Spatial variation of soil constraints and its implications for site-specific soil and nutrient management in CA. Yash Dang
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This document discusses spatial and temporal variability in soil properties and its implications for site-specific soil and nutrient management in conservation agriculture. It finds that variation between seasons is greater than within-season variation. It also evaluates different methods of measuring soil variability, including farmer knowledge, yield monitoring, remote sensing, and discrete soil sampling. The document advocates for site-specific soil amelioration like applying gypsum to address sodicity issues. It also promotes matching nutrient inputs to realistic yield potentials based on soil constraints in order to optimize economic returns from fertilizer application.
Spatial variation of soil constraints and its implications for site-specific soil and nutrient management in CA. Yash Dang
- 1. Spatial variation of soil constraints and its implications for site-specific soil and nutrient management in conservation agriculture Yash Dang, Lindsay Bell and Ram Dalal
- 2. Spatial and Temporal Variability Mean 18.9 Mean 1.79 Mean 0.91 Mean 1.29 SD 10.7 SD 0.39 SD 0.31 SD 0.40 CV 56.6 CV 21.5% CV 34.5% CV 31.2% Variation between seasons > Variation within a season PM should consider both spatial and temporal aspects
- 3. Measuring Variability a. Grower’s Knowledge & Experience Heavy black soil, brigalow softwood Open black soil, plain, no tree Light soil, box, scattered brigalow High yielding Medium yielding Poor yielding
- 4. Measuring Variability b. Continuously (on the go yield monitoring)
- 5. Measuring Variability b. Continuously (proximal sensing) 4.0 2 Y=3.95 - 0.02 ECa_LL, r =0.97 Average wheat yield (t/ha) 3.5 NS; ECa_UL 3.0 2.5 2.0 1.5 1.0 0 50 100 150 200 250 ECa (mS/m)
- 6. Measuring Variability c. Remotely (Satellite imagery, Landsat) near-IR – red near-IR + red 5 Y = 6.48 - 0.35 NDVI, r2=0.79 Wheat grain yield_2007 (t/ha) 4 3 2 1 0 0.2 0.4 0.6 NDVI_2007
- 7. Measuring Variability d. Discretely (point sampling of soil)
- 9. Ground-truthing Cl (mg/kg) EMgP (%) NO3-N (mg/kg) VMCLL (cm3/cm3) 0 500 1000 30 60 0 20 40 0.2 0.3 0.4 0.0 Low 0.2 Medium High 0.4 Soil depth (m) 0.6 0.8 1.0 1.2 1.4
- 11. Gypsum responses 3.5 Gypsum 0 b 3.0 Gypsum 2.5 t/ha (2005) a 2.5 a a Grain yield (t/ha) 2.0 b 1.5 a 1.0 0.5 0.0 Wheat 2005 Chickpea 2007 Wheat 2008 Cumulative gross margin for surface applied gypsum $143/ha over 3-4 years
- 12. Gypsum reduces Cl concentration Cl (mg/kg) 0 500 1000 1500 0 20 Control Gypsum spread 40 Soil depth (cm) 60 80 100 115 t NaCl 120 140 160
- 13. Site-specific nutrients management: Matching inputs Low 16 Medium 15 High 13 14 10 11 12 5 7 High 8 9 Medium 6 N46 Low Wheat grain yield (t/ha) 5 N23 1 4 N0 4 N46 2 N0 N23 3 N0 N23 N46 3 M e te rs 0 12 5 2 50 50 0 7 50 1 ,0 0 0 2 1 0 10 20 30 40 50 Applied nitrogen (kg N/ha)
- 14. Matching Inputs to Realistic Yield Potential • Determine realistic yield potential in presence of soil constraints Ymax = (Starting Soil Water + In Crop Rain) * Water Use Efficiency Realistic Yield Potential = Ymax Soil constraints Soil Nutrition
- 15. Nitrogen Requirement N required (kg/ha) = (RYP x protein goal x 1.75 x 2)- Av. NO3-N to 0.9 m NO3-N (mg/kg) 0 20 40 0.0 Low 0.2 Medium High 0.4 Soil depth (m) 0.6 0.8 1.0 1.2 1.4
- 16. Matching Nitrogen Fertilizer: Economics Zone 1 Zone 2 Zone 3 Field average (20 ha) (28 ha) (16 ha) (64 ha) Low Medium High Realistic yield potential 3.36 2.21 (t/ha) 1.29 2.22 Nitrogen requirement 59 100 150 101 (kg N/ha) Average available N in 119 55 36 70 the soil (kg N/ha) Farmer’s rate (kg N/ha) 46 46 46 46 Actual N required (kg 114 31 N/ha) 0 45 Consequence of uniform 2.0 t urea 0.06 t urea 3.9 t urea 2.0 t urea N application required waste waste wasted
- 17. Matching Nitrogen Fertilizer: Environmental 10 High 14 High N-denitrification (kg/ha) Medium Medium N-leaching (kg/ha) Low Low 5 7 0 0 0 25 50 0 25 50 Applied nitrogen (kg N/ha) Applied nitrogen (kg N/ha)
- 18. In Summary Integrate spatial data with grower’s knowledge and ground-truthing to identify spatial variability of constraints to crop production Evaluate sustainable development goals (economic, environmental and social) for site-specific soil and nutrient management
- 19. Thanks to number of colleagues who have worked on the project over the years Thanks! And many more……