Conservation tillage, a south african je hoffman
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72nd SWCS International Annual Conference July 30-August 2, 2017 Madison, WI
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Conservation tillage, a south african je hoffman
- 1. Dr J E Hoffman Department of Soil Science University of Stellenbosch South Africa Email: ehoffman@sun.ac.za Conservation tillage, a South African perspective to optimize water harvesting for crop production
- 2. Introduction • Crop production mainly on arid soils • Average annual rainfall < 450 mm • Interior – summer rainfall • Sandy soils - 1 – 3m deep • Water harvesting important • Winter and summer grain crops • Western and Southern Cape • Mediterranean climate • Shallow soils 0.3 m – sandy to clay • Winter crops – Wheat/Canola/Lupins
- 3. Introduction… • Main aim of cultivation practices • Reduce evaporation • Keep field free of weed • Prevent wind erosion • Soil surface storage – rain water harvesting • Seed bed – good germination • Three cultivation practices compared • Clean tillage – plow • Conservation tillage – controlled traffic • No till – only planting action
- 6. Localities • Summer rainfall • Central – Bloemfontein • Western – Petrusburg • Eastern - Tweespruit • Winter rainfall • Swartland – Malmesbury • Southern Cape - Riviersonderent
- 9. Soils of the different sites • Summer rainfall • Bainsvlei - 1.8 m • Hutton - 2.5 m • Clovelly – 0.6 m • Winter rainfall • Glenrosa – 0.3 m • Shale – wheatered rock • Stone content – 50% of volume
- 10. 2 10 18 26 34 42 50 58 66 74 82 0 - 300 mm 300 - 600 mm 600 - 900 mm Massfractions(%) 2 10 18 26 34 42 50 58 66 74 82 900 - 1200 mm 1200 - 1500 mm 1500 - 1800 mm Particle size (mm) Clay Coarse and fine sand Fine sand Medium sand Coarse sand 2 10 18 26 34 42 50 58 66 74 82 1800 - 2100 mm 2100 - 2400 mm 2400 - 2700 mm 2 10 18 26 34 42 50 58 66 74 82 0 - 300 mm 300 - 600 mm 600 - 900 mm Massfractions(%) 2 10 18 26 34 42 50 58 66 74 82 900 - 1200 mm 1200 - 1500 mm 1500 - 1800 mm Particle size (mm) Clay Coarse and fine sand Fine sand Medium sand Coarse sand 2 10 18 26 34 42 50 58 66 74 82 1800 - 2100 mm 2100 - 2400 mm 2400 - 2700 mm 2 10 18 26 34 42 50 58 66 74 82 0 - 300 mm 300 - 600 mm 600 - 900 mm Massfractions(%) 2 10 18 26 34 42 50 58 66 74 82 900 - 1200 mm 1200 - 1500 mm 1500 - 1800 mm Particle size (mm) Clay Coarse and fine sand Fine sand Medium sand Coarse sand 2 10 18 26 34 42 50 58 66 74 82 1800 - 2100 mm 2100 - 2400 mm Central - Bloemfontein Western - Petrusburg Eastern - Tweespruit
- 11. Particle size (mm) Clay Coarse and fine silt Fine sand Medium sand Coarse sand Massfractions(%) 2 10 18 26 34 42 50 58 66 74 82 No till Plow Conserve Swartland - Malmesbury
- 12. Massfractions(%) 6 14 22 30 38 46 54 62 0 - 100 mm 100 - 200 mm 200 - 300 mm 300 - 450 mm Particle size (mm) Clay Fine silt Coarse silt Very fine sand Fine sand Medium sand Coarse sand Very coarse sand Coarse fragment 6 14 22 30 38 46 54 62 0 - 100 mm 100 - 200 mm 200 - 300 mm 300 - 450 mm CT No till Southern - Riversonderent
- 13. Cultivation practices • Clean tillage • Disk - straw after harvest • Tine implement with sweeps • Stubble on surface • Remove weeds • Plow soil when suitable wet • Seedbed with shallow sweeps • Plant with No till planter
- 15. Cultivation practices.. • Conservation tillage + controlled traffic. • Shallow blade or big V-sweep • Cut stubble below surface • Shallow rod weeder – mechanical driven or • Chemical weed control • Deep tine tillage – soil sufficient wet if soil is compacted? • 600 – 750 mm deep • Plant with no till planter
- 18. Cultivation practices.. • No tillage + controlled traffic. • Chemical weed control • Fertilizer recommendation same with all three cultivation practices • Plant with no till planter
- 20. Crop rotation • Summer rainfall • Wheat – maize (corn) – wheat or • Wheat – sorghum – wheat (long season growers) – 2 crops in 3 years • Winter rainfall (5 year cycle) • Medics – wheat – lupins – wheat – canola – wheat – (fallow for 3 years)
- 21. Components of the water balance • Profile available water content – Neutron moisture meter • Beginning – at planting • End – harvest • Rainfall during growing season • Runoff - (Runoff plots 10 m2) • Drainage/percolation upwards - modeled from drainage curve • ET = balance of above
- 22. Plow Locality Central Western Eastern Swland Southern Watercomponent(mm) 0 50 100 150 200 250 300 Profile water content Rainfall Percolation upwards
- 23. Conservation Locality Central Western Eastern Swland Watercomponent(mm) 0 50 100 150 200 250 300 Profile water content Rainfall Percolation upwards
- 24. No Till Locality Central Western Eastern Swland Southern Watercomponent(mm) 0 50 100 150 200 250 300 Profile water content Rainfall Percolation upwards
- 25. Summer rainfall Evapotranspiration 50 100 150 200 250 300 350 Yield(kg/ha) 600 800 1000 1200 1400 1600 1800 2000 Conservation y = 3.6x + 163.5 R2 = 0.64 No til y = 3.7x + 66.7 R2 = 0.65 Plow y = 5.5x - 10.6 R2 = 0.87
- 26. Winter rainfall Evapotranspiration 0 100 200 300 400 500 600 Yield(kg/ha) 2000 2500 3000 3500 4000 4500 5000 Conservation y = 9.0x + 565 R2 = 0.96 No til y = 4.4x + 1698 R2 = 0.80 Plow y = 3.9x + 1852 R2 = 0.46
- 27. Plow Evapotranspiration 100 200 300 400 500 600 Yield(kg/ha) 0 1000 2000 3000 4000 5000 Summer rainfall y = 5.5x - 10.7 R2 = 0.87 Winter rainfall y = 3.9x + 1852 R2 = 0.46
- 28. Conservation tillage Evapotranspiration 100 150 200 250 300 350 400 Yield(kg/ha) 0 1000 2000 3000 4000 5000 Summer rainfall y = 9.0x + 565 R2 = 0.64 Winter rainfall y = 3.6x + 164 R 2 = 0.96
- 29. No till Evapotranspiration 100 200 300 400 500 600 Yield(kg/ha) 0 1000 2000 3000 4000 5000 Summer rainfall y = 3.7x + 66.7 R2 = 0.65 Winter rainfall y = 4.4x + 1698 R 2 = 0.80
- 30. Production areas Evapotranspiration 100 200 300 400 500 600 Yield(kg/ha) 0 1000 2000 3000 4000 5000 Summer rainfall y = 4.47x +30.6 R2 = 0.68 Winter rainfall y = 4.53x + 168.95 R2 = 0.66
- 31. Conclusion • Summer rainfall – • determined by stored soil water and spring rainfall • contribution by upward percolation • lower water use efficiency • Winter rainfall – • less dependent on stored water – rainfall in season • higher contribution from upward percolation • higher water use efficiency • Profitability • Winter rainfall >> summer rainfall • Wheat imported to sustain consumption