]

Abstract  The effect of reduced tillage (RT) on nitrous oxide (N2O) emissions of soils from fields with root crops under a temperate climate was studied. Three silt loam fields under RT agriculture were compared with their respective conventional tillage (CT) field with comparable crop rotation and manure application. Undisturbed soil samples taken in September 2005 and February 2006 were incubated under laboratory conditions for 10 days. The N2O emission of soils taken in September 2005 varied from 50 to 1,095 µg N kg−1 dry soil. The N2O emissions of soils from the RT fields taken in September 2005 were statistically (P 2O emissions from their respective CT soil. The N2O emission of soils taken in February 2006 varied from 0 to 233 µg N kg−1 dry soil. The N2O emissions of soils from the RT fields taken in February 2006 tended to be higher than the N2O emissions from their respective CT soil. A positive and significant Pearson correlation of the N2O–N emissions with nitrate nitrogen (NO3 −–N) content in the soil was found (P 3 −–N content of the soil and reduced N2O emissions from RT soils. [ABSTRACT FROM AUTHOR]

Abstract  Several recent reports on cropland soil organic carbon (SOC) stock changes throughout Europe indicate a general continuing loss of SOC from these soils. As most arable soils in Europe are not in an equilibrium situation because of past changes in land-use and management practices, shifts in both have been suggested to drive this decline of SOC stocks. A lack of data has prevented the unambiguous verification of the contribution of these factors to SOC loss. First, this study focused on recent evolutions in management options for SOC sequestration in Flanders and showed that despite such practices have increased since 1990, their current contribution is still limited. Strikingly, their expansion is at odds with the reported general losses of SOC (−0.48 t OC ha−1 year−1 on average). We used very detailed datasets of livestock numbers, N-application rates and cropping surfaces to calculate regional shifts in input of effective OC from animal manure application, cereal straw incorporation and crop residue incorporation which amounted to −0.094, −0.045 and −0.017 t OC ha−1 year−1, respectively. Shifts in management were identified to have potentially brought about but a third of the recent loss of SOC in the study area, although for central West-Flanders and the Eastern border of Flanders larger impacts of management were observed. This study suggests other influences such as land-use change and climate change to be involved as well. We estimated that another 10%–45% of the loss of SOC could potentially be attributed to land-use changes from grassland to cropland during the 1970–1990 period and about 10% to the observed temperature increase. While being a regional-scaled case study, these findings may be relevant to other European regions in particular (Denmark, The Netherlands, North-West Germany, Brittany and the North-West of France, the Po-valley in Italy and parts of England), with similar climate and intensity of agriculture, and where comparable trends in farming management may well have taken place. [ABSTRACT FROM AUTHOR]

Abstract  We have investigated the effect of two nitrification inhibitors, 3,4-dimethylpyrazole phosphate (DMPP) and dicyandiamide (DCD), on the accumulation of $${\text{NH}}^{{\text{ + }}}_{{\text{4}}} {\text{ - N}}$$ and $${\text{NO}}^{ - }_{3} - {\text{N}}$$ after incorporation of cauliflower residues in incubation experiments. Cauliflower leaves were incubated with soil and DCD or DMPP at two application rates [8.93 and 17.9 mg active component (ac) kg−1 for DCD; 0.89 and 1.79 mg ac kg−1 for DMPP]. Both doses of DCD and DMPP increased $${\text{NH}}^{ + }_{4} - {\text{N}}$$ on average by 18.9 and 26.0 mg N kg−1 for DCD1 (during 30 days) and DCD2 (during 45 days), respectively, and on average by 14.4 mg N kg−1 for DMPP1 and DMPP2 during a period of at least 95 days. In DCD-treated soils, $${\text{NO}}^{{\text{ - }}}_{{\text{3}}} {\text{ - N}}$$ data followed an S-shaped curve, indicating that nitrification restarted during the experiment: inhibition was on average 24% during 35 days for DCD1 and on average 45% during 49 days for DCD2. Thereafter, $${\text{NO}}^{ - }_{3} - {\text{N}}$$ amount in DCD-treated soils exceeded that of the cauliflower-only treatment by 31% for DCD1 and 78% for DCD2, probably due to a nitrogen release from DCD itself and a priming effect induced by DCD. In DMPP-treated soils, $${\text{NO}}^{ - }_{3} - {\text{N}}$$ data followed a linear pattern since nitrification was inhibited during the complete incubation (95 days): inhibition was on average 56 and 64% for DMPP1 and DMPP2, respectively. DMPP did not affect the N mineralization of the crop residues. Under favourable conditions, DCD is able to inhibit the nitrification from crop residues for 50 days and DMPP for at least 95 days. Hence, especially DMPP shows a potential to reduce $${\text{NO}}^{ - }_{3} $$ leaching after incorporation of crop residues. [ABSTRACT FROM AUTHOR]

Abstract Manipulating the N release from high-N crop residues by simultaneous mixing of these residues with organic biological waste (OBW) materials seems to be a possible method to reduce NO3− leaching. The aim of this study was to examine whether the incorporation of OBW materials together with a high-N crop residue (celery) had also an effect on N2O emission from horticultural soil under short-term and optimised laboratory conditions. A sandy loam soil and celery residues were mixed with different OBW materials and brought into PVC tubes at 80% water-filled pore space and 15°C. Every 2.5 h, a gas sample was taken and analysed by gas chromatography for its N2O concentration. The soil amended with only celery residues had a cumulative N2O emission of 9.6 mg N kg−1 soil in 50 h. When the celery residues were mixed with an OBW material, the N2O emission was each time lower than the emission from the celery-only treatment (between 3.8 and 5.9 mg N kg−1 soil during maximum 77 h), except with paper sludge (17.2 mg N kg−1 soil in 100 h). The higher N2O emission from the paper sludge treatment was probably due to its unusually low C:N ratio. Straw, green waste compost 1 (GWC1) and 2 (GWC2), saw dust, and tannic acid reduced the N2O emission of the celery treatment by 40 to 60%. Although the N2O reduction potential can be expected to be lower and with differing dynamics under field conditions, this study indicates that apart from reducing NO3− leaching, OBW application may at the same time reduce N2O emissions after incorporation of high-N crop residues. [ABSTRACT FROM AUTHOR]

The denitrification potential of the soil horizons between 0- and 90-cm depth of 20 agricultural fields, representative of the most frequent combinations of agricultural crops and soil textures in Flanders (Belgium), and the factors affecting the denitrification potential were studied in the laboratory under controlled conditions. The denitrification potential in the presence of an added soluble C and N source was measured at 15°C after saturation of air-dried soil samples with water. The denitrification potential of the lower horizons was generally negligible compared to the upper horizons. The lower denitrification potential of the deeper horizons could partially be explained by their limited C availability. The denitrification potential of the upper horizons strongly depended on texture. Based on this parameter the soils could be divided into three groups: soils with a high clay content (>30% clay) were characterised by a high denitrification potential (>8.33 µg N g -1 dry soil day -1); soils with medium texture had a medium denitrification potential, between 0.41 and 7.25 µg N g -1 dry soil day -1; and soils with a high sand content (>80% sand) had a low denitrification potential (<2.58 µg N g -1 dry soil day -1). In most cases, extending the saturation period during pre-incubation increased the denitrification potential. Comparison of the denitrification potential of the upper horizons with and without addition of a soluble C source showed that the denitrification potential of the upper horizons of these soils was limited by their percentage of endogenous C. The measured denitrification potentials indicate that denitrification losses in soils high in clay content can be important when NO 3 - concentrations are high. [ABSTRACT FROM AUTHOR]

In Western Europe, agriculture is one of the major contributors to the pollution of ground- and surface waters. Environmental concern has created the need for protection of these waters against eutrophication, caused by nutrient losses from e.g. agricultural sources. Leaching models may be used to predict nitrate-N losses to the environment and a plethora of such leaching models already exist. Four nitrate leaching models (Burns model, SLIM, SACFARM and ANIMO), with varying degree of complexity and parameter requirements, were used to simulate leaching in a bare fallow soil on a number of fields in the Wijlegem catchment in Flanders, Belgium. The models' performance was evaluated both statistically and graphically. Although all models predicted nitrate content in the soil profile within acceptable limits, the slightly adjusted Burns model appeared to simulate both the nitrate nitrogen and the water content best for the calibration field. Similar results were obtained for the evaluation field experiments: the Burns–α model simulated the moisture and nitrate content fairly well, while SLIM performed well in simulating the nitrate content. In conditions with limited data availability, simple (management) models, needing only a limited number of parameters to be measured or calibrated, may yield better simulation results than complex mechanistic models. [ABSTRACT FROM AUTHOR]

We have studied the short term C mineralization of six wastes from important food industries, one sludge from a biogas plant and three composts. All the wastes were characterized chemically and fractionated according to the Van Soest method. The fresh wastes were incubated under controlled environment conditions to determine the C mineralization rate. Based on first order mineralization kinetics, we calculated the hypothetical amount of stable C in the wastes as the amount of C that would not be mineralized within one year under field conditions. The percentage of stable organic C in the organic matter was in general much larger in the composts than in the other wastes, but when expressed on dry matter, the non-composted wastes had comparable or larger amounts of stable organic C than the composts and have a considerable potential for supplying organic matter to soils, and hence for C sequestration. The amount of stable organic C could best be predicted by the total N content of the wastes (Ra2 = 0.855), whereas the results of the fractionation had very little predictive power, probably due to problems related to the high ash content of some of the wastes. An index that combined stable organic C and N and P content in the wastes was calculated to assess possible limitations for applying these wastes in agriculture. Under current nutrient legislation in Western Europe, a number of these wastes will only be usable in small amounts, but these and other food industry wastes could still prove to be valuable soil amendments in nutrient poor situations, for increasing soil organic C content and supplying nutrients. [ABSTRACT FROM AUTHOR]