Durum wheat-faba bean temporary intercropping: Effects on nitrogen supply and wheat quality

Intercropping cereals and grain legumes is a common practice because of the advantages in N use, in pest and volunteer plant smothering, but when the grains need to be separated, there are several technical difficulties. These problems may be overcome by adopting a particular form of intercropping (termed "temporary intercropping") where the coexistence of the crops is limited to a portion of their life cycles. In a cereal-legume temporary row-intercropping, the legume component is ploughed into the soil before cereal shooting: thus the legume is used with a mere fertility purpose in order to improve N availability for the cereal component. The presence of such a positive effect, already confirmed in permanent intercropping, needs to be verified in temporary intercropping systems. In an organic farming system, a field experiment was carried out in two consecutive years (2005 and 2006) to evaluate the technical feasibility of a temporary intercropping between three varieties of durum wheat (Triticum durum Desf.) and faba bean (Vicia faba L var. minor Beck.) and to test the effects on interspecific competition for light, N availability, cereal grain yield and quality. The species were temporarily intercropped following an additive design, and there was no fertilisation or crop protection. The N incorporated into the soil by the faba bean biomass was rather stable across years. The competitive effect of the legume reduced the biomass accumulation of the intercropped wheat, but the cereal N status was considerably improved. After the faba bean incorporation into the soil, the marked asymmetry of the temporary intercropped wheat (i.e. large inter-row space coupled with high plant density in the row) affected the radiation balance, nevertheless the yield was positively affected and the wheat grain protein content was increased to an excellent (from 12.0 to 13.9% in 2005) or a good (from 10.2 to 11.5% in 2006) level. Temporary intercropping was shown to be excellent method to improve the quality of organic durum wheat in the Mediterranean environmental conditions. (C) 2010 Elsevier Boy. All rights reserved.