Temporal Variability of Some Soil Fertility indicators in the Agricultural Lands of East Azerbaijan Province

The characteristics of soil exhibit variability across different locations, and it is of utmost significance to aptly identify these variations and effectively incorporate them into the strategic planning and efficient management of agricultural lands. This study was conducted with the objective of monitoring the fertility of soil in the agricultural lands of East Azerbaijan province over a period of 15 years by examining the spatial and temporal variations of organic carbon, available phosphorus, and potassium.

It was an applied study carried out in 2023 in East Azerbaijan province. The methodology involved the preparation of spatial variation maps for soil organic carbon, available phosphorus, and potassium using the Inverse Distance Weighting (IDW) approach. These maps were created based on the analysis of 9000 soil samples collected between 2002 and 2006 from all counties within the province. The preparation of these maps occurred from 2020 to 2022, using data from 1400 databases, and the homogeneous areas of the studied properties were classified according to the standards set by the Soil and Water Research Institute.

The findings demonstrated a notable reduction in the expanse of lands containing organic carbon levels below one percent; Consequently, by 2022, the territory of these lands had diminished to less than half of its previous size. Conversely, the area encompassing land with organic carbon levels surpassing 1% exhibited a marked increase, reaching over 660000 ha. Over the course of these years, there was a substantial decline in the quantity of available phosphorus, resulting in a decrease to less than 10 mg/kg across an expanse exceeding 1260000 ha. Conversely, the amount of potassium exhibited minimal alteration throughout this period.

Notably, the area of land exhibiting an organic carbon content below the critical threshold has experienced a significant reduction, amounting to less than half. Conversely, the area of land with organic carbon surpassing the critical threshold has expanded. Furthermore, the quantity of absorbable phosphorus has exhibited a noteworthy decrease during this time period, resulting in over 85% of agricultural lands currently suffering from a deficiency in phosphorus. In contrast to these aforementioned elements, the quantity of soil-absorbable potassium has remained relatively stable throughout this period.