Assessing manure and inorganic nitrogen fertilization impacts on soil health, crop productivity, and crop quality in a continuous maize agroecosystem

(a) Soil organic carbon (C), (b) total soil nitrogen (N), (c) β-glucosidase (BG) enzyme activity, (d) potentially mineralizable N, (e) water-stable macroaggregate fraction, and (f) bulk density by soil depth and treatment (control = 0 kg N ha⁻¹, urea = 179 kg N ha⁻¹, and manure = target application rate of 179 kg N ha⁻¹). Error bars represent the standard error of the mean (n = 4). Values within soil depth marked with different letters are significantly different at α = 0.05.

(a) Soil nitrate nitrogen (NO₃-N), (b) Olsen phosphorus, and (c) diethylenetriaminepentaacetic (DTPA) potassium by soil depth and treatment (control = 0 kg N ha⁻¹, urea = 179 kg N ha⁻¹, and manure = target application rate of 179 kg N ha⁻¹). Error bars represent the standard error of the mean (n = 4). Values within soil depth marked with different letters are significantly different at α = 0.05.

(a) Soil diethylenetriaminepentaacetic (DTPA) extractable copper, (b) iron, (c) manganese, and (d) zinc by soil depth and treatment (control = 0 kg N ha⁻¹, urea = 179 kg N ha⁻¹, and manure = target application rate of 179 kg N ha⁻¹). Error bars represent the standard error of the mean (n = 4). Values within soil depth marked with different letters are significantly different at α = 0.05.

Physical, chemical, biological, nutrient, and overall soil quality indices in the surface (a) 0 to 7.5 cm and (b) 7.5 to 15 cm by treatment (control = 0 kg N ha⁻¹, urea = 179 kg N ha⁻¹, and manure = target application rate of 179 kg N ha⁻¹). The number of individual indicators used in each category is delineated in brackets. Error bars represent the standard error of the mean (n = 4). Values within soil depth and category marked with different letters are significantly different at α = 0.05.

Average stover, cob, and grain yields in response to inorganic nitrogen (N) (179 kg N ha⁻¹) and manure treatment (estimated available N of 179 kg N ha⁻¹), compared to a control treatment (0 kg N ha⁻¹). Data are the mean ±1 SE averaged over two growing seasons (n = 8). Different lowercase letters within a plant fraction indicate a significant treatment difference at α = 0.05.

Stover, cob, and grain macronutrient concentrations by plant compartment averaged over two study years (2017 to 2018) by treatment (control = 0 kg nitrogen [N] ha⁻¹, urea = 179 kg N ha⁻¹, and manure = target application rate of 179 kg N ha⁻¹). Error bars represent the standard error of the mean (n = 8). Values within plant compartment marked with different letters are significantly different at α = 0.05.

Stover, cob, and grain copper, iron, and manganese concentrations by plant compartment, averaged over two study years (2017 and 2018) by treatment (control = 0 kg nitrogen [N] ha⁻¹, urea = 179 kg N ha⁻¹, and manure = target application rate of 179 kg N ha⁻¹). Error bars represent the standard error of the mean (n = 8). Values within plant compartment marked with different letters are significantly different at α = 0.05.