Radiation interception parameters in mustard and its modification due to debranching

An experiment was conducted during 2004–05 and 2005–06 in sandy clay loam soils of Indian Agricultural Research Institute (IARI), New Delhi representing semi arid climate. Treatments include two cultivars namely ‘Pusa Jaikisan’ and ‘BIO-169-96’, two date of sowing i.e. 15^th October (timely sowing: D1) and 30^th October (late sowing: D2) and debranching that include removal of three to four lower branches at 40 days after sowing (early debranching: P1), 50 days after sowing (late debranching: P2) and no branch removal (control: P0) Plant compensated for loss of branches and leaves, by producing additional leaves and branches. Timely sown crop has higher tendency to compensate for loss of branches (debranching) during vegetative stage. ‘BIO-169-96’ was found more vigorous hence more suitable for debranching. Radiation penetration from top to bottom was almost similar in all the treatments except 40 to 115% higher value for a week or so in case of debranching. Penetrations from mid to bottom were 30 to 68% higher in case of debranching for considerable part of time (20–45 days) as plants compensated by producing upper branches and not the lower ones. Peak radiation use efficiency for both the cultivars were in the range of 3.03 to 3.97 g MJ⁻¹. Relatively higher radiation use efficiency was observed during grain filling stage in case of debranching. ‘BIO-169-96’ witnessed lower extinction coefficient as compared to Pusa Jaikisan. The relationship between fraction of intercepted radiation (fIPAR) and LAI were logarithmic. In case of timely sown crop, removal of lower 3 to 4 branches at 5 to 6 branch stage may be a mechanism to generate additional biomass as mustard have strong tendency to compensate for loss of branches and leaves.