Paulo Augusto Manfron

Qualidade de cultivares de alface produzidos em hidroponia

The purpose of this research was to define the centesimal composition of six lettuce cultivars (Aurora, Brisa, Livia, Mimosa, Regina and Veronica) using four nutrient solutions. The experimental design was carried out in Santa Maria, RS, Brazil, consisting of entirely randomized subdivided parcels. The used spacing was 0.18 m between array and 0.25 m among plants. It was observed that the Ueda solution should not be used for the lettuce production in NFT system, due to the high dry mass production and, consequently, high caloric value, content of lipids and fibers, depreciating the quality of the final product, in spite of its low nitrate content. The lettuce production in the NFT system using the Castellane-Araujo, Furlani and Bernardes solutions maintained the nutricional quality (protein, ethereal extract and fiber, mineral residue contents) equivalent to the lettuce produced in soil, but presenting smaller caloric value. Therefore, the hydroponic lettuce is a healthy food for maintaining and improving its centesimal composition for being a product of low caloric value, easy cleaning and high durability.

Modelos para estimar o acúmulo de fitomassa de alface em hidroponia

The protected and hydroponics cultivation are increasing in Brazil, demanding a better knowledge of crop performance in this environment. Plant dry matter accumulation as a function of solar radiation, temperature, relative humidity and other weather parameters in greenhouse is different when compared with field cultivation. With the purpose of proposing models to characterize the temporal variation of leaf and total dry matter production of hydroponics-grown lettuce (Lactuca sativa L.) and to determine the flowering period and the maximum dry matter accumulation rate as a function of plant relative development (relative degree-days), solar radiation and effective thermal index, two experiments (Spring and Autumn) were carried out in the greenhouse, at Santa Maria, Rio Grande do Sul State, Brazil. Growth and development models are useful in obtaining basic information on the plant ´ environment interactions, maximizing the use of resources in greenhouse, as well as, to define the best form of crop management. The cultivar Vera was chosen as function of its earliness. Models were proposed to estimate the temporal variation of dry matter accumulation, where the best results for relative development were obtained using effective degree-days, characterizing the importance of the air temperature for the vegetative phase and the solar radiation for the reproductive. The yield and quality of the lettuce seeds evidenced a high potential of hydroponics technique.

A questão do nitrato em alface hidropônica e a saúde humana

Lettuce (Lactuca sativa L.) is the main vegetable crop produced hydroponically. In this kind of cropping, the majority of nitrogen is provided as nitrate, which may lead to the accumulation of this ion in cells. Nitrate amount in plants depends upon genetic factors, the availability of this nutrient in roots and environmental factors. Several studies have indicated that the consumption of nitrate may be harmful to human health, causing methaemoglobinaemia and gastric cancer. However, recent studies have proposed that there is no link between nitrate and these diseases, and that nitrate may be even good for human health as a protector against gastroenteritis. Some other studies have indicated that the presence of certain vitamins in plants is likely to inhibit possible negative effects of nitrate. High nitrate concentrations in lettuce grown hydroponically in northern European countries have been a matter of concern to the scientific community and Brazilian consumers. Nevertheless, studies have demonstrated that in Brazil, because of higher solar radiation at low latitudes, nitrate amounts found in lettuce produced hydroponically are much lower than the amounts given by the European community, indicating no risk to human health.

CRESCIMENTO E DESENVOLVIMENTO DA ALFACE (Lactuca sativa L.) CONDUZIDA EM ESTUFA PLÁSTICA COM FERTIRRIGAÇÃO EM SUBSTRATOS

In order to study the effects of fertirrigation in growing substrates on the development of lettuce cultivar Brisa, two essays were conducted, one during the fall of 1998 and the other during the winter, in a plastic greenhouse in the Federal University of Santa Maria. The treatments with and without fertirrigation were constituted by earthworm humus plus rice hulls (H+CN), earthworm humus plus carbonized rice hulls (H+CC) and pure soil as check. The fertirrigation timing was established by monitoring the electric conductivity of the substrates drained solution. The experimental design was a randomized block with four replications. Once a week, the number of leaves per plant, fresh and dry weight of above ground plant parts and leaf area index were determined. The water retention capacity (CRa) of the isolated substrates and mixtures both before and after the establishment of the plants was also determined. The substrates CRa values increased along the growing season whereas soil CRa was constant. The substrates irrigated with nutritive solution resulted in plants with greater leaf numbers, higher dry and fresh above ground weight and higher leaf area index when compared with plants irrigated with water only. The H+CN and H+CC substrates were significantly more productive that the check substrates in both growing seasons.

Temperatura base inferior e estacionalidade de produção de genótipos diplóides e tetraplóides de azevém

The objective of this study was to estimate lower base temperature Tb of three diploid (Comum, Fepagro Sao Gabriel, and LE 284 and two tetraploid (Avance and INIA Titan) ryegrass genotypes. With the estimated Tb, it was also possible to investigate if these genotypes may have seasonal production, which helps in programming herds feeding schedules. Five sowing dates (11/05, 07/06, 05/07, 09/08 e 01/09/2007) were performed in Santa Maria, RS, Brazil. Two methods were used to estimate Tb: least deviation method and relative development method. Tb values varied from 7.0 to 8.5°C for diploid genotypes and from 9.0 to 10.6°C for tetraploid genotypes, depending upon the method. Diploid ryegrass germoplasm have no risk of seasonal decrease in forage production, whereas tetraploids, mainly Avance, may have their growth and development decreased from June to August in Santa Maria because of minimum air temperature.

Eficiência do uso da radiação solar por plantas Ilex paraguariensis A. St. Hil. cultivadas sob sombreamento e a pleno sol

The efficiency of conversion of the solar radiation in biomass is a variable frequently used in models of simulation the culture growth, because the biomass production is related with the efficiency of which a plant converts radiant energy in chemistry, given by the process of the photosynthesis. The objective of this work was to determine the efficiency of conversion of the photosynthetically active and intercepted solar radiation (RFAi) in Ilex paraguariensis biomass, cultivated in consortium (Ilex paraguariensis A. St. Hil. E Pinus elliottii Engelm) and single. For so much, it was determined the photosynthetically active and intercepted solar radiation (RFAi), the index of leaf area and the biomass dries of the seedlings, being then, the efficiency of conversion of RFAi in biomass dries of the cultivated in consortium and single. For a same radiation value RFAi, is obtained larger efficiency of use of the radiation in the accumulation in matter dries when Ilex paraguariensis is cultivated in consortium. The conversion efficiency (eb) of biomass total drought of Ilex paraguariensis plants in relation to the amount of the photosynthetically active and intercepted solar radiation (RFAi) accumulated is of 0.83 g MJ-1 in the system consortium and of 0.23 g MJ-1 in the single system. In spite of that, the production of aerial biomass for plant was larger in the single system.

Expolinear model on soybean growth in Argentina and Brazil

Predicting crop growth and yield with precision are one of the main concerns of the agricultural science. For these purpose mechanistic models of crop growth have been developed and tested worldwide. The feasibility of an expolinear model for crop growth was evaluated on predicting growth modification on soybean (Glycine max L. Merrill) of determined and undetermined growth cultivars, submitted to water restrictions imposed on different phenological stages. An experiment was carried out in Azul/Argentina and in Vicosa/Brazil during the growing seasons (1997/1998, 1998/1999 and 2002/2003). The expolinear model was adjusted to the dry-matter data obtained from each treatment. The model showed sensibility of Rm (maximum relative growth rate of the culture - g g-1 day-1) to variation in air temperature; of Cm (maximum growth rate of the culture - g m-2 day-1) to solar radiation and of Tb (lost time -day) to water stress. Cm values were higher without water restriction presenting, in both countries, a direct correlation with solar radiation. Without water restrictions, Rm values were lower when the average air temperature during the cycle was lower. It was observed that under water stress the culture had a bias to present higher Rm values. Tb was lower in the irrigated treatments than in those with water deficits. The analysis of the outputs clearly shows the feasibility of the expolinear model to explain the differential growth rates of soybean as a consequence of climatic conditions.

Crescimento e teor de óleo essencial de mentas com diferentes concentrações de potássio na solução nutritiva

The work was carried out at the Universidade Federal de Santa Maria, Rio Grande do Sul State, Brazil, from October to December 2004. Three simultaneous experiments were carried out, each one with one Mentha species (M. arvensis, M. x gracilis and M. x piperita var. citrata) in four hydroponic solutions with different K concentrations (276; 414; 552 and 690 mg L-1 ) and plant ages. The experimental design was of randomized complete blocks, with five replications, the treatments showing a factorial for each species: 4x6, 4x7 and 4x8, four K concentrations and plant ages being determined weekly starting 27 days after planting date. The height of plants; foliar area; fresh and dry phytomass of leaves and stems; leaf:stem relation; and the content of essential oil in fresh leaves were evaluated. The increase of K concentrations in the hydroponic solutions affected negatively the growth and accumulation of phytomass in mint plants, but allowed an increase in the content of essential oil per plant. In all consecutive harvesting dates an increase in the growth of the three species of plants were observed. M. arvensis and M. x piperita var. citrata accumulated more stem than leaf phytomass, the reverse occurring with M. x gracilis, which also presented a higher equivalent production of oil per ha, in the lowest K concentration. A good growth of Mentha under hydroponic cultivation was observed under K concentrations of 276 and 414 mg L-1.

Forragem hidropônica de milheto: produção e qualidade nutricional em diferentes densidades de semeadura e idades de colheita

This study aimed to evaluate the effect of different harvest dates and sowing densities on growth and bromatological composition of hydroponic millet forage. The experiment was carried out in the Crop Production of the Universidade Federal of Santa Maria, RS, Brazil. A randomized experimental design was used. Treatments consisted of four sowing densities (0.5, 1.0, 1.5 e 2.0kg seed m-2) and two harvest dates (10 and 20 days after germination) distributed in a 4x2 factorial scheme. There was no interaction between sowing densities and harvest date for all analyzed variables. Plant height, dry biomass, hemi cellulose and lignin were not influenced by sowing density. Increasing sowing densities increased the values of crude protein and fresh biomass, and decreased the values of neutral and acid detergent fiber and cellulose. Harvest at 10 days after germination showed higher values of fresh and dry biomass, cellulose, hemi cellulose and lower values of neutral and acid detergent fiber and lignin. It was not observed statistical difference in crude protein in relation to the two dates of harvest. The best quality feature of hydroponic corn forage was verified with 2.0kg seed m-2 and harvest at 10 days after sowing.

Testes para determinação do potencial fisiológico de sementes de abóbora

This work aimed to determine the efficiency of different tests to access the physiological potential of squash seed lots. Six seed lots were submitted to germination and vigor tests (germination first count; speed of germination; cool germination; accelerated aging; seedling emergence; seedlings growth and dry biomass (root, hypocotyl and total) and plants (root, stem and total length, root, stem, root plus stem, leaves and total). A completely randomized design was used with four replicates. The averages were compared by the Tukey test (p < 0.05). Pearsons correlation test was also performed. The germination first count, speed of germination, accelerated aging, root plus stem and leaves dry biomass from plants evaluated in the 21st day after sowing can be used to determine the physiological potential of squash seeds.