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Fertimaps: Characterization of intra-parcel variability using remote sensing techniques

Fertimaps: Characterization of intra-parcel variability using remote sensing techniques

Farmers know there are different productivity zones within their fields. Then, why do they manage them in the same way? Why do they apply the same fertilizer dose? Why do they sow the same seed dose? Now, thanks to satellite remote sensing, farmers can have maps delimiting different potential productive zones and make more appropriate management decisions for each one of them.

The development of the crop itself is the best indicator of the productive potential of a specific spot or area in a plot, as it integrates all factors affecting its growth, such as soil fertility, environmental and management conditions, etc.  Satellite image time series allow the characterization of crop development. Each image shows the status of the vegetation cover at satellite overpass time, on the basis of the values of vegetation indexes such as the NDVI.  If the image time sequence is dense enough, then a curve describing the dynamic of the crop temporal and spatial evolution in each pixel can be drawn. This trajectory in time defines crop growth. The numerical integration of this trajectory throughout the crop cycle, or in other words, the area under the curve allows quantitative characterization of biomass production at pixel scale.

What does MZM mean?

MZM stands for Management Zones Map. It always refers to a single crop unit, being understood as the total or partial farm surface covered by the same crop and managed in a homogeneous way. On a MZM, biomass values of each pixel are compared to the mean value of the total crop unit, which results in the graphic representation of areas characterized by their percentage deviation with respect to the said mean value. The results obtained can be compared to those obtained using other methodologies to draw variability or heterogeneity maps, both soil maps (electric conductivity maps) and production maps (performance monitoring maps installed in harvesters). Availability of image time series in the AgriSat ® system allows for the creation of these maps not only for the current season, but also for previous seasons. Operating over them as previously described, a map of biomass production can be obtained per season and unit of crop. The map of a single season is useful by itself, but the availability of maps of successive years in an easy and rapid way allows the discrimination of contextual factors which could have affected the yield in a particular year or crop, while allowing also to better establish spatial patterns of structural nature linked to intra-farm variations of agro-ecological conditions (soil properties, terrain characteristics, slope, orientation, microclimates, etc.).

What is the use of an MZM?

A Management Zones Map (MZM) defines and characterizes the variability of agricultural plots, depending on the crop and the productive approach, this information can be used for several purposes, such as:

  • Definition of areas which could be subjected to differential management.
  • Fertilization with variable doses: having an estimation of the total crop yield in the plot, or alternatively by establishing a yield goal for the next crop, the spatial distribution of yield can be done for further use for fertility diagnostic tasks, estimation of nutrients extraction and preparation of fertilization scheduling.
  • Delimitation of sampling areas for soil studies analysis.
  • Delimitation of areas for the follow-up of ripening and assessment processes of final quality, in woody crops like grapes and other fruit trees.
  • Delimitation of areas and sectors in the design of irrigation systems.
  • Classification of soil qualities for land valuation.

The first step towards variable rate fertilization

The quick and easy access to maps of the intra-plot variability invites farmers to rethink their usual practice of applying homogeneous fertilizer rate all over the plot. The information provided by an MZM, together with the agronomic knowledge of crop nutrition and the increasing availability of variable rate spreaders, opens the way to variable rate fertilization according to the space-time nutrient requirements of each parcel.

A promising future

Beyond these currently available amazing advances in crop management due to remote sensing, there is more to come: rapidly evolving technology and knowledge show the promise of a true revolution in the monitoring and management of crops. Space agencies and various industry consortia are planning to launch more space applications for the agricultural sector. Today’s farmers (not only the future farmers) cannot ignore these powerful tools that help them manage their farms more efficiently in both economic and environmental terms.


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