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At DAT 10 of the summer lettuce cycle C60 showed the highest NAvN together with MF (109 kg N ha-1 on average), while values were 63% lower with C10 and C30. NAvN significantly increased with the intermediate compost dose (+115%), while values did not change in C10. It was found a tendency to the decrease with MF (-79%) and a slight increase with C60 (+47%). NAR was not different with C30 and C60 (12% over the two cycles) while values with C10 and MF were higher (33%). Our results demonstrated that compost fertilization made at the beginning of the summer season at the 160 and 319 kg N ha-1 rate was able to sustain N lettuce nutrition in two consecutive cropping cycles, giving yields not different from mineral fertilization. Those results are consistent with Erhart et al. (2007) showing that compost acts as a slow release fertilizer, whose low mineralization rate makes N available to plants also several months after the application to the soil.
Low N uptake at the beginning of the summer cycle was probably due to the lack of N caused by the activation of soil microbiota after the fertilization. This happened only with the highest compost doses but no problems in plant nutrition occurred since N availability increased in the successive days of the summer cycle. NAvN did not increase in C10 plots probably because labile N input was too low to balance the slow N mineralization. NAR values were the same with C30 and C60 demonstrating that the 30 Mg ha-1 dose can maximize N recovery and lettuce yields.
4. Conclusion In our high fertile soil MSW compost could be a useful tool to manage N fertility in horticulture, reducing N inputs with mineral fertilizers. Nevertheless fertilization with fully stabilized compost could seriously limit crop growth in fine textured or low SOM soils where mineral N immobilization prevails on nitrification. Furthermore, compost doses need to be carefully managed in order to guaranty an adequate feeding of crops and limit hazardous N surplus. A more efficient N use could also be achieved delaying transplant date of summer season, as in well watered soils N availability from compost tends to a significant increase with the increase of soil temperature.
References Diacono M. and Montemurro F. 2010. Long-term effects of organic amendments on soil fertility. A review. Agronomy for Sustainable Development 30, 401-422.
Erhart E., Feichtinger F. and Hartl W. 2007. Nitrogen leaching losses under crops fertilized with biowaste compost compared with mineral fertilization. Journal of Plant Nutrition and Soil Science 170, 608-614.
Fagnano M., Adamo P., Zampella M. and Fiorentino N. 2011. Environmental and agronomic impact of fertilization with composted organic fraction from municipal solid waste. Agriculture Ecosystems & Environment 141, 100-107.
Montemurro, F., Maiorana, M., Ferri, D. and Convertini, G. 2006. Nitrogen indicators, uptake and utilization efficiency in a maize and barley rotation cropped at different levels and sources of N fertilization. Field Crops Research 99, 114
Nitrogen Workshop 2012
Assessment of the potential N mineralization/immobilization of pig slurry fractions obtained using different techniques Fangueiro, D., Lopes, C., Olsen, L., Vasconcelos E.
UIQA, Instituto Superior de Agronomia – Technical University of Lisbon, 1349-017 Lisbon, Portugal
An anaerobic incubation method (Fangueiro et al., 2008) was used to assess the potential N mineralization/immobilization. An amount of a specific slurry fraction corresponding to 0.03 g of N was added to 10 g of field moist soil in a 60 ml syringe and the amount of water was adjusted to have a total amount of 25 ml. 8 replicates of each slurry fraction and non-separated whole slurry
were performed to allow one half to be incubated for 7 days at 40º C, whilst the other half were extracted immediately with 1 M KCl. Potential mineralization/immobilization (PNM) was calculated as the difference between post- and pre-incubation NH4+-N contents.
3. Results & Discussion The main characteristics of the liquid and solid fractions obtained here vary notably according to the separation techniques used, namely in terms of total N and organic C (Table 1). All separation techniques except Sed and Sed+PAM generated solid fractions with higher organic C and total N concentrations than the WS or respective LF.
Potential nitrogen mineralization was observed with the WS and all the SFs with values of PNM close to 5% of the organic N applied (7.5% in Cent-S) (Figure 1). The LF obtained showed higher variability in terms of PNM with 2 leading to N mineralization, 2 to N immobilization and 2 did not exhibit any variation. No correlation was found between the PNM value of the different fractions studied and their C:N ratio albeit this parameter is usually used to predict the mineralization/immobilization of the organic residues. Hence, it is to believe that other parameters influenced by the separation techniques may interfere in the nitrogen mineralization/immobilization process.
Cent-L cent-S Sed Sed Sed-L Sed-S Siev-L Siev-S Sed+Filt-L Sed+Filt- PAM-L PAM-S WS +PAM-L +PAM-S S Slurry Fraction or whole slurry Figure 1. Potential of nitrogen mineralization/immobilization of SF and LF obtained by separation of pig slurry using different techniques (N=4)
4. Conclusions Our results show that most separation techniques allow an efficient removal of solids but the composition of the resulting fractions depends on the separation technique. The choice of the separation technique has to consider the final use of the resulting fraction. Nevertheless, technologies to perform centrifugation and sieving are expensive and energy consuming whereas the separation by sediment settling imply limited investments. According to previous results from Fangueiro et al. (2008), the assessment of the particle size distribution of the fraction obtained with different separation technique might help to understand why the separation techniques affect the PNM of the resulting fractions.
References Fangueiro, D., Bol, R. and Chadwick, D. 2008. Assessment of the potential N mineralization of six particle size fractions of two different cattle slurries. Journal of Plant Nutrition and Soil Science, 171, 313-315.
Jorgensen S. and Jensen L. 2009. Chemical and biochemical variation in animal manure solids separated using different commercial separation technologies. Bioresource Technology, 100, 3088-3096.
Nitrogen Workshop 2012
Biochar reduces nitrate leaching in an apple orchard Ventura, M.a, Sorrenti, G.b, Panzacchi, P.b, Tonon, G.a a Faculty of Science and Technology, Free University of Bolzano/Bozen, Bolzano/Bozen, Italy b Department of Fruit Tree and Woody Plant Sciences, University of Bologna, Bologna, Italy
1. Background & Objectives Biochar is a by-product of pyrolysis that is the thermal decomposition of different organic sources under limited oxygen concentration at relatively low temperatures aimed at producing energy by syngas combustion. The incorporation of biochar into the soil has been proposed as a valid strategy to increase soil C storage. Furthermore, biochar has shown to promote plant growth increasing soil nutrient retention (Lehmann and Joseph, 2009). In particular, biochar has shown to reduce ammonium leaching in acidic tropical soils (Lehmann et al., 2003) and in laboratory conditions (Ding et al., 2010; Laird et al., 2010), however, information about alkaline soils and in field conditions is still totally lacking. The aim of the present study is to understand the potential of biochar for increasing soil N retention in calcareous, sub-alkaline soil.
2. Materials & Methods In spring 2009, 10 Mg of biochar per hectare was applied in a mature apple (Malus domestica Borkh.) orchard, growing on a calcareous, sub-alkaline soil (pH 7.3) and located in the Po Valley (Italy). Biochar was incorporated into the first 20-cm soil layer by surface soil ploughing. A similar soil perturbation was applied to control plots. Cumulative nitrate (NO3-) and ammonium (NH4+) leaching was measured 4 months after biochar addition and in the following year, by using ionexchange resin lysimeters (Susfalk and Johnson, 2002) installed below the ploughed soil layer. Leaf analysis was conducted to assess plants nutritional status. Soil pH and microbial biomass were also determined in treated and control plots.
3. Results & Discussion After 4 months, biochar treatment did not produce significant differences in the total amount of leached nitrogen, both as nitrate and ammonium (Figure 1a). On the contrary, in the following year NO3- leaching was significantly reduced in biochar treated soil in comparison to untreated soil (Figure 1b).
Figure 1. Cumulative ammonium nitrogen (N-NH4) and nitrate nitrogen (N-NO3) leaching after 4 months from biochar addition (a) and after the following year (b).
The symbol * denotes a statistically significant difference for p 0.05.
Soil applied biochar did not affect leaf chlorophyll (Chl) content, leaf dry weight and macronutrient content, while only leaf Zn concentration slightly decreased in amended soil (Table 1). Biochar treatment did not significantly affect microbial biomass nitrogen and soil pH values (data not shown). The observed NO3- leaching reduction may be due to different mechanisms, such as adsorption of NH4+ by charcoal, or the inhibition of nitrification with the consequent ammonium adsorption by clay particles (Berglund et al., 2004; Taghizadeh-Toosi et al., 2011). However, direct adsorption of nitrate by biochar particles cannot be totally excluded. The higher efficacy of biochar observed in the second year of the experiment might be due to a change in biochar properties with time.
* = significant for p 0.05; ns = not significant
4. Conclusion Even if the underlying physico-chemical mechanism is still unclear, the present study shows, for the first time, that soil biochar addition can significantly decrease nitrate leaching also in a sub-alkaline soil of temperate climates.
References Berglund, L.M., DeLuca, T.H. and Zackrisson, O. 2004. Activated carbon amendments to soil alters nitrification rates in Scots pine forests, Soil Biol Biochem 36,2067-2073.
Ding, Y., Liu, Y-X., Wu, W-X., Shi, D-Z., Yang, M. and Zhong, Z-K. 2010. Evaluation of Biochar Effects on Nitrogen Retention and Leaching in Multi-Layered Soil Columns, Water Air Soil Pollution 213,47-55.
Laird, D., Angelis, P., Wang, B., Horton, R. and Karlen, D. 2010. Biochar impact on nutrient leaching from a Midwestern agricultural soil, Geoderma 158,436-442.
Lehmann, J. and Joseph, S. 2009. Biochar for environmental management: An introduction, In: Lehmann J., Joseph S.
(eds), Biochar for environmental management: Science and technology, Earthscan, London pp 1-12.
Lehmann, J., Pereira da Silva, J., Steiner, C., Nehls, T., Kech, W. and Glaser, B. 2003. Nutrient availability and leaching in an archaeological Anthrosol and a Ferralsol of the Central Amazon basin: fertilizer, manure and charcoal amendments, Plant and Soil 249:343-357.
Susfalk, R.B. and Johnson, D.W. 2002. Ion exchange resin based soil solution lysimeters and snowmelt solution collectors, Communications in Soil Sciences and Plant Analysis 33,1261-1275.
Taghizadeh-Toosi, A., Clough, T.J., Condron, L.M., Sherlock, R.R., Anderson, C.R. and Craigie, R.A. 2011. Biochar incorporation into pasture soil suppresses in situ nitrous oxide emissions from ruminant urine patches, Journal of Environmental Quality 40,468-476.
Nitrogen Workshop 2012
Can an urease inhibitor mitigate N2O and NO emissions from urea fertilized Mediterranean agrosystems?
Sanz-Cobeña, A.a, Ábalos, D.a, Misselbrook, T.b, Sanchez-Martín, L.a, Téllez, A.a, García-Marco, S.a, Vallejo, A.a a ETSI Agrónomos, Technical University of Madrid, Ciudad Universitaria, 28040 Madrid, Spain b Rothamsted Research, North Wyke, Okehampton, Devon EX20 2SB, UK
1. Background & Objectives Urea is the cheapest and most commonly used form of inorganic N fertilizer worldwide, accounting for c. 50% of inorganic N use (Harrison and Webb, 2001). Nevertheless, the low efficiency of N-urea use by crops represents a threat to environmental quality and public health. It has been estimated that up to 60% of N-urea applied could be lost to the atmosphere via ammonia (NH3), nitric oxide (NO) and nitrous oxide (N2O), and to water streams through nitrate (NO3-) leaching. Among the proposed mitigation strategies to prevent N losses from urea fertilisation, urease inhibitors have been shown to effectively reduce NH3 volatilization (Sanz-Cobena et al., 2008). Additionally, few studies examine the effectiveness of NBPT to decrease the NO and N2O production rate in urea fertilized croplands (Ding et al., 2011). Results from two field experiments were used to evaluate the effectiveness of the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT, trade name Agrotain®) on abating N oxides emissions from urea fertilized agricultural soils in Central Spain.
2. Materials & Methods All experiments were carried out in the same location (i.e. “El Encín” field station, latitude 40◦32´N, longitude 3◦17´W). The mean annual temperature and rainfall in this area are 13.2ºC and 430 mm, respectively. The soil type is a Calcic Haploxerepts (Soil Survey Staff, 1992) with a sandy clay loam texture (clay, 28%; silt, 17%; sand, 55%) in the upper (0–28 cm) horizon. The cropping systems that were studied were barley and maize crops. Losses of NO and N2O were determined by static chambers (SanchezMartin et al., 2008). Measurements were carried out 3, 6, 9, 12 days after application in the 2 weeks after urea fertilization, and then once a week until the end of the sampling period. Urea (U) and NBPT coated urea (U+NBPT) (0.20% w/w) were applied in granular form. The N application rate was 100 and 250 kg N ha-1 for barley and maize, respectively. Following local agricultural practices, maize was irrigated by 404 mm and barley was set as a rainfed crop. A soil without N fertilizer applied was settled as a Control soil (C).