تأثير تنش شوري بر پارامترهاي رشد و عملكرد نيشكر

Effect of salt stress on yield and growth parameter of sugarcane

Concerning agricultural productivity, land salinity is one of the major problems in Iran. In fact, a soil is called saline when it has an extract electrical conductivity testing index of higher than 2 ds/m. Sugarcane is ranked as a plant with a salinity threshold of 1.7 ds/m and with a varying sensitivity level ranging from moderate to sensitive. Sugarcane with suitable salts reduces the harmful side effects of salinity by making appropriate minerals. We should bear in mind that there is a significant negative relationship between land salinity increase and sugarcane growth and production. Studies done in Haft Tapeh region, ʹseven hillsʹ, show that sugarcane production rate fluctuates depending on the density of soil salinity. For instance, sugarcane growth is not affected in a soil with salinity up to 2ds/m, but the yield loss is greatly observed when the soil salinity grows upper than 4ds/m. Salinity tension has also adverse impacts on the growth of sugarcane. On the one hand, while it decreases the percentage of the reducing substances (RS), it increases the rate of molasses. Regarding the reduction of growth parameters and the corresponding effects of salinity and variety, sugarcane varieties show significant differences in their growth and outputs. In resistant cultivars, the value of K+ and the soluble sugar in them are considerably more, but the amount of their proline is less than those of the sensitive cultivars. Studies done in terms of age show that the ratoon fields are much more sensitive to salinity phenomenon as such the yield reduction indicates a linear relationship to EC increase and the intensity of such a relationship in the fields with the new culture is less than the ratoon. This field experiment was carried out in Amir Kabir Agro-industrial Company during 2002-2003 culture periods. The experimental cultivars CP69, CP48, CP57, and CP70 were of S. offtcinarum types. In dry climates, a great part of the water, required for plants irrigation to be supplied, has a large amount of insoluble salt. Salinity control has always been an important issue in irrigation management. To do this, an optimal irrigation management is required. It should be noted that high quality water is not always easily accessible; therefore, soil EC increase is something definitive particularly regarding the sugar high irrigation volume, about 30000m3/ha/y, and the special atmospheric conditions (high evaporation and perspiration rate) in Khuzestan province. Furthermore, the studies already done in the above-stated region show that the per ton straw in terms of unit increase in EC (ds/m) has resulted in 3.9 tons product failure (r= -0.863). On the other hand, the average percentage (10.88%) of sugar production has been associated with the mean EC of 3.59 ds/m. The effect of sugar reduction in the first quarter of the harvest season was equivalent to 0.613 RS per unit increase in salinity, while it was 0.231 RS in the second quarter. All in all, decreasing trend of 0.416 RS per unit increase in EC indicates the reduction of the quality of sugarcane syrup as well as the increase in soil salinity. From the above-stated studies, it can be inferred that the decreasing trend of syrup quality in proportion to its salinity has been more in the beginning of the harvest season, but this trend could be gradually slowed down if it is precisely managed. Depending on such factors as regional soil texture, drainage conditions, Aystaby level, quality of irrigation water and underground water salinity in terms of rate, cultivated varieties production differences pop up.