Dynamics of soil organic matter in Panicum virgatum sole crops and intercrops

Soil organic matter (SOM) is one of the primary indicators of soil quality, which plays an important role in enhancing a range of soil physical, chemical and biological functions in the agricultural ecosystem. Switchgrass cultivation for bioenergy has the potential to improve and stabilize soil properties on marginal land over the years. The research was aimed to evaluate the dynamics of SOM in different types of switchgrass cropping systems and the influence of SOM on switchgrass productivity. The experiment was performed on a marginal land in the central part of the forest-steppe zone of Ukraine. The switchgrass (Panicum virgatum L.) cultivar 'Cave-in-Rock' was used. The experiment included two factors. Factor A - type of cropping: 1) sole crops of switchgrass (Sw) - control; 2) strip intercropping of switchgrass and lupine (Sw + strip); 3) mixed intercropping of switchgrass and lupine (Sw + mix). Factor B - years of switchgrass cultivation (2010-2016). It was demonstrated that perennial switchgrass cultivation has the potential to increase SOM content. SOM content in Sw + strip crops increased by 0.12%, in Sw + mix - by 0.09% and in Sw - by 0.07%. The highest switchgrass productivity was formed in Sw + strip (from 1.11 to 1.53 kg m(-2)) and in Sw + mix (from 1.12 to 1.45 kg m(-2)) crops, the lowest - in Sw (from 0.85 to 1.34 kg m(-2)) crop. The maximum switchgrass productivity was observed for 5-7 years of cultivation. The highest height of plants and number of shoots of switchgrass were in Sw + strip crops, and significantly less in the other treatments. The results of the experiment showed a great increase of switchgrass productivity and SOM content in switchgrass crops and confirmed that switchgrass can be a sustainable energy crop.