Dairy Farming Activities Science Centres: Freshwater and Estuaries , Te Kūwaha Dairy farms operate to maximise milk production. Milk production Dairy farms are either seasonal (spring-autumn) or town supply (year round) operations. Expansion of the dairy industry over the last 20-30 years is largely due to the rapid conversion of dry stock and forestry land to dairying as well as the intensification of farming methods that has led to an increase in stocking rates (cows per hectare). During the milking season, cows are usually milked twice a day. During milking, animal waste (dairy effluent) that accumulates in the milking shed and yard is washed down with high pressure hoses and collected in oxidation ponds. This effluent may also contain other elements, such as spilled milk, soil, animal feed, detergents, and other chemicals (i.e., residue from animal health products such as drenches and antibiotics). Dairy effluent contains organic and inorganic nutrients (especially nitrogen and phosphorous) and contaminants (e.g., pathogens and sediment ), which all have the potential to impact on water quality and mahinga kai if not disposed of correctly. Dairy effluent cannot be discharged to water directly and needs to be disposed of either by: 1. Settling effluent in an oxidation pond, then spreading onto land. 2. Irrigating dairy shed effluent directly onto land. Soil and pasture management The greatest on-farm contribution of nutrients and pathogens into waterways comes from animal faecal matter and urine. Animals with open access to waterways or that cross streams are especially likely to increase nutrients and pathogens into a stream. During times of heavy rain, waste can wash into waterways via surface runoff from paddocks or tracks and roads. Waterways become especially prone to increased nutrients from faecal matter and fertilisers when there are no fences or riparian vegetation , which exclude stock from waterways and absorb excess nutrients in the runoff. Increasing the number of cows per hectare (overstocking) to maximise production may have detrimental effects on soil structure (compaction, pugging, and trampling