Influence of environmental factors on the weed flora in crops in the Guadalquivir Valley

Abstract

Summary:The study was conducted on the weed flora of the main irrigated crops of the Guadalquivir Valley. The TWINSPAN (Two Way Indicator Species Analysis) method was applied for each crop separately to all the species present as well as to their degree of infestation. The results indicated that soil texture may markedly influence the flora, whereas the effects of pH and carbonate content were less important. The climatic differences found in the three areas studied were of little importance. The type of irrigation markedly influenced the flora, although it was always related to edaphic factors, especially texture and slope.In general, the weed flora found in the crops can be divided into two communities. One is characterized by species such as Ridolfia segetum, Picris echioides, Phalaris brachystachys, Phalaris paradoxa and Chrozophora tinctoria and the second by Capsella bursa‐pastoris, Cyperus rotundus, Paspalum paspalodes, Digitaria sanguinalis, Sorghum halepense and Portulaca oleracea. The first community comprises weeds in the higher altitudes, further away from the riverbed, with a soil of clayey texture, a high slope and irrigated with sprinklers. The second community comprises the flora of flat areas, with sandy soils, located in the middle and low river terraces and furrow irrigated.