Organomineral Fertilisers: Nutrient Dynamics and Evaluation of Agronomic Characteristics

Recycling of sewage sludge (biosolids) to agricultural land is regarded as the best practicable environmental option and currently represents the main disposal route in the UK. A novel method was developed by United Utilities-plc to produce organomineral fertilisers (OMFs) using biosolids. The purpose of this investigation was to identify the effects of the use of OMFs on winter wheat (Triticum aestivum L) and rye-grass (Lolium perenne L.) and validate the data reported in previous studies. Nitrogen and phosphorus release characteristics were also investigated under controlled laboratory conditions. Results indicated that grain yield (wheat) and dry matter production (rye-grass) were significantly increased (p<0.001) following application of OMFs and urea compared with the control (non-fertilised crop). Higher concentration of available N in the OMFs and urea resulted in significantly higher (p<0.001) grain yield and dry matter than the biosolid. Following fertiliser and biosolids application, the concentration of N in harvested plant material (rye-grass) was also significantly increased in the all treatments compared with the control (p<0.001). The MERNs (most economic rate of N) were calculated for wheat; these were 199.6; 189.7; and 223.5kg [N] ha -1 for urea, OMF 15, and OMF 10 respectively. Following application of OMFs and urea to the soil, the majority of the N (up to 80% of the total N applied) was found to be released in the first 30 days after application; thereafter, N-fertiliser was released at a rate comparable to the soil organic N. Total N in the soil was found to have significantly increased (p=0.002) compared with the control (non-fertilised soil) after two consecutives years of fertiliser application. This was more evident when the organic N content in the fertiliser material was increased in relation to the readily available N. Soil extractable P was not significantly (p=0.962) changed after two consecutive years of OMFs and biosolids application; however, a marginally larger increase in soil extractable P was observed when biosolids were used.