Interception and Use of Solar Radiation in Mustard/ Grass Pea Intercropping

Solar radiation is of prime importance as it drives primary growth processes of plants. However its use in mustard and grass pea association is not yet analyzed. Therefore, a study was conducted at the Bangladesh Agricultural University during the cropping season extended from November 2014 to March 2015 to assess whether the mustard and grass pea crops are compatible when they grow together as intercrops in terms of radiation interception and use along with growth and productivity performances. Mustard was considered as a dominate crop and grass pea as an intercrop. The experiment comprised four treatments viz. sole mustard, sole grass pea, single row alternate intercropping (i.e. 1M:1G, where one row of mustard was grown followed by one row of grass pea), and double grass pea row intercropping (i.e. 1M:2G, where one row of mustard followed by two rows of grass pea). Both mustard and grass pea plants in sole cropping had higher leaf area index (LAI) and total dry matter (TDM) accumulation as compared to that at intercropping. Mustard grown with 1M:1G intercropping system showed higher LAI and TDM accumulation than those at the 1M:2G system however, opposite trend was found for grass pea. The combine intercrop canopy of 1M:2G showed higher radiation-use efficiency (RUE; 2.44 g MJ-1 PAR) followed by 1M:1G (2.29 g MJ-1 PAR) and sole mustard canopies (1.89 g MJ-1 PAR) whereas the sole grass pea stands showed minimum RUE (1.17 g MJ-1 PAR). Maximum grain yield of mustard (2.32 t ha-1) was harvested from sole cropping which was about 19 and 31% higher than that obtained from 1M:1G (1.87 t ha-1) and 1M:2G (1.60 t ha-1) intercropped mustard, respectively. Similarly, sole grass pea (1.45 t ha-1) produced about 32 and 3% higher seed yield as compared to single (0.99 t ha-1) and double row (1.41 t ha-1) intercropped grass pea, respectively. The 1M:1G and 1M:2G combined intercropping systems gave the highest land equivalent ratio (1.493 and 1.663) and area time equivalent ratio (1.313 and 1.507, respectively). In 1M:1G intercropping system, mustard exhibited higher competitive ratio over grass pea but in 1M:2G intercropping system grass pea significantly dominated over mustard. It can be concluded that the mustard and grass pea crops are compatible in their intercropping mixture and the performance of double row of grass pea alternatively grown with a single row of mustard is superior to their sole stands or single row intercropping system due to the improved utilization of solar radiation.