Soil Phos Building. How Much is Enough?

There has been a lot of discussion in ag circles in the last couple of years about phosphorous removal in soils. There is good reason for this. Yields have been high and crop fertility practices are pushing ever harder to maximize yield potential. Nitrogen has been the focus of this push for the most part, and in many if not most cases applied phos has not been scaled up in kind. The ratio of P removal vs P replacement has not been balanced.

There is an inverse relationship between the phosphorous supply of a given soil and the responsiveness of the same soil to applied P. Soil P supply has therefore diminished in these soils that have been “mined”. The responsiveness to applied P would therefore tend to be higher and higher after each year that P removal exceeds replacement.

In my many years of providing crop fertility service, I have consistently observed that the best yielding fields tend to be soils rich in phosphorous – in other words high soil P supply (therefore tend to be *less* responsive to applied P). Targeting low P supply fields for phosphorous building is therefore a smart thing to do to build soil productivity. There is only one way to do this – P applications must exceed P removal. It is not enough to merely meet the current yield targets of the crop.

And so we adopt a P building program…now what? How much P should be applied? How much annual P building is enough? When do we switch from “building” to “maintaining”? I believe it is impossible to guess at this or do it blindly. We have to have a target “ideal” for long term P supply and blind strategies are like shooting in the dark. We have to know where our soil is at and we have to know where we want to go.

The IPNI has a cool website which calculates nutrient removal for different crops. Bookmark that site. Very useful but still only a guide. Soil is much more complicated then a linear calculation of crop removal.  In order to keep moving toward, and ultimately achieve, our optimum soil P supply target we must have strategies based on “ground truth-ed” measurements.

Not every soil needs to have a P building strategy. Some soils are rich in crop available phosphorous. So rich that it can actually be drawn down or “mined” – in some cases for years – by not applying P and still be a P rich soil. Manured soils are the obvious case that comes to mind. We could actually have the same P supply target in these soils but our strategy is the opposite of P building. We allow for crop removal of P to draw soils down to our “target” P supply.

Below is a Western Ag CropCaster image of a field which we would allow P to be “mined”. There is no need to guess or try to calculate when we would switch from a “mining” strategy to a “maintenance” strategy. Annual sampling will show us when we approach our P supply target.

figure 1 cropcaster image

What should our “target” P supply be? The decision rests with each individual client, however I believe that it is pointless to use a maintenance strategy on the above soil. At the very least the target P supply should be allowed to fall to the point where the crop can respond to the applied P. If we set aggressive yield targets of 70 bu canola then current P supply of 117 lbs could draw down to 70 lbs before we would see even a hint of response to applied phos. I suggest that the P supply could be allowed to fall below the 70 lb level, to a range where P maintenance (balance between crop removal and applied) and P responsiveness are at least in the same ball park. Soils capable of at least 25 lbs P supply still have a strong tendency to high productivity and would match up pretty nicely with a maintenance strategy for those pushing aggressively on yield. Using the IPNI calculator the maintenance to cover 70 bu canola would be about 56 lbs. Once we have arrived at the target P supply “space” the P maintenance vs applied P fertility could be fine tuned and reconciled based on continued annual Western Ag sampling and optimized crop fertility planning.

 

 

 

 

 

Advertisements

Do Western Ag Optimized Crop Fertility Plans Hold Up in a Drought?

In my mind, one of the key “deliverables” of a crop fertility plan is that it should be able to stand up to a wide range of environmental conditions. After all there are no gaurantees that we will receive seven inches of rain (which is what I usually assume when generating PRS CropCaster model scenarios and crop fertility plans). The last many years our rainfall totals have been much higher but the seven inch assumption has still allowed me to generate crop fertility plans with high yield targets in mind and consider risks of lodging and other issues which might come from pushing fertility too hard in high precipitation years. This year for many areas the situation has reversed and drought conditions are prevalent (inevitable in Saskatchewan). So how does a crop fertility plan which optimizes for seven inches of rainfall during the growing season hold up if only two inches is received? This is exactly the case for a Saskatoon area client who I recently visited to do some mid season follow up. After an interesting tour of these fields yesterday the customer kindly consented to (anonymously) allowing me to use his CropCast scenarios and field photos for a blog post.

At this time of year in our service cycle we endeavor to do what is called a “mid cast” – that is a mid season field visit which considers our original plan with the circumstances of the growing season. Besides a mid season check on our recommendations it gives us an opportunity observe first hand if there are situations which might come into play with respect to limiting crop yields…weeds, disease, lodging, etc.

This is a new customer who decided to trial the service on five fields. Three of these fields turned out to generate crop fertility plans which were big departures from his original blanket fertility plan. For these fields the client tailored his fertility field by field according to the Western Ag recommendations but wisely left check areas which reverted to the original blanket fertility. The plan is to take these areas to yield and evaluate the alternative fertility strategies. Then Mother Nature pitches in by throwing a drought into mix! There has been about 2 inches of accumulated rainfall on these fields to date in the growing season (to go along with apporximately 4.3 inches of stored subsoil water) . In only a few short days if not already, further rainfall accumulation will be of no benefit. In discussions with the client he felt that the yield potential for these fields should fall into a range of 35 to 40 bushels per acre which I concurred with and later found the PRS model to be consistent with as well.

So for each of these three I’ll present the model scenarios in this article along with pictures which compare the Western Ag optimized fertility to the checks using the farmer’s original blanket plan. All three fields involve HRS wheat. The model allows us to “pencil in” additional assumed costs ballpark estimated to be $200 per acre in consideration of all other non-fertilizer unit costs (including fixed costs).

Case #1: Wheat on Pea Stubble:

Figure 1A: Model Scenario for Case #1 Wheat on Pea Stubble

Figure 1A: CropCast Model Optimization for Case #1 Wheat on Pea Stubble

Note that in this case following the WA optimized plan results in a modest profit margin of $26.73. While the blanket plan produces the same yield, the profit margin projects to a loss of  $34.04 due to applying nutrients at rates which are unresponsive in the drought conditions of this growing season. An interesting side note in this case is that according to the model this field should still be somewhat responsive to applied N even with the drought. Cutting N out of crop fertility completely would project a yield of 29 bushels (with the crop feeding off of the N provided by the pulse crop residue). Here is a picture of this field showing the original blanket fertility plan applied on the left and the WA optimized plan applied on the right:

Photo 1A: Original Blanket Fertility on Left. WA Optimized Fertility on Right

Figure 1B: Case #1 Wheat on Pea Stubble. Original Blanket Fertility on Left. WA Optimized Fertility on Right

Case #2: Wheat on Canola Stubble with High Residual N

Figure 2A: CropCast Model Optimization of Wheat on Canola Stubble Field with High Residual N.

Figure 2A: CropCast Model Optimization for Case #2 Wheat on Canola Stubble Field with High Residual N.

In the above case the sample field was found to have a high residual of N following the 2014 canola crop. So much so that if true the 2015 wheat crop would be virtually unresponsive to applied N even if the assumed seven inches of rain had materialized. As a result our optimized plan recommended zero N be applied (along with 34 lbs of Phos). The projected yield for the field with this plan according to the model is about 39 bu with 2 inches of rainfall. As with case #1, a modest profit is $34.29 per acre is projected. Again, as with the first case, the original blanket fertility plan would result in a loss – this time of $44.06 per acre due to cost of unresponsive higher rates of fertilizer. Below is the accompanying picutre of the field showing the original blanket fertility plan on the left and the WA (zero N) plan on the right.

Figure 2B: Blanket Fertility on Left. WA Optimized on Right.

Figure 2B: Case #2 Wheat on Canola Stubble with High Residual N. Original Blanket Fertility on Left. WA Optimized on Right. Flag in Distant Background Against Truck.

Case #3 Wheat on Pea Stubble with K Deficiency

Figure 3A: Case #3 Wheat on Pea Stubble. Original Blanket Fertility on Right. WA Optimized Fertility on Left.

Figure 3A: Case #3 Wheat on Pea Stubble. Original Blanket Fertility on Right. WA Optimized Fertility on Left.

In this case besides the typical residual N reading we see with pulse stubble fields, we also see a K deficiency feature in the analysis. The client uses 12 lbs of K in his blanket plan, however we found the field to be responsive enough that the model recommended significantly more – 45 lbs – at least with the original seven inch rain assumption. Even with the reality of the drought, the model projects a slight yield benefit of three bushels attributable to additional applied K. The field is of a light sandy loam texture and therefore according to the model the expected yield potential is lower at about 35 bu with the recommendations compared to about 40 bushels on the the heavier loam textured field cases. Unfortunately in this case the WA fertility recommendation costs significantly more and the projected yield is about five bushels less. Therefore a loss is projected for this field of $51.20 per acre. However the orginal blanket fertility strategy projects to fare much worse with a projected loss of $98.33

Figure 3B: Case #3 Wheat on Pea Stubble. On Left Planned Blanket Fertility. On Right WA Optimized.

Figure 3B: Case #3 Wheat on Pea Stubble. WA Optimized Fertility on Left. Planned Blanket Fertility on Right.

So how do the original Western Ag optimizations done assuming seven inches of growing season precipitation hold up under drought conditions? In our three cases we project margins for our optimizations of $26.73, $34.29 and ($51.20) for cases #1, #2 and #3 respectively with an average margin of $3.27 so a break even scenario. The original planned blanket strategy projects losses of ($34.04), ($44.06), and ($98.33) for cases #1, #2, and #3 respectively even though yields average less then a bushel better with the WA scenarios.

Discussion: Even in if drought conditions become the reality when we don’t plan for drought in our crop fertility strategies, through PRS analysis and CropCast modelling it is possible to devise plans which stand up to growing season risks very well. This is the benefit of well targeted, field by field crop fertility optimization through the Western Ag process. It is not that hard to make money when growing conditions are very good and moisture is neither limiting nor excessive. The real challenge will come in seasons (such as this year for many) where drought returns, and the the efficient “fine tuning” of the Western Ag crop fertility plans might make the difference between breaking even and losing money. One should also consider that with farmers pushing harder on crop fertility then ever before, that highly variable residual fertility will be a reality in the drought stricken areas and carry into the 2016 season. The exercise here shows field by field sampling by Western Ag will provide an opportunity for farmers to profit by efficiently recovering this carryover. That opportunity will be lost for the most part with blanket fertility strategies.

Guest Post: Cereal Crop Staging

I am pleased to put up my second invited guest post on this blog. The article discusses identification of crop staging of cereals. It is a timely article as we are moving rapidly into fungicide season. Cereal crop staging can be a little ambiguous and tricky when trying to project and plan the timing of fungicide operations. We consulted with Cory Jacob a week or two ago because of the atypical (at least for the last 7 or 8 years) and variable pace of crop development we were seeing in the 2015 cereal crop – we wanted to be certain we were interpreting our observations properly. I thought it would be a great topic for a blog article….so here we are.

Cory works as a Regional Crops Specialist with the Ministry of Agriculture out of Watrous. He carries in his back pocket both agronomy based Bachelor’s and Master’s degrees from the University of Saskatchewan. He has held various summer agronomy themed jobs in private industry and also has experience as a graduate teaching assistant at the University of Saskatchewan. Cory works closely with producers and industry to help alleviate current and future issues in crop production.


Cereal crop staging – Cory Jacob, Saskatchewan Ministry of Agriculture, Watrous, SK

Leaves and tillers

Cereal crops are easily the most difficult to stage. When staging a cereal crop, it is good to know that the leaves develop on alternate sides of the stem. What I mean, is that the first leaf will be on the left side of the plant and the second leaf on the right side and so on.
The best way to stage a cereal crop is to first, take all of the leaves or stems in your hand and see which is the tallest, the tallest stem is the main stem as it is the furthest along in growth and development. Next is to identify the leaves, the first leaf will appear on the left side of the plant and will have a blunt or rounded tip and will be the lowest leaf on the left side of the plant.
Tillers can be considered as side shoots off of the main stem leaves and have their own sheath called a prophyll. Typically, the coleoptilar tiller, which is formed from the coleoptile node, on the seed, this tiller develops at any time regardless of the plant development. The tillers that form from the leaf axil (where the main stem and leaf blade meet) emerge after the plants has 3 leaves and will develop in order of the true leaves, so tiller one will emerge from the axil of leaf one and so on. Typically, 5 tillers is the maximum observed on a plant.

stage cereal plant

Figure 1: Cereal Plant Leaf and Tiller Staging

In general, every 3-4 days a new leaf will emerge on a cereal crop plant, but this is a factor of many things including growing degree days, environment, genetics, fertility, crop stress, etc.
Head initiation takes place during the 4 leaf stage and before stem elongation begins. If you were to cut the stem open, you will find the head developing within the stem. Once the formation of head is complete, stem elongation (jointing) begins and this pushes the wheat head up in the plant. Stem elongation beings around the 5 or 6 leaf stage. There are 7 nodes with in a cereal plants, 4 remain below ground in the crown area, the 5th one remains around the soil surface and elongates only slightly, which the 6th and 7th nodes elongate well above the soil surface, which pushes up the head. The peduncle (stalk leading to the head) is the longest internode.
Flag leaf
The flag leaf is the last leaf to emerge before the head. Typically, the 6th leaf is the penultimate leaf (leaf right below the flag leaf) and the 7th leaf is the flag leaf. This can greatly differ, but can be a general guideline. The flag leaf will begin to emerge just after the 3rd (7th) above-ground node is observed. The flag leaf accounts for about 75 percent (generally) of yield, so it is best to protect the flag leaf with a fungicide application.
The boot will swell after flag leaf development and the peduncle will elongate. The flag leaf sheath will swell to form the boot and the flag leaf collar and sheath will be forced open by the developing head.
Flowering
Heading occurs as the peduncle continues to elongate and push the head out of the fag leaf collar. In barley, the crop flowers just before or during head emergence, other cereal crops will flower after head emergence. Typically, wheat will flower 3-10 days after head emergence. The head of the cereal crop develops from the middle out and the color of the anthers is very important for flowering. The anthers is what you will see hanging off of the wheat head. Green anthers mean that flowering has not occurred yet and yellow or gray anthers mean that flowering has occurred. During flowering (anthesis) is the ideal time to spray for Fusarium Head Blight, as it is a tight window to hit all of the acres at the ideal stage, it is recommended to begin spraying when you see 75% if the heads on the main stem fully emerged. Perfect timing will be when just a few yellow flowers can be observed in the middle of the wheat head. A producer should stop spraying when they notice that 50% of the heads on the main stems are in flower. It is too late to spray once you see the anthers turn white and dry up, this means flowering is complete and it is too late to spray, or rather spraying will provide little benefit. (FHB infographic place here)

Infographic FHB Timing

Figure 2: FHB Fungicide Timing

Grain development
For grain development, the watery ripe stage occurs when a clear fluid can be squeezed from a developing kernel. The plant will be green and the lower leaves will begin to die off. Soft dough stage is when the material pressed out of the kernel is no longer a liquid and is a meal or dough consistency. Hard dough stage is when the kernel reach physiological maturity and little green color remain in the plant. Kernel hard stage occurs when the plant has become completely yellow and the kernel has become firm. The surface of the kernel can be dented with the edge of a thumbnail. Harvest can occur on the kernel is hard and the plant has become dry and brittle.

Special Guest Post by Katelyn Duncan: Sprayer Tank Cleanout

We have been fortunate to have Katelyn Duncan as a part of our agronomy group now for a little over a year. Being an agronomist and also actively involved in their family farm operations outside of Regina, she is familiar with both the science and the hands on operations of farming. Earlier in the spring she posted up a tweet about sprayer cleanout with a view of preventing potentially crop damaging chemical residue contamination of their sprayer. She hit on an issue which has caused large losses for farmers over the last few years, and I asked her if she would be interested writing an article about the subject for this blog. She has written an excellent article and at this time of year it is a timely post. Click on the link below to view the article. Thanks for this contribution Katey!

Sprayer cleanout article

Single Prescription Optimized Crop Fertility Considering Variability Within the Field

Variability within a specific field can be a challenge when it comes to devising a single prescription, non-variable, crop fertility plan. Client discussions often arise about how such variability should play into the fertilizer plan for a given field. A common concern in these discussions is that since fields contain areas such as salinity, or sand ridges, etc, that the “optimized” fertility plan does not consider these poor yielding areas of a field (which are intentionally avoided when sampling). Often the suggestion is that planning for 55 or 60 bushel canola yields should be scaled back accordingly in consideration of sub-optimal areas which dilute the “true” yield expectations down to 40 or 45 bushels. It is a valid concern and worthy of consideration in determining the ultimate fertility plan for a field.

How should one deal with such a challenge? Fortunately with Western Ag, we possess a tool that we can use to help us create simulations of this type of variability. Then we can compare the bottom lines generated under different crop fertility management ‘philosophies’ to see what type of strategy is most favorable.

Often the first instinct of a farmer client is to think in terms of managing fertility based on average productivity and yield expectations. In other words, the view is that, say, 60 bushel canola yields are unrealistic for certain fields and therefore fertilizer plans should be scaled back to reflect a more ‘realistic’ yield expectation of 45 bushels (or whatever). Is this the correct philosophy to determine the most profitable or lowest risk fertilizer plan for such a field?

When we sample a field, we intentionally avoid any saline areas which tend to get seeded. And low productivity areas like sand ridges would also be avoided unless such areas were typical of the field. So when we run the CropCast model to devise an optimized fertility plan the yields generated by the model do not represent an average across all areas of the field. We are estimating a yield which excludes the poor productivity areas. If we go with such a plan then the philosophy would be to ignore the yield diluting effects of low productivity areas such as saline areas and sand ridges and plan for 60 bushels.

So we have now two competing philosophies in setting the crop fertility plan for a field which we can use to run simulations and hopefully clear up which strategy is likely to be most profitable and/or lowest risk. The alternative management philosophies are:
1. Set a plan based on yield which excludes low productivity areas like salinity and sand ridges – ie: 60 bushels.
2. Set a plan based on the overall average yield for a field – ie: 45 bushels.

Once the lab analysis comes back and the CropCast model is set up, we are ready to run the simulations of the competing philosophies and select the one which is best for our field. Using philosophy #1 the model does not consider low productivity areas and an optimized plan is generated with an expectation of 60 bushel yield (Figure 1 below). However we know that the field consists of salinity and sand ridges, which means that the true yield expectation of the field with this type of fertility is 45 bushels not 60 bushels. In this case, from discussions with the client we understand that about 60% of the field could be expected to yield 60 bushels per acre (in line with the CropCast model) while the other 40% would have an expected yield of only 22 bushels per acre with the lower yields attributable to the marginal saline and sand ridge areas. The overall average yield for the field is then expected to be 45 bushels. From the model run, the applied fertility for the field is 99-33-0-24 at a cost of $79.32/acre. If the price of canola is $9.50 per bushel and all other non-fertilizer costs are $250 per acre then the profit margin for the field calculates as follows:
• 45 bushels x $9.50 per bushel = gross of $427.50 per acre
• $427.50 – $79.32 (fertilizer costs) – $250 (all other costs) = $98.18

Figure 1: CropCast simulation excluding low productivity areas of field

Figure 1: CropCast simulation which excludes low productivity areas of field.

Now for the alternate plan (philosophy #2) where fertility is set according to average yield expectation of 45 bushels (Figure 2 below). Here we see that the CropCast model has computed a fertility plan of 61-21-0-16 to generate this yield (note that this field has some N carryover supply of about 30 lbs already in the soil). Before we consider the yield diluting effects of salinity and sand, the CropCast summary shows the following:
• 45 bushels x $9.50 per bushel = gross of $427.50 per acre
• $427.50 – $50.01 (fertilizer costs) – $250 (all other costs) = $127.49
So at first glance the strategy of fertilizing to a set ‘realistic’ yield target of 45 bushels averaging across good and poor productivity areas would appear to be the more profitable and lower cost strategy. However this analysis has not yet accounted for the low yielding saline and sand ridge areas of the field. Even if we make the (generous) assumption that the yield in these low productivity area is 22 bushels per acre – same yield as with the higher fertility scenario – the overall average yield would be 35 bushels and not 45. The profit margin would then calculate out as follows:
• 35 bushels x $9.50 per bushel = gross of $332.50 per acre
• 332.50 – $50.01 (fertilizer cost) – $250 (all other costs) = $32.49

Figure 2:

Figure 2: CropCast simulation that sets yield target by averaging across low productivity areas of field.

We see from this exercise that it is a mistake to devise a fertility plan for this field that averages across the poor yielding saline and sandy areas of the field. We wind up shooting ourselves in the foot and missing out on $98.18 – $32.49 = $65.69 profit per acre. While it might seem counter intuitive, the best fertility plan for this field is to stick with the model optimization which excludes such areas. Real life yield expectations can still be set straight after running the model by accounting for low productivity areas and adjusting true yield expectations accordingly.

Sea Ice Extent – Day 10 – 10th Daily Record

There is an amazing phenomenon happening right now that many are unaware of – growth of Antarctic sea ice (relative to long term averages). As the annual Antarctic sea ice minimum approaches, the current anomaly is about a 3 sigma departure from the long term average. The data seems to show that this occurrence is not just a blip, but seems to be part of a tendency over the last decade or more. In fact the trend is currently overwhelming the decline in arctic sea ice (which seems to have stabalized over the last 7 or 8 years). In fact global sea ice extent (arctic and antarctic combined) looks to be around 2 sigma departure above normal for this date! This has important implications for global climate because above normal sea ice reflects sunlight heat energy (like a mirror) that would otherwise be absorbed by ocean waters.

sunshine hours

10 daily records in a row in 2015.

Antarctic Sea Ice Extent Breaks Daily Record By 700,000 sq km.

That is 3 standard deviations above normal. In fact every day in 2015 has been above 3 STD.

DataSouth / North

Antarctic Sea Ice Extent for Day 10 From 1978 (infilled)Global_Sea_Ice_Extent_Zoomed_2015_Day_10_1981-2010Antarctic_Sea_Ice_Extent_Zoomed_2015_Day_10_1981-2010Arctic_Sea_Ice_Extent_Zoomed_2015_Day_10_1981-2010

View original post

Seed Drill Row Spacing – Part Two (Sort of)

In my previous post on cereal row spacing I discussed the many conflicting functions of modern seeding equipment. By conflicting I am suggesting that particular functions performed by a seed drill actually work against each other. For example, optimizing the function of seed bed utilization (row spacing) conflicts with the function of minimizing seed bed disturbance. Both functions are important but designs to optimize for one function would tend to work antagonistically on the other.

These types of conflicts put rigid limitations and constraints on machine design. It narrows the range of conceptual design options available to perform the many needed functions of seeding equipment. One way to illustrate the way in which this type of conflict plays out with seeding equipment design is through the use of a Venn diagram. With a Venn diagram, we let a circle define the “space” of design options to impart a specified function in a seed drill. Each function which the drill needs to perform as a condition of commercial acceptability is then represented by a separate circle.

The figure below shows a Venn diagram for seven distinct functions which I believe a modern seed drill needs to carry out in order to succeed in the marketplace. While there are no doubt many more functions not considered here it is sufficient to demonstrate the challenge and complexity involved in equipment design.

Image

The figure shows how these functional conflicts work against each other and severely limits the alternatives for engineers and equipment designers. The small shape which I have outlined in black shows the small overlapping area of “solution space” which can reconcile all of the mostly conflicting and non-overlapping space of design alternatives. Note that the optimal design solution for each individual function does not necessarily lie within the small overlapping “solution space”. However to obtain greatest commercial value – which is in theory the maximized sum of values of the seven functions – the ultimate design must lie within the small space.