Influence of sewage sludge, Rhizobium and arbuscular mycorrhizal fungi on nutrient uptake, growth, photosynthetic and biochemical attributes in Cicer arietinum L.

Recycling of sewage sludge (SS) as an organic amendment and a source of nutrients can be a potential option for proper disposal of organic waste. Symbiotic microbes show greater potential to carry out the bioremediation of heavy metals present in SS. A pot culture study was conducted to find the influence of SS and microbial symbionts [Rhizobium (R) and arbuscular mycorrhizal fungi [Funneliformis caledonius (Nicolson & Gerd.), Fc; and Glomus bagyarajii Mehrotra, Gb] on the growth of chickpea (Cicer arietinum L.). The major attributes of growth (height, fresh and dry weight and leaf number), photosynthesis (chlorophyll and carotenoid contents) and biochemical (protein and proline content) and the status of the uptake of N, P and K as well as the population of rhizospheric microbes were determined. Plants were grown in autoclaved garden soil alone (S) or garden soil amended with 20% SS with or without single or combined inoculation of symbiotic microbes in a pot experiment. SS amendment modified the properties of S by decreasing pH and increasing organic carbon in a resulting soil-sludge mixture (0.8 kg SS + 3.2 kg S). Plant sampling was done on 90 days after sowing. Highest plant growth, biochemical responses and nutrient contents were observed with SS + R + Gb treatment, whereas unamended soil without any inoculum exhibited the lowest values of the mentioned parameters. The content of proline, an indicator of stress, was found highest in C. arietinum raised in soil amended with SS. However, proline content decreased in the amended soil when inoculated with R + Gb. The nodulation and the percent root colonization were also found highest in SS-treated C. arietinum supplied with R + Gb. Overall, the study outcomes provide evidence that S mixed with appropriate amount of SS should be inoculated with combined inoculum of symbiotic microbes in order to achieve optimum growth, photosynthesis and biochemical attributes in economically important C. arietinum.