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

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

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

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

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??

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

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)

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

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)

Nitrogen - Loss N loss mechanisms Runoff Leaching Volatilization Denitrification

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

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

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

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=288-40-40-30 No-till adjustments Add 20-30 lb N

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

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 0 91 98 0.32 --- --- --- 40 S 106 115 0.36 38% 17 38% 70 S+sd 124 133 0.38 47% 18 60% 100 S+sd 135 149 0.42 44% 16 37% 130 S+sd 156 164 0.40 50% 15 70% 160 S+sd 161 172 0.46 44% 8 17% 190 S+sd 177 177 0.43 45% 5 53% 220 S+sd 160 154 0.43 31% - 23 --- 200 pp 173 162 0.41 41% --- --- N response to dryland corn: Manhattan, 2006

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

Nitrogen – Management Factors

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

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

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

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

Phosphorus - Recommendations Sufficiency and build/maintain

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.

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.

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.

Temperature and potassium response

Potassium - Recommendations Sufficiency and build/maintain

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.

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.

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.

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.

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

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

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

Tillage and Stratification of K Mallarino, ISU

Potassium Stratification Long-term tillage in Indiana 1975-1994 (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

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?

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

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

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

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

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.

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

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.

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

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

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

Questions??