Inland water on soils with bad water balance can lead to serious yield losses. Soil management and plant protection is nearly impossible in these marshy vernal pools, wherefore very special vegetation develops. On the basis of 58 phytocoenological surveys made in South-Western Hungary the vegetation of the vernal pools will be characterised. From phytosociological point of view our surveys stand to Ranunculo sardoi-Alopecuretum geniculati and Myosuro-Ranunculetum sardoi associations the nearest, where the proportion of Nanocyperion elements is significant. The following endangered species occure in these vernal pools: Elatine alsinastrum, Limosella aquatica, Lindernia procumbens, Montia fontana, Peplis portula. However vernal pools in segetal fields are causing losses from economical aspects, they can contribute to increase agrobiodiversity and have an important role in maintaining numerous threatened and protected plant species (Red Data List, IUCN, Corine Biotopes Project, Bern Convention). © Eugen Ulmer KG.

Which factors are the most important determinants of weed species composition in organic rice fields? Which species can be associated with the extreme values of the most important background variables? To answer these questions, we surveyed the weed flora along with 15 management and 3 environmental variables in 42 organically managed rice fields in eastern Hungary. Filamentous algae, Chara vulgaris, Chara braunii, Schoenoplectus mucronatus, Elatine triandra, and Echinochloa crus-galli were the most dominant weeds. Using a minimal adequate model containing 4 terms with significant net effects, 48.3% of the total variation in weed species data could be explained. Farm holding size (correlated with sowing type, shift crop, organic manure and water depth) was found to be the most important explanatory variable, which was followed by hand weeding, tillage type (correlated with tillage depth, shift crop and supplementary nutrients) and rice cover. Farm holding size was negatively associated with most of the aquatic plants suggesting its adverse impact on farmland biodiversity. Hand weeding appeared to be efficient against Rumex stenophyllus and Echinochloa crus-galli, but it was tolerated by Cyperus difformis. Perennial weeds like Persicaria amphibia and Bolboschoenus planiculmis were more abundant in sites without soil inversion and Lemna aequinoctialis seemed to be most tolerant for the shading effect of crop canopy. The responses of weed species to the studied variables provide new information about the assembly rules of aquatic plant communities, and our findings also can be used to optimise non-chemical weed control strategies in organic rice production.

Organic rice farming has increasingly gained attention for its potential to enhance biodiversity compared to conventional agricultural methods. In this study, we examined the abundance of plant species groups of conservation interest in rice fields in Hungary, located at the northern periphery of rice cultivation. We compared organically and conventionally managed rice fields to determine their impact on plant biodiversity. Our results indicated that organic fields generally support a greater abundance of non-harmful macrophytes, charophytes, and red-listed species. However, these differences were less pronounced in fields considered less ecologically valuable, irrespective of management types. Our analysis revealed that water conductivity had a more significant impact than farming type. Lower conductivity correlated with weed communities of higher conservation values, particularly in organically managed fields. This effect was significant compared with conventional fields but was only evident in areas with relatively low conductivity, likely reflecting low nutrient levels in the water. These findings suggest that to maximize biodiversity benefits, organic agriculture should be practiced alongside the judicious use of low amounts of organic manure or nutrients. Such practices could enhance species-rich macrophyte communities, contributing to the preservation of the unique biodiversity found in this historic rice cultivation region.