Weed Ecology of Brassica fields of Abbottabad District and Correlation of Weeds with Physical and Chemical Nature of the Soil

Abstract

Indo-Pak subcontinent is the world‘s largest cultivator of Brassica. It constitutes 33 % of the world‘s land, cultivated under rapeseed and mustard crops. Weeds ecology of Brassica crops i.e., Brassica juncea (L.) Czern. (Mustard), B. rapa L. and B. napus L. (Rapeseed) were explored for elaborating the weed species profile in districts of Abbottabad, Haripur and Mansehra. Weeds are the part of dynamic ecosystem growing in cultivated crop or ordinary environment. Its flora has not been evaluated quite often from its ecological point of view and phytosociological classification because of its deteriorating impacts on economic crops. Therefore, its flora in Brassica crop of the aforementioned districts was quantitatively analyzed under the impact of various environmental variables. Quadrate quantitative ecological techniques were used for sampling of weeds vegetation. Phytosociological attribute and physiognomic characteristics of each weed species were recorded at each quadrate. Physicochemical properties of soil were measured at each station and compared with quantitative and synthetic characteristics of weed communities. A total of 50 weed species (44 dicot & 6 monocot) were recorded from Brassica crops belonging to 20 different plant families. The topmost abundant weed of the Brassica crop was Euphorbia helioscopia, Galium aparine and Coronopsus didymus while, Lapsana communis, Scandix pecten veneris and Parthenim hysterophorus were the rare weed species with minimum importance values. Euphorbiaceae was the topmost dominant family followed by Poaceae and Brassicaceae in the studied area. All the collected weeds belong from therophytes life form category. Species belonging to Constancy Classes IV-V were Euphorbia helioscopia, Coronopus didymus and Fumaria officinalis appearing close to 50 % of the stands in Mustard and Rapeseed fields. While Anagallis arvensis, Avena sativa and Galium aparine present in less than 50% of the stands (Class: III - IV). Species revealed to Class I, were present either in Mustard or Rapeseed fields. It appears that the synthetic characters followthe pattern of Quantitative Characers upto certain extent. Result of soil characteristics revealed that the soil of Abbottabad and Mansehra districts were mostly silty clay loam different from Haripur and Havelian regions along with silt loam soil condition. Furthermore, soil of Abbottabad and Haripur has maximum amount of N-NO3, pH as compared to Mansehra. Potassium (K) and Phosphorus (P) concentration were higher in soil of Mansehra and Haripur rather than Abbottabad Havelian regions. Regarding, Zinc (Zn) and Manganese (Mn) concentration which is higher in Haripur and Mansehra respectively. Electrical conductivity (EC) was higher in all three regions except Haripur. 2

While, increased amount of nitrate concentration in soil is due to the abundantly presence of nitrogen fixation weeds in the fields. The aforementioned finding i.e., weeds of Brassica crops, their general profile and distribution in different farming systems of the area will provide a baseline for devising weed management strategies in the studied area. It will also open a new venue of research for Brassica crops improvement through the scientific ways of weed eradication.