An average loam soil will have 4000 pounds of nitrogen, 4000 pounds of phosphorous, and 20,000 pounds of potassium per acre in the top eight inches most of it in forms that are unavailable to plants. Many minerals present in the soil are most available to plants if the soil pH is neutral to very slightly acid. Soil in my region is neutral. We do not run fertilizer through the irrigation system. If your irrigation water is alkaline, you will have to adjust it to increase soil fertility. Your county ag agent is your best source for information. We use organic mulches and green manure crops for soil fertility. We do use bone meal at planting time on our large dahlia crop. But, hey, I think we need to use alfalfa like LizaLily because we want 100 blooms per day on our Chilsean's Pride dahlia. In correcting deficiencies of minor elements, it is important to realize that the difference between a therapeutic dose and a toxic dose is pretty small for some of the nutrients. Essentially, what we use here in the Great Lakes Region is probably going to have no bearing on what someone uses in your area. Talk to growers in your area and your ag agent. We have received valuable information from both.