Jared Barnes

Modeling impact of nitrogen carrier and concentration on root substrate pH

ABSTRACT We conducted an experiment to quantify the effects on substrate pH from nitrogen (N) carrier and concentration. We used four concentrations of N (3.5–14 mM) and five fractions of ammonium (NH4+) (0–80% NH4+ of total N) that are found in commercially available fertilizers. Fertilizers were applied to fallow 14-cm-diameter pots (1.29 L) filled with a 3 peat:1 perlite (v/v) substrate amended with non-residual powdered calcium carbonate to raise the substrate pH to approximately 6.0. Harvests occurred at 20 and 42 days. Significant effects in the model included main effects of N carrier and N concentration, their squared terms, an interaction effect, and a time × N carrier. The fraction of NH4+ accounted for 45.0% of variation in substrate pH, and N concentration accounted for 1.5% of the total R2 of 76.7%. Substrate acidification was likely due to the physiological fertilizer effect and nitrification.

Nutrient disorders of Dianthus ‘Bouquet Purple’

ABSTRACT ‘Bouquet Purple’ pinks (Dianthus sp.) were grown in silica-sand culture to induce and photograph symptoms of nutritional disorders. Plants received a complete modified Hoaglands all-nitrate (NO3) solution. Nutrient-deficient treatments were induced with a complete nutrient formula minus one of the nutrients, and a boron (B)-toxicity treatment was induced by increasing B 10-fold in the complete nutrient formula. Plants were monitored daily to document sequential series of symptoms as they developed. Typical symptomology of nutrient disorders and corresponding tissue concentrations were determined. All treatments exhibited deficiency symptomology. Disorders for nitrogen (N), iron (Fe), calcium (Ca), and sulfur (S) were the first to manifest in pinks. Unique symptomology was observed for plants grown under potassium- (K), B-, copper- (Cu), and molybdenum- (Mo) deficient conditions, which supported the need for a species-specific approach when characterizing nutrient disorders of floriculture crops.