Journal of Agricultural Science; Vol. 5, No. 3; 2013 ISSN 1916-9752 E-ISSN 1916-9760 Published by Canadian Center of Science and Education 243 Agronomic Performance of Soybean Genotypes in Low Latitude in Teresina-PI, Brazil Josynaria Araújo Neves 1 , José Algaci Lopes da Silva 2 , Douglas Rafael e Silva Barbosa 3 , Tuneo Sediyama 4 , Rita de Cássia Teixeira 4 & Renato Santos Rocha 4 1 Centro de Ciências Agrárias, Universidade Federal do Piauí, Campus Ministro Petrônio Portela, Bairro Ininga, CEP: 64049-550, Teresina, PI, Brasil 2 Departamento de Planejamento e Política Agrícola, CCA/Universidade Federal do Piauí, Teresina, PI, Brasil 3 Universidade Federal Rural de Pernambuco – UFRPE, Rua Dom Manoel de Medeiros, Brasil 4 Centro de Ciências Agrárias/DFT, Universidade Federal de Viçosa, Viçosa MG, Brasil Correspondence: Josynaria Araújo Neves, Centro de Ciências Agrárias, Universidade Federal do Piauí, Campus Ministro Petrônio Portela, Bairro Ininga, CEP: 64049-550, Teresina, PI, Brasil. E-mail: josynaria@hotmail.com Received: December 31, 2012 Accepted: January 31, 2013 Online Published: February 17, 2013 doi:10.5539/jas.v5n3p243 URL: http://dx.doi.org/10.5539/jas.v5n3p243 Abstract The soybean is one of the most important grain exports. In order to evaluate the agronomic traits and yield components of different soybean genotypes grown under low latitude conditions of Teresina-PI, developed in this research. It were evaluated the phenological and productive traits related to the development of soybean plants of 18 genotypes in the agricultural year 2009/10. Under the conditions studied, the genotypes showed significant differences for all traits analyzed, except plant height at maturity. Plant height at flowering, maturation and first pod showed variations from 42 to 57 cm, 42-63 cm and 6-11 cm, respectively. The genotypes 174 BCR1069X7RG and 169 BCR1069X7RG were considered the most precocious in flowering. In contrast, the genotypes 177 BCR1069X7RG and 176 BCR1069X7RG, with more than 57 days from germination to flowering, were considered the most late. In 1000 grain weight variation was from 15.02 to 20.72 g in values found. The genotypes showed satisfactory yield, especially 171 BCR1069X7RG (4.19 t ha -1 ) and 174 BCR1069X7RG (3.84 t ha -1 ) equivalent to 69.80 and 63.97 sacks of 60 kg, respectively. Overall, the genotypes showed good agronomic performance. Keywords: Glycine max (L.) Merrill, phenological observations, morphological observations, soybean, seed yield 1. Introduction The soybean [Glycine max (L.) Merrill] is a species of great economic importance, due to the formation of the complex structure of production, storage, processing and marketing in all countries where it is cultivated. The great demand in international markets provided rapid expansion of this crop in Brazil (Rezende & Carvalho, 2007). The Brazilian soybean production in 2009/10 crop, according to Companhia Nacional de Abastecimento (2010) was 65.16 million tons, representing an increase of 14% (8.0 million tons) compared to 2008/09 crop. The high soybean production in Brazil is due to the changes the country underwent in the last 32 years, with increases of 333% in planted area and 1,536 times in the production, which resulted in greater use of agricultural inputs, encouraging the use of application technologies for this crop (Farinha, Martins, Costa, & Domingos, 2009). Also the appearance, selection and recommendation of soybean cultivars adapted to low latitudes, basic objectives of genetic improvement programs, as promoted the use of unexplored areas of the Cerrado (Lima et al., 2008). Although the present Cerrado soils with low fertility chemistry, topography and weather are highly suitable for cultivation (Oliveira Júnior, Prochnow, & Klepker, 2008). To have successful in soybean crop is necessary to meet their nutritional requirements and water, and using cultivars with high yield, resistant to lodging, pests and diseases and adapted to different environmental conditions. However, soybean is manifested differently when subjected to different climatic conditions, and its production cycle changed as a function of air temperature and photoperiod (Rezende & Carvalho, 2007).