Effective application of mass balance method: case of organic fertiliser produced from pig slurry

Received: January 26th, 2021 ; Accepted: May 8th, 2021 ; Published: May 11th, 2021 ; Correspondence: shalavinaev@mail.ruThe study aimed to verify the applicability of the mass balance method in calculating quantity and quality of an organic fertiliser produced from unseparated pig slurry in a pigfattening complex in the Leningrad Region. The amount of manure at ex-animal level and its nutrient content, required for further calculations of ex-housing manure and resulting organic fertiliser at ex-storage, were calculated by applied diets and feed DM digestibility. Calculated values were compared with the norms from relevant Russian regulatory documents. The regulatory values of manure nitrogen were 22% smaller than the calculated ones. On the contrary, the standard values of manure phosphorus and potassium exceeded the calculated ones by 72% and 73%, respectively. The nutrient content of the organic fertiliser was calculated by the farm data on pig housing and slurry processing systems. The values calculated by the mass balance method were compared with those from the analysis reports issued by the certified laboratory. The difference did not exceed 20%: 11.2% for N, 13.3% for P, and 18.7% for K. This way, the mass balance method can be effectively used for calculating the characteristics of pig slurry-based organic fertiliser. On the contrary, the data from the current regulatory manure management documents showed the low reliability in the part of the physicochemical properties of fattening pig manure. These documents do not take into account the changes in the fattening pig diets with modern special concentrated feeds, which have a major effect on the manure nutrient content