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osunpk

osunpk

Since 2008 I have served as the Precision Nutrient Management Extension Specialist for Oklahoma State University. I work in Wheat, Corn, Sorghum, Cotton, Soybean, Canola, Sweet Sorghum, Sesame, Pasture/Hay. My work focuses on providing information and tools to producers that will lead to improved nutrient management practices and increased profitability of Oklahoma production agriculture

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Rain makes grain, but also washes Nitrogen away.

Precipitation in the southern Great Plains is never something you take for granted. As I write this blog I am just wondering when it will be dry enough for long enough to finishing sowing my wheat, but I also remember just how dry it was last winter. The last three months, Aug-Oct rank as one of wettest in the states recorded history. Below are the 30, 60, and 90 day rain fall totals (as of 10.26.18) from Mesonet. By the 60 day map most the wheat belt is showing double digits and the 90 day maps shows a lot of our graze out wheat regions in the 20+ inch realm.

30 Day rainfall totals retrieved from Mesonet on 10.26.18.  Putting recording window from Sept 26-Oct 26. http://www.mesonet.org/index.php/weather/category/rainfall

60 Day rainfall totals retrieved from Mesonet on 10.26.18.  Putting recording window from Aug 27 – Oct 2 http://www.mesonet.org/index.php/weather/category/rainfall

90 Day rainfall totals retrieved from Mesonet on 10.26.18. Putting recording window from July 28-Oct 26 http://www.mesonet.org/index.php/weather/category/rainfall

I bring up graze-out wheat for a reason, to get as much forage as possible it is planted as early as possible. I know of fields that were seeded in July and early August. And to produce this great quality forage, nitrogen fertilizer is applied pre-plant. It just so happens that this July more fertilizer was sold than any other month since I have been in Extension. In July producers bought nearly 1/3 of totoal tons of fertilizer what is typically sold in a single year. While a portion of this may have been pre-purchased for later delivery, I know a lot of it made it to the field. To see why this matters, lets take a look at the nitrogen cycle.

 

The nitrogen cycle is made up of a central component (Organic Matter), three N sinks (Microbial/Plant, Atmosphere, Nitrate {NO3}), four loss pathway (Ammonia Volatilization, Leaching, Plant Loss, Denitrification), and five additions (N2 Fixation, Fertilization, Lightning/Rainfall, Industrial Fixation, Plant/Animal Residues). We are going to spend the next bit talking about what is happening in the bottom right corner and left hand side.

When we put anhydrous ammonia (NH3) in the soil it pulls a hydrogen (H) from water and turns in to ammonium (NH4). Urea goes through a similar process but has to first be converted to NH3 by the enzyme urease.  Ammonium is important because it is a positively charged ion (cation) which will be fixed on the cation exchange sites. This means is it not going to move around in soil, but is readily available for plant uptake. However when NH4 is in a soil with temperatures above 50 degrees and in the presence of oxygen the two bacteria nitrosomonas and nitrobacter convert it to NO3. Given warm soils and our good soil moisture levels it very likely that any N applied in July or August would have converted 50% or more of its NH4 into the NO3 form by this point.

Nitrification portion of the Nitrogen Cycle. Complete Nitrogen Cycle. http://psssoil4234.okstate.edu/lecture

Nitrate is a negatively charged ion (anion) which is repelled from the negatively charged soil. This is beneficial for plants as when they take up water, NO3 is taken up though mass flow. The downside is that since NO3 is in the soil solution, where ever the solution goes so does the NO3, that is called leaching. So in well drained soils the recent rains will have caused a fair amount of leaching.  For some areas the NO3 that is leached below the root zone and could potentially be drawn back up as the soils dry. But there are going to more scenarios in which the N is gone, or at least gone elsewhere. In a sloping field the soil water will hit a limiting layer or clay increase layer and move down slope. I have already seen many wheat fields that are showing yellowing on side slopes.

Unfortunately leaching isn’t the only way we are losing N during this wet cycle. Denitrification occurs when the soil is saturated and oxygen (O) levels are depleted.  In anaerobic conditions, microbes strip O from NO3 reducing it gaseous forms. Typically it takes about one week of standing water to start seeing high levels of denitrification.

Nitrate loss pathways of the Nitrogen Cycle.
Complete Nitrogen Cycle. http://psssoil4234.okstate.edu/lecture

What does this all mean? Conservative guess is that for July or early August applied N we could be looking at losses of 50% or more.  This is a rough guesstimate of course, a fields soil texture, slope, soil type, tillage etc will all impact the loss amount.  As the date of application moves closer to Oct there will have been less nitrification and less total rainfall. What I can say with 100% certainty is that if N fertilizer was applied any time from July through early September, N has been lost.

So whats my N manage recommendations? First, foremost, and always This is the perfect scenario where N-Rich Strips will pay off! (Here’s a blog on N-Rich Strips https://osunpk.com/2013/09/19/nitrogen-rich-strips/). The N-rich Strip will allow you to detect N stress early, which for grazers is important. Close attention needs to be paid on fields with wheat being grown for grazing, N deficiencies will reduce forage production and gain. If the N-Rich strip shows up or there are signs of N deficiencies (yellowing of older leaves from the tip toward the collar) its time to be looking at applying N. For grain only fields we have some time. It is important though that as we get closer to spring and hollow stem we are taking care of the crops N needs. Here is a link to a blog on reading the N-Rich Strips to get a N rate rec https://osunpk.com/2014/02/24/sensing-the-n-rich-strip-and-using-the-sbnrc/ and here is a link to one of my latest blogs on Timing of Nitrogen Application for Wheat https://osunpk.com/2018/10/01/how-long-can-wheat-wait-for-nitrogen/.

For more information please contact me at b.arnall@okstate.edu

 

Below is a Sunup TV video on the subject of Nitrogen Losses with the recent rains.

 

 

 

Planting Date and Seeding Rate Considerations for Winter Wheat

As the current weather pattern has this state headed to one of its wettest, if not the wettest, Aug-Sept-Oct on records, this is good information. As we start progressing towards November wheat seeding rate needs to be increased to compensate for lost tiller production. Keep in mind I have not done ANY research on seeding rate. After the mid Oct I bump my seeding rate to 70-75 lbs per acre. As we hit November I am in the 80s.

World of Wheat

With this August setting up similar to last year and the need for wheat pasture for a number of producers this fall, we will likely see drills start rolling in parts of the state by the end of the month. As planting gets going, here are a couple considerations when it comes to planting dates and seeding rates for Oklahoma winter wheat.

Planting date:

The optimal window for dual-purpose wheat for most of Oklahoma is between September 10-20 (approximately day 260 in Figure 1). This window represents a trade-off between maximizing forage production while minimizing potential grain yield loss. Earlier planting dates, last week into this week for example, will provide more fall forage potential, but this is usually not recommended unless the wheat is intended to be produced for grazing, or “grazeout.” Planting dates for grain-only producers will be at least 2-3 weeks later than what is the ideal…

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How long can wheat wait for Nitrogen?

Joao Bigatao Souza, PhD. Student Precision Nutrient Management
Brain Arnall Precision Nutrient Management Extension Specialist.

The N-rich strip method allows wheat producers a greater window of decision making regarding the application of nitrogen (N) fertilizers. Besides having greater accuracy in N rates than standard methods (based on the SBNRC – OSU) also helps to reduce costs in the production system and to preserve the environment avoiding over N applications.

With the experiments performed in the last two crop seasons (2016/18 and 2017/18), we can now be even more accurate with regard to the best application time to increase the N use efficiency by the crop. The objective of our study was to determine the impact of prolonged nitrogen deficiency on winter wheat grain yield and protein. Eight studies were conducted with 11 N application timings in no-till dryland conditions. A pre-plant treatment of 90 lbs ac-1 of N was broadcast applied as ammonium nitrate (AN). We used AN as our source because we wanted to measure the crops ability to recover and eliminate the impact of source efficiencies. When visual symptom differentiation (VSD) was documented between the pre-plant and the non-fertilized check, i.e the N-Rich Strip showed up, top-dress applications were performed every seven growth days (GDD> 0) (https://www.mesonet.org/index.php) until 63 growth days after VSD at all sites. The only N the treatments received where applied according to treatment structure. No preplant N was applied other than trt 1, and all locations had residual N under 15 lbs 0-6” sample.

The first visual response to fertilizer N ranged from November 11 to February 5 (Table 1). The soil can have residual N from the previous season which can supply the subsequent crop in the beginning of the development what makes the wheat not demonstrate any sign of stress in the early season. For example LCB2017 a and b which were located 100 yards apart but under a different point in the crop rotation (LCBa was wheat after wheat and LCBb wheat after canola) had a 30 day difference in date of first N response. This range in first and last dates allowed us to evaluate N application over a wide range of dates and determine whether the first sign of stress is actually the best indicator of top dress application timing.

Table 1 shows the planting date, date of first visual difference (0DAVD) and each of the application dates for all locations. Different colors represent individual months. Hollow stem occurred approximately Feb 20 in the 2017 crop and March 10th in the 18 crop.

 

Image of the 2016-17 Perkins location. Image collected March 21 2017.

As shown in the Tables 2 and 3 below only three of the 78 comparisons made back to the pre-plant application were significantly less in terms of grain yield. All three of these comparisons where from when N application was delayed until late March or April. When the delayed applications were compared to 0DAVD yields only two of the 68 comparisons showed a significant decrease on yield. One was the pre-plant application for LCB2017a while the other were the 63DAVD application for LCB2017b. In most locations applications made in March yields were at the highest point, however when delayed till April yield trends on the downward trend. The 2017 crop reached hollow stem (Feekes 6) around Feb 20th while the 2018 crop reached hollow stem around March 10th.

Grain protein concentration was decreased only once when compared to both the pre-plant and 0DAVD treatments. This one timing, LCB2018b 64DAVD, was the only application made in May. During this time the crop was in the early stages of grain-fill. In all locations delaying N application until February/March increased grain protein content above the check, and in most cases above the 0DAVD trt.

Tables 2-3 shows the winter wheat grain yield and protein concentration, respectively, of all treatments. The colors of the cells represent statistical difference from the Pre-plant treatment. Treatments with cells shaded yellow are equal to the pre-plant, Green is statistically greater than while red is statistically less than the pre-plant treatment.

 

2016-2017 Delayed nitrogen winter wheat grain yield and protein results. For the locations of Perkins and N40 the Dec-1 application has a higher yield due to a 2x application of N to equal 180 lbs.

 

2017-2018 Delayed nitrogen winter wheat grain yield and protein results. The Perkins location in 18 was the only location in the study which did not have a statistically significant response to added N.

All the data was combined and plotted by cumulative GDD’s>0 from planting (GDDFP) across all locations to determine a general “best” timing. Using the pre-plant application yield as a base there was no yield loss if the applications was made prior to the 143 GDDFP. When the results were normalized by 0DAVD N there was no yield loss if the applications were made prior to 130 GDDFP. The quadratic model created provides the opportunity to identify the point of highest grain yield, which was approximately 94 GDDFP. In terms of the relationship between the application of N based on GDDFP and % of protein content on the grain, a linear response of N delay application observed for grain protein concentration. Our results suggest that the later the application, the higher the protein % in the grains.

Growing degree days > 0 from planting and equivalent calendar days for all experimental sites (Lake Carl Blackwell, Perkins, Lahoma, Stillwater) utilized in the study evaluating the impact nitrogen fertilizer timing on winter wheat, conducted in north central Oklahoma over the 2016-2017 and 2017-2018 winter wheat growing seasons.

We have concurrent work looking at similar approaches with other sources of N such as Urea and UAN. While all of  these studies are being continued the past two years of work have presented some easy take homes.

First: Timing of N application does matter, but yellow wheat does not necessarily mean yield loss.
Second: Two years in a row ALL Nitrogen could be delayed until hollow stem without yield Loss, in fact yields of trts with N applied at this time typically better than that of the pre-plant.
Third: Protein content increased as N applications was delayed.
Fourth: The conclusions of this and other studies support that N-Rich Strip concept does not increase risk of lost yield.
Fifth: Applying the majority of the N at or just after hollow stem maximized grain yield and protein with a single shot.
Sixth and Final: Be more concerned about applying N in an environment conducive to increased utilization and less about applying at the first sign of N stress. Take a look at the wheat N uptake curve by K-State.The crop really doesnt get going in terms of N-uptake until jointing i.e. hollow Stem.

Wheat N-uptake. Figure adapted from Lollato et al.

Questions for comments fill free to contact me via email at b.arnall@okstate.edu

The challenge of collecting a representative soil sample

Guest Author, Dorivar Ruiz Diaz, Nutrient Management Specialist Kansas State University

At first glance, soil sampling would seem to be a relatively easy task. However, when you consider the variability that likely exists within a field because of inherent soil formation factors and past production practices, the collection of a representative soil sample becomes more of a challenge.

Before heading to the field to take the sample, be sure to have your objective clearly in mind. For instance, if all you want to learn is the average fertility level of a field to make a uniform maintenance application of P or K, then the sampling approach would be different than sampling for pH when establishing a new alfalfa seeding or sampling to develop a variable rate P application map.

In some cases, sampling procedures are predetermined and simply must be followed. For example, soil tests may be required for compliance with a nutrient management plan or environmental regulations associated with confined animal feeding operations. Sampling procedures for regulatory compliance are set by the regulatory agency and their sampling instructions must be followed exactly. Likewise, when collecting grid samples to use with a spatial statistics package for drawing nutrient maps, sampling procedures specific to that program should be followed.

 

Figure 1. The level of accuracy of the results of a soil test will depend, in part, on how many subsamples were taken to create the composite sample. In general, a composite sample should consist of 15 or more subsamples. For better accuracy, 20-30 cores, or subsamples, should be taken and combined into a representative sample. F

Regardless of the sampling objectives or requirements, some sampling practices should be followed:

  • A soil sample should be a composite of many cores to minimize the effects of soil variability. Take a minimum of 12 to 15 cores from a relatively small area (two to four acres). Taking 20-30 cores will provide results that are more accurate. Take a greater number of cores on larger fields than smaller fields, but not necessarily in direct proportion to the greater acreage. A single core is not an acceptable sample.
  • Use a consistent sampling depth for all cores because pH, organic matter, and nutrient levels often change with depth. Match sampling depth to sampling objectives. K-State recommendations call for a sampling depth of two feet for the mobile nutrients – nitrogen, sulfur, and chloride. A six-inch depth is suggested for routine tests of pH, organic matter, phosphorus (P), potassium (K), and zinc (Zn) (Figure 2).
  • When sampling a specific area, a zigzag pattern across the field is better than following planting/tillage pattern to minimize any past non-uniform fertilizer application/tillage effects. With a GPS system available, recording of core locations is possible. This allows future samples to be taken from the same locations in the field.
  • When sampling grid points for making variable rate nutrient application maps, collecting cores in a 5-10 foot radius around the center point of the grid is preferred for many spatial statistical software packages.
  • Avoid unusual spots obvious by plant growth and/or visual soil color/texture differences. If information on these unusual areas is desired, collect a separate composite sample from these spots.
  • If banded fertilizer has been used on the previous crop (such as strip tillage), then it is suggested that the number of cores taken should be increased to minimize the effect of an individual core on the composite sample results, and to obtain a better estimate of the average fertility for the field.
  • For permanent sod or long-term no-till fields where nitrogen fertilizer has been broadcast on the surface, a three- or four-inch sampling depth would be advisable to monitor surface soil pH

 

 

Figure 2. Consistency is sampling depth is particularly important for immobile nutrients like P. Stratification of nutrients and pH can be accentuated under reduced tillage.

Soil test results for organic matter, pH, and non-mobile nutrients (P, K, and Zn) change relatively slowly over time, making it possible to monitor changes if soil samples are collected from the same field following the same sampling procedures. However, there can be some seasonal variability and previous crop effects. Therefore, soil samples should be collected at the same time of year and after the same crop.

Soil test results for organic matter, pH, and non-mobile nutrients (P, K, and Zn) change relatively slowly over time, making it possible to monitor changes if soil samples are collected from the same field following the same sampling procedures. However, there can be some seasonal variability and previous crop effects. Therefore, soil samples should be collected at the same time of year and after the same crop.

Soil testing should be the first step for a good nutrient management program, but it all starts with the proper sample collection procedure. After harvest in the fall is good time for soil sampling for most limiting nutrients in Kansas.

For instructions on submitting soil samples to the K-State Soil Testing Lab, please see the accompanying article “Fall soil sampling: Sample collection and submission to K-State Soil Testing Lab” found in this eUpdate issue.

For any questions Contact.
Dorivar Ruiz Diaz, Nutrient Management Specialist
ruizdiaz@ksu.edu

 

How Does Soil pH impact Herbicides?

Misha Manuchehri and Brian Arnall

There are many factors that influence the persistence and uptake of a herbicide that has soil activity. One of those factors is soil pH or the amount of hydrogen (H) ions present in the soil solution. Some herbicides will persist for an extended amount of time or rapidly degrade when outside the pH window of 6.0-7.0.

The triazines (atrazine, simazine, etc.) and sulfonylureas (chlorsulfuron, metsulfuron, etc.) are two herbicide chemical families that are especially affected by soil pH (Table 1). The dinitroanilines, and the active ingredient clomazone also can be affected by low and high soil pH; however, degradation by light and/or volatility are more important when it comes to the activity of these herbicides. Generally, the triazines and sulfonylureas persist longer and are more available for plant uptake in higher pH soils (>7.0) while the opposite is true for imidazolinone herbicides (imazamox, imazapic, imazethapyr, etc.). Imidazolinones persist and are more available for plant uptake in lower pH soils (<6.0). The persistence of the triazines and sulfonylureas in high pH soils is a result of a decrease in chemical and microbial breakdown, a trend that is often observed in high pH soils where neutral herbicide molecules are loosely adsorbed to the soil and are more available for plant uptake. Conversely, in low pH soils, triazine and sulfonylurea herbicides become charged and are more tightly adsorbed to the soil where they are more susceptible to breakdown.

A key management factor that must be considered when evaluating a field’s soil pH is whether or not the field is no-till and for how long it has been in no-till. Tillage will impact how deep you should take soil samples to determine soil pH. In no-till and minimum tillage fields, the traditional method of 0-6 inch or 0-8 inch soil cores may not be adequate. Instead, a 0-2 inch core depth and a 2-6 inch core depth may be needed, since application of limestone to the surface may increase surface pH more than expected or application of nitrogen fertilizer to the surface may cause a drop in pH at the surface. In many long term no-till fields with historic surface applications of N and no lime applications, soil pHs in the low 4s have been observed while the 3-6” depth will be at a 6.0. Since herbicides with a soil residual are affecting plants just below the soil surface, this is the soil zone we are the most interested in.

Oklahoma and Kansas production fields can have a wide range of soil pH from field to field and within field. In a dataset of over 300 grid sampled fields from Oklahoma (259 fields) and Kansas (47 fields), the average field pH was a nice 6.0. However, the average range in the lowest and highest soil pH within the fields was 1.9. This means the average field had a pH range from 5.0 to 7.0. It should be noted that more than 25% of the fields had a pH range of 3.0 units. This range of highs and lows has helped explain the presence of spotty herbicide issues on several fields in the past and should be taken into account when planning crop rotations.

It is extremely important to know and understand the pH of your soils and the herbicides you plan to use and how they will react. Soil testing is the only way to know your soil pH and reading your herbicide label is a great way to learn if soil pH affects the herbicide you are applying.

Table 1. Herbicide chemical families or selected herbicides that are most affected by soil pH.

Herbicide chemical family or active ingredient

Common name (trade name) examples

Importance of soil pH

Soil pH considerations

Sulfonylureas

Chlorsolfuron + metsulfuron (Finesse C & F), metsulfuron (Ally XP)

Extremely

pH > 7a – persist longer and are more available for plant uptake

Triazines

Atrazine (AAtrex), simazine (prince)

Extremely

pH > 7 – persist longer and are more available for plant uptake

Imidazolinones

Imazamox (Beyond), imazapic (Plateau), imazethapyr (Pursuit)

Somewhat

pH < 6 – persist longer and are more available for plant uptake

aAcidic Soils < 5.5, Basic Soils > 7.5

 

Ag Apps, 5 Years Later

As I write this it does not seem possible that my first Ag App Blog was written over five years ago. https://osunpk.com/2013/07/30/agriculture-app-for-the-ipad-and-iphone/. When I wrote that first blog I had 76 apps on my iPad a year later I had over 200 apps on the same iPad posted the third app focused blog https://osunpk.com/2014/12/09/agriculture-apps-200-strong-and-growing/.

Today I still enjoy looking for apps and I am also having a lot of fun developing apps.  With a team of computer science students we have released twenty eight apps in both iOS and Andriod platforms http://www.dasnr.okstate.edu/apps.  After I had picked up a few new apps, broke the 300+ mark, I found that my five year old iPad 2 was not quite as quick as it used to be and I had to upgrade prior to doing my Scouting App Review https://osunpk.com/2017/08/03/scouting-app-review/.

Even after 300+ apps I still have a few of the same original suggestions, like the general rule of thumb “If I cannot figure it out in 3 minutes it’s GONE.  An app should be intuitive, easy to use and have a purpose.  They only exception to the 3 minute rule is the Scouting and Mapping Apps. Because of their complexity I allow them 5 minutes, and then I am done.  Any app with GIS in its name gets much more time”. As far as searching for apps terms such as Corn, Soybean, and Wheat return more games and dietary apps than useful ag apps.  Multiple key work searchers is important.  If you find a good app go into iTunes or Google Play and check out the other apps created by the developer. Chances are if the developer has made one app you like there will be other well suited to your needs.

App Information page in iTunes or Google Play

App Information page in iTunes or Google Play

See a list of all apps created by the developer.

See a list of all apps created by the developer.

 

 

 

 

 

 

 

 

But to be honest as you can expect of those 300+ apps 95% only get opened when I have to give a talk.  Recently I have had request to update my list of apps but instead of spending the countless hours organizing my thoughts on the 300+, I decided on just sharing with you those apps which have made their way onto my cell phone because I do use them. Many of these are on my original blog 5 years ago.

TANK MIX CALC  Apple   Andriod

Tank Mix Calculator by Farm Logic

Tank Mix is a handy app that allows the user to create chemical inventories, plan spray jobs, share the details and save for later.  Minus wading through the list of chemical this is a very intuitive app and provides a great deal of information. The ability to create a library of chemical and application really streamlines the systems.

SPRAY SELECT      Apple

Spray Select by TeeJet

Spray Select was the first app I downloaded.  While over the years it has had its fair share of bugs, in my line of work this app is a gem. In a day I may go from spray a contact, to a fertilizer, to a systemic.  Not to mention the wide range of GPAs I run at.  Being able to to select my speed and GPA then have a list of tips and droplet sizes makes this app critical for my project. I primarily use TeeJet but if you use Hypro check out AgPhDs SprayTipGuide, if you use Greenleaf download NozzleCalc, JohnDeere has an app for their nozzles also.

FERTREMOVAL     Apple    Andriod

FertRemoval by AgPhD

I have two Nutrient Removal Calculators on my iPhone the Fert Removal from AgPhD and Nutrient Removal from IPNI.  I give Fert Removal the leg up because it provides nutrient values for more than just the macro nutrients.

DEFICIENCIES      Apple    Andriod

Deficiencies by AgPhD

The AgPhDs put out another nice app in Deficiencies. Nice funcitonality but image library is a bit limited. It is my hopes that they are adding to this over time. Much like with the nutrient removal tools I give second runner up in this group to the IPNI PlantImages app. It has a larger image data base but at the time of this blog it needs updating and is not functioning on all platforms. Both apps are on my phone and are great tools for someone new in the field, or someone who has been around a while but who’s client needs to a see a second opinion.

CORNYIELDCAL      Apple    Andriod     Crop Calculators  Apple  Andriod

Corn Yield Calculator by Kinetic Thoughts

I like the easy of use for of the Corn Yield Calculator. It is a quick, easy, and clean way to estimate yield.  However when I pulled the links for this app it seems as though since I first downloaded the app, a fee has been added, $2.99. For some of you it may be worth the charge. However University of Wisconsin has a nice app named Crop Calculators. It has several functions but the UI (user interface) is not as clean.

HARVESTLOSS    Apple    Andriod

Harvest Loss by AgPhD

Another app by the Ag PhDs is on my list.  For me the Harvest Loss App is what I use as an example for the perfect “app”. Harvest loss allows the user to choose the commodity and current price. Then the number of grains found in a square foot after harvest is counted. This provides an economic value to properly setting a combine. What more powerful tool than money lost is there to impact change.

IDWEEDS UM  Apple    Andriod    WeedID Monsanto   Apple    Andriod

ID Weeds by University of Missouri and Monsanto

These are not the only Weed Identification apps, but they are my favorite. University of Missouri’s IDWeeds was the first of its kind and has made some fantastic improvements over the years. Monsanto’s WeedID app is, IMHO, one of the cleanest and nicest user interfaces available. Both function similarly, the user selects grass or broadleaf, then chooses the appropriate physiological features of the weed in question. A list of weeds fitting the description is compiled. Pictures and more in-depth descriptions are available.

DISEASEID      Apple

Disease ID BASF

While this app is built for the UK, being in the southern Great Plains wheat is king and this is a very useful app when it comes to cereal disease. While it does not have a good ID tool it has a great list of diseases, images and very in-depth descriptions.

COWPOOPANALYZER      Apple

Cow Poop Analyzer by Texas A&M AgriLife Extension Service

This app just makes me smile. But it really does have some great features and could be quite useful or any cattle producer. By considering the consistency of the pile the quality of the forage/feed can be estimated.

SHAMELESS PLUG

Apps released by OkState Division of Ag and Natural Resources. See full list at http://www.dasnr.okstate.edu/apps

Of course I have all of the OSUNPK apps on my  phone but here are a few that I think were homeruns. The full list can be found at http://www.dasnr.okstate.edu/apps 

CANOPEO

Canopeo

While Canopeo is not mine its the best thing since sliced bread. This app uses the camera on your phone or tablet to get a % canopy cover. The Android version even has a video version. The applications for this app are endless.

OKSTATE SOIL SAMPLE

OKState Soil Sample App

Designed for individuals who send samples to the OSU Soil, Water, and Forage Testing Labs (SWFAL). User can collect the GPS location of a sample, add notes, and tie it to your lab ID and sample number via a barcode. I know some who just use this app to get Lat Longs from sample points. At this point the app is not tied to the Lab system. But a file can be emailed with all of the saved data.

IRRIGATION

Crop Nutrients in Irrigation Water Calculator

Simple calculator that will calculate annual nutrient additions when you have a irrigation water test.

GRAINDRILLCALC

Grain Drill and Planter Calibration Calculator

Handy app built to help calibrate grain drills to sow canola with the added function of determining rates of other grains and fertilizers.

FOODPLOTS

Wildlife Food Plot Apps

Non Ag but extremely popular app designed for a DIY food plot. Pick your species of interest and planting window and a list of applicable plants and their agronomic recommendations are provided. Lists can be saved and shared.

PLOTCALC

Plot Calculator

Built to help graduate students prep fertilizer for plot application. The app also has a unit conversation calculator.

If you are free in the middle of July, make your way to InfoAg in St Louis (July 17-19, 2018). I will be going through these app and many more in a app review and demonstration. For more info on InfoAg check out their website. https://infoag.org/ 

Questions for comments fill free to contact me via email at b.arnall@okstate.edu

Soil sampling for pH and liming in continuous no-till fields

Quest Author, Dorivar Ruiz Diaz, Nutrient Management Specialist Kansas State University

One question that commonly comes up with continuous no-till operations is: “How deep should I sample soils for pH?” Another common question is: “How should the lime be applied if the soil is acidic and the field needs lime?”.

Sampling depth in continuous no-till

Our standard recommendation for pH is to take one set of samples to a 0-6 inch depth. On continuous no-till fields where most or all of the nitrogen (N) is surface applied, we recommend taking a second sample to a 0-3-inch depth. We make the same recommendation for long-term pasture or grass hayfields, such as a bromegrass field that has been fertilized with urea annually for several years.

Nitrogen fertilizer is the primary driving force in lowering soil pH levels, so N application rates and methods must be considered when determining how deep to sample for pH. In no-till, the effects of N fertilizer on lowering pH are most pronounced in the area where the fertilizer is actually applied. In a tilled system, the applied N or acid produced through nitrification is mixed in through the action of tillage and distributed throughout the tilled area.

Where N sources such as urea or liquid UAN solutions are broadcast on the surface in no-till system, the pH effects of the acid formed by nitrification of the ammonium will be confined to the surface few inches of soil. Initially this may be just the top 1 to 2 inches but over time, and as N rates increase, the effect of acidity become more pronounced, and the pH drops at deeper depths (Figure 1). How deep and how quickly the acidity develops over time is primarily a function of N rate and soil CEC (cation exchange capacity), or buffering capacity.

Where anhydrous ammonia is applied, or liquid UAN banded with the strip-till below the surface, an acid zone will develop deeper in the soil. As with long-term surface applications, these bands will expand over time as more and more N fertilizer is placed in the same general area. The graphic below (Figure 1) illustrates the effect of repeated nitrogen and phosphorus application with strip-till in the same area in the row middle on a high CEC soil for more than 12 years.

Figure 1. Soil pH stratification after 25 years of no-till and surface nitrogen fertilizer application, and the effect of repeated fertilizer application with strip-till in the same area after 12 years.

Liming application methods in continuous no-till

Where do you place the lime in continuous no-till?

If you surface apply N, then surface apply the lime. That’s a simple but effective rule. But remember that surface-applied lime will likely only neutralize the acidity in the top 2-3 inches of soil. So if a producer hasn’t limed for 20 years of continuous no-till and has applied 100 to 150 pounds of N per year, there will probably be a 4-5 inch thick acid zone, and the bottom half of that zone may not be neutralized from surface-applied lime. So, if a producer is only able to neutralize the top 3 inches of a 5-inch deep surface zone of acid soil, would that suggest he needs to incorporate lime? Not really. Research has shown that as long as the surface is in an appropriate range and the remainder of the acid soil is above pH 5, crops will do fine.

Liming benefits crop production in large part by reducing toxic aluminum, supplying calcium and magnesium, and enhancing the activity of some herbicides. Aluminum toxicity doesn’t occur until the soil pH is normally below about 5.2 to 5.5 and KCl-extractable (free aluminum) levels are greater than 25 parts per million (ppm). At that pH the Al in soil solution begins to increase dramatically as pH declines further. Aluminum is toxic to plant roots, and at worse the roots would not grow well in the remaining acid zone.

This implies that the acid zones from ammonia or banded UAN are probably not a major problem. We have monitored ammonia bands in the row middles of long-term no-till for many years and while the pH dropped very low, we never saw any adverse impacts on the crop that would justify liming and using tillage to incorporate the lime. In fact, some nutrients such as zinc, manganese, and iron can become more available at low pH, which can be an advantage at times.

Yield enhancement is not the only concern with low-pH soils, however. Herbicide effectiveness must also be considered. The most commonly used soil-applied herbicide impacted by pH is atrazine. As pH goes down, activity and performance goes down. So in acidic soils, weed control may be impacted. We do see that happen in corn and sorghum production.

Liming products for no-till

When choosing a liming product, is there any value to using dolomitic lime (which contains a large percentage of magnesium in addition to calcium) over a purely calcium-based lime product?

Most Kansas soils have high magnesium content. So as long as we maintain a reasonable soil pH, there normally is enough magnesium present to supply the needs of a crop. Calcium content is normally significantly higher than magnesium, so calcium deficiency is very, very rare in Kansas. The soil pH would need to be below 4.5 before calcium deficiency would become an issue. Before calcium deficiency would occur, aluminum toxicity or manganese toxicity would be severely impacting crop growth. So producers really don’t have to worry about a deficiency of calcium or magnesium on most Kansas soils.

What about the use of pelletized lime as a pH management tool on no-till fields?

The idea has been around for a while to use pel-lime in low doses to neutralize the acidity created from nitrogen and prevent acid zones from developing. . Pel-lime is a very high-quality product, normally having 1800 to 2000 pounds of effective calcium carbonate (ECC) per ton, and can be blended with fertilizers such as MAP or DAP or potash easily. Therefore, if you apply enough product this can be an excellent source of lime. Lime can be from various sources and with different qualities. Consecutively, to ensure a standardized unit of soil-acidity neutralizing potential, we use units of ECC.

Summary

Applying N fertilizer to soil will cause the soil to become acidic over time. Placement of the applied N and the level of soil mixing done through tillage determine where the acid zones will develop. Make sure your soil testing program is focused on the area in the soil becoming acidic, and apply the lime accordingly.

 

For any questions Contact.
Dorivar Ruiz Diaz, Nutrient Management Specialist
ruizdiaz@ksu.edu