Evaluation of Subsoiling Depth of Fields of Ratoon Cane on some Soil and Plant Indices

Heavy land preparation and leveling in sugarcane cultivation in Khuzestan damages soil structure. It makes the soil prone to compaction during harvesting. To reduce the effects of soil compaction and root improvement, rotation operations are common in ratoon field. Since subsoil (ratooning) plowing directly affects the development of sugarcane roots, therefore, this study was conducted to investigate the depth of ratooning operations of fields of ratoon cane on soil bulk density and its effect on plant root development and subsequent quantitative and qualitative yield of sugarcane. Ratooning operations were conducted at two depths of 30 and 50 cm and compared with no ratooning control. Quantitative yield including height, diameter, number of cane and shoot fresh weight per unit area were determined at the end of growth and before harvest. After harvest, cane root distribution was investigated in different depths. The results of analysis of variance showed that the ratooning depth operations were significantly affected cane height, stalk number per m-2, stalk weight, millable cane yield, sugar yield, and soil bulk density. But the cane stalk diameter, syrup brix, recoverable sugar, and soil bulk density at a depth of 30 (BD30) cm were not affected by the depth of ratooning. R-50 treatment increased cane height (28.2%), stem number (5.7%), stalk weight (42%), millable cane yield (55%) and sugar (53%) compared to control, and reduced soil bulk density in depth of 50 cm (3.6%). However, R-30 treatment resulted in increased soil bulk density (3.6%) and reduced yield of sugarcane (12.8%) compared to control. Also, root weight was higher in R-50 treatment compared to control and especially R-30. In addition, more than 50% of root distribution was observed in R-30 treatment in the first 10 cm layer of soil. In general, the results of this study showed that reducing the depth of ratooning to 30 cm, not only did not have a positive effect on the above factors, but also increased the soil bulk density, more root extending near the soil surface and eventually, reduced sugarcane yield. In other words, limiting root development to soil depth causes more root density on the soil surface and thus leads to the absorption of nutrients in a more limited volume of soil, which ultimately reduces plant growth and sugarcane yield.