Abstract
Sugarcane filter cake is a by-product of the sugarcane industry and its accumulation without use may increase the risk of environmental pollution. Filter cake valorization to be used as a soil amendment is of special interest due to its high content of nutrients and organic matter. However, little is known about its effect on soil health and productivity of mango (Mangifera indica L.) plants. Laboratory and 2-year field studies were conducted to investigate the effect of fresh (FC) and composted filter cake (CFC) in combination with plant growth stimulating bacteria (PGSB) on soil quality and fruit yield of mango. The field experiment contained two factors: the first one was the inoculation with plant growth stimulating bacteria [with (PGSB +) or without inoculation (PGSB -)]. The second factor consisted of five treatments: C = control, FC1 = fresh filter cake at 5 t ha(-1), FC2 = fresh filter cake at 10 t ha(-1), CFC1 = composted filter cake at 5 t ha(-1), and CFC2 = composted filter cake at 10 t ha(-1). The addition of FC1, FC2, CFC1, and CFC2 with PGSB + inoculation increased the soil organic-C by 16, 26, 16, and 28%, respectively, compared to C. PGSB significantly increased the nutrient availability and uptake and enhanced the activity of dehydrogenase and phosphatase (acid and alkaline) enzymes in the studied sandy soil. PGSB enhanced the soil health and caused a 10% increase in the fruit yield of mango plants compared to the non-inoculated treatments. PGSB and CFC2 significantly increased the chlorophyll, leaf area, number of leaves, and shoot length by 27, 57, 20, 23, and 40% compared to C. CFC2 increased the fruit yield by 40 and 39%, respectively, in the first and second seasons compared to FC2. PGSB and CFC2 significantly improved the total soluble solids, total sugar, vitamin C, and pulp in the fruit of mango compared to C. The addition of fresh filter mud cake significantly reduced the soil health and fruit yield of mango compared to the composted form. The addition of composted form resulted in higher levels of nutrient availability and enhanced the activity of dehydrogenase and phosphatase enzymes compared to the fresh form. Although the addition of fresh filter cake directly to the soil was less efficient in improving the soil quality and mango yield compared to the composted form, this method is much cheaper and easier than composting of filter cake. Soil health of arid degraded soils is expected to be more sustainable with the combined use of composted filter cake and plant growth stimulating bacteria than using fresh organic fertilizer alone.