| Ten seasonal rivers are located in the northern ordos plateau, frequent floods, causing large amount of high flood peak,as steep fall,discharged into the Yellow River, often appearing giant sand bar in the entrance of Yellow River, then blocking the Yellow River, but also cause serious soil erosion and desertification.Study on the silted tilth land of flood silting engineering in Gongwusu. after respectively in 2005,2007 and 2013 samples collected and measured the 7 fertility indicators, also studied and analyzed the change law of each index.Then established the soil fertility quality evaluation index system and evaluation model in order to evaluate soil fertility quality. The main conclusions as follows were reached:1. By using the flood silting engineering in order to lead into the flood with high sand for silting up many times,has improved the soil nutrients and found that the integrated fertility index of the silted tilth land was obviously higher than undisturbed soil.Also five indicators of fertility levels are higher than the undisturbed soil,such as the organic matter, total nitrogen, total potassium, total phosphorus and alkaline hydrolysis nitrogen.2. With the increase of farming years, the content of organic matter, total nitrogen, alkali solution nitrogen and total potassium in the silted tilth land is basically increasing from the point of horizontal distribution; And the content of total phosphorus, available phosphorus and available potassium is shrinking. The distribution of soil fertility index in upstream, middle and downstream is not obvious in whole layer and surface layer.3. With the increase of soil depth, the content of organic matter, total nitrogen, alkali solution nitrogen, total phosphorus and available phosphorus is reduced from the point of vertical distribution, however,surface layer is the highest level; And the content of total potassium and available potassium does not change significantly with the increase of the depth.4. Evaluation indicators include organic matter, total nitrogen, total phosphorus, total potassium, alkali solution nitrogen, available phosphorus and available potassium;then evaluate the soil fertility quality by fuzzy mathematics method and gray correlation degree. The change tendency of the two kinds of statistical results are consistent, also grading is almost the same. According to the national department of agriculture standard NY/T3092-1996 national farmland type farmland productivity hierarchies, more than 90% of the sample area belongs to â…¢ level and â…£ level. According to the determination of weight, the correlation between four kinds of soil fertility index and the soil fertility quality index is higher, four kinds of soil fertility index are available potassium, available phosphorus, alkaline hydrolysis nitrogen and organic matter. We can give priority to select these indicators fertility index when doing evaluation. |
