Estimation of net radiation in sunflower as a function of solar radiation

This study aimed to develop models for estimating the net radiation (Q *) from the incident solar radiation (Rg) on canopies of sunflower plants. The experiments were conducted at the Plant Science Department of the Federal University of Santa Maria in 2007, 2008 and 2009 years. Q* was measured by net radiometers above the plants and Rg by automatic weather stations. For purposes of calculation, daily sums of Q* and Rg were performed, obtaining the relationship between Q* and Rg for each day. Models with high coefficient of determination and low RQME were obtained in test between measured and estimated values from an independent database, indicating precision to estimate net radiation in sunflower canopies, regardless of cultivation time in year. The general linear function with data obtained from different times of cultivation was: Q* = 0.5285 Rg (R-2 = 0.95), that the test showed RQME = 1.04 MJ m(-2) d(-1). It was concluded that net radiation (Q*) can be estimated using solar radiation measured by an automatic stations with sufficient accuracy for different purposes in sunflower agrometeorology.