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Vaughn Reed, PhD. Student Precision Nutrient Management
Brain Arnall Precision Nutrient Management Extension Specialist.
Data presented below are the results of Mr. Reeds Masters research project.
On farm research trials are important, because they give us the ability to see responses over a larger geographic area, and even more importantly, evaluate our recommendations on fields that are managed by producers, not researchers. They also allow us to look at current production practices and see if there are any missed opportunities. Several years ago, we looked at whether producers were leaving yield on the table by not applying enough nitrogen (N), phosphorus (P), potassium(K), and sulfur (S) to winter wheat. We did this by applying strips of N, P, K, and S fertilizer on farmers’ fields with the instructions to not change their fertilizer management strategies. If one or more of the strips resulted in higher yields then it could be assumed that either the nutrient was under-applied by the producer, or in the case of N, lost. That study concluded that at 75% of the locations, yield was maximized by the producer with [their respective] NPKS management system, however the greatest responses came from the addition of P and that Oklahoma State University’s soil testing and analysis was adequate for nutrient recommendations. That studies results were published in 2017 and is open access, so available for anyone to read. https://dl.sciencesocieties.org/publications/cftm/abstracts/3/1/cftm2017.02.0014
There are many producers around the state that follow winter wheat with double crops (DC). Often, this practice is done with limited inputs to reduce economic risk. Oklahoma State does not make different recommendations for DC or full season crops, with the exception that yield potentials can differ. In 2016 and 2017 we duplicated the Wheat NPKS study across 3 double crops (soybean, grain sorghum, sunflower) following winter wheat and canola. With a recent climb in DC yields we wanted to investigate if producers were applying enough nutrients to maximize grain yield. Additionally it would allow us evaluate the accuracy of OSU’s soil test based fertilizer recommendations in a double crop. Over the two years, 61 on-farm sites ranging from central to NE Oklahoma had 200 lb/ac of product per nutrient applied in strips 6ft wide by 150 ft long. Urea (46-0-0), triple super phosphate (0-46-0), muriate of potash (0-0-60), and gypsum (0-0-0-19) were used for sources N, P, K, and S, respectively (92 lbs N, 92 lbs P, 120 lbs K, 38 lbs S). In most cases the fertilizer was applied post planting and post-emergence to ensure strips were applied an areas with good stand.
Much like with the wheat-NPKS study 75% of the locations did not respond to additional fertilizer. Twenty treatment comparisons of the 244 made across all 61 locations (50 soybean, 7 grain sorghum, 4 sunflower) yielded a statistically significant change in yield due to the addition of N-P-K-or S. For this report, a comparison was the yield of each nutrient versus the non-treated check, therefore there were four comparisons made per location. Seventeen of the twenty positive responses were found in soybean, three with grain sorghum, and no responses were found in sunflower plots. Lack of response from grain sorghum and sunflower locations is contributed to small amount of grain sorghum and sunflower fields in the study.
Nitrogen rates, for non-legumous crops, are yield driven, meaning the higher yielding a crop, the higher amount of N required. Both grain sorghum and sunflower crops, due to neither being legumes, were expected to see N response, especially to those locations that applied little to no N to begin with. A yield response from the addition of N was found in one grain sorghum location, where the producer application was not enough to maximize yield, and the additional N pushed the yields. As expected, there were no soybean locations that responded to the addition of N.
Phosphorus and potassium are both sufficiency based, not yield driven. This means that if the soil is at 100% sufficiency, the crop will produce at its highest rate achievable, based on that nutrient. 100% sufficiency for P and K are approximately 65 STP and 250 STK, respectively. Phosphorus and potassium strips yielded the most results, especially in soybean locations. Of 20 responses, five responses were due to P, ten due to K, and four due to S. Locations that responded to the addition to P were locations that either had low levels of STP (approx. 80% sufficiency or less), or had low pH, which leads to less availability of P (pH>5.0).
Potassium yielded the most positive results, with ten responsive locations, as well as the most interesting results, with only three sites falling below 100% sufficiency. The other responses were attributed to having low Cl levels (Cl, as in Chloride, which while responses are rare, is a necessary nutrient, and sometimes can lead to losses in yield, especially in sandy environments), as well as drought stress conditions. Potassium has been shown to have a vital role in nutrient uptake and water retention, as it is found to be critical for root growth, and these are displayed highest in crops found in drought like conditions. One hypothesis for the K response is related to root growth. The later planted DC will spend less resources in root development before going reproductive. Soybean is a heavy user of K, combine smaller roots, typically hot drier soils, and high K demand it is not surprising to find this occurrence.
Sulfur, while not wide-spread reported in Oklahoma, has recommendations by OSU built on a yield driven scale. There were four responsive locations found in this project. While one location had low soil test S values there were located areas that received high rainfall events during the growing season, and therefore the response was attributed to leaching of S.
So, after all that, what is the bottom line? Here is our observations:
- Producers maximized yield 75% of the time, with 25% of locations responding to any additional nutrient.
- The 20 responses to additional nutrients occurred across 15 locations, four locations had responses to more than one nutrient
- By nutrient: Note for P and K, due to site variability it was not expected to observe statistic yield increase due to P or K unless soil test was below 70% sufficiency, of which no location had soil test P or K below 70%.
- 38 locations were below 100% sufficiency of phosphorus, with five observed responses
- Seven locations were below 100% sufficiency of potassium, two observed responses. An additional eight locations responded that were not predicted by soil test
- Based on pre-plant soil test there were no sites expected to respond to the addition of Sulfur, 4 locations did respond.
- Soil test results were adequate in correctly identifying locations that would not respond to the addition of nutrients (93.5% accurate), while not as accurate at predicting sites that would respond.
- For K, soil testing was less accurate, as eight of the ten responsive locations had soil test values above 250 soil test K (125 ppm or 100% sufficiency). For this reason, we are currently doing work evaluating K recommendations for soybeans.
This work confirms that of the fields we evaluated, the majority was not yield limited by N, P, K or S. However, as with anything, we have more work to do in order to further refine our recommendations, and always looking to learn more about how to aid producers.
In the spring of 2014 we initiated what was to be the first year of a three year project evaluating starter fertilizers for soybean production in the southern Great Plains. The first and second year was and is being funded by the Oklahoma Soybean Board.
Year one was a bit experimental in that with so many products on the market we needed some initial work to help focus the direction for years two and three. I also added a treatment which I knew would have significant negative impact, for extension reasons. Keep in mind two locations in a single year does not make an experiment nor provide enough information to draw a definite conclusion. It is however enough to learn some lessons from and for us to plan for our 2015 trials.
The 2014 trial consisted of 12 treatments, Figure 1 and Figure 2. In these treatments I wanted to see the impact of a standard practice, see if a specific nutrient may be more so beneficial, and evaluate a few popular products. The spring of 2014 started out dry so at one of our two locations we pre-watered. This was done by hauling water to the Lake Carl Blackwell (LCB) 1000 gallons at a time and pumping through sprinklers. The other site, Perkins, we delayed planting until we had moisture.
The two locations were also selected due to differences in soil fertility. The LCB site is has good soil fertility, with exception of phosphorus (P), and the Perkins site pH was an issue. I would have expected a benefit from adding P at both of these locations. Figure 4 shows the soil test results.
At LCB as expected some of the treatments (Thio-Sul) reduced stand, some unexpectedly reduced stand (Fe) and others had less impact on stand (APP 5.0) than expected. The growth at LCB was tremendous, the 30 in rows covered over very quickly and the majority of the treatments hit me waist high by early August (I am 6’0”). Many of the treatments showed greater growth than check. But when it comes down to it, grain pays and green does not. Statistically there were no treatments that out preformed the un-treated check, however the K-Leaf and 9-18-9 did make 3 and 2 bpa more than the check respectively. What I am hypothesizing at this site is that the added nutrients, especially those with high P levels, significantly increased vegetative grown and these big plants were delayed into going reproductive and they started setting pods later in much hotter weather. While riding in the combine I could see that the plots with compact plants with clearly defined rows out yielded those were the vines had crossed over and we harvested through more of a solid mat of mature plants. A hot August is not uncommon and I am curious on whether this trend repeats itself. If it does this may direct us into research evaluating ways to force/promote the reproductive stage to start in these big plants. Even if we can force flowering to start earlier, it’s unknown whether yields will increase or not.
The same trends in treatments reducing stand can be seen at Perkins, however the impact was less extreme. Perkins being planted later due to waiting on moisture forced a later flowering date and I believe reduced overall yields. But the addition of P at this low pH site definitely made a difference. While again no treatments were statistically greater than the un-treated check the 2.5 gpa APP, DAP broadcast, APP/H2O, and Pro-Germ/H20 treatments increased yield by 5.6, 4.2, 3.8 and 1.7 bpa respectively.
Take home from year one was that at LCB the addition of a starter fertilizer had little benefit and if done wrong could cost you yield while at the low pH site of Perkins an addition 2.5 gallons of APP did get a 5 bpa bump, but do to variability in the trial the increase was not statistically significant. This year we will drop some of the treatments and incorporate a few new treatments. Based on the current weather we look to potentially being able to start with better soil moisture at planting. Again do not take this work and significantly adjust any plans you have for your 2015 soybean crop. This is however some interesting findings that I wanted to share and make everyone aware of. Finally thank you to the Oklahoma Soybean Board for providing funding for this work. www.oksoy.org/
It was just 11 months ago when I wrote my last blog on Ag apps. Since that time I have presented on the topic several times, added nearly 100 new apps, have filmed several designated segment on sunup featuring apps (these can be seen at http://www.youtube.com/osunpk), and released two (soon to be three) apps myself. Below is the introductory slide I have been using in all of my app talks, on this slide you can see how the number of apps have been increasing overtime. In this update I wanted to share some of the new sections I have added to manage the vast number apps and go through some of my favorite apps in each of the sections.
Finding the right app has not changed as I still just give an app 3 minutes before a keep or drop decision is made, however since a year ago some of the key words are now less useful. For example a search for wheat will bring up droves of gluten free diet apps. None of these fit the bill for what I am looking for. Though out the blog you can click on pictures screenshots to get a better view of the app buttons.
Ag News and Weather
Still a very large section with little change for my recommendations, just go with what suits you in layout and reporting. I personally use RonOnRON (Ron Hays, the voice of Oklahoma Agriculture), DTN/PF, AG/Web, and AgWired.
This includes peer review publications, resource guides and extension materials.
The majority of the Calculator apps preform relatively simple functions without the need of cellular or wifi connectivity. The Ag PhDs have two apps in the section I want to highlight, HarvestLoss and Fert. Removal. Both apps are useful tools in making management decisions. HarvestLoss allows the user to calculate the economic loss of a poorly set combine while Fert. Removal allows the user to select from a wide range of crops and see an exit ate of nutrient removal based upon selected yield level. Other useful apps are Growing Degree which allows the user to see cumulative heat units a crop has received anywhere in the US, Corn Yield Calc estimates corn yield based on ear girth and length, Canola Calc is a great apps produced by Pioneer which calculates the proper planting rate of canola based upon several factors and the Kansas Wheat Yield Calculator KWYC, uses growth stage stalk counts, height and/or NDVI to estimate potential grain yield.
This section is filled with University Extension handbooks such as Purdue’s Field Guide ($12.99), University of Arkansas Corn Advisor, University of Kentucky Corn Production, and one private groups MFA Agronomy. Each of these guides are quality apps and should be chosen based upon geography or personal preference. The university apps mirror their respective hard copies however UK’s app added a nice update section highlighting local Ag news. MFA’s app is strong in pesticides with good herbicide performance data.
For any producer who regularly applies animal waste the Manure Calc by the University of Nebraska is a great tool. The University of Wisconsin has a nice app in N Price Calculator and the Saskatchewan Soil Conservation association (SSCA) has created a nice fertilizer blend app. Oklahoma State University has Ammonia Loss Calculator which uses soil pH and environmental conditions to estimate N losses from surface applied urea.
I am also getting into the app game with two recently released apps the Canola Starter and Field Guide. Canola Starter provides a recommendation for safe starter rates based on row width and fertilizer source. Field Guide is app version of my Nutrient Management Field Guide, this app includes a nutrient removal calculator, nutrient deficiency ID tool, and fertilizer rate calculators. Along with these I have several in the wings with titles like Crop Nutrients in Irrigation, GDDs>0, and Wildlife FoodPlot.
As mentioned in my first two blogs the University of Missouri’s IDWeeds app was the first taxonomy based weed identification tool. I still use it regularly but both BASF and Monsanto have brought products to the table, both named WeedID, that are very user friendly and effective. Plant Images ($5.00) is a library of nutrient deficiency photos from a large selection of crops. Years and Ag PhDs also have apps available with deficiency images named Yara Checkit and Crop Nutrient Deficiencies. Cereal Disease ID app by BASF is intended for the UK and DuPonts Pestbook for Australian cotton farmers but I find that both can be very useful even in Oklahoma.
Pay to Play, Registrations
I have heard several good things about many of these apps. However they reguire the user to either be an employee or patron of the company or online registration. In a pay to pay app I would expect an all inclusive tool that could replace several free apps and preform record keeping duties.
To be honest this is not a section I use much as I do not have an operation to maintain records on. However just by walking through the apps Crop Calculator by the University of Wisconsin and Pesticide Recordkeeping (PeRK) by University of Nebraska.
This section has apps that I classify as decision aid tools that could be used by someone scouting crops and apps that can be used to map and or collect field notes. South Dakota State has two great tools in Soy Diseases and NPIPM Soybean Guide. Scout and Sirrus.
Company based, Pioneers app products are some of the best with Plantability and Estimator
Some things haven’t changed I still use Tank Mix Calc and Spray Select on a very regular basis. But over the past year a few companies have added product finders and Clemson University has released a very nice sprayer calibration app named Calibrate.
The last two apps are Mesonet and Climate Corp Basic. You will notice the background on the screen shot is slightly different. That is because neither of these apps is kept Ina folder, both are on my home screen. Whether it is rain, temp, or wind weather impacts all aspects of agriculture therefore these two apps are always within one tap. For any producer in Oklahoma the Mesonet is an amazing system with 120 automated weather stations spread evenly across the state. This app just provides this data with just a few swipes of the finger. For those outside of Ok Climate Basic allows producers to first save field of interest and then monitor rainfall and environmental conditions of each field. While not extremely accurate it is defiantly close enough for those with a wide territory to be a very handy app.
For more information and some screen shots of the apps in action either visit my website http://npk.okstate.edu/presentations or my YouTube site http://www.youtube.com/osunpk under the playlist OSU_NPK on Sunup.
Since my Ag App post in July I have presented on the topic an additional five times and have two more on the books for 2014. A good thing about doing talks is that you have to update the information to remain current. Which in all honesty, when it comes to technology of any kind this is quite challenging and even more so for Smart Phone Apps. In July when I first blogged on the subject I had 76 apps on my iPad. Today (1.3.14) I have 111 apps on my iPad, for both the iPhone and iPad, that I deem to be Ag related. Since the summer I have found new favorites, changed some, and added categories but for the most part I still maintain my 2 minute rule stated in the first blog. I have allowed a bit more leniency in that I now say “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” I guess I am just getting soft.
Again I must make the obligatory statement; I am not a developer, designer, or expert. I am just a user who has had a chance to look at a few apps. Almost all of the apps I have are free and I am sure I have missed a few. Please share those with me. I am also not discussing Mobi’s, this is another large group of quality decision aid tools. I am also not discussing none apples apps. This is not because they are not relevant or important, it is because I do not have that technology.
I now have nine Ag folders on my iPad:
Ag News/Weather/Markets, Scouting/Mapping, Record Keeping, ID Tools, Crop Tools, Calculators, Sprayer/Chemicals, Fertilizer, Seed Select.
Apps are nice because the majority are stand alone and do not need internet or cell connection. This means they can be used when you are in the middle of nowhere, which is a great deal of Oklahoma, and have no service. This will exclude many of the Ag News/Weather/Markets, Scouting/Mapping, and Record Keeping apps that need positioning or location information.
Now let’s discuss some of the new and old apps.
Not much change in this group however I have added one or two.
This category has changed the most. Record keeping apps have been removed and several new apps added. The only free apps which can create boundaries are still Scout and Sirrus. To date Scout remains to be my favorite app for in field scouting notes. Pictures tagged with Lat Long and a note is very useful. My knock on is app is its boundary creation. It is a challenge every time as it is hard to remember the steps and not make a mistake. That is where Sirrus comes to play, by far the best boundary creation app. Sirrus has easy to use tools for both point and pivot boundaries. I like the edit vertex zoom in tool that resembles a rifle scope. I was able to add 12 fields in a matter of 20 minutes. Being able to create grid soil sampling scheme and record samples is also a very nice tool. My favorite part of the app, the UNDO button, and all apps should include this. The drawback to Sirrus is that it has no ability to take notes such as Scout. An additional nice scouting tool is South Dakota States NPIPM (North Plains IPM) app. This app provides not only a pest id tool with morphological drop down, I will discuss this in the ID Tools cat, but also management recommendation for the identified insect.
The majority of the apps in this category are “Pay to Play”, which makes since as they deal with data management and storage. Many would also fit the Scouting/Mapping category. As I do not pay for many apps I do not have experience with any of these. However this is the category that I would recommend any group to look at as they should be the all-inclusive app. However, PeRK by the University of Nebraska is a free app designed for field records of pesticide applicators.
I have added a few apps to this category but my favorites have not changed. I regularly use Plant Images, ID Weeds, and the Pestbook as references. I will add more discuss to app ID tools. The importance of being able to ID weeds and Pest via morphological drop down menus (ID Weeds and NPIPM) is extremely important. Many of the ID tools just have pictures and names. Well is I am using an ID Tool I likely do not know what I am looking at or what it is called.
Crop Tools includes my second “Paid in Full” app. And this one hurt a bit more. Not because it cost money but because I have multiple versions of the hard copy. However Field Guide by Purdue is one of my most recommended apps. Field Guide is the electronic version of the Purdue Corn and Soybean Field Guide, which the majority of consultants in the Corn Belt likely have this sitting in their truck. The Stoller apps also have nice very nice image bank of plant developmental phases. FieldGuide and CornAdvisor, another good app, are great examples of what I expect to be coming out of the majority of the Land Grant Universities very soon. Cooperative Extension has hundreds if not thousands of quality hard copy publications just waiting to be turned in to handy dandy apps. To be honest I am working on turning my Nutrient Management Field Guide into an app right now.
Only two apps has been added to this category. I am still using Fert.Removal, HarvestLoss and Growing Degrees on a regular basis.
Many apps have been added to this group but none of them have been good enough to kick TankMixCalc and SpraySelect of my favorites list.
Similar to the Sprayer/Chemicals category several apps have been added to this group, including several from Ok State. For me the Fert Cost Calc is still very useful. I do not get to use the Manure Calc I am very impressed by its layout and user friendliness. This app allows for applicator calibration, nutrient recs and manure value estimator.
It is no surprise the apps in this category are company created. I will say for the central Great Plains Pioneer’s Canola Calc is very useful tool for selecting canola planting rate providing input for row spacing live plants, seed weight, Germ percent, and survival percent.
To wrap up this blog I want to share with you may new Favorite none ag app. Bump is a huge time saver for anyone who takes pics with your iPhone or iPad. Bump allows easy transfer between mobile devices but more importantly between your mobile device and desktop by a simple tap of the space bar. This file share will go both directions. This means no more emailing pictures from your phone so that you can have them on your desktop. Bump is a iPhone app that can work on the iPad.
When searching with an IPad, remember to switch the search to include IPhone apps, there are some good ones out there that are IPhone only. Check out www.npk.osktate.edu/presentations to see screen shots from many of my favorite apps.