Maize yields from manure and mineral fertilizers in the 100‐year‐old Knorr–Holden Plot

Abstract

AbstractIt takes years, if not decades, before measurable changes in crop productivity and soil properties due to management practices can be detected. The objective of this experiment was to evaluate the effects of long‐term cattle manure and inorganic fertilizer applications on irrigated continuous maize grain yield, yield stability and reliability, nitrogen use efficiency (NUE), and soil properties. The experiment was conducted at the Knorr–Holden Plot in Scottsbluff, NE, from 1912–2012. Maize received no fertilizer in the first 30 yr of the experiment, and yields declined as nutrient supply from the native prairie was used. In 1942–1952, there were two cattle manure rates (0 and 27 kg ha–1 yr–1), and yield significantly increased in the manure treatment. In 1953, second replication and six inorganic N treatments were added effectively, making the study a randomized complete block with manure as the main and inorganic N as subplot factor with two replications. Linear regression of yield against years in manured plots had similar slopes across N rates. There was a gradual increase in slope with increasing N rates in non‐manured plots. Yield response to inorganic N rates in the non‐manured plot had a significantly greater slope but lower intercepts than the manured plot. Manure provided greater yield stability and reliability and significantly increased soil organic matter, nitrate‐N, and P accumulation in soil. Optimized manure and inorganic fertilizer N management are necessary to provide a stable and reliable yield and help establish an economically and environmentally sustainable maize production system.