Determination of field capacity in situ or by regression equations

Abstract

This work was developed in order to test the global equations obtained by Macedo to determine the in situ field capacity (FC) in a Typic Kanhapludalf soil; to evaluate the flux chamber developed by Fabian & Ottoni Filho; and to verify how the FC values obtained with this equipment compare to the values determined through the method of Embrapa. The tests took place in 1994, in a Typic Kanhapludalf soil, in Itaguaí, RJ, Brazil. The motivation for such a comparison is the fact that water lateral movement is practically eliminated inside the chamber. It was confirmed that the FC values measured in such an equipment, reproduced the FC determinations obtained through the methodology of Embrapa. As the area of the chamber is 0.50 m², the result suggests the possibility of decrease in the flooding basin dimension. The regression global equations obtained by Macedo were validated, determining FC based on textural and organic matter percentages, or based on microporosity (60 cm tension-soil moisture).