Agricultural exploitation and physiographic location in the availability of nutrients to the soil of Diyala Governorate

The study area was chosen to include three physiographic sites on the Diyala River, as it is located in the village of Umm Al-Azam between longitudes 33.71785 east and latitudes 44.6185 north. There are four pedons in each A physiographic unit, two of which are in cultivated sites and the other two are in unexploited agricultural sites, so the total of the studied pedons is twelve. The results of laboratory analysis showed that the lowest content of available nitrogen for the cultivated sites was in the soils of river levees and the highest content in the soils of the river basins, while in the abandoned soil sites, it was the lowest content in the soils of the river basins and the highest content in the soils of depressions, and that the variance of the available nitrogen content in the soils of the cultivated pedons sites was moderate. The results indicated that the available phosphorous content in the sites of cultivated pedons soils ranged between 17.25 – 40.24 mg kg-1 as it was the lowest content in river levee and the highest in the depressions soils, while the available phosphorous content in the soils of the abandoned pedons sites ranged between 19.19 - 43.00 mg kg-1 as it was the lowest content in river basins and the highest content in depressions soils, while the variance of phosphorus in the cultivated soils pedons was of slight variation available. The available potassium content in the soils of the planted pedons sites ranged between 175.60 - 255.17 mg kg-1 , as it was the lowest content in the river levee and the highest in the soils of the river basins. The available potassium content in the soils of the abandoned pedons sites ranged between 170.64 - 257.45 mg kg-1 , where the lowest content of the available potassium was in the river levee soils, and the highest was in the depressions soils. Also, the variance of the available potassium in the pedons' soils was very little. As for the effect of the interaction between agricultural exploitation and physiographic sites and horizons in the characteristics of the study area, the results of the statistical analysis indicated that all study indicators represented by sites, type of use, horizons and their interactions did not have a significant effect of increasing nitrogen in the soil of the study area, as well as phosphorous and potassium. Keywords: N, P, K, nutrients, physiographic location, agricultural exploitation.