Zeolite Enhances the Beneficial Effects of Sewage Sludge on Barley Yield, Increases Nitrogen Use, and Improves Soil Properties

Abstract Biosolids and zeolite have been extensively used in agriculture; however, their interactive effects need to be further clarified under field conditions. The effects of sewage sludge (SS) and zeolite on barley grain yield, nitrogen use efficiency (NUE) and soil properties were investigated in a 2-yr field study. Treatments included four rates of SS (7.8, 15.6, 23.4, 31.2 Mg ha − 1 ) and one rate of inorganic fertilizer (IF; 120 kg N ha − 1 + 26.16 kg Ρ ha − 1 ) both applied alone and in combination with zeolite, an unamended control, and a zeolite control. The applied soil amendments stimulated crop growth and N uptake. Sewage sludge, even at the lowest rate, resulted in grain yield similar to that of the IF (1669 kg ha − 1 ). Zeolite reduced SS requirements to produce grain yield at the IF level by 40% and increased maximum grain yield of barley by 23% compared to SS alone. Zeolite increased NUE when combined with low rates of SS, primarily by enhancing N uptake efficiency compared with IF, and mitigated the adverse effect of high SS application rates on soil NO 3 – -N and electrical conductivity. Adding SS at rates up to 15.6 Mg ha − 1 in combination with zeolite improved soil organic C only in the first year. Soil DTPA-extracted Cu, Mn, and Fe levels in SS treatments were lower than those detected in the IF, except for the 15.6 Mg SS ha − 1 rate that resulted in a significant increase in Fe. Zeolite inhibited the increase in DTPA-extractable Zn induced by high SS rates. Overall, zeolite enhanced the beneficial effects of SS while mitigated its negative consequences, offering both agronomic and environmental benefits.