Design and sustainability assessment of bioenergy double cropping system in southern Sweden
Abstract: Due to short growing season harvesting two crops sequentially in one year is not common in Sweden. In this experiment a cropping system was designed where rye was grown as a first crop for production of biomass feedstock for bioenergy. Aim of the study was to design a cropping system that can increase overall crop production and provide food, feed, energy and non-market ecosystem services such as increase annual carbon input and reduce leaching loss of nitrogen in the soil. With these ideas a field experiment was conducted in 2014-15 in Dybäck, southern part of Sweden. Rye was planted as first crop in September 2014 and harvested in green condition for energy production at the end of May, 2015. Blue lupin, soybean, black bean, lentil and buckwheat were selected as second crops and were grown in between June to September, 2015. It was an interdisciplinary research work. Both quantitative and qualitative methods were used for this study. A literature search was conducted to collect preliminary data to assess sustainability of double cropping system using Sustainability Assessment of Food and Agriculture systems (SAFA) as a concept. Quantitative method was used for determining crop yield and crop residues. Qualitative method was used to investigate possible motives and constraints that might influence farmers’ decision to adopt double cropping system through semi-structured interviews. According to the literatures reviewed, conventional double cropping system requires a high level of water consumption and fertilizer utilization. This system also emits a high quantity of GHG. However, due to high soil coverage the system may enhance soil quality and protects soil from land degradation. Double cropping system also supports a large number of diverse species such as beetles and spiders. Increase yield could result in rise in net income. It should be noted that overall outcome of the double cropping system can greatly vary depending on the country/region, climate, soil, choice of the crops/varieties and, cultivation system (irrigated/non-irrigated, tillage/non- tillage, organic/conventional). Grain yield of lentil was highest (1.7 t/ha) among all the crops. Grain yield of buckwheat, black bean, soybean and blue lupin were 1.3 t/ha, 0.9 t/ha, 0.6 t/ha and 0.5 t/ha respectively. Production of crop residues was highest in buckwheat (3.2 t/ha). Crop residues production of lentil, black bean, soybean and blue lupin were 2.1 t/ha, 1.1 t/ha, 1.1 t/ha and 0.8 t/ha respectively. Highest annual C input in the soil was determined in buckwheat (304.2 kg/ha). Annual C input in the soil by lentil, blue lupin, black bean and soybean were 214.5 kg/ha, 121.7 kg/ha, 107.7 kg/ha and 101.2 kg/ha respectively. Amount of available N was determined for three crops: buckwheat, lentil and soybean at the depth of 0-60 cm. Total amount of available nitrogen in buckwheat, soybean and lentil were 14.3 kg/ha, 11.3 kg/ha and 9.6 kg/ha respectively. Crops residues are suitable for animal feed and energy production. Results from five interviews demonstrated that absence of market, lack of suitable machineries to handle second crops and lack of knowledge of double cropping system might be the major barriers of potential adoption of bioenergy double cropping system by the farmers who are growing rye for production of biomass feedstock for bioenergy production.
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