Evaluation of chemical fertilizer and farm cost savings through the use of filtered liquid fertilizer

This case study evaluated the agronomic applicability and economic benefits of using filtered liquid fertilizer (FLF) derived from livestock manure for spinach (Spinacia oleracea L.) greenhouse cultivation in Pocheon, Korea.The FLF was produced via a membrane filtration process and showed a reduced suspended solids content (SS, 684 mg/L), indicating suitability for fertigation systems.Chemical analysis revealed that the FLF contained high levels of total nitrogen (2,242.32mg/L) and potassium (K 2 O, 2,640.62 mg/L), whereas phosphorus (P 2 O, 151.80 mg/L) was markedly lower than other major nutrients.Soil diagnosis of the study sites showed excessive accumulation of available phosphate (Av.P 2 O 5 , 1,028 mg/kg), far exceeding the recommended range, while nitrate-nitrogen was below the optimal range.Therefore, an FLF application strategy based on crop nitrogen requirements was considered optimal to supply nitrogen and potassium without aggravating phosphorus accumulation.Substituting chemical fertilizers with FLF resulted in a fertilizer cost saving of 47,193 KRW per 10a.Although the FLF exhibited high electrical conductivity (EC, 23.41 dS/m), the findings suggest that FLF can serve as an effective alternative to chemical fertilizers in intensive greenhouse systems, particularly for managing nutrient imbalance in phosphorusaccumulated soils while providing tangible economic benefits to farmers.