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References Bond J. J. and Willis, W.O, 1969. Soil water evaporation: surface residue rate and placement effects. Soil Science Society of America Proceedings, 33, 445-448 Findeling A., Garnier P., Coppens F., Lafolie F. and Recous S. 2007. Modeling water, carbon and nitrogen dynamics in soil covered with decomposing mulch. European Journal of Soil Science 58, 196-206.
Nitrogen Workshop 2012
Impact of two different types of grassland-to-arable-conversion on nitrous oxide emission and nitrate leaching Roth, G.a, Helfrich, M.a, Well, R.a, Flessa, H. a a Institute of Agricultural Climate Research, Johann Heinrich von Thünen-Institute, Federal Research Institute for Rural Areas, Forestry and Fisheries, Braunschweig, Germany
1. Background & Objectives Conversion of grassland to arable land often causes enhanced nitrous oxide (N2O) emissions to the atmosphere (Conen, Dobbie et al., 2000; Grandy and Robertson, 2006) as well as augmented nitrate leaching to the groundwater (Strebel, Böttcher et al., 1988). This is due to the tillage of the sward and subsequent decomposition of organic matter. However, prediction of such effects is uncertain so far because emissions may differ depending on site and soil conditions. We aim to evaluate the impact of grassland-to-field-conversion on N2O fluxes, mineral nitrogen (Nmin) content and the eluviation of nitrate. Moreover, we compare two different types of conversion (mechanical and chemical).
2. Materials & Methods At two sites, in Kleve (North Rhine-Westphalia, Germany, conventional farming, silt loam over clay loam) and Trenthorst (Schleswig-Holstein, Germany, organic farming, sandy silt loam), a four times replicated plot experiment with (i) mechanical conversion (ploughing, maize), (ii) chemical conversion (broadband herbicide, maize per direct seed) and (iii) continuous grassland as reference was started in April 2010. In Trenthorst we established additionally (iv) a continuous field with maize as reference. Over two years, Nmin content, water content as well as gas emissions were measured weekly. For gas emissions, we used a closed chamber system (Flessa, Dörsch et al., 1995). Soil samples for Nmin analysis were taken in 0-10cm and 10-30cm depths. In the second year, leachate was sampled in suction cups installed in 35cm depth and analysed for Nmin and dissolved organic N (DON).
3. Results & Discussion The time series of N2O emissions (Figure 1) and Nmin content (Figure 2) are shown for the Kleve site.
The peak emissions of N2O correlated with the dates of harvest, soil tillage or fertilization in autumn 2010. Increased emissions in the grassland could be due to the wet autumn which was reflected by high water contents. Cumulative N2O fluxes of the converted grassland were high (6.2
We found significant differences between conversion, both, chemical and mechanical, and the reference plots within the first year. While in Kleve were significant differences between the two types of conversion in Trenthorst there was none (Table 1).
4. Conclusions Following grassland-to-arable-conversion, there was a clear increase in N2O fluxes within the first two years. The time series of N2O emissions and Nmin was strongly affected by soil tillage and water content. The type of grassland-to-arable-conversion had was significant on one site, but not on the other. The differences between the two sites were mainly due to the different fertilization.
We also collected gas samples to analyse isotopic signatures of N2O to elucidate the processes responsible for elevated N2O fluxes from the converted grassland.
References Conen, F., Dobbie, K. E. and Smith, K. A. 2000. Predicting N2O emissions from agricultural land through related soil parameters. Global Change Biology 6(4), 417-426 Grandy, A. S. and Robertson, G. P. 2006. Initial cultivation of a temperate-region soil immediately accelerates aggregate turnover and CO2 and N2O fluxes. Global Change Biology 12(8), 1507-1520 Strebel, O., Böttcher, J., Eberle, M. and Aldag, R. 1988. Quantitative and qualitative changes in soil porperties of Ahorizons of sandy soils caused by conversion of grassland to arable land. Zeitschrift fur Pflanzenernährung und Bodenkunde 151(5), 341-347 Flessa, H., Dörsch, P. and Beese, F. 1995. Seasonal-variation of N2O and CH4 fluxes in differently managed arable soils in southern Germany. Journal of Geophysical Research-Atmospheres 100(D11), 23115-23124
Nitrogen Workshop 2012
Improving N efficiency in barley through green manure management and biogas slurry Frøseth, R.B.a, Bakken, A.K.a, Bleken, M.A.b, Riley, H.a, Thorup-Kristensen, K.c, Hansen, S.a a Norwegian Institute for Agricultural and Environmental Research (Bioforsk), Norway 1)Organic Food and Farming Division, 6630 Tingvoll ; 2) Grassland and Forage Crops Divison, 7500 Stjørdal; 3) Arable Crops Division, 2849 Kapp b Department of Plant and Environmental Sciences, University of Life Sciences, 1432 Ås, Norway c Department of Agriculture and Ecology, Faculty of Life Sciences, University of Copenhagen, 2630 Taastrup, Denmark
1. Background & Objectives In cereal production on stockless organic farms green manure (GM) is commonly used to improve soil fertility. The clover-grass swards are mown frequently as a means to control perennial weeds in GMcereal rotations and to keep the ley in a vegetative state, thus avoiding decrease in biomass production and in N2-fixating activity. The mown GM herbage is commonly mulched (Dahlin et al., 2011). The purpose of this study was to increase knowledge of the N-dynamics in such rotations, in order to suggest methods for improving N efficiency and thus organic cereal yields. The hypothesis was that spring application of biogas residue from anaerobic digestion of GM herbage increases the N uptake and yield of a subsequent barley crop, compared to repeatedly in situ mulching of the same GM herbage in the preceding season.
2. Material & Methods The effect of various GM treatments on spring barley yields and nitrogen dynamics was investigated, at four sites differing in soil and climatic conditions. The locations were Central Norway (Site 1: silty clay loam and Site 2: sandy loam), Eastern Norway (Site 3: loam) and South-Eastern Norway (Site 4: clay loam). In 2008 a grass clover mixture was undersown in barley. In 2009 the clover-grass herbage was either harvested or mulched. In spring 2010 the GM sward was ploughed down, and barley was sown. Six treatments were compared (Table 1), with four replications. Biogas residue from anaerobically digested GM herbage was applied in spring 2010. It contained 11 g total N and 6 g NH4-N m-2 (56 % of the total N in the GM herbage). Two control treatments were included, in which cereals were grown in all three years (without any fertilizer in 2008 and 2009, and with biogas residue or mineral fertilizer in 2010).
Soil mineral-N was analysed at 0-0.8 m depth on several occasions from 2008 until spring 2011.
3. Results & Discussion On average, the mulched or harvested GM herbage contained 19 g N m-2. In spring 2010, before ploughing down the GM, there was a higher level (P 0.001) of mineral N in soil with GM mulched (GM+) compared with the other treatments at all sites. But two weeks after germination of the barley crop there were no difference in the levels of mineral-N in soil between GM mulched (GM+) and removed (GM-).
Nitrogen Workshop 2012
Barley dry matter yields in 2010 were approximately 300 g m-2, except in trial 1, where it was only half as high. The use of biogas residue (GM-(B)), raised the nitrogen yield of the barley crop to the same level as of the mulched treatment (GM+). When biogas residue was applied on control plots that had been exhausted by two consecutive cereal crops without any form of fertilization (C (B)) the nitrogen yield of the barley crop reached the same level as the treatment of GM with two of three harvests removed (GM2/3).
At sites 1, 2 and 3 barley N yields in 2010 (Figure 1) were 29-38 % lower (P 0.001) when GM herbage was removed (GM- and GM2/3) than when it was mulched (GM+). In these trials, N deficiency symptoms in barley were seen already at the 3rd leaf stage on plots where the GM herbage had been removed. At site 4, there was a similar trend, but the effect was not statistically significant.
Figure 1. Nitrogen yields of barley grain in 2010 (g m-2 ± standard deviation) following contrasting green manure treatments in 2009 in four trials.
Abbreviations for green manure treatments are explained in Table 1.
In spring 2011 there was a higher level (P 0.001) of NO3-N in soil with GM in 2009 than without, but no effect of the different GM treatments was seen in NH4 -N content.
4. Conclusions The results suggest that, under the Norwegian climate, mulching of GM herbage can increase cereal yields compared to its removal, depending on soil type and rotation history. However, the use of GM herbage for biogas production appears to be much more N-efficient on farm level. We applied about half of the N available in GM herbage, and the surplus residue makes it possible to manure other fields.
References Dahlin A.S., Stenberg M. and Marstorp H. 2011. Mulch recycling in green manure leys under Scandinavian conditions, Nutrient Cycling in Agroecosystems 91:119-129.
Nitrogen Workshop 2012 Influence of fertilisation practice on gas and grain yield production Bálint Á.a, Hoffmann S.b, Berecz K. †b, Kristóf K.a, Kampfl Gy.a, Nótás E.a, Horváth M.a, Gyarmati B.a, Molnar E.a, Anton A.c, Szili-Kovács T.c, Heltai Gy.a a Department of Chemistry and Biochemistry, Szent István University, Gödöllő, Hungary b Institute of Plant Production and Soil Sciences, University of Pannonia, Keszthely, Hungary c Institute for Soil Sciences and Agricultural Chemistry, Centre for Agricultural Research, MTA, Budapest, Hungary
1. Background & Objectives CO2, N2O, CH4 and NO emissions are studied extensively (Akimoto et al., 2005; Mørkved et al., 2006; Ruser et al., 2006) because their presence in air causes environmental problems e.g. global warming and stratospheric ozone depletion. To explore the role of fertilisation practices to this phenomenon, experimental examinations of soil gas emission with different scales have particular importance. Hence, the objective of our research was to investigate this complex relationship by comparing the effects of organic and mineral fertilisers on GHG emission and grain yield production. The research project started in 2007 was realized at four levels: in long term field, mesocosm, microcosm and column experiments. The GHG emissions from the different experimental setup were compared and analyzed. In this paper only part of the soil column experiment (2010) is presented.
2. Materials & Methods Six undisturbed soil columns were taken from the set-aside (Eutric Cambisol soil) at Keszthely, Hungary (46°40’ N; 17°15’ E). The columns were 90 cm high and 40 cm in diameter. Soil texture was a sandy loam with low organic matter and P content and medium K content, pH(KCl)= 7.1. The soil columns had different fertilization treatments: 1. control without maize seeding and fertilisation (0), 2. 105 Mg hectare–1 equivalent NPK fertilisation without maize seeding (NPK), 3. control with maize seeding (M), 4. maize seeding and 105 Mg hectare–1 equivalent NPK (M+NPK), 5. maize seeding and farmyard manure, 105 Mg hectare–1 equivalent (M+FYM), 6. maize seeding and 105 Mg hectare–1 NPK fertilisation plus 105 Mg hectare–1 NPK equivalent farmyard manure (M+NPK+FYM). Soil surface CO2 fluxes were measured by gas sampling from a closed-chamber inserted into the top of each column at zero and at 30 minute after closure. Gas samples were taken each time at about 8 a.m. by a gas-tight syringe and injected into evacuated Exetainer tubes (Labco Limited, UK). The gas concentrations were measured by gas chromatograph (HP 5890, equipped with Porapak Q column to measure carbon dioxide, which was detected by thermal conductivity).
Soil samples were also taken to measure active microbial biomass by substrate-induced respiration (SIR) and microbial activity based on fluorescein-diacetate hydrolysing activity (FDA).
3. Results & Discussion Treatments had significant effect on SIR and FDA (Figure 1) although the effects of individual treatments could not be distinguished. Manure treatments caused significantly higher microbial biomass and activity during summer. On the other hand the presence of maize did not clearly appeared in the SIR and FDA values. We established significant correlation between SIR and FDA (r= 0.596; p= 0.0001). Three peaks of CO2 fluxes (Figure 2) were observed during the 141 day long period, the first between 9th and 11th days after seeding of maize, the second on 86th day (21th July) in all treatments while on 37th (2nd June) only at manure treatments. The mean values of CO2 fluxes varied between 21 and 2052 mg CO2 m-2 hour-1. The correlation between surface CO2 flux and SIR was marginally significant (r= 0.302; p= 0.073) while between CO2 flux and FDA was significant (r= 0.47; p= 0.004).
2010.05.03 2010.05.10 2010.05.17 2010.05.24 2010.05.31 2010.06.07 2010.06.14 2010.06.21 2010.06.28 2010.07.05 2010.07.12
Figure 1. Fluorescein-diacetate hydrolysing (FDA) activity in surface soil samples during the vegetation season (0 = control; NPK = NPK treatment; M = presence of maize plant; FYM= farmyard manure) and linear regression between SIR and FDA in all soil samples in soil column experiment.
Figure 2. Sampling of gas and surface CO2 flux from soil columns during the vegetation season from 13th April till 1st September (0 = control; NPK = NPK treatment; M = presence of maize plant; FYM= farmyard manure).
4. Conclusions Treatments had significant effects on surface CO2 flux, SIR and FDA, and they were in correlation with each other. The highest CO2 flux, SIR and FDA were found in the combined NPK+FYM treatment.
Acknowledgement The National Scientific Research Fund supported this work (OTKA K: 72926, 73326, 73768).