RELAÇÃO ENTRE CARACTERÍSTICAS DE SOLOS DE VÁRZEA E A ABSORÇÃO DE NITROGÊNIO PELO ARROZ IRRIGADO EM DOIS CULTIVOS SUCESSIVOS EM CASA-DE-VEGETAÇÃO RELATIONSHIP BETWEEN LOWLAND SOIL CHARACTERISTICS AND NITROGEN ABSORPTION BY FLOODED RICE IN TWO SUCCESSIVE CULTIVATION IN GREENHOUSE

Soil organic matter (SOM) is the most important nitrogen (N) source to crops and its content is used to establish N fertilizer rates applications. However, SOM is not a good parameter to establish N fertilization to irrigated rice in lowland soils because the influence of aerobic and anaerobic cycles on SOM decomposition and N dynamic. The objective of this work was to evaluate the soil characteristics correlated with N absorbed by plants of flooded rice in two successive cultivations in greenhouse. Rice was cultivated using pots with 4 kg of soil from superficial layer (0-0.2m) of 15 lowland soils from Rio Grande do Sul (RS) state. Chemical and physical soil characteristics were correlated with absorbed N by plants. There was a wide variation in absorbed N by rice (24,7 to 307,7 mg of N pot -1 in the first cultivation and 9,84 to 113,6 mg of N pot -1 in the second), showing a wide N availability in lowland soils from RS. The organic C, total N, initial mineral N and clay content were correlated with N absorbed by plants whereas C/N relation and N-NH4 + e N-NO3