Inoculação com Azospirillum brasilense e Bacillus subtilis associada à adubação nitrogenada na nutrição, desenvolvimento e produção do capim Urochloa brizantha cv. Marandu
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Data
2020-08-18
Autores
Sampaio, Fernando Antônio Rebouças
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Universidade Estadual Paulista (Unesp)
Resumo
Bactérias dos gêneros Azospirillum e Bacillus são descritas como promotoras do crescimento de plantas e, quando associadas à adubação nitrogenada, podem reabilitar a capacidade produtiva das gramíneas forrageiras e auxiliar no processo de recuperação das pastagens degradadas. Sendo assim, este estudo teve como objetivo avaliar o efeito da inoculação com Azospirillum brasilense e Bacillus subtilis, de forma isolada e combinada, associada a níveis de adubação nitrogenada, no desenvolvimento, produção e qualidade nutricional de forragem do capim Urochloa brizantha cv. Marandu em quatro cortes. O experimento foi conduzido em casa de vegetação em delineamento inteiramente casualizado distribuído em esquema fatorial 4 x 5, com cinco repetições. O primeiro fator constituiu-se da inoculação das sementes de Urochloa brizantha cv. Marandu: sem inoculação, inoculação com estirpes de Azospirillum brasilense (Ab-V5, Ab-V6), inoculação com estirpe de Bacillus subtilis (CCTB04) e a coinoculação com as estirpes de A. brasilense e B. subtilis; o segundo fator correspondeu às doses de nitrogênio: 0, 25, 50, 75 e 100 mg dm-3 de N (equivalentes a 0, 50, 100, 150 e 200 kg ha-1 de N) aplicados na forma de ureia. Os vasos foram preenchidos com 15 dm3 de solo classificado como Argissolo Vermelho Amarelo distrófico proveniente de uma área com pastagem degradada. Em todos os vasos foram feitos a calagem e corrigidos os teores de fósforo, potássio e de micronutrientes. A inoculação for realizada na proporção de 1,0 mL 50 g-1 de sementes. Após cada corte da forrageira, foi realizada a reinoculação aplicando-se 5,0 mL planta-1 de solução bacteriana (1,0 mL de calda bacteriana por litro de água) e a reaplicação da adubação nitrogenada (0, 25, 50, 75 e 100 mg dm-3 de N) conforme os tratamentos supramencionados. As variáveis avaliadas foram: altura de planta (AP), número de perfilhos (NP) e de folhas (NF), diâmetro basal do colmo (DC), massa seca da parte aérea (MSPA), massa seca total (MST), proteína bruta (PB) e acúmulos de nitrogênio (N), fósforo (P) e potássio (K) na parte aérea ceifada do capim. Para todas as variáveis houve efeitos da interação da inoculação versus doses de nitrogênio, exceto para NP e NF no primeiro ciclo. De modo geral, as inoculações influenciaram a produção e qualidade do capim Marandu. Em todos os ciclos, na ausência da adubação nitrogenada, os tratamentos inoculados promoveram incrementos na AP, NP, DC, NF, MSPA, MST, PB e nos acúmulos de N, P e K, em comparação ao tratamento não inoculado. Independentemente do suprimento de nitrogênio, em pelo menos um dos ciclos de cultivo, os tratamentos inoculados proporcionaram acréscimos nas variáveis analisadas. Entre os tratamentos inoculados sobre o não inoculado, os melhores desempenhos (maiores incrementos mg dm-3 de N) no NP, NF e acúmulo de K foram obtidos com a inoculação isolada de B. subtilis, enquanto que a MSPA e o acúmulo de N foram mais influenciados com a inoculação isolada de A. brasilense, e por sua vez, a AP, DC, MST e acúmulo de P sobressaíram com a coinoculação. Os tratamentos inoculados reduziram os teores de PB em relação ao não inoculado, por efeito diluição na MSPA. Apesar de não ter sido regra, houve uma tendência de maior influência nas variáveis com a inoculação de A. brasilense associada à adubação até 50 mg dm-3 de N, enquanto a partir dessa dose, os melhores resultados foram obtidos com a inoculação de B. subtilis. Os resultados sugerem que a inoculação com A. brasilense e B. subtilis na forma isolada ou combinada, associadas ou não à adubação nitrogenada, apresentam potencial para incrementar a nutrição e o crescimento do capim Marandu, além de ser uma alternativa na recuperação das pastagens degradadas de forma sustentável e com menor consumo de nitrogênio e custos.
Bacteria of the genera Azospirillum and Bacillus are described as promoters of plant-growth and when associated with nitrogen fertilization, they can rehabilitate the productive capacity of forage grasses and assist in the recovery process of degraded pastures. Thus, this study aimed to evaluate the effect of inoculation with Azospirillum brasilense and Bacillus subtilis, in an isolated and combined forms, associated to nitrogen fertilization levels, on the development, production and nutritional quality of forage of Urochloa brizantha cv. Marandu in four cuts. The experiment was conducted in a greenhouse in a completely randomized design distributed in a factorial scheme 4 x 5, with five replications. The first factor was the inoculation of the U. brizantha cv. Marandu seeds: without inoculation, inoculation with Azospirillum brasilense strains (Ab-V5, Ab-V6), inoculation with Bacillus subtilis strain (CCTB04), and co-inoculation with A. brasilense and B. subtilis; the second factor corresponded to nitrogen doses: 0, 25, 50, 75 and 100 mg dm-3 of N (equivalent to 0, 50, 100, 150 and 200 kg ha-1 of N) applied in the form of urea. Experimental pots were filled with 15 dm3 of a Typic Hapludult soil from an area with degraded pasture. In all them, liming was done, and the phosphorus, potassium and micronutrients contents were corrected. Inoculation is performed in the proportion of 1,0 mL 50 g-1 of seeds. After each cut of the forage, re-inoculation was carried out by appling 5,0 mL plant-1 de bacterial solution (1,0 mL bacterial syrup per liter of water) and the reapplying nitrogen fertilization (0, 25, 50, 75 e 100 mg dm-3 of N) were performed according to the treatments aforenamed. The variables evaluated were: plant height (AP), number of tillers (NP) and leaves (NF), stem basal diameter (DC), shoot dry mass (MSPA), total dry mass (MST), crude protein (PB), and accumulations of nitrogen (N), phosphorus (P) and potassium (K) in the mowed shoot of the grass. For all variables there were effects of the interaction of inoculation versus nitrogen doses, except for NP and NF in the first cycle. In general, inoculations influenced the production and quality of Marandu grass. In all cycles, in the absence of nitrogen fertilization, the inoculated treatments promoted increases in AP, NP, DC, NF, MSPA, MST, PB and in the accumulations of N, P and K in shoot, compared to the non-inoculated treatment. Regardless of the nitrogen supply, in at least one of the cultivation cycles, the inoculated treatments provided increases in the analyzed variables. Among the inoculated treatments over the non-inoculated, the best performances (highest increments of mg dm-3 N) in NP, NF and K accumulation were obtained with the isolated inoculation of B. subtilis, while MSPA and N accumulation were more influenced by the isolated inoculation of A. brasilense; and in turn, AP, DC, MST and P accumulation stood out with co-inoculation. The inoculated treatments reduced the CP content in relation to the non-inoculated, due to the dilution effect on the MSPA. Although it was not a rule, there was a trend of greater influence on the variables with the inoculation of A. brasilense associated with fertilization up to 50 mg dm-3 of N; as from this dose, the best results were obtained with the inoculation of B. subtilis. The results suggest that inoculation with A. brasilense and B. subtilis, in isolated or combined form, associated or not with nitrogen fertilization, has the potential to increase the nutrition and growth of Marandu grass, besides being an alternative in the recovery of degraded pastures in a sustainable way and with less nitrogen consumption and costs.
Bacteria of the genera Azospirillum and Bacillus are described as promoters of plant-growth and when associated with nitrogen fertilization, they can rehabilitate the productive capacity of forage grasses and assist in the recovery process of degraded pastures. Thus, this study aimed to evaluate the effect of inoculation with Azospirillum brasilense and Bacillus subtilis, in an isolated and combined forms, associated to nitrogen fertilization levels, on the development, production and nutritional quality of forage of Urochloa brizantha cv. Marandu in four cuts. The experiment was conducted in a greenhouse in a completely randomized design distributed in a factorial scheme 4 x 5, with five replications. The first factor was the inoculation of the U. brizantha cv. Marandu seeds: without inoculation, inoculation with Azospirillum brasilense strains (Ab-V5, Ab-V6), inoculation with Bacillus subtilis strain (CCTB04), and co-inoculation with A. brasilense and B. subtilis; the second factor corresponded to nitrogen doses: 0, 25, 50, 75 and 100 mg dm-3 of N (equivalent to 0, 50, 100, 150 and 200 kg ha-1 of N) applied in the form of urea. Experimental pots were filled with 15 dm3 of a Typic Hapludult soil from an area with degraded pasture. In all them, liming was done, and the phosphorus, potassium and micronutrients contents were corrected. Inoculation is performed in the proportion of 1,0 mL 50 g-1 of seeds. After each cut of the forage, re-inoculation was carried out by appling 5,0 mL plant-1 de bacterial solution (1,0 mL bacterial syrup per liter of water) and the reapplying nitrogen fertilization (0, 25, 50, 75 e 100 mg dm-3 of N) were performed according to the treatments aforenamed. The variables evaluated were: plant height (AP), number of tillers (NP) and leaves (NF), stem basal diameter (DC), shoot dry mass (MSPA), total dry mass (MST), crude protein (PB), and accumulations of nitrogen (N), phosphorus (P) and potassium (K) in the mowed shoot of the grass. For all variables there were effects of the interaction of inoculation versus nitrogen doses, except for NP and NF in the first cycle. In general, inoculations influenced the production and quality of Marandu grass. In all cycles, in the absence of nitrogen fertilization, the inoculated treatments promoted increases in AP, NP, DC, NF, MSPA, MST, PB and in the accumulations of N, P and K in shoot, compared to the non-inoculated treatment. Regardless of the nitrogen supply, in at least one of the cultivation cycles, the inoculated treatments provided increases in the analyzed variables. Among the inoculated treatments over the non-inoculated, the best performances (highest increments of mg dm-3 N) in NP, NF and K accumulation were obtained with the isolated inoculation of B. subtilis, while MSPA and N accumulation were more influenced by the isolated inoculation of A. brasilense; and in turn, AP, DC, MST and P accumulation stood out with co-inoculation. The inoculated treatments reduced the CP content in relation to the non-inoculated, due to the dilution effect on the MSPA. Although it was not a rule, there was a trend of greater influence on the variables with the inoculation of A. brasilense associated with fertilization up to 50 mg dm-3 of N; as from this dose, the best results were obtained with the inoculation of B. subtilis. The results suggest that inoculation with A. brasilense and B. subtilis, in isolated or combined form, associated or not with nitrogen fertilization, has the potential to increase the nutrition and growth of Marandu grass, besides being an alternative in the recovery of degraded pastures in a sustainable way and with less nitrogen consumption and costs.
Descrição
Palavras-chave
Bactérias promotoras de crescimento de plantas, Brachiaria brizantha, Coinoculação, Fixação biológica de nitrogênio, Massa seca da parte aérea, Recuperação de pastagens degradadas, Plant growth promoting bacteria, Brachiaria brizantha, Co-Inoculation, Biological nitrogen fixation, Shoot dry mass, Recovery of degraded pastures