Characteristics of mechanical composition and mineral composition of cultivation land the former Dang Xa – Le Chi area, Gia Lam, Hanoi city

The land specialized for vegetable cultivation extending from the former Dang Xa through Le Chi Communes, Gia Lam, is part of the green vegetable belt supplying the inner city of Hanoi. This area is one of the sources of vegetables and fruits for the daily consumption needs of the city. In order to clarifying the characteristics of structure, mechanical composition, mineral composition of cultivation land of the former Dang Xa - Le Chi area, Gia Lam, Hanoi city, the authors have conducted field surveys, dug holes, study the soil profiles through the dug holes and collect soil samples. Combination of analytical methods in the lab such as grain size analysis, the XRD method, scanning electron microscopy (SEM) for fine grain bath, and stereomicroscopy method. The results of the studying soil profiles show that the cultivation land in Dang Xa-Le Chi area compose of mainly young alluvial soil, distributed on the sediments of the Thai Binh Formation. In general, the soil has mainly 2 layers structure: The upper layer: from the surface down to 35-45cm, has the composition of silt, finegrained sand, brown, loose, and organic matter; The lower layer is distributed mainly at a depth of 45-50 cm, the composition of silt-clay is yellow-brown, more solid, in many places containing thin layers with black and yellow-brown laterite spots. For mechanical composition of cultivation land in the study area is mainly loamy soil, heavy silt-clay soil and sandy clay. The mineral composition of coarse-grained bath is mainly quartz, iron hydroxides/oxides with small or little amount of feldspar, rutile, amphibol, micas... In fine-grained batch, quartz also accounts for the majority, followed by illite, kaolinite, montmorillonite, goethite, chlorite. Feldspar and other minerals such as gibsite, amphibol, hematite and calcite account for small amounts. In terms of characteristics of structure, mechanical composition, mineral composition of cultivation land in the study area is quite favorable for the cultivation of short-term, terrestrial crops, including vegetables. The research results will contribute the scientific basis for the sustainable management and development of safe vegetable cultivation areas in the areas.