The Soil Geochemistry Character Of Green Paddy Production Base In Qianguo Irrigation Area, Jilin Province

Soil is a place for root of paddy to grow, stretch and absorb the moisture and nutrients, where root growth of paddy only to meet the specific physiological and ecological requirements, can be normal and healthy. Therefore it is necessary to understand the relationship between paddy growth and soil conditions. In this paper, the eco-geochemical evaluation to standardized production base of green paddy was done through the identification of eco-geological environment and geochemical background of paddy growth in Qianguo irrigation area, in order to plan the layout of high-quality paddy cultivation and to develop the regional industrialization.In this paper, through carrying out soil geochemical survey combined with soil geochemical data of typical vertical profile, the following works were done to study the element distribution characteristics with the changes of soil type and physical- chemical nature: 108 each of soil samples and paddy root samples, and 99 soil vertical profile samples were collected systematically; the soil geochemical characteristics and the relationship between effective volume and full volume of soil elements in this area were analyzed to identify the geochemical factors that affect the distribution and the effectiveness of the soil elements; the relationship between geochemical environment and crop quality and yield were analyzed by means of extracting eco-geochemical information and using regression analysis, factor analysis and other methods, in order to identify the geochemical factors affecting the quality of paddy; the soil environmental quality was appraised based on the regional multi-purpose geochemical survey data and the GB15618-1995 environmental quality standards; the soil fertility in Qianguo irrigation area was evaluated through the analysis of element effective state, the abundance and deficiency conditions of useful elements and the factors affecting its effectiveness.This area is predominantly sandy soil, whose composition is mainly quartz and feldspar, and the clay minerals are mainly illite. The soil cation exchange capacity averages 22.43cmol·kg-1, which is low in the central and the northeast of this area. Overall weakly alkaline soil, pH values range from 5.37 to 8.78, with an average of 7.87 and increasing gradually from the northeast to southwest in space. The soil organic matter content averages 2.5%, with an overall high level but a very poor grade. Soil SiO2, Al2O3, Fe2O3, MgO, CaO, Na2O and K2O, the average contents are 62.74%, 12.07%, 3.40%, 1.21%, 4.52%, 2.19% and 2.70% separately. In the spatial distribution, SiO2, Al2O3, K2O, Na2O and Fe2O3 have the same law that is from northeast to southwest direction the contents decrease gradually with the distance increasing from the second Songhua River, while the MgO and CaO are just the opposite. This area the average of the total rare earth elements 175.85mg·kg-1, lower than the Chinese soil on average, slightly higher than the background value of Jilin Province, the distribution patterns are right-wing and appear Eu loss phenomenon after be normalized by carbonaceous chondrite. In space, the distributions of soil elements in this area can be divided into two categories: N, P, Mn, As, Pb and Hg contents increase with the distance increasing from the second Songhua river and K, B, Zn, Mo , Fe, Cu, Cr, and Cd contents are just the opposite. Elements in the vertical direction, the same distribution of differences, broadly divide into the following three categories: N, Cd and Hg accumulate on the surface and decrease gradually with the profile deeper; B, Cu, Zn, Fe, Mn, Cr, Pb and As are the opposite; P, K, and Mo contents decrease first and then increase with the profile deeper.The soil environmental quality in this area was valued in accordance with the maximum allowable concentration values of heavy metal elements for the second-level soil given by GB15618-1995, and the result shows that the most soil heavy metal pollution indexes in this area are low, the average pollution index of each element is less than 0.4 , and only As and Cd maximum values of the pollution index are slightly higher (0.92 and 1.39, respectively) and the remaining elements do not exceed the maximum value of 0.4; besides the average of comprehensive pollution index PN is also only 0.34 with the largest value 1.01, and only three samples are greater than 0.7, indicating that the soil environmental quality in this area is very good and basically in the first-level.Soil fertility evaluation of this area shows that the classification of the available K is the best, followed by cation exchange capacity, while the total nitrogen and available phosphorus are worse, especially in the northeast of this area; organic matter is the worst case. In this area soil fertility is relatively high in general. The central area is mostly rich in nutrient but short of Mo. In salting paddy soil and alluvial flooded paddy soil, the fertility is relatively low. The limiting fertility factor of salting paddy soil is the serious shortage of Mo. And the limiting fertility factors of alluvial flooded paddy soil are the lack of N, P and the low effective boron.The eco-geochemical environment in Qianguo irrigation area was evaluated comprehensively in this paper to explore the eco-geochemical methods and techniques of the green food base, and for further construction and use of standardized production base of green paddy, the following recommendations were made: N and P effectiveness in alkaline soil is the pressing issue of technique of fertilization, so it is should to break the conventional fertilization methods to research and develop a special fertilizer for alkaline soils; locally As and Cd should be concerned about the pollution problem, and it is recommended As and Cd polluted area using reasonable farming methods to strictly control pollutants into the crop absorption; soil lacking P, missing B, and lack of Mo are quite conspicuous need for balanced fertilization formula, targeted to ensure the normal growth of paddy and the increasing production and quality; the more cost-effective approach for soil nutrient supply is to improve the soil environment, release of soil nutrient resources, make full use of soil N and P resources, and apply organic fertilizer, in order to improve the potential agricultural productivity.