Tese
Disponibilidade do nitrogênio em solos de várzea e parâmetros da planta para avaliação nutricional da cultura do arroz irrigado
Fecha
2012-08-31Registro en:
POCOJESKI, Elisandra. Nitrogen availability in lowland soils and plant parameters for nutritional evaluation of flooded rice crop. 2012. 85 f. Tese (Doutorado em Agronomia) - Universidade Federal de Santa Maria, Santa Maria, 2012.
Autor
Pocojeski, Elisandra
Institución
Resumen
The present work aims at assessing the nitrogen mineralization in aerobic and
anaerobic conditions in an incubation experiment and monitoring the N level in plants by the
use of chlorophyll meter in order to establish a critical value of the SPAD (Soil Plant Analysis
Development) reading for flooded rice crop. Two studies were carried out being one in the
lab, with incubation of different kinds of rainfed and lowland soils, in humid and flooded conditions. Nine evaluations of N-NH4 + e N-NO3 - content were carried out. Parallelly, an experiment in the greenhouse has been carried out by using the same soils in the same
conditions as the rice crop. At the end of the experiment the green/dry matter, Nitrogen
content in the plant tissue and accumulated Nitrogen were determined. For the second study,
three field experiments were developed in the crops of 2006/07; 2007/08 and 2008/09, with
flooded rice cultivars. For the experiment 1, six limits of values in the chlorophyll meter were
established as treatment in the R0 stage and six doses for the 1st topdressing fertilization.
Assessment with the chlorophyll meter was carried out and when necessary, nitrogen was
applied in order to reach the pre-established reading values in R0. For the experiments 2 and
3, different doses of N were used for the 1st and the 2nd topdressing fertilization, one after the
readings were done with chlorophyll meter. For the study 2 green/dry matter, N contend in
the tissue and accumulated N were also determined. In study 1 the flooded soils presented the highest N-NH4
+ contends released during the experiment. The highest N-NO3
- contends were lowland soils, once the soils presented the highest SOM contends, they also presented
the highest contends of N-NH4 + and N-NO3 -. The accumulated N mineral at 102 day in the
lowlands was higher when maintained under flood and rainfed when kept humid. The best
correlation was obtained between the N-mineral contend and the accumulated N in the plant
tissue. For the experiment 1 of the study 2 there was a linear reaction between values of the
chlorophyll meter readings in R0 and the N contend in plants, however, the grain productivity
had a quadratic behavior when related to the chlorophyll meter readings, being the
estimated the critical value of the reading of 36 SPAD units in R0. For the experiments 2 and
3 of the study 2 there was effect of the 1st and the 2nd application of N demonstrated by the
chlorophyll meter readings, nevertheless, as the time passed by the readings were similar for
all treatments. The green and/or dry matter and the accumulated N responded linearly to the
doses of N. there was no interaction effect for the doses of N in the grain productivity in both
experiments and its answer was quadratic. The nutritional state evaluation of the plants by
the chlorophyll meter, alone, is not a good indicator of the general conditions of the crop and
the green or dry matter might help in the interpretation of the results for a better adjust in the
topdressing N fertilization.