Application of composted sugarcane bagasse as a soil mulch aim to soil evaporation and salinization control

lack of water and soil salinization are two main threats to the sustainability of agriculture, especially in arid and semi-arid areas same as most parts of Iran. High evaporation in arid and semi-arid regions drive the down-to-up salt movement into the soil profiles and led the soil to salinization. Soil salinity reduces plant production through many ways like reducing water and nutrient uptake, ion toxicity, change in soil microbial activity, carbon and nitrogen ecological cycle disruption, etc. There are many ways to control the soil salinity and preserve soil water by application of mulch is one of them. Actually the use of mulch on soil in agriculture is mainly to limit evaporation, improve water use efficiency, and weed control. Many tupes of mulch are using to control the soil evaporation such as tephra, sand, plastic, wheat straw, geotextile, etc. Organic mulches have two main disadvantages, the ecological problem and, biological pollution for agricultural areas. More than one million tons of sugarcane bagasse produce in the Khuzestan province of Iran as the agricultural waste. And composting is a proper way to reduce the bad effects of raw organic material. This study examined a soil organic mulch, produced by composted sugarcane bagasse, in Jofeir area haloculture pilot in Khuzestan province.

Materials and Methods:

 This study, conducted in the southwest of Khuzestan province, Iran. The mean temperature during the experiment was 44 ± 2 ᵒC and the relative humidity was 65 ± 3%. The composted sugarcane mulch in 4 different thicknesses of 0.5, 1, 2 and, 0 (control) cm with 3 replicas applied on 2.5 liters of the local silt-clay-loam soil. The micro-lysimeters were 3 liters PVC pots which have heat-insulated and fill with the soil in 25 cm depth. In addition, The weight of the pots were measured at 10:00, 12:00, 14:00, 16:00, and 18:00 houres after the soil saturation. Before and after the experiment soil EC (1:2), bioavailable B concentration, saturation extracts Na concentration, and exchangeable sodium percentage (ESP) of the top 5 cm of the pots was examined. The experiment re-conducted in 5 continuous days and Identification of significant differences was performed using one-way ANOVA, in which p < 0.05 is considered significant in differences. Statistical analysis was performed with the Microsoft Excel 2010 and SPSS Version 16.

Results showed the significant difference between treatments with and without soil mulch in available water loss. The lowest water loss was belonging to the treatment with 2 cm (198.6 g of water/pot) of sugarcane composted mulch. The non-mulched soil had the highest evaporation amount (407.7 g of water/pot). water loss percentage showed the same trend and reduction with increasing in the sugarcane composted mulch thickness. Which with 2 cm of the mulch the moisture loss percentage calculated about 9.8 % and it near half of the value for the control (no-mulched soil) one. This mulch able to increase the available water for plant uses. Salts, B, and Na accumulation in surface soil appeared due to the evaporation process and mulch prevents it. As the results represented, with increasing the sugarcane composted mulch thickness, EC rising was slow. The EC increase in surface section of the non-mulched soil was high (20.5 dS/m) and the final EC were 41, 32, 25.5, 22 dS/m respectively in 0, 0.5, 1, and 2 cm of the mulch thickness treatments. This effect of sugarcane composted mulch could save the plant roots from salinity effects such as high Na, B and ESP. Also, it may play a positive role in water preservation in horticulture and green space. According to the composting process, this mulch has less ecological adverse effect than other organic raw materials. On the other hand, it able to release carbon and nutrients to enhance soil biological activity which would help plants to grow well.

Results showed increasing in the water losses and salinity accumulation in the soil surface of the treatments with decresing the mulch thickness. Also, the same trend was observed for bioavailable B concentration, saturation extract Na concentration, and ESP of the soil surface. Evaporation and, as the result salinization of the soil surface, decreased by the time but, the salt transport was very fast and the high considerable amount moved to the top