index.
Depending on how much detail we decide to include about this earlier (see comment in section 3.1.1.3), could add sentence here:
"As in section 3.1.1.3, there are some examples of the P index increasing with the October drill treatment. This can be attributed to the increased fraction of P remaining on the surface from fall surface applications when the cover crop no-till drilled compared to fall incorporated applications when no cover crop was present."
-0.4,
Strike
October drill,
Strike
All
Replace "All" with "Most" since we do see a few cases where the Oct CC actually increases P Index
However, even though P application as manure decreased total P losses, it slightly increased losses of soluble P (Table 3.1).
This is no longer true for the St. Charles soil (or for this ASD), but it is still true for some soils/regions.If we want to keep things simple, could strike this sentence and the following one.
I looked around to see if the sentence citing Bundy could fit elsewhere but didn't find any obvious place since the effect of nutrient source was consistently so small relative to other things.
Nonetheless, especially in cropping systems with low P losses, a reduction of 0 lb ac-1 y-1 would be non-trivial and additional benefits would accrue over time as soil test P decreased.
Recommend striking this sentence now that the difference rounds to zero. If we wanted to provide a specific example that supports the previous sentence about legacy P, could include some info about the relative contributions of "soil" vs. "applied P" to the surface soil total P we calculate in the P Index, which is an important part of the particulate P calculations.
Picked one "baseline" example. This is where we fall apply fertilizer at a rate equal to crop removal on St. Charles SiL with 50ppm STP:
Surface soil **total ** P concentration is 420 mg/kg, which breaks down to ...
This particular example is on the low end of what we would see for the contribution from applied nutrients because our baseline "fall chisel disk" tillage system has incorporation passes in the fall and spring that leave very little amendment P on the surface.
fertilizer
replace "fertilizer" with "nutrient" (covers both fertilizer and manure)
t 0 lb ac-1 y-1, o
With the bug fixes, this difference is now small enough that it rounds to zero.
crop removal = 3.72<br /> 20% reduction = 3.68
reduction
With the updated results, now have a small average increase with the October CC. This can be attributed to fall surface (unincorporated) fertilizer applications
In Fig 3.4, all four of the points with >5 PI shown for CC Oct Drill have STP = 100 and P applied = crop removal and fall surface fertilizer application
In this specific case, the values of these four points did not increase with the bug fixes, but a different correction I made to a subset of October CC and September CC fields related to incorporation method brought many of the other values down (so now these stick out)
Table 3.1:
Pick up here
three-pass chisel plow and disk tillage system (hereafter, “chisel disk”)
Ag Water Quality discussion: clarify what each pass in the three pass sytem
Summary
Ag Water Quality Meeting: use "estimated P loss" instead of "P Index" for clarity
2026
Link to relevant existing resource explaining P fractions etc. https://ipcm.wisc.edu/wp-content/uploads/sites/54/2022/11/UnderstandingSoilP04.pdf
For clarity, we emphasize that all Tables in this document report P reduction from a practice as a positive number (larger is better); this decision was made to provide consistency with similar reports prepared by neighboring sta
I think I might have originally proposed that we plot the reductions as negative numbers, but now that I'm seeing the plot right next to the table (which reports reductions as positive numbers) I'm wondering if we should make them match
it slightly increased losses of soluble P
Yes - and what's going on behind the scenes here is that we assume that fertilizer contributes to the DP fraction only in the season of application, but with manure we account for DP contributions in the first season of application AND the second and third seasons after application (this is all based on work that Peter Vadas did). In the second season following application, 20% of the manure total P remaining on the soil surface is expected to become 9 water soluble. In the third season following application, 5% of the total P remaining on the soil surface is expected to become water soluble.
Vadas, P.A., L.B. Owens, and A.N. Sharpley. 2008. An empirical model for dissolved phosphorus in runoff from surface-applied fertilizers. Agric. Ecosys. Environ. 127-59-65. Vadas, P.A., L.W. Good, P. A. Moore Jr., and N. Widman. 2009. Estimating phosphorus loss in runoff from manure and fertilizer for a phosphorus loss quantification tool. J. Environ. Qual. 38:1645-1653. Vadas, P. A. and P. J. A. Kleinman. 2006. Effect of methodology in estimating and interpreting water-extractable phosphorus in animal manures. J. Environ. Qual. 35: 1151-1159. Vadas, P.A., W.J. Gburek, A.N. Sharpley, P. J. Kleinamn, P. A. Morre, Jr., M. L. Cabrera, and R. D. Harmel. 2007. A model for phosphorus transformations and runoff loss for surface-applied manures. J. Environ. Qual. 36:324-332
Vadas, P.A., Gburek, W.J., Sharpley, A.N., Kleinman, P.J.A., Moore, P.A., and Cabrera, M.L. et al. 2007a. A model for phosphorus transformation and runoff loss for surface-applied manures. J. Environ. Qual. 36: 324–332. doi: https://doi.org/10.2134/jeq2006.0213
This difference can be attributed to the effects of manure solids on soil physical properties–i.e., a “mulching effect” (Grande et al., 2005).
Yes - and for context (not sure it's worth including), we calculate the amount of residue added to the soil surface as a result of the manure applications and use this as an input to RUSLE2 when we run soil loss. For the range of manure application rates in the Cg-Sg rotation, that amounts to 834 - 1390 lb/acre dry matter residue being added to the soil surface
Figure 3.9
update plot title to remove "and tillage" (conveniently this will also help the end of the title from being cut off!)
/tillage
delete
/tillage
delete
and tillage
delete
and tillage
This comparison isolates only the timing shift from fall to spring. Suggest updating this header to "Shifting the timing of P application from fall to spring"
More info: The 24 baseline scenarios shown below in Fig 3.9 all have the "Fall Chisel Disk" tillage system (1 chisel pass in fall, 1 disk and 1 cultivation pass in spring). Since we have tillage passes in both fall and spring, this allows us to isolate the effect of timing (fall incorporated vs. spring incorporated) for the baseline scenario
I believe we decided to do it this way because it allows us to isolate the effect of timing across all 4 of our tillage systems, even the ones like strip till and no-till that don't have "spring" and "fall" variations like we do for chisel disk and vertical till systems (spreadsheet attachment to illustrate example with Rock County soil)
grass
"perennial cool season grass"
could help mitigate these risks.
Note to self: see if I can also find a guidance document or other ref about how if filter strips are not designed to the proper width / specs sediment can build up and the strips can actually be a SOURCE of additional soil loss
at the edge
"at the downslope edge" - suggesting this wording because I have been surprised at the number of Snap users (and agency personnel!) who forget this point
Sep
missing the "CC" in front of Sep here to match graph label
high soil test P
Note to self, make sure that somewhere we specify that this is Bray1 soil test p
show
typo: shows
Good et al. (2025)
citation format: change to parenthetical