Comparative Evaluation of Nitrogen Release Patterns from Controlled-release Fertilizers by Nitrogen Leaching Analysis

• Published in: HortScience Vol. 32; no. 4; pp. 669 - 673
• Main Author: Cabrera, Raul I
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Alexandria, VA American Society for Horticultural Science 01-07-1997
• Subjects: Agronomy. Soil science and plant productions; Applied sciences; Biological and medical sciences; Chemical industry and chemicals; Exact sciences and technology; Fertilisers; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Industrial chemicals; Nitrogen fertilization; Nitrogen, phosphorus, potassium fertilizations; Soil-plant relationships. Soil fertility. Fertilization. Amendments; Soilless cultures. Co2 fertilization; Soilless cultures. Protected cultivation; Process dynamics; Nitrogen fertilization; Ammonium; Incorporation; Horticulture; Temperature effect; Inorganic fertilizer; Nitrates; Solutes; Property formulation relationship; Time curve; Lixiviation; Nitrogen fertilizer; Greenhouse study; Release; Fertilizer coating; Controlled release form; Loss; Nursery (plant); Container growing; Polymer; Topdressing; Slow releasing fertilizer; Application method; Leachate
• ISSN: 0018-5345; 2327-9834
• DOI: 10.21273/HORTSCI.32.4.669

Seven nursery grade (8-9 month duration), polymer-coated, controlled-release fertilizers (CRF) were topdressed or incorporated into a 2 peat: 1 vermiculite: 1 sand (by volume) medium to yield the same amount of N per container. The pots (0.5 L) were uniformly irrigated with DI water every week to produce a target leaching fraction of 25%. Leachate N contents (ammonium plus nitrate), employed as indicators of N release, allowed for comparison of CRF performance as a function of temperature changes over a season. Two distinct N leaching (i.e., release) patterns were observed over the 180-day experimental period. The fertilizers Osmocote 18-6-12FS (Fast Start: OSM-FS), Prokote Plus 20-3-10 (PROK), Osmocote 24-4-8HN (High N: OSM-HN) and Polyon 25-4-12 (POLY) exhibited a N leaching pattern that closely followed changes in average daily ambient temperatures (T avg ) over the season. This relationship was curvilinear, with N leaching rates per pot (NLR) being highly responsive to T avg changes between 20 and 25 °C. Temperatures above 25 °C produced an average maximum NLR of 1.27 mg·d -1 for these fertilizers. OSM-FS, PROK, and OSM-HN had the highest cumulative N losses over the experimental period. In contrast, the CRF group formed by Nutricote 18-6-8 (270: NUTR), Woodace 20-4-12 (WDC), and Osmocote 18-6-12 (OSM) showed a more stable N leaching pattern over a wider range of temperatures, with rates about 30% to 40% lower than those in the temperature-responsive CRF, and averaging a maximum NLR of 0.79 mg·d -1 for T avg >25 °C. NUTR and WDC had the lowest cumulative N losses over the season. Soluble salt readings paralleled N leaching for each CRF, indicating similar leaching patterns for other nutrients. Incorporation produced significantly higher cumulative N losses than topdressing, but without effect on the actual N leaching pattern over the season. Regardless of the N formulation in the CRF, over 85% of the N recovered in the leachates was in the nitrate form.