Paulo Cezar Rezende Fontes

Critical chlorophyll, total nitrogen, and nitrate‐nitrogen in leaves associated to maximum lettuce yield

Abstract An experiment was conducted to establish chlorophyll, nitrate‐nitrogen (NO3‐N), and total nitrogen (N) critical concentrations in lettuce (Lactuca sativa) leaves that are associated with maximum dry matter yield. Six N levels (0, 60, 120, 240, 480, and 960 mg.kg‐1 soil) as ammonium nitrate (NH4NO3) were applied in a randomized block design with four replications. Two wrapper leaves were collected at the eighth‐leaf stage and analyzed for their chlorophyll a+b and total N contents. Forty‐five days after transplanting, plants were harvested, dried, and analyzed for their NO3‐N and total N contents. Critical levels associated with maximum lettuce yield at the eighth‐leaf stage were: 1,837 mg chlorophyll kg‐1 fresh weight and 4.27 g N 100 g‐1 dry matter, and at harvest: 6,361 mg NO3‐N kg‐1 dry weight and 3.75 g N 100 g‐1 dry matter. In the soil, N levels associated to maximum plant dry weight were 34 mg NO3 ‐N kg‐1 and 390 mg N kg‐1.

Fruit size, mineral composition and quality of trickle-irrigated tomatoes as affected by potassium rates

Para determinar o efeito da fertirrigacao com K sobre o tamanho, a composicao mineral e a qualidade dos frutos do tomateiro, foi conduzido um experimento com aplicacao de seis doses de K, na forma de KCl, correspondendo a 0, 48,4, 118,6, 188,8, 259,0 e 399,4 kg ha-1, com quatro repeticoes, distribuidas no delineamento experimental em blocos casualizados. Foram observadas respostas quadraticas das producoes das classes de frutos graudo 2 (diâmetro > 60 mm), graudo 1 (56 a 60 mm) e graudo (52 a 56 mm) em relacao as doses de K aplicadas na adubacao. As producoes maximas de frutos de cada classe foram obtidas com as doses de K de 116, 190 e 233 kg ha-1, respectivamente. O conteudo de materia seca e os teores de P, S e Mg dos frutos nao foram influenciados pelas doses de K, mas os teores de nitrato e de potassio aumentaram com o aumento das doses. Os teores de vitamina C, solidos soluveis, licopeno e b-caroteno nao foram influenciados pelas doses de K; porem, os incrementos nas doses reduziram o pH e aumentaram o conteudo de acidos nos frutos.

Qualidade do fruto de melão rendilhado em função de doses de nitrogênio

ABSTRACT MUSKMELON FRUIT QUALITY AS AFFECTED BY NITROGEN RATES Two experiments with melon plants ( Cucumis melo L.) Cantalupensis Group were carried out inthe summer, in the field and in an unheated greenhouse, aiming to evaluate the effect of nitrogen rateson fruit physical (weight, diameter, flesh pulp thickness, and cavity diameter) and chemical (total solublesolids, titratable acidity, and pH) characteristics. Each experiment consisted of four randomized blockscontaining five nitrogen rates (0, 75, 150, 300, and 450 kg.ha -1 ). The nitrogen, applied as urea, had 30%placed in furrows before seedlings transplantation, and the remaining 70% of each N rate were trickle-applied throughout the plant cycle. In both greenhouse and field, the increase in N applied increasedfruit physical characteristic values. In the greenhouse, with the N rate of 312 kg.ha -1 , that gave themaximum commercial yield (MCY), fruit fresh weight, diameter, flesh thickness and cavity diameterwere, respectively, 1.280 g, 12.6 cm, 3.1 cm and 6.1 cm. In the field, with 344 kg ha

Color evaluation of carbon monoxide treated porcine blood

The stability of liquid porcine blood, treated with carbon monoxide (CO) at different pH values (7.40, 6.70, and 6.00) up to its complete saturation, was studied. Lowering the pH from 7.40 to 6.70 resulted in a decrease in the amount of CO necessary to obtain 100% carboxyhemoglobin. Further pH lowering to 6.00 did not result in additional reduction in the amount of gas. During 4 days of refrigerated storage CO treated liquid blood maintained, at every pH, a more stable and attractive red color than fresh blood, which was a result of an increase (P<0.05) of a(*) (redness) and b(*) (yellowness) values and no variation (P>0.05) on L(*) (lightness) value. Hue (h(*)) and chroma (C(*)) decreased in the untreated blood but not in the CO-treated blood. The results indicate that blood saturation with CO yields a product having greater potential for use in meat products without compromising its visual appearance.

Composition and color stability of carbon monoxide treated dried porcine blood

Color stability of swine blood was studied over 12 weeks of storage in plastic bags, after pH (7.40, 6.70, or 6.00) adjustment, saturation with carbon monoxide (CO) and spray-drying. CO-treated dried blood presented a redder color and higher reflectance between 610 and 700 nm, compared to a brownish-red color and lower reflectance of untreated samples. As indicated by reflectance spectra, blood pH adjustment did not influence (P>0.05) the initial color of dried blood but influenced (P<0.05) its color stability (browning index). During storage, CO-treated blood showed a reduction in reflectance percentages as well as in CIE L(*) and a(*) values, which was more pronounced in polyethylene (OTR=4130 cm(3)/m(2)/day/atm) packaged samples. After 12 weeks of storage, CO-treated samples packaged in high OTR bags presented color indexes similar to those of the untreated dried samples. CO-treated samples packaged in nylon-polyethylene (OTR=30-60 cm(3)/m(2)/day/atm) bags showed a smaller rate of discoloration and color difference (DeltaE(*)) between the CO-treated and untreated samples. Even with some darkening, packaging CO-treated dry blood in low OTR bags still gives an acceptable reddish color after 12 weeks of storage while untreated dry blood has a brownish color just after drying.

Effect of Nitrogen and Trinexapac-Ethyl Rates on the SPAD Index of Wheat Leaves

ABSTRACT The objective of this study was to evaluate the effect of nitrogen (N) and trinexapac-ethyl (TE) rates on the SPAD index in wheat flag leaf. The treatments were five N rates (30, 60, 90, 120, 150 kg ha−1) combined with four TE rates (0, 63, 125, 188 g ha−1). The experiment was carried out in a randomized block design with four repetitions. SPAD index, leaf N content and grain yield showed quadratic response to the increase in N rates, whereas area, wet and dry weight of flag leaf presented linear increase. TE caused linear increase in SPAD index, linear decrease in leaf area, reduction in grain yield with smaller N rates and increase with larger N rates. The N content, and the wet and dry weight of flag leaf were not affected by TE. SPAD calibration to estimate N status in wheat should be specific for each TE rate.

Potato plant growth and macronutrient uptake as affected by soil tillage and irrigation systems

The objective of this study was to evaluate potato plant growth and macronutrient uptake, as affected by soil tillage methods, in sprinkle and drip irrigated experiments. Eight treatments were set: T1, no tillage, except for furrowing before planting; T2, one subsoiling (SS); T3, twice rotary hoeing (RH); T4, one disc plowing (DP) + twice disc harrow leveling (DL); T5, 1DP + 2DL + 1RH; T6, 1DP + 2DL + 2RH; T7, 1SS + T6; T8, one moldboard plowing (MP) + 2DL. Treatments were arranged in a randomized block design with four replications. In both irrigation systems, plants presented higher emergence velocity index (EVI), when the soil was not tillaged, and the EVI was inversely related to the maximum tuber dry mass production. In both experiments, a functional direct relationship was found between the leaf area index and maximum tuber dry mass yield. The growth of plant organs (tuber, leaf, stem and root) and the macronutrient (N, P, K, Ca and Mg) contents in potato plant responded positively to a deeper soil revolving caused by plowing, especially with moldboard plow.

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.

Critical phosphorus concentrations in potato plant parts at two growth stages

Abstract Adequately evaluating the phosphorus (P) nutritional status of a potato crop is dependent upon sampling the appropriate plant part at a defined growth stage. To establish P critical concentration levels in various potato plant parts (leaves, stems, tubers, leaflets, and petioles) at two growth stages [20 and 50 days after plant emergence (DAE)], an experiment under Brazilian climatic and soil conditions was conducted using seven P treatment levels (0, 40, 80, 160, 320, 640, and 1,280 kg P2O5 ha‐1) applied in a randomized complete block design with four replications. ‘Baraka’ potato tubers were seeded at a spacing of 0.80 x 0.30 m following agronomic cultural practices recommended for this crop. Phosphorus concentrations in all the potato plant parts were significantly affected by the P fertilizer rates applied. The highest correlation between the P concentration in the various plant parts and marketable yield and optimum profit yield was obtained for the petiole taken 20 days DAE. Critical P leve...

Avaliação do estado nutricional do nitrogênio em batateira por meio de polifenóis e clorofila na folha

The objective of this work was to evaluate the effect of N rates on physiological indexes related to nitrogen nutrition in potato, and to verify the possibility of indirectly estimating leaf N contents. Flavonol (FLVI), chlorophyll (CHLI), and the nitrogen balance (NBI) indexes were evaluated, and estimations of leaf N contents were made at 21 and 42 days after emergence using the Dualex leaf‑clip instrument. The experiment was carried out from November 2010 to February 2011, in a randomized complete block design, with five N rates (0, 50, 100, 200, and 300 kg ha -1 of N, applied as urea) at pre‑planting, and four replicates. There was an increase in CHLI and NBI and a decrease in FLVI with the increasing N doses. The indexes determined with Dualex were correlated with N and extractable chlorophyll content in the fourth leaf and with potato tuber yields. Dualex can be used to evaluate N nutritional status in potato plants, and for the prognosis of final tuber yield with readings.