福建沿海地区农业土壤全量养分丰缺评价

农业土壤除了pH值、有机质、全氮、全磷、全钾有全量评价标准外,多目标地球化学调查提供的其他营养和有益元素均无全量评价标准。文章采用耕作地土壤的背景值和标准离差以及与全国土壤丰度的比值确定了其他13种营养和有益元素的丰缺分级评价标准。提出了土壤养分丰缺综合评价方法,将19种土壤养分指标分成土壤性质指标、一级营养元素指标、二级营养元素指标及微量营养和有益元素指标,其贡献总分值分别为30分、40分、15分和15分,组成类型的单指标总分值与该类型贡献总分值相同,根据丰缺分级评价标准和各单指标含量,计算单指标分值。采用算术平均值法计算4种类型指标的分值,以4种类型指标分值和的大小作为评价土壤全量养分丰缺的依据。应用该评价体系对福建沿海地区农业土壤养分状况进行评价,旨在为农业土壤区划提供参考依据。另外,文章还分析了影响土壤养分丰缺的因素,提出了土壤的pH值和SiO₂含量是影响土壤养分丰缺的重要因素,其次还有地质背景因素、人类活动叠加因素、沉积作用环境因素和气候环境因素等。

ASSESSMENT OF NUTRITIVE ELEMENTS IN AGRICULTURAL SOILS ALONG COASTAL REGIONS IN FUJIAN PROVINCE

Eco-geochemistry survey along coastal economic belts of Fujian Province was carried out by China Geological Survey and Fujian Province Government. The project investigated 54 elements in 4.34×104km² soils （top-soil and sub-soil） and shallow sea sediments （sea water depth<10m）. One column shaped surface soil sample （0～20cm depth） was collected in grid of 1km², 9 747 composite top-soils samples were consisted by 4 sub-samples. Total of 54 elements of composite soils were analyzed, and data of 30 nutritive and availability and toxic elements concentration could reflect status of nutrient and environmental quality of agricultural soils along coastal regions in Fujian Province.There are no criteria to assess availability of most nutritive elements in soils obtained by eco-geochemical survey except for pH, organic matter, nitrogen, phosphorus, and potassium in farming lands. The aim of the study were to calculate the sufficient and deficient thresholds of thirteen nutritive and beneficial elements in agricultural soils by integrated consideration of background value and standard deviation value as well as their ratio to element abundance of national soil. The study defined five thresholds: very deficient, deficient, feasible, sufficient, very sufficient by ≤0.5C _S, 0.5C _S～1.0C _S, 1C _S～1C _X, 1.0C _X～1.5C _X and >1.5C _X respectively.This study gave an integrated supply assessment system; 19 elements were classified into four key categories as soil property indicators（pH, SiO ₂ and organic matter）, grade-one nutritive elements（N,P and K ₂O）, grade-two nutritive elements（CaO,MgO,S and Cl） and trace nutritive or beneficial elements（Fe ₂O 3,Mn,Cu,Zn,B,Mo,Se,Na ₂O and Co）. These four categories were respectively given the highest scores with 30, 40, 15 and 15 according to their contribution to plant growth. The scores of each category could be achieved by calculating the average value of each indicator score. Then total element supply ability of agricultural soils was evaluated by sum of the four scores. The coastal region of Fujian Province was divided into several parts according to the total score. The result could be used to guide land-use plan.The result showed that the nutritive level of agricultural soils in the coastal region of Fujian Province was feasible and deficient as a whole; there were about 3/5 soils nutritive level as deficient or very deficient. Sufficient and very sufficient nutrient soils were highly cultivated paddy field and woodland distributed among town andresidential areas. The soils nutritive level being feasible were distributed along drainage basin such as river valley plain and marine bay plain; the soils nutritive level being deficient and very deficient were high sandy soils among laterite mesa, river valley basin plain and shore sandy soils.In this study, we analyzed the factors controlling the nutrient level of the investigated soils. It showed that pH value and SiO ₂ concentration were the main factors affecting soil nutritive supply ability, other factors were geological setting, human activity as well as climate and landscape conditions.