Investigation of effects of different canopy cover of olive on some soil properties under an agroforestry system (Case study: Aq Qala, Golestan province

Trees play an important role in all terrestrial ecosystems. Trees can have a main impact by their root system and canopies on conservation, fertility and improve quality of soil. Studies conducted in context of the effect of trees on soil properties indicate that presence of trees have been an important role in improving soil properties under their canopy. Considering the importance and role of trees on the surrounding soil properties, trees management is essential in Programs principles of soil conservation and fertility. One thing that should be considered in this context is the canopy of trees. Therefore, in this study has been paid to investigate of effect of olive trees canopies in an agroforestry system on soil organic matter and nutrient.
For this study was considered the land under agroforestry system (wheat cultivation in between olive trees) and land under wheat cultivation (control area). In agroforestry system, was considered three treatments of canopy cover: canopy cover with small area, canopy cover with moderate area and large canopy cover. Organic matter was used titration method and soil nitrogen was calculated by using correlation between nitrogen and organic matter. Soil soluble phosphor was determined by Olsen method and spectrophotometer. Measurement of potassium was determined by using ammonium acetate method and flame photometry. Mean weight diameter was measured by wet sieving. To analyze the data from laboratory results were used by SPSS and Excel and for comparison of means were used by test least significant difference (LSD).
The results show that different treatments of canopy cover have a significant effect on organic matter, phosphorous and mean weight diameter at 1% and 5% level of significance. Significant correlations have not been observed between different treatments of canopy cover and soil potassium. As a result of the implementation of agroforestry system, increased amount of organic matter from %0.22 to %1.49, nitrogen from %0.01 to %0.074, phosphorus from 0.79 to 1.22 mg/L, potassium from 4.94 to 6.95 mg/L and mean weight diameter from 0.04 to 0.15 mm.
The presence of litter fall and wheat debris under trees increased soil organic matter and nutrient and improve soil properties. Agroforestry system can be as an approach to increase of soil fertility and help to prevent of soil erosion especially in arid zone because of combination of several different systems (trees, crops and pasture). Today, due to increase of population has followed increasing demand for food. This led to increased utilization of agricultural land and loss of soil fertility. Agroforestry system as a sustainable agricultural can increase soil fertility in long term.