Fertilizer Id in management practices

[Palki Arora]

Hi everyone

I was trying to do the management practices on cropland sub watersheds for upland cotton crop. What is the meaning of fertilizer id in that(while doing fertilizer operation)? I doubt it is NPK ratio but how to convert the given fertilizer in that particular ratio? If its given that we have to apply 50kg/ha of N and 45kg/ha of P on April 15, then what fertilizer id should be used and why?

Looking forward for your help guys.

Thanks

Palki

[charlesi @iastate.edu]

You could get to those N and P application rates by using one fertilizer or a combination of fertilizer types.  The xx-xx-xx is in fact the N-P2O5-K2O ratio of the fertilizer.  The fertilizers and their nutrient contents are described in Appendix A.4 of the SWAT2012 I/O Manual.  You can also add a new fertilizer type that would give you the N and P contents you need to get to your desired application rate.  But from the numbers you offer, it appears as though either 05-10-15, 05-10-10, or 05-10-05 would be close enough to your desired ratio, with all 3 types having 0.050 for Min-N and 0.044 of Min-P (per page 609 of manual).  Just add the amount of fertilizer (kg/ha) you need to get to your total application rate for N and P.  Note that Min-P = P2O5 times 0.44 (you are probably interested in Min-P, not P2O5).

--Charles

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