Dairy cattle manure improves soil productivity in low residue rotation systems
Mineral fertilizer alone may not sustain soil productivity in cropping systems that return little crop residues to the soil, unless additional organic residues and/or manure is applied regularly to the soil. The objective of the present study was to assess the long-term effects of mineral fertilization (No fertilizer, PK, and NPK) and manure addition (0 and 20 Mg ha–1 yr–1) on soil physical and chemical properties and crop yields in a cereal rotation with removal of crop residues. After 28 yr, soil organic carbon (SOC) declined by –0.25 g C kg–1 yr–1 and total nitrogen (TN) by –0.025 g N kg–1 yr–1 with balanced mineral fertilization (NPK, no manure), comparable to the control (no manure, no fertilizer). In addition, mean weight diameter (MWD) of water-stable aggregates was lower with balanced mineral fertilization than in the control. In contrast, long-term application of manure significantly increased water-stable macroaggregates, potentially mineralizable nitrogen (PMN), and soil preseeding NO3–N levels. Corn yield and N uptake were increased by mineral fertilization compared to the control, and manure application increased corn yield by 89 and 87% and corn N uptake by 110 and 79% in 2005 and 2006, respectively. Increased corn yield in manured plots was attributed to the residual manure-derived nutrients and to improved soil properties. Mineral fertilizer alone could not sustain soil productivity in intensive low-residues cropping systems.