Indicators of Sustainable Irrigated Agriculture

6 Production Indicators

Sustaining production on a farm relates to optimising the amount of produce grown over the long term. Farmers do not always seek to maximise production as it does not necessarily lead to maximum profits, because of the effect of input costs such as energy, labour, and other resources. Sustainable production also involves being able to continuously produce at the optimum rate without a reduction in the quality of the product.

6.1 ISSUES

Irrigation directly affects production. The main reason why farmers irrigate is to increase production. When managed correctly, irrigation will always result in increased production when crops would otherwise be subjected to soil moisture deficits. Irrigation’s most direct benefit is in reducing risk associated with drought, but it has other benefits such as reducing the likelihood of pest outbreaks, producing healthier livestock, and reducing financial and social stress. Production benefits due to irrigation are a function of the amount of money, time and energy invested in the irrigation system. The investment required to install and operate an irrigation system is significant, and farmers need to be sure that this investment is justified. This does not only apply to new systems. When a system becomes older, for example, the cost of maintaining the irrigation equipment may outweigh the production benefits gained from the system.

6.2 POTENTIAL INDICATORS

Farmers, in their regular assessment of the state of the farm, already measure a number of production indicators. The following are potential indicators:

quantity of produce;

quality of produce;

health of livestock;

amount of pest problems;

production per unit of water;

production per unit of energy input;

production per labour unit (hour);

number of lost irrigation hours per season due to system failure;

production per unit of water used (including rainfall).

The use of a particular indicator can result in the identification of a problem area, enabling farm managers to react directly to rectify the situation. Irrigation affects many of these parameters - the quantity and quality of the produce, the cost of production (need for more/less irrigation), energy consumption, labour input, repairs and maintenance of equipment.

6.3 RATIONALE FOR SELECTING INDICATORS

Decreasing or increasing the volume of irrigation water applied will have an effect on most of the potential indicators listed above, but the most important in terms of production optimisation will be on the quantity and quality of the product, and how efficiently the crop can be produced. Indicators such as livestock health and pests are inherently included in the measures of product quantity and quality because they have a direct effect on production. They are also likely to be monitored independently of irrigation.

The quantity of produce per hectare for each crop is important, as it is the primary determinant of revenue for the crop. Insufficient irrigation, while it may result in lower costs, may cause a significant reduction in yield. Conversely, applying excessive irrigation, while it may maximise yield (all other things being equal) may be less profitable overall because of the additional cost of irrigating.

In addition to increasing yield, well-managed irrigation systems generally produce higher quality crops, and even though the relationship between irrigation applied and quality may be a subjective assessment, there is no doubt that a positive relationship exists for many crops.

On their own, indicators of quantity and quality do not tell the full story, as they do not give any indication of the costs of achieving the production. Indicators relating production to the input of water, energy and labour lead to an overall assessment of the efficiency of the operation. Water use efficiency is discussed below and energy and labour efficiency in Sections 7 and 8.

The net amount of water required to grow a crop, whether the water is from rainfall or irrigation, is about the same each year. However, as rainfall varies significantly, irrigation also varies each year. The gross amount of water that needs to be applied through irrigation to make up the difference between the total needs of the crop and that supplied by rainfall depends on two factors: irrigation efficiency, and the risk of not satisfying the water demand of the crop.

Irrigation efficiency

The less efficient the irrigation, the more water that needs to be applied. Efficiency relates to how much of the irrigation water and rainfall is usefully used by the crop (refer to Section 10 - Water indicators). Inefficient irrigation will result in a higher total seasonal water use, as the irrigation component of water use will be higher. Conversely, more efficient irrigation will use less water.

Risk of not fully satisfying the water demand of the crop

An irrigation system that is able to supply enough water to meet or exceed the water demands of a crop at all times, including extreme drought years, requires an irrigation system capacity which is much higher than that required to fully meet demand most but not all of the time. There is a significant cost to this extra capacity, which may not be able to be justified for economic reasons. Farmers often choose to risk losing some production in extremely dry years to reduce the cost of the irrigation system through lower capacity. Systems with lower system capacities inherently result in higher efficiencies and better use of rainfall, and lower overall water use, but they produce more variable yields. Above a certain capacity, the incremental yield benefits of irrigation decrease with increasing irrigation system capacity.

Production per unit of water used is an easy way of indicating whether irrigation and rainfall are being used efficiently, and can be used to compare the total water use from season to season. However, this indicator needs to be reported for each crop because different crops have different water requirements and responses to water. To assess the effect of irrigation on individual crops, the quantity of each type of crop produced should be recorded, and compared with the irrigation water applied to the crop.

The recommended indicators will be ideal for inter-farm comparisons, to give an indication of the most effective systems. Aggregation can result in production figures for an entire region or scheme. Energy, water and labour figures are readily available to the farmer through accounting records, power bills and timesheets. Production quantity and quality data can also be determined from crop records and sales information.