Simulation of growth and yield of rice under varied ...

ISSN : 0976-7606

  Volume 1, No. 2 July - Dec, 2010

INDIAN SOCIETY OF HILL AGRICULTURE (Regd. 2010) URL: www.isharanichauri.com

Sharing Knowledge for Prosperity

Indian Society of Hill Agriculture (ISHA) was founded in 2010 having its secretariat at G.B. Pant University of Agriculture and Technology, Hill Campus, Ranichauri, Distt Tehri Garhwal, Uttarakhand, India with the main objective to cultivate and promote research, education and development of agriculture and allied branches of science with special emphasis on development of hill and mountain regions of the world.

OFFICE BEARERS Dr BS Bisht, Vice Chancellor, GB Pant Univ of Ag & Tech, Pantnagar, Uttarakhand Dr MC Nautiyal, Dean, College of Forestry and Hill Ag, GBPUAT, Ranichauri, Uttarakhand Dr PS Bisht, Dean, VCSG College of Horticulture, Bharsar, GBPUAT, Uttarakhand Dr AK Sharma, Additional Director Hort, Deptt of Hort, Govt of Uttarakhand, Chaubattia Dr SK Thakur, CSK HPKVV, Palampur, Himachal Pradesh Dr VK Rao, GBPUAT, Ranichauri, Uttarakhand Dr PJ Handique, Gauhati University, Guwahati, Assam Dr MS Mir, Sher-e-Kashmir Univ Ag & Sci Tech, Shalimar, Srinagar, Jammu & Kashmir Secretary: Dr VK Yadav, GBPUAT, Ranichauri, Uttarakhand Joint Secretary: Dr Sanjeev Sharma, Central Potato Research Institute, Shimla, Himachal Pradesh Dr Sunil Kumar, GBPUAT, Ranichauri, Uttarakhand Dr OC Sharma, Sher-e-Kashmir Univ of Ag Sci & Tech, RARS, Leh, Jammu & Kashmir Dr Vinod K Sharma, GBPUAT, Ranichauri, Uttarakhand Dr Mayank Rai, Central Agricultural University, Manipur Editor-in-Chief, J Hill Ag Dr Satish K Sharma, GBPUAT, Ranichauri, Uttarakhand Associate Editor Dr KC Sharma, CSKHPKVV, Kullu, Himachal Pradesh Treasurer: Dr Chandra Dev, GBPUAT, Ranichauri, Uttarakhand Business Manager: Dr AK Pandey, GBPUAT, Ranichauri, Uttarakhand Chief Patron: Executive Patron: President: Vice President (s):

Members From India

Members From Abroad

INTERNATIONAL ADVISORY BOARD Dr Mangla Rai, President NAAS and Former Secretary DARE, Govt. of India Dr P L Gautam, Chairman, National Biodiversity Authority, Govt. of India Dr Anwar Alam, Vice Chancellor, Sher-e-Kashmir Univ Ag & Sci Tech, Srinagar, J&K Dr KM Bujarbaruah, Vice Chancellor, Assam Agricultural University, Jorhat, Assam Dr K R Dhiman, Vice Chancellor, Dr YSP Univ of Hort & Forestry, Solan, HP Dr Bhag Mal, South Asia Coordinator, Biodiversity International, New Delhi Dr JDH Keatinge, Director General, AVRDC, World Vegetable Centre, Taiwan Dr Md. Yousuf Mian, Director General, BARI, Gazipur, Bangladesh Dr C Kole, Clemson University, South Carolina, USA Prof (Dr) FG Schroeder, Dresdan, Germany Dr G Paliyat, University of Guelph, Ontario, Canada Dr Ramesh Thakur, Michigan Technical University, Houghton, USA

EXECUTIVE COUNCILLORS Dr VK Joshi, Prof & Head, Univ Hort & Forestry, Solan, Himachal Pradesh Dr AK Singh, Professor, Horticulture, Banaras Hindu University, Varanasi, Uttar Pradesh Dr AK Singh, Professor and Head, Forestry, GB Pant Univ of Ag & Tech. Hill Campus, Ranichauri, Uttarakhand Dr Vandana A Kumar, Professor, Biological Sciences, GB Pant Univ of Ag & Tech. Hill Campus, Ranichauri, Uttarakhand Dr VK Sah, Professor Ecology, GB Pant Univ of Ag & Tech. Hill Campus, Ranichauri, Uttarakhand EDITORIAL BOARD (2010) Dr Pankaj Panwar, CSWCRTI Chandigarh Dr Alkesh Kandoria, PSCST, Chandigarh Dr Pawan Sharma, ICAR Res Complex Imphal, Manipur Dr Ashok Thakur, UHF, Solan, Himachal Pradesh Dr PS Kashyap, GBPUAT, Ranichauri, Uttarakhand Dr AV Singh, GBPUAT, Ranichauri, Uttarakhand Dr Rakesh Sharma, UHF, Solan, Himachal Pradesh Dr B K Khanduri, GBPUAT, Ranichauri, Uttarakhand Dr Rashmi Yadav, GBPUAT, Ranichauri, Uttarakhand Dr B Prasad, GBPUAT, Ranichauri, Uttarakhand Dr S Tripathi, GBPUAT, Ranichauri, Uttarakhand Dr BK Mishra, North Eastern Hill Univ, Meghalaya Dr SC Singh, CSUAT, Kanpur, Uttar Pradesh Dr BM Pandey, VPKAS, Almora, Uttarakhand Dr Shachi Shah, GBPUAT, Ranichauri, Uttarakhand Dr Deep Ji Bhat, SKUAST (J), Jammu & Kashmir Dr Med Ram Verma, IVRI, Izatnagar, Uttar Pradesh Dr TP Singh, GBPUAT, Ranichauri, Uttarakhand Dr Tsering Stobdan, DIHAR, Leh, Jammu & Kashmir Dr N Bhardwaj, CHF, Passighat, Arunanchal Pradesh For any queries pertaining to Indian Society of Hill Agriculture (ISHA) or Journal of Hill Agriculture (JHA) please write to Se cretar y / Editor-in-Chief (JHA), Indian Soc iety of Hill Agr ic ulture, G. B. Pant Univer sity of A griculture and Technology, Hill Campus, Ranichauri, Distt Tehri Garhwal, Uttarakhand – 249 199, India P h o n e : +91 1376 252651, 252650, 252138 Fax: +91 1376 252128, 252651 E mail: e ditor inc hiefj ha@ gm ail. co m URL : www.isharanichauri.com Online version of “Journal of Hill Agriculture” is availabe at www.indianjournals.com

Journal of Hill Agriculture, 2010 Vol 1(2) CONTENTS Hill Agriculture – fast forward MANGLA RAI

91

Effect of different levels of potassium on growth, yield and fruit quality of apple (Malus domestica Borkh) NS KAITH, DK MEHTA, USHA SHARMA

160

Exploring potential of traditional mountain agroecosystems in addressing food security and climate change issues in the central Himalaya VINOD KUMAR

94

Performance of various cultivars of pear in Kullu valley of Himachal Pradesh JAYANT KUMAR, JS CHANDEL

164

Micropropagation of Stephania japonica, a rare medicinal plant of north - east India PJ HANDIQUE, DEBOJA SHARMA

102

An analytical study on economics of saffron cultivation in Jammu and Kashmir SUDHAKAR DWIVEDI , TARUNVIR SINGH

168

Generation of Double haploids through induced androgenesis in Ethiopian mustard (Brassica carinata A. Braun) PHILEM SARINA, SANJAY CHADHA

107

Studies on heterobeltiosis in bittergourd (Momordica charantia L.) under mid hill condition of Uttrakhand ML KUSHWAHA, RP MAURYA

172

114

Effect of organic manures and biofertilizers on growth and yield of tomato and french bean under mid hills of Himachal Pradesh KS THAKUR, DHARMINDER KUMAR, AMIT VIKRAM, AK THAKUR, DK MEHTA

176

Simulation of growth and yield of rice under varied agronomic management and changing climatic scenario by using DSSAT ver. 4.0 crop model in Chitwan, Nepal A LAMSAL, LP AMGAIN Nitrogen and sulphur management in Gobhi sarson (Brassica napus L.) for improving yield, quality and soil properties in inceptisol of Himachal Pradesh DHANBIR SINGH

124

Correlation and path analysis in strawberry (Fragaria x ananassa Duch.) VK RAO, BHARAT LAL, VK YADAV, SK SHARMA

179

Performance of Pleurotus species on different substrates of hill region SK MISHRA, OMVEER SINGH, AK TIWARI

129

183

Effect of time of planting and planting densities on growth, yield and economic production of broccoli (Brassica oleracea L. var italica Plenck) cv. Pusa broccoli KTS-1 BR SAIKIA, DB PHOOKAN, SANCHITA BRAHMA

135

Standardization of feed rate and vacuum pressure for processing of seeds of bell pepper (Capsicum annuum L.) DK MEHTA, HS KANWAR, AK THAKUR Integrated nutrient management studies in grain amaranth (Amaranthus hypochondriacus L.) TEJ PRATAP, MANORANJAN DUTTA

187

190

KVK trainings for the farmers in hilly areas of Poonch district – identifying need of the hour NEERJA SHARMA, RK ARORA, SANJAY KHER

140

Effect of organic manures and biofertilizers on growth and fruit yield of tomato (Solanum lycopersicum L.) KS THAKUR, RAJESH THAKUR, YR SHUKLA, DK MEHTA, AK THAKUR

193

Genetic variability, characters association and path analysis in exotic lines of cabbage under mid hill sub humid conditions of Himachal Pradesh KC SHARMA

146

Manifestation of heterosis for quantitative traits in bacterial wilt resistant lines of brinjal (Solanum melongena L) VK SHARMA

197

Seed maturity indicators in Himalayan Cedar [Cedrus deodara (Roxb.) G.Don] SUNNY VERMA, TARA CHAND, RK NAYITAL, NARESH KUMAR

151

Stability for green pod yield in bush type french bean (Phaseolus vulgaris L.) under north-western Himalayas KC SHARMA

Relative susceptibility of okra varieties and hybrids to blister beetles (Mylabris spp.) in Himachal Pradesh ADITI BADIYALA

155

Awards of ISHA

i

Referees of JHA 2010 Vol 1(2)

ii

Advertisements

iii

Guidelines for authors

v

Membership form

vii

From the desk of Editor-in-Chief Dear readers and researchers, India holds very prominent place in agricultural production in the whole world, especially in south Asia. The green revolution has begun a new era of agriculture in the country making us self sufficient in food production. But it is a paradox that although, we have advanced so much in almost all segments of agriculture, but a revolution similar to the green revolution is still awaited in hill agriculture. It would not be wrong if I say that green revolution passed across but did not actually reach the hills of India as well as other hill regions of the world. Today also, we have problems and challenges like low productivity, lack of irrigation, depleting soil nutrient and health status, scarce or no package of practices for hill crops, low production from milch animals, lack of diversification and so many more. Difficult terrains, lack of transportation and marketing facilities, fragmented land holding, poor knowhow etc. further add to the grievances of hill farmers. The problems and challenges in hill agriculture are entirely different from that existing in the plains. Framing a common policy for the nationwide development of agriculture, would not be a wise step. The problems and prospects of agricultural production in hills therefore need to be addressed from a different angle. We cannot expect a major breakthrough in hill agriculture unless separate and dedicated steps are taken for that. It has always been a challenge for people, scientists and researchers to work under difficult agro-climatic conditions of the hills. For working in hills, people, alongwith their families, have to sacrifice the comfort and luxuries of their lives. This sometimes becomes very painful, especially under the situations wherein the workers do not receive any appreciation and recognition from those sitting at headquarters located in prime places or good cities. It requires many times more amount of labour, energy, time and resources to produce good results in various research programmes undertaken at hill research stations, than that required for similar accomplishments made by people at headquarters of the organizations. Unfortunately, in most of the organizations, we receive lesser recognition for the work done at small hill research stations. People sometimes spend all their lives working in hills and still await an encouraging tap on their shoulders from any one of their seniors. This a kind of feeling one can only understand if has served in hills. Nevertheless, there are a large number of contributions and achievements made by hill researchers which have made major changes in the field of agricultural development in hills. These efforts should continue on and on. Considering all the above, the thought of having some platform to recognize the work of agricultural researchers, scientists, teachers etc., in hills, was shaking my mind for the last many years. The difficulties somehow with all the cooperation of my colleagues at Ranichauri and in other organizations of hill states and the support of the administration of GBPUA&T laid the foundation of Indian Society of Hill Agriculture, under the purview of which, this “Journal of Hill Agriculture” was initiated. It is my pleasure to present the second issue of JHA before the readers. It has been a tiring time for all of us, especially the office bearers and members of the editorial board of JHA, who have worked day and night for accomplishing what was planned for the first year of the journal and the society. The overwhelming response of authors by contributing papers for the journal was also worth appreciation. In this small period of few months, we have made our journal available in print as well as online. The online submission and processing of manuscripts has also started and is being used by authors. I urge upon the authors to prefer the online mode of submitting their papers for faster processing. In the first two issues we have published papers on many aspects of hill agriculture including, agronomy, fruit science, vegetable science, soil science, postharvest technology, agricultural extension, agricultural economics, mushroom, plant protection, biotechnology, microbiology, forestry etc. Papers from persons of eminence in Indian agriculture were also published to give an insight for future development of hill agriculture. Since information delayed is information lost, we have tried our best to process the papers as fast as possible so as to disseminate the research findings at the earliest. Being new in the business of publication of research journals, we have faced many difficulties, but I hope the authors must have enjoyed the kind of effort we have put to process their manuscripts in short time and to improve the presentation of results in their papers. Hopefully, in years to come with all the cooperation of worthy members of the ISHA, we shall make gaint strides in hill agriculture and march forward towards achieving excellence in bringing out a research journal and recognizing the work of scientists in the hill regions of the world. I hope readers would welcome this issue of JHA and contribute their work for publication in their own hill journal. (Satish Kumar Sharma) Editor-in-Chief, JHA [email protected]

Journal of Hill Agriculture 1(2): 114-123, July-December 2010

RESEARCH PAPER Sharing Knowledge for Prosperity

Simulation of growth and yield of rice under varied agronomic management and changing climatic scenario by using DSSAT ver. 4.0 crop model in Chitwan, Nepal A LAMSAL  LPAMGAIN

Received: August 07, 2010; Revised: Nov 21, 2010; Accepted: December 01, 2010

ABSTRACT A field experiment on various cultivars and N levels on rice was carried out for identifying their growth and yield performance under humid sub-tropical climate of Chitwan, Nepal during rainy season of 2008. The simulation study for different agronomic and climate change parameters was also done concurrently by the use of CSM-CERES-Rice model embedded in DSSAT ver. 4.0. The experiment was laid out in 2 factorial RCBD with three replications consisting three varieties: hybrid ‘Prithivi’, improved check ‘Masuli’ and scented basmati ‘Sunaulo Sugandha’ and four levels of nitrogen: 40, 80, 120 and 160 Kg ha-1. Soil of experimental field was loamy sand in texture where in initial content of soil available N, P and K was medium in surface horizon and lower in sub surface horizon. Significantly higher grain yield (5.71 t ha-1) was obtained for Prithivi with 160 Kg N ha-1. The ancillary attributes viz. plant height, leaf area index (LAI), tillers m-2 and total dry matter production were significantly correlated with grain yield (r=0.58, 0.59, 0.89 and 0.84), respectively. The model calibration was performed with 160 Kg N ha-1 for Prithivi and Sunaulo Sugandha and 120 Kg N ha-1 for Masuli and the model validation was found to be satisfactory. The model was found sensitive to various scenarios of climate change parameters like weather years and different amplitudes of weather variables and other agronomic parameters viz. transplanting date, crop geometry and doses of N. Increment and decrease in maximum and minimum Lamsal A  Amgain LP Tribhuvan University, Department of Agronomy, Institute of Agriculture and Animal Science, Rampur, Chitwan, Nepal LP Amgain ( ) E mail: [email protected]

temperature (± 40C), CO2 concentration (+20ppm) with change in solar radiation (±1MJ m-2 day -1) resulted maximum increase in yield (by 62, 41 and 42%) under decreasing climatic scenarios in Prithivi, Masuli and Sunaulo Sugandha, whereas maximum decrease in yield (by 80, 46 and 40%) was recorded under increasing climate change scenarios, respectively. Similarly Prithivi showed 13 % decline under early transplanting (July 1) where as Masuli and Sunaulo Sugandha predicted 13 and 19% of yield loss by 20 days of delaying in transplanting (July 31) than the standard transplanting (July 11). Simulated yield of Prithivi was reduced by 5% for closer geometry of 20×20 cm2 and increased by wider geometry of 30×30 cm2 with reference to 25×25 cm2. N stressed (control) in Prithivi, Masuli and Sunaulo Sugandha reduced the yield by 17, 34 and 38%, respectively with maximum loss in improved check and scented varieties. Results showed that the CSM-CERES-Rice model could be a good tool for acquiring précised decision on the allocation of scarce resources and to increase the efficiencies of inputs in the hilly and inner-terai regions of central Nepal under the burning scenarios of global climate change. KEYWORDS DSSAT ver.4.0, growth and yield, rice, agronomic and climate change scenarios INTRODUCTION Globally, rice (Oryza sativa L.) is most important food crop since it provides more than 60% share of the world’s population as staple food. In Nepal, agriculture holds major share of economy (31.07% of GDP) on which rice alone contributes 20.75% of the agriculture gross domestic product (AGDP) (MoAC 2008). Rice is the dominant crop in the terai and inner terai and still dominant in certain foot-hill pockets of Nepal. Available decadal yield data in

Journal of Hill Agriculture (Volume 1, No. 2 July-December 2010)

115

Nepal indicates changes in average national rice yields from 1.80 t ha-1 during 1960-69, to 2.85 t ha -1 during 2004 (MoAC 2004), and ultimately 2.55 t ha-1 in 2008 (MoAC 2008). Among the various factors responsible for the lower production of rice, the choice of proper cultivars suited to the agro-eco-zones and their planting geometry and other several agronomic management factors including low nitrogen use efficiency especially ineffective splitting of N application are the major (Adhikari et al. 2008, Devkota et al. 2008). Several cultivars of rice especially high yielding varieties (HYV’s), hybrids and scented basmati are the desire of Nepalese farmers to fulfill their family need and uplift their economy. Experiments in China, India and Vietnam had established that hybrid rice offers an economically viable option to increase cultivars yield beyond the level of semi dwarf rice cultivars (Joshy 2001). In Chitwan and its adjoining foot-hill areas the improved cultivar Masuli has still been popular to the majority of farmers since 1970, hybrids cultivars supplied from Indian markets are dominating in the regions since about last 510 years due to their high yield potential and scented basmati are also becoming popular at advance (Amgain and Timsina 2005). Fertilizer use efficiency in south Asia and especially in Nepal is very low (30-40%) and increasing temperature and predicted adverse scenario of climate change in future is further likely reduce it. This will lead to increased fertilizer requirement for meeting increased future food production demand which to the large number of resource poor farmers in the tropics and sub tropics regions of Nepal could not seem possible. Simulation modeling studies done at different places, advocated that agronomic management including N management could vary depending on the management strategies and climate change scenarios and it may benefit to the majority of farmers (Aggarwal 2003, 2008).

Agriculture contributes the significant of green house gas emission in south Asia primarily due to CH4 and N2O emission from rice by the application of manures and nitrogenous fertilizers in to the soils. Potential approaches to reduce these emissions include mid-season drainage or alternate wetting and drying of rice field and approaches to increase N-use efficiency and soil carbon etc. Simple adaptation strategies such as change in planting dates and varieties could also help in reducing the impacts of climate change to some extent.

Through a series of observations and modeling studies, the Inter-Governmental Panel on Climate Change (IPCC) has shown that the earth temperature has increased by 0.740 C between 1906 and 2005 due to increase in anthropogenic emissions of green house gases. By the end of this century, temperature increase is likely to be 1.8-4 0C (IPCC 2007). This would lead to more frequent hot extremes, floods, droughts, cyclones and gradual recession of glaciers, which in-turn would result in greater instability of food production. The increase in GHGs was 70% between 1970 and 2008 (IPCC 2007). The global increases in CO2 concentration are due to primarily to fossil-fuel use and land use change, while those of methane and nitrous oxide are primarily due to agriculture. It has also been estimated that crop production loss in south Asia by 2100 AD could be 10-40% despite the beneficial effects of higher CO 2 on crop growth.

MATERIALS AND METHODS

Cropping system model (CSM-CERES-Rice) is a decision support tool used widely to evaluate and/or forecast the effects of environmental conditions, management practices, and different genotypes on rice growth, development and yield (Asadi and Clement 2003). Earlier versions of the DSSAT model (ver. 3.5) have been evaluated across rice growing environments of Asia and Australia and their performance has been generally satisfactory, but variation exists (Timsina and Humphreys 2003). Similarly, Pathak et al. (2002), Timsina et al. (2004), Amgain et al. (2006) and Amgain and Timsina (2007) evaluated the CERES-Rice model (ver. 4.0) for soil mineral N and loss processes from rice fields under Rice-Wheat systems for Delhi, Modipuram and Punjab in north-west India. In context of Nepal, the model had not been tested over different locations of country except the few studies conducted in maize, e.g., by Sapkota et al. (2008) in winter maize and Bhusal et al. (2008) in spring maize. In this context an attempt has been tried to study the field performance of different rice cultivars under graded levels of Nitrogen and simulation results of CSM-CERES-Rice model on the growth and yield under changing agronomic management and climatic scenarios of sub-tropical condition of central Nepal.

Field experimentation The field experiment was carried out at the Research Block of the Agronomy Farm of IAAS Rampur, Chitwan, Nepal (27o37’ N; 84 o25’E and 256 amsl) from June to November 2008. The place is situated in humid-subtropical climate but resembles the foot-hill and inner-terai climate. The total rainfall during the crop growing season was 1333.52 mm. The mean maximum and minimum temperatures were 30.77 oC and 21.62 oC, respectively for the crop season. During the crop period, average maximum temperature ranged from 33.2 oC (June) to 28.09 o C (November). Similarly, minimum temperature ranged from 25.08 oC (June) to 13.08 oC (November). The relative humidity ranged between 83.53% on the month of June to 94.7% on the month of November. The experiment was

A LAMSAL  LP AMGAIN

116

carried out in two factors factorial randomized complete block design with three replications. The treatment consists of combination of the three rice cultivars (hybrid as Prithivi, improved check as Masuli and scented cultivar as Sunaulo Sugandha) and four levels of N (40, 80, 120 and 160 Kg ha-1). The upper surface soil of the research site was loamy sand in texture and neutral in reaction (pH 7.3). Total nitrogen and soil available phosphorous was found medium at upper soil profile but found decreasing with increasing soil depth. The r recommended agronomic management practices were followed to accomplish the experimentation except the fertilizer treatments. Yield and yield attributing characters were recorded, tabulated and analyzed using MSTAT-C computer software and statistical package as mentioned by Gometz and Gometz (1984). Simulation modeling Various data on experimental field crops were taken in consideration for making appropriate input files required to run the DSSAT ver 4.0 crop models. Those characters include data sets required for experimental file (file X), yield attributes (file A), growth attributes (file T), Soil file (file S) and Weather file (file W). Model calibration was performed for all three rice cultivars with recommended dose of 160 Kg N ha-1 for Prithvi and Sunaulo Sugandha, and with 120 Kg N ha-1 for Masuli taking it under potential production condtion. Prithivi and Sunaulo Sugandha were validated for 40, 80 and 120 Kg N ha-1, whereas Masuli with 40, 80 and 160 Kg N ha-1 was used to validate the model. The parameters used for the validation of CERES-Rice were anthesis date, days to physiological maturity, grain yield and unit grain weight. Sensitivity analysis was accomplished with 160 Kg N ha1 in Prithivi and Sunaulo Sugandha, and 120 Kg Nha-1 with Masuli for various agronomic traits. Similarly, simulation to different scenarios of climate change was

accomplished by selecting weather year’s bases and by increasing or decreasing the values in maximum and minimum temperature by 4oC, increase or decrease in solar radiation by 1 MJ m -2 day -1 and increase of CO 2 concentration by 20 ppm to the base level of 350 ppm for all cultivars of tested rice genotypes. Other agronomic management options like transplanting date and spacing, and N amount and their application timings were also verified to simulate the growth, phenology and yield of rice. RESULTS AND DISCUSSION Statistical analysis The grain yield of Prithivi (4.93 t ha -1 ) was significantly higher than Msauli and Sunaolo Sugandha (Table 1). Prithivi produced 44 and 23% more yield than the Masuli and Sunaulo Sugandha, respectively. The higher grain yield of Prithivi was because of higher LAI and higher number of effective tillers and other yield attributes (Table 2) than other two varieties under test. Walker et al. (2008) reported that hybrid technology produced 17 to 20% greater yield compared with the inbred cultivars. Virmani (1996) also reported that hybrid rice had larger panicles and more spikelets per panicle. There was significant interaction on the grain yield between varieties and levels of N application. Prithivi produced the highest grain yield (5.71 t ha-1) at 160 Kg Nha-1 and this was significantly higher than Masuli and Sunaulo Sugandha at each level of N application. Yang and Sun (1990) reported that hybrid rice takes up about 15-20% of the total amount of N accumulated in the plant after heading and conventional varieties used only 6-7%. Table 2 clearly indicated that the highest effective tillers m-2 were recorded in Prithivi (158) which was significantly higher than Masuli (149.5) and Sunaulo Sugandha (135.3). This might be due to its high genetic

Table 1 Grain yield of rice as influenced by variety and levels of nitrogen Grain yield (t ha -1) Varieties Dose of nitrogen -1

40 Kg ha 80 Kg ha -1 120 Kg ha-1 160 Kg ha-1 Mean LSD (0.05) ( Interaction) LSD(0.05) (Varieties) LSD(0.05) (Fertilizer)

Prithivi de

4.17 4.70 bc 5.13 b 5.71 a 4.93 a

Masuli g

3.22 3.45f g 3.89 ef 3.12 g 3.42 c

Sunaulo Sugandha fg

3.58 3.87 ef 4.14 de 4.47 cd 4.01 b 0.510 0.255 0.295

Mean 3.65c 4.00 b 4.39a 4.45a 4.12

Treatment means followed by common letter/letters within column are not significantly different among each other based on DMRT at 0.05


117

Table 2 Yield attributes of rice as influenced by varieties and levels of nitrogen Variety

Varieties Prithivi Masuli Sunaulo Sugandha LSD(0.05) SEM± Fertilizer 40 Kg ha -1 80 Kg ha -1 120 Kg ha-1 160 Kg ha-1 LSD(0.05) SEM± C.V%.

Effective tillers (No m -2) a

158.0 149.5 b 135.3 c 6.884 2.347 127.1 d 140.2 c 156.1 b 167.0 a 7.949 2.710 5.51

Panicle wt.(g)

a

4.18 3.26 b 4.49 a 0.564 0.192 4.10 4.13 3.75 3.92 NS 0.224 16.77

Panicle length (cm) b

26.83 24.05 c 30.41 a 0.7396 0.2522 26.97 27.23 26.96 27.53 NS 0.2912 3.22

Filled grain(No. panicle -1) a

165.2 136.5c 157.6 b 17.46 5.955 136.1 d 147.7c 159.7 b 168.8a 0.8422 0.2872 13.47

Sterility %

b

11.38 10.57 c 16.83 a 0.607 0.207

12.54 12.72 13.28 13.16 NS 0.2390 5.5

Test wt(g)

a

23.52 18.06c 23.24 b 0.2439 0.0831 21.64 21.68 21.47 21.64 NS 0.096 1.33

Straw yield (t ha-1)

Harvest index%

7.011 b 7.259 b 8.567 a 0.280 0.096

41.18 a 31.96 b 31.86 b 1.765 0.602

7.300 b 7.464 b 7.834 a 7.851 a 0.324 0.110 4.36

33.43 b 34.94 ab 35.91 a 35.72 a 2.038 0.695 5.96

Treatment means followed by common letters/letters within column are not significantly different among each other based on DMRT at 0.05.

and vegetative hybrid vigour for Prithvi. Singh and Panwar (1994) also reported that rice hybrid had higher vegetative vigour. The significantly higher numbers of effective tillers m-2 were found in 160 Kg N ha-1 as indicated by Rao and Moorthy (2002). It was revealed that Sunaulo Sugandha (4.49 g panicle-1) had heavier panicle followed by Prithivi (4.18 g panicle-1), however, the higher yield in Prithivi might be due to higher number of filled grains than other high yielding varieties. Significantly longer panicle length was found in Sunaulo Sugandha (30.41 cm) than in Prithivi (26.83 cm) and Masuli (24.05 cm).

was adjacent to the result of Chopra and Chopra (2000). The harvest index of Prithivi (41.18%) was significantly higher than Masuli (31.96%) and Sunaulo Sugandha (31.86%). Higher harvest index of Prithivi might be due to more N translocation in to panicles after flowering than in to those of conventional cultivars. Hybrid Prithivi had less plant stature and dry matter records than the Masuli and Sunaulo Sugandha. Yang and Sun (1990) also reported the same result.

It was observed that Prithivi had significantly higher 1000-grain weight (23.5 g) than other cultivars Sunaulo Sugandha (23.24 g) and Masuli (18.06 g). Significantly higher filled grains panicle-1 was obtained in Prithivi (165) than other cultivars Sunaulo Sugandha (158) and Masuli (137). Salgotra et al. (2002) also reported that hybrid had high heterosis for grains panicle-1. Number of filled grains panicle-1 was significantly enhanced with the increased levels of nitrogen. Significantly higher number of filled grains panicle-1 was recorded from 160 Kg N ha -1 (169) than from 120 (160), 80 (148) and 40 (136) Kg N ha -1, respectively. Sterility percentage was significantly higher in Sunaulo Sugandha followed by Prithivi and Masuli. Significantly lower sterility percentage was obtained in Masuli. Sunaulo Sugandha had recorded the significantly highest straw yield than Prithivi and Masuli. The straw yield at 160 Kg N ha-1 was highest for all cultivars and that might be due to the higher dry matter accumulation. Vigorous growth (plant height and dry matter) with increase in N level resulted higher straw yield and this

The data sets for the three rice cultivars viz. Prithivi and Sunaulo Sugandha with 160 Kg N ha-1 and Masuli with 120 Kg N ha-1 were used to determine the genetic coefficient of the rice cultivars under study by using the CSM-CERES-Rice model. The genetic coefficients were adjusted until there was a close match between the observed and simulated dates of anthesis, physiological maturity and grain yield. Table 3 presents the summary of the runs for the calibration of model for all three rice cultivars; Prithivi, Masuli and Sunaulo Sugandha. The genetic coefficients P1 to P20 represents the parameters related to growth attributes and G1 to G4 indicate the yield attributes.

Model calibration and validation

The CSM-CERES-Rice model was validated by using the above determined genetic coefficients of three varieties with their respective fertilizer levels as Prithivi and Sunaulo Sunganda with 40, 80 and 120 Kg N ha-1 and Masuli with 40, 80 and 160 Kg N ha-1. Observations on anthesis days, days to physiological maturity, grain yield, and unit grain weight were used for the model validation.


118

Table 3 Estimating genetic coefficients for rice cultivars Cultivars

Prithivi Masuli Sunaulo Sugandha

P1

P2R

P5

Genetic Coefficients P2O G1 G2

70 40.7 91.9

0.7 86.1 32

30 51 20

0.2 0.8 0.9

9.9 2.4 2.2

.295 .0202 .242

G3

G4

0.97 1.0 1.0

1.13 1.0 1.0

Simulated values A PM GY 74 103 112

104 134 145

5754 3892 4468

Observed values for Prithivi: Anthesis date 74, Physiological maturity days: 104, yield 5754, Masuli: Anthesis date 103, PM: 134, yield 3892, and Sunaulo Sugandha: Anthesis date 112, PM: 145, yield 4468

Predicted grain yield was well-agreed with observed yield (RMSE=747.353, d-stat =0.793). Similarly, close agreement was observed between observed and simulated anthesis date (RMSE = 1.106 d-Stat = 0.99) and physiological maturity date (RMSE = 2.58, d-stat = 0.994). These validation results showed that the CERES-Rice model could safely be used as a tool for simulation of different agronomic and climate change parameters at the agroclimatic situation of central Nepal. Sensitivity of models to various climate change parameters The model was found sensitive to weather years and various scenarios of climate change. The simulated yield for hybrid Prithivi, Masuli and Sunaulo Sugandha was 17%, 12% and 12% lesser in 2007 than the standard year 2008, respectively. In the year 2005, Prithivi produced 20% lesser yield than standard. This decline in the yield was due to the lower solar radiation and scanty rainfall in the years 2005 and 2007 as compared to the other years. It was revealed that average temperature was higher in the year of 2006, which shorten maturity days of Masuli and Sunaulo Sugandha and yield declined by 9 and 8% respectively (Fig 1 a, b and c). Singh and Ritchie (1993) also reported that increased temperature reduce rice yield significantly. The model was found to be sensitive to climate change parameters (temperature, solar radiation and CO2 concentration). Change in maximum and minimum temperatures (+40C), CO2 concentration (+20 ppm from the base of 350 ppm) with change in solar radiation (1MJ m-2 day-1) resulted maximum differences in yield. The result showed that with the decreasing scenarios of maximum and minimum temperature by 4 0C and other factors increasing results in increased grain yield by 62, 41 and 42% of Prithivi, Masuli and Sunaulo Sugandha while maximum decrease in yield of 80, 46 and 40%, in above case just with increasing maximum and minimum temperature by 40C, respectively. Hence hybrids seem more sensitive to increased temperature than the others. The decline in rice yields and their associations with rising night temperatures have been noticed in the south Asia (Aggrawal 2003) and Philippines (Peng et al. 2004). Recent

Fig 1 Simulated (a) average daily temperature (b) daily precipitation (mm) during rice growing season and (c) daily photosynthetically active radiation (MJm-2day-1)

meta-analysis of CO2 enrichment studies in fields has shown in the field environments, 550 ppm CO2 leads to benefit of 8-10% in yield in wheat and rice and almost negligible in maize (Long et al. 2005). Increased CO2 concentrations would reduce transpiration and N losses and increase water, N and radiation use efficiencies and could be beneficial to rice and wheat (Singh and Padila


119

Table 4 Sensitivity of simulated yield and phenology of rice cultivars to weather years Weather years Simulated yield (Kg ha-1) Percent yield Anthesis (days) Physiological maturity (days) Prithivi

Masuli

Sunaulo Sugandha

a

2008 a 2007 2006 2005 2008 a 2007 2006 2005 2008 a 2007 2006 2005

5754 4759 5679 4629 3892 3420 3530 3640 4468 3939 4098 4208

100 83 98 80 100 88 91 94 100 88 92 94

74 75 75 75 103 102 99 101 112 111 108 110

104 105 104 103 134 132 128 133 145 142 137 143

Standard years

Table 5 Sensitivity analysis of rice cultivars with changes in temperature, S.R. and CO 2 concentration Max temp (oC) +0a

+4

-4

+4

-4

+4

+4

-4

-4

a

Min temp ( oC)

CO2 conc. (ppm)

Solar radiation (MJm-2day-1)

Treatments

Simulated yield (Kg ha-1)

% yield change

Growth duration (days)

+0

350

+0

Prithivi

5754

100

104

Masuli

3892

100

134 145

+4

-4

+4

-4

+4

+4

-4

-4

350

350

+20

+20

+20

+20

+20

+20

+0

+0

+0

+0

+1

-1

+1

-1

Standard climatic conditions, S.S = Sunaulo Sugandha

S.S.

4468

100

Prithivi

1320

23

96

Masuli

2310

59

111

S.S.

2928

66

117

Prithivi

8533

148

139

Masuli

4895

125

212

S.S.

5684

127

226

Prithivi

1360

24

96

Masuli

2365

61

111

S.S.

2994

67

117

Prithivi

8686

150

139

Masuli

5144

132

212

S.S.

6027

134

226

Prithivi

1548

27

96

Masuli

2613

67

111

S.S.

3294

73

117

Prithivi

1177

20

96

Masuli

2104

54

111

S.S.

2686

60

117

Prithivi

9342

162

139

Masuli

5486

141

212

S.S.

6385

142

226

Prithivi

7976

138

139

Masuli

4624

119

212

S.S.

5278

118

226


120

1995). At high CO2, light intensity positively affects photosynthesis and slightly increased temperature promotes both photosynthesis and leaf area. Zhiqing et al. (1994) showed that the direct effects of increased CO2 concentration would compensate for the negative effects of increased temperature on rainfed rice at most sites of China. The beneficial effect of higher CO2, however with the increased temperatures and increased variability of rainfall would considerably affect food production. Several IPCC studies also has indicated that there is the probability of 10-40% yield loss in crop production by 2050 to 2100 in South Asia (Fischer et al. 2002, Parry et al. 2004, IPCC 2007). Sensitivity analysis to agronomic management options The simulated yield of Prithivi (Table 6) was increased by 5 to 16% under delayed transplanting (July 21 and July 31) but yield was declined by 13% under early transplanting (July 1). Yield of Masuli and Sunaulo Sugandha was decreased by 13, and 19%, respectively under delayed

transplanting of July 31. While yield of Masuli increased by 6% under early transplanting (July 1). Virmani (1996) reported that transplanting of hybrid rice was usually done when sixth to seventh leaves as fully expanded, which corresponds to a seedling age of 15-20 days. Hybrid varieties are comparatively short in maturity and require less water to grow. Nepalese rice farming is mostly rainfed and under this situation days of seedling transplanting marked a significant response in yields. The improved and scented rice cultivars are long in duration and require more days to mature and their transplanting at late condition could not coincide with the requirement of light and temperature and results lesser yield in farmers’ field. Farmers generally grow rice after harvesting their summer maize maturing in late July and hence hybrid rice would be economical to them to utilize their lands and get the higher benefit. CERES-Rice was run for 3 different crop geometries (Table 7). In the standard treatment plant was transplanted with geometry of 25×25 cm2, where sensitivity was analyzed with geometry of 20×20 cm2 and 30×30 cm2. It

Table 6 Sensitivity of simulated yield and phenology of rice cultivars to date of transplanting Planting date Prithivi

Masuli

Sunaulo Sugandha

a

Simulated yield (Kg ha -1) Percent yield Anthesis (days)

July 11a July 21 July 31 July 01 July 11a July 21 July 31 July 01 July 11a July 21 July 31 July 01

5754 6014 6308 4732 3892 3918 3387 4135 4468 4328 3603 4505

100 105 116 87 100 100 87 106 100 97 81 101

Physiological maturity (days)

74 75 75 75 103 102 102 103 112 111 113 112

104 107 107 104 134 138 142 136 145 148 149 140

Standard dates

Table 7 Sensitivity of simulated yield and phenology of rice cultivar to crop geometry

Prithivi

Masuli

Sunaulo Sugandha

a

Standard crop geometry

Planting geometry (cm 2)

Simulated yield (Kg ha -1)

Percent yield change

Anthesis (days)

Physiological maturity (days)

25×25 a 20×20 30×30 25×25 a 20×20 30×30 25×25 a 20×20 30×30

5754 5459 6035 3892 4017 3856 4468 4497 4421

100 95 105 100 103 100 100 100 98

74 74 74 103 103 103 112 112 112

104 104 104 134 134 134 145 145 145


was raveled that narrower the spacing, increment in yield by 3% in Masuli and this was due to the higher plant population since Masuli has not a profuse tillering and therefore also recommended for transplanting with the 20×20 cm2 spacing (NARC 2004). Jayawardena and Abeysekera (2002) have also reported that 20 ×20 cm2 is the optimum geometry for most of the HYV’s under optimum management conditions. Prithivi yields 5% less at closer geometry and that might be due to the increased sterility percentage at closer geometry. Verma et al. (2000) reported that hybrid rice planted at closer geometry (20×10 cm2) results significantly higher sterility percentage than wider geometry. Nitrogen stress (0 Kg N ha-1) showed a greater reduction in rice yield (34% in Prithivi, and 38% in Sunaulo Sugandha) over 160 Kg N ha-1 and 34% reduction in Masuli over 120 Kg N ha-1. Simulation of N dose with application of 200 Kg ha-1 resulted decrease in yield of all Prithivi, Masuli and Sunaulo Sugandha and proportionate decrease is high in Masuli (17%) than the other two. Amgain and Timsina (2007) reported that simulated yield was reduced by 58% by reducing level of N from 120 to 0

121

Kg ha-1 at PAU soil. Nitrogen stress limits cell division, chloroplast development, enzymes activity and reduced dry matter yields (Gardner et al., 1985). Principally leaves are the primary organ for solar radiation interception and photosynthesis. As the leaf area index increases, light interception is more resulting in higher dry matter production and higher grain yield. High N (200 Kg ha -1) could not show any increase in the yield which mostly enhance biomass yield and increased the percentage sterility. Reddy and Reddi (2005) reported that leaf expansion depends upon N supply, whereas high nitrogen application leads to development of larger leaves sometime reducing aeration and increased effective tillers. But all the combination of balanced nutrients is needed for the higher yield. Nitrogen was lost through leaching, volatilization and denitrification under the flooded paddy soil condition. Amount of loss in higher dose of N-application was 18165%, 1-48% and 22.10-667.3% more against no Napplication condition through leaching, volatilization and denitrification, respectively (Table 8). Due to unavailability of water for continuous flooding, alternate

Table 8 Sensitivity of simulated yield, N-uptake, and N losses in rice to dose and timing of fertilizer application Dose of N (Kg/ha)

Timing of N application

Varieties

Simulated Yield (Kg/ha)

% yield change

N Uptake (Kg/ha)

N Leached (Kg/ha)

N Volatilized (Kg/ha)

N Denitrified (Kg/ha)

120*

60 Kg N/ha (basal) +30 Kg N/ha (35 DAS) +30 Kg N/ha (at PI stage) 0 Kg N/ha


5736 3892 4082

100.00 100.00 100.00

104.83 170.53 179.42

1.16 1.16 1.16

0.16 0.18 0.17

58.27 32.91 30.59

Prithivi Masuli Sunaulo Sugandha Prithivi Masuli Sunaulo Sugandha

2112 1514 1638

36.82 38.90 40.13

41.07 59.68 62.88

0.00 0.00 0.00

0.00 0.00 0.00

10.72 9.81 10.47

5360 2649 2682

93.44 68.06 65.70

96.92 104.46 107.68

0.18 0.17 0.17

0.01 0.01 0.01

13.09 13.30 13.95


5736 3468 3628

100.00 89.10 88.88

104.83 146.94 150.04

0.67 0.67 0.67

0.06 0.06 0.06

32.76 17.33 17.55


5736 3892 4469

100.00 100.00 109.48

104.83 172.35 198.50

1.65 1.65 1.65

0.43 0.48 0.46

82.29 57.71 49.20

0

40

80

160

20 Kg N/ha (basal) +10 Kg N/ha (35 DAS) +10 Kg N/ha (at PI stage) 40 Kg N/ha (basal ) +20 Kg N/ha (35 DAS) +20 Kg N/ha (at PI stage) 80 Kg N/ha (basal) +40 Kg N/ha (35 DAS) +40 Kg N/ha (at PI stage)

*120 Kg N/ha as a standard treatment; PI stage: panicle initiation stage

122

wetting and drying was given to this experiment and these sorts of input to the model gave the output like the dominance loss of N by nitrification and denitrification. When soil becomes water logged, O2 is excluded and anaerobic conditions occur as some anaerobic organisms obtain their O2 from NO2 and release of N2 and N2O. It was also reported that about 80% of the applied NO3- was lost in 72 hours due to denitrification (Devkota et al. 2008, Prasad and Lakhdive 1969). CONCLUSION To achieve the higher yield and quality in rice, the cultivation of newly developed hybrid varieties and scented varieties with optimum dose of nitrogen is crucial. Nitrogen is the major nutrient, limiting rice yields and its inefficient use has been reported in tropical and subtropical soils. Losses of N from leaching, volatilization and denitrification process vary in magnitude depending on the prevailing weather stage of crop growth, water and N management strategies. It is difficult or even inappropriate to recommend a single fertilizer strategy that is optimum in all season for the versatile nature of rice cultivars. There seems the immense scope of using CSM-CERES-Rice model as a tool for estimating potential yield, to verify the effects of different agronomic and climate change parameters and enhancing the resource use efficiency to the foot-hill basins and inner-terai of Central Nepal but CSM-CERES-Rice Model needs more rigorous studies with the complete data sets to suggest the appropriate mitigation and adaptive suggestions to the farmers in log-term and broad scale. REFERENCES Adhikari S, Basnet KB, Dahal KR, Chaudhary NK 2008. Performance of rice (Oryza sativa L.) under different combinations of mulching materials with LCC based nitrogen management in Chitwan. J Inst Agric Anim Sci 29:33-40 Aggarwal PK 2003. Impact of climate change on Indian agriculture. J Plant Biol 30: 189-98 Aggarwal PK 2008. Global climate change and India agriculture: impacts, adaptation and mitigation. Indian J Agric Sci 78 (10): 911-19 Amgain LP, Timsina J 2005. Major agronomical research work at the Institute of Agriculture and Animal Sciences, Rampur, Chitwan, Nepal: A Review. J Inst Agric Anim Sci 25:1-22 Amgain LP, Timsina J 2007. Simulation of yield, water and nitrogen balances in rice in Punjab, using CSM- CERESRice Model. J Inst Agric Anim Sci 28:15-26 Amgain LP, Devkota NR, Timsina J, Singh B 2006. Effect of climate change and CO2 concentration on growth and yield


of rice wheat in Punjab: Simulations using CSM-CERESRice and CSM-CERES-Wheat models. J Inst Agric Anim Sci 27:103-110. Asadi ME, Clement RS 2003. Evaluation of CERES-Maize of DSSAT model to simulate nitrate leaching, yield and soil moisture content under tropical conditions. J Food Agri Eng Res 1(3/4): 270-276. Bhusal TN, Amgain LP, Sah SK, Devkota NR 2008. Effect of weather years, CO2 and climate change on yield of open pollinated varieties of maize at Rampur, Chitwan. 5 th National Conference on Science and Technology, Nepal Academy of Science and Technology (NAST) (10-12 Nov, 2008), Kathmandu, Nepal. Chopra N, Chopra N 2000. Effect of row spacing and nitrogen level on growth, Yield and seed quality of scented rice (Oryza sativa) under transplanted conditions. Indian J Agron 45(2):304-308. Devkota K, Sah SK, Sah SC, Chaudhary NK 2008. Growth and productivity of hybrid and inbred rice varieties with different nitrogen management practices. J Inst Agric Anim Sci 29: 13-20. Fischer GM Shah, Velthuizen VH 2002. Climate change and agricultural vulnerability. International Institute for Applied Systems Analysis. Laxenburg, Austria. Gardner FP, Pearce RB, Mitchell RL 1985. Physiology of Crop Plants. (2nd eds) Iowa State University Press, Ames, IA. USA. Gometz K, Gometz AA 1984. Statistical Procedures for Agricultural Research. John Wiley and Sons Inc, UK. IPCC 2007. Climate Change 2007: Climate change impacts, adaptation and vulnerability. Summary for policymakers. Inter Governmental Panel on Climate Change. Jayawardena SN, Abesysekera SW 2002. Effect of plant spacing on the yield of hybrid rice. Annals Sri Lanka Dept Agri 4:15-20. Joshy KB 2001. Heterosis of yield and yield component of rice. Nepal Agric Res J 5:3-14. Long S P, Ainsworth EA, Leakey ADB, Morgan PB 2005. Global food insecurity. Treatment of major food crops with elevated carbon dioxide or ozone under large-scale fully open-air conditions suggests recent models may have overestimated future yields. Philosophical Translations of Royal Society B 360: 2011-20 MoAC 2004. Statistical information on Nepalese agriculture 2002/2003(2059/060). HMG, MOAC, Agri-Business Promotion and Statistics Division, Singh Durbar, Kathmandu, Nepal. MoAC 2008. Statistical information on Nepalese agriculture. Agribusiness Promotion and Statistics Division, Singh Darbar, Kathmandu, Nepal. Parry ML, Iglesias C, Livermore AM, Fischer G 2004. Effects of climate change on global food production under SRES emissions and socio-economic scenarios. Global Environmental Change 14: 53-67


123

Potential International Impacts. ASA Special Publication Number 59. ASA Madison, Wisconsin. pp 99-122.

Pathak H, Bhatia A, Prasad S, Singh S, Kumar S, Jain MC, Kumar U 2002. Emission of nitrous oxide from rice-wheat systems of indo-gangetic Plains of India. Environmental Monitoring Assessment 77:163-178

Singh U. Ritchie JT 1993. Simulating the impact of climate change on crop growth and nutrient dynamics using the model. J Agric Met 48:819-822.

Peng S, Huang J, Sheehy JE, Lazza RC, Visperas RM, Zhong X, Centeno CS, Khush G S, Cassman KG 2004. Rice yields decline with higher night temperature from global warming. Proc Natl Acad Sci 101 (27): 9971-75.

Timsina J, Humphreys E 2003. Performance and application of CERES and SWAGMAN destiny® models for ricewheat cropping systems of Asia and Australia- a review. CSIRO Land Water Technical Rep 16/03.

Prasad R, Lakhdive BA 1969. Nitrification of ammonia sulphate and subsequent losses of N under water logged condition as affected by nitrification inhibitor N-serve. Indian J Agric Sci 39:259-262.

Timsina J, Pathak H, Humphreys E, Godwin D, Singh B, Shukla AK, Singh U 2004. Evaluation of, and yield gap analysis in rice using, CERES Rice ver. 4.1 in northwest India. Abstract of the 4 th International Crop Science Congress, Brisbane, Australia, 26 Sept.-1 Oct. 2004. 170p.

Rao KS, Moorthy BTS 2002. Response of different rice (Oryza sativa) hybrids and varieties to graded level of nitrogen during wet and dry seasons in coastal Orissa. Indian J Agric Sci 72(9):508-513.

Verma AK, Pandey N, Tripathi S 2000. Effect of transplanting spacing and number of seedlings on productive tillers, spikelet sterility, grain yield, and harvest index of hybrid rice. Indira Gandhi Agricl Univ. India. IRRN 27(1):51.

Reddy TY, Reddi GH 2005. Principles of Agronomy. Kalyani Pub, Ludhiana, India. pp 54-326.

Virmani SS 1996. Hybrid rice. Adv Agron 57:377-462.

Salgotra RK, Katoch PC, Sood M 2002. Performance of rice hybrids for yield and quality traits under mid hill conditions of Himanchal Pradesh. SKUAST J 1:38-42.

Walker TW, Jason AB, Ottis BV, Patrick D, Dustin G, Harrell L 2008. Hybrid rice response to nitrogen fertilization for Midsouthern United States rice production. Agron J 100:381-386.

Sapkota A, Amgain LP, Devkota NR, Timsina J 2008. Evaluation of CSM-CERES-Maize model, estimation of potential yield and yield gap analysis of winter maize at Rampur, Chitwan. J Inst Agric Anim Sci 29: 27-32.

Yang X, Sun X 1990. Effect of NH4+-N and NO3- -N top dressing on the nutrition of hybrid and conventional rice varieties at late growth stage. Acta Agric Nucl Sin 4(2):75-79.

Singh A, Panwar DVS 1994. Hybrid rice: for sustainable rice production. Proceedings of symposium on sustainability of Rice Wheat System in India, 7-8 May 1994 at Regional Research Station, CCS Haryana Agricultural University, Karnal Haryana, India. pp 197-204.

Zhiqing J, Daokuo G, Chen H, Fang J 1994. Effects of climate change on rice production and strategiues for adaptation in southern China. In: Rosenzweig C, Igleasias A, (eds.) Implications of Climate Change for international Agriculture: Crop modeling study. US environmental Protection Agency, Washington DC. USA.

Singh U, Padila JL 1995. Simulating rice response to climate change. In: Climate Change and Agriculture: Analysis of

o