Sandro Luis Petter Medeiros

Substratos na produção hidropônica de mudas de hortelã

The normal growth and the formation of plants with quality for commercialization depends on good seedlings production. The right substrate has to be used. Hydroponic cultivation holds certain advantages: saving substrate, resulting in good establishment of the crop and quality of seedlings production. The experiment was carried out at the University of Santa Maria, Rio Grande do Sul State, Brazil. The effect of substrates (without substrate, phenolic foam substrate and organicmineral substrates) was determined on the production of mint (Mentha x villosa) transplants by cuttings vegetable methods in hydroponics. The experimental design was a completely randomized design with three treatments and 20 replications, one plant being used in each repetition. We evaluated: height and number of leaves at 7; 14; 21 and 28 days after the transplant. Fresh and dry matter weight 35 days after transplant were also analyzed. The phenolic foam substrate showed the best results in relation to the production of fresh and dry matter. Phenolic foam and the organicmineral substrates were not significantly different, but were significantly superior to the treatment (direct in solution) without substrate.

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.

Arranjo de plantas na expressão dos componentes da produtividade de grãos de canola

O objetivo deste trabalho foi avaliar os efeitos do arranjo de plantas nos componentes diretos da produtividade de graos e na producao final em canola, com uso de hibridos de diferentes ciclos de desenvolvimento. Foram realizados tres experimentos com espacamento entre linhas de 0,20, 0,40 e 0,60 m, em delineamento experimental de blocos ao acaso, com quatro repeticoes para cada ano de cultivo (2008 e 2009), genotipo (Hyola 432 e Hyola 61) e densidade de plantas (20, 40, 60 e 80 plantas por metro quadrado). Hyola 432 apresentou maior producao de graos em comparacao a Hyola 61, independentemente do ano e da densidade de cultivo. Os efeitos do ano de cultivo influenciaram mais a producao e os componentes da produtividade de graos do que o potencial genetico da cultivar e a densidade de cultivo. O ajuste da densidade de plantas em canola e alterado pelo genotipo e pelo ano de cultivo.

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.

Estimativa da área foliar de meloeiro em estádios fenológicos por fotos digitais

This experiment was aimed at evaluating the precision of digital photos in estimating the leaf area of watermelon plants and to find mathematical models that estimates leaf area as a function of leaf linear measurements at different growth stages. All odd leaves of eight plants were photographed after being established on the field using a digital camera that resulted in 4,188 photos in which length and width were measured using a Sigma Scan Pro v. 5.0 Jandel Scientific software. In order to estimate the precision of the digital photos method, a sample consisting of 40 leaves was taken and leaf area measured using the standard leaf disks and the photo method. A 0.99 correlation coefficient was detected between the two methods. Therefore digital photos can be used to estimate leaf area of watermelon plants and estimation of leaf area per growth stage presents higher precision. The larger variability in leaf area was observed during reproductive growth. Maximum leaf width is the measure that best estimates leaf area.

Água no solo e rendimento do trigo, soja e milho associados ao El Niño Oscilação Sul

The objective of this study was to simulate soil water content, and wheat, soybean and maize yields, in Santa Maria, RS, Brazil, and link their interannual variability to El Nino Southern Oscillation (ENSO). The period studied was 1969 to 2003. Soil water content and the yields of wheat, soybean and maize were simulated with models available in the literature. Soil water content was represented by the fraction of transpirable soil water. The results showed that the lowest soil water content in Santa Maria is associated to neutral years and the highest soil water is associated to El Nino events. La Nina years were more favorable to high wheat yield, whereas El Nino years were more favorable to high soybean and maize yields. It was evident that years classified as neutral years in respect to ENSO are riskier to grain yields of soybean and maize crops, which is an important information for planning strategies in agribusiness considering ENSO forecast.

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.

MODIFICAÇÃO AMBIENTAL CAUSADA POR TÚNEIS BAIXOS DE POLIETILENO TRANSPARENTE PERFURADO CULTIVADOS COM ALFACE

Determinou-se as modificacoes ambientais causadas por tuneis baixos de polietileno transparente perfurado instalados no Departamento de Fitotecnia da Universidade Federal de Santa Maria, RS. As densidades de perfuracao estudadas foram 100, 200, 300 e 400 perfuracoes por m2 correspondendo, respectivamente, a uma area perfurada de 0,78% CT1), 1,57% (T2), 2,35% (T3) e 3,14% (T4). Os resultados evidenciam que a densidade de perfuracao nao modificou significativamente a disponibilidade de energia solar. A medida que aumentou-se a densidade de perfuracao ocorreu um decrescimo no valor medio diurno da temperatura do ar, aspecto que demonstra a viabilidade de ventilar o tunel baixo atraves da perfuracao do plastico. Tambem observou-se que nos tuneis perfurados, os valores medios da temperatura do solo, minima e media diurna do ar e umidade relativa do ar foram maiores que no ambiente externo.

Temperatura base inferior e ciclo de híbridos de canola

The aim of this study was to determine the lower base temperature (Tb) of two canola hybrids during the subperiods emergency-beginning of flowering (EM-IF), early-flowering-late flowering (FI-FF) and late-flowering physiological maturity (FF-MF), and the number of days in each subperiod. The experiment was carried out with nine seeding times with the hybrids Hyola 61 and Hyola 433 in Santa Maria, being utilized two methods to estimate: least deviation and relative development. There was a negative linear relationship between air temperature and cycle length in days. The Tb values of canola genotypes ranged from -0.6 to 9.1°C for relative development method, and -1 to 11°C for the least deviation method. The average duration for the subperiods EM-IF, IF-FF and FF-MF were respectively 65, 47 and 24 days for hybrid Hyola 61 and, 68, 48 and 23 days for hybrid Hyola 433. The cycle duration of two hybrids decreased with delayed sowing, which reduced from 162 to 100 days in Hyola 433 and 162 to 104 days in Hyola 61.