1. EMISSIONS OF NOx AND N 2 O FROM OXISOL CULTIVATED WITH COTTON IN THE CERRADO REGION, BRAZIL Êrika Fernandes (CEFET/BA - UnB) Mercedes Bustamante (UnB) Alessandra Kozovits (present address UFOP) Richard Zepp (EPA)

2. - ~2 millions km² of the central Brazilian Plateau. - Correspond ~24 % of the country's area - The second largest of Brazil's major biomes - Seasonal rainfall (total: 800-1800 mm): - Wet season (October to April) - Dry season (May to September) - The soils are dystrophic: - 46 % are Oxisols (“Latossolos”) (clayey soils but well-drained, acidic, high Al saturation and low CEC) Cerrado (tropical savana) - overview

3. Land use in the Cerrado Region - 1950’s: The construction of Brasilia improved transportation and infrastructure in Central Brazil - 1970’s: There was an expansion of agriculture * development of crops adapted to soil * natural conditions for mechanized - Today, the Cerrado is the most important region for grain and meat production in Brazil  Exported products Original Cerrado area In 2002 the Cerrado veg. is fragmented

4. Value of exportation from the Center-west in 2001 US$ 2,5 Billions Of this total, the following products contributed with ~76%, In decreasing order: In decreasing order: Product % Soybean (grain) 41,48 Soybean related products 21,39 Meat (frozen) 7,32 Meat (fresh) 3,25 Cotton 2,41 TOTAL 75,85 Fonte: IBGE 2000/SCO-MI Ministério da Integração Nacional Secretaria de Desenvolvimento do Centro-Oeste

5. - Federal state of Goias (GO) (an area of old agricultural occupation) 1990 - 35.000 ha 2004 - 142.000 ha (4 x) - Federal state of Mato Grosso (MT) (a new agricultural frontier) 1990 – 43.000 ha 2004 - 470.000 ha (10 x) Source: Brazilian Ministry of Agriculture Evolution of the area with cotton GO MT

6. Nitrogen management Cotton x soybean Cotton cultivation in the Cerrado is an option to soybean In many cases, used in rotation with soybean However,  Cotton demands N fertilization (90-150 kg N per hectare)  While soybean does not demand N fertilization (N is supplied by biological fixation) Land use changes associated with fertilization may have important consequences for the soil- atmosphere exchange of NOx and N 2 O emissions

7. Objective As there are few data on NOx and N 2 O fluxes in Cerrado region agroecosystems Here, we will report data on NOx and N 2 O emissions from a Oxisol planted with cotton under no till management under Brachiaria straw

8. The study was carried out at the Pamplona Farm, located in Cristalina – GO, Brazil (16  15` 02`` S and 47  37` 02`` W) Central part of the Cerrado region Brasília GOIÁS MG TO BA MT MS Study site. Cristalina

9. Study site: - Cotton field - Native cerrado (a control site) Study period: - November/2004 to August/2005 - N emissions were measured monthly - wet and dry season Methodology

10. Cultivation phases: - before planting - planting with row fertilization 24 kg N ha -1 as di-ammonium phosphate - surface fertilization 36 kg N ha ‑ 1 as ammonium sulfate 90 kg N ha ‑ 1 as urea - Along the growing season - before and post harvest Before planting Before harvest

11. In the crop rows   5 m 10 m Methodology Between the crop rows  chamber (PVC)  Sampling site:

12. N oxides measurements Soil surface fluxes of NO and N 2 O were measured using polyvinyl chloride (PVC) chambers; NO was analyzed using a Scintrex LMA-3; The N 2 O samples were collected using 60 mL polypropylene syringes and analyzed with a gas chromatograph (Shimadzu GC-14A); Statistical tests were used to make comparisons among:  cultivation phases;  cultivation phases and native cerrado.

13. 1.Fluxes before planting were very variable – probably because of Brachiaria straw 2. However, there was no difference between fluxes before planting and after planting with row fertilization with di-ammonium phosphate (24 kg N ha -1 ) NO fluxes

14. 3. Slightly higher NO emissions were measured four hours after surface fertilization with ammonium sulfate (36 kg N ha -1 ) - In the crop rows (6 X) - Between the crop rows (2 X)

15. 4. A large pulse of NO was observed 3 days after the third fertilization when 90 kg N ha ‑ 1 were applied: Pulse = 39,3  20,1 ng N cm -2 h -1 (In the crop rows) Pulse = 83,3  11,9 ng N cm -2 h -1 ( Between the crop rows) NO fluxes 5. In cultivation phases after fertilizations, NO fluxes in the cotton field were similar to fluxes in the native cerrado

16. N 2 O fluxes - Most of the N 2 O fluxes measured were very low and under the detection limit (0.6 ng N 2 O cm -2 h -1 )

17. NO 3 - N2N2 NH 4 + NO N2ON2O N2ON2O Hole-In-The-Pipe Model Firestone and Davidson 1989 Nitrification Denitrification Ratio of NO / N 2 O fluxes explained by 2 factors: 1. During the period of the study, ammonium predominated over nitrate  probably contributing to higher NOx emissions than N 2 O emissions

18. 2. Additionally, During the study period, WFPS ranged from 15 to 51 %  Nitrification rates are often elevated in aerobic conditions as when WFPS < 60% NO / N 2 O fluxes % WFPS control on N oxide emissions Davidson, 1991

19. Conclusions Application of nitrogen fertilizers resulted in elevated NO emissions compared to background levels in the native cerrado. This increase was a result of pulses after N additions; NO fluxes might be influenced by type of fertilizers and amount of N used; Total N-NO emission for the cultivation period (258 days) was 0.8 kg.ha -1 corresponding to 0.5 % of the N applied as fertilizer (150 kg.ha -1 ).

20. Funding NASA / MCT - Experimento de Grande Escala Biosfera- Atmosfera na Amazônia (LBA) – ND-07 Acknowledgments Pamplona Farm (SLC Company)

21. Thanks Êrika Fernandes, fernandes.eb@gmail.com fernandes.eb@gmail.com Mercedes Bustamante, mercedes@unb.br mercedes@unb.br Alessandra Kozovits Richard Zepp