Malas hierbas de cultivos de regadío del suroeste de Castilla y LeónPropuesta de un nuevo índice malherbológico

Resum

Weeds growing in irrigated crops in Salamanca and Zamora provinces (CW Spain) have been studied to the aim of getting an assessment on which of them are more abundant and frequently found. The distribution of weeds in the different types of crops (lucerne, sunflower, corn, potato, sugar beet and other sixteen less important crops) that have been here surveyed has been also studied, as well as their incidence in the rich fluvial lowlands (Águeda and Tormes in Salamanca, Duero and Esla-Órbigo-Tera in Zamora) and in an area irrigated by subterranean water (Peñaranda de Bracamonte in Salamanca). A new method to quantify weed infestation is proposed. It consist of a decimal scale of indexes of risks of weed harmfulness (IRN) ranging from 0 to 100, which is graphically represented by a «cube of risks of weed harmfulness». This index comprises three weed parameters: relative frequence of incidence (FRP), maximum covering index (IMC) and one new parameter, frequence of high covering (FAC). Four hundred and twelve fields have been studied, where 331 taxa have been found. Three groups of species have been established in relation to their harmfulness potentiality and also according to their IRN. High risk of harmfulness has been found in 17 species considerin the whole of the crops and areas surveyed, from which 5 represent the highest risk of harmfulness and have been found in all types of crop and agricultural areas: Chenopodium album L., Echinochloa crus-galli (L.) Beauv., Solanum physalifolium var. nitidibaccatum (Bitter) Edmons, Amaranthus powellii S. Watson and Digitaria sanguinalis (L.) Scop.