Embrapa Trigo Boletim de Pesquisa Online Nº 4, dez./2000


Gilberto Rocca da Cunha 2
Homero Bergamaschi 3
Moacir A. Berlato 2
Ronaldo Matzenauer 4


The main form of energy exchange between earth’s surface and the atmosphere is through electromagnetic radiation which involves short and long-wave fluxes. The net radiation (Rn), global solar radiation (Rs) and reflected radiation (Rr), above the surface of a maize crop, Zea mays L., cv. SAVE-342, was measured during selected days at different crop development stages, in the 1986/87 growing season, in Taquari, RS, Brazil (29º48'S, 51º49'W and altitude of 46 m). The albedo (a ), short-wave balance [(1 - a ) Rs], long-wave balance (I), heating coefficient (b ) and long-wave exchange coefficient (l ) were calculated based on the above mentioned measurements. The variation of Rn was highly associated with the variation of Rs. Daily mean albedo (a ) ranged from 0.19 to 0.24. Heating and long-wave coefficients showed interactive effects between the characteristics of atmosphere and soil surface. Linears models of Rn estimates above the maize crop were adjusted with Rs (r2 = 0.979) and [(1 - a ) Rs] (r2 = 0.943).

Index terms: albedo, short-wave balance, long-wave balance, net radiation, Zea mays L.

1Extraído da dissertação de mestrado apresentada pelo primeiro autor à UFRGS-Faculdade de Agronomia, agosto de 1988.
2Eng. Agr., Dr., Embrapa-Centro Nacional de Pesquisa de Trigo (Embrapa Trigo), Caixa Postal 451, CEP 99001-970 Passo Fundo, RS.Bolsista do CNPq-PQ.
3Eng. Agr., Dr., UFRGS-Fac. Agron., Caixa Postal 776, CEP 90001-970 Porto Alegre, RS. Bolsista do CNPq-PQ. 
4Eng. Agr., Dr., Fundação Estadual de Pesquisa Agropecuária (FEPAGRO), Rua Gonçalves Dias, 570, CEP 90570-001 Porto Alegre, RS. Bolsista do CNPq-PQ.

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