"Preferential" ammonium uptake by sugarcane does not increase the N-15 recovery of fertilizer sources

Author(s)

Boschiero, Beatriz Nastaro ; Mariano, Eduardo ; Ocheuze Trivelin, Paulo Cesar

• Document type: Journal article
• Source: PLANT AND SOIL; v. 429, n. 1-2, p. 17-pg., 2018-08-01.

Abstract

Aims As ammonium (NH4+) has been reported as the "preferred" mineral N source for sugarcane (Saccharum spp.), the predominant supply of NH4+ has been hypothesized as a means of increasing the N-15 recovery and crop yield. We aimed to evaluate the N-15 recovery by sugarcane as affected by N-15-NH4+ and N-15-NO3- addition. Methods Under field conditions, N-15-labeled ammonium nitrate [labeling as (NH4NO3)-N-15 (N-15-NH4+) and NH4 (NO3)-N-15 (N-15-NO3-)] and urea were surface-applied at a rate of 100 kg N ha(-1). Under controlled conditions, sugarcane was grown in hydroponic medium (containing unlabeled N) until the maximum N demand period. Subsequently, plants received N-15-NH4+ or N-15-NO3- (as ammonium nitrate). Plants were then sampled at 1, 3, 7, and 15 d after fertilization (DAF) to estimate N-15 recovery. Results Under field conditions, the N-15 recovery for urea was lower than that for ammonium nitrate, partly explained by ammonia volatilization, but there was no difference in N use efficiency between the two fertilizer N sources, as well as between N-15-NH4+ and N-15-NO3- supply. Under controlled conditions, however, N-15-NH4+ resulted in higher N-15 recovery than N-15-NO3- until 7 DAF. Nevertheless, as N-15-NH4+ became depleted in the nutrient solution, N-15-NO3- was taken up more intensely by the crop. At 15 DAF, highest N-15 recovery was detected in the roots and whole plant under N-15-NO3- supply. Conclusions Although uptake of NH4+ is faster than NO3-, the so-called "preference" for NH4+ by the crop did not necessarily translate into higher N-15 recovery. Therefore, we suggest that the term "preference" should be used with caution to avoid misinterpretation. (AU)

• FAPESP's process: 13/17278-1 - Nitrogen fertilization of sugarcane ratoon: long-term effects of sources and rates of nitrogen fertilizers
• Grantee: Beatriz Nastaro Boschiero
• Support Opportunities: Scholarships in Brazil - Doctorate