Why shift from a "clean" plantation to a more diverse plantation?

It has been standard practice in macadamias to keep the plantations "clean" and park like.

This has a visual appeal but may not be the best practice for pest management, soil health and biodiversity.

A more plant diverse inter row, has many benefits for increasing beneficial arthropods and pollinator populations which in turn makes the crop more resistant to pest incursion.
A more vigorous and diverse inter row can also:

• improved nutrient cycling,
• increase soil carbon levels,
• provide better water penetration and reduce runoff
• improve water holding capacity
• nurture a more diverse and abundant soil borne microfauna.

Methods to do so:

• Reduce mowing when possible.
• Alternate row mowing, not mowing the whole block at once.
• or just mow half a row at a time,
• Leave Mohawk central nature strips when possible
• Light cultivation of strips will allow seed bank to germinate
• Aerator alone may enable seed bank seeds to germinate
• Discs to disturb soil and germinate seed bank
• Rotary hoe or power harrow to prepare seed bed for sowing
• Direct drill seeding into worked ground or existing sod.

See also:
Alternate mowing
Cultivation
Direct seeders - See the video
Equipment
Seeds to Plant

Just by leaving part of the row longer than the rest will provide more homes and food for beneficial and pollinators. If grasses are allowed to get to flowering this allone is a great improvement on a contantly low mown inter row.

A light cultivation may enable the seed bank to germinate. Many so called "weeds" are good for beneficials. Including cobblers pegs, billygoat weed, milk thistles...

The next step is to deliberately plant seeds. Seed selection will depend on the aim of the exercise. For beneficials, plants that produce pollen, nectar and/or are hosts for insects like aphids are the best. You may also want to break up a hard pan in which case you want some deep rooted species like oil seed or tillage radish, or if want to add to add nitrogen select legumes, and for organic matter go with various forage crops.

Brassicas provide many flowers that are good for pollinators and parasitoids and may also harbour aphids which provide food for ladybirds, lacewinds and hover flies.

Alyssum produces a lot of nectar which is very attractive to bees and parasitoids

Tillage radish is great for breaking up compaction and produces a lot of organic matter

Vetch is great for building up nitrogen and soil carbon.