Castaño, J. P.

Giménez, A.

Olivera, L.

English

University of Kentucky

University of Kentucky UKnowledge International Grassland Congress Proceedings 21st International Grassland Congress / 8th International Rangeland Congress Monitoring Natural Pasture Status in Uruguay Using Satellite Images and a Soil Water Balance Model J. P. Castaño INIA, Uruguay A. Giménez INIA, Uruguay L. Olivera INIA, Uruguay Follow this and additional works at: https://uknowledge.uky.edu/igc  Part of the Plant Sciences Commons, and the Soil Science Commons This document is available at https://uknowledge.uky.edu/igc/21/5-1/37 The 21st International Grassland Congress / 8th International Rangeland Congress took place in Hohhot, China from June 29 through July 5, 2008. Proceedings edited by Organizing Committee of 2008 IGC/IRC Conference Published by Guangdong People's Publishing House This Event is brought to you for free and open access by the Plant and Soil Sciences at UKnowledge. It has been accepted for inclusion in International Grassland Congress Proceedings by an authorized administrator of UKnowledge. For more information, please contact UKnowledge@lsv.uky.edu. 　 Multifunctional Grasslands in a Changing World 　 Volume Ⅰ 　 瞯 ]681　 瞯Grasslands/Rangelands Resources and Ecology ——— Application of Information Technology in Monitoring and Managing Grasslands/Rangelands ResourcesMonitoring natural pasture status in Uruguay using satellite images and a soil water balancemodelJ . P . Casta鼻 o , A . Giménez , L . OliveraClimate and In f ormation Systems Unit (GRA S ) , National A gricultural Research Institute ( IN IA ) , A ndes 1365 p iso 12 ,Montev ideo , Uruguay . E‐mail :j castano＠ inia .org .uyKey words : natural pastures , IDSS , NDVI , soil water balanceIntroduction Cattle beef production in natural grasslands is the dominant agricultural production system in Uruguay . Monitoringand information about the current status of natural pastures is very important for planning and decision making at farm andgovernment level , to prevent cattle beef production losses . INIA , jointly with other national and international institutions , hasbeen developing an Information and Decision Support System ( IDSS) for monitoring the status of natural pastures in Uruguay .The IDSS is based on tools like remote sensing , Geographic Information Systems and models .Objectives The main objective of the IDSS is to offer almost real time information about the natural pasture status and the soilwater content in natural grasslands areas to support Government and cattle beef producers planning and decision making . Thecurrent IDSS is based on two main components : １ ) the Normalized Difference Vegetation Index ( NDVI) estimated with datacoming from the Advanced Very High Resolution Radiometer ( AVHRR) sensor , installed in NOAA satellites , and ２ ) a SoilWater Balance ( SWB) model for Uruguayan soils .Methodology AVHRR‐NDVI satellite data is supplied by the Climate and Water Institute from the Argentinean AgricultureResearch Institute . The NDVI is a normalized ratio of the red ( R ＝ ０ .５８‐０ .６８ mm) and near infrared ( NIR ＝ ０ .７２５‐１ .１ mm)spectral wavelengths . Monthly or １０‐day maximum values of AVHRR‐NDVI are estimated from daily data collected throughoutthe year . Monthly or １０‐day NDVI imagery creates a relatively cloud‐f ree data set by choosing NDVI pixels from days whenradiance interference is lowest and sun angle is highest with the assumption that the selected pixel is most representative ofactual ground reflectance ( Holben , １９８６ ) . Also , monthly NDVI anomaly imagery is created based on historic NDVI imagerydata set .The other tool used in the IDSS is the�Water Balance Model for Soils of Uruguay" developed by the INIA‐GRAS , Unit jointlywith the Water and Soils Department of the MGAP , and the National Direction of Meteorology of Uruguay . The modelestimates the soil water content by integrating the water precipitation data from ８５ climate stations , the atmospheric potentialwater demand , the vegetation transpiration , and the water holding capacity of each soil type . This model runs daily andgenerates ten‐day and monthly means outputs in map format of : water runoff ( mm) , and soil water content ( mm and％ ) .Results Monthly and １０‐day data and maps of NDVI and SWB are located and continuously updated in the GRAS Unit web sitehttp :/ / www .inia .org .uy / gras . A monthly agro‐climate report , including NDVI and SWB information , is also published in theGRAS Unit web site and sent by email to more than １０ ,０００ users .　 Figure 1 NDV I ( Feb‐2005) .Figure 2 Soil w ater content (mm)(Feb‐2005) .Conclusions NDVI and SWB componentsof the IDSS used in an integrated way ,have demonstrated to be a powerful toolto monitor natural pasture status , mainlythrough alerting drought situations( Figure １ and ２ ) . In these conditions ,drought affected areas have been detectedby both indices , but usually the SWBshowed them earlier than the NDVI ,probably due to the delayed response ofplants to the water deficit .ReferencesHolben , B . N . , ( １９８６ ) ,Characteristics of maximum‐valuecomposite images from temporalAVHRR data . InternationalJournal o f Remote Sensing , ７ ,１４１７‐１４３４ .Thornthwaite C .W . y Mather J .R .�Instructions and tables for computing potential evapotranspiration and the water balance ."Publ . in Climatology , １０ :１８１‐３１１ , １９５７ .-30 -31 -32 -33 -34 -351---~-_59 -58 -57 -56 -55 -54 -53 I- I I I I I 1- 1 0.25 0.3 0.35 04 045 0.5 0.55 0.6 1 -30.0 -30.5 -31.5 -32.0 -32.5 -33.0 -33.5 -34.0 -34.5 -35. 0'-~-,-e,. -59.0 -58.5 -58.0 -57.5 -570 -56.5 -56.0 -55.5 -55.0 -54.5 -54.0 -53.5 -530 I- I I I I I I I I b I 015 30 45 60 75 00 1051201351W165180rrrn 

Monitoring Natural Pasture Status in Uruguay Using Satellite Images and a Soil Water Balance Model

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Monitoring Natural Pasture Status in Uruguay Using Satellite Images and a Soil Water Balance Model

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