changes in soil aggregation, soil water
Transcription
changes in soil aggregation, soil water
Document obtenu sur le site http://Agroecologie.cirad.fr CHANGES IN SOIL AGGREGATION, SOIL WATER-HOLDING CAPACITY AND SOIL BIOLOGICAL ACTIVITY UNDER NO-TILL SYSTEMS AND CROPPING SEQUENCES IN THE LAO PDR By Florent Tivet, Hoà Tran Quoc, Johnny Boyer, Chansamone Inthavong, Sompasith Senephansiri, Laty Keodouangsy, Thisadee Chounlamountry, Chanthasone Khamxaykhay, Khamkeo Panyasiri, Lucien Séguy Document obtenu sur le site http://Agroecologie.cirad.fr CONTENT 1. Brief presentation of the context in the Southern Xayabury 2. Materials and methods 3. Results 4. Discussion and Prospective Rising pressure on the natural environment and on farming systems… Document obtenu sur le site http://Agroecologie.cirad.fr … to increase productivity to generate marketable commodities Document obtenu sur le site http://Agroecologie.cirad.fr Marked land degradation and depletion of natural resources ORIGINAL AND CURRENT SOC – SOUTHERN XAYABURY Document obtenu sur le site http://Agroecologie.cirad.fr Natural ecosystem SOM natural (%) SOC natural (%) Stock C (ton/ha) -3 Bulk density (Mg.m ) Converting forest + 15 years of ploughing SOM current (%) SOC current (%) Stock C (ton/ha) -3 Bulk density (Mg.m ) Total loss of carbon (ton/ha) 0-10 cm 7.99 4.64 48.67 1.05 10-20 cm 5.66 3.29 37.78 1.15 2.71 1.57 20.44 1.30 3.00 1.74 23.19 1.33 0-20 cm 86.45 43.64 42.81 SOIL PHYSICAL PROPERTIES UNDER CONVENTIONAL PRACTICES Document obtenu sur le site http://Agroecologie.cirad.fr St e, op sl p ge ee tilla e, op sl e tle ag en ill G t Soil is disrupted by tillage, high frequency of small macro aggregates is observed. Increasing mineralization rate and loss of SOC by runoff. Document obtenu sur le site http://Agroecologie.cirad.fr OBJECTIVE ‘This study set out to analyse soil aggregation, soil water-holding capacity and soil biological activity under tillage and no-tillage conditions in relation to the cropping sequence’ Document obtenu sur le site http://Agroecologie.cirad.fr CONTENT 1. Brief presentation of the context in the Southern xayabury 2. Materials and methods 3. Results 4. Discussion and Prospective Document obtenu sur le site http://Agroecologie.cirad.fr Maize monoculture (4.8 t.ha-1 DM) THREE CROPPING SYSTEMS Maize (5.1) / Rice bean (3.1) Maize (5.2) + B. ruziziensis (4.0) / Rice bean (3.1) Document obtenu sur le site http://Agroecologie.cirad.fr SOIL AGGREGATION Water stable aggregates: aggregate size fraction through the wet sieving method (Yoder, 1936). Soil samples are collected at 0–10, 10-20 and 20–30 cm depth (6 replicates per depth). The samples are moistened by capillarity, by placing them on a filter paper at the top sieve. The water volume is then raised inside the water tank to wet the filter paper and, consequently the soil. Each test uses six sieves of 8, 4, 2, 1, 0.5 and 0.25 mm. The wet sieving process for 10 minutes. The aggregates retained in each sieve are weighed 24h at 105°C. Document obtenu sur le site http://Agroecologie.cirad.fr SOIL WATER HOLDING CAPACITY 6 Soil samples are collected at 0–10, 10-20 and 20–30 cm depth to measure bulk density. The samples are moistened by capillarity until full capacity and then weighted. 7 Weight of dry soil is recorded after drying the sample for 24h at 105°C. Document obtenu sur le site http://Agroecologie.cirad.fr SOIL MACRO FAUNA Fauna sampling is done on square of 25cmx25cm on the top soil and at 3 depths: 0-10, 10-20 and 20-30 cm. Minimum of 9 repetitions are required for each system. Total fauna is collected on each depth using pliers and put into alcohol for identification in laboratory. Fauna identification and accounting is done under binocular glass. Fauna weight is done for each treatment at every depth and for each specie. Document obtenu sur le site http://Agroecologie.cirad.fr CONTENT 1. Brief presentation of the context in the Southern xayabury 2. Materials and methods 3. Results 4. Discussion and Prospective Frequency (%) 0 10 20 30 40 Forest Soil layers (cm) 0-10 10-20 20-30 5.6 mm 5.3 mm 8 mm 4 mm 2 mm 1 mm 0.5 mm 0.25 mm 5.1 mm mean diameter of water-stable aggregate SOIL AGGREGATION Document obtenu sur le site http://Agroecologie.cirad.fr Frequency (%) Document obtenu sur le site http://Agroecologie.cirad.fr 0 10 20 30 40 Soil layers (cm) Tillage 0-10 3.0 mm 10-20 4.6 mm 20-30 4.3 mm > 8 mm > 4 mm > 2 mm > 1 mm > 0.5 mm > 0.25 mm Frequency (%) 0 10 20 30 40 SCV Soil layers (cm) 0-10 4.7 mm 10-20 5.0 mm 20-30 4.2 mm Maize monoculture, DM = 4.8 t.ha-1 Frequency (%) Document obtenu sur le site http://Agroecologie.cirad.fr 0 10 20 30 40 Soil layers (cm) Tillage 0-10 3.3 mm 10-20 3.6 mm 20-30 3.8 mm > 8 mm > 4 mm > 2 mm > 1 mm > 0.5 mm > 0.25 mm Frequency (%) 0 10 20 30 40 Soil layers (cm) SCV 0-10 4.9 mm 10-20 4.0 mm 20-30 3.8 mm Maize (DM = 5.1 t.ha-1) / Rice bean (DM = 3.1 t.ha-1) Frequency (%) Document obtenu sur le site http://Agroecologie.cirad.fr 0 10 20 30 40 Soil layers (cm) Tillage 0-10 3.6 mm 10-20 3.7 mm 3.4 mm 20-30 > 8 mm > 4 mm > 2 mm > 1 mm > 0.5 mm > 0.25 mm Frequency (%) 0 10 20 30 40 SCV Soil layers (cm) 0-10 6.0 mm 10-20 5.0 mm 20-30 4.8 mm Maize (DM = 5.2 t.ha-1) + B. ruziziensis (4 t.ha-1) / Rice bean (3.2 t.ha-1) Document obtenu sur le site http://Agroecologie.cirad.fr The temporary (roots hairs and hyphae) and transient (polysaccharides) binding agents are the most important aggregation components. Frequency (%) 0 10 20 30 40 50 Soil layers (cm) Brachiaria ruziziensis 0-10 7.4 mm 10-20 7.2 mm 20-30 5.2 mm > > > > > > 8 mm 4 mm 2 mm 1 mm 0.5 mm 0.25 mm Soil aggregation under [No-till and cropping sequence maize + B. ruziziensis – rice bean] showed results close to the natural ecosystem. Land preparation Tillage No-till Tillage No-till Tillage Cropping sequence maize monoculture Water Stable Aggregate (mm) 0-10 cm c 4.6 b 5.0 c 3.6 b 4.0 c 3.7 a 3.0 4.7 maize - rice bean 3.3 4.9 maize + B. ruziziensis - rice bean 10-20 cm 3.6 20-30 cm ab 4.3 abc a 4.2 c 3.8 bc 3.8 c 3.4 a abc bc bc c ab No-till 6.0 5.0 4.8 Forest 5.6a 5.3a 5.1a SOIL AGGREGATION Document obtenu sur le site http://Agroecologie.cirad.fr Document obtenu sur le site http://Agroecologie.cirad.fr SOIL AGGREGATION DMC maize + B. ruziziensis – rice bean High frequency of big macro aggregates. Enhanced soil structure, increase soil water holding capacity and protect soil organic carbon (oxidation reduction). Soil sensitivity to erosion decreases due to soil cohesion improvement. Macro aggregation (and pattern of aggregate size) is linked to continuous C flux (dry matter/residue input) and enhancement of soil biological activity Document obtenu sur le site http://Agroecologie.cirad.fr SOIL AGGREGATION e, op sl ng p hi ee ug St plo e, op sl ing tle gh en u G plo Soil disrupted by tillage + ze i s ai s m ien n C iz ea M z b D . ru ice B –r Aggreg ation pr ocess u nder no -till and sequen croppin ce. g Document obtenu sur le site http://Agroecologie.cirad.fr “The macroaggregation is the main way to protect the C released from the crop residues decomposition and stimulate the interactions among soil chemical, physical and biological attributes” SOIL WATER HOLDING CAPACITY Document obtenu sur le site http://Agroecologie.cirad.fr 65 Soil water retention (mm H2O, 0-10 cm) bc c ab bc a 60 c a +8.6 +6.6 55 +7.1 50 45 40 35 30 25 re Fo e- iz Ma st e Ric b n ea ize Ma - CV e Ric be S an i- ruz + e iz Ma CV e Ric b n ea i- iz Ma ruz + e CV e Ric be S an CV ize Ma CV S ize a M CV SOIL WATER HOLDING CAPACITY Document obtenu sur le site http://Agroecologie.cirad.fr 160 Soil water retention (mm H2O, 0-30 cm) bcd cd ab 150 abc +9.0 a d +6.2 ab +10.4 140 130 120 110 100 90 re Fo iz Ma e st eb n ea ic -R e- iz Ma CV e Ric be S an i iz Ma ruz + e CV eb ic -R e iz Ma n ea i- uz +r CV e Ric be S an CV ize Ma CV S ize a M CV Document obtenu sur le site http://Agroecologie.cirad.fr SOIL MACRO FAUNA ACTIVITY 2500 CT No-till 17 17 Individual (m-2) 2000 14 1500 17 18 1000 14 16 10 500 12 12 0 Mo c no iz ma e r u ult e ize Ma b ice R - ea n eb Ric e Ric ea a be iz Ma n n aiz -M e B e+ iz Ma . ru B e+ ie ziz . ru ns is ie ziz ns is b ice R - ea n Document obtenu sur le site http://Agroecologie.cirad.fr SOIL MACRO FAUNA ACTIVITY 30 CT No-till Biomass (g.m-2) 25 20 15 10 5 0 n Mo oc ma e r u ult ize iz Ma Ric e e eb an Ric Ric e eb e eb an an aiz -M aiz -M e e+ ru B. ize Ma +B ien ziz sis ziz . ru ic ien -R sis e eb an ORIGINAL AND CURRENT SOC – SOUTHERN XAYABURY Document obtenu sur le site http://Agroecologie.cirad.fr Between 2001 and 2007 SOM 2001 (%) SOC 2001 (%) Stock C 2001 (ton/ha) -3 Bulk density (Mg.m ) SOM 2007 DMC (%) maize - rice bean SOC 2007 DMC (%) Stock C (ton/ha) -3 Bulk density (Mg.m ) Total gain of carbon (7 years, ton/ha) Carbon gain per year (ton/ha) SOM 2007 CV (%) SOC 2007 CV (%) Stock C (ton/ha) -3 Bulk density (Mg.m ) Difference of SOC CV vs SCV Total loss of SOC between 2001 and 2007 0-10 cm 3.75 2.17 29.76 1.37 10-20 cm 3.50 2.03 27.72 1.37 4.06 2.36 32.29 1.37 3.31 1.92 26.11 1.36 0.36 -0.23 2.71 1.57 21.30 1.36 3.00 1.74 23.80 1.37 -10.98 -8.46 -2.31 -3.92 0-20 cm 57.48 58.40 0.92 0.13 45.10 -13.29 -12.37 Two years rotational sequence. DM of maize = 6,0 t.ha-1 and rice bean = 3,8 t.ha-1 ORIGINAL AND CURRENT SOC – SOUTHERN XAYABURY Document obtenu sur le site http://Agroecologie.cirad.fr Between 2001 and 2007 SOM 2001 (%) SOC 2001 (%) Stock C 2001 (ton/ha) -3 Bulk density (Mg.m ) 0-10 cm 3,88 2,25 30,83 1,37 10-20 cm 3,29 1,91 26,09 1,37 SOM 2007 DMC (%) maize - rice bean SOC 2007 DMC (%) Stock C (ton/ha) -3 Bulk density (Mg.m ) 4,46 2,59 34,74 1,34 3,80 2,21 30,20 1,37 SOM 2007 CV (%) maize - rice bean SOC 2007 CV (%) Stock C (ton/ha) -3 Bulk density (Mg.m ) 2,71 1,57 21,49 1,37 3,00 1,74 23,78 1,37 -1,75 -13,24 -0,80 -6,42 Difference of OM CV vs SCV Difference of SOC CV vs SCV 0-20 cm 56,92 64,93 45,27 -19,67 Two years rotational sequence. DM of maize = 10,6 t.ha-1 and rice bean = 3,8 t.ha-1 Document obtenu sur le site http://Agroecologie.cirad.fr CONTENT 1. Brief presentation of the context in the Southern xayabury 2. Materials and methods 3. Results 4. Discussion and Prospective Document obtenu sur le site http://Agroecologie.cirad.fr DISCUSSION AND PROSPECTIVE Soil aggregation, water holding capacity and biological activity increase under no-till and cropping sequence but… Document obtenu sur le site http://Agroecologie.cirad.fr DISCUSSION AND PROSPECTIVE …we have to generate no-till and intensive (high dry matter production > 15 t.ha-1) cropping sequence to optimize the main functions of SCV systems: nutrients recycling, water use efficiency, integrated weeds management, SOC sequestration and profitability. Document obtenu sur le site http://Agroecologie.cirad.fr DISCUSSION AND PROSPECTIVE DM = 7.8 t.ha-1 (maize) + 10.6 t.ha-1 (B. ruziziensis + C. cajan) DM = 7.4 t.ha-1 (maize) + 7.9 t.ha-1 (C. cajan) DM = 7.2 t.ha-1 (maize) + 4 t.ha-1 (V. umbellata) Analyze SOC for a range of no-till and cropping sequence in ‘station’ and in farmers’ fields: • To record the potentialities of these systems in sequestrating C and the impact of each specie on the form of C (stable and active pool). • To establish relationships between SOC and profitability. Document obtenu sur le site http://Agroecologie.cirad.fr H22O Why the soil organic matter is Importance of continuous OM flux to influence soil aggregation, soil the key component structure and OM as a consequences influence air flux, water retention, and of the no-tillage nutrients cycling. AIR systems? NUTRIENTS From J.C de Moraes Sà Document obtenu sur le site http://Agroecologie.cirad.fr THANKS FOR YOU ATTENTION
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