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Southern Arava R&D

In-situ lysimeters for optimizing water and nutrient use efficiency

Background:

Irrigation is essential for agricultural production in the Southern Arava region where rainfall is inadequate to sustain crop growth. This region features both salinity and scarcity of its water resources along with high potential evapotranspiration (3300 mm·y-1) that limits current agricultural production and future expansion. Furthermore, the water use efficiency in agricultural production is rather low. According to the FAO, only 40 to 60% of the water is effectively used by the crop, the remaining water is lost, either through evaporation, runoff, drainage, or deep percolation into the groundwater.

Irrigation scheduling is the primary tool for improving water use efficiency and raising yields, consequently leading to higher incomes and greater water resource availability while minimizing soil and groundwater pollution. Despite considerable efforts to promote the introduction of modem irrigation scheduling tools, their practical application by regional farmers continues to fall below expectations. To date, there is no tool other than in-situ sensors (tensiometers, TDR etc.) that can help farmers to determine irrigation quantities and scheduling based on the soil water status. Nevertheless, these sensors readings do not represent the soil water status in the field since they correspond to a small volume and their operation range is limited and because of the spatial variability of the soil hydraulic characteristics. Hence, a large number of sensors is needed for a reasonable evaluation of the crop's water requirement. Similarly, calculation of irrigation quantities from meteorological data requires crop specific transformation function. Lysimeters, on the other hand, offer precise data on water requirements of specific crops, yield response to various environmental conditions, horticultural management parameters and drainage water quality. However, as far as we know, they have been used for research only.

In-situ lysimeters will be placed in a commercial onion fields located at Yotvata. The lysimeter irrigation and drainage water quantities will be measured with an automated controller, by installing water meters, and with vacuum pumps that will extract the drainage water from the collection tanks placed underneath the lysimeters. The irrigation water quantity will be determined by setting the leaching fraction to 25%.

Objectives

  • To establish and  maintain an orderly distance learning program in many subjects.
     

  • Whether or not drainage lysimeters placed in commercial fields can serve as a tool for growers in determining both irrigation scheduling and fertigation quantities remains an important question for examination.
     

  • In the current research for the first time we aim to adjust in-situ lysimeters placed in a commercial field, for accurate calculation of fertigation quantities. Determination of the lysimeter design (dimensions and optimal quantity in a field plot) will be according to the variability of the soil hydraulic characteristics and water content.
     

  • Many growers over irrigate due to a general lack of means for measuring crop water use. The proposed tool will increase water use efficiency of field crops while simultaneously decreasing agrochemical use and soil contamination.

Contact:
Amnon Greenberg

08-6355733