Geovane Webler

Evaluation of a Dynamic Agroecosystem Model (Agro-IBIS) for Soybean in Southern Brazil

With the growing demands for food and biofuel, new tech- nologies and crop management systems are being used to increase productivity and minimize land-use impacts. In this context, estimates of productivity and the impacts of agriculture management practices are becoming increasingly important. Numerical models that describe the soil-surface-atmosphere inter- actions for natural and agricultural ecosystems are important tools to explore the impacts of these agronomical technologies and their environmental impacts.

INFLUENCE OF SOIL PROPERTIES IN DIFFERENT MANAGEMENT SYSTEMS: ESTIMATING SOYBEAN WATER CHANGES IN THE AGRO-IBIS MODEL

AbstractThe water balance in agricultural cropping systems is dependent on the physical and hydraulic characteristics of the soil and the type of farming, both of which are sensitive to the soil management. Most models that describe the interaction between the surface and the atmosphere do not efficiently represent the physical differences across different soil management areas. In this study, the authors analyzed the dynamics of the water exchange in the agricultural version of the Integrated Biosphere Simulator (IBIS) model (Agro-IBIS) in the presence of different physical soil properties because of the different long-term soil management systems. The experimental soil properties were obtained from two management systems, no tillage (NT) and conventional tillage (CT) in a long-term experiment in southern Brazil in the soybean growing season of 2009/10. To simulate NT management, this study modified the top soil layer in the model to represent the residual layer. Moreover, a mathematical adjustment to th...

EFFECTS OF A STRAW LAYER ON THE SOIL THERMAL BEHAVIOR

The presence of crop residue on the soil surface has an impact on evaporation, water storage, soil temperature and soil heat flux. Consequently, changes the energy transfer in the soil-atmosphere system. The objective of this work is study the influence of crop residues in the soil thermal variables. It was concluded that the thermal effect of a straw layer is large, leading to surface temperature differences around 10°C. With depth increasing, the effect of straw coverage decreases, leading to a temperature difference to 4°C of 5cm depth. The most important consequence of higher temperature on bare ground is an increase of soil heat flux. In stable weather conditions, this difference can reach 29 W/m 2 .

EVAPOTRANSPIRATION PARTITION FOR A MAIZE CROP

Crop transpiration is directly related to its production. Plant transpiration varies along the crop cycle and in most part of this cycle is the dominant component in evapotranspiration. There are several well-established techniques to estimate these components individually. Currently, the eddy covariance technique is widely used for measurements of evapotranspiration. However, this technique is unable to identify the flow of water between the surface and the atmosphere has its origin by evaporation from soil or plant transpiration. A new methodology based on the efficiency of water use by the plant is being used successfully. This technique determines how much water is transpired to each carbon molecule attached to the plant. This efficiency ratio is obtained by the difference of external and internal concentration on stomatal cavity of CO2 and H2O. In practice, external concentration of carbon and water is obtained from the infra-red gas analyzers used to obtain data in eddy covariance technique. In this work, the evapotranspiration for a maize crop in southern Brazil is partitioned and compared to the surface model AGRO-IBIS. Results show that the maximum development of the plant transpiration is approximately 70% of evapotranspiration.

AVALIAÇÃO DO MODELO WRF COM DIFERENTES PARAMETRIZAÇÕES CONVECTIVAS PARA UM CASO DE CICLOGÊNESE NA BACIA DO PRATA

O impacto da escolha do esquema de parametrizacao convectiva na representacao da precipitacao associada a um caso de ciclogenese e analisado utilizando o modelo WRF. Os indices estatisticos ETS e BIAS score mostraram que para os limiares de chuva fraca a moderada, o esquema de ajuste convectivo de Betts-Miller-Janjic obteve uma melhor representacao da precipitacao.

BALANÇO DE ENERGIA E TROCA LÍQUIDA DE CO2 PARA UM CICLO DA CULTURA DO MILHO NO MODELO AGRO-IBIS

Neste trabalho, e apresentado o balanco de energia e a troca liquida de CO 2 (NEE) para um ciclo da cultura do milho com o modelo Agro-IBIS. Os resultados indicam que o modelo representa bem as trocas entre o ecossistema e o ambiente na maior parte do ciclo, com excecao no periodo de senescencia foliar.

ANÁLISE DA EVAPOTRANSPIRAÇÃO E ÍNDICE DE ÁREA FOLIAR NUMA CULTURA DE SOJA SOB DOIS SISTEMAS DE MANEJO

Neste trabalho sao analisados resultados da evapotranspiracao (ET) e do indice de area foliar (IAF) obtidos durante a estacao de cultivo (2009/2010) para os sistemas de plantio direto (PD) e plantio convencional (PC) no ciclo da cultura da soja, no municipio de Cruz Alta, Rio Grande do Sul (RS).

ESTUDO DO BALANÇO DE ÁGUA PARA O CULTIVO DE SOJA SOB DOIS SISTEMAS DE PLANTIO

1. Introdução O desenvolvimento de novas tecnologias e de técnicas de manejo do solo possibilitaram a expansão da área de cultivo da soja (Glycine max (L.) Merril), nas últimas décadas no Brasil. As mudanças nas formas dos manejos alteram as propriedades físicas e hídricas do solo, sendo que a disponibilidade hídrica é a maior causa de variabilidade dos rendimentos de grãos observados a cada ano nas diversas regiões produtoras brasileiras. Também é o principal fator limitante à obtenção de rendimentos próximos ao potencial produtivo da espécie (Farias, 2004). Com isso o conhecimento do balanço de água de uma área plantada é importante para a avaliação da disponibilidade hídrica.

VARIAÇÃO ANUAL DOS FLUXOS DE ENERGIA NUMA CULTURA DE ARROZ IRRIGADO

This work is quantified and analyzed the variation of annualflows of energy in relation to net radiation in a culture of rice in Paraisodo Sul. The calculation of the flow of energy was done by the method ofcovariance turbulent vortices. The average annual flow of latent heat,sensible heat and soil were respectively 70.24 W/m2, 14 W/m2, 1.4 W/m2.The annual average net radiation was 97.04 W/m2 while the balance ofenergy was 85.64 W/m2. In this period the variation of energy in thelamina water was not measured. Thus it is possible that the differencebetween net radiation and energy balance is associated with energy storedin the water layer

ESTIMATIVA DOS FLUXOS SUPERFICIAIS DE ENERGIA E MASSA NA REGIÃO DO PAMPA GAÚCHO

As trocas de energia e massa entre o pampa gaucho e a atmosferasao estimadas atraves do modelo de superficie SiB2 e comparados comdados experimentais obtidos no sito experimental de Candiota-RS. Asestimativas dos fluxos superficiais descrevem satisfatoriamente a interacaoentre a superficie e a atmosfera