The Characteristics And Assessment Of Soil Fertility Of Farmland And Forestland In The Northeast Sandy Area Of Ulanbuh Desert

This paper took woodlands, shrub lands and a variety of farmlands as research objects in the Northeastern Sandy Area of Ulan Buh Desert, using the method of combining field investigations and laboratory experiments, basic characteristic and differentiation of soil fertility in different woodlands, shrub lands and varieties of farmlands were studied; using the method of combining principal component analysis and factor analysis evaluated soil fertility quality to reveal existing problems of soil fertility quality, and to provide the basis for selection of soil phytoremediation measures. The main results of the research were as follows:1. Soil texture coarse degree and agglomeration rate had certain differences among woodlands, among shrub lands and among farmlands. In terms of the ability of improving soil physical properties, three arbor tree species including Cladrastis sinensis, Populus simonii×(Populus pyramidalis + Salix matsudana) cv. Poplaris, Populus gansuensis. and shrub species with nitrogen fixation including Calligonum mongolicum, Caragana korshinskii, Hippophae rhamnoides were better to improve soil physical properties and were dominant tree species in sandy areas. Medicago sativa can be planted or changing fertilization modes and management measures improves soil texture conditions in farmlands.2. Soil organic matter, nitrogen and phosphorus were relatively poor in woodlands, shrub lands and farmlands, most of them were "low" level. Contents of rapidly available potassium of the soil surface of most of various lands, including Populus gansuensis, Cladrastis sinensis Hemsl., Populus simonii×(Populus pyramidalis + Salix matsudana) cv. Poplaris, Tamarix chinensis, Elaeagnus angustifolia, Hedysarum scoparium, and Citrullus lanatus, Helianthus annuus, Medicago sativa, Lycopersicon esculentum, were "grade 3", and belonged to a medium level. Contents of rapidly available potassium of other lands were "grade 4", belonged to potassium deficiency level. CEC, CaCO3 and pH value had a few of variations among lands, and also had no significant changes compared with CK.In terms of the ability of improving soil physical properties, Populus gansuensis, Cladrastis sinensis,Tamarix chinensis and nitrogen-fixing shrub species (Tamarix chinensis, Hedysarum scoparium, Hippophae rhamnoides, Elaeagnus angustifolia) were better to improve and to enhance the whole soil nutrient and are better tree species in the sandy area, and Populus. Alba var. pyramidalis, Salix matsudana, Caragana korshinskii, Calligonum mongolicum, Atraphaxis bracteata and Zygophyllum xanthoxylum were relatively worse. Distributions of soil chemical properties were extremely uneven in varieties of farmlands, which was mainly related to fertilization, irrigation and crop types, etc. Thus, to change the cropping systems and fertilization enhances furtherly the level of soil nutrients.3. Organic matter and most of Chemical properties existed significant or extremely significant relations, which appeared the leading role of organic matter in soil fertility. Total nitrogen was the main source of available nitrogen (extremely significant relation). Total phosphorus had a few of contributions to available phosphorus (not significant relation). Dynamic transforming relations of different degree were showed among various forms of potassiums. CEC had effect of different degree on various nutrients. pH value, CaCO3 and electrical conductivity affected to some extent enrichment and substitution of various nutrients, etc. Soil chemical indicators had sensitivity of different degrees to soil physical properties, especially contents of small particles such as clay or physical clay not only determined conversion, leaching rate, release ability of available nutrients, but also had an important influence on improving and enhancing CEC, contents of soil CaCO3, electrical conductivity.4. Results from assessment of soil fertility quality: Woodlands: Cladrastis sinensis, Populus simonii×(Populus pyramidalis + Salix matsudana) cv. Poplaris and Populus gansuensis are better, belonged to"grade 2", others were"grade 5". Shrub lands: Elaeagnus angustifolia belonged to"grade 2", Caragana korshinskii and Hippophae rhamnoides were"grade 3","grade 4"(Tamarix chinensis and Calligonum mongolicum) and"grade 5"(Hedysarum scoparium, Zygophyllum xanthoxylum and Atraphaxis bracteata) lands had appeared degredations of different degrees. In varieties of farmlands, Lycopersicon esculentum belonged to"grade 1"; Medicago sativa and Citrullus lanatus belong to"grade 2"Helianthus annuus and Zea mays were""grade 4"; Lavatera trimestris was"grade 5". To sum, several measures should be timely taken for woodlands, shrub lands and farmlands existing soil fertility quality degration to improve soil quality.