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Somaweera K.A.T.N.,University of Peradeniya | Suriyagoda L.D.B.,University of Peradeniya | Suriyagoda L.D.B.,University of Western Australia | Sirisena D.N.,Rice Research and Development Institute | De Costa W.A.J.M.,University of Peradeniya
Plant and Soil | Year: 2016

Background and aims: Knowledge on periodic uptake, accumulation and allocation of nitrogen (N), phosphorus (P) and potassium (K) in different tissues of a rice plant under different soil moisture management conditions is important when implementing efficient and effective water management practices ensuring sustainable rice production. Methods: Rice variety Bg358 was grown in soil columns containing sufficient amounts of N, P and K. Four water management treatments were used; (i) continuous flooding (CF) of soil from crop establishment to maturity, (ii) CF until tillering (4 weeks) and Alternative Wetting and Drying (AWD4) thereafter, (iii) CF until flowering (10 weeks) and AWD thereafter (AWD10), (iv) CF until flowering and Top Soil Drying (TSD) thereafter (TSD10). Harvests were made in 2 weeks intervals. Key results: Root growth of AWD4 decreased from 4th week compared with CF, and then enhanced from flowering onwards; thereby developing more roots in the top 20 cm soil layer increasing the root mass ratio. Both N and K uptake continued until maturity while P uptake continued until 2 weeks before maturity, and the amount taken up was highest for K and lowest for P. Moisture limitations substantially reduced tissue P content and retranslocation of P to panicles while the lowest reductions were observed in N. Therefore, internal utilisation was most efficient for P and lowest for N i.e., during grain filling N resorbed only from flag leaves, K from green, dead and flag leaves and only in AWD4, and P from green, flag and dead leaves, and stems. Conclusion: Initially reduced root growth under AWD stimulated after flowering. Soil moisture limitation reduced P uptake greatly and thus had most efficient internal P utilisation mechanisms throughout the life cycle while those of N were the lowest. © 2015, Springer International Publishing Switzerland. Source

Gunaratne A.,Sabaragamuwa University of Sri Lanka | Kao W.,University of Hong Kong | Ratnayaka J.,Rice Research and Development Institute | Collado L.,University of Hong Kong | Corke H.,University of Hong Kong
Journal of the Science of Food and Agriculture | Year: 2013

Background: Hydrothermal treatment used in parboiling could induce formation of novel starch properties having potential food applications. In the current work, functional, digestible and retrogradation properties of flour from non-parboiled and steamed parboiled six rice varieties with high amylose content of around 30% but differing in length and width ratio were investigated and compared. Results: The parboiling process reduced swelling volume and amylose leaching in all tested varieties. Among the varieties studied, the resistant starch content ranged from 1.6% in AT 306 to 0.46% in BG 357. Parboiling reduced the resistant starch content in AT 306 by about 50%, but it did not significantly affect the resistant starch content of the other varieties. The amylose-lipid complex remained unchanged after parboiling. Amylopectin retrogradation was not observed in parboiled rice. Amylose retrogradation was not seen except for AT 306. Pasting behaviour of parboiled rice flours showed high pasting stability and low setback. Flours were more susceptible to enzymatic hydrolysis after parboiling. Partial gelatinisation during parboiling was sufficient to produce grains with excellent milling quality showing a head rice recovery that ranged from 98% to 100% among the varieties studied. Conclusion: Degree of gelatinisation is the most important factor that determines the high head rice recovery. High pasting stability and low setback of flour of parboiled rice indicate some potential food applications. © 2013 Society of Chemical Industry. Source

Anputhas M.,Okanagan University College | Samita S.,University of Peradeniya | de Abeysiriwardena S.Z.D.,Rice Research and Development Institute
Communications in Biometry and Crop Science | Year: 2011

Identification of rice varieties with wider adaptability and stability are the important aspects in varietal recommendation to achieve better economic benefits for farmers. Multi locational trails are conducted in different locations/seasons to test and identify the consistently performing varieties in wider environments and location specific high performing varieties. The interaction aspect of varieties with environment is complex and highly variable across locations. Thus, the identifying varieties under these circumstances are difficult for varietal recommendations. However, several methods have been proposed in the recent past with the complex computation requirements. But, the aid of statistical software and other programs capabilities ease the complexity to a large extent. In this study, we employed one of the established techniques called variance component analysis (VCA) to make the varietal recommendation for wider adaptability for many varying environments and the location specific recommendations. In this method variety × environment interaction is portioned into components for individual varieties using yield deviation approach. The average effect of variety (environment centered yield deviation - D k) and the stability measure of each variety (variety interaction variance - s k 2) are used make the recommendations. The rice yield data of cultivars of three month maturity duration, cultivated across diverse environments during the 2002/03 wet-season in Sri Lanka was analyzed for making recommendations. Based on the results the variety At581 gave the highest D k value with wide adaptability selected for general recommendation. Varieties Bg305 and At303 also had relatively higher D k and thus these two can also be selected for general cultivation purpose. © CBCS 2011. Source

Chauhan B.S.,International Rice Research Institute | Abeysekara A.S.K.,Rice Research and Development Institute | Kulatunga S.D.,Rice Research and Development Institute | Wickrama U.B.,Rice Research and Development Institute
Weed Technology | Year: 2013

Dry-seeded rice systems are an emerging production technology in many Asian countries. A field study was conducted in 2011 and 2012 at the farm of the Rice Research and Development Institute, Batalagoda, Sri Lanka, to evaluate the performance of different herbicides in a dry-seeded rice system. Weed control treatments were nontreated (weedy), pretilachlor plus pyribenzoxim, cyhalofop-butyl, thiobencarb plus propanil, propanil, and bispyribac-sodium plus metamifop. All these POST herbicides were applied at 8 d after sowing, followed by an MCPA spray at 20 d after sowing. The dominant weeds in the study were barnyardgrass, Chinese sprangletop, and knotgrass. All herbicide treatments provided similar weed control, which ranged from 82 to 99%. Weeds in the nontreated plots reduced rice grain yield by 58 to 79% compared with the herbicide-treated plots. All herbicide-treated plots, except cyhalofop-butyl-treated ones, produced similar grain yield, which ranged from 3.7 to 4.2 t ha-1 in 2011 and from 6.0 to 7.0 t ha-1 in 2012. The results of our study suggest that different herbicides provided similar weed control and therefore different herbicides can be rotated in different seasons to reduce selection pressure on weeds. Source

Chauhan B.S.,International Rice Research Institute | Abeysekara A.S.K.,Rice Research and Development Institute | Kulatunga S.D.,Rice Research and Development Institute | Madusanka I.U.,Rice Research and Development Institute
Journal of Crop Improvement | Year: 2013

Dry-seeded rice (Oryza sativa L.) is an emerging establishment system in irrigated areas in many Asian countries, including Sri Lanka. A field experiment was conducted in the major (Maha) 2011/12 and minor (Yala) 2012 seasons at the research farm of the Rice Research and Development Institute, Sri Lanka, to evaluate the efficacy of several herbicides in an irrigated dry-seeded rice system. Herbicide treatments included propanil, followed by MCPA (2-methyl-4-chlorophenoxyacetic acid), pendimethalin, oxadiazon plus propanil, oxyfluorfen, and pendimethalin, followed by fenoxaprop plus ethoxysulfuron, oxadiazon plus propanil, followed by fenoxaprop plus ethoxysulfuron, and oxyfluorfen followed by fenoxaprop plus ethoxysulfuron. The efficacy of herbicides varied across years. All herbicide-treated plots had lower weed density and weed biomass than the untreated plots. The results suggested that oxyfluorfen applied alone provided the poorest weed control. Generally, there was no effect of the additional spray of fenoxaprop plus ethoxysulfuron on weed biomass at 42 days after planting. However, grain yield was higher in the plots sprayed with the pre-emergence, followed by post-emergence herbicides, compared with the plots sprayed with only pre-emergence herbicide(s). The results suggest that different herbicide options are available in Sri Lanka to effectively control weeds in dry-seeded rice systems. © 2013 Copyright Taylor and Francis Group, LLC. Source

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