Temporal variations of soil moisture in relation to precipitation and temperature under fallow and planted conditions in rainfed land

Soil moisture (SM) is the major factor controlling plant growth particularly in rainfed lands. It varies due to the change of climatic parameters such as precipitation and air temperature and evaporation. This study was conducted to found climatic factor influencing soil moisture under rainfed conditions. A field experiment with two cultivated conditions: under fallow and cultivated with winter wheat was designed in a rainfed land with 10% slope steepness in the University of Zanjan during growth period from 2016 to 2017. Toward this, six plant plots with 2m × 5m dimensions were installed along the slope orientation similar to conventional tillage method in the area. Volumetric soil moisture was measured in 7-day interval using TDR model IDRG SMS-T2 set during growth period Climatic variables including air temperature (AT) and precipitation (P) along with soil temperature (ST) were determined during growth period. Based on the results, SM in cultivated plots was about 11% less than the follow plots, and this difference was statistically significant between the two. Amount of soil moisture significantly varied among different months (p<0.001). Significant correlations were found between SM and P, AT and ST in the two cultivation conditions (p<0.05). Higher dependency of SM on AT (r=0.44) and ST (r=0.51) was observed in fallow plots as compared to planted plots. This study revealed that ST is the most effective property controlling SM in fallow and planted lands in the area.