USING CS-137 TO INVESTIGATE NET SOIL-EROSION AT 2 SOIL BENCHMARK SITES IN QUEBEC

Cs-137 in the soil was used to estimate soil erosion at two National Soil Conservation Program benchmark sites in the province of Quebec (sites 15-QU and 16-QU). The Cs-137 baseline in an uneroded forest area was approximately 3100 Bq m-2. The Cs-137 content at site 15-QU ranged from 1072 Bq m-2 to 6389 Bq m-2, while at site 16-QU it ranged from 663 Bq m-2 to 5444 Bq m-2. Computed net erosion over the past 30 yr at site 15-QU varied from a loss of 9.65 kg m-2 yr-1 to a gain of 10.88 kg m-2 yr-1 and at site 16-QU from a loss of 6.38 kg m-2 yr-1 to a gain of 1.73 kg m-2 yr-1. The average net erosion rates were 2.43 kg m-2 yr-1 at site 15-QU and 1.29 kg m-2 yr-1 at site 16-QU. Soil samples collected on a grid pattern indicated that 90% and 83% of the area at sites 15-QU and 16-QU, respectively, was subjected to net soil loss. A comparison of total Cs-137 movement from eroded areas to depositional areas showed that 24.2% of Cs-137 was lost from site 15-QU, while about 17.6% of Cs-137 was lost from site 16-QU. Mapping of Cs-137 content and calculated soil loss and deposition showed that soil erosion was closely related to topography. Under similar slope conditions, the soil erosion rates were 27-68% higher at site 15-QU than at site 16-QU. Higher tillage frequency and use of silage com were the suggested reasons for the higher soil erosion rates at site 15-QU compared with site 16-QU, which had been used for hay and small grains.