The Journal of Research ANGRAU

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Research Notes J.Res. ANGRAU 41(1) 61-65, 2013 INFLUENCE OF NITROGEN AND WEED MANAGEMENT ON GROWTH AND YIELD OF AEROBIC RICE (Oryza sativa L.) K. SANDYARANI, M. MALLA REDDY, R. UMA REDDY and P.V. RAO Department of Agronomy, Agricultural College, Acharya N.G. Ranga Agricultural University, Aswaraopet - 507 301 Date of Receipt : 13.06.2012 Date of Acceptance : 06.11.2012 The soil N dynamics and path way of nitrogen losses in dry sown rice system are different from lowlands and result in different fertilizer nitrogen recoveries. The alternate moist and dry soil conditions may stimulate nitrification-denitrification processes in dry sown rice, leading to loss of nitrogen through N 2 and N 2 O (Prasad, 2011). Hence, traditional lowland rice fertilizer doses may not be optimum for aerobic rice. Further, aerobic soil conditions and dry tillage practices, besides alternate wetting and drying are conducive for germination and growth of highly competitive weeds, which cause grain yield losses ranging from 50-91%, compared to conventional production systems (Singh et al., 2006), in which weeds are suppressed by standing water and transplanted rice seedlings have a “head start” over germinating weed seedlings. As the concept of aerobic rice in Andhra Pradesh is new, relatively few insights into weed management and nitrogen fertilization exist. Hence, the present investigation was planned out to find out the optimum dose of nitrogen and effective weed management practice in aerobic rice. Field experiment was conducted during kharif, 2011 at Regional Agricultural Research Station, Warangal, Andhra Pradesh. The soil of the experimental site was sandy loam in texture, medium in available nitrogen (288 kg ha -1 ), low in available phosphorus (7.6 kg ha -1 ) and medium in available potassium (73 kg ha -1 ) with a pH of 8.1. The experiment was laid out in randomized block design (factorial concept) with three nitrogen doses viz., 120, 180 and 240 kg ha -1 and four weed management treatments, viz., pre-emergence application of pendimethalin @ 1.2 kg a.i. ha -1 + post-emergence application of pyrazosulfuron ethyl @ 30 g a.i. ha -1 at 25 DAS, mechanical weeding at 20 and 45 DAS, weed free check and weedy check replicated thrice. Rice variety ‘WGL-32100’ was sown by dibbling at 30 cm row spacing with solid rows with a seed rate of 40 kg ha -1 . Phosphorus and potash @ 60 and 50 kg ha -1 were applied uniformly as basal in the form of single super phosphate and muriate of potash, respectively. Nitrogen was applied in the form of urea as per the treatments in three equal splits, each at basal, active tillering and panicle initiation stage. A range of mean minimum temperature of 19.7 to 26.1 0 C and mean maximum temperature of 27.1 to 33.0 0 C was recorded during the crop growth period. A total rainfall of 349.4 mm was received during the crop season in 26 rainy days. Supplemental irrigation was given as and when required to maintain the soil in moist condition. The weed density and dry weight were recorded in each plot using a quadrant of 1 m × 1 m size. The data on weed density and dry weight were subjected to square root transformation before statistical analysis. Weed spectrum of the experimental field consisted of three groups of weeds like grasses, sedges and broad leaved weeds. The observed sedges were Cyperus rotundus, Fimbristylis argentea; grasses were Cynodon dactylon, Echinochloa colona, Dinebra retroflexa, Panicum javanicum and broad leaved weeds were Corchorus olitorius, Eclipta alba, Digera arvensis, Cyanotis axillaris, Psoralea corylifolia, Ammannia baccifera, Euphorbea geniculata, Phyllanthus niruri, Portulaca oleracea, Abutilon indicum, Celosia argentia, Commelina benghalensis, Merremia emarginata, Gynandropsis pentaphylla and Parthenium hysterophorus. Among these, broad leaved weeds were dominant followed by grasses and sedges in aerobic rice. email: ksragrico@gmail.com 66
SANDYARANI et al Weed parameters like weed density, dry weight, weed control efficiency and weed index were not significantly influenced by the application of different doses of nitrogen except weed density at 60 DAS and weed dry weight at 15 DAS and harvest (Table 1 ). At 60 DAS, the weed density recorded with 240 kg N ha -1 was significantly higher than 120 kg N ha -1 but was at par with 180 kg N ha -1 . Preemergence application of pendimethalin @ 1.2 kg a.i. ha -1 followed by pyrazosulfuron ethyl @ 30 g a.i. ha -1 at 25 DAS registered significantly lower weed density at all the stages of observation compared to weedy check and mechanical weeding except at 60 DAS where they were at par with each other (Table 1). Similar trend was observed with respect to the dry weight of weeds at 60 DAS. Higher weed control efficiency was recorded with herbicides than mechanical weeding at all the stages which led to lower weed index in the former treatment. The interaction between the nitrogen levels and weed management treatments was significant with respect to the dry weight of weeds at 15 DAS and harvest only. The weed dry weight was significantly higher with mechanical weeding compared to herbicides application at all the doses of nitrogen both at 15 DAS and harvest. Similarly, the dry weight of weeds significantly increased at 240 kg N ha -1 compared to 120 kg N ha -1 at 15 DAS and 180 kg N ha -1 as well at harvest except in the weed free treatment. This could be attributed to vigorous growth and development of weeds owing to higher uptake of nutrients at higher rate of nitrogen application. Similar results were reported by Sharma et al. (2007). Nitrogen removal by the weeds at harvest was significantly higher at 240 kg N ha -1 over 120 kg N ha -1 but at par with 180 kg N ha -1 (Table 2). It was also significantly more with mechanical weeding compared to herbicidal application which was at par with weedy check due to higher density and dry weight of weeds in the latter treatment. Singh and Tripathi (2007) also reported similar results. Application of 240 kg N ha -1 recorded significantly higher yield attributes and grain yield over 120 kg N ha -1 but at par with 180 kg N ha -1 except the test weight (Table 2). The straw yield was not significantly different among the different nitrogen doses. Increased yield under higher nitrogen levels might be due to adequate nutrient supply which would have resulted in increased growth and yield components. Similar findings were reported by Shekara et al. (2010). Among the weed management practices, pre-emergence application of pendimethalin @ 1.2 kg a.i. ha -1 followed by post-emergence application of pyrazosulfuron ethyl @ 30 g a.i. ha -1 at 25 DAS recorded significantly higher yield attributing parameters, grain yield and straw yield over mechanical weeding and it was comparable with weed free treatment. The increased grain yield was mainly due to effective control of weeds in herbicide applied plots (Jayadeva et al., 2011). The significantly lowest yield attributing parameters and yield among the treatments were observed with unweeded check owing to severe crop-weed competition throughout crop growth period. Nitrogen uptake by grain and straw of rice increased significantly with increasing doses of nitrogen upto 240 kg N ha -1 (Table 2). Among all the weed management practices, significantly higher nitrogen uptake by grain as well as straw was observed with herbicides compared to weedy check but at par with mechanical weeding (Table 2). The highest net returns and returns per rupee invested were obtained with the application of 240 kg N ha -1 over other two doses. Among the weed management practices, weed free check recorded highest values followed by pre-emergence application of pendimethalin @ 1.2 kg a.i. ha -1 followed by postemergence application of pyrazosulfuron ethyl @ 30 g a.i. ha -1 at 25 DAS. These results corroborate the findings of Jayadeva et al. (2011). It can be stated that application of 180 kg N ha -1 was found to be optimum for aerobic rice in sandy loam soils of Telangana region and pre-emergence application of pendimethalin @ 1.2 kg a.i. ha -1 followed by post-emergence application of pyrazosulfuron ethyl @ 30 g a.i. ha -1 at 25 DAS was found to be effective and economical weed management practice in aerobic rice during kharif season. 67
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CONTENTS PART I : PLANT SCIENCE Eff
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J.Res. ANGRAU 41(1) 1-4, 2013 EFFEC
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EFFECT OF FOLIAR APPLICATION OF NPK
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J.Res. ANGRAU 41(1) 5-13, 2013 NUTR
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NUTRIENT UPTAKE BY RICE CROP UNDER
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NUTRIENT UPTAKE BY RICE CROP UNDER
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Page 19 and 20: LAKSHMI et al Fig 1. Changes in C/N
Page 21 and 22: LAKSHMI et al Changes in C/N ratio
Page 23 and 24: LAKSHMI et al Table 3. Changes in h
Page 25 and 26: J.Res. ANGRAU 41(1) 20-29, 2013 INF
Page 27 and 28: PRASAD and PRASADINI of bulk densit
Page 29 and 30: PRASAD and PRASADINI to as high as
Page 31 and 32: PRASAD and PRASADINI Table 4 . Infl
Page 33 and 34: PRASAD and PRASADINI Table 8. Influ
Page 35 and 36: J.Res. ANGRAU 41(1) 30-38, 2013 GEN
Page 37 and 38: VEMANNA et al The range in mean val
Page 39 and 40: VEMANNA et al grain yield per plant
Page 41 and 42: VEMANNA et al 41
Page 43 and 44: VEMANNA et al Singh, S. P and Khan,
Page 45 and 46: RAMANA et al RESULTS AND DISCUSSION
Page 47 and 48: J.Res. ANGRAU 41(1) 42-46, 2013 A S
Page 49 and 50: RAJANNA et. al. Table 2. Reasons fo
Page 51 and 52: RAJANNA et al the present findings
Page 53 and 54: NARASIMHA et al Table 1. Proximate
Page 55 and 56: NARASIMHA et al Maynard, L., Lossli
Page 57 and 58: RAMANA et al with small follicles m
Page 59 and 60: RAMANA et al Characteristics of fol
Page 61 and 62: Research Notes J.Res. ANGRAU 41(1)
Page 63 and 64: KIRTHY et al Akhtar et al., 2008; S
Page 65: KIRTHY et al El Gharras H. 2009. Po
Page 69 and 70: SANDYARANI et al Table 2. Influence
Page 73 and 74: KUMAR et al Table 2. Effect of seed
Page 77 and 78: DEEPAK et al Table 2 Price spread a
Page 81 and 82: YAMINI et al Table 3. Estimates of
Page 83 and 84: YAMINI et al coupled with high per
Page 85 and 86: LOKESH et al Table 1. Clustering pa
Page 87 and 88: LOKESH et al Table 4. Mean values o
Page 89 and 90: ABIRAMI et al Socio-economic Impact
Page 91 and 92: ABIRAMI et al socio-economic impact
Page 95 and 96: VEMANNA et al Table 1. Discriminant
Page 97 and 98: VEMANNA et al total biomass, fresh
Page 99 and 100: RAO et al Table 1. Plant height, nu
Page 103 and 104: DEVI et al S.No Category Frequency
Page 105 and 106: DEVI et al extension contact and ma
Page 107 and 108: NIRMALA and VASANTHA earliness in a
Page 109 and 110: NIRMALA and VASANTHA adopted this t
Page 111 and 112: SUDHARANI et al Table 1. Genotypic
Page 113 and 114: SUDHARANI et al At genotypic level,
Page 115 and 116: NIRMALA et al weight of pods per pl
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NIRMALA et al Table 3. Cluster mean
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Research Notes J.Res. ANGRAU 41(1)
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PUNYAVATHI and VIJAYALAKSHMI 6.5 6.
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PUNYAVATHI and VIJAYALAKSHMI REFERE
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KATTEL et al Table 1. Item Analysis
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RADHIKA et al Thus, the results of
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RAJU et al estimated daily dietary
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RAJU et al Table 3. Physico-chemica
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MINNIE et al Table 2. Estimates of
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Statement about ownership and other
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GUIDELINES FOR THE PREPARATION OF M
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ESSENTIAL REQUIREMENTS FOR CONSIDER
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