Avaliacao de luzernas anuais em solos acidos - estudo do efeito de alguns factores limitantes com vista ao melhoramento de plantas

The selection of ecotypes of medics for acid soils, which have great representation in Portugal, was done. This work began with germplasm collected in Portugal, sent by different research centres abroad and some commercial cultivars. Medicago polymorph was the most frequent species in Central and Southern Portugal. The agronomic evaluation was done with field trials on 5 soils (4 acid and 1 neutral). In slightly acidic soils, the greatest yields (dry matter and seed) occurred with M. polymorph, M. doliata, M. scutellata, M. tornata, M. littoralis and M. truncatula. In more acidic soils, only M. polymorph and M. murex grew, and rarely M. doliata, M. scutellata and M. truncatula. With the study of the genotype x environment interaction we identified the most stable ecotypes in terms of the answer to increases in environmental index and those that, though unstable, showed an increase of yield greater than the environmental index. These elements are very important to pursue the selection process. Using the same soils we studied with pot experiments the effects on plant concentration and export of some nutrients by different ecotypes, when liming was done or phosphorus was applied. Yields were greater in schist than in granite soils. In more acidic soils, some M. murex ecotypes proved to be better than the other species. There was a positive effect of liming seemed to result from a decrease in Mn uptake. In acid soils, M. murex removed more P extraction and less Mn than the other species, and therefore avoided Mn toxicity. The number of branches was the growth parameter that explained more adequately dry matter yield, more than length of longer branch or number of podsAvailable from Fundacao para a Ciencia e a Tecnologia, Servico de Informacao e Documentacao, Av. D. Carlos I, 126, 1249-074 Lisboa, Portugal / FCT - Fundação para o Ciência e a TecnologiaSIGLEPTPortuga