How to select forages: a short tutorial


Below is a short tutorial designed to introduce you to the selection tool and its various functions.

Case study

A research team working with smallholder farmers is seeking to test the value of introducing a forage legume into an existing crop-livestock production system in eastern Zimbabwe. Farmers currently grow maize as a cash crop and for local consumption and the diet of the dairy cattle is made up of maize stubble, native grass species, crop by-products and dairy concentrates. The team wants to select an herbaceous legume that can be used in an annual rotation with maize to provide high quality forage for dairy cattle and improve soil nitrogen status for the subsequent maize crop.
The smallholder farmer is from a region in Zimbabwe which is over 1000 m in elevation, has an average annual rainfall(AAR) of between 800-1000 mm, soils that are sandy, well drained and slightly acidic (approximately 5.5 pH) with poor unimproved fertility.
The underlined words above indicate key elements of the case study that have direct relevance to the selection tool.

Below is a step-by-step guide to a forage selection based on the 'Case Study':

  1. From the Tropical Forages 'home page' click on the Selection Tool and wait while the Features and Entities screen loads.
    Reminder: The selection tool requires a Java Virtual Machine installation. If you are unsure about this or you do not see a screen similar to the one below, then test your Java Virtual Machine capabilities → Click here


    Lucid selection tool

  2. The screen initially loads as shown above with Features Available & Features Chosen (empty) on the left and Entities Remaining (180) and Entities Discarded (0).
    The Features are listed to prompt logical thought about the conditions in your proposed forage system. For example, Intended forage use, LatitudeXAltitude and Rainfall are listed at the top due to their importance as defining features of a forage system.
  3. Start at the top of the list and select your Intended forage use. Click with the mouse on the + symbol to the left of the Feature called Intended forage use. This will open the list to reveal 15 potetial forage uses:

    Intended forage use

  4. Each Feature has an information icon to the left of the name. Clicking on the icon links to a glossary definition of that particular feature.

    Fact sheet iconGlossary or Fact sheet icon.

  5. Tick the following 'Intended forage use' boxes because they relate closely to the selected Case Study criteria:

    intended forage use selection

  6. As you make selections the Entities Remaining window shows the list of species that match the features chosen. In this case 42 species match the 3 chosen features.

    The selection tool works by 'matching all' rather than 'matching any' feature. In the selections you have chosen, the Entities match all of the Features rather than just any of the features. Alternatively, the species (entities) match 'ley or short term pasture' AND 'cut & carry' AND 'conservation' rather than 'ley or short term pasture' OR 'cut & carry' OR 'conservation'. This type of selection pattern is more discriminating, which contributes to more decisive selections. For more information on this selecting pattern read the relevant Lucidô help documentation - click here.

  7. Go to the 'LatitudeXAltitude' feature and open the feature set by clicking on the + symbol. According to the case study, select the 'Tropics, 1000 - 2000m ASL' feature. The list is reduced only slightly to 38 species that match the features chosen.

  8. The next feature in the list is 'Rainfall'. Click on the blank text entry box to the immediate left of the name 'Rainfall'. An entry box appears into which you can enter the rainfall range of 800 - 1000 from the Case Study.

    Rainfall range

  9. Please note that this does not reduce the list of species in the Entities Remaining window. This action does however reorder the list. This is an important feature of the selection tool. Initially the list of species is arranged in alphabetical order. As selections are made the list is reordered according to the species that best match the features selected. The closest matching species are arranged towards the top of the list. Scroll down the list of Entities Remaining and note the new order of species.

  10. Continue to tick the Features that best match the Case Study:

    More selections

  11. The above selections will have reduced the list down to 14 species. The final selections will hone this list even further. The case study suggests that the researchers require 'an herbaceous legume' to fit into an annual rotation with maize. Tick the following Features that match this criteria:

    Final selections

  12. The 'Entities Remaining' window lists 4 species that match the 'Features Chosen'. This is a small set would appear to be useful for further field-testing. It is important at this stage to closely review the fact sheets for each of these species to identify the specific characteristics of each species and their potential for further testing.

    Further 'Feature' selections can continue to be made, however this set of Features match the case study and provides a manageable list of species for further analysis. Note that the purpose of the selection exercise is not to try to get just a single species to match the Features. You should be seeking a small set of species in order to facilitate comparisons and further testing.

    The list below shows that Lablab purpureus, Mucuna pruriens, Stylosanthes hamata and Chamaecrista pilosa match the Features. Lablab and Mucuna are more accurate matches due to their position in the list.

    Entities remaining

A useful selection facility

At any stage in the selection process you may wish to compare species to see how they have been 'scored'. This can be done by clicking on the first species for the comparison, then while holding down the CTRL key click on the other species of the comparison. With the two (or more) species selected click on the compare button:

Compare species

The window that appears displays the Features that are scored differently for each species selected. This may be a useful facility when one reaches a small selection of species that requires further analysis.

Species differences