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4. Conclusion This work highlights the large variations in farm N surpluses, both between the European landscapes studied, and within these landscapes. Moreover, the large potentials for reductions in the N-losses is discussed, and demonstrated via the Danish case study.
References Dalgaard, T, Hutchings, N, Dragosits, U, Olesen, JE, Kjeldsen, C, Drouet, JL and Cellier, P. 2011a. Effects of farm heterogeneity and methods for upscaling on modelled nitrogen losses in agricultural landscapes. Environmental Pollution 159 (2011) 3183-3192.
Dalgaard, T., Olesen, J.E., Petersen, S.O., Petersen, B.M., Jørgensen, U., Kristensen, T., Hutchings, N.J., Gyldenkærne S. and Hermansen, J.E. 2011b. Developments in greenhouse gas emissions and net energy use in Danish agriculture – How to achieve substantial CO2 reductions? Environmental Pollution 159 (2011) 3193-3203.
Hansen, B., Thorling, L., Dalgaard, T. and Erlandsen, M. 2011. Trend reversal of nitrate in Danish groundwater – a reflection of agricultural practices and nitrogen surpluses since 1950. Environ Sci and Tech. 2011, 45 (1) 228–234.
Kronvang, B., Andersen, H.E., Børgesen, C.D., Dalgaard, T., Larsen, S.E., Bøgestrand, J. and Blicher-Mathiasen, G.
2008. Effects of policy measures implemented in Denmark on nitrogen pollution of the aquatic environment.
Environmental Science and Policy. Volume 11, Issue 2, Pages 144-152.
Food-based digestate quality and fertiliser value Rollett, A.J.a,. Taylor, M.J.a, Tompkins, D.b and Chambers, B.J.a a ADAS Gleadthorpe, Meden Vale, Mansfield, Nottinghamshire, NG20 9PD, UK b WRAP, The Old Academy, 21 Horse Fair, Banbury, Oxfordshire, OX16 0AH, UK
1. Background & Objectives Anaerobic digestion (AD) involves the breakdown of biodegradable materials in the absence of oxygen releasing biogas (a mixture of methane and carbon dioxide) that can be used to provide heat and power, and digestate: a nitrogen-rich fertiliser. AD can help to meet many important environmental goals including the diversion of biodegradable materials from landfill, generation of renewable energy and reduction in climate change gas emissions. However, the agronomic benefits of digestate are less well understood. This project quantified the ‘as produced’ quality of food-based (source-segregated) digestate, providing a robust evidence base to build confidence in its use with farmers and growers.
2. Materials & Methods Triplicate digestate samples were taken from two food-based AD facilities on two occasions (12 samples in total), following standard methodologies (e.g. Defra/EA, 2009) to obtain representative samples. Both AD facilities were working towards PAS 110 (BSI, 2010), which is an industry specification against which producers can check that digestate is of consistent quality and fit for purpose. Each sample was analysed for a range of nutrients, microbial pathogens, biochemical oxygen demand, physical contaminants, heavy metals and organic compound contaminants.
3. Results & Discussion
3.1. Total and readily available nitrogen The food-based digestates were shown to be a valuable source of nitrogen (Table 1); the mean total N content was 7.4 kg N m3, compared with ‘typical’ values for pig and cattle slurry of 3.6 kg N m3 and 2.6 kg N m3, respectively (Defra, 2010). The readily available N content (ammonium + nitrateN) of the food-based digestates was equivalent to c. 80 % of the total N content, compared with c.
70 % and c. 45 % for pig and cattle slurry, respectively. The digestates also contained agronomically useful amounts of phosphate (P2O5), potash (K2O), and sulphur (SO3) (Table 1).
Nitrogen Workshop 2012
3.2. Microbial pathogens The food-based digestates were PAS 110 compliant for E. coli (≤1000 colony forming units- CFU/g fresh weight-fw) and Salmonella spp. (absent in 25 g of fresh material). By way of comparison, Salmonella has been measured in c. 5 % of livestock slurries (Hutchison et al., 2002) and typical E.
coli numbers in livestock slurries are c. 7 log10 CFU/g.
3.3. Biochemical oxygen demand Biochemical oxygen demand (BOD) is a measure of the oxygen used by 30000 microorganisms to decompose organic materials. The mean BOD of the food
3.4. Other parameters Mean heavy metal concentrations in the food-based digestates were within the limits set in PAS 110, with the exception of cadmium in one digestate sample. All of the digestate samples were compliant with PAS 110 limits for physical contaminants (i.e. glass, plastics, etc.). Organic compound contaminants were present only at very low levels or below the limits of analytical detection.
4. Conclusions The analyses showed that food-based digestates contain valuable quantities of major plant nutrients.
In particular, digestate was shown to be a valuable source of readily available N. Careful recycling to land will allow the nutrient value of food-based digestate to be realised, benefitting crop yields and soil fertility and reducing the ‘carbon footprint’ of farming through savings in manufactured fertiliser use.
References BSI, 2010. Publicly Available Specification No 110. Specification for Whole Digestate, Separated Liquor and Separated Fibre Derived from the Anaerobic Digestion of Source-Segregated Biodegradable Materials. BSI, London.
Defra/EA, 2009. Guidance for Farmers in Nitrate Vulnerable Zones. PB 12736.
Defra, 2010. Fertiliser Manual (RB209) 8th Edition. The Stationery Office. PB13381 Hutchison, M.L., Ashmore, A.K., Crookes, K.M., Wilson, D.W., Groves, S.J., Chambers, B.J., Keevil, C.W. and Moore, A. 2002. Enumeration of pathogens in livestock wastes and factors affecting their survival. In: Proceedings of the joint CIWEM and Aqua Enviro Technology Transfer 7th European Biosolids and Organic Residuals Conference MAFF (1998). A Code of Good Agricultural Practice for the Protection of Water. Ministry of Agriculture Fisheries and Food. Publications, London.
Nitrogen Workshop 2012
Impact of the application of nitrogen from livestock manure on agricultural parcels on water quality: derogation in Flanders Vandervelpen, D.a, Maes, S.a, Tits, M.a, Elsen, A.a, Bries J.a, Vandendriessche, H.a, Van Overtveld, K.b, Peeters, L.b, Batelaan, O.b, Van Orshoven, J.b, Vanderborght, J.b, Diels, J.b a Soil Service of Belgium, Heverlee, Belgium b Department of Earth and Environmental Science, K.U. Leuven, Belgium
1. Background & Objectives In the commission decision of 21 December 2007, the Commission of the European Communities approved the Belgian request, with regard to the region of Flanders, to allow a higher application of livestock manure than provided in Nitrogen Directive 91/676/EEC. In this derogation decision a number of specific conditions were imposed on individual farms applying derogation as well on the competent authorities with regard to monitoring, control and reporting. Since nitrogen fertilizers will become more expensive in the future, it is of great importance to verify the possibility of substitution with livestock manure without impact on soil and water quality. The objective of this research is to assess the impact of derogation on nitrogen losses from the soil and on water quality through a monitoring network of at least 150 farms (target of 180 farms and 225 parcels) during 2007-2010.
2. Materials & Methods The existing monitoring network for phreatic groundwater was chosen as the basis for the set-up of the derogation monitoring network. This groundwater network consists of 2,107 multilevel monitoring wells with short well screens at 3 depths. The wells are equipped with one or more filter elements of 50 cm in length. Preferably, the first two wells were installed in the oxidized zone of the aquifer, where the third well was installed in the deeper reduced zone. For every well the infiltration area and the travel time for water from the root zone to the uppermost well screen was calculated. Only monitoring wells where the infiltration area was completely located in a single agricultural parcel and had a travel time less than 3 years were selected for the derogation monitoring network. In this way the measured water quality in a monitoring well could be linked to the agricultural parcel. Other selection criteria were willingness of farmer to participate, soil type, derogation/non derogation and cultivated crop. One hundred and twenty one parcels linked to monitoring wells were selected, less than the required 225 parcels. Therefore additional parcels were selected from farmers who volunteered to participate in the network and extra monitoring wells were placed to measure the water quality on their parcels. After the selection of parcels several types of measurements were carried out. Each hydrological year a soil sample was taken before and after winter from 0-90 cm in three layers to measure the amount of nitrate in the soil.
This gives information on the nitrate residue after harvest and the nitrate leaching out towards the surface and groundwater. To investigate the quality of the surface and groundwater, water samples from the phreatic monitoring wells, the extra monitoring wells, drains, ditches and canals were taken. In order to measure the water quality on parcels with a water level deeper than 1.5 m, a soil sample was taken from 90-120 cm and from 120-150 cm. Besides a general comparison of all derogation and non-derogation parcels, detailed comparisons were carried out for the most common combinations of cultivated crop (grass and maize) and soil type in Flanders (sand and sandy loam).
ANOVA tests (P ≤ 0.05) were carried out to verify statistical differences of measured nutrients between derogation and non-derogation parcels.
4. Conclusion Based on the extensive information of the monitoring network it is possible to conclude that application under specific derogation conditions of more nitrogen originating from livestock manure than described in Nitrogen Directive 91/676/EEC has no significant negative impact on water quality in Flanders, regarding nitrate concentration.
Nitrogen Workshop 2012
Impact of timing of nitrogen fertilization at tillering stage on rice plant growth in intermittent water management.
Martínez-Eixarch, M.a,b, Català-Forner, M.M.a, Pla-Mayor, E.a, Tomàs-Navarro, N.a, Zhu D.c a IRTA (Institute for Food and Agricultural Research and Technology. Ctra. Balada, km 1. 43870. Amposta. Spain b Present address: Department of Agriculture, University of Reading, Earley Gate, Reading RG6 6AR, UK c CNRRI (China National Rice Research Institute). 359 Tiyuchang Road, Hanzghou 310006, Zhejiang, China
1. Background & Objectives Tillering is a key process within the rice plant growth cycle as it plays an important role in determining the panicle number (Gendua et al., 2009). Nitrogen (N) fertilization is an important factor in rice tillering because it promotes the emergence of the culms and enhances their productivity. Nitrogen efficiency could be improved by a more precise application of the fertiliser.
In the Mediterranean climate, water scarcity is predicted under a scenario of climatic change (Climate Change 2001: Impacts, Adaptation and Vulnerability - IPCC, 2001). In rice, the intermittent water management system has been presented as a promising water saving irrigation system. The aim of this study was to investigate whether early N fertilisation at tillering stage would increase the yield in rice plants by promoting tillering in lower nodes. Also, the effect of a water-saving management and its interaction with the N fertilisation was considered.
2. Materials & Methods In 2008, a field experiment was conducted in Ebro Delta area (Southern Catalonia, Spain) under direct sown system cultivation. The N treatments focused on the timing of application during the tillering stage: either early tillering fertilization at the 3.5-leaf stage (N4L) or late tillering fertilization at the 8.5-leaf stage (N8L). The same dose of N (120 kg ha-1) was used in both treatments. In addition, two water management systems were compared: a standard water management (SWM) system with continuous flooding at 7 cm deep, which is usually practiced in the area, and an alternate wetting and drying (AWD) system with layers of 3 cm deep. The experiment was analyzed as a randomized plot design with 3 replications. Cultivar used was Gleva, which is widely grown in Ebro Delta area. Tiller emergence and survival of primary nodes (emerging from buds on the main stem) were monitored in 10 plants per treatment with three replicates. At harvest, grains in each tiller were oven-dried at 80ºC for 3days and then weighed.
Plant and tiller yield were assessed by the dry weight of the grains on a panicle basis. The plant yield was the sum of tiller yieldAnalysis of variance was made using the MIXED and ANOVA procedures and mean separation tests were performed using the adjusted Tukey’s least significant difference test (LSD). The statistical program used was SAS version 9.2.
3. Results & Discussion The early N fertilisation at tillering stage promoted the emergence of tillers in plants (54.7% and 49.7% in N4L and N8L, respectively, P=0.06), especially in lower positions. The average dry grain yield in the primary panicles was significantly higher in N4L (1.84±0.42 g) than in N8L (1.53±0.50 g) (P=0.0005). As a result, the yield of plants under N4L was higher (5.8±1.4 g) than under later N fertilisation (4.5±1.4 g) with a probability near the 5% significance level (P=0.08). The interaction between N fertilisation and water management was significant for tiller emergence (P=0.022) and tiller survival (P=0.03).
Nitrogen Workshop 2012
Figure 1. Response of plant yield in the different nitrogen treatments (A) and combinations of nitrogen and water treatments (B).
A. N fertilization at the start of tillering (N4L) promoted higher yields than fertilization at mid or late tillering (N8L). B. Plants under the treatment AWD-N8L yielded markedly less due to the poorer tillering and the subsequent lower panicle number. [SWM, standard water management (7-cm water layer); AWD, alternating wetting and drying; N4L, N fertilization at plant stage of 3.5 leaves; N8L, N fertilization at plant stage of 8.5 leaves].