| Located in the southeast part of Jiangsu Province, the city of Taicang enjoys a relatively higher production level of industry and agriculture, while industrial spot pollution and area pollution in agricultural do exist. The pollution will influence agricultural products quality. As a result, to understand the fertility and quality of cultivated land and take exclusive measures to improve comprehensive productive capacity by launching regional investigation and evaluation on cultivated land fertility is of great realistic significance on food security and promoting sustainable development of regional agricultural as well as our economical society.The fertility and soil environmental quality of cultivated land covering an area of 36000 hectare of Taicang was studied in this thesis. In 2005, GIS technology was used to sample and analyze the soil in the research region. Classification on land quality was done by vague mathematic statistics. Nemerow index method was used to evaluate environmental quality of the soil and countermeasures for improving and recovering of cultivated land were proposed. The results obtained showed that:First, the average soil nutrient contents were revealed in the year of 2005. The organic matter (OM) content in cultivated land of Taicang was between 23.66g/Kg The mean value for the content of total nitrogen, available phosphorous and available potassium in the soil studied were 1.54g/Kg, 16.8 mg/Kg and 82.8 mg/Kg, respectively. Comparing with the results gained from the 2nd national soil survey, soil OM, the content of total nitrogen and available phosphorous have been all around improved. Available potassium content in cultivated land soil of Taicang was slightly decreased, though. As for the microelements, silicon and boron were insufficient in parts of the soil. And molybdenum was in severely deficiency, other trace elements were abundant in the soil.Second, cultivated land classification was completed. We classified 36001.79 hm~2 of cultivated land into 5 grades. The area of the first, second and third class land were 501.63 hm~2, 6478.72 hm~2 and 19313.02 hm~2, accounting for 1.39%, 18.00% and 53.64% of the total, respectively. The fourth-class land was 22.56% of the total, with area of 8123.46 hm~2 and the area of the fifth-class land was 1584.96 hm~2, taking up 4.40% of the total. Third, the evaluation on land environmental quality in Taicang showed that in 2005, 23.3% of the cultivated land was safe and clear, 60% of all was clean and 16.7% of the soil has alr(?)ady been polluted. And the major pollution factors were Cd, Zn and residual DDT. The evaluation showed that the irrigation water quality was up to standards for the production of green foods and pollution-free agricultural productsAccording to our evaluation, we proposed policies and measure to improve and recover the cultivated land in Taicang city in future, including applying more organic fertilizer, supplementing chemical fertilizers such as potassium, silicon, boron and molybdenum, in order to improve nutrient balance and elevate fundamental fertility of the land continuously. Carry out regular monitoring on land quality, establish land preserving funds and prop up commercial organic fertilizer production and green manure plantation to promote peasants' initiative to preserve the land. Zeolite powder, degradation bacteria for pesticide residues and plants with high heavy metal accumulation ability should be used to recover the contaminated soil and improve environmental quality of the soil. |
