Effect of injection depth of digestate liquid fraction on soil carbon dioxide emission and maize biomass production

Abstract

The aim of this study was to evaluate, in open field conditions, the effect of injection depth of digestate liquid fraction (10 cm, 25 cm and 35 cm) in clay loam soil, on CO2 emission. An un-amended soil was considered as control. The study was performed in 2014 on a farm located in Terrasa Padovana, Veneto region (Italy) distributing digestate before maize sowing.Digestate injection determined a high soil CO2 emission in the first hour after application, followed by a progressive reduction in as early as 24 h, reaching significantly lower values, similar to those measured in the un-amended control, after 48 h. Gas emissions measured 1 h after digestate application decreased as injection depth increased with significantly higher emission values in the 10 cm treatment (median value 23.7 g CO2 m -2 h -1 ) than in the 35 cm one (median value 2.5 g CO2 m -2 h -1 ). In the 3 days between digestate distribution and maize sowing, soil CO2 emission was significantly higher in the amended treatments than un-amended one, with median values of 1.53 g CO2 m -2 h -1 and 0.46 g CO2 m -2 h -1 respectively. During maize growing season, no significant soil CO2 emission difference was monitored among treatments, with a median value of 0.33 g CO2 m -2 h -1 .Digestate application significantly improved maize aboveground dry biomass with an average yield of 22.0 Mg ha -1 and 16.2 Mg ha -1 in amended and un-amended plots, respectively, due to the different amount of nutrients supplied. IntroductionIntensive soil fertilisation with mineral fertilisers has led to several issues, like loss of soil carbon (C), and nitrogen (N) leaching (Borin et al., 1997;Nardi et al., 2004;Morari et al., 2006). Fertilisation with organic wastes therefore represents an alternative for sustainable agriculture (Casacchia et al., 2012;Marchetti et al., 2012;Morra et al., 2013;Barbera et al., 2013;Nkoa, 2014). In this context the agricultural reuse of digestate, organic waste product of biogas plants, should be considered. Furthermore, the sustainability of biogas production may depend on an appropriate end-use of the downstream effluents of anaerobic digestion, which should be treated, disposed of, or re-used in a proper way, avoiding any environmental impact (de la Fuente et al., 2013). Digested waste materials present some advantages for their use as soil amendments in comparison with untreated wastes, such as greater microbial stability and hygiene and a higher NH4 + -N amount (Holm-Nielsen et al., 2009;Alburquerque et al., 2012b;Möller and Müller, 2012). Therefore, digestate can be considered as organic amendment or organic fertiliser when properly handled and managed (Nkoa, 2014). In fact, the application of organic matter to agricultural soils stimulates microbial activity, increasing greenhouse gases emission (Bol et al., 2003;Fangueiro et al., 2010), thus requiring the application of appropriate agronomic techniques for greenhouse gases emission mitigation (Pezzolla et al., 2012).Several laboratory scale studies investigated the effect of so...

Greenhouse gas and ammonia emissions from soil: The effect of organic matter and fertilisation method

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The Chemical Composition of Biogas Digestates Determines Their Effect on Soil Microbial Activity

“…Most probably, the contribution of digestates to the storage of soil organic matter depends on the substrate inputs, which is also supported by modeling based on results from incubation experiments [18]. However, the number of investigations using field experiments is very limited and, again, these studies often focus on very brief periods after application and on a very small number of different digestates [19]. One aim of this work was, therefore, to investigate the effect of digestates on microbial activity up to 5 years after application under field and controlled conditions.…”

Effects of digestate solid fraction fertilisation on yield and soil carbon dioxide emission in a horticulture succession

“…Suboptimal performances of diges- tate involved inappropriate storage and/or application techniques that can lead to the loss of its fertiliser value or nitrogen use efficiency, through ammonia volatilisation, leaching and runoff into surface and ground waters (Nkoa, 2014). Several studies have investigated the effect of digestate fertilisation, especially on cereal and/or biomass production (Loria et al, 2007;Chantigny et al, 2008;Bachmann et al, 2014;Maucieri et al, 2016). Considering digestate effect on vegetables production literature data are also present, but several studies consider: i) one crop cycle (Hossain et al, 2014); ii) the cycles of the same species in different years (Montemurro et al, 2010;Lošák et al, 2016); iii) different cycles of one species in the same year (Nicoletto et al, 2014).…”