Variations in C stock. in tropical and subtropical soils of. Segundo Urquiaga, Claudia P. Jantalia Bruno J. R. Alves Robert M.

Transcription

1 Variations in C stock and dghg emissions i in tropical and subtropical soils of Brazil Agrobiologia Rio de Janeiro Segundo Urquiaga, Claudia P. Jantalia Bruno J. R. Alves Robert M. Boddey FAPESP, SP, 16 June 2009

2 The GHG emission i from the soil/plant system to atmosphere started at the beginning of agriculture.

3 Expansion of agricultural frontier: Deforestation

4 In the change from one type of vegetation, or agricultural management system to another there will be a change in the soil C content towards a new equilibrium.

5 The quantity of carbon (organic matter) stored in the soil profile under any vegetation is controlled by three factors: 1. The quantity and quality of plant residues deposited in the soil. Each soil has a limited potential for? C accumulation. 2. Their decomposition rate.

6 Traditional agric lt re Food prod ction depends Traditional agriculture. Food production depends on the natural soil fertility

7 The Cerrados: The last agricultural frontier The green revolution (1960s): Technology based on: Plant breeding. Intensive use of fertilisers

8 Soil tillage contributes to soil erosion and stimulates SOM/SOC losses

9 Reduction in soil organic matter levels after 6 years of conventional planting of soybean in Ferralsols in the western area of Bahia (NE Brazil) 4 > 30% clay ic matte er (%) % < clay < 30% clay < 15% So oil organ Years Silva et al, 1994

10 THE SECOND AGRICULTURAL GREEN REVOLUTION: THE ZERO TILLAGE SYSTEM

11 The great innovation in soil management over the last 15 years in Brazil has been the spread of the practice of zero tillage Million ns hectar res Brazil Cerrados Years Data from the Brazilian Federation of Zero tillage Organisations - FEBRAPDP

12 The Zero Tillage System has now been adopted by FAO as Conservation Agriculture and has three fundamental characteristics: The cover of the soil surface with crop residues (mulch). A preservation of the integrity of the physical structure of the soil by the elimination of tillage. In addition for the system to function well, it is necessary to have a diversity of crops in the rotation to increase nutrient-use use efficiency.

13 Brazil and the Kyoto Protocol Brazil is one of the signatories of the Kyoto protocol ( ), 2012) and although has no obligation to meet targets for reduction in GHG emission, it must: 1) Search for efficient production systems to mitigate GHG emissions. 2) Inform periodically their GHG emissions, through inventories. The IPCC has prepared guidelines to quantify the GHG emission for the inventories (The available information is mainly from temperate regions).

14 Main GHG emitted by agricultural activities: CO 2, N 2 O e CH 4 CO CH 4 CH N N CO O O 2 Soil and native vegetation Soil N-fertiliser Excretas Cattle

15 Research activities at Embrapa Agrobiologia on GHG emission Studies on the impact of agricultural systems (LUC) on the stocks of SOC. Quantification of N 2 O emission rates in various agricultural systems in order to establish emission factors for Brazil.

16 Studies in the field in areas of production of grain, pastures and sugar cane.

17 LUC: Conv. Tillage to Zero tillage Large quantities of crop residues deposited on the soil surface affect mainly the soil C stock of the upper few cm of the soil profile.

18 Carbon sequestration Until recently the consensus held that any conversion from conventional tillage agriculture to zero tillage or full CA would promote soil C accumulation (sequester atmospheric CO 2 ). West and Post (2002) in a meta-survey of 275 comparisons of ZT and CT, concluded on average C was sequestered at 0.57 Mg ha-1 year-1. All these studies sampled the soil to 30 cm depth or less (68 % All these studies sampled the soil to 30 cm depth or less (68 % to 20 cm or less).

19 A great question: In order to evaluate the stock of SOC as consequence of land use change, the IPCC recommendation is restricted to the 0-30 cm layer, to be used in the national inventories. Is this appropriate for Brazilian soils?

20 Soil sampling : The soil profile under cropping systems and natural vegetation, was sampled in small layers until 1 m depth. Bulk density in each soil layer was also evaluated Soil mass content in each layer cm

21 The SOC accumulation or soil C sequestration is finite, and depend on the soil management, history, texture, weather, productivity, etc. Soil C stock Limit Management 2 Management 1 Potential of SOC accumulation after LUC or management Time

22 Site 1 Cerrado (edaphic savanna) Embrapa Cerrados (Planaltina,DF) Site 2 Cerrado (edaphic savanna) Federal University of Uberlândia, MG Site 3 Cerrado (edaphic savanna) Embrapa Western Agriculture (Dourados, MS) Site 4 Semi-deciduous Atlantic forest Embrapa Soybean (Londrina, PR) Site 5 Semi-deciduous id Atlantic ti forest Embrapa Wheat (PassoFundo, RS)

23 Cropping systems. 13yr. experiment Passo Fundo, RS M A M J J A S O N D J F Rotation 1: Wheat/Soybean Wheat Soybean Rotation 2: wheat/soybean-vetch/maize 1º year Wheat Soybean 2º year vetch Maize Rotation 3: wheat/soybean-oats/soybean- vetch/maize Wheat Soybean 1º year 2º year Oats Soybean 3ºyear vetch Maize

24 t ha -1 ) Organic Carbon ( Organic Carbon content in the soil profile under No-tillage and conventional tillage ab ab 0~100cm depth 178 a 161 b 179 a 163 b 171 ab 13 years 100 NT CT NT. CT..NT.CT Forest Wheat/Soybean Wheat/Soybean W/S-Oat/Soybean Vicia/Maize Vicia/Maize Passo Fundo- RS, BRAZIL (Sisti et al, 2004, Soil & Tillage Research 76(1): )

25 In a study on a Ferralsol in southern Brazil C stocks in different depth intervals beneath three crop rotations managed under Zero Tillage (ZT ) or Conventional Tillage (CT) for 13 y Soil C stock (Mg.ha -1 ) Tillage treatment Rotation ZT CT Mean Depth Interval 0-30 cm Difference ZT - CT R1 60.9a a 61.6A R2 64.7a 59.3b 62.0A 5.4 R3 69.6a 60.5b 65.0A 9.1 years Mean 65.0a 60.7b Coef. var. (%) 4.3 Depth Interval cm R1 Wheat/soybean R2 Wheat/soybean Vetch/maize R3 Wheat/soybean R a 161.3b 169.7A 16.9 Oats/soybean -Vetch/maize R a 167.5a 167.7A 0.5 R a 161 3b 169 7A 16 9 R a 162.7b 171.0A 16.7 Mean 175.2a 163.8b Coef. var. (%) Means in the same row followed by the same lower case letter are not significantly different at P< Means in the same column followed by the same upper case letter are not significantly different at P<0.05. (Sisti et al. 2004, Soil Tillage Research 76: 39-58)

26 13 C abundance of soil below all 3 crop rotations under zero or conventional tillage in comparison with that of soil below neighbouring native vegetation (Embrapa Wheat Centre, Passo Fundo, RS).

27 Experiment, 15 years C and N stocks to 100cm under a rotation of flax/soybean -oats/soybean -barley/soybean (6 years) followed by vetch/maize - oats/soybean - barley/soybean (9 years) managed either under ZT or CT (mouldboard plough). (Embrapa Wheat Centre (Embrapa Wheat Centre, Passo Fundo, Rio Grande do Sul)

28 It is becoming increasingly evident that t the quality of crop residues (nitrogen content!!) t!!) plays an important role in the accumulation of soil carbon.

29 C:N Ratio in two different soils under No-tillage, conventional tillage and forest at 2 sites in southern Brazil R 2 = 0,94 Y = 0,5 + 12,37.X (n=420) p<0, Y= -0, ,34.X R 2 = 0,99 P<0,0001 (n=120) Nitrogen (g.kg -1 ) Nitrogen (g.kg -1 ) Passo Fundo: Oxisol Rio Grande do Sul Cambé : Terra Roxa Paraná (Claudia Jantalia Sisti, MSc Thesis 2001)

30 Relationship between Labile organic carbon and Total nitrogen in an oxisol of Cerrado. La abile org ganic c arbon (g.kg g -1 ) g g g Y Y=0.4 = 0, ,45.X X R 2 = 0,97 (n=168; P<0,0001) Total nitrogen (g.kg -1 ) 1 Brasília - DF. Brazil Claudia Jantalia Sisti, MSc Thesis 2001

31 No tillage farming is an important technology to improving soil processes, controlling soil erosion, and reducing tillage costs, and these are sufficient reasons to promote the conversion of plow tillage to no-tillage farming, but the idea that no-tillage would also enhance soil organic carbon sequestration ti as an additional benefit of no-tillage technology needs a careful reexamination. H. Blanco-Canqui & Rattan Lal. SSSAJ, 72 (3): Junho, 2008

32 The N economy by the use of lupins for green manure of maize under notillage at Paraná state (South Brazil) Lupins used in the winter for a summer based soybean-maize cropping system Maize yields growing on a lupin biomass of about 7 to 11 ton DM ha -1, under no-tillage. ton ha Maize after lupins Maize after oats + 80 kg N ha -1 Maize after lupins (no N fertilizer) Maize after oats + 80 kg N ha -1 After lupins After oats + N The drought of the winter 2005 Lupin biomass under 2 ton DM ha / / / /2005 Summer harvests 2005/2006

33 N 2 N 2 N 2 CO CO 2 2 CO 2 CO 2 CO 2 CO kg/ha N ~ 450 kg/ha CO kg/ha N ~ 1 kg N Assuming a 2 O ~ 500 kg/ha CO 2 fertilizer-use efficiency of 50%, and that 25% of the applied N is N 2 O immobilized as soil organic matter. NH + 4 NO kg/ha N ~ 1100 kg/ha CO 2 C-SOM

34 Carbon sequestration in soils of the Cerrado Region (CPAC-Brasília)

35 Cropping sequence in the experimental area. 18 years Year Crop Year Crop 1979/80 Rice 1989/90 Fallow 1980/81 Rice 1990/91 Fallow 1981/82 Soybean 1991/92 Soybean 1982/83 Pigeon pea 1992/93 Soybean - Maize 1983/84 Fallow 1993/94 Soybean - Maize 1984/85 Fallow 1994/95 Rice 1985/86 Fallow 1995/96 Soybean 1986/87 Soybean 1996/97 Maize 1987/88 Soybean 1997/98 Soybean 1988/89 Soybean - Maize 1998/99 Soybean

36 Carbon content (M Mg.ha-1) Organic carbon and nitrogen content in the soil profile under 4 different tillage systems and natural vegetation Inert carbon Charcoal C }Labile carbon C4 Nit trogen con ntent (Mg.h ha-1) Zero-tillage Disk plow 1 time.yr Disk plow 2 times.yr -1 8,2 Cerrado 10 C 4 18 years 4 Means of 3 profiles. 0 Zero-tillage Disk plow 1 time.yr -1 Disk plow 2 times.yr -1 Cerrado Jantalia et al. (2007 Soil & Tillage Research 95:

37 Our team at Embrapa Agrobiologia and others at the Federal University of Rio Grande do Sul have now made 14 comparisons of C accumulation under zero till experiments on Ferralsols in southern Brazil sampled to either 30 or 100 cm depth. On average evaluation of soil C stocks to only 30 cm depth compared to 100 cm underestimated C sequestration by 59%. rate Mg/h ha/yr cm) C seque estration ( Wheat/soybean Rotations with winter or intercropped legumes 0.0 C 100 = (1.59 x C 30 ) Oats/maize Boddey et al, Global Change Biology (in press) r 2 = C sequestration rate Mg/ha/yr (0-30 cm)

38 Brachiaria Pastures in Brazil Cerrado region: 40 to 60 Million ha (M ha) Coastal Atlantic forest region: >20 M ha Amazon region: ~20 M ha TOTAL: > 90 M ha (~10 % of the area of Brazil)

39 Atlantic forest region Animal Husbandry Station of CEPLAC in Itabela, Bahia

40 Carbon content of soils under 9-year old grass-only Brachiaria humidicola, and mixed B. humidicola/desmodium ovalifolium pastures and adjacent secondary forest and a degraded pasture in the Atlantic forest region (Itabela, S. Bahia). Degraded d Secondary Depth Grass-only Legume/grass pasture Forest cm Mg C/layer ` Total Means of three stocking rates (2, 3 e 4 head. ha -1 ) Tarré et al. (2001 Plant and Soil 234:

41 13 C natural abundance of soil under forest and of pasture B. humidicola in monoculture or mixed with D. ovalifolium (1997). Depth (cm) Pasture monoculture Pasture mixed (B + D) Forest C PDB Tarré et al, 2001

42 Contribution of biological nitrogen Fixation to graminaceous crops (Dobereiner & Day, 1959)

43 Cerrado Response of degraded pasture of Brachiaria spp. to the application of P and N fertilisers. Means of 6 replicates. B. brizantha 4 años B. brizantha 9 años Treatment Dry matter accumulation (g m -2 ) Fazenda Campo Fazenda Barreirão Grande Cachoeira minus N - P 189,0 c 371,5 b 66,7 c +P 190,3 c 338,33 b 64,1 c Mean 189,7 B 354,9 B 65,4 B with N -P 286,3 b 542,8 a 143,7 b +P 513,8 a 663,8 a 210,2 a Mean 400,1 A 603,3 A 177,0 A C.V. % 11,3 13,7 19,0

44 Associated pasture of B. ruziziensis:s. guianensis cv Mineirão, Uberlândia MG. Brachiaria Brach/Stylosanthes S. guianensis avoids the weight loss of cattle during the dry season in the Cerrado region

45 3 Stock of SOC (Mg/ha) in the soil profile (0-100 cm) under grass pasture at 4 different experimental sites of Cerrado Chapadão do Sul MS (Clay = 11 %) Nat. vegetation = 34,3 Pasture: Productive = 38,2 Degraded = 29,7 Luz, MG (Clay = 77 %) Nat. Vegetation = 117,0 Pasture: Productive = 144,6 Degraded = 138,0 Itaporã, MS Penápolis, SP (Clay = 46 %) (Clay = 16 %) Nat. vegetation = 83,3 Pasture: Productive = 95,4 Degraded = 85,1 Nat. vegetation= 55,6 Pasture: Productive = 62,0 Degraded = 60,5

46 THE THIRD AGRICULTURAL REVOLUTION: INTEGRATION CROPPING/PASTURE Improves physical, chemical and biological soil properties, including accumulation of SOC. Diminishes problems with weeds, pests and plant pathogens and increases nutrient-use efficiency. Increases cereal and forage yields. Diversification of agricultural activities decreases economical risk.

47 Brachiaria 59 days after the maize harvest

48 C orgânico de el suelo (g kg -1 ) Period of annual Period of perennial crops pasture Años Díaz-Zorita et al. (1997) Matéria org gânica (%) 5 Rotação contínua de soja/milho Pasto astodeposde depois lavoura oua Lavoura depois de pasto Anos Sousa, et al., 1997

49 Changes in the soil C stock of Pastures, ley-cropping and cropping under ZT in the Cerrado region Experimental Site Brasília-DF

50 180 0 to 100cm C and N accumulation under eight different pasture/cropping systems after 11 years in the Cerrado region (Embrapa Cerrados, Planaltina, DF). Jantalia et al., 2006 Tota al carbon (Mg ha -1 ) Total nit trogen (M Mg ha -1 ) # 125c # 7.7c 145a 144a 147a 8.9a 8.4ab 8.5ab 138ab 8.2bc 143ab130bc 139ab139ab 8.5ab 7.6c 8.2bc 8.0bc F1 F2 F1 F2 CT ZT CT ZT Cerrado Grass-alone Mixed grass- Ley Continuous Pasture legume pasture cropping cropping

51 The soil C accumulation is finite. N 2 O Cumulative New equilibrium u Soil organic carbon Time

52 Emission factor of the IPCC for GHG emission inventories Emission factor = Qty. N-N 2 O emitted/qty. applied N. Ex: Direct emission of N-N 2 O derived from fertilizers and crop residues = 1% N 2 O emission from cattle excreta = 2% These factors are relevant for Brazilian conditions?

53 Survey of N 2 O emission rate from Brazilian agriculture: Studies in development and programmed by Embrapa Agrobiologia Flooded rice Sugar cane Evaluation of N sources and Residues High land rice, ZT Irrigated maize and bean, ZT Integration croppingpasture Pig slurry Pig slurry and chicken manure Maize and soybean crops Pasture and cattle excreta Residues Sugar cane Forest, eucalyptus and pasture Crop rotation (maize, soybean and wheat, ZT and CT) Crop rotation (soybean and wheat, ZT and CT)

54 How N 2 O emission fluxes are being measured? Static closed chamber

55 N 2 O emission rate from a Ferralsol planted to maize under zero and conventional tillage. Londrina-PR kg N 40 kg N Preparo Conventional Convencional tillage Zero Plantio eot tillage Direto g N m-2 h /11/05 29/11/05 9/12/05 19/12/05 29/12/05 8/1/06 18/1/ /1/06 7/2/06 17/2/06 27/2/06 9/3/06 19/3/06 29/3/ kg ha -1, N-urea

56 Thus, working in three different agroecosystems of Brazilian agriculture, the emission factor of N 2 O (0.16%) for grain production averages one sixth of the value proposed by the IPCC (1%).

57 The very low values of N 2 O emission rates in Ferralsols (Latossolos) are closely l associated with the high h drainage rate of these soils and with the high evapo-transpiration rate in tropical regions Soils which are flooded for less than one day do not show enough decrease in redox potential to reduce significantly the NO - 3 content (Sposito, 1989). Water infiltration in an Oxisol (Latossolo Vermelho), Sto Antonio de Goiás, GO.

58 N 2 O emissions derived from cattle excreta in pastures. IPCC: 2% of N-excreta is lost as N 2O.

59 The sugar cane crop Variation V i of soil C stocks 60% 40% Studies from the sugar cane areas of the states of Pernambuco and Espírito Santo show that green cane harvesting contributes littlel to increase the soil C stocks.

60 Alcon Atlantic Forest region Argissolo (Conceição da Barra, ES) Stock of C in the soil under Brachiaria pasture and Sugar cane cultivation 22 years after deforestation. Campos et al, 2003

61 Private Sugar cane farm: Alcon Conceição da Barra, RJ Schematic summarizing the treatments applied. Native vegetation (Forest) Native vegetation (Forest) Undisturbed soil properties Pasture (10yr) Pasture (22yr) Sugar cane (12yr) Native vegetation (Forest) Forest Sugar cane Pasture (Brachiaria)

62 13 C natural abundance of soil to a depth of 100 cm under Sugar cane, Native vegetation and B. humidicola pasture Depth (cm) Sugar Cane Native vegetation Pasture C Campos et al, 2003

63 Roots distribution in the soil profile of a sugar cane plant in an Argissolo (Typic Hapludult) 20 cm Sugar-cane variety: RB Age: 3 th ratoon crop (4.5 years). Usina Santa Cruz, Campos dos Goytacazes, RJ

64 (Mg ha -1 ) cane yield Mean Impact of change from burned cane to a a a a green-cane harvesting Usina Cruangi, Timbauba, PE* b a a a Cane burned Trash conserved a a b a b a b Rainfall (mm) Year *Resende et al., 2006, Plant Soil 281: a a a b a b a b a b a Rainfall (mm) Increase in soil C stocks on change to green cane harvesting = ~300 kg C ha -1 yr -1 over 16 years

65 Comparison of emissions of GHGs from the manual harvesting of burned cane with the mechanized harvest of green (unburned) cane Emission source Emission CH 4 N 2 O Fossil CO 2 Total (g ha -1 ) (g ha -1 ) (kg ha -1 ) (kg eq.co -1 2 ha ) Manual harvest, burned cane 1. Cane burning 28,350 a 735 b - 1, Manual labour and transport Mechanized harvest, green cane TOTAL Fuel for harvester (diesel) GHGs for machine fabrication Manual labour and transport Mineralization of residues TOTAL 445 a Based on IPCC (2006) methodology for the burning of 13.1 Mg ha -1 of agricultural residues at 80 % efficiency (2.7 kg CH 4 Mg -1 burned). b Based on IPCC (2006) methodology for 13.1 Mg ha-1 of sugarcane residues (0.07 kg N 2 O Mg -1 burned) At present ~60% of cane is burned for manual harvest. If burning is completely replaced by mechanized green cane harvesting the mitigation of GHG emissions increases from 80 to 87%

66 Impact of GHG emissions on conversion of land to sugarcane production 1 ha of sugarcane produces today ~6,500 Litres of ethanol which will fuel a journey by a pickup fuelled by 2.4 L flexfuel motor approximately 46,800 km. This distance requires 4,500 L if pure gasoline is used. The total emission of GHGs (N 2 O, CH 4 & fossil CO 2 )bythe 6,500 L of ethanol = 3,229 kg CO 2 eq. The total emission of GHGs by 4,500 L of pure gasoline = 16,427 kg CO 2 eq. Thus the total avoided emissions ( Carbon sequestration ) of 1 ha of sugarcane used for bioethanol production = 13,200 kg CO -1 (36MgCha ha (3.6 ) year.

67 Impact on GHG emissions of conversion of land to sugarcane production A low productivity pasture grazed at 0.7 animal units (AU) ha -1 is estimated to emit 2,840 kg CO 2 eq ha -1 year -1 (principally CH 4 from rumen and N 2 O from urine etc.). If there is no change in soil C stocks the change in GHG emissions is from pasture to sugar cane 2,840 to 3,300 kg CO 2 eq. For the change from soybean/ maize cropping to sugarcane the extra GHG emission becomes 3,300-1,720 = 1,580 kg CO 2 eq. When land under crops or pastures is planted to sugarcane the extra GHG emissions are unlikely to exceed 1.5 Mg CO 2 eq year, which is very minor compared to the mitigation (>13 Mg ha -1 yr -1 ) promoted by bioethanol production.

68 Thank you very much!