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Print version ISSN 0006-8705On-line version ISSN 1678-4499

Bragantia vol.53 no.1 Campinas  1994 



Test of a soil water assessment model for a sorghum crop under different irrigation treatments


Teste de um modelo de monitoramento de água no solo para uma cultura de sorgo submetida a diferentes tratamentos de irrigação



Marcelo Bento Paes de CamargoI; Kenneth G. HubbardII; Francisco Flores-MendozaIII

ISeção de Climatologia Agrícola, Instituto Agronômico (IAC), Campinas (SP), Brazil 13001-970. Bolsista do CNPq
IIDep. Agric. Meteorol., Chase Hall, Univ. of Nebraska, Lincoln, NE, USA 68583
Centro de Investigaciones Agrícolas del Norte Centro, Calera de V.R., Zacatecas, México 98500




A model to monitor the soil water status using automated weather station data, crop phenology, and soil information was adjusted and tested for a sorghum crop using field experiments with eight different water treatments in a randomized split factorial block irrigation design during the 1990 and 1991 growing seasons at Mead, Nebraska-USA. Estimates of the total soil water content from the soil water balance model matched well with neutron-probe readings in the sorghum crop. Model performance by soil layer indicates slight underestimates of soil water content in the upper layers of soil, slight overestimates of soil water content in the lower soil layers, and close agreement between simulated and observed soil water contents in the middle soil layers. Elimination of these small offseting errors from the model would result in an improved performance within layers. One possible means of eliminating the error is to adjust the root soil water extraction slightly away from the upper levels and toward the lowest levels. Based on the fact that model estimates of total soil water were in good agreement with observations, it is concluded that it is reasonable to estimate soil water conditions on a routine basis using near-real time automated weather station data.

Index terms: soil water balance, Sorghum bicolor L., evaporation, transpiration, soil moisture.


Um modelo de balanço hídrico diário utilizando informações de estação meteorológica automática, fenologia e informações edáficas foi ajustado e testado para uma cultura de sorgo usando experimentos de campo com diferentes tratamentos de irrigação durante o verão de 1990 e 1991, em Mead, Estado de Nebraska-EUA. Estimativas do total de água no solo a partir do balanço hídrico compararam-se bem com as leituras de sonda de nêutrons tomadas nos diferentes tratamentos. O desempenho do modelo, por camadas de solo, indicou pequena subestimativa da umidade nas camadas superiores, pequena superestimativa nas inferiores e boa estimativa nas intermediárias. A eliminação desses erros resultaria em melhor desempenho do modelo nas diferentes camadas. Boas estimativas do total de água no solo podem ser obtidas através deste balanço hídrico edafoclimático modificado com base em informações fenológicas, edáficas e de dados obtidos de estações meteorológicas automáticas.

Termos de indexação: balanço hídrico, sorgo, Sorghum bicolor L., evaporação, transpiração, umidade do solo.



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Received for publication in December 29, 1993 and revised in February 6, 1994.

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