Radiation interception, light extinction coefficient and leaf area index of wheat (Triticum aestivum L.) crop as influenced by row orientation and row spacing

A field experiment was conducted at the B A College of Agriculture, Anand Agricultural University, Anand (India)(22°35’N, 72°55’E; 45.1 m MSL)during rabi (winter) season of 2003-2004 on a sandy loam soil to study the effect of row orientation and row spacing on radiation interception, Leaf Area Index and Light extinction coefficient in Wheat (Triticum aestivum L.) cv. GW-496 under two dates of sowing. The PAR values in terms of incident/incoming PAR and transmitted PAR at the field were measured after canopy development (i.e. 23 Days after sowing) at 10 day intervals at 0900-1000 h, 1200-1300 h and 1500-1600 h in a day with a Sun San Canopy Analysis System (Delta-T Devices, UK). LAI was also measured directly by the Sun Scan Canopy Analysis System at noon. The instantaneous values were averaged for that day and were converted to MJm^-2 day^-1. Solar radiation was recorded by a Pyranometer. The conversion of the daily solar radiation to PAR was made by employing a 0.5 fraction. Narrow NS (North-South) rows in general produced higher LAI throughout the growing season. NS row with narrow spacing was the most effective treatment in relation to the accumulated IPAR values, although the differences in the values corresponding to other treatments were not remarkable. The fluctuations in extinction coefficient (k) values were less random in NS rows than those corresponding ones for EW rows.