|Karlen, Douglas - Doug|
Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2009
Publication Date: 12/1/2009
Citation: Fernandez-Ugalde, O., Virto, I., Bescansa, P., Imaz, M.J., Enrique, A., Karlen, D.L. 2009. No-tillage Improvement of Soil Physical Quality in Calcareous, Degradation-prone, Semiarid Soils. Soil & Tillage Research. 106(1):29-35. Interpretive Summary: No-tillage agriculture can reduce soil erosion, conserve soil water, and increase crop yields, but producers around the world are often reluctant to adopt these new management practices. This study conducted in the Erba Valley of Spain showed that compaction (i.e., penetration resistance) of the formerly tilled surface layer increased after no-tillage practices were implemented, but other physical soil quality indicators were improved following seven years of no-tillage. No-tillage resulted in more small soil pores which increased the amount of water available to support crop growth. This doubled the yield of barley during the driest year. We conclude that no-tillage resulted in a better soil and that farmers should consider adopting these practices to compensate for the scarce and irregular rainfall that characterizes the region. This research is important for producers and researchers throughout the world who want to better understand how no-tillage affects different soils.
Technical Abstract: Many soils in the semiarid Mediterranean Ebro Valley of Spain are prone to physical and chemical degradation due to their silty texture, low organic matter contents, and presence of carbonates, gypsum, and other soluble salts. Rainfed agriculture on these soils is also hindered by the scarcity of water. No tillage can increase plant-available water and soil organic matter, and may help overcome most limiting factors in this area. Our objective was to determine how conventional- and no-tillage practices affected soil physical quality indicators and water availability in an on-farm study in the Ebro Valley. Soil samples were collected from three depth increments (0 to 5-, 5 to 15-, and 15 to 30-cm) at four locations within farmer-managed conventional- and no-tillage fields in 2007 and 2008. Both fields were managed for continuous barley (Hordeum vulgare L) production. The soil at both sites is a silt loam (Haplic Calcisol). Aggregate size distribution and stability, soil water retention characteristics, and soil organic carbon and total carbonates contents were determined for each site in 2007. Pore size distribution was estimated from the water retention curve. Penetration resistance, soil bulk density, and field water content during the entire crop growing season were measured for both fields in 2008. Penetration resistance was significantly greater to a depth of 15 cm under no tillage compared to conventional tillage, but differences were not detectable below that depth. Bulk density showed a similar but non-significant (P<0.05) trend. Aggregate mean weight diameter and stability in water were significantly greater under no-tillage than conventional-tillage practices due to reduced mechanical disturbance and increased soil organic carbon content. Field water content and soil water retention capacity were greater under no tillage than under conventional tillage. Total porosity showed that the no-tillage field had a higher percentage of 0.2 to 9 µm equivalent diameter pores, which helped to explain the differences in soil water content in 2008 when the growing season was very dry and barley production was twice as high with no tillage as with conventional tillage. We conclude that despite the greater penetration resistance under no tillage, the increase in water availability as a result of improved structure characteristics was more important for crop yield. This suggests that producers should seriously consider adopting no-tillage practices for soil conservation in similar semiarid degraded areas like the one studied in the Ebro Valley.