Effects on soil nitrogen and plant production from land applying three types of biosolids to an agricultural field for three consecutive years

Land application of biosolids as a source of crop fertilizer and soil organic matter can be viewed as a sustainable approach to maintain soil productivity. Field-based experiments were conducted to examine the effects of three municipal biosolids (composted, liquid mesophilic anaerobically digested, and alkaline treated) on soil nitrogen dynamics and corn response, applied over three years in Nova Scotia, Canada. A total of fifteen treatments were evaluated in this study based on application management (surface vs. incorporation) of biosolids and the application of biosolids at a reduced rate with urea supplementation. Agronomic parameters were measured (corn yield and nitrogen uptake) and examined relative to the amendment rates to develop nutrient use efficiency indices. Our results indicate that soil pH was significantly increased by 1–1.5 pH units in alkaline treated biosolids (ATB) treatments under both application methods compared to liquid mesophilic anaerobically digested biosolids (LMAD), composted biosolids (COMP), urea, and an unamended soil control. The soil and plant responses were greatest for ATB>LMAD>COMP. Average soil mineral nitrogen (SMN) concentrations in surface applied biosolids ranged from 25.1 to 33.28 mg kg -1 in the three years of the study, but greater concentrations (33.27–39.39 mg kg -1 ) were observed when the biosolids were incorporated. The incorporation of biosolids also increased corn biomass yield by 18–33% and nitrogen uptake by 25–38% compared to the surface applied over three years. ● Three types of municipal biosolid were amended to soil with/without urea supplementation. ● Incorporated biosolids had higher corn yields than surface applied biosolids. ● Incorporated biosolids increased soil N supply and plant N uptake over surface applied biosolids. ● Alkaline treated biosolids raised soil pH by 1–1.5 units resulting in greater soil N mineralization. ● Soil and plant responses were greatest for ATB> LMAD> COMP.