Coverage · Source

Iowa State University Extension — PM 1688: A General Guide for Crop Nutrient and Limestone Recommendations in Iowa

v1.3 (2026-08-23) · ISU PM 1688, revised February 2023, printed p.2-11, Table 1-16 (https://isuaamncus122stg.blob.core.windows.net/shop/PM1688PDF.pdf).

Fixed category table Computes rates in-app Lime / pH
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Crops covered

AlfalfaBluegrassBromegrassCloverCornCorn silageFescueGrass hayOatsOrchardgrassPerennial ryegrassReed canarygrassSorghumSorghum silageSoybeansSunflowerSwitchgrassWheat

Nutrient source for

IA

Lime / pH source for

IA

Frequently asked

What method does Iowa State University Extension — PM 1688: A General Guide for Crop Nutrient and Limestone Recommendations in Iowa use?

Fixed category table. Zone Forge computes this source's supported nutrient rates in-app and cites the published method. Its published lime method is computed in-app too.

Is this free to use?

Yes — Zone Forge's calculators are free and need no signup. This page shows the states and crops Iowa State University Extension — PM 1688: A General Guide for Crop Nutrient and Limestone Recommendations in Iowa covers so you can verify the source behind your recommendation.

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