I plant sunflowers with grains and vegetables and the effect is minimal in my opinion. Probably just due to the nitrogen and nutrient hogging, and some shade production. I wouldn't hesitate to plant pretty much anything with sunflowers or after them, or to use sunflower stalks as mulch with other plants, but maybe other people have had crop failures they would like to share.
I didn't know about this for years and have always had sunflowers in my gardens. After some experiments and observation I do take the allelopathy seriously. I still grow sunflowers though! We talk about sunflower allelopathy in this thread and also this one
I would encourage you to grow the sunflowers and observe the underplantings. I have had good luck with pole beans growing up sunflowers and with chard growing next to them. I wonder how clovers would do under there?
And another report claimed that soil bacteria and fungi can reduce oxidative stress from drought and excess salinity (although, as far as I know, this is in plants and not germinating seeds specifically) :
"Co-inoculation of lettuce ( Lactuca sativa L.) with PGPR Pseudomonas mendocina and arbuscular mycorrhizal fungi ( Glomus intraradices or G. mosseae ) augmented an antioxidant catalase under severe drought conditions, suggesting that they can be used in inoculants to alleviate the oxidative damage elicited by drought."
"The rapid degradation of juglone and other suspected allelochemicals by soil bacteria make it unlikely that these compounds are important mediators of plant-plant interactions under natural conditions. " http://www.ncbi.nlm.nih.gov/pubmed/24276429
We planted a dozen Siberian Mammoth sunflowers last year around a 144-square-foot perimeter to encourage goldfinches. The sunflowers killed very hardy perennials and self-seeding annuals, such as French sorrel, Arctic kiwi, Russian sage, lilies, iris, redbud, Hardy Chicago fig, kinnickinnick, and calendula. We can't grow any legume species in our yard, and I'm wondering if the sunflowers would cause that side-effect. I realize legumes are very sensitive to air and water pollution, and we have acid rain, due to a nearby steel smelter. Might be a combo of the allelopathy + pollution.
I'm not dead! I feel happy! I'd like to go for a walk! I'll even read a tiny ad: