Flood cropland when fallow to conserve freshwater marshes
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
Background information and definitions
Flooding cropland during fallow seasons or years, when crops are not being grown, could allow wetland plant communities to develop temporarily. If this fallow period occurs within a yearly cycle, annual plant species will dominate. If the fallow period is long enough and at the right time of year, these species may be able to complete their life cycle within cropland.
Supporting evidence from individual studies
A replicated, site comparison study in 2005–2006 of six rice fields in southern Brazil (Rolon & Maltchik 2010) found that rice fields that were flooded when fallow contained a different wetland plant community to rice fields that remained drained when fallow, but with similar species richness and biomass. The overall wetland plant community composition in the rice fields depended on the combination of flooding regime (whether fields were flooded or drained when uncultivated) and survey period (whether fields were cultivated or fallow when surveyed; data reported as a graphical analysis). Flooded and drained fields supported statistically similar species richness (flooded: 4–12 species/1.5 m2/survey; drained: 2–15 species/1.5 m2/survey) and biomass (flooded: 1–85 g/m2/survey; drained: 1–35 g/m2/survey) of wetland plants. However, only 22–31 different wetland plant species were recorded in flooded fields over the study year, compared to a total of 31–44 in drained fields. Methods: Between June 2005 and June 2006, wetland vegetation was surveyed in six rice fields (six 0.25-m2 quadrats/field/survey). Surveys covered all stages of the rice cultivation cycle, including cultivated (field preparation and rice growth) and uncultivated (post-harvest and fallow) periods. All fields were flooded when cultivated. During the uncultivated periods three of the fields were flooded and three were drained. Above-ground vegetation collected from each quadrat was dried before weighing.Study and other actions tested