000			09724nam a22002057a 4500
999			_c374084 _d374084
082			_a631.4 _bKAM/BI Ph.D
100			_aKamali, B
245			_aBiostimulants for enhancing soil biological properties in wetland ecosystem
260			_aVellayani _bDepartment of Soil Science and Agricultural Chemistry, College of Agriculture _c2025
300			_a452p.
502			_aPh.D
520	3		_aThe study entitled “Biostimulants for enhancing soil biological properties in wetland ecosystem” was undertaken in Department of Soil Science and Agricultural Chemistry during the period December 2022 to October 2024. The objective of the study was to assess the effect of selected biostimulants in a wetland ecosystem on soil biological properties for crop growth and yield. The project was envisaged in four different parts, collection of geo-referenced soil samples from rice growing tracts of Southern Kerala, generation of thematic maps with highlighting Biological Fertility Index (BFI), characterization of biostimulants and evaluation of biostimulants through pot culture and field experiment. Geo-referenced soil samples (100 samples) were collected from five agroecological units (AEUs) viz. AEU 3 (Onattukara sandy soil), AEU 4 (Kuttanad soil), AEU 5 (Pokkali soil), AEU 8 (Southern laterites), and AEU 9 (South central laterites) of Southern Kerala at a depth of 0-15 cm. The collected samples were subjected to the characterization of soil biological properties. The biological properties of soil across the agroecological units (AEUs) exhibited notable variations. AEU 4 (Kuttanad soil) recorded the highest organic carbon (3.03 ± 1.19 %), microbial biomass carbon (628.57 ± 207.76 µg g-1), β-glucosidase activity (76.70 ± 14.88 µg p-nitrophenol g-1 soil h⁻¹) and acid phosphatase activity (111.60 ± 17.94 µg p- nitrophenol g-1 soil h-1). AEU 5 (Pokkali soil) noticed the highest microbial biomass nitrogen (197.30 ± 60.72 µg g-1), soil respiration (5.28 - 11.01 mg CO₂ g-1), dehydrogenase activity (682.54 ± 189.76 µg TPF g-1 soil h-1) and protease activity (111.09 ± 42.04 µg tyrosine g-1 soil h-1). In contrast, AEU 8 (Southern laterites) recorded the lowest microbial biomass nitrogen (50.17 ± 15.76 µg g-1), microbial biomass carbon (163.65 ± 84.16 µg g- 1), water soluble carbon, labile carbon, enzyme activities and microbial population. Using Principal Component Analysis (PCA), dehydrogenase was selected as PC1 (0.913), organic carbon from PC2 (0.669), microbial biomass carbon from PC3 (0.702), soil respiration from PC4 (0.847), and microbial biomass nitrogen from PC5 (0.721). The Biological Fertility Index (BFI) was computed using the procedure prescribed by Brookes et al. (1995). It was noted that AEU 5 recorded the highest biological fertility index, followed by AEU 4, AEU 9, AEU 3 and AEU 8 (AEU 5 > AEU 4 > AEU 9 > AEU 3 >AEU 8). The lowest biological fertility index (AEU 8) was selected for the pot culture experiment to evaluate the biostimulants. In Part II of the study, characterization of the biostimulants was carried out. As Part III of the study, a pot culture experiment was conducted in 2023 at the Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani, to evaluate the effects of various biostimulants on rice (Oryza sativa L.) growth and yield. The rice variety used was Uma and the treatments consisted of RDF (100 % RDF: 90:45:45 kg N, P₂O₅, K₂O per hectare), supplemented with FYM and lime as per KAU POP. Treatments included T1 (RDF + Seaweed extract at 12.5 kg ha-1), T2 (RDF + Humic acid at 10 kg ha-1), T3 (RDF + Fulvic acid at 5 kg ha-1), T4 (RDF + Lignosulphatehumate at 10 kg ha-1), T5 (RDF + Protein hydrolysate at 2.5 kg ha-1), T6 (RDF + Panchagavya at 3 %), T7 (RDF + PGPR mix- 1 at 2 %), T8 (RDF + Pseudomonas consortium at 2 %), T9 (RDF as per KAU POP) and T10 (Absolute control). This study involved the evaluation of different treatments on soil chemical, biological and enzymatic properties across three crop stages. T2 (RDF + Humic acid) recorded the highest pH, organic carbon, available K, Mg, B and enzyme activities of β- glucosidase, amylase and the lowest EC. T7 (RDF + PGPR mix-1) exhibited the highest available N, available P, labile carbon, microbial biomass carbon, soil respiration, glomalin content and enzyme activities of dehydrogenase, acid phosphatase and protease, along with the highest microbial populations. The highest available S was noticed in T1 (RDF + Seaweed extract), whereas, water soluble carbon in T3 (RDF + Fulvic acid). In contrast, T10 (Absolute control) recorded the highest micronutrient content (Fe, Mn, Zn and Cu). The enzyme activity number was computed based on the activity of five different enzymes viz., dehydrogenase, catalase, acid phosphatase, protease and amylase proposed by Beck (1984). The highest EAN was in T7 (RDF + PGPR mix-1) at 20.28, followed by T2 (RDF + Humic acid) at 19.45, T1 (RDF + Seaweed extract) as 18.63. Growth and yield parameters, including plant height, tillers, thousand grain weight and yield were the highest in T7 (RDF + PGPR mix-1). Chlorophyll content was the highest in T7 comparable to T2 (RDF + Humic acid), while proline content was the highest in control. N and P content along with their uptake in straw and grain were the highest in T7 (RDF + PGPR mix-1) while treatment T2 recorded the highest K content and uptake. Micronutrient content (Fe, Mn, Zn and Cu) in straw and grain were the highest in controlwith significant difference compared to other treatments, but uptake was the lowest. However, the lowest micronutrient content was recorded in T2 (RDF + Humic acid). The root parameters such as active roots, root length, root dry weight, root volume were reported the highest in T7 (RDF + PGPR mix-1). SEM micrograph of rice roots revealed that PGPR mix-1 enhanced microbial colonization and root-microbe interactions, with biofilm-like structures. Treatment with Humic acid resulted in moderate microbial attachment. This was further confirmed by TEM with higher magnification, with the presence of PGPR within the epidermal layers and near the cell walls of rice roots. Bacterial colonization in the root tissues was absent in SEM and TEM images of the control samples. Root metabolites such as p-coumaric acid, vanillic acid, and syringic acid were observed and found that significant variation among the treatments with the highest concentrations found in T7 (RDF + PGPR mix-1), followed by T2 (RDF + Humic acid) and T1 (RDF + Seaweed extract). The standing water analysis showed a slight increase in pH from the 1st to 14th week and the highest pH was observed in T2 (RDF + Humic acid). Total Fe and Al were the highest in the absolute control while the CO2 evolution rate was highest in T7 (RDF + PGPR mix-1). From the interpretations of results of pot culture experiment, based on the enzymatic activities, nutrient uptake, plant growth, yield and root parameters, three best treatments were selected such T7 (RDF + PGPR mix 1), T2 (RDF + Humic acid) and T1 (RDF + Seaweed extract). In Part 1V of the study, the superior three treatments from the pot culture experiment were evaluated through a field experiment conducted at the College of Agriculture, Vellayani. The study included six treatments: T1 (Best treatment 1), T2 (Best treatment 2), T3 (Best treatment 3), T4 (KAU organic POP), T5 (RDF as per KAU POP), and T6 (Absolute control). The experiment was laid out in a Randomized Block Design (RBD) with four replications. The results revealed that T2 (RDF + Humic acid) noticed the highest pH, organic carbon, available Ca and Mg. Available N and P were the highest in T1 (RDF + PGPR mix- 1) and K in T2 while the highest available S was noticed in T3 (RDF + Seaweed extract), while micronutrients (Fe, Mn, Zn and Cu) were the highest in the control except the boron. The labile and water-soluble carbon was the highest in T1 and T3 respectively. Enzyme activities were highest in T1 (RDF + PGPR mix-1). Humic acid fractions were the highest in T2 (RDF + Humic acid) treatmentThe study also assessed the effects of various treatments on rice growth, yield, nutrient uptake, root morphology and microbial interactions. RDF + PGPR mix-1 (T1) significantly recorded the highest EAN, improving growth, yield, root parameters, nutrient uptake (N, P, Ca and Mg), and microbial interactions. RDF + Humic acid (T2) recorded the highest K content and uptake. The control (T6) recorded the lowest growth, yield and nutrient uptake, but the highest Fe, Mn, Zn and Cu content. Root metabolites, chlorophyll, sugars and amylase were also the highest in PGPR mix-1, while proline content was the highest in the control. Standing water analysis showed the highest pH in RDF + Humic acid and the highest CO2 evolution rate in PGPR mix-1, indicating enhanced microbial activity. The economic analysis of treatments T1 (RDF + PGPR mix-1) recorded the highest net return, gross return and benefit-cost (B:C) ratio. The results suggest that T1 (RDF + PGPR mix-1) is the most cost-effective treatment, providing the highest profitability among all the treatments evaluated. The study concluded that biostimulants, particularly RDF + PGPR mix-1 @ 2 %, significantly improved rice growth, yield and nutrient uptake, while also enhancing soil biological properties, microbial interactions and nutrient dynamics in rice as evaluated through both pot and field experiments.
650			_a Soil Science and Agricultural Chemistry
650			_aSoil
650			_aWetland
650			_aEcosystem
700			_aAparna, B (Guide)
856			_uhttps://krishikosh.egranth.ac.in/handle/1/5810228084
942			_2ddc _cTH