Evaluation of Soil Health in the Unstable Ecosystem of Gorgan City

Improving soil quality and stability leads to continued soil fertility, maintaining environmental quality and increasing plant and human health. Land use change is one of the main drivers of changing soil quality by changing the structure and performance of ecologists. Increased population and double pressure on the ecosystem to provide food resources, has led to widespread changes in the use of natural land in the northern forests of the country to agricultural land. Therefore, this study was conducted to assess the effect of land use change on the health and soil quality of sloping lands south of Gorgan.

In this study, two hills, one with forest use and the other with marginal agricultural land, which has more than 50 yr of cultivation history, were selected. Sampling was performed in July 2020 due to severe land degradation from only two positions of shoulder and back slope and completely randomly from a depth of 0-20 cm of forest soil and adjacent cultivated land and then samples were analyzed. Properties evaluated include soil organic carbon content (OC), percentage of soil texture components and bulk density of soil, percentage of lime equivalent soil, EC, pH, the amounts of high consumption elements (NPK) and CEC were as indicators of soil quality.

The research showed the highest coefficient of variation as a result of land use change was related to the two parameters of OC. Based on the correlation matrix, the physical parameters of saturated mud percentage, total porosity percentage with the percentage of organic carbon and soil clay at the level of one percent (P <0.001) show a positive and significant relationship. Among the chemical variables, as expected, there was a significant positive correlation between cation exchange capacity, percentage of total nitrogen and potassium levels available with organic matter and percentage of clay at the level of 1%. Analysis of variance and mean comparison showed land use change from virgin forest to agriculture has significantly reduced soil quality in all parameters evaluated except absorbable phosphorus. The reason for this can be considered improper cultivation operations in arable lands, which causes the breakdown of aggregates and exposes the organic matter trapped in the aggregates to microbial decomposition. As a result, the surface horizon of the soil loses its original structure and is easily affected by erosion and physiographic processes of the hill.

the study of OC as the most important indicator of soil quality showed that this parameter with an average of 6.07% in forest use and an average of 0.59% in agricultural use with a 90% decrease as a result of land use change. High reduction of organic carbon and soil clay as the most important indicators for assessing soil quality in arable lands, indicates unstable use and highly unstable ecologists in the sloping lands of south of Gorgan. It is suggested that in future studies, the effect of land use change on erodibility and land production should be studied and evaluated, considering that the continuation of cultivation in this area causes an increasing decrease in soil quality.