Dent corn yield and grain protein responses to integrated composted sewage sludge and liquid centrate fertilization...

Population growth and urbanization have increased wastewater generation, producing large volumes of sewage sludge requiring sustainable management. Anaerobic digestion and composting produce liquid centrate (LC) and composted sewage sludge (CSS), which can reduce dependence on synthetic fertilizers. However, their combined use as basal and topdressing nitrogen sources for dent corn has not been evaluated. This study assessed the potential of CSS as a basal fertilizer and LC as a topdressing to reduce reliance on chemical fertilizer (NPK) in dent corn cultivation. A field experiment included six treatments that applied NPK or CSS at 200 kg N ha^-1, either alone or supplemented with LC at 100 or 200 kg N ha^-1. By mid-season, LC at 200 kg N ha^-1 enhanced the SPAD value by 18.3% (NPK) and 23.5% (CSS), with these improvements persisting at 16.4% and 16.9% increases, respectively, by physiological maturity compared to NPK. The highest LC level enhanced grain protein by 11.0% (p = 0.009), shoot nitrogen uptake by 32.4% (p = 0.017), and stover yield by 19.6% (p = 0.011), irrespective of basal fertilizer. Compared with NPK alone, CSS plus the highest LC rate increased grain protein by 9.4%, nitrogen uptake by 35.3%, and stover yield by 24.7%. Grain yields (9.9-11.2 t ha^-1) and plant height were unaffected; however, CSS increased soil EC and lowered SOM, while LC reduced base cations. LC rate was the main driver of protein and biomass responses, highlighting that integrated strategy recycled wastewater-derived nutrients under the tested conditions.