Evaluation of Soil Nutrient Content and Fertility in Main Dry Farming Regions of Laos

[Objectives]To evaluate the status of soil nutrient and fertility in main dry farming regions of Laos,and to explore differences in soil nutrient content between regions and crop types.[Methods]By collecting 57 soil samples in the 0-20 cm layer of the main dryland in southern and northern provinces of Laos.Soil pH,organic matter,total nitrogen,available nitrogen,available phosphorus,available potassium,exchangeable calcium,exchangeable magnesium and available zinc content were analyzed.[Results]The soil in the main dry farming regions of Laos was acidic,the overall fertility level was good,and the exchangeable calcium and magnesium contents were low.There were differences in soil nutrient content in the dry farming regions of southern and northern Laos.Drylands where cassava and maize were growed had higher fertility.[Conclusions]It is suggested to apply lime or alkaline fertilizer in the dry land with acid soil to increase soil pH and increase the supply of soil calcium and magnesium.Organic fertilizer should be applied to improve soil water retention capacity,and it is necessary to pay attention to the fertilization ratio of macroelements to balance fertilization.

Evaluation of Variable Rate Technology for Fertilizer Application in Permanent Pastures

This paper describes the field tests carried out to evaluate the new Vicon RS-EDW centrifugal fertilizer spreader, to be used in Precision Agriculture. The results of initial dynamic calibration tests showed a significant and systematic difference between the application rates of the two discs （about 20%）. This difference had to be corrected by the manufacturer that carried out the necessary changes to the electric actuators. The fertilizer spreader had good distribution homogeneity, considering different working velocities and different positions in the parcel. The pattern distribution curve for 18% super phosphate fertilizer led to an effective working width of 28 meters, with a coefficient of variation of 15%. The longitudinal test, under experimental working conditions led to a machine delay time of 6-7 seconds. The results show an actual fertilization application density between 74%-90% of that determined for each location. These results confirm that the spreader can be used to spread fertilizer differentially in the field.

Evaluation of a model recommended for N fertilizer application in irrigated rice

The response of rice to N fertilizer applicationhas shown that high rates of N application donot always ensure a proportional increase inyield due to high N losses. A model, ORYZA-0 was developed by ten Berge for designingoptimum N fertilizer management strategy inrice. We evaluated the performance ofORYZA-0 in Jinhua, Zhejiang Province. ORYZA-0 includes N uptakes, partition-ing of N among the organs, and utilization ofleaf N in converting solar energy to dry mat-ter. It can predict the amount and time of Nfertilizer application to achieve a maximumbiomass or yield combining with Price algo-rithm optimization procedure.

Analysis of Soil Fertility Evolution Characteristics in Main Eucalyptus Producing Areas of Guangxi from 1993 to 2018

The research aimed to explore the impact of long-term continuous planting management mode on soil fertility evolution of eucalyptus plantation in Guangxi and evolution characteristics of each soil fertility index,and establish a reasonable management method of eucalyptus plantation in Guangxi.Main production area of eucalyptus in Guangxi was taken as the research object,and the soil fertility quality of eucalyptus plantation in Guangxi from 1993 to 2018 was evaluated by means of fuzzy mathematics by selecting soil chemical properties such as p H,organic matter,total nitrogen,total phosphorus,total potassium,alkali-hydrolyzed nitrogen,available phosphorus and available potassium.The results showed that the soil p H value of eucalyptus plantation in Guangxi decreased from 4.83 to 4.63,a decrease of 4.14%.The contents of soil organic matter,total phosphorus,available nitrogen and available potassium all showed a significant decreasing trend.The soil fertility quality index( IFI) was between 0.475 and 0.613,and the overall fertility index was low.The soil of eucalyptus plantation in Guangxi showed a trend of acidification under continuous management during 1993-2018.In the actual production,it should pay more attention to soil improvement,advocate soil testing and reasonable fertilization,reduce the use of acid fertilizer,increase the application of organic fertilizer and slow release fertilizer,and ensure the ecological health and sustainable development of eucalyptus plantation.

Research and implementation of a universal workflow model to evaluate the soil fertility based on OGC Web Service

A method based on workflow technology and Open Geospatial Consortium(OGC)specification is proposed to establish a universal workflow conceptual model in the network environment.In this paper,the soil fertility evaluation conceptual model was developed as an evaluation method of soil fertility by analyzing the GIS-based fertility evaluation method and extracting the dynamic variable to verify the feasibility model.This validation process involves determining the instantiation of the conceptual model.The proposed conceptual model achieved the following goals.All data acquisition and processing functions were packaged into an OGC-compliant service model;these service models were organized into a processing chain in a certain order on the workflow platform by Petri-Net;the fertility evaluation was realized on the workflow platform by calling the processing chain.Results showed that processing functions and data can be shared in the network environment,and the network workflow model can be realized by the workflow technology.The successful implementation of fertility evaluation proved the feasibility of the network-based universal workflow conceptual model.In addition,the flexibility of our modeling method is demonstrated by reconstructing the workflow model.