Produtividade de tubérculos e índices de nitrogênio em plantas de batata influenciados por fontes e doses de nitrogênio

• Autor(a) principal: Leão, Armindo Bezerra
• Data de Publicação: 2013
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1202
• topic: Solanum tuberosum; Adubação nitrogenada; Índices de nitrogênio; Solanum tuberosum; Nitrogen fertilization; Nitrogen Indexes; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOTECNIA

The objectives of the thesis were: a) to determine the effect of nitrogen (N) sources and rates on plant N evaluation indices determined in the fourth leaf and in the potato plant; b) on the potato tuber yield; c) to evaluate the N effect as urea on the morphophysiological potato plant characteristics; d) to characterize and to establish at an early potato plant stage indices to forecast tuber yield; e) to assess potato canopy spectral indices in response to different N sources and rates, selecting the most appropriate for estimating the plant N status and determining the critical level of the selected indices. Experiments were conducted with the potato cultivar Agata. The first followed a randomized complete block design in a factorial 5 x 3, consisting of three N sources (ammonium sulphate, urea and ammonium nitrate) and five N rates (0, 50, 100, 200 and 300 kg ha-1 ) with four replications. At 21 days after plant emergence (DAE) were determined the SPAD index, weight of fresh and dry weight and N content in the fourth leaf from the apex of the plants. Also it was evaluated in the plants: stem (length, number, fresh and dry matter and N content) and leaves (number, fresh and dry matter, N content). Later, at 90 DAE commercial potato tubers was evaluated. The second study was carried out using urea as N source in a randomized block design, five N rates (0, 50, 100, 200 and 300 ha-1), with four replications. Variables were determined in the fourth leaf at 21 DAE. These variables were leaf aspect by leaf image, leaf morphology (length, width, number of leaves), SPAD index, fresh and dry weight, N content besides tuber yield at the end of the crop cycle. The third study was based on the spectral data acquisition with the culture installed in the field, in the first experiment. Approximately 21 DAE, the appropriate time to decide on N sidedressing, 29 vegetation indices were obtained with the aid of spectroradiometry in the plant canopy. Measures were taken at 400 to 900 nm. From the 29 indices, five indices where selected based upon in the coefficient of determination (r2) of the linear relationship significance. After, they were estimated the coefficients of linear correlation (r) between each one of the five selected index with the variables determined both in the fourth leaf and in the final tuber harvest (SPAD index, leaf area, nitrogen content and commercial tuber yield). There was no interaction (N source and rates) effects on the variables. The effect of sources was only on the leaf area, dry matter and N content in the leaves. Significant N rate effect was observed on the leaf green intensity (SPAD), visual analysis (note) and plant indices (leaf area, length, leaflets number, masses of the fresh and dry matter). The commercial tuber yield showed a quadratic response to N rates, reaching maximum value of 47,920 and 58,300 kg ha-1 at 185.25 and 186.6 kg ha-1 of N, corresponding to the first and second experiment, respectively. Spectral analysis of the potato canopy demonstrated that in the visible region (400- 700 nm) the reflectance apparently followed the same trend for the N treatments, N rates and source, with the typical behavior of green vegetation. Conversely, the values of hyperspectral indices were influenced by N rates. NPCI MCARI (705, 750) and NVID1 indices obtained the highest degree of fit between the observed values of canopy reflectance and nitrogen rates. Regardless of the N source, the indices MCARI (705, 750) and NVID1 increased with increasing in the N rates and the opposite occurred with the NPCI index which decreased with the increasing in the N rates. There was significant correlation between the values of those indices with the values of the variables and the commercial tuber yield. NPCI index value considered critical or appropriate ranged from 0.28 to 0.29 and the index MCARI (705, 750) ranged from 127.0 to 128.0 and both indices are appropriate to evaluate the plant N status at the time to decide to make nitrogen side dress in the potato culture.