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Grasses are good at using the sun to be productive

Scientists from Aarhus University have studied how efficient crops are at using the sun to produce biomass for biorefining. This knowledge can be put to use to optimise biomass yields and improve sustainability.

2017.03.13 | Janne Hansen

Over a period of three years, the scientists conducted field studies with various crops and cropping systems. Photo: Jesper Rais

Agriculture is no longer only a question about producing grain and vegetables for food and feed. There is a growing interest in using land to produce crops for other products as well, without compromising food and feed production. This development calls for radically novel cropping systems that are adapted to growing crops for biomass for food, feed and biorefining into other products, such as energy and materials and protein.

A question that naturally arises is which crops are the best to grow for this purpose. In other words, which plants are most efficient at using their photosynthesis to transform energy from the sun into more and useful biomass? 

Which crops are most efficient?

Scientists from Aarhus University have been seeking answers to this question as a part of the research platform BioValue Spir

- We have investigated agroecological and environmental features of potential crops as candidates for biorefinery in Denmark with the aim of sustainable intensification, which in popular terms means “more with less”, in addition to sustainable extensification, says a member of the scientific team from the Department of Agroecology at Aarhus University postdoc Kiril Manevski. With his colleagues from Aarhus University he has worked on the BioValue subproject concerning delivery of plenty and sustainable biomass of a good quality for biorefining.  

The results of their investigations show that high biomass yields can be achieved if cropping systems are carefully optimised for this purpose. Over a period of three years, the scientists conducted field studies with various crops and cropping systems comprising novel perennial grasses, annual crops in rotations optimised for biomass production, and traditional Danish cropping systems under various soil and climatic conditions.

The perennial grasses included systems with intensive nitrogen fertilization, low nitrogen fertilisation and no nitrogen fertilisation. The optimised rotations of annual crops included maize, beet, hemp, triticale, winter rye and winter rapeseed, while the traditional cropping systems included monocultures of maize and triticale and a rotation of spring barley, winter barley and winter rapeseed.  

Grasses are good

The highest biomass yields were achieved with intensively fertilised perennial grasses and in the optimised rotation system; the very highest yields were obtained from beet, festulolium and tall fescue. It must be noted that traditional maize monoculture produced high biomass yields. However, the novel systems have an ace up their sleeve compared to traditional maize: they have less impact on the environment. 

- Although traditional maize produced similar or higher biomass yields than the novel cropping systems, the novel systems are expected to reduce environmental impact and have positive effects on biodiversity, says Kiril Manevski.

The perennial crops were fertilised with large amounts of nitrogen, yet offset it by producing high biomass yields with a high nitrogen content at a low environmental cost with regard to nitrate leaching. Similar findings of large biomass production and nitrogen content and low nitrate leaching were seen for the optimised rotation system. The high nitrogen content is useful if the biomass is destined for biorefining into protein products.

The researchers also considered how efficient the crops were not only at intercepting sunlight but also at using it to produce biomass– the so-called radiation use efficiency (RUE). If there are variations in RUE, there is a potential for breeding for optimal RUE by genetic improvements, or by creating conditions for the crop so that it can optimise its RUE.        



- Our results can pave the way for more diversified cropping systems. However, the farmer’s decision to do so should be supported by a sound agro-economic analysis with regard to market demands, production costs and biomass prices, says Kiril Manevski.

Further information 

Read the article: Biomass productivity and radiation utilisation of innovative cropping systems for biorefinery in Agricultural and Forest Meteorology.

Postdoc Kiril Manevski
Department of Agroecology, AU
Email: kiril.manevski@agro.au.dk
Phone: 8715 7795

Senior Scientist Uffe Jørgensen
Department of Agroecology, AU  
Email: uffe.jorgensen@agro.au.dk
Phone.: 87157729
Mobile: 21337831

Agro, DCA