Double-cropping systems based on rye, maize and sorghum: Impact of variety and harvesting time on biomass and biogas yield

Climate change affects the frequency and intensity of extreme weather, the results of which include production losses and climate-induced crop productivity fluctuations. Double-cropping systems (DCSs) have been suggested as a way to increase biomass-production while simultaneously delivering environmental benefits. In a three-year field-test, two DCSs based on maize and sorghum as the main crop and rye as the preceding winter crop were compared with each other and compared with 2 single-cropping systems (SCSs) of maize or sorghum; there were comparisons of growth dynamics, optimal harvesting and growing time as well as biomass and methane yield. In addition, the impact of variety and harvest time on the winter rye optimal biomass yield was studied. The experiments clearly showed the superiority of the DCS over the SCS. Within the DCS, the rye/sorghum combination achieved significantly higher biomass yields compared to those of the rye/maize combination. The highest dry matter biomass yield was achieved during year 1 at 27.5 +/- 2.4 t.ha(-1), during which winter rye contributed 8.3 +/- 0.7 t.ha(-1) and sorghum contributed 19.2 +/- 1.8 t.ha(-1). At the experimental location, which is influenced by a Pannonia climate (hot and dry), the rye/sorghum DCS was able to obtain average methane yields per hectare, 9300 m(3), whereas the rye/maize combination reached 7400 m(3). In contrast, the rye, maize and sorghum SCSs achieved methane yields of 4800, 6100 and 6500 m(3) ha(-1), respectively. The study revealed that the winter rye and sorghum DCS is a promising strategy to counteract climate change and thus guarantee crop yield stability.