Forrageiras e nitrogênio influenciando a dinâmica do fósforo em solo cultivado com milho

• Ano de defesa: 2019
• Autor(a) principal: Silva, Barbara Fernanda da
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Estadual Paulista (Unesp)
• Palavras-chave em Português: Zea mays. Braquiária. Hedley. dinâmica de P
• Link de acesso: http://hdl.handle.net/11449/190903

Phosphorus (P) is one of the nutrients that most limit agricultural production in tropical soils. It is found in inorganic forms (Pi) and organic (Po), with different weights in soil. Less labile forms of Pi and Po may contribute to plant nutrition, but it is necessary to be solubilized and mineralized, respectively. Coating plants contribute to the solubilization of less labile compounds, increasing the P content in the soil, but this solubilization does not always imply recycling and absorption by the plants. Two main hypotheses are raised: a) the roots of the plants cover organic acids capable of complex P through metal bridge, reducing the movement of P in the soil; b) the cover plants absorb soil P and, after decomposition, return it for the most part in the form of phytic acid, not available to the plants. Nitrogen fertilization may influence the mineralization of organic compounds in the soil, increasing the availability of P from the Po. Thus, two experiments were carried out, the first one evaluated the effect of the cover plants (U. ruziziensis, U. brizantha and P. maximum) and N nitrogen rates (70, 140 and 210 kg ha-1 ) in the soil Po dynamics, and its relation with P accumulation and yield by maize plants in two consecutive crops. The aiming of the second experiment was to evaluate the mobility of P in previously cultivated soil with cover crops under greenhouse conditions. The analyzed variables were fractions of Pi and Po in the soil; phytic acid content in soil and cover crops, and accumulation of P in the shoot of the maize plants. In the first experiment, It was verified that cultivation of U. ruziziensis as cover crop did not influenced the soil organic P dynamics. However, the nitrogen fertilization changed the soil organic P behavior. The accumulation of P in maize plants was influenced by nitrogen fertilization. In the second experiment, it was verified that in the sandy soils, P diffuses faster than in the clay soils, besides that the application of N improved the P mobility in both soils.