Full text
| |
| Author(s): |
Vanessa Zirondi Longhini
Total Authors: 1
|
| Document type: | Doctoral Thesis |
| Press: | Jaboticabal. 2020-07-14. |
| Institution: | Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal |
| Defense date: | 2020-03-30 |
| Advisor: | Ana Cláudia Ruggieri; Abmael da Silva Cardoso |
| Abstract | |
Legume inclusion in grass systems may reduce or replace the nitrogen fertilization, through the biological fixation of atmospheric nitrogen by the legume-bacterial symbiosis. Furthermore, improvement in animal nutrition can occur, decreasing the amount of nitrogen excreted into the environment via urine and dung. There have been few studies to quantify ammonia emissions from bovine excreta deposited in tropical pastures, and even fewer in warm-season grass-legume mixtures. Therefore, this thesis aimed to evaluate the use of forage peanut (Arachis pintoi Krapov. & W.C. Greg) mixed with palisadegrass [Urochloa brizantha (Hochst. ex A. Rich.) R. D. Webster cv. ‘Marandu’] as a strategy to replace nitrogen fertilizer in forage production systems. Three studies were performed. The first study evaluated herbage responses to N inputs and forage types during establishment under rotational stocking. Treatments included palisadegrass-forage peanut mixture, unfertilized palisadegrass, and palisadegrass fertilized with urea (150 kg N ha-1 yr-1). The second study evaluated how sward management strategies of palisadegrass pastures affected the litter deposition and decomposition rates, as well as litter chemical composition two years after seeding. The treatments were the same as those evaluated in the first study. In the third study, we conducted three field trials (wet, transition, and dry season) to quantify the ammonia (NH3) emissions, simulating application of heifer urine, dung, and urea fertilizer on warm-climate grasslands in Brazil. Heifer excreta were derived from the treatments of the first study, i.e. pastures of palisadegrass under three forms of N supply (0 or 150 kg N ha-1 or mixed with legume). Nitrogen fertilizer increased leaf mass (2470 kg DM ha-1) compared with the control and mixed treatments (1700 and 1310 kg DM ha-1, respectively). The percentage of N derived from atmosphere (%Ndfa) for forage peanut ranged from 79 to 85% and the biological N2 fixation (BNF) input ranged from 0.7 to 2.6 kg N ha-1 cycle-1. Nitrogen fertilization increased existing litter mass and litter deposition rate (2380 and 21 kg ha-1 OM, respectively) compared with grass in monoculture (1670 and 16 kg ha-1 OM, respectively) or legume-grass mixtures (1470 and 17 kg ha-1 OM, respectively); both variables were affected by weather conditions, with low litter deposition rate and low existing litter in the grazing cycles with poor rainfall (GC4). Nitrogen fertilized palisadegrass had greater litter N concentration (7.9 ± 0.4 g kg-1 OM) resulting in lower C:N ratio (34.0 ± 2.8) than in monoculture or legume-grass mixtures (44.1 and 57.7 ± 2.8, respectively). Nitrogen applied lost as NH3 emission across seasons ranged between 7.6 to 16.6% (mean 11.7%) for urine, 1.4 to 2.9% (mean 2.0%) for dung, and 11.2 to 20.5% (mean 14.8%) for urea, showing that NH3 emission from urine was significantly greater than from dung, for all seasons. Heifer excreta from grass-legume mixture had lower NH3 emission than excreta from the N fertilized pasture. Urea fertilizer broadcast on palisadegrass presented greater NH3 emissions in the wet season compared with the dry season but did not differ from the transition season. Overall, benefits from the forage peanut were minimal as legume percentage was ~10%. Nitrogen fertilization increased litter deposition rate as well existing litter mass and litter N concentration, whereas the low proportion of legume in the grass-legume mixtures was not enough to enhance litter nutrient cycling in the grassland ecosystem. Heifer excreta and urea fertilizer deposited on warm-climate grasslands increased the NH3 emission mainly in the wet season. (AU) | |
| FAPESP's process: | 16/11086-1 - Mitigation of greenhouse gases in pastures Marandu Grass managed with legumes or nitrogen fertilizer |
| Grantee: | Vanessa Zirondi Longhini |
| Support Opportunities: | Scholarships in Brazil - Doctorate |