Water is one of the main production factors to be considered in drip irrigation. Indeed, water supply is of fundamental importance for crops, as its qualitative characteristics during irrigation process, combined with the agronomic components, allow you to obtain the maximum yield from agricultural crops.
Water must always have some specific hygienic characteristics that do not compromise the quality of the agricultural products with which it comes into contact and, therefore, the health of final consumers.
For example, if water from an underground basin is used, it will be necessary to evaluate the presence of toxic chemical elements such as arsenic, boron or fluorine before using it for agriculture. All harmful elements will be removed with appropriate techniques.
On the other hand, in case of superficial water, it will be necessary to verify possible contamination from waste water, since when it is not properly treated, this may jeopardize the microbiological safety of agricultural production.
The importance of water quality and treatment
According to the type of water source, it will be necessary to use a suitable water treatment to guarantee water quality.
These treatments are designed to eliminate chemical or microbiological pollutants that can compromise human health.
According to current regulations, all food
sector workers must guarantee the use of drinking water for irrigation. The supply source must always contain clean water, i.e. free of microorganisms or harmful substances in such quantities that directly or indirectly affect the health quality of the food.
How to evaluate your water quality? First of all, you need to identify the supply source. Subsequently, based on the characteristics of the water source, chemical and physical treatment to be carried out will be defined, as well as the appropriate filtration system.
Main supply sources
Irrigation water supply can be carried out from different sources which we can divide into:
- Surface water: this water is from natural and artificial basins located within the farm or water from natural water basins located outside the farm. The most common external natural sources are natural lakes, artificial lakes, rivers and waterways;
- Groundwater: these water sources are located in areas adjacent to the farm that use water pumped from wells or other natural underground water sources;
- Aqueduct: these sources are artificial distribution sources, which come from common networks outside the farm and are different from surface water;
- Purified wastewater: these are water sources coming from purification plants;
- Desalinated water: this water comes from brackish basins with a highly saline content. Before being used in agriculture this water is treated in order to reduce its salt concentration;
Brackish water: this water comes from brackish basins characterized by a low saline content and therefore can be used directly without making desalination treatment.Parameters to be monitored
Knowledge of water source type and other quality parameters of the water used for irrigation is essential to obtain the best yield and quality of the crops as well as to keep the soil fertile.
Particularly, if you use:
- groundwater sources: in particular, it will be necessary to monitor water temperature as a too cold temperature which is much lower than the one of soil or crop can damage the crops and cause symptoms similar to those due to water scarcity;
- surface water sources: in particular, the presence of suspended solids and heavy metals will have to be monitored. The use of water with suspended solids, such as sand, silt or clay causes rapid wear of pumps and sprinklers and leads to a greater risk of clogging. Excessive accumulation of heavy metals can be toxic to humans and it is usually caused by acid rain;
- water sources from waste water reuse: in particular, the presence of organic substances or inorganic compounds will need to be monitored. In addition to causing clogging, organic substances also contain carbon. Carbon reacts with oxygen in the water, reducing its concentration. Therefore, the water with organic substances is often depleted. The presence of inorganic compounds such as chlorine, sulfur, carbonates and bicarbonates can be harmful to the plants and for the irrigation system itself. In particular, unlike sulphates, chlorides are more easily absorbed by plants and, in addition to being harmful to humans, when accumulated in large quantities they can cause desiccation of the edge of the foliar lamina. Carbonates and bicarbonates, on the other hand, lead to a PH increase if accumulated progressively over time. When the PH exceeds 8.4, insoluble calcareous compounds can be easily formed which cause the clogging of your drip irrigation system. An excessive presence of inorganic compounds can also cause phytoxicity phenomenon.
- brackish or desalinated water sources: it will be necessary to monitor the level of water salinity. An excessive level of salinity can damage both the soil and the crops. The soil can suffer from such phenomenon as deflocculation, i.e. transition from solid state of clays into dispersed state, with consequent PH increase; or sodicization, i.e. soil sodium enrichment. These phenomena can reduce soil permeability and consequently the speed of water infiltration and excess water drainage. On the other hand, in case of high salt concentration, crops may alter osmotic processes that prevent correct water plants absorption and cause slower growth and water stress phenomena.
