With the global population continuing to grow at a high pace, it is essential to optimize the use of water resources and to increase agricultural production in view of the prospect of having to feed 8 billion humans in 2030. Scientists have for many years been using remote-sensing satellite observations to improve water balance and farming yield assessment on large geographical scales (at the level of irrigated agriculture areas, catchment basins and so on).
Until quite recently, scientists had two different observation methods available for doing that: wide field-of-view sensors (TERRA-MODIS or SPOT-VEGETATION), which allowed daily observation of the entire globe but with a resolution on the kilometric scale, generally extending far over that of one parcel of crops, or decametre-scale-resolution sensors (SPOT, Landsat, ASTER), which can yield only one or two observations per month.
Since 2004, the Taiwanese satellite FORMOSTAT-2 has been in operation, combining the functional features of these two observation techniques, albeit without providing an exhaustive cover of the continents. It gives the possibility for daily observation of small areas of around 500 km² at a spatial resolution of about 8 metres.
Research conducted by an IRD team at the ‘Centre d’Etudes Spatiales de la Biosphère’ at Toulouse, using images taken by FORMOSAT-2, gave the opportunity to study two agricultural areas where farmers make extensive use of irrigation: the Tensift Plain around Marrakech in the centre of Morocco, and the Yaqui Valley in the State of Sonora in North-West Mexico. In these agricultural areas, irrigated cultivation of cereals, fruit trees and vegetables is practised over several thousand square kilometres.
This activity draws on limited water resources, mainly coming from precipitation received by the nearby mountain ranges: the Moroccan High-Atlas in the case of the Tensift Plain, the western Sierra Madre for the Yaqui Valley. Both regions have an arid climate: average rainfall is 200 mm per year. But the water demand is seven times as high (the potential evapotranspiration of the plant cover is about 1500 mm/year). It is therefore essential to portion off the water as equitably as possible, according to the needs of the different types of crops that make up the agricultural landscape.
For these two areas, the study demonstrated all the potential capabilities of the new imagery technique with its high spatio-temporal resolution. With the support of CNES, the satellite FORMOSAT-2 was used to obtain time series of images, from November to May of the following year, that is throughout one entire farming season, at the rate of one shot every 5 days. Processing of the resulting satellite data first helped compile land use maps (including crop rotation and succession patterns) with an excellent degree of discrimination between the different crop types.
The availability of a large set of observations also allowed detailed monitoring of the plant cover with time, achieved by determination of changes in reflectance, the proportion of the light reflected by the land surface. These measurements and associated vegetation indices gave the bases for determining the variables that describe the state of the soil-plant system such as the degree of land plant cover or the green leaf area index: a reliable index for vegetation, a figure below 0.15 corresponding to bare soil whereas one of over 0.70 characterizes a crop that is on the point of ripening (see the series of satellite images).
This detailed and practically continuous description of the plant cover made it possible to improve yield assessments and modelling of water transfer between soil, vegetation and atmosphere. The investigations run in Morocco on parcels of wheat in particular showed that evapotranspiration from the plant cover, the principal factor in water loss, could be evaluated with a margin of error of between 10 and 20%. Moreover, the plant biomass (dry above-ground phytomass) and grain yields could be estimated to an accuracy of about 25% at parcel scale.
In conclusion, this observation technique opens up the possibility to track the various successive operations (sowing, ploughing, irrigation, harvest and so on) effected as an agricultural season progresses. Making sets of such data available for local agencies responsible for agro-environmental management should facilitate the reorientation of irrigation rapidly towards the crop parcels where it is most needed. In addition, it also makes it possible to adapt and improve all the information and advice issued to farmers and thus enable them to make significant improvements to their cultivation practices.
Grégory Fléchet – DIC
1. This research work was conducted as part of the SudMed and MedMex programmes (IRD-CESBIO, Toulouse), in conjunction with the Faculté des Sciences Semlalia of Marrakech, the Office Régional de Mise en Valeur Agricole of Haouz (Morocco) and the University and Technological Institute of Sonora (Mexico). It was financed by the European Commission, Coopération Universitaire Franco-Marocaine and French national space research programmes (INSU and CNES). The FORMOSAT-2 image series were made available by the NSPO and processed in the framework of an agreement between the CNES, the NSPO and SPOT-IMAGE.
Grégory Fléchet | alfa
Climate change, population growth may lead to open ocean aquaculture
05.10.2017 | Oregon State University
New machine evaluates soybean at harvest for quality
04.10.2017 | University of Illinois College of Agricultural, Consumer and Environmental Sciences
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
20.10.2017 | Information Technology
20.10.2017 | Materials Sciences
20.10.2017 | Interdisciplinary Research