Mônica Lima Alves Pôrto

Nitrate production and accumulation in lettuce as affected by mineral Nitrogen supply and organic fertilization

Lettuce is one of the leading vegetables in Brazil. However, studies concerning its fertilization for the Northeastern region of the country are still scarce. This work was carried out to evaluate the effects of mineral Nitrogen supply and organic fertilization on the production and nitrate accumulation in lettuce, cultivar Elba, in the semi-arid zone of Paraiba, Brazil. A randomized block design, with four replications, was used to test five doses of cattle manure (30; 60; 90; 120, and 150 t ha-1), five doses of N supplied as urea (30; 60; 90; 120, and 150 kg ha-1), and a control without fertilization. Along with mineral N, the other nutrients were also supplied using mineral sources. No additional nutrients were supplied where organic fertilization was used. Lettuce yield was significantly higher when organic fertilization was used, compared to the mineral nutrient supply. Taking into account most of the fertilization doses recommended for growing lettuce in the Brazilian Northeastern States, N mineral fertilization in sandy soils with low organic matter contents can be fully replaced by organic fertilization with cattle manure. Plant total (PTY) and commercial yield (PCY) as affected by the mineral N supply fitted into a quadratic model, in which the doses 94.5 and 95.7 kg ha-1 corresponded to respectively the highest PTY (381.9 g plant-1) and PCY (321.6 g plant-1). Where organic fertilization was used, PTY and PCY fitted into a linear model. Therefore, the highest PTY (523.9 g plant-1) and PCY (449.48 g plant-1) were observed at the highest manure doses. Nitrate content on roots, stems, and leaves increased linearly with Nitrogen and manure application. In roots, the nitrate content (mg kg-1 of fresh matter) reached 93.96 (N mineral (Nm)) and 65.09 (organic fertilization (OF)); in stems, 183.45 (Nm) and 98.22 (OF); and in leaves, 121.98 (Nm) and 75.62 (OF). The maximum nitrate content observed in leaves was far below the risk level for human health.

Índice SPAD para o diagnóstico do estado de nitrogênio na cultura da abobrinha

SPAD index for nitrogen status diagnosis of zucchini plants The employment of SPAD index for N status diagnosis of crops has been largely studied in recent years. However, conclusive studies about its usefulness in zucchini plants were not found in literature. The objective of this study was to evaluate the employment of SPAD index for N status diagnosis of zucchini plants (cv. Caserta). The experiment was carried out in Vicosa, Minas Gerais State, Brazil, in a randomized block design with five rates of mineral N (0, 50, 100, 200 and 400 kg/ha), with four replications. At the early flowering stage, total chlorophyll concentration, SPAD index and total N concentration in the fourth fully expanded leaf from the apex of zucchini plants were evaluated. The total chlorophyll concentration, SPAD index and total N concentration in zucchini leaves increased following a quadratic model as a function of the N rates. The estimated critical levels of total chlorophyll concentration, SPAD index and total N concentration on zucchini leaves responsible for maximum fruit yield were 5.12 mg/g of fresh matter, 55.62 units and 3.97 dag/kg of dry matter, respectively. Significant linear and positive correlation between the evaluated characteristics was observed. The results indicate that the SPAD index can be used for N status diagnosis of zucchini plants.

Absorção e distribuição de chumbo em plantas devetiver, jureminha e algaroba

SUMMARY : ABSORPTION AND DISTRIBUTION OF LEAD IN VETIVER,MIMOSA AND MESQUITE PLANTS The use of plants for phytoremediation of metal-contaminated areas is an emergingtechnology, and studies concerning heavy metal tolerance, absorption and distribution inplants are essential for the success of such programs. This study was carried out to evaluatethe tolerance, absorption and distribution of lead (Pb) in vetiver grass [ Vetiveria zizanioides(L.) Nash], mimosa [ Desmanthus virgatus (L.) Willd] and mesquite trees [ Prosopis juliflora(SW) DC] subjected to increasing lead doses in solution. The experiment was conductedunder a screenhouse, at the DSER/CCA/UFPB, Areia-PB, Brazil. The species were grownin nutrient solution containing increasing Pb levels (0, 50, 100 and 200 mg L -1 ) during a 45-day exposure period. An entirely randomized split-plot design was used with threereplicates. The main plot was represented by the plant species and the subplot by Pblevels. The increased Pb levels caused significant reductions of dry mass of the root, shootand whole plant (root + shoot) in the three species under study. Based on critical toxicitylevels, the tolerance of vetiver to Pb contamination was higher than in the other species. Invetiver and mesquite plants, the roots were the component most sensitive to Pbcontamination, whereas a similar response to Pb by all plant components was observed formimosa. Total Pb concentrations and content in plant compartments were significantlyaffected by the increasing Pb levels in solution, and a higher accumulation of this elementwas observed in the roots of the three species under study. The highest Pb concentrationand content were found in all compartments of vetiver, which suggests a high potential ofthis grass for phytoremediation of Pb-contaminated areas.Index terms: pollution, heavy metal, phytotoxicity, tolerance, phytoremediation.

N Sources and Doses on Japonese Cucumber Yield and Nitrate Accumulation in Fruits in Greenhouse

Despite Japanese cucumber nutritional and commercial importance, few studies have been carried out with the nitrogen (N) fertilization of the crop, especially in greenhouse conditions. This study objective was to evaluate the Japanese cucumber yield and nitrate (NO3-) accumulation in the fruits in greenhouse as a function of the N sources and doses at Vicosa, Minas Gerais State, Brazil. The experiment was set in a randomized complete block design, arranged in a 2 × 5 factorial scheme, with two N sources (ammonium sulphate and ammonium nitrate) and five N doses (0; 75; 150; 300 and 600 kg ha-1), with four replicates. The number of fruits per plant, average fruit mass, fruits yield and NO3- accumulation in the fruits were evaluated. The maximum economic efficiency N doses for two N sources used was calculated according to the prices of the fertilizers and Japanese cucumber fruits practiced in 2010. There were no significant effects of N sources and of the interaction between N sources and N doses for the productive characteristics (number of fruits per plant, average fruit mass and fruits yield) of the Japanese cucumber. However, all the productive characteristics of the Japanese cucumber increased following a quadratic model as a function of the N doses. The maximum economic efficiency N doses for the fruits yield of Japanese cucumber were 398 kg ha-1 and 386 kg ha-1, resulting in fruits yield of 76.38 t ha-1 and 76.29 t ha-1, for the ammonium sulphate and ammonium nitrate, respectively. NO3- accumulation in Japanese cucumber fruits as a function of the N doses for two N sources evaluated was not verified.