Banca de DEFESA: LILIAN HORANNA ALVES DA SILVA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : LILIAN HORANNA ALVES DA SILVA
DATE: 03/03/2026
TIME: 08:00
LOCAL: Auditório do PPG Ciência do Solo
TITLE:

Photosynthetic efficiency, oxidative stress, and sugarcane nutrition in relation to iron and manganese availability in sandy soils of the coastal plateau.

KEY WORDS:

Chlorosis. Micronutrients. Coastal Tablelands. Oxidative Stress.

PAGES: 85
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Ciência do Solo
SPECIALTY: Fertilidade do Solo e Adubação
SUMMARY:

In the Northeast of Brazil, the coastal plateaus stand out as an important agricultural hub, especially in the cultivation of sugarcane. In this geological formation, crops are established on predominantly sandy and dystrophic soils, which may have hardened horizons at different depths. These horizons influence water percolation, favoring periods of saturation and altering the soil's redox conditions, which directly affects the availability of nutrients such as iron (Fe) and manganese (Mn). During dry periods, crops grown in this region are more susceptible to deficiencies of these micronutrients due to their lower mobility and availability in the soil. Conversely, during the rainy season, the presence of hardened and dark horizons (Bh) can promote temporary soil saturation and increase the availability of Fe and Mn, especially under reducing conditions. Sugarcane grown in this edaphic environment often exhibits symptoms such as leaf chlorosis characteristic of iron deficiency and longitudinal streaks associated with manganese deficiency, the manifestations of which may vary throughout the growth cycle. In this context, the objective of this research is to evaluate doses of Fe and Mn in different redox environments, influenced by the rainfall water regime, and their effects on the nutrition, photosynthetic pigments, biochemistry, and productivity of sugarcane grown in the sandy soils of the coastal plateaus of the Northeast. The experiment was conducted on sandy soil classified as Hydromorphic Spodosol, in a commercial area belonging to Usina Japungu, located in the municipality of Santa Rita–PB, cultivated with sugarcane, in the fourth ratoon cycle of the RB92579 variety. The treatments were arranged in a randomized block design, with three blocks, using a factorial scheme (6 x 2) + 1. There were 6 doses of Fe (1.5; 3.0; 6.0; 9.0; 12.0; and 15.0 kg ha-1), using FeSO4 as the source, 2 doses of Mn (1.5 and 3.0 kg ha-1), using MnCO3 as the source, plus a control treatment that did not receive any micronutrient application. Evaluations were carried out at three points corresponding to rainfall variation in the region, identified as the rainy period (May/June/25), the beginning of the dry season (August/September/25), and the peak of the dry season (November/December/25). In the plants, chlorophyll fluorescence and photosynthetic pigments were analyzed to assess photosynthetic efficiency, as well as electrolyte leakage to evaluate the plant's antioxidant response. At the end of the cycle, the plant's response to the treatments was evaluated through growth biometrics and quantification of agro-industrial productivity. In all three evaluation periods, the addition of Fe and Mn promoted an increase in the production of photosynthetic pigments. Chlorophyll fluorescence, in turn, was negatively affected during the period of highest rainfall, with the highest doses showing a possible toxic effect of these micronutrients. Plants subjected to the lowest doses of Fe and Mn showed a reduction in electrolyte leakage, indicating less damage to cell membranes. Despite the beneficial effects observed on photosynthetic efficiency and the mitigation of oxidative stress, the vegetative growth and productivity of sugarcane were not significantly influenced by the application of Fe and Mn to the soil. However, 1:1 or 2:1 type relationships proved to be more promising, as they provided improvements in the plant's photosynthetic and antioxidant dynamics with lower input requirements, without compromising productivity.

COMMITTEE MEMBERS:
Presidente - EMIDIO CANTIDIO ALMEIDA DE OLIVEIRA
Interno - MARIO DE ANDRADE LIRA JUNIOR
Externo ao Programa - 2114713 - ALEXANDRE CAMPELO DE OLIVEIRA - UFRPE