Soil-plant-water relationships

Current problems of irrigation relate primarily to unsuitable soil types and the geomorphology of the area being irrigated. Soil structures can be changed rapidly by inappropriate irrigation techniques and poor cultivation practices.

Proper soil management calls for the combined skills of pedologists who classify soils, hydrologists who study the movement of water through soils, engineers who design and construct drainage systems, and agronomists. Current irrigation practices need detailed study, including the method, frequency and duration of irrigation in relation to soil types, and the methods and timing of cultivation in relation to the moisture content of the soil.

The potential for increased use of trickle or drip irrigation has already been mentioned. Other possible new techniques include slit irrigation, where the applied water is confined to a narrow trench where the crop is growing, and sub-surface irrigation using cheap bio-degradable piping which would enable the land to be ploughed following harvesting. Sub-surface irrigation minimizes structural breakdown and weed growth is reduced. There is scope for new ideas in this field.

In the plant growth area, much work has been done, but more research is needed into the effects of irrigation management practices on root development, nutrient uptake and moisture stress. More information is needed on soil biology, the effect of soil microbes on soil structure and the availability of nutrients to plants, and the influence of crop rotation on microbiological populations.

Insect and disease control is often critical to the success of irrigated agriculture, and biological control is expected to have a very significant role in helping to reduce the use of herbicides. Again, a multi-disclipinary approach and new techniques are required to avoid the mistakes of the past.

Australian Academy of Technological Sciences and Engineering