Remote Sensing and Precision Agriculture Technologies for Crop Disease Detection and Management with a Practical Application Example

Remote sensing technology has long been used to detect and map crop diseases.Airborne and satellite imagery acquired during growing seasons can be used not only for early detection and within-season management of some crop diseases,but also for the control of recurring diseases in future seasons.With variable rate technology in precision agriculture,site-specific fungicide application can be made to infested areas if the disease is stable,although traditional uniform application is more appropriate for diseases that can spread rapidly across the field.This article provides a brief overview of remote sensing and precision agriculture technologies that have been used for crop disease detection and management.Specifically,the article illustrates how airborne and satellite imagery and variable rate technology have been used for detecting and mapping cotton root rot,a destructive soilborne fungal disease,in cotton fields and how site-specific fungicide application has been implemented using prescription maps derived from the imagery for effective control of the disease.The overview and methodologies presented in this article should provide researchers,extension personnel,growers,crop consultants,and farm equipment and chemical dealers with practical guidelines for remote sensing detection and effective management of some crop diseases.

DESIGN OF FARMLAND GIS FOR PRECISION AGRICULTURE

Precision Agriculture, also known as Precision Farming, or Prescription Farming, is a modern agriculture technology system, which brings ' precision' into agriculture system. All concepts of Precision Agriculture are established on the collection and management of variable cropland information. As the tool of collecting, managing and analyzing spatial data, GIS is the key technology of integrated Precision Agriculture system. This article puts forward the concept of Farmland GIS and designs Farmland GIS into five modules, and specifies the functions of the each module, which builds the foundation for practical development of the software. The study and development of Farmland GIS will propel the spreading of Precision Agriculture technology in China.

Weed Management in Rice-Wheat Cropping System through Remote Sensing： A Review

The productivity of the flee-wheat rotation of the Indo-Gangetie Plains is critical to India＇s food security. Severe weed competition resulting from the change in morphological characteristics of the modem high yielding varieties （HYV） led to intensive use of herbicides for weed control. Continuous and indiscriminate use of herbicides led to pollution as well as build up of resistant biotypes. This necessitates the need based use of herbicides. Identification of predominant weeds in rice-wheat cropping system through remote sensing and Geographic Information System （GIS） would help in reducing the load of herbicide on agro-eco system by reducing spray volume, application time and non-target spraying. This will help in developing site-specific weed management technique by geating only those areas with herbicide where weed densities exceed the economic threshold and may reduce application rate of herbicides in patches where weed densities are low. This paper reviews the literature on role of remote sensing for weed management not just to review their empirical findings, but to evaluate the role they have played and have the potential to play-in actual for weed management in flee-wheat cropping system （food bowl of India）.

High resolution aerial photogrammetry based 3D mapping of fruit crop canopies for precision inputs management

Rapid and accurate canopy attributes estimation is highly critical in fruit crops production management as this information can be used for canopy and crop load management as well as to develop nutrient/chemical prescription application maps.However,the existing ground based canopy sensing and attribute estimation methods are laborious and often involve complexity with field data collection and analysis.Manual methods can be subjec-tive as well.Therefore,this study explores aerial photogrammetry based method of tree–row–volume(TRV),leaf–wall–area(LWA),canopy volume(CV)and canopy cover(CC)esti-mation for grapevine and apple canopies.Remote sensing data was collected using a con-sumer–grade small unmanned aerial system(UAS)with an RGB imaging sensor flying at different flight altitudes i.e.,15 m(Ground sampling distance,GSD=0.45 cm pixel^(-1) at 65°sensor inclination),30 m(0.90 and 0.85 cm pixel^(-1) at 65°and 75°,respectively),45 m(1.35 and 1.27 cm pixel^(-1) at 65°and 75°,respectively)and 60 m(1.81 and 1.69 cm pixel^(-1) at 65°and 75°,respectively).Crop surface model(CSM)was derived from such data to esti-mate canopy height,width and foliage vigor,which are further used to estimate TRV,LWA,CV and CC.The ground measured and aerial imagery estimated TRV had a strong relation-ship with the data collected at the lowest GSD within grapevine canopies(R^(2)=0.77 at 0.45 cm pixel^(-1)as well as for apple canopies(R^(2)=0.82 at 0.90 cm pixel^(-1).Similar trends were observed for the LWA(R^(2)=0.77 and 0.86),CV(R^(2)=0.43 and 0.64)and CC(R^(2)=0.61 and 0.68)estimates for grapevine and apple canopies,respectively.Increasing GSD(≥0.45 cm pixel^(-1) in grapevine and≥0.90 cm pixel^(-1) in apple)resulted in a weak relationship between ground measurements and aerial imagery data-based estimates for grapevines(R^(2)=0.36)and apple canopies(R^(2)=0.39–0.78).Overall,the aerial flights with lower GSD and double grid missions with RGB imaging sensor in 65°orientation aided in the development of site–specific high–quality canopy vigor maps that can be used in precision crop inputs management related decision making.

Variable rate fertilizer application technology for nutrient management:A review

The efficient and effective application of fertilizers to crops is a major challenge.Conventionally,constant rate or equal dose of fertilizer is applied to each plant.Constant rate fertilizer application across entire field can result in over or under incorporation of nutrients.Fertilizer application is influenced by soil parameters as well as geographical variation in the field.The nutrient management depends on selection of nutrient,application rate and placement of nutrient at the optimal distance from the crop and soil depth.Variable rate technology(VRT)is an input application technology that allows for the application of inputs at a certain rate,time,and place based on soil properties and spatial variation in the field or plants.There are two approaches for implementing VRT,one is sensor based and another is map based.The sensor based approach;with suitable sensors,measures the soil and crop characteristics on-the-go calculating the amount of nutrients required per unit area/plant and micro controlling unit which uses suitable algorithms for controlling the flow of fertilizer with required amount of nutrient.In map based approach;Grid sampling and soil analysis are used to create a prescription map.According to the soil and crop conditions,the microcontroller regulates the desired application rate.The sensor-based VRT system includes a fertilizer tank,sensors,GPS,microcontroller,actuators,and other components,whereas the map-based system does not require an on-the-go sensor.Both approaches of VRT for fertilizer application in orchards and field crops are reviewed in this paper.The use of this advance technology surely increases the fertilizer use efficiency;improve crop yield and profitability with reduced environment impacts.