Understanding Soil Variability to Utilize Variable Rate Fertilizer Technology Agronomy Update -2012 Red Deer, AB Jan 17 & 18, 2012 Ross H. McKenzie Research Scientist Agronomy Research & Innovation Div.
Variable Rate Fertilizer Technology VRFT - Is the application of different rates of fertilizer on uniquely different soil areas within a field Purpose - To optimize fertilizer inputs and crop yield How? Identify the uniquely different soil areas within a field Soil sample areas separately Develop fertilizer prescription map for each field based on various soil types and crop yield potential
The Challenges : 1. Determine how to identify uniquely different soil areas within a field. 2. Decide how fertilizers should be managed in each unique soil area.
What are all the factors that affect yield? What factors can you control? What are the soil factors that affect yield?
Soil Factors that Affect Crop Fertilizer Response and Yield Plant Available Soil Nutrient Levels Soil Water Content low, medium, excellent at seeding? Soil Organic Matter soil fertility and nutrient availability Soil Texture Sand Silt Clay content of soil Influences soil water infiltration Influences soil water holding capacity Cation holding capacity Soil ph affect on crops; soil nutrient availability Soil Profile Depth - to C horizon Past Soil Erosion Soil salinity and sodicity Surface water drainage ponding of water in wet years Topography - soils change with slope position
How much soil variability is needed to make VRF application economically beneficial?
Variable Rate Fertilizer Application Risks vs Benefits VRF technology can be expensive - the greater the VRF cost the greater the risk. If you are going to use VFT will it pay??
Soil factors influencing nutrient uptake and crop yield potential Which soil factors related or unrelated? How variable is soil across a given field? How do soil factors vary with landscape? How can we easily identify and differentiate these soil factors in the field?
Soils vary with topography
Soil Profile Variation with Topography 1. 2. 0 6 12 24 36 3.
How Do Soil Physical and Chemical Characteristics Change with Slope Position? Depressional area Lower slope position Mid slope position Upper slope position Knolls
Upper Slope Mid Slope Lower Slope
What are the soil characteristics of upper, mid and lower slopes?? Physical: Chemical:
What are the soil characteristics of Upper Slopes or Knolls?? Physical: Thinner layer of top soil (Ah horizon) Lower soil Organic Matter (OM) level -> poorer soil structure Soil may crust more easily after a rain -> Reduced crop emergence Reduced water infiltration Lower water holding capacity Less stored soil water after rainfall Chemical: Lower soil fertility Low OM > store house of nutrients is greatly reduced Reduced nutrient cycling to release nutrients for plant growth Reduced soil fertility and nutrient status Higher soil ph > higher lime and carbonates in soil will may reduce nutrient availability, affect crop rooting Increased soil salinity -> Subsoil salts near the soil surface
What are the soil characteristics of Lower Slope positions?? Physical: Chemical:
What are the soil characteristics of Lower Slope position?? Physical: Deeper top soil depth (Ah horizon) Higher soil OM -> better soil structure Less susceptible to soil crusting -> Better crop emergence Increased water infiltration More stored soil water after rainfall Prone to standing water or high water table Chemical: Higher soil nutrient levels with better soil fertility Higher Soil OM > store house of nutrients is greatly reduced Increased nutrient cycling to release nutrients for plant growth Lower soil ph Potentially higher soil salinity if water table is present
What are the effects of slope position on crop growth?? Lower nutrient availability -? Possibly reduced soil moisture reserves in subsoil -? Possibly reduced crop emergence -? Reduced rooting depth -? Result potential for reduced or increased crop yield
Important Factors to Consider in Identifying Soil Management Zones? Topography: Slope position Soil variability: Soil nutrient levels N, P, K, S, others at time of seeding Soil moisture status at time of seeding Soil Salinity Depth of top soil/to subsoil Organic matter content Soil ph Soil Texture sand vs clay content
Which areas should receive higher rates of fertilizer? Knolls Upper slope position Mid slopes position Lower slope position
Variable Rate Fertilizer Study Mercer Farms
How variable are soils? ½ mile transect 16 sampling sites Which is most variable? N- P- K- S-
3090 3085 Elevation Change Over a Half Mile on Mercer Farm Elev (Feet) 3080 Elevation (ft) 3075 3070 3065 3060 3055 3050 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Transect Location
Site N (0-24 ) P K S ph 1. 27 40 1079 17 5.6 2. 20 44 1008 14 5.7 3. 17 87 1282 16 5.6 4. 18 117 1689 19 5.5 5. 25 14 649 <5 7.4 6. 28 11 664 <5 7.7 7. 23 12 907 <5 7.5 8. 23 70 1352 17 5.2 9. 23 10 711 10 7.8 10 22 10 540 <5 7.7 11. 15 91 1361 12 5.8 12 22 20 696 <5 6.3 13 21 6 540 <5 7.7 14 20 7 484 23 7.7 15 24 15 540 16 7.7 16 17 41 1173 <5 6.9
Variation in Soil Nutrients with Landscape Nutrient Low High Median Nitrate-N (0-24 ) 15 28 23 Phosphorus (0-6 ) 6 117 20 Potassium (0-6 ) 484 1689 696 Sulphate-S (0-6 ) <5 23 10 ph (0-6 ) 5.2 7.8 6.9
3090 3085 3080 Soil Nitrate-nitrogen Variation with Landscape Elevation (ft) Soil N 100 90 80 70 Elevation (ft) 3075 3070 3065 3060 3055 60 50 40 30 20 10 Soil N (lb/ac) 3050 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Transect Number 0
3090 3085 Soil Phosphorus Variation with Landscape Elev (Feet) Soil P 140 120 3080 100 Elevation (ft) 3075 3070 3065 3060 80 60 40 Soil P (lb/ac) 3055 20 3050 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Transect Location 0
3090 3085 Soil Phosphorus Variation with Landscape Elev (Feet) Soil P 140 120 3080 100 Elevation (ft) 3075 3070 3065 3060 80 60 40 Soil P (lb/ac) 3055 20 3050 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Transect Location 0
3090 3085 Soil Potassium Variation with Landscape Elevation (ft) Soil K 1800 1600 3080 1400 Elevation (ft) 3075 3070 3065 3060 1200 1000 800 600 400 Soil K (lb/ac) 3055 200 3050 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Transect Number 0
3090 3085 3080 Soil Sulphate Variation with Topography Elevation (ft) Soil S 25 20 Elevation (ft) 3075 3070 3065 15 10 Soil S (lb/ac) 3060 3055 5 3050 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Transect Number 0
3090 Soil ph Variation with Topography 9.0 3085 8.0 3080 7.0 Elevation (ft) 3075 3070 3065 6.0 5.0 4.0 3.0 Soil ph 3060 3055 Elevation (ft) ph 2.0 1.0 3050 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Transect Number 0.0
3 Low Mid-Slope Hill 2.5 2 Yield (kg/ha) 1.5 1 0.5 0 Fertilizer Treatments (kg/ha) Low Mid Hill
Fertilizer Treatments N rates: 0, 30, 60 (Urea and ESN), 90, 120, 150 kg N/ha N + P NP + K NPK + S NPKS + Zn on wheat NPKS + B on canola
The technology of developing Soil Management Zones is not well developed or established Soil Variability & VRF Technology Starting Point for VRFT Identifying Soil Management Zones within a field Soil Management Zones developed based on: Farmer knowledge and visual differences in soil types and crop production in a field Colour and black & white air photos Topography maps Soil salinity maps Satellite imagery visible and other spectra Crop yield maps After management zones are identified each zone must be intensively soil sampled to develop fertilizer recommendations
Summary: We have the engineering technology to apply variable rates of fertilizer accurately over changing landscape The key to making VRF technology work is to to develop a flexible, relatively easy system to identify Soil Management Zones This is not a simple or easy task. We have a long way to go to sort out how to develop accurate prescription fertilizer maps that are economical.
Questions?