1. Importance of Soil Testing
Precision nutrient management has been around for some times, because varying the rates of crop inputs to meet site-specific needs makes economic and environmental sense. I am going to spend a few minutes to talk about grid sampling based nutrient management strategy.
Hailin Zhang
Department of Plant and Soil Sciences

2. Precision Nutrient Management Strategies
Grid soil sampling
Apparent Electrical Conductivity
Yield monitor/mapping
Sensing techniques
As far as I know, these are the main strategies researched and applied. The first 2 are soil based and the other 2 are crop based.

3. Purposes of Soil Sampling
Measure the nutrient content or availability of the soil
Identify nutrient deficiencies
Predict crop response to added nutrients
Build a nutrient management plan
Those are the main purposes of soil tset

4. Soil Testing History 1842 - Liebig stated his “law of the minimum”.
Rothamsted Experimental Station established.
Magruder Plots established in Stillwater, OK.
E.A. Mitscherlich related plant growth to nutrients.
1920’s - Bray, Hester, Morgan, Spurway, and Troug developed the concept of labile versus total analysis.
1940’s & 50’s - Use of fertilizers spur interest in soil testing as a management tool.
1960’s - Evolution of soil testing continues as technological advances allow for improvements in analysis, correlation, and interpretation.

5. Milestones in Soil and Plant Analysis
pH Electrode 1932
Flame Photometer 1940
Bray 1945
Olsen 1954
P - Ascorbic Acid Determination 1962
Atomic Absorption 1960
ICP 1970s
DTPA 1978
PC Computer 1980
Mehlich

6. Soil and plant tests Water Animal Waste Feed and forage
Main services provided

7. Directly Serving All Counties, in Oklahoma; Also serve state, tribal and federal agencies, consultants, researchers and students.
We have direct service to all county extension offices in the state
SWFAL

8. Number of Samples Analyzed Since 1986

9. Soil Test Results of Oklahoma CroplandpH
<5.5
>7.5 %
25%
48%
19% 8%
Nitrate-N
<10
10-20
20-40
>40
43%
29%
18%
10%
STP
<65
65-120
>300
71%
16% 9% 4%
STK
<120
>350
36%
20%
37%

10. Soil Samples from One Producer
Lab ID
Sample pH
NO3-N (lbs/A)
P (lbs/A)
K (lbs/A)
512408 6
6.9 40 52
1010
512410 7 30 36
882
512411 8
5.2 18
162
726
512412 9
4.8 32
173
654

11. Variety Response to Soil pH
Limed
Not Limed
Custer, Ok101, Jagalene, Jagger, , AP502Cl, Ok102, 2137

12. Ok 101

13. The state-of-the-art equipments;
dedicated and well trained technicians;
technical support;
develop and validate methods; research to ensure accurate recommendations

14. QC/ QA Program in place
Use:
Internal &
External
Check Samples

15. Soil Sample Flow Chart Producer County Extension USPS Mail
OSU Mailing Services
SWFAL Login Room
Reports Online

16. Here is a winter wheat field at the Research Station in Perkins
Here is a winter wheat field at the Research Station in Perkins. Again tremendous differences in wheat growth. The forage yields ranged from practically zero to over 2,500 lbs/A. What we found the problem was low soil pH and high Al level. The forage yields were highly correlated to the Al saturation percentage.

17. Scooping samples for extraction
One acre to 6 inch deep contains about 2 million lbs of soil

18. The greatest potential for error in soil testing is in taking the sample
The farmer, or the person taking the soil sample, must provide the laboratory with a uniform, representative sample ... a critical component for the laboratory in providing accurate soil test results and fertilizer recommendations. Each sample, weighing only a pound or less, can represent millions of pounds of soil in the field. The greatest potential for error in soil testing is in taking the sample.

19. Considerations for Soil sampling Strategies
Locate variability responsive to fertilizer and lime
Obtain a sample that accurately represents the area sampled
Balance cost of sampling with the value of information

20. Recognize Field Nutrient Variability
Nitrate - Nitrogen
lbs/acre
0-30
31-40
41-50
51-60
61-80
>80
This graph shows the variability of nitrate-nitrogen in a 75’x75’ area of a field. Each small plot is a 5’x5’ square. Nitrate-N ranged from 25 lbs/acre to 102 lbs/acre over the area.
Each sample submitted for analysis should be representative of the the entire sampling area.
Avoid taking sample from any unusual spots, such as, manure piles, cracks, etc, to avoid any misrepresentation.
Data gathered from OSU Agronomy Research Farm
(Nitrate-N within a 75’ x 75’ plot)

21. 20 cores are needed to make a representative
composite sample in order to get reliable soil test results
By taking enough soil cores randomly in a field to make a composite sample, one can hit the average nutrient status repeatedly.

23. Soil Sampling Strategies
Whole field composites: Composite sample representing the average nutrient status of the field * * * * * * * * * * * * * *

24. P Changes with Depth (no-till)
P (ppm) 0”
120 2” 55 6” 35
12”
Soil test P changes with depth. N,K, pH, and many other soil properties also change, especially when the field is not cultivated. Soil phosphorus on fields receiving top dressed poultry litter tends to accumulate near the soil surface.
A 0-6 inch sample is recommended for consistent and reliable soil test results. 31
24”

25. The key components of a good sampling technique.

26. Soil Sampling Strategies
2. Zone composites: Break field based on known or expected source of variability
As far as I know, these are the main strategies researched and applied. The first 2 are soil based and the other 2 are crop based.

27. Soil Sampling Strategies
3. Grid Sampling: Break field based on ordered pattern
Grid cell method: similar to whole field
Grid center method
Point sampling * * * *
As far as I know, these are the main strategies researched and applied. The first 2 are soil based and the other 2 are crop based. * * * * * * * * * * * * * * *

28. 1. Random sampling of the entire field ,
Field Soil Sampling, Soil Testing, and Making Fertilizer Recommendations Exercise
1. Random sampling of the entire field ,
25 cores of soil from a 0-6” depth
filling two soil sample bags from the composite mixture
2. Grid-cell sampling
15 cores of soil from a 0-6” depth
3. High resolution
Have been realized the existence of field spatial variability, people have tried to account for them through management. This excise is to validate the existence of field variability using 3 different sampling schemes.

29. Whole field 1 acre grid Sub-grid Center area Point * * * * * * * * X X
A grid soil sampling exercise was conducted in this 27 acre field for the last two years. The dept. of animal science manages this field and they will use it to receive manure from the new swine facility they are building. X X X X X X * * * * * * * *

30. Whole field sample pH: Team 1: 6.0, 6.1 Team 2: 6.4, 6.4
Soil pH raged from 4.5 to 7.5. You will know where lime should be applied.

32. Comparison of Whole Field Sample between 2000, 2001 and 2002

33. Comparison of Area of Sampling for 2002

34. Why Account for Spatial Variability of Soil Properties
Improve performance of ag. practices
Either costs go down and/or returns go up
Avoid over application that might be environmentally harmful
Have been realized the existence of field spatial variability, people have tried to account for them through management. Because:

35. Analysis Costs of Various Sampling Intensities
Grid Spacing
Area/sample
Costs*
Feet
Acres
$/acre 66
0.1
100
104
0.25 40
148
0.5 20
209 1 10
330
2.5 4
467 5 2
660
Conventional
*at $10/sample

36. Choosing a Soil Sampling Strategy
Level of management and the resources to account for variability
Whole field sampling most appropriate when fertility is high and variability is low
Zoning/sub-field sampling may be most appropriate when
Location of variation known
Sampling areas are large
Limited resource
Grid sampling maybe appropriate if location of variation is unknown and variable rate applicator is available

37. How to use soil test information?
As far as I know, these are the main strategies researched and applied. The first 2 are soil based and the other 2 are crop based.

38. pH value defines relative acidity or basicity
Ammonia
cleaner
Make lime recommendation
9.0
Strong
pH value defines relative acidity or basicity
8.0
Basic
Medium
Slight
7.0
Pure water
Slight
Most productive soils
Moderate
6.0
Medium
Acid
It covers a scale ranging from zero to 14.0, with 7.0 being neutral… neither acidic or basic. Most productive soils have pH values in the 5.0 to 8.0 range; however, acid or basic soils can be made more productive when properly managed. The relative degrees of acidity and basicity are shown here.
5.0
Strong
Very strong
4.0
Vinegar
Lemon juice

40. Plant Nutrient Recommendation
C H O
N Ca
16 Essential Elements
P Mg
K S
Sixteen chemical elements have been shown to be essential for plant growth. That means the plant cannot complete its normal life cycle if just one of these nutrients is limiting. They are divided into two main groups, non-mineral and mineral.
B Cl Cu Fe
Mn Mo Zn

42. As soil P increases, so does crop yield and the potential for p loss in surface runoff
Sharpley et al., 1998

44. Remediate Contaminated Soil
EC (mmhos/cm) 4 8 12 16
Normal
Saline
ESP %
Increased salt hazard 15
Sodic
Saline-Sodic 30

45. Soil, Water and Forage Analytical Laboratory