This research investigated the combined use of sewage sludge (SS) and plant growth-promoting rhizobia (PGPR) for Ridge gourd (Luffa acutangula (L.) Roxb.) cultivated under field conditions. The different treatments of SS and PGPR such as 0% (soil as control), 5% SS, 5% SS + PGPR, 10% SS, and 10% SS + PGPR were applied to assess their impacts on seedling growth, biochemical response, and yield performance of Ridge gourd. The results showed that the highest seedling emergence (92.3 ± 2.1%), fresh biomass (9.6 ± 0.3 g), growth rate (1.4 ± 0.1 g/day), seedling length (15.5 ± 0.3 cm), root length (10.4 ± 0.3 cm), total chlorophyll (3.2 ± 0.1 mg/g), crop yield (13.8 ± 0.1 kg/plant), and average crop yield per harvest (2.8 ± 0.1 kg/plant) were observed in 10% SS + PGPR treatment. The enzyme activities of superoxide dismutase (SOD; µg/g) and catalase (CAT: µg/g) were significantly lowered after PGPR inoculation in higher SS treatments. The results of principal component (PC) and Euclidian clustered distance analyses showed a positive influence of SS dose on soil nutrient availability and Ridge gourd’s growth, biochemical responses, and yield performance. Moreover, the elemental analysis showed that the bioaccumulation factor (BAF < 0.90) and health risk index (HRI < 0.40) of selected metal elements (Cd, Cr, Cu, Fe, Mn, and Zn) were within the permissible limits, indicating consumption of Ridge gourd fruits was safe. The outcomes of this study suggest the potential use of SS and PGPR for improved Ridge gourd production and contribution towards sustainable development goal (SDG) 12 on responsible consumption and production of vegetable crops.

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Combined Use of Sewage Sludge and Plant Growth-Promoting Rhizobia Improves Germination, Biochemical Response and Yield of Ridge Gourd (Luffa acutangula (L.) Roxb.) under Field Conditions

Sewage sludge (SS) in the soil acts as a slow-release organic fertilizer, and its nutrient supplying capability and heavy metal release occur for a prolonged period depending upon the applied doses. Field experiment not only evaluated the direct impact of SS application on rice (Oryza sativa L.) but also tracked the accumulation of lead (Pb), cadmium (Cd), chromium (Cr), and nickel (Ni) content in succeeding wheat (Triticum aestivum L.) crop and next-season rice and wheat crop. The field experiment was conducted with different levels of SS (15, 30, and 45 t ha−1) alone and in combination with 100% and 50% recommended doses of fertilizers (RDF). The findings indicated that the addition of SS (45 t ha−1) alone and in combination with inorganic fertilizers increased heavy metal accumulation in grain and straw of rice–wheat system and also led to enhanced DTPA-extractable metal content in post-harvest soil. Heavy metal concentrations in crops (except Cr content in straw) and soil stay below the phytotoxic limits in all treatments. However, total Cd in the soil exceeds the permissible limit with the sole application of SS beyond 30 t ha−1. This study admitted that one-time application of SS at the lower dose and reaping its benefits in subsequent crops can be an effective strategy of SS utilization in rice–wheat system.

Ashish Latare Marotrao

Papers

Assessing heavy metal accumulation in plants and soil with sewage sludge application under rice–wheat system in an Indo-Gangetic Inceptisol