| In the paper we take Jiangyan county located in middle of Jiangsu province as example. Aiming at the problems such as soil nutrient evolution, unclear distribution and excessive fertilizer on production in the county scale, we comprehensively used classical statistics, geostatistics, global positioning system (GPS), geographic information system (GIS) technology, pocket PC(PDA) and Visual Basic, Embedded Visual Basic, principle and method of agricultural modeling science, decision support system (DSS) etc. to study the relationships of soil nutrient’s temporal dimension variation characteristics, space variability structure and with soil fertility relationship between different scales fluvo-aquic and paddy soils in the scope of the county in order to explore the effective analysis evaluation method of complex soil variability. The soil nutrient spatial database and related model were constructed, and thematic maps of multi-scale spatial distribution of soil nutrient and fertilization were also generated. Furthermore, the geographic information system of precise fertilization in rice at county scale based on Visual Basic and MapObjects, the Decision Support System of precise N application in rice at county scale based on PDA and Embedded Visual Basic, and the Decision Support System of rice precision cultivation in county scale based on Visual Basic and MapObjects were developed accordingly, which can provide soil nutrient data information query, precise fertilization decision support and intelligent tutoring service etc. for the department of agricultural production management and farmers. These results have important realistic significances and practical value for precise management of soil nutrient resources in county scales and in-depth implementation of rice precise fertilization technology, as well as, exploration of agricultural production potentiality and the realization of the goal of high yield, quality and efficient production in rice. The research technology was advanced, integrative, necessary and higher valuable for production application. The main results showed as follows:1. Classic statistics and GIS technology were used to research and prove up the law of temporal dimension evolution of soil nutrient in Jiangyan respectively from the county scale and the different scale of soil types, soil local types, the encryption points of soil types, zonally areas. The results were as followings:(1) Compared with1982, the organic matter (OM), total nitrogen (TN), available phosphorous (AP) in the soil nutrient of the county scale in2004were increased, but the pH was declined, alkaline decreased, the soil changed from the alkaline to neutral. That showed the fertility of the soil in the county scale was increased in the past20years. The contents of OM and available potassium (AK) ranked as high in the north and low in the south, which was similar to the situation in the year1982. However, AP showed without obvious law.(2) The OM, TN and AK in the paddy soil in2004were more than that in fluvo-aquic soil, but AP and pH were less. Compared with1982, the OM, TN and AP in14soil local types belonging to fluvo-aquic soil were increased in2004, while AK in12soil local types and pH in9soil local types were increased. Improved AP contents in2004were2.28times in1982. The content of AK in12soil local types where potash must be added, were less than80mg/kg, and there were still11soil local types belonging to alkali soil. Compared with1982, in19of21soil local types belonging to paddy soil, the OM was improved, AP in18soil local types and AK in14soil local types were increased, but for pH, there were a decline in15soil local types and rise in6soil local types. (3) According to the scale of encryption points, the OM, TN, AP and pH in2004were more than that in1982in both fluvo-aquic soil and paddy soil, while AK in fluvo-aquic soil was not obvious, but it declined in paddy soil. The variation coefficient (CV) of OM, TN and pH in2004were lower than that in1982, but the CV of AP and AK were larger in two years. In2004, the soil nutrient conditions and soil fertility in two kinds of soil types were improved than1982. The relative evenness of OM, TN and pH got better and soil fertility had a balanced development trend in different farmlands.(4) According to the four zonally areas from southern to northern, the OM, TN, alkali-hydrolyzable nitrogen (AHN) and AK took on a rise trend, but the pH was on the contrary and AP took on a trend of first gradually rise then decline. The comprehensive soil nutrient conditions such as OM, TN, AHN, AK in northern two zonally areas were better than that in southern, and AP level in soil were also good, which had a characteristics of soil with high yields. The contents of OM, TN, AHN and AK in southern two zonally areas were low, but the pH value was both high which belonged to alkaline soil, which not only need soil fertility buildup, and should generally increase potash and adjust pH value, and also increase phosphate in most southern zonally areas.2. The classic statistics, geostatistics and spatial interpolation technology were used to investigate the spatial variability of soil nutrient and fertilization strategy in fluvo-aquic soil and paddy soil in Zhangdian town and Shengao town of Jiangyan county. The results were as followings:(1) Judging from the spatial pattern, the contents of OM, TN, AHN, AP and AK were higher in paddy soils than those in fluvo-aquic soils whereas pH was indifferent. AP showed the largest variation coefficiency, whereas coefficiency of AK was the next and that of pH was the least between two types of soils. Except the fluvo-aquic soil pH, two types of soil nutrient elements all had the moderate spatial correlation. The results of geostatistics showed that the range of soil nutrient in paddy soil were higher than fluvo-aquic soil. The range of the observed items from maximum to minimum was respectively AP, TN, OM, pH, AK and AHN in fluvo-aquic soil, and AHN, TN, AK, OM, pH and AP in paddy soil. The measured soil fertility variables from each sampling spot represented20.4ha and36.2ha for fluvo-aquic and paddy soils respectively. This information was of critical importance and practically useful for designing county-scaled sampling units, and supplied a revise and material quantity for a mixed sample with10-33.3ha in plain where soil testing and formulated fertilization were demanded.(2) The contents of OM in Zhangdian area were not higher, and those were higher in middle zone but lower around zones, especially in North-West and North-East zone. The content of AP was higher in West than that in East. AP in7of104soil samples were seriously short, thus, more phosphate should be applied. AP in74of104soil samples were short, thus, proper phosphate should be added. However AP in23of104soil samples were not short, thus, phosphate may not be applied. The AK was lower and the variation coefficient was greatly changed. The potash fertilizer need not be applied only in10of104soil samples. In a word, OM, phosphate and potash fertilizer should be added in the soils in Zhangdian town to improve the crops yield.The contents of OM in Shengao area were a range of20-22.5g/kg mostly, which belonged to middle levels, but those in middle zones were more than27.5g/kg, even30g/kg, which belonged to high levels. The contents of AP in South-East zone were higher,1of130soil samples lacked AP seriously,58lacked,71lacked a little. The contents of AK in medium deflection to South-East were higher,51soil samples needed not be applied potash but79be added. In brief, the conditions of OM and AP in Shengao area were better, thus, they should be applied phosphate and potash making a distinction between different farmlands.3. Aiming at the more nitrogen applied in production and short of information technology of quantitative fertilizers, the experiments of orientation measured soil with a GPS machine covered in Jiangyan county and of8major soil local types were conducted. The relation models between OM and rice basal yields were established according to different soil local types, and the3parameter values for precise N application in rice which was suitable for application in Jiangyan, the spatial distribution map of soil nutrient and the map of precise N prescription in county scale were aslo made. On that basis, the geographic information system of precise fertilization in rice (V1.0) based on Visual Basic6.0and MapObjects2.2, which were suitable for cadres and peasants and owned proprietary intellectual property rights, were developed. The system consisted of Jiangyan survey, E-map, fertilizer decision, fertilizer models, fertilizer knowledge, et al. It had many functions such as information browse, map navigation, property query, decision support, learning tutorship and I/O, et al. It owned advantage such as usability, reliability and ease of use, which achieved system design goal and got the production application. As the assistant platform, the system can be used to supply an effective decision support and learning tutorship service for precise fertilization technology in rice, which had theoretical and practical dual meanings. As one of the main innovation points, the technology of nitrogen application reduced in rice at county scale including the system won the second prize of science and technology in2005in prefecture-level city of Taizhou.4. The decision support system of precise N application in rice at county scale based on PDA (Pocket PC) was developed based on the operating system of Windows Mobile and Embedded Visual Basic3.0and ArcGIS9.2and GPS navigation module. It integrated GPS real-time orientation, thematic map browse, decision support of precision N application according to soil group or soil local type, learning tutorship, system help and explain, and so on, furthermore, it owned basic function of decision support of precision N application in rice at county scale and had the good removability and portability and supplied a service of decision support for users in real time and in-place. The system combined the function module with geographic information, which can be easily operated in application precision nitrogen technology in rice according to the soil group and the soil local type. 5. Based on the developed the geographic information system of precise fertilization in rice, the software (V1.0) of Decision Support System of rice precision cultivation based on Visual Basic6.0and MapObjects2.2in county scale taking Jiangyan city as a case was developed. It had friendly surface, complete functions, abundant contents, strong updating and high graph productivity. The system integrated the latest productions of rice precise quantitative cultivation technology and it covered many contents such as proper layout, proper seed period, precision quantity of base seedling, decision support of precision N application, precise irrigation, precise plant protection, meteorological database and brainpower learning and so on. It also had base GIS spatial analysis functions such as an e-map navigation, GIS spatial information obtaining and so on. According to application of departments of crop cultivation and soil fertilizers in region, its functions was useable, dependability and ease of use, the users were very satisfied with it. The system had obtained the copyright in computer software (2008SR18123) registered by the State Copyright Administration. |
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