Douglas A. Bailey

A novel approach to calculate acid additions for alkalinity control in greenhouse irrigation water

Abstract Excessive alkalinity in greenhouse irrigation water can increase substrate solution pH, resulting in reduced micronutrient availability for plants. A spreadsheet was designed to offer a quick and practical method for calculating: 1) amount of nitric, phosphoric, and sulfuric acid required to achieve an endpoint alkalinity or pH in irrigation water; 2) the amount of nutrients added by the acid addition; and 3) acid costs. It calculates both pH and alkalinity after acidification, regardless of endpoint selected. The spreadsheet accounts for the pH dependent reaction which determines the relative percentage of each of the carbonate species ‐carbonates (CO3 2‐), bicarbonates (HCO3 ‐), and carbonic acid (H2CO3) ‐ present in the solution. In addition, the acidification calculations account for the starting pH of the solution, the alkalinity found in the initial solution, and the dissociation characteristics of the acid selected to neutralize the alkalinity. The spreadsheet was validated with six water ...