No salt is recommended as this can affect the soil conditions and the kiwi roots.   There are moss killers on the market; however, if conditions remain the same the moss will come back. Moss is not bad. In fact it is a suitable low maintenance groundcover and deserves more credit. It grows in the shade in moist areas where grass cannot. It is okay to leave it. 

Otherwise, you did not mention the area and how you want to improve it.  If you want grass, improvements need to be made or the area should be converted to non-lawn, such as  groundcovers or other plantings suited to the site (shaded, damp, acidic, etc.). Converting the area may be cheaper, simpler, and more environmentally beneficial in the long-run over making repeated adjustments. Perhaps you can mulch the area and create a woodland garden. 

Here is our page on moss and lawn alternatives. 

Marian