Long-Term Soil Ecosystem Studies

This paper describes a long-term, paired-catchment study, its broad findings, and considerations for future resource management of brigalow lands in north-eastern Australia. The Brigalow Catchment Study (BCS) commenced in 1965 with a pre-clearing calibration phase of 17 years to define the hydrology of 3 adjoining catchments (12–17 ha). After 2 catchments were cleared in 1982, 3 land uses (brigalow forest Acacia harpophylla, cropping, and grazed pasture) were monitored for water balance, resource condition and productivity, providing information for scientific understanding and resource management of the major land uses of the brigalow bioregion. In addition, this paper draws upon several project reviews to highlight the value of the BCS as an ‘outdoor laboratory’, its data resource, and to reflect on the study’s scientific rigor to support present and future value. An assessment of the BCS against national and international attributes of best practice for long-term studies showed the study to rate highly in aspects of design, implementation, monitoring, and data management, and moderately in formal publication, strategic management, and networking. The literature shows that Brigalow Catchment Study is the longest paired-catchment study in Australia, and continues to sample the interactions between climate, soils, water, land use, and management. Finally, this paper provides the context for component-specific papers on changes in hydrology, productivity, and salt balance. Results from the study to date include: a doubling of runoff after clearing, a reduction in wheat yield by more than 60% over 20 years, a halving of pasture availability 3 years after clearing, a decline in cattle liveweight gain of 4 kg/ha.year over an 8-year period with a constant conservative stocking rate, and the leaching of 60% of the root-zone (0–1.5 m) chloride after clearing for cropping. Unanticipated applications of the data from the study include: (i) a crucial set of soil samples for calibration of the RothC soil carbon model used to estimate Australia’s soil carbon emissions; and (ii) estimates of deep drainage as a basis for salinity risk assessment in the region

This paper reviews research performed at the Justus-Liebig-University of Giessen, Germany into the impact of different tillage systems on soil properties and quality. The impact of intensive soil tillage treatments on several soil properties was described by means of selected data obtained through long-term interdisciplinary research. The experiments were based on comparative application (long-term, up to 18 years investigations) of the respective tillage options on different soils (e.g. Eutric Cambisol, Eutric Fluvisol) ranging in texture from sand to a silt loam. These soils are located at five field sites with different crop rotations in the central German state of Hesse. Tillage intensity of the systems was considered to decrease in the following sequence: Conventional plough tillage (CT), reduced tillage (RT), and no-tillage (NT). For elucidating the impact of tillage intensity, the tillage extremes CT and NT were compared. Physical conditions of soil as influenced by the application of RT were considered to be intermediate between CT and NT. In general, bulk density in the upper layer of NT soils was increased, resulting in a decrease in the amount of coarse pores, and a lower saturated hydraulic conductivity when compared with the CT and RT soils. Surface cover by crop residues and higher aggregate stability under NT protected soil fertility by avoiding surface sealing and erosion. Lateral losses of herbicides were also reduced under NT conditions, whereas the susceptibility for preferential vertical transport of herbicides needs further evaluation. Accumulation of organic matter and nutrients near the soil surface under NT and RT were favorable consequences of not inverting the soil and by maintaining a mulch layer on the surface. Those improvements were associated with enhanced biological activities in NT and RT topsoils. Increased earthworm activity in NT treatments was associated with a system of continuous macropores which improved water infiltration rates. Earthworms support decomposition and incorporation of straw. Soils which have not been tilled for many years were more resistant to vehicle passage; consequently, the compaction by traffic was lower. Penetration resistance curves indicate that a uniformly stable structure had developed over the years in NT soils. Overall, the results show that RT and NT were beneficial to the investigated soil properties. If crop rotation, machinery, and plant protection are well adapted for the introduction of conservation tillage, these systems may replace conventional ploughing systems in many cases in German agriculture. (C) 1999 Elsevier Science B.V. All rights reserved.