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Int.J.Curr.Microbiol.App.Sci (2017) 6(10): 2928-2943 International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 6 Number 10 (2017) pp. 2928-2943 Journal homepage: http://www.ijcmas.com Original Research Article https://doi.org/10.20546/ijcmas.2017.610.346 Study of Aerobic Rice under Varying Fertility Levels in Relation to Iron Application D. Rakesh*, P. Raghu Rami Reddy, Md. Latheef Pasha and T.V. Sreedhar Department of Agronomy, Agricultural College, Aswaraopet, Khammam-507301, Telangana, India *Corresponding author ABSTRACT Keywords Aerobic rice, N, P, K and Fe levels, Yield. Article Info Accepted: 23 September 2017 Available Online: 10 October 2017 A field experiment was conducted at Agricultural Research Station, Kampasagar, Nalgonda, during kharif, 2011 withMTU-1010 variety, to find out the optimum nutrient requirement for aerobic rice cultivation. The experiment comprising of two nitrogen levels (120 and 180 kg N ha-1), two phosphorus levels (60 and 90 kg P ha-1), two potassium levels (40 and 60 kg K ha-1) and two iron levels (0 and 25 kg Fe ha -1) were laid in ten plots replicated thrice. The results revealed that application of 180:90:60:25 kg N, P, K and Fe ha-1 registered higher number of tillers and panicles (491 and 381 m-2), filled grains panicle-1 (86.3), 1000-grain weight (26.97 g), grain and straw yields (4960 and 6034 kg ha 1 respectively) than the application of (120:60:40 kg N, P and K ha -1). However, it was on par with (180:90:60 kg N, P and K ha-1) which registered similar number of tillers, panicles (483 and 375 m-2),filled grains panicle-1 (84.7), 1000-grain weight (26.47 g), grain and straw yields (4873 and 5814 kg ha-1 respectively). Introduction Rice requires approximately 3000-5000 litres of water to grow one kilogram of rice traditionally. It is mostly grown under flooded conditions and consumes up to 43% of the world’s developed irrigation resources (Bouman et al., 2007). About 22 million hectares of irrigated dry season rice experience “economic water scarcity” in South and Southeast Asia (Tuong and Bouman, 2002). The availability of water for agriculture is declining steadily due to urbanization and rapid increase in population (Xue et al., 2008).Therefore, in coming decades, farmers all over the world will face severe water scarcity and everlasting competition for water exists in irrigated rice systems that will ultimately have an impact on overall production. Considering the future population growth, competition from nonagricultural uses of water and increasing demand for agricultural products, available water needs to be used efficiently. To reduce the share of water in rice cultivation, it is imperative to develop new way of growing rice that uses less water, while maintaining high yields. So, it was felt that there is a need to save water in rice cultivation, which led to development of aerobic rice. Aerobic rice is water saving production system in which potentially high yielding, fertilizer responsive adapted rice varieties are grown in fertile aerobic soils that are nonpuddled and have no standing water. 2928 Int.J.Curr.Microbiol.App.Sci (2017) 6(10): 2928-2943 Supplementary irrigation, however, can be supplied in the same way as to any other upland cereal crop (Wang et al., Bouman et al., 2005). The main driving force behind aerobic rice is the increasing water scarcity, which threatens the sustainability of lowland rice production. Aerobic rice is unique in its characteristics to withstand both flooding and dry soil conditions, which make it an ideal crop for areas prone to surface flooding where other crops would suffer or fail. The low and unstable yields of aerobic rice were mainly due to nutrient stresses. Nutrients are delivered to roots primarily by mass flow and diffusion but the delivery rate decreases as the moisture content of the soil decreases. The lower soil moisture content in aerobic rice cultivation therefore reduces nutrients supply to the roots and resulted in the lower rate of plant uptake. Understanding of nutrient uptake and response to fertilization effects are also urgently required to establish optimized crop management technology. As, rice is much more susceptible to iron deficiency than other cereals, presumably because it does not have an inducible ferric chelate reductase activity, as do plants that use the reduction strategy to generate ferrous iron from the more abundant ferric iron found in aerobic soils (Mori et al., 1991). So, there is an urgent need for formulating optimum dose of fertilizers for increasing the yields of aerobic rice. Considering the above facts, field experiment was conducted at ARS, Kampasagar to study the response of aerobic rice to varying fertility levels in relation to iron application. Materials and Methods The field experiment was conducted during kharif, 2011 under aerobic conditions at Agricultural Research Station, Kampasagar, Nalgonda district of Andhra Pradesh, situated at an altitude of 136.0 m above MSL on 16o51’.12.5” N latitude and 79o28’.28.4” E longitude. It is in the Southern Telangana agro-climatic zone of Andhra Pradesh. The experiment was conducted in sandy clay loam soil with moderate drainage. The soil was low in available nitrogen (125.44 kg ha-1), medium in available phosphorus (24.84 kg ha-1) and medium in available potassium (164.84 kg ha-1) contents. The pH of the soil was 6.38. A medium slender grain type variety, MTU-1010 of 110-120 days duration was grown. The experiment was laid out in randomized block design with ten treatments [T1–(120:60:40 kg NPK ha-1), T2–(180:60:40 kg NPK ha-1), T3–(180:60:60 kg NPK ha-1), T4–(180:90:40 kg NPK ha-1), T5-(180:90:60 kg NPK ha-1), T6–(120:60:40:25 kg NPK and FeSO4 ha-1), T7–(180:60:40:25 kg NPK and FeSO4 ha-1), T8–(180:60:60:25 kg NPK and FeSO4 ha-1), T9–(180:90:40:25 kg NPK and FeSO4 ha-1) and T10 –(180:90:60:25 kg NPK and FeSO4ha-1)] with three replications. Results and Discussion Tiller production The data pertaining to tiller production was recorded at active tillering, panicle initiation, flowering stages and at maturity stage are presented in Table 1. The tiller number was decreased from active tillering to harvest in all treatments (T1-T10). At all the stages of aerobic rice highest number of tillers m-2 (537, 523, 509 and 491 at active tillering, panicle initiation, flowering and harvest stages respectively) were recorded with the application of 180: 90: 60:25 kg NPK and FeSO4 ha-1 (T10). However, there was no significant difference in tiller number with varying fertility levels in relation to iron application. Lower number of tillers m-2 (423, 395, 363 and 353 at active tillering, panicle initiation, 2929 Int.J.Curr.Microbiol.App.Sci (2017) 6(10): 2928-2943 flowering and harvest stages respectively) was recorded with 120:60:40 kg NPK ha-1 (T1). Addition of 25 kg FeSO4 ha-1 (T6) resulted in the increase of tiller number m-2 by 6.6, 8.8, 14.3 and 12.2 % over the T1 at different growth stages of aerobic rice. Additional dose of 60 kg N ha-1 (T2) to T1 resulted in improvement of tiller number by (53, 67, 88 and 85 m-2) at active tillering, panicle initiation, flowering and harvest stages of aerobic rice. Inclusion of 25 kg ha-1 further enhanced tiller number m-2 by (13, 15, 9 and 6) and finally resulted in the tiller number of (489. 477, 460 and 444 m-2) at active tillering, panicle initiation, flowering and harvest stages of aerobic rice. Successive increase in the levels of fertilizers applied to aerobic rice has showed positive response on number of tillers m-2, though they had not reached the level of significance. Increase in the fertility levels increased the tiller production at all the stages of aerobic rice. The increased tiller number is due to availability of nutrients in sufficient quantities during the critical stages of crop growth. These findings are in accordance with the reports of Venugopal (2005), Alam and Azmi (1989), Raju et al., (1992), Sarkar et al., (1995) and Krishnappa et al., (1990). Study of the data pertaining to dry matter accumulation presented in table revealed that there was an increase in the dry matter production from active tillering to harvest in all the treatments (T1 to T10). The plant dry matter production at active tillering stage was maximum with the application of 180: 90: 60:25 kg NPK and FeSO4 ha-1 (T10), as it recorded highest plant dry matter m-2 (68.7 g) and it was followed by 180:90:60 kg NPK ha-1 (T5-65.6 g m-2). The next two best results were recorded by 180:60:60:25 kg N, P, K and Fe ha-1 (T8-63.7 g) and 180:60:60 kg NPK ha-1 (T3-61.2 g). At panicle initiation the influence of varying fertility levels in relation to iron application on plant dry matter was more pronounced. The application of 180: 90: 60:25 kg NPK and FeSO4 ha-1 (T10) had significant influence on dry matter production (524 g m-2) over 120:60:40 kg NPK ha-1 (T1-388 g m-2) and it was on par with 180:90:60 kg NPK ha-1 (T5514 g m-2). The next two best treatments were T8 (504 g m-2) and T3 (475 g m-2) where 180:60:60:25 kg NPK and FeSO4 ha-1 and 180:60:60:0 kg NPK and FeSO4 ha-1 were applied respectively. Dry matter accumulation At both flowering and harvest stages the response of aerobic rice to varying fertility levels in relation to iron application on plant dry matter production was not significant though the application of 180: 90: 60:25 kg NPK and FeSO4 ha-1 (T10) recorded highest plant dry matter of 919 and 1600 g m-2 at flowering and harvest stages over 120:60:40 kg NPK ha-1 (T1-652 and 1232 g m-2). Application of 25 kg FeSO4 ha-1 to T1 (T6) increased the plant dry matter by 46 and 29 g m-2 at flowering and harvest stages respectively. The data pertaining to plant dry matter production which was recorded at active tillering, panicle initiation, flowering and harvest stages were presented in Table 2. Enhanced nutrient application increased dry matter production at all stages. Increased nutrient availability at higher doses of fertilizers was responsible for profuse tillering Application of FeSO4 in aerobic rice has failed to claim significant effect on tiller number m-2. This might be due to involvement of Fe in plant physiochemical activity but it might not be a strong element to induce a drastic change in the plant growth. These findings are in accordance with the findings of Voigt et al., (1982), Kasana and Chaudry (1983) and Singh (1992). 2930 Int.J.Curr.Microbiol.App.Sci (2017) 6(10): 2928-2943 and ultimately higher plant dry matter production. Excluding panicle initiation stage, the influence of varying fertility levels in relation to iron application was not significant. These findings are in accordance with Laxminarayana (2003); Venugopal (2005); Sashikumar et al., (1995); Rao et al., (1991); Raju et al., (1999) and Thakur and Patel (1998). Application of FeSO4 in aerobic rice has failed to claim significant effect on DMP. This might be due to involvement of iron in plant physiological activity but it might not be a strong element to induce a drastic change in plant growth. These findings are in accordance with Voigt et al., (1982), Kasana and Chaudry (1983) and Singh (1992). Yield Attributes The data on yield attributing characters like productive tillers m-2, panicle length, total grains panicle-1, filled grains per panicle, unfilled grains per panicle and 1000 grain weight are presented in Table 3. Effective tillers m-2 A critical analysis of the data brings out the fact that the varying fertility levels in relation to iron application had failed to claim significant influence on effective tillers of aerobic rice. However, the highest number of effective tillers m-2 (381) was recorded where the maximum amount of the nutrients (180:90:60 kg NPK ha-1) were applied along with 25 kg FeSO4 ha-1 (T10). This was closely followed by application of same quantity of fertilizers except FeSO4 (T5- 375 m-2). Application of 120:60:40 kg NPK ha-1 (T1) recorded less number of effective tillers m-2 (331) in aerobic rice and with additional [60 kg N ha-1 (T2); 60, 20 kg NK ha-1 (T3); 60, 30 kg NP ha-1 (T4); 60, 30, 20kg NPK ha-1 (T5); 60, 30, 20kg NPK and 25 kg FeSO4 ha-1 (T10)] application of nutrients resulted in the yield improvements of 2.1, 10.6, 5.4, 13.3 and 15.1 % respectively over T1. Application of FeSO4 @ 25 kg ha-1 only improved the number of effective tillers m-2 of aerobic rice (T6 to T10) marginally when compared to their respective nutrient levels (T1 to T5). Addition of 25 kg FeSO4 ha-1 to 120:60:40 kg NPK ha-1 (T6) recorded an additional 4 effective tillers m-2 over no application of FeSO4 (T1) to the same nutrients. Efficient utilization of applied nitrogen as well as other major nutrients has resulted in more number of effective tillers at higher levels. These findings are in close agreement with the reports of Shekar et al., (2005), Kundu et al., (2004), Singh and Namdeo (2004), Dwivedi et al., (2006), Sarmah (1998) and Sathiya Bama and Selvakumari (2005). Panicle length Though there was an increase in panicle length with varying fertility levels in relation to iron application, their influence was not much pronounced on the length of panicle. However, application of 180:90:60:25 kg NPK and FeSO4 ha-1 (T10) recorded the maximum panicle length of (20.7 cm) followed by the application of same fertilizers except FeSO4 (T5-20.42 cm). Application of 120:60:40 kg NPK ha-1 (T1) recorded the minimum panicle length of 19.21 cm. Addition of 25 kg FeSO4 ha-1 to T1 improved the panicle length by 2.1%. Addition of 60, 30, 20 kg NPK and 25 kg FeSO4 (T10) to T1 enhanced the panicle length by 1.5 cm. These findings are in accordance with the works of Laxminarayana, 2003; Venugopal, 2931 Int.J.Curr.Microbiol.App.Sci (2017) 6(10): 2928-2943 2005; Ramamurthy and Shivashankar, 1996 and Ram et al., 1997. (120:60:40:25 kg ha-1) (180:90:60:25 kg ha-1) Total grains panicle-1 Increase in the total number of grains panicle1 at higher NPK and FeSO4 levels might have caused severe competition for carbohydrates thus resulted in increased hollow grain percentage. In lower NPK and FeSO4 levels, insufficient nutrients for filling of grains led to diminished grain number panicle-1; thus in this state, lower competition is the cause of decreased hollow grain percentage in panicle. These results are in accordance with the findings of Esfehani et al., 2005 and Mondal et al., (1987). Varying fertility levels in relation to iron application has failed to claim significant influence on total grains panicle-1 of aerobic rice. However, application of 180:90:60:25 kg NPK and FeSO4 ha-1 (T10) recorded highest number of grains panicle-1 (91) followed by the application of 180:90:60 kg NPK ha-1 (T588). Lowest number of grains panicle-1 (78) was recorded with the application of 120:60:40 kg NPK ha-1 (T1). Addition of 60, 20 kg NK ha-1 to T1 (T3) recorded more number of grains panicle-1 (85) than the addition of 60, 30 kg NP ha-1 to T1 (T4-83). Addition of 25 kg FeSO4 ha-1 to T1 (T6) recorded an increase of 2.6 % in the number of grains panicle-1. Number of filled grains panicle-1 There was no significant difference in the number of filled grains panicle-1 due to varying fertility levels in relation to iron application. Though maximum number of filled grains panicle-1 (83) were recorded with the application of 180: 90: 60:25 kg NPK and FeSO4 ha-1 (T10) and 180:90:60 kg NPK ha-1 (T5-81), the percent transformation of total grains panicle-1 to filled grains panicle-1 was more pronounced with the application of 120:60:40 kg NPK ha-1 (T1-94 %) than with the application of 180:90:60:25 kg NPK and FeSO4 ha-1 (T10-91 %). Number of unfilled grains panicle-1 The response of aerobic rice to varying fertility levels in relation to iron application has failed to claim significant influence on number of unfilled grains panicle-1. Unfilled grain percentage was increased with the increasing NPK and FeSO4 from 6.41 % to 8.79 % Test weight There was no significant difference in test weight due to varying fertility levels in relation to iron application. However, the test weight was increased with increase in nutrient levels. Maximum test weight (26.97 g) was recorded with the application of180: 90: 60:25 kg N, P, K and Fe ha-1 (T10) followed by the application of 180:90:60 kg N, P and K ha-1 (T5-26.47 g). The next two best treatments are T8 (26.2 g) and T3 (25.3 g) where 180:60:60:25 kg NPK and FeSO4 ha-1 and 180:60:60 kg NPK ha-1 were applied respectively. Minumum test weight (24.16 g) was recorded from the application of 120:60:40 kg NPK ha-1 (T1). Addition of 25 kg FeSO4 ha-1 to T1 increased the test weight marginally by 0.21 g. The efficacy of the fertilizers applied to aerobic rice was reflected in yield attributing characters like productive tillers m-2, panicle length, total grains panicle-1, filled grains per panicle, unfilled grains per panicle and 1000 grain weight, though they had not reached the level of significance. Increase in fertility levels increased the yield attributing characters of aerobic rice. The increase in yield attributes were mainly due to availability of nutrients in sufficient quantities 2932 Int.J.Curr.Microbiol.App.Sci (2017) 6(10): 2928-2943 during critical stages of crop growth which resulted in better growth characters and finally resulted in the growth of yield components of aerobic rice. These findings are in accordance with Shekhar et al., (2005), Kundu et al., (2004), Madhavi Latha (2001) and Raju et al., (1999). is clear that the role of Fe in rice plant is unparallel, but the amount of FeSo4 supplied to aerobic rice in the form of soil application might not be sufficient during the whole period of crop growth, thus resulting in the poor response of aerobic rice to ferrous sulphate application. Application of ferrous sulphate even upto 25 kg ha-1 as soil application has failed to influence the yield attributes of aerobic rice. It These observations are in close agreement with the findings of Sakal and Singh (1983), Tandon (1984) and Ghosh and Jena (1989). Table.1 Influence of varying fertility levels in relation to iron application on tiller number m-2 at various stages of aerobic rice Treatments (Nutrient levels (kg ha-1) T1(N120P60 K40) T2 (N180P60K40) T3 (N180P60K60) T4 (N180P90K40) T5 (N180P90K60) T6 (N120P60 K40FeSO4 25) T7 (N180P60K40FeSO4 25) T8 (N180P60K60FeSO4 25) T9 (N180P90K40FeSO4 25) T10 (N180P90K60FeSO4 25) CD (P = 0.05) SE(m) CV (%) Tiller number m-2 Panicle initiation Flowering 395 363 462 451 491 475 482 459 513 501 430 415 477 460 497 483 485 470 523 509 N.S N.S. 46.6 37.7 16.8 14.1 Active tillering 423 476 506 491 528 451 489 516 498 537 N.S. 26.6 9.4 Harvest 353 438 462 442 483 396 444 470 456 491 N.S. 35.7 13.9 Table.2 Influence of varying fertility levels in relation to iron application on plant dry matter g m-2 at various stages of aerobic rice Treatments [Nutrient levels (kg ha-1)] T1(N120P60 K40) T2 (N180P60K40) T3 (N180P60K60) T4 (N180P90K40) T5 (N180P90K60) T6 (N120P60 K40FeSO4 25) T7 (N180P60K40FeSO4 25) T8 (N180P60K60FeSO4 25) T9 (N180P90K40FeSO4 25) T10 (N180P90K60FeSO4 25) CD (P = 0.05) SE(m) CV (%) Active tillering 53.3 54.4 61.2 56.4 65.6 54 59.5 63.7 59.9 68.7 N.S. 6.5 19.0 Plant dry matter g m-2 Panicle initiation Flowering 388 652 440 791 475 833 449 780 514 909 414 698 451 793 504 899 454 797 524 919 48 N.S. 15.9 57.6 6.0 12.4 2933 Harvest 1232 1285 1411 1383 1555 1261 1287 1492 1408 1600 N.S. 164.8 20.5 Int.J.Curr.Microbiol.App.Sci (2017) 6(10): 2928-2943 Table.3 Influence of varying fertility levels in relation to iron application on yield attributes of aerobic rice Treatments (Nutrient levels (kg ha-1) T1(N120P60 K40) T2 (N180P60K40) T3 (N180P60K60) T4 (N180P90K40) T5 (N180P90K60) T6 (N120P60 K40FeSO4 25) T7 (N180P60K40FeSO4 25) T8 (N180P60K60FeSO4 25) T9 (N180P90K40FeSO4 25) T10 (N180P90K60FeSO4 25) CD (at 5%) SE(m) ± CV (%) Effective tillers m-2 331 338 366 349 375 335 346 374 354 381 N.S. 21.9 10.7 Number Number of Panicle of filled length(cm) grains grains Panicle-1 Panicle-1 19.21 19.67 20 19.87 20.42 19.61 19.73 20.17 19.88 20.7 N.S. 0.32 2.8 78 81 85 83 88 80 84 86 85 91 N.S. 5.9 12.2 73 74 78 77 81 75 78 81 79 83 N.S. 2.65 5.9 Number of unfilled grains Panicle-1 5 7 7 6 7 5 6 5 6 8 N.S. 0.7 19.7 Test weight (g) 24.16 24.49 25.28 24.7 26.47 24.37 24.6 26.2 24.83 26.97 N.S. 0.86 5.94 Table.4 Influence of varying fertility levels in relation to iron application on grain and straw yield (kg ha-1) of aerobic rice Treatments (Nutrient levels (kg ha-1) T1(N120P60 K40) T2 (N180P60K40) T3 (N180P60K60) T4 (N180P90K40) T5 (N180P90K60) T6 (N120P60 K40FeSO4 25) T7 (N180P60K40FeSO4 25) T8 (N180P60K60FeSO4 25) T9 (N180P90K40FeSO4 25) T10 (N180P90K60FeSO4 25) CD (P = 0.05) SE(m) CV (%) Grain yield (kg ha-1) 4281 4465 4767 4552 4873 4399 4534 4811 4584 4960 N.S. 169.9 6.4 2934 Straw yield Harvest index (kg ha-1) 4924 5253 5530 5336 5814 5143 5327 5812 5424 6034 N.S. 253.3 8.03 (%) 0.47 0.46 0.45 0.46 0.45 0.46 0.46 0.45 0.46 0.45 N.S. 0.01 3.70 Int.J.Curr.Microbiol.App.Sci (2017) 6(10): 2928-2943 Table.5 Influence of varying fertility levels in relation to iron application on nitrogen uptake (kg ha -1) at different crop growth stages of aerobic rice Treatments [Nutrient levels (kg ha-1)] T1(N120P60 K40) T2 (N180P60K40) T3 (N180P60K60) T4 (N180P90K40) T5 (N180P90K60) T6 (N120P60 K40FeSO4 25) T7 (N180P60K40FeSO4 25) T8 (N180P60K60FeSO4 25) T9 (N180P90K40FeSO4 25) T10 (N180P90K60FeSO4 25) CD (P = 0.05) SE(m) CV (%) Active tillering 8.2 9.8 10.3 10.3 11.4 8.8 10.3 10.4 10.3 11.6 N.S. 1.33 22.7 Nitrogen uptake (kg ha-1) Harvest Grain Straw 31.3 23 41.5 27 46 34.8 42.3 30.2 50.6 38.4 38 26.3 42.4 28.9 45.5 33.5 42.6 32.4 52.2 39.1 N.S. N.S. 5.5 4.02 22.1 22.2 Total 54.3 68.5 80.8 72.5 89 64.3 71.3 79 75 91.3 Table.6 Influence of varying fertility levels in relation to iron application on phosphorus uptake (kg ha -1) at different crop growth stages of aerobic rice Treatments [Nutrient levels (kg ha-1)] T1(N120P60 K40) T2 (N180P60K40) T3 (N180P60K60) T4 (N180P90K40) T5 (N180P90K60) T6 (N120P60 K40FeSO4 25) T7 (N180P60K40FeSO4 25) T8 (N180P60K60FeSO4 25) T9 (N180P90K40FeSO4 25) T10 (N180P90K60FeSO4 25) CD (P = 0.05) SE(m) CV (%) Phosphorus uptake (kg ha-1) Harvest Active tillering Grain Straw 1.36 11.4 5 1.56 12.5 5.4 2.18 14 6.9 1.79 13.3 6.2 2.42 15.2 7.6 1.49 12.3 5.3 1.64 13.1 5.9 2.19 13.5 6.4 2.16 13.2 6.7 2.73 16.2 8.7 0.8 2.2 N.S. 0.26 0.74 0.76 22.8 9.5 20.5 2935 Total 16.4 17.9 20.9 19.5 22.8 17.6 19 19.9 19.9 24.9 Int.J.Curr.Microbiol.App.Sci (2017) 6(10): 2928-2943 Table.7 Influence of varying fertility levels in relation to iron application on potassium uptake (kg ha -1) at different crop growth stages of aerobic rice Treatments [Nutrient levels (kg ha-1)] T1(N120P60 K40) T2 (N180P60K40) T3 (N180P60K60) T4 (N180P90K40) T5 (N180P90K60) T6 (N120P60 K40FeSO4 25) T7 (N180P60K40FeSO4 25) T8 (N180P60K60FeSO4 25) T9 (N180P90K40FeSO4 25) T10 (N180P90K60FeSO4 25) CD (P = 0.05) SE(m) CV (%) Potassium uptake (kg ha-1) Harvest Grain Straw 9.1 39.9 9.9 44 11 51.5 10.3 47.3 11.7 52.8 10.3 44.4 10.1 45.5 10.8 48.1 10.4 49.1 12 54.7 N.S. 7.2 0.7 2.4 11.8 8.8 Active tillering 5.3 5.9 6.6 6.1 7.1 5.5 6.0 6.7 6.1 7.3 N.S. 0.7 19.8 Total 49 53.9 62.5 57.6 64.5 54.7 55.6 58.9 59.5 66.7 Table.8 Influence of varying fertility levels in relation to iron application on iron uptake (g ha -1) at different crop growth stages of aerobic rice Treatments [Nutrient levels (kg ha-1)] T1(N120P60 K40) T2 (N180P60K40) T3 (N180P60K60) T4 (N180P90K40) T5 (N180P90K60) T6 (N120P60 K40FeSO4 25) T7 (N180P60K40FeSO4 25) T8 (N180P60K60FeSO4 25) T9 (N180P90K40FeSO4 25) T10 (N180P90K60FeSO4 25) CD (P = 0.05) SE(m) CV (%) Active tillering 8.3 13.4 20 16.4 25.4 13.5 15.4 23.6 18.8 30.9 N.S. 4.5 41.7 2936 Iron uptake (kg ha-1) Harvest Grain Straw 9.5 14.8 10.8 18.2 13.4 24.3 12.4 19.9 14.6 25.6 10.5 17.8 11.3 19.4 13.5 22.2 12.6 22.2 15.6 27 N.S. N.S. 2.2 4.1 30.1 33.2 Total 24.3 29 37.7 32.3 40.2 28.3 30.7 35.7 34.8 42.6 Int.J.Curr.Microbiol.App.Sci (2017) 6(10): 2928-2943 Table.9 Economics of varying fertility levels in relation to iron application in aerobic rice Treatment [Nutrient levels (kg ha-1)] T1(N120P60 K40) T2 (N180P60K40) T3 (N180P60K60) T4 (N180P90K40) T5 (N180P90K60) T6 (N120P60 K40FeSO4 25) T7 (N180P60K40FeSO4 25) T8 (N180P60K60FeSO4 25) T9 (N180P90K40FeSO4 25) T10 (N180P90K60FeSO4 25) Cost of cultivation (Rs. ha-1) 16982 17716 18247 18691 19222 20982 21716 22247 22691 23222 Grain yield A critical analysis of the data brings out the fact that the varying fertility levels in relation to iron application had failed to claim significant influence on grain yield of aerobic rice. However, the highest grain yield (4960 kg ha-1) was recorded where the maximum amount of the nutrients (180:90:60 kg NPK ha-1) were applied along with 25 kg FeSO4 ha-1 (T10). This was closely followed by application of same quantity of fertilizers except FeSO4 (T5- 4873 kg ha-1). Application of 120:60:40 kg NPK ha-1 (T1) recorded grain yield of 4281 kg ha-1 in aerobic rice and with additional [60 kg N ha-1 (T2); 60, 20 kg NK ha-1 (T3); 60, 30 kg NP ha-1 (T4) and 60, 30, 20 kg NPK ha-1 (T5); 60, 30, 20 kg NPK and 25 kg FeSO4 ha-1 (T10)] enhancement in dosages of nutrients resulted in the yield improvements of 4.29, 11.3, 6.3, 13.8 and 15.9 % respectively over T1. Application of FeSO4 @ 25 kg ha-1 only improved the grain yield of aerobic rice (T6 to T10) marginally when compared to their respective nutrient levels (T1 to T5). Addition of 25 kg FeSO4 ha-1 to 120:60:40 kg NPK ha-1 (T6) recorded an additional grain yield of 118 kg ha-1 over no application of FeSO4 (T1) to the same nutrients. Gross returns (Rs. ha-1) 52337 54763 58349 55800 59888 54608 55598 59234 56268 61131 Net returns (Rs. ha-1) 35355 37047 40102 37109 40666 33626 33882 36987 33577 37909 B:C ratio 3.08 3.09 3.20 2.99 3.12 2.60 2.56 2.66 2.48 2.63 The efficacy of the fertilizers applied to aerobic rice was reflected in grain yields though they had not reached the level of significance. Increase in fertility levels increased the grain yields of aerobic rice. The increase in grain yields were mainly due to availability of nutrients in sufficient quantities during critical stages of crop growth which resulted in better growth characters and yield components and finally on yield of aerobic rice. These findings are in accordance with Yogeshwar et al., (1980); Sharma and Prasad (1982); Raju and Rao (1987); Dalal and Dixit (1987); Patel et al., (1997) and Reddy and Kumar (1999) FeSO4 application to the aerobic rice has failed to claim a significant influence on grain yield. This might be due to insufficient amount of iron in the experimental plots which has resulted into low grain yields. The results are in agreement with the results reported by Singh et al., (1987); Zhang (1991) and Tandon (1996). N uptake by crop The data on N uptake at active tillering and at harvest by grain and straw is presented in Table 1. 2937