Integrating nano and water - soluble fertilizers for rationalising nutrient management of lowland rice (Oryza sativa L.) in the southern laterites

Abstract

The study entitled "Integrating nano and water-soluble fertilizers for rationalising nutrient management of lowland rice (Oryza sativa L.) in the Southern Laterites" was conducted at College of Agriculture, Vellayani, during 2022-2024. The objectives were to assess the effect of nano-N, nano-P and water soluble fertilizers on the growth, yield, and nutrient use efficiency of lowland rice and to work out the economics. The field experiment, laid out randomized complete block design with eight treatments and three replications, was undertaken at the Instructional Farm, Vellayani, from November 2023 to March 2024, with Uma (Mo 16) as the test variety. The treatments were T1: Nano-urea (0.4%) at active tillering (AT) + Nano-urea (0.4%) at panicle initiation (PI), T2: Nano-DAP (0.4%) at AT + Nano-DAP (0.4%) at PI, T3: Potassium nitrate (0.5%) at AT + Potassium nitrate (0.5%) at PI, T4: Nano-urea (0.4%) at AT + Nano-DAP (0.4%) at PI, T5: Nano-urea (0.4%) at AT + PSAP (0.4%) at PI , T6: Nano-urea (0.4%) at AT + Potassium nitrate (0.5%) at PI, T7: Urea (2.0 %) at AT + DAP (2.0%) at PI and T8: KAU POP. In all the treatments except T8, the recommended dose of nitrogen and phosphorus were reduced by 25 per cent and 50 per cent respectively. Foliar application of nano and water-soluble fertilizers significantly influenced the growth attributes of rice. Plants were taller (98.04 cm) at PI stage with nano urea (0. 4 %) at AT followed by Nano DAP (0. 4 %) at PI (T4). At flowering, plants were observed to be taller (111.10 cm) in T3 (0.5 % KNO3 at AT + PI). Comparatively taller plants (112.75 cm) were observed with T5 (0.4 % nano urea at AT + 0.4 % PSAP at PI) at harvest. Significantly more number of tillers per square metre at PI, flowering and harvest stages (556, 572 and 578 respectively) were noted in T5 (0.4 % Nano urea at AT + 0.4 % PSAP at PI). Similarly, T5 recorded a higher leaf area per hill at PI (977.13 cm2) and flowering stages (1148.80 cm2). Leaf area index at flowering and harvest stages were significantly higher (5.74 and 3.91 respectively) with nano urea (0.4 %) at AT followed by PSAP (0.4 %) at PI (T5). Flag leaf area per hill was also noted to be the highest (52.08 cm2) in T5. Further, leaf area duration from panicle initiation to flowering and flowering to harvest stages were found to be superior (154.16 days and 149.63 days respectively) in T5. Urea (2%) at AT followed by DAP (2%) at PI stages (T7), resulted in higher total dry matter production (11102 kg ha-1). Yield attributes including productive tillers per metre square (388), grains per panicle (202.33), and grain yield (5.44 t ha-1) were significantly higher with T5. Compared to KAU POP, T5 registered 8.15 per cent higher grain yield. Sterility percentage was less in T7 (2 % urea at AT + 2 % DAP at PI), which also recorded higher straw yield (7.39 t ha-1). Thousand grain weight and harvest index did not vary significantly in response to foliar nutrition. Chlorophyll content failed to vary significantly in response to foliar nutrition of nano and water-soluble fertilizers at flowering stage. Higher leaf nitrogen content (4.19 %) of rice plants at AT was observed in T5, whereas at flowering, T3 (0.4 % KNO3 at AT&PI) resulted in higher leaf nitrogen content (4.02 %). While N uptake was significantly higher (194.21 kg ha-1) in T6 (0.4 % nano-urea at AT + 0.5 % KNO3 at PI), P uptake (31.47 kg ha-1) and K uptake (317.01 kg ha-1) were observed to be superior in T7 (2 % urea at AT + 2 % DAP at PI) and T5 (0.4 % nano-urea at AT + 0.4 % PSAP at PI) respectively. Significant variation could not be observed in the crude protein content. Nutrient use efficiency in terms of partial factor productivity (PFP), agronomic efficiency (AE), physiological efficiency (PE) and apparent recovery efficiency (ARE) varied significantly with foliar nutrition. PFP and AE of N, P and K were noted to be significantly higher in T5. PFP in T5 was higher than KAU POP (8.12 per cent for N and 6.23 per cent each for P and K). However, T2 (0.4 % nano-DAP at AT + PI) resulted in significantly higher PEN and PEP, while PEK was higher in T3. AREN was the highest in T6, while AREP and AREK were higher in KAU POP (T8) and T5 respectively. Analysis of the post-experiment soil revealed higher soil reaction (5.93) with urea (2 %) at AT followed by DAP (2 %) at PI stage (T7), while significantly higher electrical conductivity (0.37 dS m-1) was observed with KAU POP (T8). The treatment, T5 (0.4 % nano-urea at AT + 0.4 % PSAP at PI) recorded higher (1.74 %) organic carbon content in the post-experiment soil. KAU POP (T8) was observed to leave the soil richer in available phosphorus (22.21 kg ha-1). However, available N and K of the post experiment soil did not show significant variation. Higher net income (₹ 76850 ha-1) and benefit cost ratio (1.65) were obtained with foliar nutrition of urea (2 %) at AT followed by DAP (2 %) at PI (T7), which was at par with T5 (₹ 74303 ha-1, 1.61). From the experiment it was concluded that KAU POP recommendation for medium duration rice, with recommended dose of nitrogen and phosphorus reduced by 25 per cent and 50 per cent respectively, supplemented with foliar application of nano urea (0.4 %) at active tillering stage followed by PSAP (0.4 %) at panicle initiation stage could be recommended for better growth, yield, nutrient use efficiency and economics in lowland rice. However, the effects were comparable with supplementation of foliar nutrition with urea (2%) at active tillering stage followed by DAP (2%) at panicle initiation stage with respect to grain yield, net income and BC ratio.