P. Allen Hammer

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 ...

Comparison of hydroponic solutions for poinsettia nutritional studies 1

Abstract Poinsettia cultivars Supjibi and Freedom were grown in eight hydroponic solutions to develop a baseline solution for further nutritional studies. Four solutions contained nitrogen (N) from Ca(NO3)2‐4H2O and KNO3 (denoted as ‐NH4) and four contained Ca(NO3)2‐4H2O, KNO3, nitric acid, and NH4NO3 as the N sources (denoted as +NH4). The four ‐NH4 and +NH4 solutions were further divided by an IX or 2X rate of micronutrients [boron (B), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), and zinc (Zn)] (denoted as IX or 2X). A factorial of these four solutions at 2 concentrations (100 mg L1 of N and potassium (K) and 15 mg L1 phosphorus (P), or 300 mg L1 of N and K and 46 mg L‐1 P) was studied. Greater leaf and stem dry weight for both ‘Supjibi’ and ‘Freedom’ was observed in plants grown with the +NH4 solutions, with a larger increase occurring with’ Supjibi’. Leaf NH4‐N content for both cultivars was higher for both the 100 and 300 mg L‐1 N and K fertilization rates when NH4‐N was included. The le...

Industry root media analysis results: Useful in determining greenhouse nutrition problems and educational opportunities

Abstract Two years of floriculture greenhouse industry root media analysis results from the Purdue University Greenhouse Media Testing Laboratory were studied for nutritional trends. Root media analysis results were statistically analyzed over 72 categories by crop, time, and firm. Sixty‐five percent of samples were submitted in the spring and fall, during the period of highest production of greenhouse crops. The largest number of samples were from: roses (21.5%), poinsettias (14.5%), and geraniums (8%). Of the samples received, 87% came from 32 firms. The mean pH level for all samples was 6.32, which is above the acceptable range for most crops of 5.8 to 6.0 for soilless root media. In addition, 63% of all samples were also above the acceptable pH range. There were also a large percentage of samples that contained excessive levels of magnesium (Mg) [39.4%], potassium (K) [27.4%], and phosphorus (P) [27.4%]. Our analysis suggests the need for growers to purchase pH and soluble salt meters to regularly mon...