Influence of Pasture and Rainfed Agriculture Land Uses on Soil Loss in Dojag-Chay Subwatershed (Ardabil Province- NW Iran)

Document Type: Research and Full Length Article

Authors

1 Scientific Member of the Center of Agriculture and Natural Resources of Ardabil, Ardabil

2 Scientific Members of the Center of Soil Conservation and Watershed Management, Tehran.

3 Scientific Member of the Center of Agriculture and Natural Resources of Ardabil

4 Scientific Members of the Center of Soil Conservation and Watershed Management, Tehran

Abstract

One of the main resonator factors in watershed soil erosion is inappropriate
land management including conversion of pasture land to dry-land farming.
Unfortunately, the changes of Gara Su watershed usages have been very common.
Thus, in order to understand the influence of land use on runoff rate and soil loss, soil
losses were investigated and determined under both pasture and dry-land agricultures
at sub-watershed of Dojag chay in southern west Qara Su Basin (within Ardebil
province). In this Research, using a drop maker rainfall simulator device, 18
treatments under the said watershed were conducted using an artificial rain with the
intensity of 6 mm/ min for 6 minutes and soil loss rate was measured due to the
rainfall in two user types in dry-land and rangeland under natural humidity conditions
and approximately the same as the raining season in three slope classes of 5 to 12, 12
to 20 and greater than 20. The results showed that with the cultivation, cultivated
soils get empty and their porosity and permeability increase so, with the increase of
water penetration ability, their runoff compared to the pasture lands starts with delay.
Comparing the amount of runoff shows that after runoff gets started in rain-fed
agriculture lands, the flowing speed and amount of water become more than those of
pasture lands and the statistical analysis also verified the significant relationship,
especially in slopes of more than 20% between the amount of soil loss and land use.
The soil loss under rain-fed agriculture was 8.8 times more than the pasture. As the
soil loss was compared for different slope classes of 5-12, 12-20, and more than 20
slope percent, the results indicated that the soil losses under rain-fed agriculture were
4.5, 5.6, and 12 times more than the pasture. The study results, therefore, can be
utilized for proper management of area through devoting necessary attention into
land uses.

Keywords