Nitrogen is one of the most yield limiting nutrients in rice production under ali agro-ecological conditions. A greenhouse experiment was conducted to evaluate N responses to 12 lowland rice genotypes. Soil used in the experiment was an Inceptisol. The N rates used were Omg kg' (low) and 300 mg kq' (high) of soil. Straw yield, grain yield and panicle density were significantly increased with the addition of N fertilization and genotype treatment. The N X genotype interaction also was significant for these traits, indicating different responses of genotypes with variation in N rates

FAGERIA, N. K.

MORAES, L. A. C.

MOREIRA, A.

SANTOS, A. B.

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Lowland rice genotypes evaluation for nitrogen use efficiency in brazilian acid soil.

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8'" INTERNATIONAL SYMPOSIUM ON PLANT SOIL INTERACTIONS AT LOW pHFageria N.K.1, Santos A.B.1 and Moreira A.2 and Moraes L.A.C.2'National Rice and Bean Research Center of EMBRAPA,Caixa Postal 179, 5anto Antônio de Goiás, Go, CEP75375-000, Brazil'National Soybean Research Center of EMBRAPA,Caixa Postal 231, Londrina, PR,CEP86001-970, Brazil.Email: fageria@cnpf.embrapa.brLOWLAND RICE GENOTYPES EVALUATION FOR NITROGEN USE EFFICIENCY INBRAZILlAN ACID SOILAbstractNitrogen is one of the most yield limiting nutrients in rice production under ali agro-ecological conditions. A greenhouseexperiment was conducted to evaluate N responses to 12 lowland rice genotypes. Soil used in the experiment was anInceptisol. The N rates used were Omg kg' (low) and 300 mg kq' (high) of soil. Straw yield, grain yield and panicle densitywere significantly increased with the addition of N fertilization and genotype treatment. The N X genotype interaction alsowas significant for these traits, indicating different responses of genotypes with variation in N rates.294 Session V - Susta;nable Utilizat;on and Management of Agricultural and Natural Ecosystems ;n Acid SoilIntroductionRice is an important food crop for a large proportion of the world's population. Everyyear about 90 million people are addedto world population. This increase mostly occurs in developing countries. Hence, total rice production will need to increaseto feed an increasing world population. Rice is produced under both upland and lowland ecosystems with about 76% of theglobal rice produced from irrigated-Iowland rice systems (Fageria et aI. 2003). To improve rice yield, use of adequatetechnology is fundamental. Among the technologies which improves crop yields are use of adequate rate of fertilizers andcrop genotypes with high yield potential and higher nutrient use efficiency. Nitrogen is one of the most important nutrientsin improving crop yields, including rice under most agro ecosystems (Fageria and Baligar, 2001; Fageria, 2007). Under thesesituations, use of adequate rate, source and methods of N application along with efficient genotypes is an importantstrategy to reduce cost of production aswell as environmental pollution. The objective of this study was to evaluate lowlandrice genotypes for nitrogen use efficiencyMateriais and MethodsA greenhouse experiment was conducted at the National Rice and Bean ResearchCenter of EMBRAPA,Santo Antônio deGoiãs, Brazil to evaluate N use efficiency of lowland rice genotypes. The soil used in the experiment was an Inceptisol. Initialsoil properties (0-20 cm depth) were: pH 3.8 in water, Ca2.88 cmole kq', Mg 0.91 cmole kq', All.0 crnol kq', P46.8 mg kq', K50 mg kq', S 7.9 mg kq', Cu 7.4 mg kq:', Zn 1.6mg kq', B 1.5mg kq', Fe380 mg kq' and Mn 60 mg kq' and organic matter23 9 kq', Textural analysis showed 420 9 kg' clay, 200 9 kq silt and 380 9 kq' sand. The N rates used were Omg kq' (Iow)and 300 mg kg' of soil (high) and 12 lowland rice genotypes. These genotypes were advanced lines or cultivars frombreeding program of National Riceand BeanResearchCenter.A split-plot with sub-plot treatments arranged in a randornizedcomplete block design was used, with N rate in the main plots, and genotypes in the sub-plots. The treatments werereplicated three times. Basal fertilizer rate used were 200 mg P kq' applied with triple superphosphate and 200 mg K kqapplied with potassium chloride. Half of the N was applied at sowing and remaining half applied as topdressing at activetillering growth stage. Each pot also received 10 9 dolomitic lime. Lime was added 4 weeks before sowing and pots weresubjected to wet and dry cycling during 4 weeks period. After germination, thinning was done and four plants weremaintained in each pot. Pots were flooded with a water depth of about 3 to 4 cm two weeks after sowing and drained atharvest.Data were analyzed by analysis of variance, and treatment means were compared with Turkeys testoResults and DiscussionNitrogen X genotype interactions were significant for straw and grain yield and panicle density, indicating that somegenotypes were highly response to N fertilization while others were notoStraw yield varied from 14.129 plant' produced bygenotype BRA051108 to 20.31 9 plant' produced by genotype BRA051135, with an average value of 16.069 plant' at lowN rate. At high N rate, straw yield varied from 27.76 9 per plant produced by genotype BRA051250 to48.56 9 per pantproduced by genotype BRA051108, with an average value of 39.62 9 per plant. The increase in shoot dry weight with theaddition of 300 mg N kq' soil was 147% compared with Omg N kq: of soil. Fageria and Barbosa Filho (2001) reportedsignificant increase in shoot dry weight with the addition of 304 mg N kq' of soil compared to zero N application treatmentin Brazilian lowland soils. Shoot dry weight was having significant linear relationship with grain yield (Y= 8.5484 + 0.3005X,R2= 0.7298"). Fageriaand BarbosaFilho (2001) and Fageria (2007) reported significant association with shoot dry weight and8'" INTERNATIONAL SYMPOSIUM ON PLANT SOIL INTERACTIONS AT LOW pHgrain yield of lowland rice. Grain yield varied from 9.12 9 plant' produced by genotype BRA 051135 to 15.16 9 plant'produced by genotype BRSJaçanã, with an average value of 12.92 at low N rate. Similarly, at high N rate, grain yield variedfrom 17.05 9 plant' produced by genotype BRA051135 to 24.43 9 plant' produced by genotype BRSTropical., with anaveragevalue of 20.91 9 planr'. The increase in grain yield at high N rate was 62% compared with low N rate. Increase in grainyield of lowland rice with the addition of N fertilizer has been reported by Fageria and Barbosa Filho (2001), and Fageria etaI. (2003).Panicle density varied from 5.00 per plant produced by genotype BRA 051134 to 8.08 per plant produced bygenotype BRA051083, with an average value of 6.58 at low N rate. At high N rate, panicle density varied from 10.00 per plantproduced by genotypes BRA 051134 and BRA 051135, with an average value of 12.85 per plant. The increase in paniclenumber was almost double at high N rate compared with low N rate. Panicle number was significantly and linearly relatedwith grain yield (Y = 4.6694 + 1.2607X, R2= 0.9350"). Fageria and Barbosa Filho (2001) reported highly significant correlation(r = 96") between grain yield and panicle number in lowland rice grown in Brazilian Inceptisol.Table 1 :Strawyield (SY), grain yield (GY) and panicle density (PD) of 1210wland rice genotypes as influenced by N rate andgenotype treatments. Low N=Omg N kg" and high N 300 mg N kg" soilGenotype SY (g plant") GY (g plant") PD (plant")LowN High N LowN High N LowN High NBRSTropical 16.11 bcd 47.14a 12.53abc 24.43a 7.25abcd 15.00aBRSJaçanã 14.28d 34.28de 15.16a 20.47cd 7.08abcd 13.50abBRA02654 15.21cd 38.45cd 14.27ab 22.63ab 7.75ab 13.91abBRA 051077 14.66d 38.76cd 13.54abc 21.91 bc 6.33bcde 14.00abBRA 051083 14.44d 38.53cd 13.17abc 22.34bc 8.08a 14.33aBRA 051108 14.12d 48.56a 14.80ab 22.07bc 7.50abc 14.00abBRA051126 14.48d 41.91bc 12.45abc 19.61de 6.42bcde 12.48bcBRA 051129 18.65ab 32.35ef 11.09cd 18.10ef 5.25e 11.33cdBRA 051130 16.65bcd 45.68ab 13.00abc 22.37bc 5.83de 13.33abBRA0511344 18.08abc 40.69bc 12.28bc 18.02ef 5.00e 10.00dBRA 051135 20.31a 41.31bc 9.12d 17.05f 6.00cde 10.00dBRA 051250 15.68bcd 27.76f 13.61abc 21.91 bc 6.50abcde 12.25bcAverage 16.06b 39.62a 12.92b 20.91a 6.58b 12.85aF-TestN rate (N) ** ** **Genotype ** ** **(G)NXG ** ** **CV(%) N 7.49 4.23 7.28CV(O/O)G 4.95 4.91 5.84.. Significant at the 1% probability leveI. Means followed by the same letter in the same column are not significantly different at the 5%probability levei by the Turkeys testoReferencesFageria, N. K. 2007. Yield physiology of rice. J. Plant. Nutr. 30:843-879.Fageria, N. K., and V. C. Baligar. 2001. Lowland rice response to nitrogen fertilization. Commun. Soil Sei. Plant AnaI.32:1405-1429.Fageria,N. K.,and M. P.Barbosa Filho. 2001. Nitrogen use efficiency in lowland rice genotypes. Commun. Soil Sei. Plant Anal. 32:2079-2090.Fageria, N. K., N. A. Slaton, and V. C. Baligar. 2003. Nutrient management for improving lowland rice productivity and sustainability.Adv. Agron. 80:63-152.Session V - Sustainable Utilization and Management of Agricultural and Natural Ecosystems in Acid Soil 295

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Lowland rice genotypes evaluation for nitrogen use efficiency in brazilian acid soil.

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