Municipal Sewage Sludge Effects on Maize Yield, Nitrogen Use Efficiency, and Soil Properties

Abstract

Biosolids are frequently used as organic soil additives. This 2-year field study investigated the effects of sewage sludge (SWS) application on maize (Zea mays L.) production, nitrogen accumulation, redistribution, and nitrogen use efficiency, as well as on grain element concentrations and soil properties. Treatments included three SWS rates (20, 40, and 80 Mg ha−1 year‒1), mineral fertilizer (300 kg N ha−1 year‒1 and 26 kg P ha−1 year‒1), and an unamended control. Plant samples were collected at silking and maturity in both years, while soil samples were taken following maize harvest in the second year. Maize grain yield increased by 143 kg ha−1 for every Mg increase in SWS rate. Sewage sludge application resulted in maize grain yield comparable to or even greater than that of mineral fertilizer. Nitrogen uptake and translocation to grains increased quadratically with increasing SWS rates. Nitrogen use efficiency increased with moderate SWS application (up to 40 Mg ha−1) but decreased with heavy application (80 Mg ha−1) compared to fertilizer, raising the risk of nitrogen losses. Compared to fertilizer, SWS resulted in similar or lower P and Cu concentration in the grain, as well as similar or higher K, but had no effect on N, Zn, Fe, and Mn concentration. Soil pH, NO3-N, and exchangeable K were similar in SWS and fertilizer, but soil Olsen P improved with SWS. There were no differences among treatments in DTPA-extractable Zn, Fe, and Cu, while Mn raised with SWS. Sewage sludge could be used to increase plant N reservoir at silking, N translocation to grains, and post-silking N uptake, allowing plants to meet their N requirements throughout the growing season. Even at 20 Mg ha−1, sewage sludge can successfully replace mineral fertilizer in maize crop.