Intensive irrigation in semi-arid regions can lead to soil salinisation, which adversely affects agricultural productivity. The table below shows the relationship between soil salinity (measured as electrical conductivity, ECe\text{EC}_eECe) and the mean crop yield of a salt-sensitive variety of wheat:
| Soil salinity in dS m−1\text{dS m}^{-1}dS m−1 | Mean wheat crop yield in t ha−1\text{t ha}^{-1}t ha−1 |
|---|---|
| 2.0 | 7.84 |
| 4.0 | 6.52 |
| 6.0 | 4.81 |
| 8.0 | 2.95 |
Calculate the percentage change in the mean wheat crop yield when the soil salinity increases from 4.0 dS m−14.0\text{ dS m}^{-1}4.0 dS m−1 to 6.0 dS m−16.0\text{ dS m}^{-1}6.0 dS m−1. Give your answer to one decimal place and show your working.
