To calculate the number of seedlings required for 2 hectares of farmland with a spacing of \(2.5 \, \text{m} \times 4.0 \, \text{m}\):

1. Convert hectares to square meters
 \(1 \, \text{hectare} = 10,000 \, \text{m}^2\)
 2 \(\, \text{hectares} = 2 \times 10,000 \, \text{m}^2 = 20,000 \, \text{m}^2 \)

2. Calculate the area occupied by one seedling
 \( \text{Area} = 2.5 \, \text{m} \times 4.0 \, \text{m} = 10 \, \text{m}^2\)

3. Calculate the number of seedlings
 \( \text{Number of seedlings} = \frac{\text{Total area}}{\text{Area per seedling}} \)
 =\(\frac{20,000 \, \text{m}^2}{10 \, \text{m}^2} = 2,000 \, \text{seedlings} \)