Alberto Eduardo Knies

Funções de pedotransferência para estimativa da retenção de água em alguns solos do Rio Grande do Sul

Soil physical hydraulic properties are determinations considered expensive and difficult to obtain. The use of pedotransfer functions (PTFs) is an alternative for obtaining such properties more easily and practically costless. The objective of this study was to develop and validate PTFs to estimate soil water retention of different textural soil classes in the State of Rio Grande do Sul, Brazil. The research was carried out using data from physical analysis of soils belonging to the database of Sistema Irriga laboratory, Universidade Federal de Santa Maria. This database consists of soil texture information (sand, silt and clay), density (of soil and of particles), soil porosity (macro, micro and total), besides of water content information at the matrix potential of 0, -1, -6,-33, -100, -500 e -1500kPa. Soil samples were collected on the surface layer of cultivated soils of RS. The variables were submitted to a correlation test, and were subsequently analyzed in multiple regressions test to obtain the PTFs, using the stepwise option of the SAS statistical program. The generated PTFs showed greater associations of soil attributes only related to soil structure such as soil water retention for higher potential (0 and -1kPa) and textural and structural attributes for lower potential (-33, -100, -500 e -1500kPa). The PTFs showed high accuracy in estimating soil water holding capacity of the considered potentials.

Estimativa do filocrono em milho para híbridos com diferentes ciclos de desenvolvimento vegetativo

The phyllochron is defined as the thermal time needed for the appearance of successive leaves on the plant main stem. Through the phyllochron it is possible to calculate the length of the growing period and thus the flowering period based on the air temperature. This study aimed to determine the phyllochron from different maize hybrids. Three field experiments were carried out during the agricultural years of 2007/08, 2008/09 and 2009/2010. The experimental design was one of randomized blocks with three repetitions. The treatments consisted of 18, 22 and 24 maize hybrid during the three agricultural years of 2007/08, 2008/09 and 2009/2010, respectively. The phyllochron was estimated by the inverse of the angular coefficient of the linear regression between the number of leaves and the accumulated thermal sum from emergence on (base temperature = 10°C). The calculated phyllochron varied from 44.3 to 34.4°C day-1 leaf-1 among the evaluated hybrids, being the phyllochron value of hybrids directly related to the precocity of the growing period.

Plastocrono e número final de nós de cultivares de soja em função da época de semeadura

The plastochron, which is the time interval between the appearance of two successive nodes and the final node number (FNN) are important variables of the vegetative development in soybean. The objective of this study was to determine the plastochron and the FNN of soybean (Glycine max (L.) Merrill) cultivars sown in different dates under irrigated conditions in a subtropical location. A field experiment was carried out in Santa Maria, RS, Brazil during 2005/2006 growing season, with three sowing dates (09/11/2005, 09/12/2005 and 28/01/2006). It was used 15 soybean cultivars recommended for the Central and North Argentina, and South and Southeast Brazil. The variables measured were the number of nodes (NN) and the (FNN) on the main stem. The plastochron was estimated by the inverse of the slope of the linear regression between NN and the thermal time (base temperature = 10°C) accumulated since plant emergence. The late sowing resulted in lower plastochron and FNN, probably because of the lower photoperiod under which the plants were submitted in the node phase, a typical response of short day plants.

Bioclimatic mapping of Rio Grande do Sul state for animal and human thermal comfort

O presente estudo teve como objetivo realizar o zoneamento bioclimatico do estado do Rio Grande do Sul, a partir do indice de umidade e temperatura (ITU), para o conforto termico de animais e do trabalhador rural. O estudo foi realizado para 27 municipios do estado. Os dados meteorologicos necessarios para o calculo do ITU foram obtidos no site do Instituto Nacional de Meteorologia, referentes ao periodo compreendido entre 1961 e 1990. Foram utilizados os dados de temperatura maxima do ar (Tar max), temperatura minima do ar (Tar min), umidade relativa maxima (UR max), umidade relativa minima (UR min), temperatura media compensada (TMC) e umidade relativa compensada (URC). O ITU foi calculado em tres situacoes: (i) ITU maximo (ITU max); (ii) ITU minimo (ITU min); (iii) ITU medio (ITU med). A analise geoestatistica e confeccao dos mapas tematicos foram realizadas utilizando o programa computacional GS+, versao 9. Os resultados do ITU max, obtidos para o estado do RS, indicaram condicoes ambientais muito quentes a extremamente quentes, no periodo primavera/verao, com maior severidade nas regioes de menor altitude, podendo trazer consequencias graves a saude do trabalhador rural e condicao de perigo para os animais. Abstract The present study had as objective bioclimatic mapping of Rio Grande do Sul state, based on the moisture and temperature index (ITU), for animal and human thermal comfort. The study was carried out for 27 municipalities in the state. The meteorological data needed to calculate the ITU were obtained from the website of the National Institute of Meteorology, from 1961 to 1990. The data for maximum air temperature (Tar max), maximum relative humidity (RH max), minimum relative humidity (RH min), mean compensated temperature (TMC) and compensated relative humidity (RHC). The ITU was calculated in three situations: i) ITU maximum (ITU max); ii) ITU minimum (ITU min); (iii) mean ITU (ITU med). The geostatistical analysis and thematic mapping are performed using the GS + software, version 9. The results of the ITU can be obtained for the state of the RS, in the regions of lower altitude, which can have serious consequences for the health of the rural worker and animals.