Full text
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| Author(s): |
Thales Meinl Schmiedt Sattolo
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2016-01-14 |
| Examining board members: |
Rafael Otto;
Henrique Coutinho Junqueira Franco
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| Advisor: | Rafael Otto |
| Abstract | |
Nitrogen fertilizers play an important role in nutrition and increased productivity of sugarcane, however, affect cycling of C and N in the soil. This study mainly aimed to evaluate the effect of the consecutive application of organic and inorganic sources of N in microbial soil transformations, in N mineralization, in C, total N and mineral N stocks, and soil fertility in the medium term. They were chosen two areas cultivated with sugarcane in the State of São Paulo in which experiments with management of nitrogen fertilization have been conducted since 2010 and 2011, with annual reapplication of treatments through 2014. In these areas was adopted the randomized blocks experimental design, with four replications. The treatments were: control (no nitrogen fertilization), fertilization with sources of ammonium nitrate, urea, organic fertilizer and Ajifer® at rate of 100 kg ha-1 yr-1 N, and fertilization with YaraBella NitromagTM source at rates of 50, 100, 150 and 200 kg ha-1 yr-1 N. To evaluate the effect of treatments on the variation of soil fertility and hydrolysable organic-N fraction (N-ISNT), annual soil samples were collected in these experiments at 0-0.2 and 0.2-0.40 m. To evaluate the effect of treatments on soil C and N transformations, soil samples were collected up to 1.0 m depth in the control, organic fertilizers, YaraBella NitromagTM at rates of 100 and 200 kg ha-1 yr-1 N treatments and bushland, in which were determined bulk density and organic C, total N and mineral N (NH4+-N and NO2--N + NO3--N). In addition, soil samples of the 0-0.2 m were incubated in the laboratory to assess the availability of N and the content of C and N microbial biomass and microbial activity. The effects of consecutive nitrogen fertilizer were inexpressive in microbial transformations, in the temporal availability of mineral N and C and N soil stocks; however, it was observed mineral N accumulation in deeper layers (> 0.4 m) at rate of 200 kg ha-1 yr-1 N. Moreover, the bushland showed better microbiological attributes and largest C and N soil stocks compared with areas cultivated with sugarcane. In relation to the variation of soil fertility, it observed that the increase in N rates enhances the soil acidification in consecutive years, and promotes decreased levels of exchangeable bases. The maintenance of soil fertility, the microbiological attributes, and the C, total N and mineral N soil stocks for sustainable biofuel production depends on proper management of nitrogen fertilization on crop system of without burning sugarcane fields. Complementarily and in parallel with these studies, it was the object of study the adaptation and validation of colorimetric methods for the determination of inorganic N in tropical soil extracts. The results revealed that it is necessary to add activated charcoal during the extraction process so that colorimetric methods exhibit better accuracy and precision. It is recommended to use extraction solution of KCl 2,0 mol L-1 and allow 30 min reaction time between addition of reagent and the spectrophotometer reading. The linear working range more suitable varies from 0 to 7.5 and 0 to 10,0 mg L-1 of N for measurement of NH4+-N and NO3--N respectively. (AU) | |
| FAPESP's process: | 14/02604-3 - Effect of cumulative nitrogen fertilization on sugarcane (Saccharum spp.) cropped soils |
| Grantee: | Thales Meinl Schmiedt Sattolo |
| Support Opportunities: | Scholarships in Brazil - Master |