Tillage Effects on Soil Compactness and Wheat Root Morphology

Tillage systems influence soil physical, chemical and biological characteristics which in turn may alter, root characteristics, growth, and development. A three year study was conducted to investigate the effects of seven tillage systems on some soil (fine-loamy mixed, Typic Haplocambids) physical characteristics and wheat (Triticum aestivum L.) root morphology. Tillage treatments included moldboard plowing + disking (MD) as conventional tillage, chisel plowing + disk (CD), chisel plowing + rotary tilling (CR), chisel plowing (twice) + disking (2CD), plowing with a khishchi (a regional rigid cultivator) (KD), as non-inversion methods, and till planting with cultivator combined drill (TP), and no-tillage (NT) as direct drilling methods. Soil texture, bulk density (BD), organic matter (OM) and compactness (CI) were determined. At the depths 0-0.1, 0.1-0.2, 0.2-0.3 and 0.3- 0.4m, root mass density (RMD) was obtained, root length density (RLD) was determined and average root diameter (RD), surface area density (RSD), and root fineness (RF) were calculated. A randomized complete block design consisting of four blocks (replications) was used. For all treatments, the upper layer (0-0.lm) contained a higher quantity of RMD, RLD and RSD, but the reverse was observed for the lower layer (0.3-0.4m). The upper layer (0-0. lm) contained almost 46% of the total RMD (average of all treatments), while the second (0.1-0.2m) the third (0.2-0.3m) and fourth (0.3-0.4m) depths contained 23, 18.5 and 12.5% of the total RMD, respectively. The average RLD of four depths for MD, CD, CR and 2CD were significantly (P ≤ 10)higher than KD, TP and NT systems (24.9, 25.1, 24.2, and 23.8, as compared with 22.3,21.8 and 21.6km m-3 , respectively). Results of this study showed that, for the arid soils of central Iran, with weak structure and low organic matter content, as the number of tillage operations increased, root morphological characteristics improved.