Hello:

Thank you for your contact. According to information researched by our Extension Master Gardeners:

Citric acid will likely not provide the desired acidying result. Reasons - expensive, short chain acid that will rapidly breakdown (and thus not stick around long enough to be helpful). Citric acid is used in greenhouses to acidify irrigation water, but it's still not usually the acid of choice because of cost, it's a weak acid and will need lots more applied than others. It also offers no nutritive value to the plants, while the others do. We've attached some references that should be helpful on this. But it is unlikely to be a useful method for reducing soil pH.

 http://www.clemson.edu/extension/hgic/plants/other/soils/hgic1650.html

https://www.ces.ncsu.edu/depts/hort/floriculture/plugs/alkalinity.pdf

https://ag.umass.edu/fact-sheets/adjusting-alkalinity-with-acids