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MAIZE NITROGEN RECOVERY FOR DIFFERENT APPLICATION LEVELS AND SPLITS OF NITROGEN FERTILIZER

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Author(s): FLÁVIA CARVALHO SILVA FERNANDES | PAULO LEONEL LIBARDI

Journal: Revista Brasileira de Milho e Sorgo
ISSN 1676-689X

Volume: 6;
Issue: 3;
Start page: 285;
Date: 2007;
Original page

Keywords: Zea mays L. | nitrogen | no tillage | residual effect

ABSTRACT
The objective of this work was to analyze the nitrogen recovery of maize crops growing in the soil under the no-tillage management system, using different levels and splits of N. The experiment was carried out in a sandy-loam soil, located in the ESALQ/USP campus and consisted of two maize croppings (2003/04 and 2004/05) and one black oat cropping grown in the interval between 2003/04 and 2004/05. The experimental design was randomized blocks with four replications, in an incomplete factorial (3x2) scheme + 1 (control: 0 kg ha-1 of N). Three levels (60, 120 and 180 kg ha-1) and two splits (30 or 60 kg ha-1 at sowing and the balance in cover) of N were used. The 15N-labelled fertilizer application, performed in order to use the isotope method, was carried out in the level of 120 kg ha-1 in subplots only in the first maize cropping. The following were evaluated: amount of N in plants, 15N abundance fertilizer recovering by plants of the three croppings using both methods of the difference and isotope. The nitrogen recovery, by the difference method, after all croppings of maize, did not decrease with the increase of the applied nitrogen level and, for the level of 120 and 180 kg ha-1 of N, the applications of 60 kg ha-1 at sowing showed the highest N recovery by the plants. For the level of 120 kg ha-1 of N, the plant N recovery (in percent) obtained by the method of the difference, after the first maize cropping, was 78,5% (in average) overestimated in comparison with the value found by the isotope method. The difference method should not be used in residual effect studies.
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