Changes of greenhouse gases emission from agricultural soils under the influence of mineral fertilizers

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1 Symposium no. 65 Paper no. 246 Presentation: poster Changes of greenhouse gases emission from agricultural soils under the influence of mineral fertilizers KOZLOV A.E., STEPANOV A. and MANUCHAROVA N. Moscow State University, Department of Soil Biology, Moscow, Russia Abstract It has been studied the influence of the intensive use of mineral fertilizers on the decomposition of soil organic matter and emission of carbon dioxide and methane from soils to the atmosphere. of experiment included using of mineral forms NPK-fertilizers (ammonium nitrate/ superfosphate/ potassium chloride). In presence of P 7 K 14 fertilizers doses of mineral nitrogen varied from 9 to 15 kg N ha -1 applied to forest (podzolic) soil under Zea mays L. crops. The level of greenhouse gases emission increased proportionally to doses of added N-fertilizers ( g C-CO 2 g -1 h -1 and g C-CH 4 g -1 h -1 ). It was shown that using NPK-fertilizers simultaneously with application of clay minerals (ceolites) accompanied by decrease of CO 2 flux from 31.9 to 15.7 g C-CO 2 g -1 h -1 and from.77 to.13 g C-CH 4 g -1 h -1. The marked effect was absent when high doses (15 kg N ha -1 ) of N-fertilizers were added because of exceeding of CEC (Cation Exchange Capacity 15 mg equivalent NH 4 + ) of these minerals. It was proved that intensive use of NPKfertilizers caused changes in a structure of microorganisms complex accompanied by changes in biogeochemical carbon cycle in the soil. This leads to increase in the rate of decomposition (emission CO 2 and CH 4 ) in the following years even without using of mineral fertilizers. Thus, emission of greenhouse gases from variants where the largest dose was used (31.9 g C-CO 2 g -1 h -1 and.77 g C-CH 4 g -1 h -1 ) exceeded emission from control (without fertilizers) in 1.5 times for CO 2 and in 4 times for CH 4 (2.7 g C-CO 2 g -1 h -1 and.19 g C-CH 4 g -1 h -1 ). This permits to make a conclusion about changes in biogeochemical cycle of carbon caused by using of mineral fertilizers that leads to considerable emissions of CO 2 from agricultural soils to atmosphere. Keywords: greenhouse gases, emission, mineral fertilizers, carbon cycle, agricultural soil Introduction The global role in climate and environment changes belongs to the carbon cycle. Carbon dioxide is the most important gas responsible for the formation of greenhouse effect. Recent concentration in the atmosphere is about 345 mg kg -1 with annual increase nearly.5%. Another important micro component of atmosphere that has influence on the process of global climate change is methane. The main source of CH 4 in biosphere is the process of its microbial transformation in soils. Two antagonistic 246-1

2 17 th WCSS, August 22, Thailand processes the formation and absorption by methanogenic and methanotrophic bacteria, determine the magnitudes of methane fluxes. The estimates of CO 2 and CH 4 emission coming from cultivated soils helps to understand the contribution of soils in greenhouse effect. In this paper we report results of our investigation of CO 2 and CH 4 emissions from forest (podzolic) soil under Zea mays L. crops. We analyzed the influence of different doses of mineral fertilizers on the variations in fluxes observed, compared the magnitudes of carbon dioxide and methane emission during three months and discussed the impact of N-fertilizers on the degradation of soil organic matter. Materials and Methods Samples of forest (podzolic) soil were used (ph 5.8, C - 3.4%, P 2 O 5-7 mg kg -1, K 2 O-65 mg kg -1 ). To determine potential emissions of CO 2, weighted portions of airdried soil (5 g) were placed in 15-mL flasks sealed by rubber stoppers mg of glucose was added together with water to each sample. The samples were placed in a thermostat at 28 o C and incubated for 24 hours. ( The methods of soil microbiology and biochemistry (199)..5 ml of gas phase from every flask was injected into a gas chromatograph (model 37) with a column length of 3.2 m by inner diameter of 2 mm filled with Polysorb-1, with a thermo capture detector (current 15 ma; thermostat temperature 3 o C; carrier gas helium, 25 ml min -1 ). The methane content in the gas phase was measured on the gas chromatograph Chrom-41 with a column length of 3.2 m filled with Serosil (thermostat temperature 3 o C; carrier gas argon, 3 ml min -1 ; hydrogen 2 ml min -1 ; air 1 ml min -1 ). Our work consists of two series of experiments. In the first one we use mineral fertilizers by following scheme (in nutrient elements, kg ha -1 ): P 7 K 14, P 7 K 14 N 9, P 7 K 14 N 15, P 7 K 14 N 9c and P 7 K 14 N 15c (ammonium nitrate modified by ceolites). In the second series mineral fertilizers were used previous year. The scheme was: Control (without fertilizers), P 7 K 14, P 7 K 14 N 9 and P 7 K 14 N 21. Nitrogen was taken in a form of ammonium nitrate, phosphorus in a form of superfosphate and potassium as potassium chloride. The samples were taken during the period of vegetation (June, July, August) from arable horizon from the beginning of using fertilizers. Results Our investigation showed that intensive use of mineral fertilizers leads to sudden increase of CO 2 and CH 4 emission from agricultural soil. Thus, using of PK-fertilizers has led to increase of carbon dioxide emission (in comparison with control) in 1, 8 times from 8.1 to 13.5 g C-CO 2 g -1 h -1 and methane emission in 1.4 times from.19 to.27 g C-CH 4 g -1 h -1 (June). Application of full NPK mineral fertilizer accompanied by higher CO 2 and CH 4 fluxes from soil. Using NPK in doses of 9 and 15 kg ha -1 increase the intensity of emission to 21.8 and 23.1 g C-CO 2 g -1 h -1 and to.5 and.65 g C-CH 4 g -1 h -1, respectively. Study of ceolites influence on the ratio of carbon dioxide and methane emission has shown that simultaneously use of P 7 K 14 N 9 and ceolites accompanied by decrease of emission. Application of high doses of nitrogen fertilizers (15 kg ha -1 ) made this effect 246-2

3 17 th WCSS, August 22, Thailand not marked, magnitudes of emission decreased from 23.1 to 22 g C-CO 2 g -1 h -1 and.65 to.61 g C-CH 4 g -1 h -1 (Figures 1, 4). In July emission of CO 2 in variants with the application of PK-fertilizers increased from 2.7 to 26.2 g C-CO 2 g -1 h -1 (in 1, 3 times in comparison with control). In variants where ceolites were added to P 7 K 14 N 15 CO 2 flux decreased from 31.9 to 27.7 g C-CO 2 g -1 h -1 and CH 4 flux from.77 to.57 g C-CH 4 g -1 h -1 (Figures 2, 5). In August the differences between the magnitudes of CO 2 and CH 4 emission in control and in variants with using of PK-fertilizers were smaller (carbon dioxide flux varied from 23.8 to 25.5 g C-CO 2 g -1 h and methane flux from.7 to.75 g C-CH 4 g -1 h -1 ). But the effect from ceolites use was marked. Thus, emission of CO 2 and CH 4 from the variants with ceolites and N-fertilizers in a dose of 9 kg ha -1 was15.7 g C-CO 2 g -1 h -1 and.13 g C-CH 4 g -1 h -1 ; from the variants without ceolites but with the same dose of NH 4 NO g C-CO 2 g -1 h -1 and.24 g C-CH 4 g -1 h -1. The magnitude of CO 2 and CH 4 emission with the application of a high dose of nitrogen (15 kg ha -1 ) achieved 3.5 g C-CO 2 g -1 h -1 and.62 g C-CH 4 g -1 h -1 ; and in variants where ceolites were simultaneously used-28.4 g C-CO 2 g -1 h -1 and.56 g C-CH 4 g -1 h -1, respectively (Figures 3, 6). Consequently, using of mineral fertilizers accompanied by considerable losses of carbon in a form of methane and carbon dioxide. Results of our work have shown that even on the second year after application of mineral fertilizers their influence on CO 2 and CH 4 emission from agricultural soil maintained. In June CO 2 fluxes increased from 8.1 (in a control) to 12., 15., 18.8 g C- CO 2 g -1 h -1 in variants where P 7 K 14, P 7 K 14 N 9 and P 7 K 14 N 21 were used in the previous year. Methane fluxes increased from.19 (control) to.27,.68 and.77 g C-CH 4 g -1 h -1. In July higher magnitudes of CO 2 emission were observed, this led to increase of the difference between control and variants with PK-fertilizers (on 13%) and with the use of NPK-fertilizers (on 24%). In August the same tendency was observed. In control CO 2 emission was 23.8 g C-CO 2 g -1 h -1, and in variants where mineral fertilizers were put before, they were higher: 27.-g C-CO 2 g -1 h -1 (P 7 K 14 ) and 38.7 g C-CO 2 g -1 h -1 (P 7 K 14 N 21 ). µg µg C-CO C-C2 2 g-1h-1 g -1 h -1 JUNE p7k14 p7k14n9 p7k14n15 p7k14n9c p7k14n15c Varients Figure 1 Emission of CO 2 (with application of fertilizers)

4 17 th WCSS, August 22, Thailand µg µg C-CO2 2 g-1h-1 g -1 h -1 JULY p7k14 p7k14n15 p79k14n15c Figure 2 Emission of CO 2 (with application of fertilizers) µg C-CO2 g-1h-1 2 g -1 h August p7k14 p7k14n9 p7k14n15 p7k14n9c p7k14n15c Fi 3 E i i f CO2 ( ith li ti f f tili ) Figure 3 Emission of CO 2 (with application of fertilizers).,7 µg C-CH4 g-1h-1 4 g h -1,6 JUNE,5,4,3,2,1 P7K14 P7K14N9 P7K14N15 p7k14n9c p7k14n15c Figure 4 Emission of CH 4 (with application of fertilizers)

5 17 th WCSS, August 22, Thailand JULY µg C-CH 4 g -1 h -1 µg C-CH4 g-1h- 1,8,7,6,5,4,3,2,1 P7K14 P7K14N15 P7K14N15C Figure 5 Emission of CH 4 (with application of fertilizers). µg C-CH 4 g -1 h -1 µg C-CH4 g-1h-1 AUGUST,7,6,5,4,3,2,1 P7K14 P7K14N9 P7K14N15 P7K14N9C P7K14N15C Figure 6 Emission of CH 4 (with application of fertilizers). Conclusion (1) Carbon dioxide and methane fluxes from soil increase proportionally the dose of mineral nitrogen in the composition of fertilizers. Thus, the largest losses (31.9 g C- CO 2 g -1 h -1 and.77 g C-CH 4 g -1 h -1 ) were fixed in variants with the application of full mineral fertilizer P 7 K 14 N 15. (2) Application of nitrogen fertilizers simultaneously with the ceolites accompanied by decrease of CO 2 and CH 4 emissions from soil to atmosphere. Ceolites are the clay minerals with high absorption capacity. The crystalline lattice of these minerals may fix the NH4 + -ions and so they are gradually liberated into the soil. That s why ceolites use leads to decrease of CO 2 and CH 4 emissions. Applications of doses of mineral fertilizers exceed their CEC (Cation Exchange Capacity-15 mg equivalent NH 4 + ) led to decrease of effectiveness of their employment. (3) Using of mineral fertilizers accompanied by changes in CO 2 and CH 4 emission even on the second year after their application

6 17 th WCSS, August 22, Thailand (4) The results of our work permit to make a conclusion that use of mineral fertilizers leads to increase of soil s biological activity and considerable mineralization of organic matter what expressed in intensive emission of carbon dioxide and methane from cultivated soil to atmosphere. References D.G. Zvyagintsev, M., ed The Methods of Soil Microbiology and Biochemistry. 34, Moscow University Press