Utilizing woody materials for fungal-based management of soil nitrogen pools

Application of nitrogen fertilizers to reach high crop production is
common practice. However, this can come with an environmental cost,
irrespectively of the synthetic or organic origin of the nitrogen
fertilizer. Intensively managed soils often fail to retain excess
nitrogen, which leads to contamination of ground- and surface water. Next
to abiotic factors like soil texture, limited nitrogen retention is
ascribed to low activity of saprotrophic fungi. It has been shown that
amendment of arable soils with cellulose-rich materials can effectively
stimulate resident saprotrophic fungi. The current study investigated the
relationship between fungal dynamics (biomass, composition) and nitrogen
immobilization-remobilization dynamics upon soil amendment with woody
materials Mineral  nitrogen pools, ergosterol and ITS2 amplicon
sequences were analyzed during a 6-months pot experiment. Carbon-rich
amendments included sawdusts of deciduous (beech, willow) and coniferous
(Douglas fir, larch) tree species, beech wood chips, wheat straw and
combinations of these materials. Excess nitrogen derived from addition of
either mineral or organic fertilizer. Deciduous wood sawdust resulted in
rapid stimulation of fungal biomass, mainly consisting of saprotrophic
Sordariomycetes. This was accompanied by a reduction in the mineral N pool
equivalent to  24–60 kg N ha-1 for four to over six months. The
intensity of nitrogen immobilization depended on sawdust application rate
and the type of fertilizer. Single amendments of coniferous sawdust and
beech wood chips had minor effects, but led to prolonged nitrogen
retention when combined with beech sawdust. Our conclusion is that,
fungus-stimulating woody soil amendments  have great potential to
increase nitrogen use efficiency in arable soils.