Evaluation Of Soil Fertility Quality Of Typical Terraced Fields In Loess Hilly Region

The Loess Plateau of Northwest China has been suffering from serious soil erosion,while terrace is one of the important measures on soil and water conservation in loess plateau.Its soil quality directly affects the sustainable development of agricultural production as well as efficiency of soil conservation.This study chose the soil of typical terraces on loess plateau as the research object and investigated the physical,nutritional and biological characteristics of soil and evaluated the soil comprehensive quality from data collected from field investigation and indoor determination of the soil quality indicators.The main conclusions are as follows:(1)The nutrient contents of the surface layer(0~20 cm)were higher than those of the lower layer(20~40 cm)in both areas,showing the effect of the surface in soil nutrient content under different planting types.Overall,the nutrient content shows higher level on greenhouse,apple orchard,forest than on agricultural lands and new abandoned land.Organic matter content shows moderate level in Zhuanglang compared with its low level in Ansai.Total nitrogen content in both areas are at low level.Total phosphorus content generally shows moderate level in both types of lands except high level in greenhouse.The available nutrient content is moderate-to-low.The available phosphorus is high in greenhouse while the rest were at low level.The available potassium shows moderate-to-low situation in both areas.(2)The variation coefficient of pH in different cultivars was 4.02% in the three study areas,which indicated as non-sensitive index.The variation range of soil nutrients content was large.For the case of total phosphorus,the variation coefficient was as small as 23.68%,labeled as the moderate sensitive index.While the available phosphorus variation coefficient was 226.39%,which was highly sensitive index.(3)The soil comprehensive quality in these three basins of Baozi ditch,Majiagou and Fangta is examined to be the middle level,which is consistent with the previous studies on the soil status of the Loess Plateau,indicating that the results of soil quality evaluation in this study are accurately reflecting the real situation of the study area soil.The comprehensive quality of soil in Baozigou watershed is as follows: potato land> grassland> intercropping>wheat> maize >apple.The comprehensive quality ofsoil in Majiagou watershed is: abandoned land> Greenhouse>maize> Soybean.The soil comprehensive quality index of Fangta watershed is as follows: potato> intercropping> maize> apple> fallow.The soil quality of potato in the Loess Plateau was generally higher than other types of lands,and hence,the growing potato is beneficial to improve the production of grain crops in this area.Although the fruit growers take great efforts on the apple orchard,the comprehensive quality of the apple soil is lower than that of the agricultural land because of the large demand of nutrients in the soil.Overall,the intercropping of apple and potato could mutually improve the comprehensive level of soil quality in the region.