Thakuria, DwipendraDevi, Mayanglambam Homeshwari2023-01-302023-01-302018-05https://krishikosh.egranth.ac.in/handle/1/5810192931Approximately 100 million-hectare of land suitable for rice production is currently under utilised because of the soil-related constraints. One of such constraints is high acidity induced limitation of essential nutrients for plant growth and development. Phosphorus (P) and Zinc (Zn) deficiency are widespread in approximately 42% and 43%, respectively of the arable lands in India. Phosphorus is not only deficient in rice soils but also finite in source (natural stock can support P fertilizer supply only for 105 to 470 years). Soil application of Zn often results in complexation with available P fractions in soil leading poor use efficiency of P and Zn. Silicon (Si) plays important beneficial roles especially in rice nutrition in terms of enhanced tolerance to abiotic and biotic stresses. However, soil application of Si is quite expensive for resource poor farmers. So, nutrient management approach should consider the principle of efficient utilization of applied nutrients ensuring maximum availability during critical periods of crop growth and minimizing the quantity to be applied. In the recent years, seedling root-dip (SRD) method is being increasing recognized as one of the efficient rhizosphere-based nutrient management approaches in terms of enhanced nutrient use efficiency and sustaining grain yield of rice in acid soil. The objectives of the present study were: (1) to determine uptake pattern of P, Zn and Si in SRD of rice cultivars (HYV, Hybrid and Traditional), (2) To find out the optimum doses of P, Zn and Si and their combinations in SRD methods, and (3) To compare the effectiveness of SRD method relative to soil and foliar application (SA and FA) of P, Zn and Si. The incubation experiments on SRD in soil slurry amended with P, Zn and Si (either alone or in combination) for three rice types (HYV- Ranjit, Hybrid – Arize 6444 and Traditional- Mendri) using two distinct acid soils (sandy clay loam, SCL, pH 4.98 and clay loam,CL, pH 4.52) was carried out. Results indicated that the optimum doses of P in soil slurry for SRD were 62, 88 and 138 mg kg-1 soil for traditional, HYV and Hybrid rice, respectively in SCL, and in CL soil, 88 mg kg-1 soil for both traditional and HYV rice and 112 mg kg-1 soil for Hybridrice. The optimum doses of Zn in soil slurry were 0.22 mg kg-1 soil for traditional and HYV riceand 0.78 mg kg-1 soil for Hybrid in SCL and 0.72, 1.24 and 1.72 mg kg-1 soil for traditional rice, HYV rice and Hybrid rice, respectively in CL. The optimum doses of Si in soil slurry were 225 mg kg-1 for traditional and HYV rice and 275 mg kg-1 for Hybrid rice in SCL and 175, 225 and325 mg kg-1 soil for traditional rice, HYV rice and Hybrid rice, respectively in CL. Results on the combination of two nutrients (P+Zn, P+Si, and Zn+Si) and three nutrients (P+Zn+Si) applied through SRD methods indicated that P+Zn and Zn+Si root-dipmethods showed the negative response in terms of nutrient content and their uptake inseedling biomass compared to that of their respective individual SRD method. Root-dip onP+Si added soil slurry showed the positive response of Hybrid rice in both soil types and HYVin CL soil. Root-dip on P+Zn+Si amended soil slurry also showed the negative response interms of P content and uptake in seedling biomass for all rice types in SCL and traditional ricein CL soil. However, it gave positive response in HYV and Hybrid rice in CL soil. The comparative effectiveness of SRD method relative to SA of P-Zn-Si and P+MCRD+50%RDP+foliar application (FA) of Zn and Si was evaluated on two field experiments (Kharif, 2015 at CPGS research Farm, Meghalaya and Kharif, 2016 at farmer’sfield, Kakching, Manipur). Soils of both experimental sites were acidic (Kharif, 2015 experimentwas SCL with pH 4.85 and Kharif, 2016 experiments was CL with pH 5.56). In the Kharif, 2015 experiment HYV rice variety CAU-R1 was used, and six nutrient treatments were allocated asper Randomized Block Design (RBD) with four replications. The treatments were: (1) control (no P input), (2) Microbial consortium root-dip (MCRD), (3) Multi-nutrients (P, Zn and Si) rootdip (MNRD), (4) MN+MCRD, (5) soilapplication of P, Zn and Si (SA of P-Zn-Si), and (6) P+MCRD+50%RDP+FA of Zn-Si. In the Kharif, 2016 experiment HYV rice variety CAU-R1 wasused and four nutrient treatments were allocated as per RBD design with 5 replications. The treatments were: (1) 100%RDP, (2) MNRD+50%RDP, (3) MN+MCRD+50%RDP, and (4)P+MCRD+50%RDP+FA of Zn-Si. In Kharif, 2015 experiment, the content and uptake of P, Zn and Si in shoot and root at different growth stages (30, 60 and 90 DAT), straw and grain at harvest and grain yield of rice were significantly higher in SA of P-Zn-Si treatment followed by P+MCRD+50%RDP+FA of Zn-Si as compared to that in other treatments. In the Kharif, 2016 experiment, the content and uptake of P, Zn and Si in shoot and root at 50 DAT were significantly higher in SRD treatments as compared to that in 100% RDP treatment. However, grain yield of rice among four treatments were comparable. In conclusion, the critical doses of P, Zn and Si in soil slurry for SRD method according to rice types (traditional, HYV and hybrid rice) for acidic SCL and CL soils were reported for the first time. The critical doses of P, Zn and Si in soil slurry SRD method for rice crop were in increasing order of Hybrid rice > HYV rice ≥ traditional rice. TheP+MCRD+50%RDP+FA of Zn-Si method was comparable to 100% RDP in terms of grain yield, harvest index and uptake of N, P, Zn and Si. The half quantity of the recommended P fertilizer dose can be reduced by adopting P+MC RD+50%RDP+FA of Zn-Si method in acid soil without compromising yield and approximate 2 times higher P use efficiency. Hence, P+MCRD+50%RDP+FA of Zn-Si method is recommended for enhancing nutrient use efficiency and sustaining higher yield of rice in acid soils.EnglishRice yieldNutrient managementThesis