Phosphorus Losses to Surface Runoff Waters After Application of Digestate to a Soil Over Fertilised with Phosphorus

Abstract

Anaerobic digestates from biogas plants can be used as agricultural fertilisers providing recycling nitrogen (N) and other nutrients for crop needs. It is still unclear the impact on phosphorus (P) losses to runoff waters of digestates as sources of N instead of inorganic N fertilisers in over fertilised soils with P. A field experiment was done in a sandy and acidic soil high in P. The experimental design was completely randomised with five treatments. The inorganic N fertilisation (90 kg ha−1) was done in four treatments, those with past P inputs of the following: (i) inorganic N and P fertilisers (Ni/MF), (ii) organic amendments (pig or duck dry slurry-Ni/PS and Ni/DS or cattle manure compost-Ni/CM). Digestate was applied in plots with past P input of cattle slurry (DG/CS) providing also 90 kg N ha−1. Ryegrass was sowed as cover crop. The concentration of total dissolved P in runoff waters was high in all treatments and ranged between 0.5 (Ni/PS) and 2.6 mg L−1 (DG/CS). These runoff waters pose a risk of non-source P pollution for fresh waters. In soils with low P sorption capacity and over fertilised with P, the fertilisation with anaerobic digestate as the only source of N to crops increased the risk of P losses to runoff waters compared with inorganic N fertilisation. Therefore, the amount of digestate applied to soil must be calculated considering its N:P ratio in order to not exceed the crop P requirement.

Long-Term Organic Manure Substitution Increases Yield and Phosphorus Use Efficiency in a Double-Rice System by Altering Soil Phosphorus Uptake and Apparent Balance

“…Long-term field experiments could provide important data on the effects of various management strategies on the sustainability of farmlands under different fertilization regimes [23,24]. As a result of chemical P fertilization, for instance, crop P uptake is usually in the range of 10-25%, and the residual 90-75% is transformed to stable forms not easily accessible to plants [25], thereby leading to steady saturation of the soil P buildup and adsorption capability [26], reducing PUE [3,27] and increasing the danger of eutrophication [28]. This scenario makes long-term P management for optimum crop yield and environmental protection difficult, especially in acidic soils [28,29].…”

“…The cereal production capacity of China in 2017 increased by 462% relative to 1961 figures in an effort to feed approximately 22% of the global populace [33]. However, this progress could be retarded owing to the decline in PUE of the major cereal crops [3,21] and increased soil P accumulation [26] due to long-term excessive P fertilization [1,3]. Various fertilization methods alter soil P content [34] and regulate surplus P accumulation differently [35].…”

Phosphorus use efficiency, uptake and apparent balance response to substituting long-term chemical fertilizer with organic fertilizer in a double-rice cropping system

“…Yan et al (2020) stated that China's P use efficiency was below the global average, since the seasonal P use efficiency for major cereal crops in China was approximately 12% (Wang et al 2011;Shen et al 2013). The excess soil P may accumulate (Horta and Carneiro 2021) or leached to the nearby waters and causes eutrophication (Feng et al 2019). Previous results set that, application of chemical fertilizers in combination with organic manure can increase P use efficiency by changing soil pH (Ahmed et al 2019;Mitran and Mani 2017;Xin et al 2017).…”