Selective inverted sink efficiency for spring frost protection in almond orchards northwest of Isfahan, Iran

A so-called selective inverted sink (SIS) was validated in frost protection of a 20-ha almond orchard. Daily counts of flower buds were made for two branches of some selected almond trees in every plot to determine frost damage percentage. Temperatures increased due to the SIS system, but there was an average gradient of temperature decrease of about 0.4°C per 100?m with distance from the SIS. The minimum air temperature increased from 0.5 to 2.8°C, with the highest increase closest to the SIS. The percent of frost-damaged flower buds of almond relative to the control plot with distance to the SIS system had its maximum gradient (8% per 100?m ) in 100?C200-m distance from the SIS, but this gradient decreased to a minimum (4% per 100?m) in 500?C700-m distance from the SIS. The ANOVA and Duncan??s multiple-range test of air temperature and frost damage data confirm that the significant influence zone of this local SIS was about 500?m.