Irrigation is the artificial application of water to land for the purpose of agricultural production. Effective irrigation will influence the entire growth process from seedbed preparation, germination, root growth, nutrient utilisation, plant growth and regrowth, yield and quality.
The key to maximising irrigation efforts is uniformity. The producer has a lot of control over how much water to supply and when to apply it but the irrigation system determines uniformity. Deciding which irrigation systems is best for your operation requires a knowledge of equipment, system design, plant species, growth stage, root structure, soil composition, and land formation. Irrigation systems should encourage plant growth while minimising salt imbalances, leaf burns, soil erosion, and water loss. Losses of water will occur due to evaporation, wind drift, run-off and water (and nutrients) sinking deep below the root zone.
Proper irrigation management takes careful consideration and vigilant observation.
Irrigation and its Value
Irrigation allows primary producers,
- to grow more pastures and crops
- to have more flexibility in their systems/operations as the ability to access water at times when it would otherwise be hard to achieve good plant growth (due to a deficit in soil moisture) is imperative. Producers can then achieve higher yields and meet market/seasonal demands especially if rainfall events do no occur.
- to produce higher quality crops/pastures as water stress can dramatically impact on the quality of farm produce
- to lengthen the growing season (or in starting the season at an earlier time)
- to have ‘insurance’ against seasonal variability and drought.
- to stock more animals per hectare and practice tighter grazing management due to the reliability of pasture supply throughout the season
- to maximise benefits of fertiliser applications. Fertilisers need to be ‘watered into’ the ground in order to best facilitate plant growth.
- to use areas that would otherwise be ‘less productive’. Irrigation can allow farmers to open up areas of their farms where it would otherwise be ‘too dry’ to grow pasture/crops. This also gives them the capability to carry more stock or to conserve more feed.
- to take advantage of market incentives for unseasonal production
- to have less reliance on supplementary feeding (grain, hay) in grazing operations due to the more consistent supply & quality of pastures grown under irrigation
- to improve the capital value of their property. Since irrigated land can potentially support higher crops, pasture and animal production, it is considered more valuable. The value of the property is also related to the water licensing agreements or ‘water right’.
- to cost save/obtain greater returns. The cost benefits from the more effective use of fertilisers and greater financial benefits as a result of more effective agricultural productivity (both quality and quantity) and for ‘out of season’ production are likely.
Choosing an irrigation system
There is a huge diversity in the types of irrigation technologies/systems used, which is attributable to,
- Variations in soil types
- Varying topography of the land
- Availability of power sources
- Availability of water
- Sources of water
- The period of time when the system was installed
- The size of the area being irrigated
- On farm water storage capacity
- Availability of labour/financial resources
Source of irrigation water
The vast majority of irrigation water use is pumped directly from a water source (river, creek, channel, drag line, hole, dam or bore).
Irrigation scheduling is the process by which an irrigator determines the timing and quantity of water to be applied to the crop/pasture. The challenge is to estimate crop water requirements for different growth stages and climatic conditions.
To avoid over or under watering, it is important to know how much water is available to the plant, and how efficiently the plant can use it. The methods available to measure this include: (i) plant observation, (ii) feel and appearance of the soil, (iii) using soil moisture monitoring devices; or (iv) estimating available water from weather data.
While irrigation has provided a number of important benefits the potential drawbacks of over/under watering include,
- Loss in market value through yield reduction
- Reduction in fruit size and quality
- Unwanted vegetative growth
- Losses of valuable water to the watertable
- Irrigation water travelling over soil can cause erosion. The excessive displacement of the top soil can also affect soil fertility (and hence crop yields), it may also clog drainage ditches and streams (silting), harm aquatic habitats, foul waters used for recreational activities, and increases the need for water treatments.
- Irrigation can cause pesticides, pathogens and weeds to spread during irrigation
- Cause runoff
- Increased operational costs (labour, pumping, cost of water)
- Leaching of nutrients (eg. salt, phosphorus) may lead to algal growth, salinity an nitrate build ups (poisoning) elsewhere in the catchment
- Downgraded product quality and reduced yield.
- Higher operational costs for the producer (hence, reduced profits)
- Pressue on water resources with the Increasing demand for water use by urban dwellers