1. Fertilizing for No-till
Kent Martin
Southwest Research Extension Center
Kansas State University

2. Overview Nitrogen Phosphorus Loss mechanisms Requirements
No-till considerations
Requirements
Nitrogen use efficiency
Management Factors
Phosphorus
Background
Plant uptake
Recommendations

3. Overview Potassium Stratification of P and K Starter considerations
Plant uptake
Recommendations
Stratification of P and K
Starter considerations
Summary

4. Nitrogen Primary crops in Kansas use large amounts of N
Soils contain thousands of pounds of N
Naturally deficient in most agricultural soils
Environmental concern due to loss
How much is available?
Why is some not available?
We make assumptions for the best estimate

5. Nitrogen Soil organic matter – “storage mechanism” for N
Plant and animal residue
Decomposed organic materials
True organic matter – persistent decomposition products
Assumptions
Range from 1-4% average is 2.2% in Kansas
2,000,000 pounds x 2.2% = 44,000 pounds soil organic matter
If soil organic matter is 5% N then 44,000 pounds x 5% = 2,200 pounds N in soil
We have a lot of N from soil organic matter!! Why are our crops typically deficient??

6. Nitrogen How do we use it?? Mineralization
Conversion of this organic matter (proteins and amino acids) by microbes
R-NH2 + H2O → NH3 + R-OH + Energy
Requires air
Rate is sensitive to temperature and moisture
Occurrs when it is cold, but not frozen

7. Nitrogen Immobilization – opposite of mineralization
Occurs with an abundance of carbon
Microbial populations increase to utilize carbon
Inorganic N (available) is used for this process
Transforms to organic N and is unavailable
C:N ratio controls the balance
<25:1 = net mineralization (N released)
>25:1 = net immobilization (N tied up)

8. Nitrogen Common C:N ratios Source Microorganisms Soil O.M. Alfalfa
Soybean Residue
Rotted Manure
Green Rye
Cornstalks
Small grain straw
Grain Sorghum
Sawdust
% Carbon 50 52 40
--- --
% Nitrogen
6.2
5.0
3.0
0.7
0.5
0.1
C:N Ratio
8:1
10:1
13:1
15:1
<20:1
36:1
60:1
80:1
400:1
Mineralization
Immobilization

9. Nitrogen What does this mean for no-till??
Crop residues on the soil surface causes immobilization
Consider placement to overcome immobilization
Inject>surface band>broadcast
Starter placement works well (caution seed placed rates)
Some crop residues (<25:1 C:N) causes mineralization
Previous crop adjustments for cool season crops
Corn, wheat, soybeans = 0; Sorghum, sunflowers = +30; Fallow = -20 (0 if profile nitrate test is used)
Previous crop adjustment for warm season crops
Corn, wheat, sorghum, sunflowers = 0; Soybeans = -40; Fallow = -20 (0 if profile nitrate test is used)

10. Nitrogen - Loss N loss mechanisms Runoff Leaching Volatilization
Denitrification

11. Nitrogen - Loss Runoff – physical movement off field
Slope adds risk
Factors that prevent movement into soil
Frozen soils
No-till surface residue minimizes this loss
Leaching – downward movement of nitrate
Course textured soils
Significant rainfall or over irrigation
N in nitrate form adds risk
Extreme early application

12. Nitrogen - Loss Denitrification – loss of N from nitrate as a gas
Fine textured soil, low permiability
Warm, moist conditions drive it
Slow conversion to nitrate decreases loss risk
Over application of irrigation water
Volatilization – loss of ammonia from urea (gas)
Caused by evaporation of water on warm windy days
Can be a problem in no-till or grass
High pH and free ammonia increase risk

13. Nitrogen - Requirements
Typical equation
N rec = (yield goal x coefficient) – credits
Coefficients
Corn and sorghum = 1.6
Wheat = 2.4
Sunflowers = 0.075
Credits
Previous crop adjustment
Soil organic matter (% x 20 warm season, % x 10 cool season)
24 inch soil test
Manure
Irrigation water

14. Nitrogen - Requirements
Example calculation
180 bu corn needs 288 lb N (180*1.6)
2% organic matter contributes 40 lb N (2*20)
In rotation with soybean contributes 40 lb
Profile nitrate test has 30 lb available
N need is 178 lb N per acre
178=
No-till adjustments
Add lb N

15. Nitrogen Use Efficiency
What you apply and what you utilize
Typically low – we never use 100% of what we apply
Global effort to increase efficiency
Fertilizer source
Application timing
Fertilizer additives
Tools for rate determination
Soil test
Sensors

16. Nitrogen Use Efficiency
Typically low – average <50%
N Rate N Uptake Grain Yield Harvest Percent N Increment Increment
lbs/a lbs/a bu/a Index Recovery Response Recovery
40 S % %
70 S+sd % %
100 S+sd % %
130 S+sd % %
160 S+sd % %
190 S+sd % %
220 S+sd %
200 pp %
N response to dryland corn: Manhattan, 2006

17. Nitrogen – Management Factors
How do we best utilize our N?
Timing – as close to utilization as possible
Rate – determine accurate application rates
Placement – apply below the soil surface if possible
Fertilizer source – AA, UAN, Urea
Specialty fertilizers – ESN
Fertilizer additives
Agrotain – urease inhibitor
N-Serve – nitrification inhibitor
Super U – urease and nitrification inhibitor

18. Nitrogen – Management Factors

19. Phosphorus An environmental concern
P concentration in top 3-4 inches controls dissolved P in runoff (a concern for us???)
Soils contain 300 to 2,000 lb/a P, most is unavailable
Supplied to plant roots by diffusion (~95%)
Diffusion is slow as compared to other nutrients
Moves short distances (1/8 inch or 1+ inch, 1954 data)
Early plant P concentration is affected by proximity and rate

20. Phosphorus Why do we want P uptake in a young plant?
This figure is from the new IPNI Fertilizing for Irrigated Corn publication. There are a few important points in this figure. First is that P uptake begins very early in the life of corn. Note that P uptake is a precursor to significant dry matter accumulation. Consider the uptake was measured by above ground biomass concentration and yield and realize that the roots are taking up P even earlier than this illustration suggests. The figure on the right is from Mengel and Barber. It shows the importance of early season P supply to plants. The amount of P taken up per unit root mass is much greater early in the season than later.
From: Fertilizing for Irrigated Corn, 2008
From: Mengel and Barber

21. Phosphorus Placement is important Roots flourish where P is applied
Most preferred placement is starter
There is a relationship between placement and root growth. This is the reason we place P near the plant to attain increased root growth and uptake. These images show how placing adequate rates of NPK differ from placement of P only in a band. Note that roots increase only in the band where as NPK application in a band causes more root growth throughout the root profile.
Drew 1975

22. Phosphorus What affects P availability Crops Grown Clay content
Time and method of P application
Aeration
Compaction
Moisture
Temperature
Phosphate status of the soil
Other nutrients
Soil pH

23. Phosphorus - Recommendations
Sufficiency and build/maintain

24. Potassium Not an environmental concern Very little movement (1/4 in.)
Supplied to plant roots through diffusion
Very slow
In extremely sandy soils with flooding, some can be leached (Concern for us??)
Very salty fertilizer sources
Band placements should not be with the seed
Potassium is different from P in that it is not a significant environmental concern. Traditional thought is that K moves about twice as much as P. Either way, there is very little movement except with sands that have a low exchange capacity and are ‘held’ loosely. If they are flooded in this situation, there can be significant leaching. As with P, most is supplied through diffusion. The big difference in P and K is the saltiness of the fertilizers. K is much saltier and thus can be a problem if placed too close to the seed.

25. Potassium Very rapid uptake of K
This illustration shows the very rapid uptake of K. It begins just a little later than P, but is taken up much faster. Notice that the uptake is mostly complete just after silking.

26. Potassium What limits K uptake Poor aeration Compaction
Very dry or very wet soils
Cold temperatures
The picture is of the effects of tillage on K availability. The right is tilled and the left is no-till.

27. Temperature and potassium response

28. Potassium - Recommendations
Sufficiency and build/maintain

29. No-till factors affecting P and K
Cold wet soil in spring limits plant growth, P and K diffusion, and thus uptake
Reduced soil moisture loss/increased water infiltration improves uptake and efficiency
Decreased erosion decreases nutrient loss
There are clearly many factors that affect P and K in no-till, but the issues related to temperature and moisture typically overshadow any others.

30. Nutrient Stratification
Stratify means to form layers or strata
Stratification is simply a way to describe something that is layered. We probably most typically think of road cuts or layered rock where you can see the obvious layers or color changes. I also like to think of soil horizons to illustrate this. This picture is of the Grand Canyon showing some of these layers.

31. Nutrient Stratification
‘Layers’ of nutrient concentrations
The concentrations typically decrease with depth causing nutrient enrichment in the surface layers
0-3 in.
3-6 in.
6-9 in.
9-12 in.
12-24 in.
I made this illustration to describe how the surface concentrations of a given nutrient is higher and that the nutrient concentration typically decreases with depth. However, some situations may have higher levels of a given nutrient at a specific depth if it was applied at a depth or if tillage or geologic/erosion events buried the nutrient rich layer.

32. Nutrient Stratification Development
Not a concern in the past
Conventional heavy tillage provided deep mixing so stratification did not develop
No-till/reduced till situation
Mobile nutrients do not stratify like immobile ones
Inadequate soil mixing to alleviate stratification
Surface application of nutrients (manure)
Nutrient uptake and surface decomposition
Explained next
Nutrient stratification was never a concern because we typically mixed the soil enough for it to be uniform in most nutrient concentrations. Depending on when specific portions of the US started reduced/no-till (1970’s as the earliest and 1990’s as the latest), producers, consultants, and researchers noticed that the concentration of nutrients were highly variable depending on depth. This became a concern especially with immobile nutrients for various reasons that will be explained later.

33. Nutrient Stratification Development
Nutrient uptake and decomposition/deposition
Assume a 150 bu/ac corn crop
This example is taken from some of the research I conducted in which I had actual biomass yield, P concentration, and grain yield and P concentration.
Dale Leikam

34. Stratification of P
This is an example of stratification of P in 4 soil profiles. This data was taken from the initial soil samples from Kent Martin’s dissertation. It is clear that there are much higher concentrations of P in the surface portions of the soil. Here, the high concentrations in the Manhattan and Tribune sites minimize the appearance of stratification at Ottawa and Scandia. However, the stratification was there as well. The concentrations in the upper 3 inches were a little more than 9 ppm, while the next depth was closer to 5 ppm – still significant stratification.
KSU, 2009

35. Tillage and Stratification of P
This data is from Antonio Mallarino and shows the stratification of P in various tillage systems. Note that everything without a plow seems to have impressive stratification. Also note the stratification in no-till.
Mallarino, ISU

36. Tillage and Stratification of K
Mallarino, ISU

37. Potassium Stratification
Long-term tillage in Indiana (Holanda)
This is another example of stratified K in soil test data. It is from a long-term experiment in Indiana. Notice even tillage with a chisel has stratification. The image is of 24 years of no-till and the effects of crop removal. You can see that the areas under the crop are in the low category, while the inter row spaces are in the high category.
Gordon, KSU

38. Remedies for Stratification
Tillage
Soil mixing will create uniform distribution of nutrients
May not be advisable
Nutrient application
Avoid surface application
Deep application
**Do We Need To Remedy It??**
The obvious remedy for stratification is to till the soil to mix the nutrients evenly through the tillage depth. This may create uniformity, but at what cost and how much tillage will have to be done to create “uniformity”. Careful attention should be placed on the value of no-till and a realization that no-till is more beneficial than tilling to relieve stratification. The next best thing is to apply these nutrients in a manner that does not build up the surface layers of the soil. This means deep application, which will again create disturbance in no-till environments. These options are deep coulter application or strip till with nutrient application. The last question we have not yet answered is do we need to be worried about it?

39. Effect of Placement on Yield
Here, we see the effect of placement of P on corn and soybean yields in Iowa. What is interesting is that there is basically no difference in the method of application, regardless of previous tillage.
Mallarino, ISU

40. Effect of Placement on Yield
This is the equivalent of the last slide but with K. Notice that there seems to be a distinct advantage to placing K deep with corn. This is not as extreme when soybean was evaluated.
Mallarino, ISU

41. Effect of Placement on Yield
Starter by Placement by Rate Factorial 2006, 2007, 2008
Effect
Pr > F
Starter
0.01
Placement
0.31
Rate
0.75
Starter × Placement
0.11
Starter × Rate
0.83
Placement × Rate
0.66
Starter × Placement × Rate
0.18
This data is Kansas data that shows that there was not a placement or rate effect, but there was a starter effect. This site had 9.5 ppm P.
Proc Mixed

42. Effect of Placement on Yield
Most studies mention that there was not a benefit from deep band application of P and an inconsistent benefit from K
Note: There is not a penalty for deep banding P or K. This may be equally important
Provides options for producers

43. Placement and Soil Test
Placement options clearly alter vertical distribution
What about lateral distribution
Broadcast maintains uniform lateral concentration
Starter alters lateral uniformity, but typically at low levels
Deep banding increases vertical and lateral variability due to depth and higher rate of application.

44. Effect of P Placement on Soil
This data is from KSU (Kent Martin’s Dissertation) showing the effect of application

45. Effect of P Placement on Soil
Soil test P concentration mean (taken from under the row)
Depth (cm)
Broadcast
Deep Band
LSD*
Scandia
0-7.6
28.5
13.4
12.13
7.6-15
9.5
21.4
9.72
*=Protected LSD; Calculated using Proc mixed (alpha=0.1)
Soil test P Coefficient of Variation (taken from under the row)
Depth (cm)
Check
Broadcast
Deep Band
Scandia (CV, %)
0-7.6
66.8
33.0
9.1
7.6-15
23.6
19.9
86.9
The first table shows the broadcast and deep band treatments and associated concentrations of P. These samples were taken after one full rotation of corn and soybeans with a total application of 80 lbs per acre. The samples were taken from directly under the row to best assess the differences in application increase or crop removal. It is clear here that you can tell there is a significant difference between the broadcast and deep band treatments. In other words, you can find the band if there was one or you can tell if the stratification was near the soil surface. However, as the second table shows, there is a very high degree of variability associated with these data. Notice that we have broken the vertical samples by depth. In the broadcast, there is a pretty significant amount of variation in the soil test data. However, when you look at the variation in deep band values, it becomes overwhelming. What does this mean? Although we can detect the band, we don’t have much confidence in what the true value of the soil test is. Next, we should note that we have actually decreased the variability from the check. This variability is likely a function of crop removal under the crop row thus causing a depletion zone with variable P concentrations.

46. Starter fertilizer
Great when an early delay cannot be offset during the season
Useful if nutrients are not in the seedling root zone – too deep or on the surface
Cold wet conditions limit uptake
Late planting dates
Most frequent response from no-till management
Seldom enough in low testing soils
Apply no more than 8-10 lb N+K with seed!!
This is a summary of conditions that may warrant the use of starter applied nutrients

47. Summary Nitrogen is the most frequent limiting nutrient
Concerns for no-till
Minimize contact of N fertilizer with residue
Avoid loss conditions – sources, placement, timing, rate, additives
Adjust cool season rates for no-till
Increase N use efficiency through all management factors

48. Summary Phosphorus – second most limiting in our area
Starter may give best response in no-till
Won’t be useful for raising soil test level
Needed early in the growing season
Can become highly stratified after years of no-till
Not a significant concern
Potassium – not a big concern in our area
Needed early in growing season
Can become highly stratified
More frequent response than with P
Use caution with starter application

49. Questions??