Garden with Insight v1.0 Help: Soil patch end year functions: change pH for effect of fertilizations during year

The addition of nitrogen fertilizers lowers soil pH if those fertilizers contain a significant portion of ammonium ions (as in urea, ammonium nitrate, anhydrous ammonia). All auto fertilization in the simulation adds directly to the nitrate pool (and not to the ammonium pool), but the assumption here is that there is some ammonium ion included in the fertilizers added. Nitrification of the ammonium ions to nitrate, which is assumed, creates hydrogen ions which reduce the soil pH. (Remember that the EPIC model is used to simulate conventional (not organic) farming and that you don't need to use these types of acidifying fertilizers in your garden. Options for the automatic application of less acidifying fertilizers would make the simulation more flexible.)

Nitrogen fixation by legumes is also added in here to the total acidifying nitrogen, because some of the nitrogen produced by N fixation is in the form of ammonium ions in the soil, which are nitrified in the same way as fertilizer ammonium.

Lowering of soil pH by ammonium is calculated by a linear function based on the amount of fertilizer added and N fixed, the bulk density of the soil, and the cation exchange capacity of the soil.

calculation of auto fertilization, nitrogen fixation
EPIC Auto Operations
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