SOC and biodiversity dynamics under DMC systems: Enhancing soil potentialities and production of ecosystem services Examples from Laos and Brazil F. Tivet (CIRAD), H. Tran Quoc (CIRAD), C. Khamxaykhay (DALAM/NCAC), JCM Sá (UEPG), P. Lienhard (CIRAD), J. Boyer (CIRAD), P. Tantachasatid (Kasetsart), K. Panyasiri (MAF), S. Boulakia (CIRAD), L. Hok (RUA), R. Kong (GDA), A. Khamhoung (DALaM), L. Séguy (Agroecoriz) THE 4 TH INTERNATIONAL CONSERVATION AGRICULTURE CONFERENCE IN SOUTHEAST ASIA

Objective to evaluate for a range of no-till systems the changes on SOC, soil physical properties and biodiversity … … as a tool to improve cropping systems design and adjustment

Strong connection with Thai market Intensive cash crops production (maize and cassava) Plow-based tillage, pesticides, hybrid seeds and chemical fertilizers Yields decrease drastically + increasing production costs High environmental impacts Southern Xayabury/Laos: context and drivers of changes  3,000 km 2

Temporal changes in SOC stock (0-30 cm) Shifting cultivation + ~15 years under CT Native SOC Stock (Mg C ha -1 ) Conversion to agriculture Temporal changes in SOC stock  140 Mg C ha -1 t0t0 Since the conversion: ~ 50% decrease in SOC stock Mg C ha -1 Native vegetation Basic igneous rocks, gabbro, dolerite 480 g clay kg Mg C ha -1  80 Mg C ha -1 Unfolded sandstone and claystone 380 g clay kg -1 Shifting cultivation and less intensive ploughing THE 4 TH INTERNATIONAL CONSERVATION AGRICULTURE CONFERENCE IN SOUTHEAST ASIA

3 cropping systems Maize monoculture (  5.0 Mg DM ha -1 ) Maize (5 to 6) / Rice bean (3 to 5) Maize (5 to 6) + B. ruziziensis (4 to 6) / Rice bean (3 to 5) 44 farmer groups 1630 households 2000 ha 180 ha

Density and diversity of soil macrofauna Main differences on earthworm, ants, termites, millipedes (Diplopoda), and beetle (Coleoptera) From Boyer J. (CIRAD) and Tantachasatid P. (Kasetsart University) THE 4 TH INTERNATIONAL CONSERVATION AGRICULTURE CONFERENCE IN SOUTHEAST ASIA

Infiltration rate (cm h -1, 0-30 cm depth) Maize monoculture (  5.0 Mg DM ha -1 ) Maize (5 to 6) / Rice bean (3 to 5)B. ruziziensis THE 4 TH INTERNATIONAL CONSERVATION AGRICULTURE CONFERENCE IN SOUTHEAST ASIA

Changes in soil physical properties MaizeMaize - ricebeanM + ruzi - ricebean Total water retention (mm ha -1, 30 cm depth) CT NT Gain+20 mm+27 mm+12 mm+17 mm % of macroaggregates > 8 mm (0-10 cm, wet sieving) CT NT THE 4 TH INTERNATIONAL CONSERVATION AGRICULTURE CONFERENCE IN SOUTHEAST ASIA CT-M NT-MRV Disruptive effect of ploughing  SOC losses Enhancing macroaggregation  SOC protection and accumulation

THE 4 TH INTERNATIONAL CONSERVATION AGRICULTURE CONFERENCE IN SOUTHEAST ASIA CEC = 1.48 SOC r 2 = 0.83

Gentle slope < 5% Flat land Steep slope > 15% Changes in SOC (0-30 cm, 6-yrs period) *** * *** * Mean ± Std. Error, n = 4 Eq. Soil-mass depth basis  SOC: 0.2 to 3.7 Mg C ha -1 yr -1 THE 4 TH INTERNATIONAL CONSERVATION AGRICULTURE CONFERENCE IN SOUTHEAST ASIA

What are the main gains (basaltic soils)? NT vs. CT  10,000 ha FaunaBiomass (kg ha -1 ) ,280 Mg Diversity (taxa ha -1 )+2.3 Density (Ind m -2 )+801 THE 4 TH INTERNATIONAL CONSERVATION AGRICULTURE CONFERENCE IN SOUTHEAST ASIA Infiltration rate (cm h -1 )+26.3 Total water retention (mm ha -1 ) m 3 Aggregation (mean diameter, mm) +4.4 CEC (cmol ha -1, 30 cm depth)+0.5 to 8.7 cmol ha cmol ha ,000 cmol yr -1 SOC0.2 to 3.7 Mg ha -1 yr Mg C ha -1 yr -1 +5,400 Mg C yr -1

CT = Conventional Tillage NT = No-Tillage Results > Differences between maize mono cropping with tillage and no-tillage are not significant > In a « Maize - Rice bean » rotation, maize yields -without fertilizer- can be increased from 25% to 50% (in comparison to maize monoculture under CT) > Maize yields – without fertilizer - with rice bean mulch are close to optimum maize yield

Yields – Basaltic soils CT = Conventional Tillage NT = No-Tillage 4 years average maize yield ( )

sorghum + Brachiaria + pigeon pea Sunflower + Crotalaria sorghum + Brachiaria + pigeon pea Summer wet Soybean of high productivity (>4.0 tons/ha) Finger millet + Crotalaria millet + Brachiaria ruziziensis Winter hot and dry Maize + Brachiaria + pigeon pea 15 tons of biomass/ha TROPICAL CERRADO REGION From L. Séguy, S. Bouzinac and partners

SUBTROPICAL AGROECOSYSTEMS Fazenda Agripastos, Manoel Henrique Pereira

Changes in C content in aggregate size classes Land use Aggregate size classes (mm)C input C content (g C kg -1 )Mg C ha -1 yr -1 Tropical NV CT NT Subtropical NV CT NT SOC is more labile and less processed under NT than under CT, suggesting that spatial inaccessibility within aggregates plays a major role in enhancing SOC accumulation. ‘free’ and labile SOC: plant, fauna and microflora nutrition, and structural stability. Tivet et al., Soil and tillage research, 126: THE 4 TH INTERNATIONAL CONSERVATION AGRICULTURE CONFERENCE IN SOUTHEAST ASIA 8 yrs 29 yrs

THE 4 TH INTERNATIONAL CONSERVATION AGRICULTURE CONFERENCE IN SOUTHEAST ASIA SUBTROPICAL AGROECOSYSTEM … higher catabolic demand under NT Bigger « engine » under NV but … … different groups of bacteria and functions (see Lienhard et al., ASD 33: ) Sá et al., Forthcoming

THE 4 TH INTERNATIONAL CONSERVATION AGRICULTURE CONFERENCE IN SOUTHEAST ASIA SUBTROPICAL AGROECOSYSTEM Sá et al., Soil Science Society of America Journal. 65: Mg C ha -1 and Mg N ha -1 under NT22 Higher SOC and N stocks under NT  SOC: 0.86 Mg C ha -1 yr -1

t1t1 15 years continuous soybean under CT Native t2t2 SOC Stock (Mg ha -1 ) 71.4 Mg C ha Mg C ha -1 Conversion to agriculture Temporal changes in SOC stock CT 55.6 Mg ha -1 Forest 75.7 Mg ha -1 8 years under CT or NT NT systems C input: 6.84 to 8.38 Mg C ha -1 yr -1 t0t0 Temporal changes in SOC stocks (0-40 cm depth) - Tropical agroecosystem Tivet et al., Geoderma : Sá J.C.M., Séguy L., et al., Land Degradation & Development: DOI: /ldr  SOC: 0.7 to 2.0 Mg C ha -1 yr -1

Cambodia – Bos Knor station  PhD. Lyda Hok (RUA), partnership GDA - CIRAD (PAMPA), North Carolina A&T (SANREM) and UEPG (Brazil)  3 experiments (rice, soybean and cassava), randomized block design (60 plots of 300 m 2 )  4 cropping systems selected per experiment: SOC dynamics to 1-m depth + soil microbial abundance and diversity

Soil biomass and diversity Continuous fresh C flux (above + rhizodeposition) C cycling Nutrients availability (N, P, S), pests management? Conclusions THE 4 TH INTERNATIONAL CONSERVATION AGRICULTURE CONFERENCE IN SOUTHEAST ASIA Nutrient cycling Dynamics Availability N and P Carbon dynamics Turnover Stabilization Soil structure Aggregation Porosity Water retention Habitat provision Pest management Soil structure CEC

22 Thank for your attention Rice direct seeded on Stylosanthes guianensis residues – Cambodia (PADAC – GDA) THE 4 TH INTERNATIONAL CONSERVATION AGRICULTURE CONFERENCE IN SOUTHEAST ASIA