What was it all about?

Increased climate variability is a key challenge the Australian vegetable industry faces. Technological solutions such as high-tech greenhouses can provide a level of control and certainty, however the expense of such structures is not always justified by returns for many vegetable crops, which can be relatively low value, space consuming, or simply not suited to full protective cultivation.

Low-cost protected cropping offers a compromise between the cost of high technology and the need to provide some protection to crops from adverse conditions. An initial review in the project identified shade structures, wind-breaks and floating row covers as the most potentially effective options for vegetable growers. These were subsequently trialled in a large number of growing sites around Australia.

Information was extended to growers through a series of workshops and presentations in key vegetable growing regions, and couple of fact sheets were produced (see the ‘act now’ section further down). Further information regarding the project trials and findings is outlined below and in the project’s full final research report.

Some of the findings…

Permanent shade houses and nets were found to be able to provide full protection from events such as hailstorms, but were unable to withstand cyclonic conditions in Western Australia. They did not greatly reduce crop temperatures when used as a top-only system. Although yield was unaffected by shading in these trials, it was noted that red shading resulted in darker leaf colour.

Capsicum plants grown in a retractable roof Cravo® house were significantly larger and healthier than similar plants grown outside, and would be expected to have greatly increased yield over an extended cropping period.

Using floating row covers for summer production of leafy greens demonstrated a number of potential issues with such systems. These included the difficulty of weed control as well as the potential for small insects such as aphids to multiply inside the protective cover if the sides were not kept well-sealed. Floating covers can improve seed germination if conditions are sub-optimal, but if the crop is well managed then there may be no benefit.

Under cold conditions, however, ‘fleece’ floating row covers can provide major benefits. These materials can significantly improve germination and growth, and protect crops from light frosts. Harvest of lettuce was brought forward one to two weeks using fleece materials. The lightest fabrics, which are also the cheapest, were sufficiently durable and gave results as good or better than more heavyweight fleeces. Capsicum plants grown under floating row covers had improved yield and better fruit quality.

Floating row covers enhanced plant growth, prevented sunburn and reduced temperatures around the plants during hot weather. They also proved effective at excluding Queensland fruit fly, a major pest of capsicums. The results were best when the row covers were installed early during development. The same effects, however, were not observed for chilli plants. No increases in either yield or quality were observed for cayenne or bird’s eye chillies grown with floating covers.

The large size of the plants and more frequent harvests also made use of floating covers problematic for chilli production. However, the materials did provide a significant benefit by excluding fruit fly, which may be important for growers practising integrated pest management.

ACT NOW

Download these fact sheets produced by the project:

• Blankets for vegetables: using frost cloths to protect plants from weather
• Managing insect contaminants in processed leafy vegetables: a best practice guide