Nitrogen fertiliser value of digested dairy cow slurry, its liquid and solid fractions, and of dairy cow slurry

Abstract

An understanding of crop availability of livestock slurry nitrogen (N) is necessary to maximise crop N use efficiency and to minimise environmental losses. Results from field and laboratory incubation experiments suggest that first-year crop availability of slurry N comes mainly from its ammonium fraction because net mineralisation of organic N is often negligible in the short term. A two-year field experiment during 2011 and 2012 in northern Italy was undertaken with several aims: to estimate the N fertiliser value of raw dairy cow slurry, digested dairy cow slurry, and the liquid and solid fractions of the digested slurry, and to verify if applied ammonium recovery was similar both among slurries and between slurries and inorganic N fertiliser (ammonium sulphate).Different fertilisers were applied before silage maize cultivation followed by an unfertilised Italian ryegrass crop. The results showed that ammonium recovery was significantly higher in mineral-fertilised (75%) versus slurry-fertilised (30%) treatments, except in digested slurry (65%). This indicates that ammonium applied with organic materials is less efficient than when applied with mineral fertiliser. For the digested slurry and its liquid fraction, most of the applied ammonium was available to the maize during its application year (55%) due to a low carbon (C)/organic N ratio. The apparent N recovery of the raw slurry and digested slurry solid fraction increased substantially between the first (-1.4%) and second (20%) years, as these materials had high C/organic N ratios; they likely immobilised N for several months post application, producing residual effects during the Italian ryegrass and next maize crops. IntroductionRaw and anaerobically digested livestock slurries can be valuable fertilisers because they supply nutrients and organic matter to the soil.Anaerobic digestion of organic biomasses has seen considerable growth in Europe (Eurobserv'er, 2013) and in northern Italy (Fabbri et al., 2013) over the last decade.Many biogas plants co-digest livestock and biomasses to increase methane production, and in northern Italy, energy crops are often dedicated for co-digestion (Fabbri et al., 2013). To facilitate the use of digested slurries as fertilisers, liquid and solid fractions are separated to ease their transport (Möller and Müller, 2012).A deep understanding of applied slurry nitrogen (N) turnover in soil, and identification of practices to reduce N losses are required to maximise crop N use efficiency and to minimise environmental losses. Nutrient management plans (NMPs) maximise crop N use efficiency through calculation of the slurry amount needed for optimal crop production, and determination of application dates that match crop nutrient requirements according to soil type, local climate, and crop characteristics (Grignani et al., 2003). The slurry N fertiliser value is normally accounted for in a NMP by apparent nitrogen recovery (ANR), an expression of the fraction of applied total N that on average can be taken up by the cro...

Effects non-digested and anaerobically digested farmyard manures on wheat crop cultivated in desert soil

“…Makádi et al (2012) and Šimon et al (2015) confirmed that digestate has high available nutrients profile compared with non-digested, which resulted in significantly increased biomass yields of winter and spring wheat. Furthermore, it has been reported in several studies that the crop N uptake is higher with all types of digestate than non-digested manure if N losses by volatilization and leaching are prevented (Cavalli et al, 2014;Gunnarsson et al, 2010;Loria et al, 2007;Odlare et al, 2008). Moreover, humic acids in digestate are one of the most important organic fertilizers that increase N uptake and plant growth (Tahir et al, 2011).…”

Short-Term Nitrogen Uptake of Barley from Differently Processed Biogas Digestate in Pot Experiments

“…Laboratory and field experiments have been carried out with digestate in order to investigate N uptake of plants as well as the effect on soils regarding N mineralization, and often compared with mineral N fertilizers as control [19][20][21][22][23][24][25][26][27][28][29]. Other investigations focused on solid and liquid fractions of separated digestate regarding their use as fertilizer [12,[30][31][32][33]. Further studies show that digestate can also improve soil quality and water holding capacity on marginal soils [34] and that the use of fermentation residues is beneficial for selected plants such as tomato, pepper, kohlrabi or ornamentals.…”

Impact of nitrogen inputs on multiple facets of plant biodiversity in mountain grasslands: does nutrient source matter?

“…; Cavalli et al. ), the mineralization of the organic N can become non‐negligible over the long term (Gutser et al. ; Schröder et al.…”

“…However, the agronomic distinction between 'organic' (manure) and 'mineral' (industrial) fertilizers is misleading, since liquid manure contains high proportions of inorganic compounds, especially ammonium and phosphate, and easily mineralized soluble organic compounds, such as urea. Therefore, both industrial fertilizers and liquid manure present a high proportion of inorganic N available for plants in the short term (Muñoz et al 2004;Cavalli et al 2014).…”

“…Not considering the delayed effects of farmyard manure can lead to an underestimation of the N quantities supplied by these fertilizers over a few years (Kirkham et al 2008). While first-year N availability mainly comes from ammonium contained in liquid manure (Webb et al 2013;Cavalli et al 2014), the mineralization of the organic N can become non-negligible over the long term (Gutser et al 2005;Schr€ oder et al 2005), especially for solid manure (Muñoz et al 2004).…”