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2. Materials & Methods Aerobic long-term laboratory incubation experiments (182 days) were carried out with soils from rice-wheat double-crop rotations from two different locations in Jiangsu Province (Yixing (31°17’ N 119°53’E) and Huai’an (33°30’N 119°03’E), based on the method by Stanford and Smith (1972), modified by Nordmeyer and Richter (1985). At each site, field-moist soil samples from three depth increments (0-20 cm, 20-60 cm, 60-90 cm) were taken after field preparation for the winter wheat crop. Samples were mixed with quartz sand, filled in 60 ml plastic syringes, incubated by 35 °C and regularly leached with a 0.01 M CaCl2 solution on days 0, 3, 7, 14, 21, 35, 49, 70, 91, 119, 147 and 182 after the onset of the experiment. Mineral N (NO3--N and NH4+-N) in the leachates was determined by continuous-flow analysis and the cumulative amounts were used for estimation of mineralization parameters using a double exponential model with two first-order kinetics reactions (Richter et al., 1982):
}  The estimated parameters will subsequently be included in the HERMES model (Kersebaum, 1995;
Kersebaum and Beblik, 2001) for simulation of the N dynamics in the soil, water and plant system during the winter wheat growing period. Calibration and validation of simulation results will be performed with field Nmin, gravimetric water contents, as well as plant N uptake data, taken from field experiments conducted in Yixing and Huai’an during three winter wheat cropping seasons (2008-2011).
Soil properties in Yixing and Huai’an are presented in Table 1. The soil in Yixing was developed in alluvial deposits and has a silty clay loam texture. The soils on the experimental sites in Huai’an are relatively young and developed in limnic sediments with high clay contents.
Figure 1 shows the cumulative N mineralization in three depth increments of the soils from Yixing and Huai’an. As expected, highest amounts of N were mineralized in 0-20 cm depth of the soils in both locations with a distinctly higher N mineralization in the topsoil of Huai’an. The 20-60 cm depth showed a drastically lower N mineralization for both soils, with slightly higher amounts in the soil from Huai’an. Almost no N mineralization occurred in the 60-90 cm soils depth of both locations.
Yixing Huai‘an Figure 1. Cumulative N mineralization during 182 days in three depth increments (0-20 cm, 20-60 cm, 60-90 cm) of experimental soil from Yixing (left) and Huai’an (right), China; error bars represent s.d., n=4.
4. Conclusion The experimental results showed a clearly higher N mineralization in the soils from Huai’an, which can be explained by higher soil organic matter and clay contents (Table 1). These differences have to be considered for N fertilization recommendations. The results will be used for parameter adaptation in the HERMES model and for simulation of the N dynamics during the winter wheat growing season in rice-wheat systems.
Acknowledgements This research was funded by the Sino-German project “Nitrogen Management China”, BMBF-FKZ: 0330800C, MOST grant no. 2007DFA30850.
Kersebaum, K.C. 1995. Application of a simple management model to simulate water and nitrogen dynamics. In:
Ecological Modelling 81, p. 145-156 Kersebaum K.C. and Beblik A.J. 2001. Performance of a nitrogen dynamics model applied to evaluate agricultural management practices. In: Shaffer M., Ma L., Hansen S. (eds.) Modeling carbon and nitrogen dynamics for soil management. Lewis Publishers, Boca Raton, USA, pp 549–569
Nordmeyer, H. and Richter, J. 1985. Incubation experiments on nitrogen mineralization in loess and sandy soils. In:
Plant Soil 39, 433-445.
Richter, J., Nuske, A., Habenicht, W. and Bauer A. 1982. Optimized N-mineralization parameters of Löss-soils from incubation experiments. In: Plant Soil 68, 375-388.
Roelcke, M., Han, Y., Cai, Z.C. and Richter, J. 2002. Nitrogen mineralization in paddy soils of the Chinese Taihu Region under aerobic conditions. In: Nutr. Cyc. Agroecosyst. 63, 255-266.
Stanford, G. and Smith, S. J. 1972: Nitrogen mineralization potentials of soils. In: Soil Sci. Soc. Am. Proc. 36, 465– 472.
Nitrogen Workshop 2012
Nitrogen removal by fruits, leaves and pruning wood in a peach orchard Villar, J.M.a, Pascual, M.a, Fonseca, F.b, Lordan, J.a,b, Villar, L.a, Arbones, A.b, Rufat, J.b a Universitat de Lleida (UdL), ETSEA, Av Rovira Roure 191, 25198 Lleida, Spain b Institut de Recerca i Tecnologia Agroalimentàries, IRTA, Av Rovira Roure 191, 25198 Lleida, Spain
1. Background & Objectives Peach nitrogen fertilization could be optimized considering the diversity of agronomic practices.
Application rates range between 100-170 kg N ha-1. Nitrogen uptake and distribution has been studied in young nectarine trees (Tagliavini et al., 1999) and, for a mature peach orchard with 500tree/ha, Tagliavini et al (1996) calculated an annual removal of nitrogen of 109-157 kg N ha-1 (leaves contribution was estimated). The objective of this paper was to evaluate the effects of fertilisation on annual N removal of nitrogen in fruit, leaves and pruning wood, from a mature peach orchard, on a shallow calcareous soil with high soil organic matter content.
2. Materials & Methods A five-year field experiment (2006–2010) on clingstone peach (Prunus persica (L.) Batsch cv.
Andross), grafted on GF305 rootstock (5x2.8 m; 715 trees ha-1) was conducted in a commercial orchard under mechanical harvesting for the processing industry. A 3x3 factorial design with randomized complete blocks and four repetitions was established Three nitrogen doses were evaluated: 0, 60 and 120 kg N ha-1, combined with three drip irrigation treatments: full irrigation throughout the growing season; restricted irrigation during stage-II (70% restriction) and restricted irrigation during stage-III (30% restriction). N content in the irrigation water was negligible. The soil type was a shallow, well-drained, loam which had a petrocalcic horizon within 45 cm of the soil surface (Petrocalcid Calcixerepts). The soil had a pH of 8.4, and 2.5-3% organic matter (OM). Trees were fertigated (N32 solution) on a daily basis. Soil was sampled to determine nitrate content (2 cores inside the wet volume). Fruit (endocarp and mesocarp), leaf and pruning wood dry matter were measured and analysed for N to estimate total N removal. Apparent nitrogen recovery (ANR) was the additional N uptake per unit of added nutrient (kg kg-1) and was calculated as described by Greenwood and Draycott (1989). The effect of N treatment on N removal by fruit, leaves and pruning wood corresponds to 2009 (fourth experimental year). Statistical analysis of data was carried out using the SAS-STAT package (SAS, Version 9.2.)
3. Results & Discussion Tree N removal has been higher than the applied N (Table 1). Full irrigation treatment (4270 m3 ha-1 until harvest) combined with N60 achieved the highest yield (data not shown). N fertilisation increased the annual removal of N as it was demonstrated by Rufat and DeJong (2001). This irrigated mature orchard removed a high amount of nitrogen (total N removal ranged between 136 and 189 kg N ha-1). The roots and the permanent framework (trunk and branches) were not included. Average N removal by endocarp was 15% of the total fruit (ranged from 12 to 18%).
Leaves and pruning wood showed a similar amount of N removal. In this farm, the pruning wood is chopped and left on the soil surface. Average N recovery was 76.4 % for N60 treatment and 47.8% for N120 treatment (Table 2). These ANR were very high due to fertigation practice. N taken up by the N0 treatment trees comes from OM mineralization and from the initial soil NO3-N content (4.3 mg kg-1). Initial soil nitrate content was not different between treatments. Table 3 shows how the soil NO3-N content (0-35 cm) inside the wet bulb at the end of stage-II increased with N application.
4. Conclusions The application of N fertiliser throughout fertigation to peach orchards increased on average between 32-40% the total annual removal of N. N0 treatment showed an important amount of N uptake, being the soil organic matter mineralization and the leaves and pruning wood decomposition the main N sources. Highest fertilizer recovery was achieved for N60 treatment and this amount would be advisable to farmers. Any N application is not advisable when irrigation and nitrogen are properly applied.
References Greenwood D.J. and Draycott A. 1989. Experimental validation of an N-response model for widely different crops.
Fertil Res 18, 153-174.
Rufat J.and DeJong T.M. 2001. Estimating seasonal nitrogen dynamics in peach trees in response to nitrogen availability. Tree Physiol. 21 (15):1133-1140.
Tagliavini, M., Scudellari D., Marangoni B. and Toselli M. 1996. Nitrogen fertilization management in orchards to reconcile productivity and environmental aspects. Fertilizer Research 43, 93-102.
Tagliavini M., Millard P., Quartieri M. and Marangoni B. 1999. Timing of nitrogen uptake affects winter storage and spring remobilisation of nitrogen in nectarine (Prunus persica var. nectarina) trees. Plant and Soil 211(2), 149-153.
Nitrogen Workshop 2012
Nitrogen sources and sinks in a heavily impacted watershed (Oglio River, Northern Italy) Laini, A.a, Sacchi, E.b, Soana, E.a, Delconte, C.A.b, Racchetti, E.a, Bartoli, M.a and Viaroli, P.a a Department of Environmental Sciences, University of Parma,Viale G.P. Usberti 33/A, 43124 Parma, Italy b CNR-IGG, U.O.S. Pavia and Department of Earth and Environmental Sciences, University of Pavia, via Ferrata 1, 27100 Pavia, Italy
1. Background & Objectives Increased reactive nitrogen (N) input to the biosphere by human activities has resulted in the gradual saturation of the N buffering capacity of terrestrial areas and increased N loads to aquatic ecosystems. Farming activity is one of the primary causes for the current high N loads, due to unbalanced livestock manure production and agricultural lands availability for spreading. The control of N inputs to aquatic systems is of general public interest due to ecosystemic consequences as eutrophication and the potential nitrite toxicity. Rivers are particularly critical because they link terrestrial and coastal ecosystems, and aggregate stressors occurring at the landscape scale.
Worldwide N budgets suggest that up to 75% of the N load generated within catchments is retained and not exported via river discharge. N retention is the result of several processes, among which some are well studied (i.e., crop uptake) while others are scarcely investigated (i.e. denitrification in lotic ecosystems, N storage in soils, percolation and N transformations in groundwater) and represent large, unknown terms in N budgets. The aim of this study is to provide a detailed analysis of N budget and pathways in a river basin with a large N surplus, and in particular to explore the fate of the N pool retained within the watershed.
2. Materials & Methods The study was conducted on the Oglio River and watershed, (156 km river stretch and 3,800 km2 watershed area), located within the Po basin, northern Italy. Agricultural nitrogen balances were performed for the year 2008 using the “soil system budget” approach (Oenema et al. 2003).
Farming census data were used to compare N input (livestock manure, synthetic fertilizers, atmospheric deposition, biological fixation and wastewater sludge) and output (crop uptake, ammonia volatilization and denitrification in soils) within the catchment’s agricultural land.
Industrial and domestic inputs were also calculated using census data from National Statistics Institution. The watershed N export was estimated from monthly measurements (years 2000 to
2008) at the Oglio River closing section; here water flow and dissolved and particulate N forms are regularly monitored by the Oglio Consortium and by the Regional Agency for the Environment.
Denitrification was measured in riverine wetlands by means of the isotope pairing technique (Nielsen, 1992) and in the river course using a dual isotopic approach (Silva et al., 2000).
Theoretical denitrification rates in the secondary drainage system were estimated according to Soana et al. (2011). Lowland springs (n=30) were sampled bimonthly from December 2010 to October 2011; water samples were collected and analysed in the laboratory for nitrate NO3-, nitrite NO2- and nitrous oxide N2O concentrations via spectrophotometry and gas chromatography.
3. Results and Discussion The N mass balance suggests a large N surplus in this area, with livestock manure and synthetic fertilizers contributing 85% of total N inputs from agriculture (about 100 kt N yr-1) and largely exceeding crop uptake, soil denitrification and volatilization (about 60 kt N yr-1). Nitrogen from domestic and industrial origin is relatively small, contributing 5.8 and 7.2 kt N yr-1, respectively.
Annual export of N from the watershed is about 13 kt N yr-1, resulting in a large excess unaccounted (~40 kt N yr-1) for in unknown temporary or permanent N sinks.
Nitrogen Workshop 2012
The watershed out flow had enriched nitrate stable isotope composition but calculations suggest a N removal corresponding to at most ~3 kt N yr-1. Although denitrification rates in wetlands are high they result in low N removal (1% of the missing N amount) due to their small surface area and limited lateral connectivity.
Figure 1. Nitrate and nitrous oxide concentrations in lowland springs.