Licentiate thesis, 2012
Nutrient supply to reed canary grass as a bioenergy cropLindvall, Eva
AbstractProduction of renewable energy from herbaceous crops on agricultural land is of great interest since fossil fuels need to be replaced with sustainable energy sources. Reed canary grass (RCG), Phalaris arundinacea L. is an interesting species for this purpose. The aim of this thesis was to study different approaches to reduce the requirement of mineral fertilizers in RCG production for bioenergy purposes. Paper I describes a study where fertilization effects and risk of heavy metal enrichment were studied, using annual applications of ash for seven years. Ash from co-combustion of RCG and municipal wastes (mixed ash), pure RCG ash and commercial fertilizers were compared. The experiment was harvested each spring. Paper II describes an ongoing study in which the effects of intercropping RCG in mixture with nitrogen-fixing perennial legumes are examined in two experiments, in combination with various fertilization treatments. Three fertilization treatments were applied: high N, low N (half of the high N) and low N + RCG ash/sewage sludge. A delayed harvest method was used; cutting the biomass in late autumn and harvesting in spring. Besides dry matter yield, the N-fixation rate was estimated. The results from paper I showed no differences between treatments in the dry matter yields or in the heavy metal concentrations in the biomass. Soil samples, taken when the experiment was finished, showed differences between treatments for Cd, Pb and Zn only in the uppermost soil level, highest levels for the mixed ash treatment. The results in paper II showed that at one site the legume proportion in the mixtures was low and did not affect RCG growth negatively. The high N treatment gave a higher spring yield than the low N treatments. Mean rates of N2-fixation in the first production year were 12-28, 33-40 and 55 kg N ha-1 kg for goat´s rue (Galega orientalis Lam.), red clover (Trifolium pratense L.), and alsike clover (Trifolium hybridum L.), plots, respectively. At the other site, competition with higher proportion of the clovers affected RCG growth and spring yield negatively. The N-fixation rates were 33 - 42 kg N ha-1 for red clover and 24 kg N ha-1 for alsike clover. As a conclusion, pure RCG ash can be used to complement mineral fertilizers in RCG crops, but it is important to analyse the ash for plant nutrients and heavy metals before use. There was no spring yield benefit of legume/RCG intercropping. Thus, the method cannot be recommended in a spring harvest system, at least not under the tested conditions.
Keywordsbiofuel; nitrogen fixation ; ash fertilization; reed canary grass; delayed harvest; heavy metals; intercropping with legumes
Publisher: Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences
Swedish University of Agricultural Sciences, Department of Agricultural Research for Northern Sweden
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