Dairy manure application effects on corn yield, nitrogen uptake, and plant‐available nitrogen with and without an interseeded cover crop

Abstract Manure is a critical corn nitrogen (N) source on farms; however, systematic manure N guidelines across growing environments are lacking. Impacts of preplant solid manure application on no‐till corn ( Zea mays ) yield, N uptake, and changes in soil plant‐available N (PAN) were compared to sidedress urea‐N application (90 kg N ha −1 ) with and without an interseeded cover crop ( Lolium multiflorum ). The study was performed at the Marshfield Agricultural Research Station in central Wisconsin from 2022 to 2024 on a somewhat poorly drained Withee soil ( fine‐loamy, mixed, superactive, frigid Aquic Glossudalfs ). Composted manure (CM) and fresh manure (FM) were surface applied preplant in the spring without incorporation at 81 ± 2 and 102 ± 27 kg total N ha −1 year −1 , respectively. Corn yield and N uptake were measured, and soil samples were taken in May and October to monitor PAN. Sidedress urea‐N application significantly increased corn yield across years compared to CM or FM. Partial factor productivity (N uptake/N applied) was also greater for sidedress urea in two of three seasons. Soil PAN concentration (0–10 cm) tended to be lower for CM and FM. The cover crop did not decrease yield or N uptake and had 1.7–4.9 times lower mean nitrate‐N leachate concentrations compared to no cover crop. Total carbon (C), nitrate‐N, ammonium‐N, PAN, and C:N sampled in spring were important contributors to yield and N uptake variance. Results stress the importance of sidedressing N to maintain corn yields and PAN on poorly drained no‐till fields.