4.1. Seasonal changes of nitrogen and pH in soil and floodwater in rice
fields
In order to reduce N losses and develop more efficient
fertilization practices, seasonal changes in N content in rice
fields
need to be monitored. These seasonal changes are mainly caused
by agricultural practices, especially the N fertilization and
flooding
regime, but also the plant growth and soil type. And they may also
depend on climate characteristics. Unfortunately, such monitoring
has not been conducted in Portuguese rice
fields.
Portugal has a Mediterranean-type climate in its rice-producing
region. The typical rice management scheme during the last
fourteen years has involved the application of NH4 fertilizers
before sowing (basal dressing) and during the tillering stage
(topdressing) (Figueiredo et al., 2014).