Understanding Soil Variability to Utilize Variable Rate Fertilizer Technology

Transcription

1 Understanding Soil Variability to Utilize Variable Rate Fertilizer Technology Agronomy Update Red Deer, AB Jan 17 & 18, 2012 Ross H. McKenzie Research Scientist Agronomy Research & Innovation Div.

2 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

3 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.

4 What are all the factors that affect yield? What factors can you control? What are the soil factors that affect yield?

5 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

6 How much soil variability is needed to make VRF application economically beneficial?

7 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??

8 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?

9 Soils vary with topography

10 Soil Profile Variation with Topography

11 How Do Soil Physical and Chemical Characteristics Change with Slope Position? Depressional area Lower slope position Mid slope position Upper slope position Knolls

12 Upper Slope Mid Slope Lower Slope

13 What are the soil characteristics of upper, mid and lower slopes?? Physical: Chemical:

14 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

15 What are the soil characteristics of Lower Slope positions?? Physical: Chemical:

16 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

17 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

18 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

19 Which areas should receive higher rates of fertilizer? Knolls Upper slope position Mid slopes position Lower slope position

20 Variable Rate Fertilizer Study Mercer Farms

21 How variable are soils? ½ mile transect 16 sampling sites Which is most variable? N- P- K- S-

22 Elevation Change Over a Half Mile on Mercer Farm Elev (Feet) 3080 Elevation (ft) Transect Location

23 Site N (0-24 ) P K S ph < < < < < < <5 6.9

24 Variation in Soil Nutrients with Landscape Nutrient Low High Median Nitrate-N (0-24 ) Phosphorus (0-6 ) Potassium (0-6 ) Sulphate-S (0-6 ) < ph (0-6 )

25 Soil Nitrate-nitrogen Variation with Landscape Elevation (ft) Soil N Elevation (ft) Soil N (lb/ac) Transect Number 0

26 Soil Phosphorus Variation with Landscape Elev (Feet) Soil P Elevation (ft) Soil P (lb/ac) Transect Location 0

27 Soil Phosphorus Variation with Landscape Elev (Feet) Soil P Elevation (ft) Soil P (lb/ac) Transect Location 0

28 Soil Potassium Variation with Landscape Elevation (ft) Soil K Elevation (ft) Soil K (lb/ac) Transect Number 0

29 Soil Sulphate Variation with Topography Elevation (ft) Soil S Elevation (ft) Soil S (lb/ac) Transect Number 0

30 3090 Soil ph Variation with Topography Elevation (ft) Soil ph Elevation (ft) ph Transect Number 0.0

31 3 Low Mid-Slope Hill Yield (kg/ha) Fertilizer Treatments (kg/ha) Low Mid Hill

32 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

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35 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

36 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.

37 Questions?