Short‐term soil health responses to organic and inorganic amendments in rainfed and irrigated sandy loam corn systems

Abstract

Improving soil health under variable water regimes remains a challenge in coarse‐textured soils. We evaluated short‐term soil health responses to fertilizer source (beef manure vs. inorganic N) with or without surface wood‐chip mulch during two contrasting growing seasons (2022–2023) in adjacent rainfed and irrigated no‐till sandy loam corn ( Zea mays L.) fields in Nebraska. Soil physical (bulk density and mean weight diameter) and chemical (pH, cation exchange capacity [CEC], NO ₃ ⁻ ‐N, K, P, Ca, Mg, Na, and SOM/SOC) indicators were measured postharvest, while biological indicators (β‐glucosidase, microbial respiration, and community‐level physiological profiles) were assessed at multiple within‐season sampling dates. By the second year, manure reduced bulk density by 10%–23% under both water regimes and consistently increased soil pH and concentrations of P, K, Ca, Mg, and Na. In contrast, inorganic fertilizer resulted in approximately 17% greater CEC and stimulated β‐glucosidase activity and microbial respiration at selected sampling times. Manure also increased microbial functional diversity at selected rainfed sampling dates. Wood‐chip mulch produced few consistent effects during the 2 years, and aggregate stability and SOC showed limited sustained responses. Overall, manure produced the broadest combination of short‐term physical and chemical responses, whereas inorganic fertilizer generated distinct chemical and transient biological responses. The contrasting response patterns indicate that short‐term soil health assessment in sandy loam systems should integrate responsive chemical and biological indicators with structural measurements rather than rely on a single indicator. Soil organic carbon and aggregate stability may be more informative for longer term assessment because measurable changes in these properties were limited during the study period.