Coexistence of rice production and threatened plant species: testing Marsilea quadrifolia L. in N-Italy

In the past, the aquatic pteridophyte Marsilea quadrifolia L. was considered as a weed in paddy fields of southern Europe. The systematic use of herbicides as a crucial component of intensive agronomic approach has led to a dramatic decline in M. quadrifolia populations in European countries, mostly in the Mediterranean area. However, the introduction in recent years of sustainable rice cultivation practices has allowed partial recovery. We present here the results of a research aimed at analyzing the effects of farming typologies in respect to M. quadrifolia growth in the Po Valley area. After having transplanted M. quadrifolia swards in rice fields belonging to different farming systems, we monitored its growth and diffusion. Our results showed that M. quadrifolia has higher vegetative performance in organic farms, even though it can survive in conventional fields with reduced herbicide supply. Differences in water chemistry have limited effects on M. quadrifolia performance, because of its wide ecological amplitude. The shady conditions provided by rice canopy create micro-habitats suitable for M. quadrifolia growth. Cultivating M. quadrifolia in organic rice farms represents an important opportunity for preserving this endangered species in areas of intensive agriculture. This can, meanwhile, represent a valid opportunity to combine nature conservation and productivity offering a new possible income for farmers.