Ever so simple improvement over the standard preset for farmland
Old: Only get to pick circular irrigation, yes (or no if you want) which in taging translates to irrigation=pivot
The world is though bigger than farming methods e.g. observed flying over Libya and South Africa so looked in TagInfo what are most common forms and explaining it as a much wider concept of
"Specifies the type of irrigation on farmland or whether a waterway carries water to be used for agriculture
so this got roled out as a customization
Yes, ploughing furrows in the land and then funneling water into them is an irrigation method too used, a lot more than just the 74 entries in the OSM data base, maybe just because no one is interested or because the list of methods is not offered in that standard preset. Ditch and Canal will surely tickle a few fancies.
Edit: some grammar