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.

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