An agricultural micro-fertigation water includes a phosphate fertilizer, a water-soluble organic acid and a water-soluble organophosphonate, and is prepared by a method wherein the phosphate fertilizer is added to the irrigation water as a chaser to (addition with or after components of) the combination of a water-soluble organic acid and water-soluble organophosphonate to fully prevent precipitation and thus prevent plugging of a micro-irrigation system despite the addition of phosphate fertilizer in water having a precipitation factor of from 125 to 1,000 ppm, wherein said precipitation factor is a combined level of total alkalinity (as CaCO3) in ppm and total hardness (as CaCO3) in ppm.
