Comparative study of chemical and biological diversity of soil of two rice fields subjected to organic and conventional farming

Transcription

1 Comparative study of chemical and biological diversity of soil of two rice fields subjected to organic and conventional farming Romani M. 1, Beltarre G. 1, Miniotti E. 1,2 and Said-Pullicino D. 2 1 Rice Research Center, Ente Nazionale Risi, Pavia, Italy. m.romani@enterisi.it 2 Soil Biogeochemistry Team, Rice Agroecosystem & Environmental Reserch Group, University of Turin, Italy.

2 Organic rice in Italy Total ha Rice surface Organic ha ha in conversion Percent of organic cereal surface Corn Rice Wheat Barley Oat Rye Triticale Others Data: SINAB 2010 Comparative study of the Chemical and biological diversityof soil

3 Key elements Weed control - Grasses in dry seeded - Aquatic weeds and Echinochloa species (white types) in water seeded Diseases control - Panicle blast Soil fertility - Availability of N-organic fertilizers

4 Materials and Methods 2 farms in Italian rice area near Pavia (Italy): conventional VS organic farming Surface: 24,3 and 45,8 ha Climate: Temperate, with 465 mm/y 17,6 C during the cropping season Soils: Typic Hapludalf, coarse-loamy, mixed, mesic (Soil Survey Staff, 1992). Soil samples in 2002 and 2007 Crops: Oryza sativa L. cv. Baldo Crop management: Dry seeding and flooding at tillering stage

5 Materials and Methods Conventional farm 24,3 ha High-input continuous rice monocropping Fertilization 15:5:20 N:P:K mineral compound fertilizer (375 kg/ha) before seeding 150 kg/ha of Diammonium phosphate before flooding Herbicide Pendimetalin and oxadiazon at pre-emergence Propanil and etoxysulfuron at post emergence Organic farm 45,8 ha 5 years crop rotation: rice-rice-soybean-corn-winter cereal *2 years of organic management before starting the experiment Fertilization Cattle manure 1,9:0,7:1,5 N:P:K Poultry litter 3,9:1,8 N:P Horn and hoofs 14% N and , 300, 420 kg/ha respectively K-Mg sulphate 270 kg/ha

6 Materials and Methods Sampling scheme

7 Results Paddy rice yields during t/ha Conventional t/ha Organic Average: 5,3 t/ha Average: 5,8 t/ha

8 Results Chemical and phisical properties of Conventional and Organic fields for 2002 and 2007 sampling Conv Conv Organic 2002 Organic 2007 ph (H 2 O) 6,4 6,5 5,7 6,5 ph (KCl) 5,5 5,7 4,5 5,6 Conductivity (1:2) μs cm C 164,3 216,3 61,8 175,8 Total N 1,6 1,5 0,9 1,1 P 2 O 5 (Olsen) ppm 154,5 140,7 108,6 140,2 P 2 O 5 (Bray Kurtz) ppm 272,5 128,8 160,8 110,5 C.E.C. cmol (+) /Kg 10,0 11,1 7,4 7,9 Ca 2+ ppm 1379,3 1354,8 686,5 977,2 Mg 2+ ppm 143,0 111,5 95,9 104,4 K + ppm 122,6 194,7 81,0 242,0 Na + ppm 24,8 60,3 10,6 64,7 Fe-DTPA ppm 107,8 57,3 121,5 68,4 Mn-DTPA ppm 2,4 1,6 3,8 5,9 Cu-DTPA ppm 3,6 3,5 3,5 3,4 Zn-DTPA ppm 1,7 1,1 1,4 2,3 B ppm 0,6 n.d. 0,5 n.d. Sand (>50 µm) % 77,1 75,6 79,1 77,8 Silt (2-50 µm) % 20,3 20,9 17,4 16,7 Clay (<2 µm) % 2,0 3,5 3,5 5,5

9 Results Total Organic carbon Treatment Year TOC mg C kg -1 Conventional , ,0 Organic , ,4

10 Results Characterization of organic fraction in the soils TOC = Total Organic Carbon TEC = Total extractable Carbon HA+FA = Humic and Fulvic Acid Carbon NH = Non- Humic Carbon HI = Humification index DH = Degree of Humification HR = Humification Ratio

11 Results Characterization of organic fraction in the soils Treatment Year TEC HA+FA NH HI DH HR mg C kg -1 % % Conventional ,4 6,8 3,6 0,5 65,8 43, ,4 5,1 2,3 0,5 69,1 36,9 Organic ,7 3,1 2,7 0,9 53,3 34, ,2 3,2 2,0 0,6 61,3 30,8 TOC = Total Organic Carbon TEC = Total extractable Carbon HA+FA = Humic and Fulvic Acid Carbon NH = Non- Humic Carbon HI = Humification index DH = Degree of Humification HR = Humification Ratio

12 Organic Conventional Results 300 mg/kg October 2002 (mg C-CO 2 /kg of soil) 300 mg/kg October 2007 (mg C-CO 2 /kg of soil) days days

13 Organic Conventional Results 300 mg/kg October 2002 (mg C-CO 2 /kg of soil) 300 mg/kg October 2007 (mg C-CO 2 /kg of soil) days days October 2002 (mg C-CO 2 /g Corg) October 2007 (mg C-CO 2 /g Corg) 30 mg/g 30 mg/g days days

14 Results Microbic Carbon content Respiratory quotients (at 7 days) Treatment Year C mic mg C g -1 Treatment Year RQ mg C-CO 2 /mg C mic h -1 Conventional , ,2 Organic , ,2 Conventional , ,14 Organic , ,22

15 Results Mycorrhizal colonization Roots infection of O. sativa F M a A % Conventional Organic 2,45 1,00 46,99 0,47 F: Indicates the percentage of root segments showing internal colonization; M: Indicates the average percentage colonization of roots segments; A: Indicates the presence of arbuscules in the whole root apparatus; a: Indicates the average presence of arbuscules within the infected areas.

16 Discussion and Conclusions 7 years of organic management lead to an increase in TOC This result is of significant importance particularly considering the aerobic conditions of the field for 3 over 5 years of crop rotation and the sandy soil texture The short period of organic management was probably not sufficient to appreciate variation in the more stabilized OM content Biological parameters were positively influenced by organic management In the Italian scenario dominated by continuous rice cropping and little zootechnic activity, organic management could represent a valid alternative leading to an adequate increase in soil fertility particularly in areas characterized by high inputs and low yields.

17 Thanks for your attention Comparative study of the Chemical and biological density of soil