Country Impacts

Improving Agricultural Water and Fertiliser Management in

The Challenge

Cash crops in Libya are often grown in the light-textured sandy soils of the coastal belt covering an area of approximately 250,000 ha. These soils tend to have low water holding capacities and high infiltration rates, i.e. the rate at which soil is able to absorb rainfall or , and are prone to loss of water through rapid drainage below the crop roots, with a concomitant loss of water-soluble plant nutrients from the soil. Libya relies predominantly on sprinkler systems and applies as much as 1000 mm of irrigation water to many of its cash crops. Because of the intensive use of water, in Libya accounts for about 83% of the country’s total freshwater withdrawal, and is the major cause of the rapidly dropping water tables. Libyan agriculture therefore faces significant challenges to quickly reduce its vast water consumption. Agricultural water management, including improved irrigation methods, fertilisation and the utilisation of crops that use water efficiently, is important in facing the increasing demand for freshwater in the coming decades. Large amounts of nitrogen fertilisers are being used for cash crops in the coastal Green Circles – pivot irrigation in the Al Khufrah , Libya belt of Libya. On average, 600 kg nitrogen/ha is applied to crops such as from manure and mineral fertilisers on these light-textured soils. Combined with the excessive application of irrigation water, this results in excessive leaching of nitrogen and other crop nutrients to below the crop roots where they can potentially contaminate the groundwater. There is therefore an urgent need to improve both the water and the nitrogen fertiliser use efficiency in this coastal belt.

The Project

Through an IAEA technical cooperation project1, the Biotechnology Research Centre, the Agriculture Research Centre and the Tajoura Nuclear Research Centre in Libya quantified water and nutrient requirements for potato production in the coastal region. The project compared 400 mm of drip fertigation (the simultaneous application of water and soluble nutrient) containing 100, 200, 300 and 400 kg of nitrogen/ha, with conventional overhead sprinkler irrigation of 1000 mm combined with a surface application of 200 kg of nitrogen/ha. The soil moisture neutron probe was used to measure soil water content to improve irrigation scheduling, while the 15N labelled fertiliser was used to evaluate nitrogen uptake by plants as influenced by irrigation technology and application rate of water and nitrogen fertilisers. Using 400 mm of drip fertigation, the best potato yields of 34 to 37 t/ha were obtained with the three lowest doses of nitrogen, while the yield with the overhead sprinkler system using 1000 mm of water and 200 kg of nitrogen/ha was much lower at 12 t/ha. The corresponding water use efficiency ranged from 7.6 to 8.2 kg/m3 with drip fertigation, compared to only 1.1 kg/m3 with the overhead sprinkler.

The Technology

The soil moisture neutron probe (SMNP) is an instrument that measures soil water content for crop production. During the measuring process, the probe emits neutrons that collide with hydrogen atoms in soil water. This collision slows down the speed of the neutrons. The change in the speed of the neutrons is detected by the probe and provides a reading that corresponds to the soil water content. The SMNP is currently the most suitable instrument to accurately measure soil moisture under saline conditions. It is also widely used to calibrate other moisture sensors for direct use in farmers’ fields. Nitrogen is a major nutrient for plant growth. Labelling nitrogen fertilisers with the 15N stable isotope can help to determine the fate of applied nitrogen from fertilisers in soils, plants and water, and is therefore a safe and useful tracer in determining the nitrogen fertiliser Fertigation and drip irrigation in Libya use efficiency of crops. Fertigation is the simultaneous application of irrigation water and liquid fertiliser through a drip irrigation system that enables both water and fertiliser to be delivered directly and simultaneously to the root zone of the crop with minimal loss. Accordingly, benefits arising from this technology include a more precise application of water and nutrients at the right time and at the place they are needed; and a reduction in amounts of water and nitrogen required, leading to cost-savings to farmers and a reduced fertiliser impact on the environment.

The Impact

Compared to the average potato yield in Libya of up to 20 t/ha, this project effectively showed that a 2- to 3-fold increase in yield could be obtained using 40% or less of the water and only one sixth or less of the nitrogen fertiliser normally applied by farmers. More importantly, it highlighted the high potential economic benefits to farmers arising from savings both on fertiliser and on labour costs, and identified a key option for Libyan agriculture “I am extremely happy with the to contribute effectively towards resolving the projected medium-term outcome from the association of water shortages in the country. Accordingly, drip irrigation/fertigation is the Tajoura Nuclear Research rapidly finding its way into the water management practices of Libyan Centre with the IAEA on this farmers. project. Through IAEA assistance A complete transition in Libya from the sprinkler irrigation system to drip we were able to show that drip irrigation/fertigation could potentially reduce the freshwater demand of fertigation is a potential irrigation 3 3 Libyan agriculture from currently 1000 m /ha to 400 m or less, and hence and nitrogen management tool play a major role in ensuring freshwater availability beyond the next for potato production in Libya that decade. Likewise, the reduction in nitrogen fertiliser from 600 to 100 kg/ha can dramatically improve water or less, would contribute to halting the increasing salinization of agricultural use efficiency and nitrogen soils and the negative impact of current irrigation practices on the Libyan fertiliser utilization in the field”. environment. Mr Abdulhafied Ellafi National Scientific Research Council Tajoura Nuclear Research Center.

For further information, please visit: The Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture International Atomic Energy Agency, Wagramer Strasse 5, PO Box 100, 1400 Vienna, Austria www-naweb.iaea.org/nafa/swmn

1 LIB5010 on “Establishing a drip Irrigation-fertigation system using nuclear techniques”, 2004-2007.