Trend of total nitrogen, phosphorous and potassium variability in floodwater spreading stations

Importance of flood spreading related to soil resources is due to sedimentation of suspended materials in eroded lands. These lands are converted to fertile lands with high capability for developed agriculture. Entrance of flood with variable resources produces variability in soil properties. Therefore، trend of changes in total nitrogen (N)، phosphorous (P) and potassium (K) were investigated in this research. For those purposes، the experimental stations were selected، based on soil properties، watershed characteristics and conditions of flood spreading sites. After selection of bands، sampling was done by the systematic-randomized method. Non-parametric test (Kruskal & Wallis) was used for statistical analysis because of data non-uniformity of (based on Kolmogorov-Simernov test). Variability of total N in stations of group I and group II increased in the final year in comparison with that of the first year. So، total N from the first to the third bands ranged from 0. 03، 0. 03 and 0. 02 percentage in the first year to 0. 04، 0. 03 and 0. 03 percentage، respectively in the final year. Also، P variability in stations of group I and group II increased from the first year to the final year. So، available P in the three bands ranged from 3. 1، 5. 03 and 3. 99 mg/kg in the first year to 7. 93، 9. 09 and 5. 89 mg/kg in the final year. In the stations of group II، available P in the three depths ranged from 7. 35، 5. 17 and 2. 01 mg/kg in the first year to 9. 25، 6. 85 and 6. 14 mg/kg in the final year. In the stations of group III، available P in the three depths ranged from 4. 23، 3. 1 and 4. 74 mg/kg in the first year to 9. 34، 6. 95 and 6. 72 mg/kg in the final year. In group I، available K decreased from the first year to the final year. So، available K from the first to the third bands ranged from 127، 133 and 128mg/kg in the first year to 111، 118 and 113 mg/kg in the final year. Despite the low quality of soil fertility prior to the construction of these stations، in general، floodwater spreading has considerably improved soil fertility. However، desirable objectives may be achieved in long term through occurrence of diverse flood events and suitable maintenance of the stations.