Adubação nitrogenada do feijoeiro, em plantio e cobertura, em plantio direto e convencional

Abstract

RESUMOCom o objetivo de avaliar, a campo, a resposta do feijoeiro a doses de nitrogênio por ocasião da semeadura e em cobertura, foram conduzidos dois experimentos (plantio direto e convencional), na safra das águas 2004/05. O delineamento estatístico foi em blocos casualizados com três repetições e esquema fatorial 4x4, envolvendo 4 doses de N no plantio (0, 40, 80 e 120 kg.ha -1 ) e 4 doses de N em cobertura (0, 40, 80 e 120 kg.ha -1 ), aos 20 DAE. Cada parcela foi constituída por quatro linhas de 5 m de comprimento, espaçamento de 0,5 m e densidade de 16 sementes.m -1 . Foram avaliados os estandes inicial e final e o rendimento de grãos. Em ambos os sistemas de plantio, o incremento do fertilizante nitrogenado de plantio reduziu o estande de plantas. De maneira geral, no plantio direto, a resposta à aplicação de N no plantio foi quadrática e a dose correspondente à máxima produtividade variou com as doses de cobertura. No plantio convencional, essa resposta foi linear decrescente, em razão do maior efeito de N de plantio sobre o estande. A resposta à aplicação de N em cobertura foi quadrática, em ambos os sistemas de plantio e as maiores respostas do rendimento de grãos foram observadas com o emprego da dose de 40 kg.ha -1 de N no plantio.Termos para indexação: Nitrogênio, Phaseolus vulgaris, sistemas de plantio. ABSTRACTWith the aim of evaluating the responses of bean to nitrogen fertilization rates at sowing and topdressing in the field, two experiments were carried out (no-tillage and conventional tillage), in the rainy season 2004/2005. The experimental design was in randomized blocks with three replicates in a 4x4 factorial structure encompassing four N rates at sowing (0, 40, 80, and 120 kg.ha -1 ) and four topdressing N rates (0, 40, 80, and 120 kg.ha -1 ) at 20 DAE. Each plot was composed of four 5-m-long rows, 0.5 m apart from each other and a 16 seed.m -1 density was used. Initial and final stand and grain yield were assessed. In both crop management systems, the increasing nitrogen fertilization rate at sowing reduced the plant stand. In general, in no-tillage the response to N application at sowing was squared and the rate corresponding to maximum yield varied depending on the topdressing rates. In conventional tillage this response decreased linearly, as a function of the higher effect of N at sowing on final stand. The response to N topdressing application was squared in both crop management systems and higher responses to grain yield were observed with 40 kg.ha -1 N rate at sowing.

<b>Nitrogen and molybdenum fertilization and inoculation of common bean with <i>Rhizobium</i> spp. in two oxisols

“…This fact is likely attributed to the salt effect of urea, given that the irrigation was less uniform in the initial phase of the experiment in Pitangui. The salt effect of N fertilization at planting has been frequently reported in the literature to result in decreases in germination, emergence, and dry matter accumulation in common bean plants (Kikuti et al, 2005;Alves Júnior et al, 2009).…”

“…In Pitangui, where the stand was already low, this effect was not significant, and other factors, such as the lack of uniformity of the initial water application, may have had an effect on this variable As observed for the other traits, yield was not affected by seed inoculation (Figure 1F), although it was influenced by the main effects of N ( Figure 1H) and Mo, with the latter dependent on the location, as evidenced by means for the L x Mo interaction ( Figure 2C at planting produced lower grain yields (16% lower than the treatment without N; Figure 1H). This result can be explained by the reduction in the final plant population attributed to the effect of salt stress (Kikuti et al, 2005;Alves Júnior et al, 2009) and consequent decrease in grain production per area.…”

“…However, applications of high doses of N, especially at planting, negatively affect nodulation and BNF (Soares et al, 2006;Souza, Soratto, & Pagani, 2011), and may also affect the germination and the emergence of common bean (Kikuti, Andrade, Carvalho, & Morais, 2005; Alves Júnior, Andrade, Carvalho, Vieira, & Morais, 2009). For the state of Minas Gerais, under field conditions, it has not been yet established a safe N dose in the planting furrow that does not reduce nodulation and BNF, and not have the salt effect of nitrogen fertilizer.…”

Age of No‐Till System and Nitrogen Management on Common Bean Nutrition and Yield

“…In this system, the accumulation of crop residues on the soil surface favors the recycling of nutrients, soil aggregation, water storage, and the maintenance of soil organic matter (SOM) and has positive eff ects on fertility (Hunt et al, 1996;Sá, 1999;Triplett and Dick, 2008;Crusciol and Soratto, 2010;Watts et al, 2010;Kumar et al, 2012). Nevertheless, the mineralization rate of SOM is lower than that of conventional tillage (CT) systems (Amado and Mielniczuk, 2000), which provide reduced N availability to plants, especially during the period from system implementation to equilibrium (Sá, 1999;Soratto et al, 2001;Figueiredo et al, 2007;Alves et al, 2009). A number of years aft er adopting a NT system an equilibrium between the amounts of immobilized and mineralized N in the soil is reached.…”

“…In addition, Franco et al (2008) found that the application of 100 kg ha -1 N at sowing led to a common bean seed yield similar to that of a split application of fertilizer, indicating that supplying N during the initial stages of development may promote a greater initial growth of common bean under the NT system. However, high rates of N application in the sowing furrow very close to seeds may compromise the establishment of common bean plants (Teixeira et al, 2005;Alves et al, 2009) and may reduce initial nodulation and N 2 fixation (Tsai et al, 1993). Therefore, it is necessary to determine the optimal manner in which to supply N to common bean in fields that have been under an NT system for different durations with the goal of decreasing the use of N fertilizers and increasing the yield of this crop.…”