Camilo Busato

Carboidratos e matéria seca de tubérculos de cultivares de batata influenciados por doses de nitrogênio

Neste trabalho, objetivou-se avaliar o efeito de doses de nitrogenio (N) sobre os teores de carboidratos (acucares soluveis totais, acucares redutores e amido), materia seca e solidos soluveis totais nos tuberculos de quatro cultivares de batata. Os tuberculos originaram-se de quatro experimentos, realizados simultaneamente no campo, no outono/inverno, na Universidade Federal de Vicosa. Em todos os experimentos, foi utilizado delineamento em blocos casualizados, com quatro repeticoes. Os tratamentos foram compostos de cinco doses de N (0, 50, 100, 200 e 300 kg ha-1) na forma de sulfato de amonio, aplicadas no plantio das cultivares Agata, Asterix, Atlantic e Monalisa. Foram analisados os teores de materia seca, acucares soluveis totais, acucares redutores, amido e solidos soluveis totais nos tuberculos, apos 30 dias de armazenamento a 5oC a 80-85% de umidade relativa. Em todas as cultivares, as doses de N apresentaram efeito quadratico sobre o teor de solidos soluveis totais e nao houve efeito sobre os teores de materia seca e de amido nos tuberculos de batata. Dependendo da cultivar, as doses de N influenciam positivamente, ou nao influenciam os teores de acucares redutores e acucares soluveis totais nos tuberculos de batata.

SEASONAL VARIATION AND THRESHOLD VALUES FOR CHLOROPHYLL METER READINGS ON LEAVES OF POTATO CULTIVARS

Chlorophyll meter readings below a threshold value would indicate the necessity to supply nitrogen (N) to the crop. This study aimed to determine threshold values for chlorophyll meter (SPAD) and nitrogen (N) rate effects on SPAD leaf measurements of potato cultivars through the crop cycle. Five N rates (0, 50, 100, 200, and 300 kg ha−1) were evaluated in a randomized block design, with four repetitions. SPAD index was measured on the oldest (OL) and on the fourth leaf from the apex (FL) at 7, 14, 21, 28, 35, and 49 days after the emergence of 90% of the plants in the plots. SPAD values decreased with plant age and were influenced by N rates and leaf position. At 21 DAE, the SPAD threshold values on FL were 43.0, 44.6, 46.5, and 50.0 for ‘Agata’, ‘Monalisa’, ‘Atlantic’, and ‘Asterix’, respectively. The corresponding values were 41.9, 43.5, 49.9, and 49.9 on OL. Plant age and leaf position should be standardized for the assessment of SPAD threshold values to diagnose nitrogen status of potato cultivars.

Evaluation of the potato plant leaf area, cultivar Atlantic, using linear measures

The objective of this research was to establish the appropriated mathematical model to estimate leaf area of potato cultivar Atlantic using the linear dimensions of the leaf: the length (C) and width (L). The evaluation was performed in 270 leaves, which were randomly collected from a field of Universidade Federal de Vicosa, 21 and 50 days after the plant emergence (DAE). In laboratory, the length, width and area of each leaf were measured by a leaf area meter (model LI 3100). The data were submitted to a regression analysis with the AF value as a dependent variable and the leaf length, width, the product of both (CL), and the square product (CL)2 values as independent variables. Potato plant LA was more precisely estimated using measures of length and width: AF = 0,369335**CL + 10,6923 (R2 = 0,92) to 21 DAE and AF = 0,470971**CL - 16,3432 (R2 = 0,86) to 50 DAE. With the obtained model, AF of potato cultivar Atlantic can be estimated by measures obtained straight from the field, with no the need to damage the leaf or the plant.

Teor e exportação de macro e micronutrientes nos tubérculos de cultivares de batata em função do nitrogênio

The objective of this paper was to evaluate the effect of nitrogen (N) on concentration and accumulation of macro and micronutrients in tuber of the most widely planted potato cultivars in Brazil. The experiments were carried out during fall/winter season, in a typic Hapludult soil. Four experiments were simultaneously set in the field. In each experiment one potato cultivar, Agata, Asterix, Atlantic and Monalisa, and five N rates (0, 50, 100, 200, and 300 kg ha-1), as ammonium sulphate were evaluated. Each experiment was set in randomized complete block design with four repetitions. There was no effect of N rate on P, K, Ca, Mg, S, Fe and Zn concentration in potato cultivars Agata, Asterix, Atlantic and Monalisa. However, the total N concentration and total N, P and Mn accumulation in the tubers response were affected by N rates in all the cultivars, with different patterns.