Seed invigouration and weed management for enhancing productivity in aerobic rice (Oryza sativa L.)

Abstract

The experiment entitled “Seed inviguoration and weed management for enhancing productivity in aerobic rice (Oryza sativa L.) was conducted at College of Agriculture, Vellayani, Kerala during the period 2022-2024. The investigation pertaining to the study comprised two experiments. A pot culture experiment was conducted to assess the seed invigouration potential of liquid organic manures and field experiment to study the effect of seed invigouration and weed management regimes for higher productivity in aerobic rice. Pot culture experiment was conducted in September 2023 at the College of Agriculture, Vellayani. The experiment followed a completely randomized design (CRD) with 18 treatments in three replications. Treatments included beejamrit, jeevamrit, panchagavya, and vermiwash at 2.5 per cent, 3 per cent, 5 per cent, and 6 per cent concentrations, along with hydropriming and no priming. Seeds of Prathyasa variety were primed for 16 h and dried to original moisture before sowing. Seed priming with liquid organic manures significantly influenced seed germination parameters, seedling attributes, and vigor indices in rice. Among the treatments, beejamrit at 6 per cent concentration recorded higher germination percentage (90.0%), while beejamrit 5 per cent achieved the highest germination rate index (21.6). However, vermiwash 5 per cent proved superior in terms of overall germination performance, registering the highest germination index (125.3), greater speed of germination, and mean daily germination (2.1 no. d-1). In addition, the coefficient of rate of germination was higher in vermiwash 3 per cent (21.4). The shortest mean germination time (5.2 d) was observed with panchagavya 3 per cent. Beejamrit 6 per cent resulted in higher seedling vigor index I (3123) which was statistically on par with vermiwash at 3 per cent, 5 per cent, and 6 per cent, as well as panchagavya 5 per cent. In terms of seedling vigor index II, the higher value was observed with vermiwash 6 per cent (6.64), and was on par with vermiwash 5 per cent(6.49).

Based on the total scores, seed priming with 5 per cent and 3 per cent vermiwash concentrations which scored the highest scores of 253 and 237, respectively, were selected for further evaluation under field condition The field experiment was conducted at the organic farm of Department of Agronomy from January to May 2024, in randomized block design (RBD) with three factors. The first factor was two levels of seed priming [vermiwash 3 per cent (p1) and vermiwash 5 per cent (p2)] and a control (unprimed seeds). The second factor consisted of various weed management regimes [wheel hoe weeding (WHW) performed three times at 15, 30, and 45 DAS (r1), live mulching with cowpea followed by WHW at 45 DAS (r2), Gliricidia maculata leaf mulching at 10 t ha-1 followed by WHW at 30 and 45 DAS (r3), hand weeding (HW) thrice at 15, 30, and 45 DAS (r4), and weedy check (r5)]. The Prathyasa variety of rice was used for the study. Seeds were sown using a seed drill, and cowpea seeds were sown for live mulching at 7 DAS of rice and was uprooted and spread at 45 DAS during wheel hoe weeding. Similarly, Gliricidia maculata leaf mulching was also done on 7 DAS. At 15, 45, and 60 DAS, the treatment combination p2r5 resulted in taller plants. However, at 30 DAS and harvest, p1r3 and p2r3 produced taller plants, respectively. Tillers m² were higher in p2r1 at 30 and 60 DAS, though it was on par with p2r3 at 30 DAS and p2r4 at 60 DAS. At 45 DAS, p2r4 produced a greater number of tillers m², and at harvest, p2r3 had a greater number of tillers m². Dry matter production per plant was found to be higher in p2r4 at 15 DAS, and at the remaining stages, p2r3 resulted in higher DMP per plant. The treatment combination p2r1 exhibited higher LAI at 30, 45, and 60 DAS. The chlorophyll content was higher in p2r1 at 15 DAS, p1r2 at 30 DAS, and in treatments p1r3, p2r1, p2r2 and p1r3 at 60 DAS. At 30 DAS - 45 DAS and 60 DAS - harvest, p2r3 resulted in higher crop growth rate (CGR) (4.74 g m² d⁻¹ and 11.96 g m² d⁻¹, respectively). However, at 45 DAS - 60 DAS, p3r3 exhibited the highest CGR (10.85 g m² d⁻¹). For 15 DAS - 30 DAS, p1r1 resulted in higher relative growth rate (RGR) (0.228 g g⁻¹ d⁻¹). However, at 45 DAS - 60 DAS, p3r3 resulted in significantly higher RGR (0.063 g g⁻¹ d⁻¹), and from 60 DAS - harvest, p1r5 showed the highest RGR (0.038 g g⁻¹ d⁻¹).

The number of days to 50 per cent flowering ranged between 54 and 59 days across treatments, with the earliest flowering in seeds primed in p2r4 (vermiwash 5% + hand weeding thrice) (54 days). The treatment combination p2r2 had greater number of panicles m-2 (236 no. m-2) and 1000 grain weight, whereas, p2r4 had greater number of grains per panicle and p2r3 had higher panicle weight. The treatment combination, p2r3 resulted in significantly higher grain yield (2625 kg ha-1), straw yield and harvest index. Compared to p2r4 (unprimed seeds + hand weeding thrice), the percentage increase in grain yield observed in p3r3 (seeds primed in vermi wash 5 per cent concentration + G. maculata green leaf mulching with 10 t ha-1 fb WHW at 30 and 60 DAS) was 48.8 per cent. Weed infestation significantly reduced grain yield in aerobic rice. Among the treatment combinations, p3r5 recorded the highest weed index of 71.5 per cent. Among the quality parameters, the treatment combination, p3r1 resulted in higher starch content and was on par with all treatments except p1r1 and p3r4. At 15 DAS, p1r3 resulted in lower absolute density of BLW, however at 30 DAS, 45 DAS and 60 DAS, p2r4 registered lower absolute density of BLW. The absolute density of grasses was found to be lower in p2r2 and p3r5 at 15 DAS, p1r1 at 30 DAS, p2r1 at 45 DAS and p2r1 and p3r3 at 60 DAS. However, p1r3 resulted in lower total density of weeds at 15 DAS and p2r4 at the remaining stages. Weed dry weight was observed to be lower in p1r3 at 15 DAS and p2r4 at 30 DAS, 45 DAS and 60 DAS. Weed control efficiency also followed the same trend as that of weed dry matter. Nitrogen and P removal by weeds were observed to be lower in p2r4 at 30 DAS and 60 DAS. However, p2r4 showed lower K removal at 30 DAS and p3r4 at 60 DAS. The treatment combination, p2r2 resulted in higher N uptake by aerobic rice (72.6 kg ha-1) and it was followed by p2r3. However, p2r3 and p2r2 resulted in higher P uptake by aerobic rice (12.0 kg ha-1) and K uptake by p2r3 (48.4 kg ha-1). Interaction between seed priming and weed management regimes had significant effect only on organic carbon content and the treatment combination,

p3r2 resulted in higher OC content (0.91%) and was on par with p2r3. Available P content of post experiment soil was found to higher in p2r2. The treatment combination, p2r3 resulted in higher gross return, net return (₹ 97070 ha-1) and B: C ratio (2.20) and it was followed by p2r2. The study demonstrated that seed priming with liquid organic manures— particularly vermiwash at 5 and 3 per cent concentrations—significantly enhanced germination, seedling vigour, and early growth parameters in rice. Both seed priming and weed management practices had a substantial impact on crop growth, physiological traits, nutrient uptake, yield, weed suppression, and economic returns. Among all treatments, seed priming with 5% vermiwash combined with green leaf manuring using Gliricidia maculata (10 t ha⁻¹), followed by wheel hoe weeding at 30 and 45 DAS, emerged as the most effective strategy for maximizing yield and profitability under aerobic rice cultivation.