Banca de QUALIFICAÇÃO: JOÃO VICTOR COSTA DE OLIVEIRA

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : JOÃO VICTOR COSTA DE OLIVEIRA
DATE: 25/02/2025
TIME: 13:00
LOCAL: Sala meet.google
TITLE:

Dynamics of soil carbon and nitrogen stocks in farming systems in Amazonia and Caatinga

KEY WORDS:

Amazon; semi-arid; land use change; climate change; forage

PAGES: 40
BIG AREA: Ciências Agrárias
AREA: Zootecnia
SUBÁREA: Pastagem e Forragicultura
SPECIALTY: Fisiologia de Plantas Forrageiras
SUMMARY:

Changes in land use have an impact on the soil's organic carbon (C) and nitrogen (N) pools, resulting in the release of these elements in the form of greenhouse gases. The aim of the first trial was to evaluate the stock of C and N in the soil and the fractions of organic matter in different woody proportions of an integrated system in the Caatinga. The second trial aimed to assess the stock of C and N in the soil and organic matter fractions in different land use systems in the Amazon biome. The experiment in the first trial was conducted in Pentecoste, CE. A randomized block design was used in a factorial arrangement (3×3+1), with the first factor being represented by the agricultural systems used in the areas (massai grass, millet or paiaguás grass + guandú beans). The second factor is represented by the proportion of wood that makes up the systems: 45; 30 or 15%. As an additional factor, an area of secondary Caatinga vegetation was evaluated as a reference in relation to the other systems. The second trial was conducted in the municipality of Moju, PA. The experiment consisted of three different land use systems: native forest (with no history of felling, only selective suppression of hardwood); Urochloa humidicola cv. Quicuio pasture managed with fire for 30 years and newly established Megathyrsus maximus cv. BRS Zuri pasture with four replications per system, represented by the trenches (4 trenches per system). Samples were collected at the following depths: 0 - 5; 5 - 10; 10 - 20; 20 - 30; 30 - 40; 40 - 60; 60 - 80 and 80 - 100 cm. The data for each variable was submitted to analysis of the normality of the residuals using the Cramer-von-mises test. When ANOVA was significant for the land use levels, a comparison of means (p<0.05) (SNK) was carried out using the R software. In the first trial, in the 0-5 cm layer, massai and paiaguás in the 30% proportion had the highest C stock values (Mg C ha-1) (8.47 and 8.51). In the 5-10 cm layer, only the paiaguás grass in the 30% ratio had the highest (6.35) C stock. In the 10-20 and 20-30 cm depths, massai and paiaguás in the 15% ratio had the highest (6.82 and 5.56) C stock. In the second trial, there was a difference (P<0.05) in soil density (g. cm-3) in the surface layers 0-5, 5-10 and 10-20 cm, the quicuio area showed greater density (1.40; 1.47; and 1.49) than the zuri (1.17; 1.41 and 1.41), while the forest did not differ (1.25; 1.45 and 1.45) from the respective areas. There was no difference (P>0.05) in the stock of C. In the stock of N (Mg N ha-1), at a depth of 0-30 cm, the zuri area (4.10 ± 0.10) stored more N than the quicuio (3.65 ± 0.11) and the forest (3.66 ± 0.20). At a depth of 0-100 cm, the forest and the quicuio showed no difference, with the zuri area (7.54 ± 0.82) having the highest N stock. The massai and paiaguás grasses manipulated in the proportion of 30% woody cover maintain the contribution of C to the soil. Newly converted areas, when managed rationally, preserve soil C and N stocks. Different crops and woody proportions influence soil C and N dynamics in the Caatinga biome. Well-formed pastures in the Amazon biome can preserve soil C and N stocks.

COMMITTEE MEMBERS:
Presidente - ***.634.163-** - ANIBAL COUTINHO DO REGO - UFC
Interno - 1331235 - THIAGO CARVALHO DA SILVA
Externo à Instituição - GABRIEL NUTO NÓBREGA - UFC
Externo à Instituição - MAURICIO ROBERTO CHERUBIN - ESALQ
Externo à Instituição - JORGE CARDOSO DE AZEVEDO - UFRA