The effects of tillage displaced soil on soil properties and wheat biomass

Tillage operations transport large amounts of soil from convex slopes and deposit on concavities in hilly cultivated areas. Field experiment was conducted to assess tillage induced soil displacement and its effects on soil properties and wheat (Triticum aestivum L.) biomass production. The study was done on 3.5 ha fertilized and wheat seeded hillslope (14-21% slope) located 100 km north of Athens. Greece. Numbered aluminum cylinders (700), each 10 mm diameter by 10 mm height. were buried in soil as soil movement tracers (SMTs) to estimate soil displacement as a function of moldboard plowing with two depths in up-slope and down-slope directions. Furthermore. clay, organic matter, rock fragment content, phosphorus and Cs-137 were determined on 81 soil bulk cores to estimate soil redistribution rates along the study hillslope. Soil depth and soil water storage were measured in 81 soil sites and related to the wheat biomass production. The mean SMT displacement distance due to 25-cm plow depth on 21% slope was 42 cm for down-slope tillage and 16 cm for up-slope tillage. Comparable values were 31 cm for down-slope and 14 cm for up-slope tillage on 14% slope gradient. The SMT distance for both tillage directions on 21% slope was about 60% less for 18-cm plow depth compared with 25-cm plow depth. Shallow soil (depth <25 cm) was observed on convex slope with greater percentages of sand, rock fragments, organic matter and lower percentages of clay and available water. In contrast, deeper soil (depth >70 cm) was found on lower concavities where displaced soil was deposited. The spatial pattern of Cs-137 inventories suggests that tillage erosion is a major erosion process in the study area. The maximum leaf area index of wheat was 2.8 for convex slope and 3.6 for concave slope. Wheat biomass, ranging from 0.2 to 1.2 kg m(2), increased logarithmically with increased soil depth. Moldboard plowing displaced large amounts of soil from convex slope which changed soil properties to less favorable fur wheat production. Application of the obtained empirical functions showed that under the existing climatic conditions and management practices, the unprofitably productive area will increase from 4.1 to 6.8% in a period of 7 years. (C) 2001 Elsevier Science B.V. All rights reserved.