Table A4.5 Hydraulic load preventive measures Control points Verification P Target remains less than field capacity, Irrigation Irrigation tools Delivery of except where leaching is required. When irrigating, apply correct water If leaching is required, ensure it is appropriate volumes of volumes. minimised. water and use alternative Appropriate volumes of water are irrigation methods applied for plants grown, weather (eg drippers) to restrict conditions, soils and the leaching rates of water addition. fraction required. Calculated Ensure irrigation amount of water needed is scheduling methods follow recorded, measured on application best practice. Water and documented. applied must be carefully No symptoms of waterlogging in calculated to match current plants. Symptoms include demand, according to yellowing or decay between the standard protocols (Allen veins, leaf tissue becoming soft at et al 1998, Christen et al the base or in the centre. Wilting 2006). may occur due to root decay, damaged roots appear blackened. Hydraulic conductivity of the soil Soils Site selection Drainage profiles copes with the required Select sites with sufficient capacity of leaching fraction and irrigation drainage capacity. If there specific site volume required for the plants to is a shallow A soil horizon is be grown (saturated hydraulic above a layer of appropriate. conductivity) at least impermeable clay, this >5 mm/hour). may lead to waterlogging. Groundwater remains below 2 m Verify watertable is >2 m Groundwater during irrigation and rain events. from soil surface or the below 2 m. lateral hydraulic conductivity of the watertable will handle required leaching fractions and irrigation rates. Soil water content less than field Drainage Drainage capacity; drainage at least Subsoil drainage can be >5 mm/hour. >5 mm/hour. installed to increase Soil water infiltration rate and content remove excess water. Verify watertable >2 m from Monitoring Groundwater Ground- surface. Ensure watertable remains water below 2 m. >2 m from soil surface. Note: All control points, preventive measures, target criteria, critical limits, critical control points, and their verification are
Table A4.5 Hydraulic load preventive measures Control points Target Verification Irrigation Irrigation tools When irrigating, apply appropriate volumes of water and use alternative irrigation methods (eg drippers) to restrict rates of water addition. Ensure irrigation scheduling methods follow best practice. Water applied must be carefully calculated to match current demand, according to standard protocols (Allen et al 1998, Christen et al 2006). Soils Site selection Select sites with sufficient drainage capacity. If there is a shallow A soil horizon above a layer of impermeable clay, this may lead to waterlogging. Verify watertable is >2 m from soil surface or the lateral hydraulic conductivity of the watertable will handle required leaching fractions and irrigation rates. Drainage Subsoil drainage can be installed to increase infiltration rate and remove excess water. Delivery of correct water volumes. Drainage capacity of specific site is appropriate. Groundwater below 2 m. Drainage >5 mm/hour. Soil water content remains less than field capacity, except where leaching is required. If leaching is required, ensure it is minimised. Appropriate volumes of water are applied for plants grown, weather conditions, soils and the leaching fraction required. Calculated amount of water needed is recorded, measured on application and documented. No symptoms of waterlogging in plants. Symptoms include yellowing or decay between the veins, leaf tissue becoming soft at the base or in the centre. Wilting may occur due to root decay, damaged roots appear blackened. Hydraulic conductivity of the soil profiles copes with the required leaching fraction and irrigation volume required for the plants to be grown (saturated hydraulic conductivity) at least >5 mm/hour). Groundwater remains below 2 m during irrigation and rain events. Soil water content less than field capacity; drainage at least >5 mm/hour. Ground- water Monitoring Ensure watertable remains >2 m from soil surface. Groundwater below 2 m. Verify watertable >2 m from surface. Note: All control points, preventive measures, target criteria, critical limits, critical control points, and their verification are P
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