Fixação biológica de nitrogênio e recuperação de N-ureia em pastagem de 'Coastcross-1' tratada com Azospirillum brasilense

The objective of this work was to quantify the inoculation effect of Azospirillum brasilense (Ab-V5 and Ab-V6 strains) on the forage yield, biological nitrogen fixation (BNF), and urea-15N recovery of the forage grass 'Coastcross-1'. The experiment was carried out in a 2 (with or without inoculation) × 2 (without N fertilizer and with 100 kg ha-1 N per year as urea) × 7 (cuts) factorial arrangement. The natural 15N abundance method was used to determine BNF; to determine urea-N recovery, 15N-labeled urea was applied in microplots. Forage yield was higher in grasses subjected to inoculation, with 7.4 Mg ha-1 dry matter per year, for the treatment without N fertilizer, and 8.0 Mg ha-1 dry matter per year for the treatment with 100 kg ha-1 N per year, respectively, which shows an additive effect of inoculation and N fertilization. The contribution of BNF was 23.0 and 53.8 kg ha-1 per year for the unfertilized treatment, both in uninoculated and inoculated plants, respectively. Urea-15N recovery was 13.7 and 16.5 kg ha-1 per year for uninoculated and inoculated treatments, respectively, corresponding to 13.7 and 16.5% of the urea-N applied. Inoculation with A. brasilense increases forage yield and the contribution of BNF to grass nutrition with N, as well as urea-N recovery by the forage grass.O objetivo deste trabalho foi quantificar o efeito da inoculação de Azospirillum brasilense (estirpes Ab-V5 e Ab-V6) na produção de forragem, na fixação biológica de nitrogênio (FBN) e na recuperação de 15N-ureia pela gramínea forrageira 'Coastcross-1'. O experimento foi feito em arranjo fatorial 2 (com e sem inoculação) × 2 (sem fertilização nitrogenada e com 100 kg  ha-1 de N por ano, na forma de ureia) × 7 (cortes). O método da abundância natural de 15N foi utilizado para determinar a FBN; para a recuperação de N-ureia, aplicou-se 15N-ureia marcada em microparcelas. As produções de forragem foram maiores nas gramíneas com inoculação, com 7,4 Mg ha-1 de matéria seca por ano, no tratamento sem N fertilizante, e 8,0 Mg ha-1 de matéria seca por ano no tratamento com 100 kg ha-1 de N por ano, o que mostra o efeito aditivo da inoculação e da fertilização nitrogenada. A contribuição da FBN foi de 23,0 e 53,8 kg ha-1 por ano para o tratamento sem fertilização de N, tanto nas plantas sem inoculação como naquelas com inoculação, respectivamente. A recuperação de 15N-ureia foi de 13,7 e 16,5 kg ha-1 por ano, para os tratamentos sem e com inoculação, respectivamente, o que corresponde a 13,7 e 16,5% do N-ureia aplicado. A inoculação com A. brasilense aumenta a produção de forragem e a contribuição da FBN para a nutrição nitrogenada de 'Coastcross-1', assim como a recuperação de N-ureia pela gramínea

Forage mass and nutritive value of bermuda grass mixed to forage peanut or common vetch

ABSTRACT Three pasture-based systems (PS) with bermuda grass (BG) + forage peanut + 75 kg of N ha-1; BG + common vetch + 75 kg of N ha-1 and BG + 150 kg of N ha-1 were evaluated. Lactating Holstein cows were used for evaluation and the experimental design was completely randomized. Forage mass, botanical and structural composition, daily dry matter accumulation rate and stocking rate were evaluated. Samples were collected by hand-plucking method to analyze crude protein (CP), neutral detergent fiber (NDF), (ISDMD), in situ organic matter digestibility (ISOMD) and total digestible nutrients (TDN). Average forage production and stocking rate were 13.8; 15.3 and 16.1 t ha-1 and 5.6; 6.4 and 5.5 UA ha-1 day-1 for PS respectively. Average CP and NDF were 16.4; 22.2 and 15.3%; 68.3; 65.7 and 66.3%; for ISDMD, ISOMD and TDN were 68.5; 70.3 and 66.4%; 64.3; 63.2 and 65.3%; 57.3; 58.3 and 57.5%, for PS respectively. Best results were reported on bermuda grass mixed with common vetch

Forage production in mixed grazing systems of elephant grass with arrowleaf clover or forage peanut

ABSTRACT Most dairy production systems are pasture-based, usually consisting of sole grass species. This system facilitates pasture management, but results in high production costs, mainly because of nitrogen fertilizers. An alternative to making forage systems more sustainable is to introduce legumes into the pasture. Mixed pastures allow better forage distribution over time and reduce fertilization costs. Thus, the objective of this study was to evaluate, throughout the year, three forage systems (FS): FS1 (control) - elephant grass (EG), ryegrass (RG), and spontaneous species (SS); FS2 - EG + RG + SS + arrowleaf clover; and FS3 - EG + RG + SS + forage peanut. Elephant grass was planted in rows spaced 4 m apart. Ryegrass was sown between the EG lines, in the winter. Arrowleaf clover was sown according to the respective treatments and forage peanut was preserved. Evaluation was carried out using Holstein cows. The experiment was arranged in a completely randomized design, with three treatments (FS), and three repetitions (paddocks) with repeated measurements (grazing cycles). Forage mass achieved 3.46, 3.80, and 3.91 t ha-1 for the treatments FS1, FS2 and FS3, respectively. The forage systems intercropped with legumes produced the best results