The stuff I can get seems to be polyphosphate http://www.yara.co.uk/fertilizer/products/liquid_product_range/liquid_npk_range/index.aspx would this be ok for going in the seed furrow with barley and oats? The idea would be to run the a pipe down the back of the seed tube. Alternatively I could dribble it above the seed after the soil is closed on it, so probably it would be above the seed by an inch or so. BUT would it just sit there and not be in the right place for the roots to pick it up?  However the coulters have a rear press wheel so it would then pick up, mmmmmm!