Boletim de Pesquisa Online Nº 4, dez./2000

RADIATION BALANCE IN MAIZE CROP

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

Abstract

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.