Banca de QUALIFICAÇÃO: ANDRÉIA TEIXEIRA DA SILVA

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : ANDRÉIA TEIXEIRA DA SILVA
DATE: 02/07/2024
TIME: 09:30
LOCAL: Sala de Aula da Pós-Graduaçao em Ciência Animal e Pastagens
TITLE:

Available Forms of Phosphorus and Management of Salinity in Salt-Affected Soils Cultivated with Forage Sorghum

KEY WORDS:

• Phosphorus fractionation,  Magnesium-induced salinity, Organic amendments

PAGES: 30
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Ciência do Solo
SPECIALTY: Fertilidade do Solo e Adubação
SUMMARY:

Soil fertility evaluation and salinity correction are essential for agricultural productivity, especially in arid and semi-arid regions. This study addresses soil salinity and phosphorus availability, offering a comprehensive view on managing fertility in salt-affected soils. Soil salinity is a growing issue, particularly in regions where evaporation exceeds precipitation, resulting in the accumulation of salts on the soil surface. This problem is exacerbated by improper irrigation and fertiliser management.

Saline and sodic soils are classified by electrical conductivity (EC) and exchangeable sodium percentage (ESP). However, high levels of magnesium (Mg) can also degrade soil structure similarly to sodium, due to Mg's higher hydration energy and radius. Magnesium-affected soils are identified by the percentage of magnesium saturation (PMS). Studies suggest that gypsum application can increase calcium (Ca) levels, improving soil structure. Organic residues, such as dairy sludge, humic substances, and biochar, have also shown effectiveness in mitigating salinity.

To assess magnesium-induced salinity, soils from regions with high Mg saturation or Ca/Mg ratio < 1 were selected. Soils were collected from three municipalities in the Agreste of Pernambuco and characterised according to EMBRAPA methods. Subsequently, a greenhouse experiment was conducted using an Eutrophic Solodic Planosol. The treatments applied were: agricultural gypsum, dairy sludge, commercial humate, sludge + gypsum, commercial humate + gypsum, biochar, and a control.

Managing fertility in saline soils involves detailed analysis of available phosphorus fractions. This study evaluated phosphorus availability in salt-affected Cambisols collected in Serra Talhada, Pernambuco, using a greenhouse experiment with increasing doses of phosphorus (0, 30, 60, 90, and 120 kg ha⁻¹ of P₂O₅) applied to soils cultivated with Sudan grass, a salt-tolerant crop. Sorghum was harvested at 50 days, and soil samples were collected to determine available phosphorus using various extractors (Mehlich-1, Olsen, Chang & Jackson, Saunder, Soltanpour, and "Pox") and inorganic phosphorus fractionation.

The studied soils exhibited pH ranging from 5.2 to 7.4, without high sodium saturation levels except at greater depths in the Vertisol. The Ca/Mg ratio was always less than 1, with high Mg saturation, indicating potential clay dispersion and aggregate formation. Available phosphorus was high in both surface and deeper horizons in some profiles. Total organic carbon (TOC) was low, particularly in surface horizons, and electrical conductivity (EC) ranged from 0.45 to 1.39 dS m⁻¹, indicating low salinity issues. Treatments with dairy sludge and gypsum showed better fresh and dry matter production, while commercial humate and biochar did not significantly differ from the control. The addition of Ca displaced Na and Mg in the solution, improving the Ca/Mg ratio. The application of gypsum and sludge effectively reduced sodium and magnesium saturation, enhancing soil structure.

The results indicate that phosphorus availability varied according to the extractor used. Phosphorus fractionation and extraction techniques are influenced by the specific characteristics of each soil, thus recommending against using a single technique for all conditions. Principal component analysis (PCA) showed that different extractors and phosphorus fractions influence nutrient availability to plants. Treatments with increasing phosphorus doses demonstrated that P application increased nutrient availability in the soil and uptake by Sudan grass, highlighting the importance of proper phosphorus management for crops in saline soils.

Integrated management of salinity and phosphorus availability, using techniques adapted to the specifics of each soil, is crucial for maintaining soil fertility and agricultural productivity in salt-affected regions. The application of gypsum and organic residues, such as dairy sludge, proved effective in improving soil structure and nutrient availability, while proper phosphorus management using multiple extractors is essential for ensuring efficient plant uptake.

COMMITTEE MEMBERS:
Presidente - ALEXANDRE TAVARES DA ROCHA
Externa ao Programa - ***.352.124-** - MARIA CAMILA DE BARROS SILVA - UFRPE
Externa à Instituição - RAYANNE THALITA DE ALMEIDA SOUZA