Response of soil structure and hydraulic conductivity to reduced tillage and animal manure in a temperate loamy soil.

We studied the combined effects of reduced tillage and animal manure on soil structure and hydraulic conductivity ( K) in the 2-10 and 12-20 cm layers in a loamy soil. The study was performed at the end of a 7-yr field trial and included three tillage treatments (mouldboard ploughing until 25 cm depth: MP, shallow tillage until 12 cm depth: ST, no-till: NT) and two fertilizer application treatments (mineral or poultry manure). Soil structure was assessed through bulk density ( ρ_b), micromorphological and macropore-space characteristics. K was measured in situ at −0.6, −0.2 and −0.05 kPa. Untilled layers had a vermicular microstructure resulting from earthworm activity, whereas tilled layers displayed a mixture of crumb and channel microstructures. Untilled layers had the highest ρ_b and twice as much lower total macroporosity area (pores > 240 μm in equivalent diameter) than tilled layers, reflected by the smallest area of macropores 310-2000 μm in diameter and the smallest area of large complex macropores. K under untilled layers was 12-62% lower than that under tilled layers, but differences were statistically significant only at −0.05 kPa in the 2-10 cm. No significant interaction between tillage and nutrient application treatments was detected for all properties. Compared with mineral fertilizer, poultry manure resulted in a similar ρ_b but 20% greater total macroporosity area and 30% higher K at −0.2 kPa. Overall, the sensitivity of soil structure and K to poultry manure were relatively small compared with tillage. We suggest that cultivation practices other than animal manure application are needed to improve physical properties under reduced tillage. [ABSTRACT FROM AUTHOR]