Soil Health Under Nitrogen- Vs Phosphorus-Based Manure and Compost Management of Corn.

In recent years manure and compost management is shifting from nitrogen (N)-based to phosphorus (P)-basis application due to environmental concerns from P and potassium (K) surplus that impacts water quality and forage quality, respectively. The objective of this study was to evaluate the impact of a change from N-based applications without incorporation to a P- based (crop-removal) management system with immediate incorporation of manure on (i) soil pH, organic matter (OM), P, K, and nitrate accumulation at different depths, and (ii) soil carbon dioxide respiration in the top 20 cm of soil. A 5-yr field study was conducted with annual spring applications of two rates of composted dairy manure (45 and 77 Mg ha^-1), two rates of liquid dairy manure (63.5 and 180 kL ha^-1), and two inorganic N fertilizer rates (0 and 112 kg ha^-1). Soil respiration was determined using the Solvita® test. After five growing seasons, the lowest soil pH was observed where 112 kg ha^-1 inorganic N was added. Soil pH increased with depth, reflecting calcareous soil parent material. Soil organic matter was higher in compost treatments than the manure and inorganic treatments and decreased from upper (0-5 cm) to deeper soil layers (40-50 cm) in all treatments. Soil nitrate levels were higher in N-based manure and compost treatments than those of P-based and inorganic treatments. Soil P and K levels were higher in surface layers (0-5 and 5-20 cm) than deeper layers and showed the highest accumulations of P and K with N-based compost and manure additions. In 2005, OM and soil carbon dioxide respiration were linearly related (r²= 0.92; p<0.04). These results show that compost application can improve soil health over time. However, rates should be limited to reduce P and K buildup in the soil.