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| Author(s): |
André Luis Tomazela
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2006-02-20 |
| Examining board members: |
Jose Laercio Favarin;
Durval Dourado Neto;
Hermann Paulo Hoffmann
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| Advisor: | Jose Laercio Favarin |
| Abstract | |
High doses of nitrogen may retard the maturation phase and enhance the risk of plant infection due to the longer exposition period in field and to the predominance of low molecular mass substances in the leaf tissue. The effect of cupper, to control pathogens is due to the lower requirements by microorganisms in relation to plants, as well to the accumulation of peroxides in the presence of this nutrient, reducing the activity of peroxidase e catalyses. The importance of manganese may be confirmed by the correlation between the concentrations of this element in health versus damaged tissues. The objectives of this study were: (i) to evaluate the yield of maize in relation to soil nitrogen and cupper and manganese foliar application; (ii) to estimate the disease occurrence and severity in relation to the nitrogen doses and cupper and manganese sources; and (iii) to establish management practices, based on micronutrients applications, aiming the reduction of pesticides use. The experiments had 12 treatments and four replications, in randomized block design, with two factorials. The first factorial (2 x 2) corresponded to the nitrogen doses (100 e 200 kg ha-1) and fungicide application (with or without fungicide), whereas the second factorial (2 x 2 x 2) was established with two nitrogen doses, two cupper sources (cupper sulfate and cupper hydroxides) and two manganese sources (manganese sulfate and chelates manganese). It was evaluated the plant height (m), stalk diameter (cm), leaf area index, total dry matter (g), and leaf disease occurrence (%), nutritional condition, total phenols content (%), spike length (cm), grain row number, number of grains per spike row, 100 grains mass (g) and grain yield (kg ha-1). The supply of 200 kg ha-1 N increased yield and infections by tropical rust (Physopella zeae), independently of the cupper and manganese sources used with the foliar applications. The cupper and manganese sources, as sulfate were more efficient for the suppression of plant infections by Physopella zeae then the hydroxide cupper and chelates manganese. The cupper and manganese micronutrients, at the studied dosage, did not replace the fungicide application for the infection control by tropical rust. The fungicide application did not eliminate the plant infections, even at the low severity of the disease (Physopella zeae), independently of the nitrogen dose. (AU) | |