Site selection and preparation
A soil test should be taken before land preparation starts so that soil amendments such as gypsum can be broadcast. Bananas will grow on most soil types available for horticulture along the Gascoyne River.
Bananas will not perform as well away from the river on the Delta land system. This system is characterised by saltbush and other halophytic shrubs. The soils there are sodic and require applications of gypsum and compost at cost prohibitive rates.
Better soils will also benefit from adding compost or mulch to improve soil physical, chemical and biological fertility. Correct soil preparation will require deep ripping to break hardpans and allow for improved root penetration. Test for nematodes before planting if there is a history of bananas in that patch.
Pre-planting cover crops
High plant density is not favourable for inter-row cover cropping, however cover crops can assist with establishing new patches. With minimal irrigation or if adequate winter rainfall persists, grass or legume cover crops such as oats, sorghum or vetch can be grown and then sprayed out at the vegetative stage with a knockdown herbicide. Banana rows can then be planted into the dry mulch. The dry matter will assist in dust and weed suppression until the banana canopy closes.
Spacing
Plant spacing effect:
- Bunch size and grade – planting too close will reduce bunch and fruit size.
- Bunch cycling – planting too close will reduce rate of emergence of follower suckers while the parent plant will be slower bunching, with slower filling bunches.
- Disease problems – closer plantings have reduced air circulation, increasing fungal leaf diseases including Deightoniella, however these are usually not a major concern.
- Cooling – closer planting shades the inter-row, cooling the patch in summer.
The two most common planting systems result in plant densities of 3333 plants per hectare.
- Plant in rows 3 metres apart with plants 3 metres apart, leaving three suckers per site for the first ratoon crop and then maintaining that density.
- Plant in rows 3 metres apart with plants 1 metre apart, leaving one sucker per site for the first ratoon crop and then maintaining density.
The close planting system requires more planting material but results in significantly higher yields in the parent crop.
The 2009 to 2012 trials of bananas under netting at the Gascoyne Research Station have led expert Dr John Robinson to the following conclusions:
“Anticipating the use of a more efficient net structure, I would propose 2200‑2500 plants per hectare on a rectangular single row arrangement in which the in-row banana spacing is 1.5m or more. In the open field, where extra canopy protection is needed from wind and heat stress, I would propose between 2500 and 3000 plants per hectare but also on a rectangular, single row and single sucker arrangement.”
This lower density is being trialled by some growers.
Planting time
Two planting times are used ‑ August to November, and February to March. Most plantings are made from August to November. This gives good establishment and plants become well advanced (2.5 to 3.0m high) before the slow growth period of winter. It takes about 13 months from planting to first harvest if the planting date is September to December, but can be 16 months or more if planting occurs from January to March (DAFWA trials).
Autumn plantings are used in an attempt to have the first crop harvested in winter and spring months when prices are traditionally higher. Trial results at the Gascoyne Research Station have shown that a high density crop planted in March reaches peak harvest in September to November. Growth after March is slow and weed control over winter can be costly.