Weed Dynamics in Acid Saline Pokkali Ecosystem of Kerala

Abstract

Background: Pokkali is a versatile rice- fish system of cultivation, producing naturally organic rice along the waterlogged coastal regions of Kerala. The weed flora of Pokkali rice fields is different from other rice ecosystems. Diverse weed flora appears in low saline phase, when rice is cultivated, but they dry up and decompose in high saline phase. With time, significant deviations have been reported in various climatic parameters and as a result, the weed spectrum has also undergone changes. Methods: Two level stratified surveys and anotomical studies were conducted during Kharif 2017 and 2018 to study the weed flora in five major Pokkali growing blocks of Kerala. Two panchayaths (political village units) from each block and two padasekharams (group farming units) in each panchayath were selected for surveying. To understand the adaptive mechanism of weeds in saline soil condition, anatomical studies were performed on individual weed species. Result: Cyperaceae family dominated in the ecosystem with more number of species. Diplachne fusca and Eleocharis dulcis were the major weeds. Echinochloa crus-galli, a dominant weed reported in earlier weed survey was found confined to very few locations and the frequency got reduced from 80% to 12.5%. In addition, Sphenoclea zeylanica was observed as an emerging weed with notable morphological adaptations. Floating ferns like Najas graminea and Hydrilla verticillata caused problems to aeration in the water in fields.