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Freeze Injury and N-Rich Strips,
Dr. Jeff Edwards “OSUWheat” wrote about winter wheat freeze injury in a receive blog on World of Wheat, http://osuwheat.com/2013/12/19/freeze-injury/. As Dr. Edwards notes injury at this stage rarely impact yield, therefore the fertility requirements of the crop has not significantly changed. What will be impacted is how the N-Rich Strip and GreenSeeker™ sensor will be used. This not suggesting abandoning the technology in fact time has shown it can be just as accurate after tissue damage. It should be noted GreenSeeker™ NDVI readings should not be collected on a field that has recently been damaged.
A producer using the N-Rich Strip, GreenSeeker™, Sensor Based N-Rate Calculator approach on a field with freeze damage will need to consider a few points. First there need to be a recovery period after significant tissue damage; this may be one to two weeks of good growth. Sense areas that have had the same degree of damage as elevation and landscape position often impacts the level of damage. It would be misleading to sense a area in the N-Rich strip that was not significantly damaged but an area in the Farmer Practice that took a great deal of tissue loss.
Finally we must consider how the SBNRC, available online at http://nue.okstate.edu/SBNRC/mesonet.php, works. The calculator uses NDVI to estimate wheat biomass, which is directly related to grain yield. This predicted grain yield is then used to calculate nitrogen (N) rate. So if biomass is reduced, yield potential is reduced and N rate reduced. The same issue is seen in dual purpose whet production. So the approach that I recommend for the dual purpose guys is the same that I will recommend for those who experienced significant freeze damage. This should not be used for wheat with just minimal tip burn.
To account for the loss of biomass, but not yield, planting date needs to be adjusted to “trick” the calculator into thinking the crop is younger and has greater potential. Planting date should be move forward 7 or 14 days dependent For example the first screen shot shows what the SBNRC would recommend using the real planting date. In this case the potential yield is significantly underestimated.
The second and third screen shots show the impact of moving the planting date forward by 7 and 14 days respectively. Note the increase in yield potential, which is the agronomically correct potential for field considering soil and plant condition, and increase in recommended N-rate recommendation. Adjust the planting date, within the 7 to 14 day window, so that the yield potential YPN is at a level suitable to the field the yield condition and environment. The number of days adjusted is related to the size and amount of loss. The larger the wheat and or greater the biomass loss the further forward the planting date should be moved. In the example below YPN goes from 37 bu ac on the true planting date to 45 bu ac with a 14 day correction. The N-rate changes from 31 lbs to 38 lbs, this change may not be as much as you might expect. That is because YP0, yield without additional N, also increases from 26 to 32 bushel.
Image 1. Planting date 9/1/2013. YPN 37 bu ac-1 and N-Rec 31 lbs ac-1.
Image 2. Planting date 9/8/2013. YPN 40 bu ac-1 and N-Rec 34 lbs ac-1.
Image 3. Planting date 9/15/2013. YPN 45 bu ac-1 and N-Rec 38 lbs ac-1.
This adjustment is only to be made when tissue has been lost or removed, not when you disagree with the yield potential. If you have any questions about N-Rich Strips, the GreenSeeker™, or the online SBNRC please feel free to contact me at b.arnall@okstate.edu or 405.744.1722.
Ag Apps Updated
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.
Ag News/Weather/Markets
Not much change in this group however I have added one or two.
Scouting/Mapping
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.
Record Keeping,
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.
ID Tools,
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,
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.
Calculators,
Only two apps has been added to this category. I am still using Fert.Removal, HarvestLoss and Growing Degrees on a regular basis.
Sprayer/Chemicals,
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.
Fertilizer,
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.
Seed Select,
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.
Freeze injury
Our recent extreme shifts in temperature have resulted in moderate to severe freeze injury in some Oklahoma wheat fields. To be honest, the damage is not as widespread or severe as I thought it would be given that most of our wheat had not had an opportunity to harden off. The dry soil conditions in western and southern Oklahoma did not help the situation, as there was not sufficient soil moisture to buffer the temperature shift in the top few inches of soil.
Freeze injury at this stage of growth (tillering) rarely impacts grain yield, but, as always, there are a few exceptions. Wheat that was very small or late-sown is more susceptible to winter kill. Similarly, wheat that does not have a good root system or that was shallow sown due to crop residue is more susceptible to winter kill. It is best to wait until after a few…
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Down and Dirty with NPK 