Abstract
Nitrogen fertilization is a major component of the cost of agricultural production, due to the high cost and low efficiency of fertilizers. In the case of urea, the low efficiency is mainly due to losses by volatilization, which are more pronounced in cultivation systems in which plant residues are left on the soil. The objective of this work was to compare the influence of urea coated with sulfur or boric acid and copper sulfate with conventional N fertilizers on N volatilization losses in sugar cane harvested after stubble burning. The sources urea, sulfur-coated urea, urea coated with boric acid and copper sulfate, as well as nitrate and ammonium sulfate, were tested at amounts containing N rates of 120 kg ha-1 N. The integration of new technologies in urea fertilization can reduce N losses by volatilization. These losses were most reduced when using nitrate and ammonium sulfate. The application of a readily acidified substance (boric acid) to urea was more efficient in reducing volatilization losses and nutrient removal by sugar cane than that of a substance with gradual acidification (elemental sulfur).
Highlights
Environmental laws encourage the adoption of harvest forms of sugarcane that dispense the previous burning of the crop stubble, which reflects back on the fertilization practices, in terms of amounts and of sources and application forms
The experimental design in randomized blocks consisted of six treatments: CT, UR, ammonium nitrate (AN), UBC, ammonium sulfate (AS), and sulfur-coated urea (SU), with four replications All treatments were fertilized with N, K2O and P2O5 corresponding to 120, 100 and 30 kg ha-1, respectively
To estimate N losses by ammonia volatilization from soil after N fertilization, we used the direct method with semi-open collectors (Nômmik, 1973) in a dynamic mode, i.e., changing the chamber of the collectors to the subsequent bases (PVC rings by which collectors are fixed to the ground) and the integration of correction factors proposed by Lara Cabezas et al (1999)
Summary
Environmental laws encourage the adoption of harvest forms of sugarcane that dispense the previous burning of the crop stubble, which reflects back on the fertilization practices, in terms of amounts and of sources and application forms. Nitrogen (N) is a very dynamic element in the soil and as such can get lost by one or several processes, e.g., volatilization, leaching, denitrification, runoff, and crop removal (De Datta, 1981). The losses of ammonia nitrogen (NH3-N) from urea applied to the surface are significant in soils with tropical and subtropical climate, due to the climatic conditions such as high temperatures, winds and high relative air humidity (Oliveira et al, 2007). In a study by Cantarella et al (1999), 12 and 30 %, respectively, of the NH3 -N of the urea fertilizer applied on sugarcane straw, at 50 and 100 kg ha-1 N, was lost by volatilization. Costa et al (2003) and Vitti et al (2007a) reported losses of more than 30 % of the N applied to straw cane In a study by Cantarella et al (1999), 12 and 30 %, respectively, of the NH3 -N of the urea fertilizer applied on sugarcane straw, at 50 and 100 kg ha-1 N, was lost by volatilization. Costa et al (2003) and Vitti et al (2007a) reported losses of more than 30 % of the N applied to straw cane
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