• Farmers use various strategies to increase the?yield?of their crops or livestock. These strategies include:
  • Reducing energy losses?from crops to?other organisms?by removing?pests
  • Reducing energy losses?from livestock through?respiration?by restricting their?movement?and keeping them?warm?(i.e. indoors)

   

• Increasing yield refers to:
  • Increasing the?net primary production?of crops
  • Increasing the?net production?of livestock

   

Percentage Yield

• There are?two?types of yield:
  • Theoretical yield?is the amount (of crop or livestock biomass) that is theoretically?possible?to produce, given the?ideal conditions
  • Actual yield?is the amount (of crop or livestock biomass) that is actually produced, given the?actual conditions?the crops or livestock are kept under

   

• The percentage yield is the?actual yield?achieved, given?as a percentage?of the?theoretical yield?possible
• Percentage yield can be calculated using the following equation:

% yield = (actual yield ÷ theoretical yield) × 100

Step 1: Write out the equation and substitute in the known values

% yield = (actual yield ÷ theoretical yield) × 100

% yield = (50 ÷ 200) × 100

Step 2: Calculate the % yield

% yield = 0.25 × 100

% yield = 25%

Step 3: Explain why the percentage yield is not 100%

• • The maximum theoretical yield (or maximum theoretical net primary production) can only be obtained if the conditions are perfect
    • This includes abiotic factors, such as temperature, water availability and light availability
    • This may also include biotic factors, such as a lack of pest species competing with the crop

     

  • The perfect conditions are very difficult to achieve for crops (especially those grown outdoors) and so the percentage yield is often well below 100%

   

Step 1: Rearrange the equation

% yield = (actual yield ÷ theoretical yield) × 100

Actual yield = (% yield × theoretical yield) ÷ 100

Step 2: Substitute in the known values and calculate the actual yield

Actual yield = (90 × 15,000) ÷ 100

Actual yield = 1,350,000 ÷ 100

Actual yield = 13,500

Step 3: Give the appropriate units

The actual yield of the herd of cattle is 13,500 kg