Ursachen höherer Backqualität von Winterweizen (Triticum aestivum L.) im Gemenge mit Winterackerbohne (Vicia faba L.) oder Wintererbse (Pisum sativum L.)

Abstract

Monocropped and intercropped winter wheat (Triticum aestivum L.) either with winter faba bean (Vicia faba L.) or winter pea (Pisum sativum L.) were evaluated in a two year field experiment (2003/2004 and 2004/2005) by complete randomized block designs. The locations were two long-time organically managed experimental stations of the University of Göttingen: Reinshof, brown warp soil, silty loam and Deppoldshausen, shelly limestone decomposition, silty loam and an organic farm in Stöckendrebber, alluvial sand, loamy sand. Wheat variety Bussard in pure stand was cultivated with 300 (100 %) or 60 (20 %) kernels per m² as well as varied in 15, 30 or 75 cm row distance. The grain legumes winter faba bean (variety Hiverna) and winter pea (variety Cheyenne) as sole crops were grown at 30 and 80 kernels per m², respectively. The substitutive mixtures were established with 20 % wheat and 80 % legumes of the recommended density and the different spatial arrangements (mixed intercropping, row intercropping or row strip intercropping). The crops were not treated with manure. On wheat growth stage BBCH 25, 65 and 89 crop harvests and soil samplings for yield and Nmin analyses were undertaken. The quality parameters of wheat flour such as protein content, wet gluten content, SDS sedimentation value, volume in micro backing test and falling number were determined. Furthermore, N-yield, N2-fixation of the winter grain legumes, transfer of symbiotically fixed nitrogen from legumes to wheat and the N-Balance were calculated.Monocropped wheat grown with 60 kernels per m² reached same yields as monocropped wheat grown with 300 kernels per m² because of compensation by tillering and grains per ear. The grain yield of monocropped wheat amounted between 2,4 and 43,3 dt DM ha-1. The legumes generated grain yields between 27,2 and 67,3 dt DM ha-1 and 13,2 and 34,6 dt DM ha-1, faba bean and pea respectively. Grain yields in mixture were normally lower for both species. However the relative yield total (RYT) in mixture was usually greater 1. Mixtures outvalued both respective sole crop yields only in one location (Stöckendrebber). The factor row distance had no effect on grain yield except for location Reinshof in the year 2004. There was a strong competition of faba bean to wheat on the location Reinshof. It was shown by low yields, low crowding coefficients and thousand kernel weights of wheat in mixture with faba bean.The quality of wheat in mixtures especially with faba bean in row strip intercrop increased in protein content up to 15,3 % in grain over the sole cropped wheat. In average of all locations and years protein contents of wheat were 9,2 and 9,8 % in 100 % and 20 % sole crops and 12,3 and 10,6 % in mixture with faba bean and pea. Increased row distance up to 75 cm (10,9 % protein content in average of all locations and years) also led to improved wheat quality compared to 15 and 30 cm row distance (10,2 and 10,4 %). There were positive correlations between protein content and the other quality parameters except the falling number. As a result of the pod parts in whole kernel flour the SDS sedimentation values were high (50 to 95 ml) and the volume in micro backing test were low (220 to 320 ml per 100 g flour).The investigations have demonstrated that a temporal and spatial Nmin gradient in soil by competition with grain legumes caused in a better backing quality of the wheat grown in mixture. That was the fact in monocropped wheat with row distance of 75 cm and particularly in row strip intercrop. Moreover the wet gluten content was depending on Nmin content at anthesis. Transfer of symbiotically fixed nitrogen by faba bean up to 10,2 kg N ha-1 and pea up to 13,1 kg N ha-1 were verified in wheat biomass (Reinshof 2004), which probably increased quality of wheat grown in mixtures. In addition there was a positive regression of the wet gluten content from N content at anthesis.Monocropped faba bean assimilated 313,1 kg N ha-1 nitrogen from atmosphere (N2-fixation) and 109,6 kg N ha-1 from soil on average (Reinshof 2004). In biomass of sole pea at ripening on average 111,4 kg N ha-1 from N2-fixation and 28,7 kg N ha-1 from soil assimilation were determined (Stöckendrebber 2005). In mixtures the N2-fixation and the N-assimilation from soil of the legumes were lower than in sole crop. However the proportion of nitrogen derived from the atmosphere (Ndfa) was higher in mixture than in sole crops.