Effect of different tillage methods on some soil physical properties

Conservation agriculture (CA) is considered as a suitable technique for protecting the environment, which will lead to major benefits and sustainable production. Minimum and zero tillage are recommended as they tend to reduce the cost of crop production, retain higher quantities of soil water, and provide physical protection for soil organic carbon (Bhattacharyya et al., 2012). CA improves soil physical parameters such as water-stable aggregates, water infiltration and retention as compared to conventional agriculture (Vinod et al., 2016). Conservation agriculture can improve soil physical properties and the associated processes, particularly, soil aeration, soil structure and soil porosity. It can also reduce soil erosion, soil compaction and crusting, and optimize the soil temperature for successful crop production (Indoria et al., 2017). Therefore, this study was conducted to evaluate the effects of conservation and conventional tillage on the soil properties and wheat yield.

This research was performed using geostatistical method through analyzing soil properties and wheat yield data. The soil properties measured included: soil texture, EC, pH, and soil infiltration. Soil infiltration were determined using double ring method. The infiltration models of Kostiakov and Philip were fitted to the measured data. Wheat yield was measured at 2 m2 interval of each sampling site. Data were analyzed using SPSS, Excel, and GS+ software. Average, variance, skewness, kurtosis and coefficient of variation (CV) of data for each property were calculated using descriptive statistics. Spatial distribution maps of properties were drawn using the best semi-variogran model and the best interpolation method.

The results showed that wheat yield with a medium CV varied from 1850 to 8150 kg/ha. The best semi-variogram model for wheat grain yield was spherical model, and the best interpolation method for it was point kriging. The wheat yield under minimum tillage system was higher than that of conventional tillage. Wheat yield and coefficients of infiltration models had a significantly correlation with soil properties. The best semi-varogram model for soil pH, EC, sand, silt, and clay percentage, and coefficient A of Philip model was spherical, and for the coefficients a and b of Kostiakove model, and I150 was exponential and for the S coefficient was Gaussian model. The spatial structure of soil pH, EC, sand, silt, and clay percentage, A coefficient, I150, and b coefficient was strong, and for the a and S coefficients were moderate. The best interpolator for soil pH, EC, sand, silt, and clay percentage, and a coefficient was kriging method and for silt percentage, b and A coefficient, and I150 was inverse distance weighting method. The magnitude of a and S coefficient was higher in comparison to the area of conventional tillage

Results showed that, the mean wheat yield at reduced tillage, no tillage and conventional tillage was respectively 6137, 4425, and 3589 kg/ha. Conservation tillage methods increased soil infiltration (6%) and decreased soil salinity (12%) relative to the conventional tillage. Conservation tillage slightly reduced soil pH as compared to the conventional tillage. Reduced tillage had a positive impact on parameters of soil infiltration models. There was a significant correlation between soil parameters, which is very important for better field management. Geostatistical models derived from the data of this research are very useful for the estimation of soil parameters in the similar areas. Based on the results of this study, it can be concluded that, although the studied soil parameters had wide spatial variability, geostatistical methods with the limited data can be used to estimate them with high accuracy. The coefficient a and the coefficient S were the highest in the area where conservation tillage was applied. These results indicate that conventional tillage has reduced the movement of water in soil by disturbing soil physical conditions, including the destruction of the soil structure. Finally, the best tillage system was reduced tillage. Acknowledgments: The authors would like to acknowledge the financial support extended by the Agriculture Organization of Fars province and Soil and Water Research Institute. Keywords: Geostatistic, Infiltration, Soil quality, Spatial variability.