100-ppm of anything in irrigation water amounts to 270 lbs. per acre-foot of water. Example: A bicarbonate level of 250-ppm (very common in California and other parts of the world) delivers 675 lbs. of bicarbonate per acre foot of water. Many crops may need 2.5 acre-feet of water, so a grower could deliver a surprising 1,688 lbs. of bicarbonate per acre into the soil each year. Each pound of bicarbonate ties up one pound of soluble calcium.