A trial was conducted in a private field at Al-Hartha township, Al-Basrah Governorate, Iraq on autumn season 2012 to investigate the effect of using combined subsoiler with a moldboard plow to make furrows of different depths and spacings immediately after harvest of barley crop for winter season without tillage of the whole field. The study included also plow performance in treating hard subsoil layer and improvement of some physical properties of soil (apparent density, total porosity and soil penetration resistance) and effect on the yield of corn crop var. Bohoth (Researches) 106. The plow used to make furrows represented by combinations of sex double treatments for subsoiler and moldboard plows (S30 M20 , S40 M20 , S40 M30 , S50 M20 , S50 M30 and S50 M40) where S denotes subsoiler and M moldboard plows, while the ancillary number denotes the depth of tine for both plows. Two spacings, i.e. 75 and 100 cm were used between furrows. Control treatment consisted of tillage with moldboard plow at depth of 25 cm using furrow opener to open furrows at 25 cm depth.
The field soil was silty clay containing a hard pan of 10 cm thickness at 30-40 cm depth. Randomized complete block design (RCBD)was used with three replicates. Differences between means wre tested by RLSD at p = 0.05.
The results indicated the significant superiority of furrow depth treatments using combined subsoiler plow comparing with control treatment in all studied properties. The increase in furrow depth within study ranges resulted in reducing apparent density and soil penetration resistance with increase in soil total porosity, which reflected positively in increased row and seed numbers in corn ear. Plant seed yield improved also, which contributed in significant increases in corn seeds (Mg. h-1). Distances between furrows did not show a significant effect on the studied properties. The treatment S50 M40 of interaction between furrow depth and 75 cm distance between furrows gave the best results and achieved the highest seed yield of 4.928 Mg. h-1.