Soil health and water supply

Improving soil health, in particular organic matter content, can maximise the benefit from the supply of water from irrigation and rainfall by increasing infiltration rates and water-holding capacity. 

Options to maximise crop water supply

Manage soil structure to enable retention of readily available water.

Ensure soil is at optimum moisture content at the time of bed formation to achieve a good tilth and maintain storage pores.

Increasing the organic matter content of coarse-textured (light sandy) soils will improve the retention of readily available water for crop growth and provide optimum conditions for microbiological processes such as nutrient cycling.

Simple in-field measurements using an auger or probe can be used to manually check the soil moisture in beds.

Gain useful insights into the health of soils – look out for compacted layers when installing access tubes for soil moisture probes.

In the UK, light limitation of the growth and yield of grass and many combinable crops is more common than water limitation, except for short periods.

Water requirements increase with growth duration (e.g. winter cereals use more water, overall, than spring cereals) and photosynthesis.

Therefore, high-yielding crops increase the risk of water limitation.

Irrigation of potatoes and many vegetable crops is common in the UK, as crop water demand can often exceed the natural supply.

Some growers use information on soil matric potential (in the range -10 to -100 kPa) to assist with scheduling irrigation. Table 1 summarises the link between pore sizes and plant water availability (expressed as soil matric potential).

Table 1. Pore sizes and plant water availability

Notes: Readily available water for plant use from -10 to -100 kPa (also optimum range for soil microbiological processes). Water-holding capacity from -10 to -1,500 kPa

Irrigation scheduling is informed by evapotranspiration measurements in horticultural crop production. However, the need for irrigation can be assessed based on:

• Judgement (such as the look and feel of soil removed from a bed using an auger, or resistance offered to a cane or auger)
• Measurement (such as a neutron probe)

This not only provides information on soil moisture status but can also give clues about soil condition and health. Compacted layers may be detected when installing access tubes for soil moisture probes, while an auger can show the presence of good soil structure and rooting depth.

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