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Abstract The evaluation process of traditional land productivity is relatively complex， and the evaluation indices and results cannot display visually. With the development of geographic information system science， there are more and more studies on the GIS based land productivity evaluation. GIS system can combine the evaluation model with information system software， realizing the visual display of all the evaluation factors. In this paper， with the development process of GIS based management information system as references， the management information system for GIS based gravel mulched field productivity evaluation was designed and developed by combining with the SI model for gravel mulched field productivity evaluation. The system was developed under VB environment， integrated with MapInfo， and the evaluation results could be shown visually in the system windows.
Key words Gravel mulched field; Productivity; Evaluation model; Information system
Establishment of Gravel mulched Field Productivity Evaluation Model
The productivity evaluation model of gravel mulched filed in the arid area of central Ningxia was carried out from two aspects： natural conditions （PI） and social and economic conditions （TI）. The natural conditions of gravel mulched field productivity were evaluated using evaluation index PI model， and 10 influencing factors were selected as evaluation indicators. The social and economic conditions of gravel mulched field productivity were evaluated using evaluation index TI model， and 5 influencing factors were selected as the evaluation indicators. It could consult the local experienced melon growers and gravel mulched field experts to get the weights of natural conditions and the social an economical conditions in the evaluation. Moreover， expert grading method was used to get the comprehensive evaluation index SI model of gravel mulched field productivity[1].
PI model for evaluation on natural conditions of gravel mulched field productivity
According to the characteristics of PI model， combined with the actual productivity evaluation of gravel mulched field， 10 influencing factors were selected as the evaluation indicators， namely， organic matter content， available phosphorus content， available potassium content， total nitrogen content， soil mechanical composition， soil effective thickness， ground slope， soil pH， photo thermal condition， and water supply capacity.
The FAO productivity index model was used as the indicator model for the evaluation of natural conditions of gravel mulched field productivity. Geometric average was performed on the 10 selected factors[2]， obtaining the following： PI=10F1·F2·F3·F4·pH·Q·T·P·E·G
Where， F1 is soil organic matter content; F2 is soil available phosphorus content; F3 is soil available potassium content; F4 is soil total nitrogen content; Q is soil mechanical composition; T is soil effective thickness; G is ground slope; pH is soil pH value; P is the photo thermal condition （≥0 ℃ accumulated temperature）; E is the water supply capacity and terrain elevation.
TI model for evaluation on social and economic conditions of gravel mulched field productivity
The indicators for the evaluation of social and economic conditions of gravel mulched field productivity were selected in combination with the specific social and economic conditions of the evaluation zones， and the determined evaluation indicators were as follows： gravel mulched years （including 4 levels of 5 years， 5-10 years， 10-15 years and over 15 years）， irrigation degree （determined by the proportion of effective supplementary irrigation area）; chemicalization level （determined by the amount of fertilizer applied per unit of gravel mulched area （kg/hm2）， agricultural mechanization level （determined by the total power of agricultural machinery per unit of gravel mulched area （kw/hm2）， and the current population carrying capacity of cultivated land （a direct reflection of the social attributes of the land， generally expressed by population density）.
TI model was used as the evaluation model：
TI=∑ni=1W i·A i
Where， n is the number of evaluation elements; W i is the weight of each element; A i is the contribution parameter of each element.
W i was determined using the analytic hierarchy process to construct the judgment matrix， and the obtained weight of each index was as follows： gravel mulched years （N） of 0.263， irrigation degree （I） of 0.475， chemicalization level （C） of 0.110， agricultural mechanization level （M） of 0.090 and current population carrying capacity of cultivated land （P） of 0.055.
SI model for comprehensive evaluation of gravel mulched field productivity
The expert grading method was used to carry out the comprehensive evaluation on the natural conditions and social and economical conditions of gravel mulched field productivity， which could get the weights of PI index model and TI index model， thereby obtaining the comprehensive evaluation SI model for gravel mulched field productivity：
SI=0.8PI+0.2TI
Overall System Structure and Content The data information of gravel mulched field productivity evaluation was in scattered distribution， and the information processing mainly relied on manual mode. The heavy work and low efficiency made it not conducive to the display and comparative analysis of the entire evaluation process. The introduction of GIS technology to the various processes of gravel mulched field productivity evaluation could make the data presented in a more visual way. Consideration was given to the network， intelligent and practical development trend of the database in database design[3]. In this way， the Gravel mulched field productivity evaluation management information system （MIS） could systematically analyze the planting distribution of the gravel mulched field， and compare and analyze the differences between the evaluation factors， which could make the evaluation results more visual， thereby promoting the modernization of gravel mulched field productivity evaluation.
The gravel mulched field productivity evaluation MIS included 2 parts， namely， a series of TAB files of the evaluation factor query knowledge base and evaluation model result database. The specific system design is shown in Fig. 1.
System Function
In terms of the design of the system structure， the gravel mulched field productivity evaluation MIS mainly had 2 functions of evaluation factor data query and productivity evaluation.
Gravel mulched field productivity index information query
The query function of the gravel mulched field productivity evaluation MIS was mainly to query various TAB files located in the knowledge base， wherein the knowledge base contained the TAB files for each evaluation index layer in the gravel mulched field natural conditions evaluation， and the TAB files for each evaluation index layer in the gravel mulched field social and economical conditions evaluation， as well as other files. These files in the knowledge base made it convenient to query or open the layers of various evaluation index factors， so that the evaluation results were more visually displayed.
Gravel mulched field productivity evaluation
The gravel mulched productivity was evaluated from the 2 aspects of natural conditions and social and economical conditions， finally the comprehensive evaluation of the 2 aspects. The design of the system took the input and upgrade of evaluation model into consideration. The input and upgrade function of the system made it convenient to manage the spatial geographic location of the evaluation area and the data calculation of the evaluation model. The data input and upgrade of the evaluation model could be achieved through the 3 function keys of natural conditions evaluation， social and economical conditions evaluation and comprehensive evaluation. Then， the grade distribution map of productivity evaluation was shown in the map function window.
Others
The system called the MapInfo related function modules under the VB window， so the related functions of MapInfo could be conveniently implemented under the window of the system. For example， the "object" function could perform related point line operations on the layer; the "table" function could realize the maintenance of the data table structure; the "map" function could realize the production of related thematic maps; the "window" function could realize the display of multiple window， making it easy to manage various layers.
System Design Environment and Development Tools
The gravel mulched field productivity evaluation MIS mainly includes 4 parts， namely， information query， gravel mulched field natural conditions evaluation， social and economical conditions evaluation and comprehensive evaluation. The system is developed under the Chinese version of Microsoft Visual Basic 6.0 and integrated with MapInfo module， and finally compiles and generates EXE file for system calls. The system is developed and operated on the Chinese Windows XP operating platform.
System Development， Operation and Maintenance
Development of main system functions
（1） System main interface development.
The main interface of the system mainly used the menu editor function function of VB to edit and implement various functions of the system， as well as to call the corresponding module. For example， the following code could be used to realize the call of the form bar of the workspace， and the design of the main interface of the system is as shown in the following Fig. 2.
（2） Visual query function development.
The visual query was mainly realized by using various TAB files in the knowledge base. After entering the system interface， the user could get theaccess to the visual query window by clicking the "OK" button after selecting the required map or table， thereby achieving the 3 D display of the various evaluation indicators.
（3） Productivity evaluation function development.
The data input and update mainly included the updating， adding and deleting functions of the database tables， which made it easy to manage the table data in the evaluation model， and the specific design is shown in Fig.3. System operation and maintenance
In the VB development environment， the system could generate .EXE files after successful program debugging， which could be operated independently under the Windows XP operating system for evaluation indicator query and database information input and update. The maintenance of the system was mainly to update and modify the files in the knowledge base at regular intervals in time， and then release them to the system users， so as to ensure the correctness and practicability of the system knowledge. The operating interface of the system is shown in Fig. 4.
Conclusion
On the basis of summarizing the current research on GIS based management information system， the gravel mulched field productivity evaluation MIS has been developed and designed in combination with the practices of gravel mulched field productivity evaluation. The system design mainly gives consideration to the 2 functions of visual information query and productivity evaluation. The gravel mulched field productivity evaluation MIS is composed of a series TAB files of the evaluation factor query knowledge base and evaluation model results database. The system is developed， debugged and operated in the Chinese version of Microsoft Visual Basic 6.0， and finally generates independent and executable .EXE files， which is convenient to operate for users.
References
[1] WANG B， TIAN JC. GIS based productivity evaluation of gravel mulched field in Ningxia[J].Water Saving Irrigation.2012.0（8）：69-73.
[2] Food and Agriculture Organization of the United Nations. Land Classification and Classification Law[M]. Rome： Food and Agriculture Organization of the United Nations， 1976.
[3] TIAN JC. Research on intelligent decision support system for water saving irrigation in arid area and irrigation disposition in pumping irrigation area[D]. Wuhan： Wuhan University of Hydraulic and Electric Engineering， 1998.
Key words Gravel mulched field; Productivity; Evaluation model; Information system
Establishment of Gravel mulched Field Productivity Evaluation Model
The productivity evaluation model of gravel mulched filed in the arid area of central Ningxia was carried out from two aspects： natural conditions （PI） and social and economic conditions （TI）. The natural conditions of gravel mulched field productivity were evaluated using evaluation index PI model， and 10 influencing factors were selected as evaluation indicators. The social and economic conditions of gravel mulched field productivity were evaluated using evaluation index TI model， and 5 influencing factors were selected as the evaluation indicators. It could consult the local experienced melon growers and gravel mulched field experts to get the weights of natural conditions and the social an economical conditions in the evaluation. Moreover， expert grading method was used to get the comprehensive evaluation index SI model of gravel mulched field productivity[1].
PI model for evaluation on natural conditions of gravel mulched field productivity
According to the characteristics of PI model， combined with the actual productivity evaluation of gravel mulched field， 10 influencing factors were selected as the evaluation indicators， namely， organic matter content， available phosphorus content， available potassium content， total nitrogen content， soil mechanical composition， soil effective thickness， ground slope， soil pH， photo thermal condition， and water supply capacity.
The FAO productivity index model was used as the indicator model for the evaluation of natural conditions of gravel mulched field productivity. Geometric average was performed on the 10 selected factors[2]， obtaining the following： PI=10F1·F2·F3·F4·pH·Q·T·P·E·G
Where， F1 is soil organic matter content; F2 is soil available phosphorus content; F3 is soil available potassium content; F4 is soil total nitrogen content; Q is soil mechanical composition; T is soil effective thickness; G is ground slope; pH is soil pH value; P is the photo thermal condition （≥0 ℃ accumulated temperature）; E is the water supply capacity and terrain elevation.
TI model for evaluation on social and economic conditions of gravel mulched field productivity
The indicators for the evaluation of social and economic conditions of gravel mulched field productivity were selected in combination with the specific social and economic conditions of the evaluation zones， and the determined evaluation indicators were as follows： gravel mulched years （including 4 levels of 5 years， 5-10 years， 10-15 years and over 15 years）， irrigation degree （determined by the proportion of effective supplementary irrigation area）; chemicalization level （determined by the amount of fertilizer applied per unit of gravel mulched area （kg/hm2）， agricultural mechanization level （determined by the total power of agricultural machinery per unit of gravel mulched area （kw/hm2）， and the current population carrying capacity of cultivated land （a direct reflection of the social attributes of the land， generally expressed by population density）.
TI model was used as the evaluation model：
TI=∑ni=1W i·A i
Where， n is the number of evaluation elements; W i is the weight of each element; A i is the contribution parameter of each element.
W i was determined using the analytic hierarchy process to construct the judgment matrix， and the obtained weight of each index was as follows： gravel mulched years （N） of 0.263， irrigation degree （I） of 0.475， chemicalization level （C） of 0.110， agricultural mechanization level （M） of 0.090 and current population carrying capacity of cultivated land （P） of 0.055.
SI model for comprehensive evaluation of gravel mulched field productivity
The expert grading method was used to carry out the comprehensive evaluation on the natural conditions and social and economical conditions of gravel mulched field productivity， which could get the weights of PI index model and TI index model， thereby obtaining the comprehensive evaluation SI model for gravel mulched field productivity：
SI=0.8PI+0.2TI
Overall System Structure and Content The data information of gravel mulched field productivity evaluation was in scattered distribution， and the information processing mainly relied on manual mode. The heavy work and low efficiency made it not conducive to the display and comparative analysis of the entire evaluation process. The introduction of GIS technology to the various processes of gravel mulched field productivity evaluation could make the data presented in a more visual way. Consideration was given to the network， intelligent and practical development trend of the database in database design[3]. In this way， the Gravel mulched field productivity evaluation management information system （MIS） could systematically analyze the planting distribution of the gravel mulched field， and compare and analyze the differences between the evaluation factors， which could make the evaluation results more visual， thereby promoting the modernization of gravel mulched field productivity evaluation.
The gravel mulched field productivity evaluation MIS included 2 parts， namely， a series of TAB files of the evaluation factor query knowledge base and evaluation model result database. The specific system design is shown in Fig. 1.
System Function
In terms of the design of the system structure， the gravel mulched field productivity evaluation MIS mainly had 2 functions of evaluation factor data query and productivity evaluation.
Gravel mulched field productivity index information query
The query function of the gravel mulched field productivity evaluation MIS was mainly to query various TAB files located in the knowledge base， wherein the knowledge base contained the TAB files for each evaluation index layer in the gravel mulched field natural conditions evaluation， and the TAB files for each evaluation index layer in the gravel mulched field social and economical conditions evaluation， as well as other files. These files in the knowledge base made it convenient to query or open the layers of various evaluation index factors， so that the evaluation results were more visually displayed.
Gravel mulched field productivity evaluation
The gravel mulched productivity was evaluated from the 2 aspects of natural conditions and social and economical conditions， finally the comprehensive evaluation of the 2 aspects. The design of the system took the input and upgrade of evaluation model into consideration. The input and upgrade function of the system made it convenient to manage the spatial geographic location of the evaluation area and the data calculation of the evaluation model. The data input and upgrade of the evaluation model could be achieved through the 3 function keys of natural conditions evaluation， social and economical conditions evaluation and comprehensive evaluation. Then， the grade distribution map of productivity evaluation was shown in the map function window.
Others
The system called the MapInfo related function modules under the VB window， so the related functions of MapInfo could be conveniently implemented under the window of the system. For example， the "object" function could perform related point line operations on the layer; the "table" function could realize the maintenance of the data table structure; the "map" function could realize the production of related thematic maps; the "window" function could realize the display of multiple window， making it easy to manage various layers.
System Design Environment and Development Tools
The gravel mulched field productivity evaluation MIS mainly includes 4 parts， namely， information query， gravel mulched field natural conditions evaluation， social and economical conditions evaluation and comprehensive evaluation. The system is developed under the Chinese version of Microsoft Visual Basic 6.0 and integrated with MapInfo module， and finally compiles and generates EXE file for system calls. The system is developed and operated on the Chinese Windows XP operating platform.
System Development， Operation and Maintenance
Development of main system functions
（1） System main interface development.
The main interface of the system mainly used the menu editor function function of VB to edit and implement various functions of the system， as well as to call the corresponding module. For example， the following code could be used to realize the call of the form bar of the workspace， and the design of the main interface of the system is as shown in the following Fig. 2.
（2） Visual query function development.
The visual query was mainly realized by using various TAB files in the knowledge base. After entering the system interface， the user could get theaccess to the visual query window by clicking the "OK" button after selecting the required map or table， thereby achieving the 3 D display of the various evaluation indicators.
（3） Productivity evaluation function development.
The data input and update mainly included the updating， adding and deleting functions of the database tables， which made it easy to manage the table data in the evaluation model， and the specific design is shown in Fig.3. System operation and maintenance
In the VB development environment， the system could generate .EXE files after successful program debugging， which could be operated independently under the Windows XP operating system for evaluation indicator query and database information input and update. The maintenance of the system was mainly to update and modify the files in the knowledge base at regular intervals in time， and then release them to the system users， so as to ensure the correctness and practicability of the system knowledge. The operating interface of the system is shown in Fig. 4.
Conclusion
On the basis of summarizing the current research on GIS based management information system， the gravel mulched field productivity evaluation MIS has been developed and designed in combination with the practices of gravel mulched field productivity evaluation. The system design mainly gives consideration to the 2 functions of visual information query and productivity evaluation. The gravel mulched field productivity evaluation MIS is composed of a series TAB files of the evaluation factor query knowledge base and evaluation model results database. The system is developed， debugged and operated in the Chinese version of Microsoft Visual Basic 6.0， and finally generates independent and executable .EXE files， which is convenient to operate for users.
References
[1] WANG B， TIAN JC. GIS based productivity evaluation of gravel mulched field in Ningxia[J].Water Saving Irrigation.2012.0（8）：69-73.
[2] Food and Agriculture Organization of the United Nations. Land Classification and Classification Law[M]. Rome： Food and Agriculture Organization of the United Nations， 1976.
[3] TIAN JC. Research on intelligent decision support system for water saving irrigation in arid area and irrigation disposition in pumping irrigation area[D]. Wuhan： Wuhan University of Hydraulic and Electric Engineering， 1998.