Weed infestation of cereals in selected organic and conventional farms in Opole region [Poland]

agricultura tradicional agriculture biologique agriculture traditionnelle cereal crops cultivos de cereales cultivos de invierno cultivos de primavera culture d'hiver culture de printemps dominant species especies especies dominantes exploitation agricole explotaciones agrarias farming systems farms infestation malezas mauvaise herbe organic agriculture poland pologne polonia species spring crops traditional farming variedades varieties weeds winter crops