High irrigation frequency and transient NH4 concentration: effects on soilless-grown bell pepper

• Published in: The journal of horticultural science & biotechnology Vol. 80; no. 2; pp. 233 - 239
• Main Authors: Silber, A., Bruner, M., Kenig, E., Reshef, G., Zohar, H., Posalski, I., Yehezkel, H., Cohen, S., Dinar, M., Assouline, S.
• Format: Journal Article
• Language: English
• Published: Taylor & Francis 2005
• ISSN: 1462-0316; 2380-4084
• DOI: 10.1080/14620316.2005.11511923

The effects of irrigation frequency, N concentration, and NH 4 -N/NO 3 -N ratio on rhizosphere NH 4 concentrations and plant yield were investigated for bell pepper (Capsicum annuum L., cv. 'Mazurka') grown in perlite. The experiment comprised eight treatments, with two concentrations of N (120 or 60 mg l -1 ), two NH 4 -N/NO 3 -N ratios (3:7 and 1:9), and two irrigation frequencies (3 d -1 , or for 1.5 min every 30 min throughout the day). The combination of high NH 4 concentration in the irrigation water and high irrigation frequency reduced yield significantly. Decreasing the NH 4 concentration by decreasing the NH 4 -N/NO 3 -N ratio, or by decreasing the total N concentration, improved yield. The impaired growth of plants exposed to high irrigation frequency and high NH 4 concentrations was a result of high transient NH 4 concentrations in the rhizosphere. Time-dependent processes, such as nitrification, reduced transient NH 4 concentrations in the rhizosphere and, therefore, actual NH 4 concentrations were lower under low-frequency irrigation. Modification of the NH 4 /NO 3 ratio under high frequencies of irrigation is recommended to diminish the risks of NH 4 toxicity in sensitive crops.