Dr. Parimal Kanti Biswas
Professor
Department of Agronomy, SAU, Dhaka.
A 2-years project was started with the financial support of SAURES of which one experiment was conducted in 2007-2008 and other experiment in 2008-2009. The objective of the project was to identify the allelopathic effect of Brassica species along ith their incorporation method, maturity and concentration to control weeds in wheat field. The wheat variety "Shatabdi" was used as a test crop. The first experiment was assigned in a split-plot design where three cultivated Brassica spp. viz. Brassica campestris, Brassica juncea and Brassica napus were in the main plot and five different ways of inclusion were in the sub-plot and the second experiment was comprised with three factors as previous crop conditions (fallow & mustard) were assigned in the main plot; two maturity date of Brassica biomass (25 days & 35 days) in the sub-plot and three levels of biomass concentration (0, 0.5 kgm-2& 1.0 kgm-2) in the sub sub-plot. Brass/ca crops were sown on November 2, 2007 for the first experiment and 01 & 12 November for the second year experiment those were uprooted at flower initiation for the first year and as per treatment for the second year and applied as per treatment. Wheat seeds were sown on using 20 cm line to line distance. Weed samples were collected two times on 30 DAS and 50 DAS for counting weed population and dry weight. Some weeds e.g.. Aniuranthus spinosus, A. viridis, Lindernia procumbens, Helioiropitun inclicum, Polygonum hydropiper, Celo,sis argentina, Ageratum conyzo ides, Brass/ca kuber and
Digitaria ischaemum were not found to the wheat field. Significantly the highest weed dry matter (1.72 g/m2) was revealed in Brassica juncea plots at 30 DAS but in Brass/ca napus field (1.44 g/m2) at 50 DAS. The lowest weed dry matter (0.89 g/m2) was recorded in total incorporation of Brassica biomass to the soil at 30 DAS but 50% incorporation and 50% spreading at 50 DAS. Weed population densities had no significant variations for Brassica species at 30 and 50 DAS and for incorporation methods at 50 DAS though the lowest weed population (15.33/m2) was revealed in spreading between lines that similar to complete incorporation and 50% spreading and 50% incorporation at 30 DAS. The different Brassica species showed the similar response but the Brass/ca biomass spreading above ground (B,), mixed with soil (B3) and 50% spreading + 50% mixed with soil (B5) resulted positively compared to other ways of biomass incorporation.
Brassica Biomass, Weed control, Wheat, Allelopathic effect,
Argonomy field, SAU
Pest Management
i) To study the allelopathic effect of Brassica spp. to control weeds in Wheat
ii) To study the spreading/incorporation behaviour of different studied materials
iii) To find out the optimum concentration of rapeseed and mustard biomass to control weeds
iv) To find out the optimum time of applying biomass
Two experiments under the title of "Control of weeds in Wheat by applying Rapeseed and Mustard biomass" and "Influence of previous land condition, crop maturity and biomass conc. to weed control and yield of Wheat" were conducted at the Agronomy farm of Sher-e-Bangla Agricultural University, Dhaka- 1207, during the period from November 2007 to October 2009. The top soil was silty clay loam in texture. Organic matter content was very low (0.82%) and soil pH varied from 5.47-5.63. Three Brassica varieties one from campestris, one from juncea and the other from napus species were sown on November 02, 2007 in a medium high and well drained land in the first year and for the second year Brassica campestris was sown on November 01 & 12, 2008. The crop
was fertilized with 180-100-180 -60-10-5 kg/ha of urea, TSP, MP, Gypsum, Boric acid and Zinc oxide respectively of which half of urea and the full amount of other fertilizers applied as basal dose. As the crops were uprooted, no additional urea fertilizer was applied. Weeding, mulching and thinning were done at 20 DAS. The Brassica crop was uprooted at 30 DAS for the first experiment and at 25 & 35 DAS for the second experiment. The land was then ploughed and cross ploughed, leveled and fertilized as per recommendation of wheat. The experiment was laid out in split-plot design (first experiment) and split split-plot design (second experiment) with three replications. Three Brassica species was assigned in the main plot and six different ways of biomass incorporation (No biomass application, biomass spreading above the ground, biomass mixed with soil, biomass spreading in lines and 50% biomass as spreading + 50% biomass as mixed with soil) in the sub plot for first year experiment. For the second year experiment, previous field condition ( no Brassica crop and with Brassie() crop) was
assigned in the main plot; ages of Brassica biomass (25 days and 35 days) in the sub plot and biomass concentrations (0, 0.5 kgm-2 and 1.0 kgm-2) in the sub sub-plot. The wheat variety Shatabdi (BARI gorn 21) was sown on 04 December, 2007 and 07 December, 2008 for the first and second year respectively. One third urea and the full amount of other fertilizers were applied as basal and the rest urea in two equal splits at CRI stage and before flowering stage. All the intercultural operations were done as and when necessary. Weed data was recorded on 30 and 50 DAS. The yield and other yield attributes were recorded using standard procedures. IRRISTAT computer package was
used for data analysis and compare the treatment means
110000
Weed species were identified during the experimentation and the weeds those were not
found in Brassica biomass treated plots are shown in Table 1. The results showed that Brassie() biomass had allelopathic effect to suppress some weed species in wheat field.
Report/Proceedings