Producing vegetables for a market (or are vegetables an appropriate enterprise?)
2. The production environment
Peter Deuter and Jerry Lovatt, Department of Primary Industries and Fisheries, Queensland.
On this page:
Introduction
To be a successful vegetable grower it is just as important that you understand basic factors such as soil suitability, availability of irrigation and temperature effects on growth, production and quality.
Soil
Drainage is the most important soil factor. Soils must be capable of free drainage, especially when a significant rainfall event immediately follows an irrigation. Shallow soils (impervious subsoils within 80 cm of the surface) compacted soils (natural clay bars or machinery compaction) and uneven fields will allow waterlogging to occur.
Waterlogging will significantly reduce yield and quality of most vegetable crops. Levelling (e.g. laser levelling) and raised beds will help reduce these effects, however they will not be eliminated in poorly drained soils.
Lighter soils allow more timely operations such as cultivation, planting and ground rig spraying after rain. Rain will delay these operations on heavy black cracking clays.
Timeliness of operations is critical in vegetable production. The planting date will significantly influence the harvest date. Pest and disease monitoring, timely spraying (when necessary) and harvesting according to specification are operations which require careful planning. In many instances one day early or late for these operations will result in crop loss and/or quality downgrading.
Access to the field when ground based equipment is required for these operations is directly influenced by the drainage capabilities of the soil and the field layout.
Fertile soils are often an advantage, but vegetable nutrition management is relatively well understood, allowing low fertility soils to be used very successfully, particularly where all other factors are advantageous.
Irrigation
Up to 5 ML of water will be required for each hectare of crop. Efficient application and scheduling systems can reduce this to 2 or 3 ML/ha. The amount of irrigation required can be significantly reduced by effective rainfall (over 12 mm). Trickle irrigation systems, which require significant additional capital costs and management expertise, can reduce the irrigation water requirement to as low as 2 ML/ha for some crops.
Temperature
The effects of temperature on plant establishment, growth and product quality are significant (Table 1) and need to be carefully considered when selecting crops and production sites.
Low temperatures
Where frosts occur, their number, duration and severity will significantly influence plant growth and product quality.
For example, broccoli plants at early establishment can withstand a 'few' -2°C frosts, but growth and development are stopped by a -6°C frost. Light frosts (-2°C) will not significantly affect broccoli head quality, but anything colder than -6°C will reduce head quality significantly if they occur just before harvest.
Lettuce heads will be affected by light frosts, particularly if they occur on consecutive days. This is why broccoli can be grown in a few locations on the Darling Downs in the winter and lettuce cannot. Lettuce is successfully grown in the Lockyer Valley in winter because of the very low frost incidence in this district.
Frost sensitive crops are also adversely affected by periods of low temperatures. These conditions can be associated with low night temperatures and warm days, which produce low soil and air temperatures. These conditions result in much reduced growth of crops such as sweetpotatoes, sweet corn and most cucurbits. Low temperatures can also adversely affect flowering and fruit set in crops such as beans, tomatoes and most cucurbits.
High temperatures
High temperatures, particularly associated with rain, produce ideal conditions for diseases and a range of pests. Production costs and plant losses are usually higher under these circumstances and in most instances yield and quality are also reduced. Broccoli is a typical example where high spring and summer temperatures can significantly affect yield and quality, and also produce ideal conditions for pests and diseases. Where night time temperatures remain high after high daytime temperatures, the adverse effects on product quality are also increased. Highland areas around Toowoomba and Stanthorpe can successfully grow traditional winter crops in summer, because night temperatures are rarely high, even when daytime temperatures are occasionally in the low 30s.
Heat waves are the most difficult conditions for most crops to cope with. High water use will affect growth rates of most plants, but the downgrading of product quality is the most significant effect e.g. broccoli heads become loose and uneven and capsicum fruits are sunburned.
Rainfall
When it does rain in Queensland, significant amounts fall in summer with smaller amounts over the rest of the year. The 'driest' period is winter and spring. This, together with the effects of high temperatures, has influenced vegetable production away from the summer months in the major production districts of Queensland. Out-of-season rainfall events do occur and often have adverse effects on planting and harvesting schedules, product quality and yield.
Where summer production does occur it is generally driven by a specific market, and the location is usually in highland areas away from the coast e.g. tomato production on the Granite Belt and lettuce at Toowoomba.
Table 1. Temperature influences on selected horticultural crops
|
Crop |
Frost sensitivity |
Effects of low temperatures (0 to 5°C) |
Effects of high temperatures on product quality | ||
|
Young plants |
Established crops |
Short periods |
Heat waves | ||
|
Broccoli |
K/H |
H+ |
reduced growth |
(X) |
XX |
K/H = killed or severely damaged by heavy frosts (-6°C and below)
H+ = succession of severe frosts can have adverse effects on plant growth and/or product quality
K/L = killed or severely affected by light frosts (-1°C)
H A = severe frost (-6°C) can affect quality of produce
L = able to withstand a few very light frosts without severe damage
O = no effect or only limited damage
(X) = reduced production or marketability of product
XX = severe effects on growth, production, pollination and/or marketability
Prolonged wet weather will affect pollination of sweet corn and cucurbits and increase disease incidence in most crops.
Wet weather harvesting can result in soil compaction from harvesting machinery, particularly on heavy clay soils. Mechanically harvesting root crops is difficult or impossible, depending on soil and crop type, during wet weather.
In general, production in summer will be difficult where high temperatures occur, particularly in combination with rainfall. The vegetative phases of some crops such as sweet corn, rockmelon, capsicum and pumpkin are relatively unaffected, whereas the reproductive phases (early flowering to harvest) will be severely affected.
Production in winter will be difficult for most crops, where consecutive severe frosts occur.
Labour and mechanisation
Most horticultural crops have a high labour requirement, which may be assisted at particular stages in the growth and production cycle by mechanical aids (Table 2). There are no crops which can be completely mechanically harvested and transported in a similar fashion to grain and cotton.
Mechanical aids have not necessarily reduced the labour requirements for harvesting. However they have made labour more efficient, reduced handling damage in the harvested product and provided the opportunity to use longer and more flexible working hours.
Table 2. Comparison of labour requirements and mechanisation of selected vegetable crops
|
Crop |
Method of establishment |
Labour vs mechanisation | ||||
|
Seed |
Transplants |
Growth to harvest * |
Harvest ** | |||
|
Labour |
Mechanical aids |
Labour |
Mechanical aids | |||
|
Broccoli |
## |
## |
## |
## |
## |
## |
# = more #s indicate the importance of this technique for production in Queensland
* taking into account operations such as weed control, irrigation and fertiliser application, and pest and disease control.
** field harvesting (not including packaging, unless normally done in the field e.g. lettuce, cabbage and pumpkin).
Further information
Other DPI&F notes available in the 'Producing Vegetables for a Market' series include:
1. Successful horticultural enterprises
3. Matching crop requirements with the production environment
4. Sensible use of irrigation resources
5. Temperature requirements and limitations for a range of vegetable crops
DPI&F information and services
- To access DPI&F's information and services, Queensland residents can contact the DPI&F Business Information Centre on 13 25 23 for the cost of a local call. The Business Information Centre is open 8 am to 6 pm Monday to Friday (excluding public holidays); E-mail callweb@dpi.qld.gov.au. Non-Queensland residents phone (07) 3404 6999.
- Current national information on agricultural chemicals registered for use on all crops is available on the Infopest CD-ROM. Write to DPI&F, GPO Box 46, Brisbane, Qld 4001, E-mail infopest@dpi.qld.gov.au, visit the Infopest web page, or phone (07) 3239 3967 for further information.
Industry links
- Industry links is a page of links to various sites of interest to horticultural growers.
Information contained in this publication is provided as general advice only. For application to specific circumstances, professional advice should be sought. The Department of Primary Industries and Fisheries, Queensland has taken all reasonable steps to ensure the information in this publication is accurate at the time of publication. Readers should ensure that they make appropriate inquiries to determine whether new information is available on the particular subject matter.
Last reviewed 16 January 2008
