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| Author(s): |
Suzana Pereira de Melo
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2005-05-24 |
| Examining board members: |
Francisco Antonio Monteiro;
Gaspar Henrique Korndorfer;
Takashi Muraoka;
Carlos Guilherme Silveira Pedreira;
Elias Ayres Guidetti Zagatto
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| Advisor: | Francisco Antonio Monteiro |
| Abstract | |
One of the biggest problems for pasture establishment and maintenance in Brazilian soils is in the extremely low availability of phosphorus. Adding to this is the high soil adsorption capacity of this nutrient, as a consequence of high soil acidity and its high iron and aluminum concentrations. Silicate application can change phosphorus availability in the soil for the crops. The objective of this study was to evaluate the change in phosphorus availability, through the phosphate and silicate applications, for Marandu grass (Brachiaria brizantha cv. Marandu) establishment, by influencing the number of tillers, the leaf area, the roots growth and dry matter production of this forage. A fractionated 5x5 factorial was used, and the 13 combinations between silicon and phosphorus, in mg dm-3, respectively, were: 150 and 10; 150 and 170; 150 and 330; 225 and 90; 225 and 250; 300 and 10; 300 and 170; 300 and 330; 375 and 90; 375 and 250; 450 and 10; 450 and 170, and 450 and 330. The experimental units were set in randomized blocks design, with four replications. Among the chosen eight soils, physical, chemical and mineralogical analysis showed that the Typic Haplustox should be the most responsive for this study with the forage. The experiment was set in a greenhouse with this Oxisol. Wollastonite, which contains 243 g kg-1 silicon, was used as silicon source. Marandu grass was grown during the Summer season and two harvests were accomplished in the plants. Silicate and phosphate rates applied to the soil resulted in increases of soil pH, base saturation percentage, and silicon and phosphorus availability. Plant results showed significant interaction between phosphorus and silicon rates in dry matter production, number of both tillers and leaves, leaf area and phosphorus concentrations in the laminae of nature leaves, at the first and second harvests of Marandu grass. Phosphorus concentrations in the laminae of recently expanded leaves and in plant tops as average showed significant interaction between phosphorus and silicon rates, at the second harvest of the grass only. The average silicon concentration in plant tops was influenced by phosphorus and silicon combinations only at the first harvest of Marandu grass. The interaction between phosphorus and silicon rates was significant for phosphorus content in the grass in both harvests, whereas such interaction was only significant for the contents of silicon, potassium and sulphur in the first harvest. Histological studies made evident that silicon was deposited in cells epidermis of the Marandu grass leaf laminae. (AU) | |