Industrial waste based nano mineral fertilizer for yield enhancement in aerobic rice (Oryza sativa L.)

Abstract

The research entitled “Industrial waste based nano mineral fertilizer for yield enhancement in aerobic rice (Oryza sativa L.)” was conducted during 2023-2025 at College of Agriculture, Vellayani. The research programme was aimed at synthesis of nano slag, characterization of slag and nano slag and evaluation of nano slag based mineral fertilizer on growth and yield of aerobic rice. Nano slag was synthesized using high energy ball mill and SEM (Scanning Electron Microscope) analysis of the nano slag depicted angular, cube-like particles with a rough surface texture and often clustered together. The average particle size observed was 160 nm. X- ray diffraction spectra exhibited a broadened peak at 30º and 35º (2ϴ) indicating the presence of well-defined crystalline phase dominated by magnesium-rich periclase (MgO), calcium ferrite (CaFe2O4), lime (CaO), and (SiO2), along with fractions of manganese oxide and phosphate-associated minerals. FTIR (Fourier-transform infrared spectroscopy) spectra of nano slag revealed the presence of siloxane bond (Si-O-Si) corresponding to peaks at 711-602 cm-1 and 985-875 cm-1. X- ray fluorescence (XRF) analysis of the slag sample revealed that the material predominantly comprised of CaO (50.60%), Fe2O3 (15.40%), SiO2 (10.70%), MgO (1.71%), P2O5 (1.79%) and MnO (0.41%). The field experiment was carried out at the Instructional Farm, College of Agriculture, Vellayani, from March 26/03/25 to July 06/07/25, with KAU Manuratna as the test variety. The experiment was laid out in randomized complete block design with ten treatments replicated thrice. The treatments were a combination of two factors and a control, first factor being phosphorus fertilization (p), viz., p1-No Phosphorus fertilizer, p2- 50% RDP and p3-100% RDP, second factor, nano slag (n) viz., n1- without nano slag, n2- nano slag at 3 t ha-1 and n3- nano slag at 5 t ha-1) and control C- KAU (POP). FYM (Farm Yard Manure), N and K nutrients were applied uniformly as per KAU POP. Results of the experiment revealed that phosphorus fertilization and nano slag had a significant effect on the growth and yield attributes of aerobic rice. The treatment combination p3n3 (100% RDP + 5 t ha⁻¹ nano slag) resulted in taller plants at 30 DAS, 45 DAS and 60 DAS (55.77cm, 71.67 cm and 89.10 cm), with p2n3 (50% RDP + 5 t

ha⁻¹ nano slag) being statistically on par at 30 and 60 DAS, and p3n2 (100% RDP + 3 t ha⁻¹ nano slag) at 60 DAS. The lower plant height was observed in p1n1 (0% RDP without nano slag). The highest number of tillers m-2 (310.33, 426.10 and 508.54 m-2 respectively) was noted in p3n3 (100% RDP + 5 t ha⁻¹ nano slag) at 30 DAS, 45 DAS and 60 DAS. Leaf Area Index (LAI) was recorded higher in p3n3 (3.24, 3.69 and 4.19 respectively) at 30 DAS, 45 DAS and 60 DAS and was on par with p2n3 at 60 DAS. The Higher dry matter production (5428 kg ha-1) was recorded in p3n3 and was found to be on par with p2n3. Yield observations indicated that p3n3 (100% RDP + 5 t ha⁻¹ nano slag) resulted in higher number of productive tillers m-2 (435.58), Significantly higher number of grains per panicle (143.69), higher grain yield (3380 kg ha-1) and straw yield (4705 kg ha-1) and was found to be on par with p2n3 (50% RDP + 5 t ha⁻¹ nano slag) in all the yield parameters. The treatment combinations were compared with control treatment (KAU POP) by contrast analysis and found that p2n3 and p3n3 were on par with control in both grain and straw yield. Nutrient content and uptake also showed a significant variation across the treatment combinations. Higher uptake of N, P and K was recorded in p3n3 (75.641, 26.115 and 93.12 kg ha-1 respectively) and with respect to P and K, it was found to be on par with p2n3 (24.76 and 92.54 kg ha-1 respectively). The treatment p3n3 (100% RDP + 5 t ha⁻¹ nano slag) resulted in significantly higher content of Ca, Mg and Si in straw and grain and was found to be on par with p2n3. Micronutrient content of Mn and Cu in straw and grain were higher in p3n3 (100% RDP + 5 t ha⁻¹ nano slag), whereas Fe and Zn content were higher in p2n2 (50% RDP + 3 t ha⁻¹ nano slag). Among soil properties, Cation Exchange Capacity (CEC) was significantly higher (5.73, (c mol (p+) kg -1) in p1n3 (0% RDP + 5 t ha⁻¹ nano slag) and was found to be on par with p2n3(50% RDP + 5 t ha⁻¹ nano slag). However, pH was recorded higher (5.97) in p3n3 (100% RDP + 5 t ha⁻¹ nano slag). When compared against the control (KAU POP) p1n3, p2n3 and p3n3 were found to be on par. Soil Available N, P, K (248.50, 29.11, 189.93 kg ha-1 respectively), Ca, Mg and Si (283.56, 43.89 mg kg-1and 43.64 kg ha-1 respectively) were significantly highest in p3n3 (100% RDP + 5 t ha⁻¹ nano slag).

The chlorophyll content at 30 DAS showed no significant variation among the treatments whereas at 60 DAS it was found to be significantly higher in p3n3 (3.04 mg g-1). Dehydrogenase enzyme activity at 60 DAS was significantly higher in p3n3 (54.98 μg TPF g-1soil-1d-1) and it was found to be comparable with p2n3 (54.97 μg TPF g-1soil- 1d-1) and p3n2 (54.81 μg TPF g-1soil-1d-1). Among different treatment combinations p3n3 recorded significantly higher bacterial and fungal count (7.75 and 5.34 log cfu g-1 respectively). In bacterial count it was found to be on par with p2n3 (7.76 log cfu g-1), whereas in fungal count it was on par with p1n3 (5.31 log cfu g-1). Economics of the study revealed that although gross income was higher (1,41,825 ₹ ha⁻¹) in p3n3 (100% RDP + 5 t ha⁻¹ nano slag), the higher net income (45,600 ₹) and BC ratio (1.48) were achieved with p2n3 (50% RDP + 5 t ha⁻¹ nano slag). From the experiment it was concluded that application of 50% Recommended Dose of Phosphorus along with 5 t ha⁻¹ nano slag proved to be equally effective as 100% RDP + 5 t ha⁻¹ nano slag in enhancing crop growth, yield, and profitability of aerobic rice. Nano slag produced from industrial waste slag also substituted the entire lime requirement for aerobic rice enhancing soil pH, nutrient availability and supply of Si and micronutrients such as Fe, Zn, Cu, and Mn.