Forms of application of nitrogen in different stages of the development of soybean culture / Formas da aplicação de nitrogênio em diferentes estádios do desenvolvimento da cultura da soja

In Brazil, inoculation with Bradyrhizobium japonicum and B. elkanii strains is the main form of Nitrogen (N) supply to soybean, but there are reports of the use of mineral N as a complement to biological fixation. The objective was to evaluate the effect of different forms and times of N application on the development and yield of soybean. The treatments include a control without N application and in all other treatments 10 kg ha-1 of N was applied, altering the time (V2, V4, R1 or R2) and the application form, namely, at sowing, broadcast on topdressing or by leaf spraying. The application of N provided an increase in leaf area, dry mass of shoot, number of nodules and dry mass of nodules in treatments with application of N at sowing and N at V2 on topdressing. For plant height, the treatment with N at V2 by leaf spraying was superior compared to control. The weight of one thousand seeds was not affected by N application. For grain yield the treatments with application of N by leaf spraying in V2 and R1 were highlighted. The greatest increase in grain yield on soybean is reached with leaf spraying at V2 stage

DÉFICIT HÍDRICO E A GERMINAÇÃO DE SEMENTES DE HÍBRIDOS DE MILHO

Considerando a importância da água no processo de germinação de sementes, as condições adversas de umidade afetam diretamente o processo germinativo. Para tanto, objetivou-se avaliar a influência do deficit hídrico na germinação e vigor de sementes de dois genótipos comerciais de milho, induzido por diferentes potenciais osmóticos. Utilizou-se delineamento experimental inteiramente casualizados (DIC), arranjado em esquema fatorial duplo 2x5, com quatro repetições, avaliando híbridos de milho (DKB255PRO3 e DKB390PRO2), submetidos a germinação sob condições de déficit hídrico, em cinco níveis de potencial osmótico (0, -0,6, -1,2, -1,8 e -2,4 MPa). Cada unidade experimental constituiu-se por um rolo de papel germitest contendo 50 sementes. Utilizou-se NaCl como agente osmótico indutor de deficiência hídrica as sementes. Avaliou-se a germinação, vigor de sementes e o desenvolvimento inicial das plântulas, em termos de comprimento e biomassa. O déficit hídrico, simulado com solução de cloreto de sódio, provoca redução no desempenho de sementes de híbridos de milho. Os genótipos de milho respondem diferentemente quanto a tolerância a condições de estresse provocado por indisponibilidade de água durante a germinação. O híbrido DKB390PRO2 apresenta germinação e crescimento de plântulas superior quando submetido a diferentes níveis de potencial osmótico de NaCl. Palavras-chave: viabilidade de sementes; restrição hídrica; Zea mays.   Effect of water deficit on the maize seed germination   ABSTRACT: Considering the importance of water in the seed germination process and knowing that conditions will not always be the most adequate to the germination process, the objective was to evaluate the influence of water deficit on germination and vigor in seeds of different commercial corn genotypes induced by different osmotic potentials. A completely randomized experimental design (D.I.C) was used, arranged in a 2x5 double factorial scheme, with four replications. Each experimental unit was constituted by a roll containing 50 seeds, made in germitest paper. Two maize seed hybrids (DKB255PRO3 and DKB390PRO2) were evaluated, submitted to germination under water deficit conditions, with levels 0; -0,6. -1,2; -1,8 and -2,4 MPa of osmotic potential. NaCl was used as osmotic agent inducing water deficiency in seeds. Germination, seed vigor and initial seedling development were evaluated in terms of length and biomass. The water deficit simulated with sodium chloride solution, causes a reduction in the performance of maize hybrids seeds. Corn genotypes respond differently to tolerance to stress conditions caused by unavailability of water during germination. The hybrid DKB390PRO2 presents superior germination and seedling growth when submitted to different levels of osmotic NaCl potential. Keywords: viability; water restriction; Zea mays