Long‐Term Effects of Mineral Nitrogen Fertilizer on Irrigated Maize and Soil Properties

Abstract

Core Ideas Grain yield, biomass, N uptake, SPAD units, soil N levels and N efficiciencies were affected by the N application rate. Maximum grain yields required 203 kg N ha −1 of available N in the 0‐ to 30‐cm layer soil. Sampling to a depth of 0 to 30 cm provided similar correlations than sampling to 0 to 60 and 0 to 90 cm. Mineral N fertilization increased soil organic C stock. Nitrogen is a key determinant of growth and grain yield (GY) in maize ( Zea mays L.) and is therefore economically and environmentally important. We investigated the performance of maize crops in a 12‐yr experiment (2002–2007, 2010–2015) under sprinkler irrigation in a petrocalcic calcixerept soil in northeastern Spain, with controlled mineral N application rates (0, 100, 150, 200, 250, 300, and 400 kg N ha −1 yr −1 ). The application rate affected maize GY, biomass, N uptake, SPAD units, soil N levels, N efficiencies, and soil organic carbon (SOC). Average maximum GY's (∼15 Mg ha −1 ) required 203 kg N ha −1 of available N (defined as initial soil NO 3 − plus N fertilizer) in the 0‐ to 30‐cm horizon, confirming the importance of the soil N content. Nitrate levels in the 0‐ to 30‐cm horizon for maximum yields achieved a R 2 value in the plateau fitting model similar to the 0‐ to 60‐ and 0‐ to 90‐cm horizons. The GY's increased at a rate of 192 kg ha −1 yr −1 , suggesting a combination of genetic improvement in the hybrids and also an improvement in agronomic management. The 200 kg N ha −1 fertilizer treatment achieved almost the highest GY's (∼14 Mg ha −1 ) with simultaneous high nitrogen use efficiency (NUE) (0.83 kg kg −1 ). Mineral N fertilization also increased the stock of SOC in the 0‐ to 30‐cm horizon.