Nitrogen-fertilizer forms affect the nitrogen-use efficiency in fertigated citrus groves

• Published in: Journal of plant nutrition and soil science 2014-06, Vol.177 (3), p.404-411
• Main Authors: Quaggio, José Antônio, Souza, Thais Regina, Bachiega Zambrosi, Fernando César, Marcelli Boaretto, Rodrigo, Mattos Jr, Dirceu
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; ammonium; Biological and medical sciences; calcium; Citrus fruits; Citrus sinensis; Efficiency; fruit yield; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; nitrate; Nitrogen fertilization; Nitrogen, phosphorus, potassium fertilizations; Physical properties; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Poncirus trifoliata; Soil science; soil solution; Soil-plant relationships. Soil fertility; Soil-plant relationships. Soil fertility. Fertilization. Amendments; Water and solute dynamics
• ISSN: 1436-8730; 1522-2624
• DOI: 10.1002/jpln.201300315

The fertigated area of the Brazilian citrus industry has grown rapidly during recent years, and an efficient management of nitrogen (N) application at these sites is required for sustainable citrus production. Therefore, a field trial with Valencia orange trees [Citrus sinensis (L.) Osbeck] on Swingle citrumelo rootstock (Citrus paradise Macfad. x Poncirus trifoliata L. Raf.) was conducted for 8 years to evaluate the effects of N rates (80, 160, 240 and 320 kg ha–1 y–1) applied by fertigation, either as ammonium nitrate (AN) or calcium nitrate (CN), on soil solution dynamics, fruit yield, nutritional status, and N‐use efficiency (NUE) of trees. The maximum fruit yield was reached with 240 kg N ha–1 for AN, whereas a linear response and greater fruit yield was observed for N supplied as CN. The NUE was reduced for both N forms with increasing N rates. However, the NUE for CN was 14 to 38% greater than the NUE for AN. The lower fruit yield and NUE for AN compared to CN‐treated trees was associated with the increased acidification of the soil solution with increased AN rates (pH ≤ 4.0). This limited nitrification resulted in a high ammonium (NH$ _4^+ $) concentration in the soil solution and a reduction in the net absorption of cations by the trees, particularly calcium (Ca). Due to the improved ion balance as well as the higher pH of the soil solution (pH ≥ 6.3) and diminished NH$ _4^+ $ availability, gains in both fruit yield and NUE in fertigated citrus groves in tropical soils can be obtained with the use of CN as a source of N.