Handbook for Irrigation of Wine Grapes in South Africa

TABLE 4.6. Criteria for clogging potential of water sources (Haman, 2017 and references therein). FACTOR Clogging hazard based on concentration Slight Moderate Severe PHYSICAL Suspended solids – filterable (mg/  ) <50 50-100 >100 CHEMICAL pH <7.0 7.0-8.0 > 8.0 Dissolved solids/salts (mg/  ) <500 500-2 000 >2 000 Manganese (mg/  ) <0.1 0.1-1.5 >1.5 Iron (mg/  ) <0.2 0.2-1.5 >1.5 Hydrogen sulphide (mg/  ) <0.5 0.5-2.0 >2.0 Hardness as ppm CaCO 3 <150 150-300 >300 BIOLOGICAL Bacteria (per m  ) <10 000 10 000-50 000 >50 000 Filtering is an important pre-requisite for good quality water flowing into the irrigation system, particularly in the case of drip and micro-sprinkler systems. Firstly, irrigation water filters must be designed to suit the systems, i.e. whether they should be sand, ring, or disk filters. Secondly, irrigation filters must be inspected regularly and maintenance carried out accordingly, no matter how big or small the filter bank (Fig. 4.33). Solid particles in irrigation water commonly cause clogging of filters (Fig. 4.34). Algae and slime in the water can also cause severe clogging of filters (Fig. 4.35). The latter primarily depends on factors such as water temperature and nutrient status in the water, particularly if soluble fertilisers are applied through the irrigation system.

FIGURE 4.33. Irrigation filter banks, no matter how big or small, require regular maintenance.

96 CHAPTER 4 – IRRIGATION SYSTEMS