How are productivity maps used?

From Wikiagro.com
Revision as of 10:28, 13 September 2012 by Ed (Talk | contribs)

Jump to: navigation, search

{{#customtitle:How are Productivity maps used?|How are Productivity maps used?}}

Applications & Benefits

Productivity maps are a reliable tool to understand variability within a field or management unit and support management decisions. By understanding within field variability, there are different  ways that these maps can be used:

Analyze variability and evaluate management alternatives

Understanding the variability within a field is the main application of productivity maps, based on crop history and remote sensing. This allows to evaluate diverse decisions regarding how to address and manage the causes for variability. The following items are examples of the types of decisions that can be taken:

  • Modify the uses of the field and/or management units
  • Select areas for on-farm research
  • Support renting/lease decisions.
  • Selecting soil sampling points
  • Variable rate seed and fertilizer application
  • Selecting sample sites for leaf / plant sampling
  • Selecting moisture probe points
  • Irrigation scheduling
  • Deciding where to dig soil profile pits
  • Drainage system and points
  • Crop rotation strategies
  • Hybrids selection by management zone
  • Monitoring effect of irrigation on crop

//put picture of irrigation issues - credit to Francis 

Directed sampling

Productivity maps provide a viable alternative to more data intensive methods, such as grid sampling or on-site surveys, reducing time and costs to diagnose the causes of variability. According to different experiences, the number of sampling points can be reduced from 6 to 1, or 10 to 1, for instance, using methods of grid sampling and directed sampling based on productivity maps.

One of the main uses of these maps is to use them as a starting point for field visits, validating on site the different zones, and with information from the farmer and the consultant, characterize the different types of management zones.

//put figure of grid & directed sampling

Variable Rate prescription

Specifically related with the use of crop inputs (seed, fertilizes, agrochemicals), it's possible to use productivity maps to generate prescription maps, in order to save inputs in areas with low yield potential and incresase inputs in areas with high potential.

//put figure of productivity map → to seed or =variable rate fertilizer


The decision making process

Productivity maps can guide the manager or consultant, regarding yield differences in their fields. These differences can be validated in the field, management zones delineated, and then take management decisions. The decision making process has three main activities:

a. Recognize the differences - generate the productivity map

In this step, the productivity map is generated to recognize variability within fields. This entails a 2-step process, where we first analyze regional limiting factors, and then carry out an analysis in each field based on remote sensing, and crop history. This process is analyzed in//put link

//photo of variability / productivity map

b. Field visit - Characterize management zones

//put figure of sampling by TO

In this step, Productivity zones are validated in the field, to derive management zones.

It's recommended to work jointly with the involved parties, such as the farmer, managers, or consultants: visiting the field with a GPS, evaluating differences shown in the productivity maps recognizing causes for variability, and characterizing management zones. One important aspect is that the regional limiting factors can be taken into account for management zones characterization. Directed soil and/or tissue sampling can be carried out to gather additional data and fine tune recommendations. Productivity maps classes can also be grouped to create management zones As a result of this step, management zones are defined, and attributed, which is the basis to evaluate management alternatives. //figure of thomas → productivity maps → management zones


c. Take management decisions

In this final step, gathered information is analyzed to take management decisions. These can be grouped in two major areas:

  • General decisions, that do not require Variable Rate Technology (VRT).
    This would involve for instance, dividing the fields in broad areas, where different decisions are implemented, such as adopting a crop rotation strategy, hybrid selection, seeding dates, drainage or irrigation management, etc. .
  • Creating Prescription maps for Variable Rate application, optimizing inputs according to the field potential.
    This would include for instance variable rate application of P, N, seed, or micronutrients.


//put figures of macroambientes / microambientes...


Limitations

There are a couple of limitations to consider:

  • Imagery availability on the right dates can be a limiting factor in certain occasions, in most cases the available image banks can provide the historical information needed. This link has additional information on using the right imagery dates//put llink
  • Productivity can be evaluated within fields only, and not between fields. The main reason is that in a given farm, fields may have at the same time different types of crops or uses. Thus, NDVIs from different fields cannot be compared. For this reason different images are selected for different fields. As a conclusion, productivity zones maps should only be used to compare variability within fields, but not as a means of comparison between different fields.