Gean Lopes da Luz

Growth and yield of lettuce plants under salinity

Plantas de alface, cv. Vera, foram cultivadas em cinco niveis de salinidade em um dispositivo experimental composto por uma camada de areia de 0,15 m de profundidade. Foi empregada uma solucao nutritiva padrao, com a seguinte composicao, em mmol/L: 16,9 de NO3-; 2,0 de H2PO4-; 1,0 de SO4-; 4,0 de Ca++; 10,9 de K+ e 1,0 de Mg++, e, em mg L 1, 0,42 de Mn; 0,26 de Zn; 0,05 de Cu; 0,50 de B; 0,04 de Mo, e 4,82 de Fe quelatizado. Os cinco niveis de salinidade foram obtidos por variacoes na concentracao da solucao nutritiva padrao, atingindo valores medios de condutividade eletrica (CE) de 0,80; 1,93; 2,81; 3,73 e 4,72 para T1, T2, T3, T4 e T5, respectivamente. A solucao nutritiva em cada nivel de salinidade foi fornecida a partir de um reservatorio atraves de uma bomba submersa, durante 15 min, em intervalos diurnos de 90 min e noturnos de 420 min. Um dispositivo experimental inteiramente casualizado foi empregado, com quatro repeticoes e 20 plantas por parcela. Quatro plantas de cada tratamento foram coletadas aos 32 dias apos o plantio para determinar a massa seca da parte aerea e das raizes, a massa fresca da parte aerea, a area foliar e o numero de folhas. O numero de folhas por planta foi igual a 18, sem diferenca significativa entre os tratamentos. A massa seca de folhas aumentou 24,4% de T1 para T3. A massa seca do caule foi reduzida nos niveis salinos mais elevados, porem nao foi observada relacao dos tratamentos com a massa seca do caule e das raizes. Foi observado efeito positivo na massa fresca da parte aerea, a qual aumentou 28,5% de T1 para T2, decrescendo 16,5% de T2 para T5. O valor maximo estimado do indice de area foliar foi de 4,3 m2 m-2 para uma EC de 2,6 dS m 1. Concluiu-se que niveis salinos acima de 2,0 e 2,6 dS m 1 reduzem o crescimento e a massa fresca das plantas, respectivamente.

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.

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.

Cultivo hidropônico da alface empregando substratos: uma alternativa a NFT?

Foi desenvolvido um dispositivo experimental para o cultivo da alface em sistema hidroponico fechado empregando substratos. As bancadas foram constituidas por telhas de cimento amianto, cujos canais foram preenchidos com brita basaltica. Sobre a brita foram dispostos os substratos, formando uma camada de 0,05 m de altura, com a superficie revestida com filme de polietileno opaco branco. As mudas foram produzidas em bandejas de poliestireno e plantadas em orificios feitos sobre a superficie do filme de polietileno. Uma solucao nutritiva completa foi fornecida diariamente, por meio de tubos gotejadores localizados na superficie da camada de substrato e abaixo do filme de polietileno. A solucao drenada foi recolhida por gravidade para dentro do reservatorio principal. Foram conduzidos dois experimentos, no periodo entre 16 de maio e 24 de junho e 1o e 28 de outubro de 2003, empregando as cultivares Regina e Mimosa e os substratos areia media e substrato orgânico Plantmax® Folhosas HA. No decorrer dos experimentos, houve diminuicao dos valores de pH da solucao nutritiva, tendo sido feita apenas uma correcao em cada um dos experimentos. No dia mais quente do experimento de primavera, a temperatura foi mais elevada na areia, sem diferenca significativa do substrato orgânico, cuja media situou-se 5,4oC acima da temperatura da solucao nutritiva e 0,4oC acima daquela do ar. As medias mais elevadas das variaveis de crescimento e desenvolvimento foram observadas no substrato orgânico no outono, enquanto, na primavera, foram constatadas nos tratamentos tendo areia como substrato. O emprego dos substratos permitiu uma reducao em torno de 92,4% no tempo de funcionamento da motobomba e simplificou tanto o manejo da fertirrigacao como os controles da solucao nutritiva.

Relação potássio-nitrogênio para o diagnóstico e manejo nutricional da cultura da batata

The objective of this work was to determine the maximum K dilution curve and the relationship with the N dilution curve, during growth and development of the potato crop, for nutritional diagnosis and fertilization purposes. Treatments consisted of nutrient solutions with K concentrations of 3.5, 5.5, 6.5, 8, and 9.5 mmol L-1. The completely randomized experimental design was adopted with four replications. Four plants were harvested, at weekly intervals, to quantify plant growth and to determine N and K tissue concentrations. The maximum K dilution curve was adjusted, and the maximum K uptake was determined, during crop growth and development. It was observed that maximum K concentrations might be estimated from critical N concentrations. Quantities of K fertilizers to be supplied to achieve a pre-fixed crop yield can be estimated from tissue N concentration.

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.

Characterization of the Use and Occupation of Soil on Rural Properties Using Remotely Piloted Aircraft Systems - RPAS

The use of remotely piloted aircraft systems allows for practicality in the collection and monitoring of study areas or in the development of rehabilitation projects for degraded areas. As such, this technology is gaining space as an alternative for applications in studies and surveys of several areas. This work is justified by the demand for projects and the search for practical alternatives that will enable the framing of rural properties according to the new Brazilian Forestry Code (Codigo Florestal Brasileiro) and its environmental recovery plans (Plano de Recuperacao Ambiental). The objective of this study is therefore to evaluate the use of a Remotely Piloted Aircraft System in the monitoring of a rural property, seeking to include it in the framework of the Brazilian Forestry Code. To accomplish this work, information samples were taken in an area of 30.19 ha of a rural property with the use of a Remotely Piloted Aircraft System - RPAS. After the data collection, the images were treated using the QGis software and through the generation of an ortho-mosaic, which enabled the data to be analyzed and interpreted. With the interpretation of land use and occupation data and with the generation of maps of land use and occupation, a diagnosis of the current situation of the area can be obtained. In a second phase, maps were created to include the property in the current legislative framework, seeking its regularization. After the completion of this work, the conclusion can be drawn that the use of a Remotely Piloted Aircraft System - RPAS is viable and enables the monitoring of rural areas with efficiency and speed.

Factorial Economic Planning Applied to Agricultural Experimentation

Innovation may be limited by the scarceness of resources, such as financial, homogeneous area, skilled labor or other research needs, for example the difficulty in experimental control of large areas in the field. In research areas such as chemistry and physics, designs are used in such a way that when compared to the agronomic designs, they result in a reduced number of experimental units, which in this work are called economic designs. Thus, the objective of this study was to identify significant factors and effects (p-value

Percepção dos agricultores familiares do município de Nova Erechim (SC) em relação à legislação ambiental

This study aimed to evaluate the perception of family farmers in the municipality of Nova Erechim (SC) in relation to environmental legislation. The case study was conducted in 42 rural properties, based on the calculation of simple random sampling plan. The guiding questions were: understanding of farmers in relation to the concept of the term Area of Permanent Preservation (APP); the interest of farmers in recovering APPs; the difficulties of farmers in relation to legal limitations to the APPs. The data collected were subjected to descriptive statistical analysis and determined the absolute frequency (Fj) e relative frequency (fj), they were interpreted by drafting tables. The main difficulty raised by farmers regarding legal limitations to the APPs is the lack of information on the topic environmental law confusing it with the Legal Reserve.