Sub-soiling system was conducted in order to alleviate the disadvantage which developed by soil compaction. A comparison made between field treatments which tilled by chisel plough at 20 cm depth and the technique of sub-soiler plough with differences in the sub-soiling depths (25, 50, and 75 cm) and the lateral spaces between sub-soiling ruts (200, 400, and 800 cm). Each techniques of the sub-soiling depth were replicated with all of the different distance of lateral spaces between sub-soiling ruts. The aim of the comparison was to indentify the most effective sub-soiling technique which produce more enhancement of soil physical properties, achieve the best distribution of soil moisture content and achieve the highest rate of soil water flux.
Results indicated that, the plot of soil which was tilled at 75 cm with a lateral space of 200 cm, recorded the lowest moisture content values and exhibited the highest values of soil penetration resistance. It exhibited more enhancement of soil physical properties as the action of the excess loosening occurred from the deep tilling with the narrower lateral space lead to increases soil porosity, improve permeability, decrease soil strength to low values in comparison with their values before sub-soiling. The soil plot which tilled at 50 cm with a lateral space of 200 cm were also achieved more enhancements. Those plots were also recorded high correlation coefficient consideration to the three irrigations. It was found 95.16 and 94.97 % at the first irrigation, 95.54 and 95.47 % at the second irrigation and 95.45 and 95.28% at the third irrigation for the plots of 75 and 50 cm, sub-soiler depth and 200 cm, lateral space respectively. Values of soil bulk density which obtained after the three irrigations for all the sub-soiling plots decreased from the values obtained before sub-soiling. And the lowest values were found at the top surface layer, this was due to tilling with chisel plough at 20 cm depth where, a more pulverization occurred in the top layer. The higher rate of soil water flux was exhibited from the plots which were tilled at 75 and 50 cm, with a lateral space of 200 cm, followed by the plots which were tilled at 75 and 50 cm, with a lateral space of 400 cm. and high correlation coefficient of 98.62 % was obtained from statistical analysis made using the drainage equations. From the obtained results, it can be concluded that, the lateral space between sub-soiling ruts decreases with an increase in the tillage depth, the soil achieve more enhancement of soil physical properties and exhibit higher rate of soil water flux.