Irrigation and Drought Tolerance in Carob Tree
Carob is one of the most drought-resistant fruit trees in the Mediterranean. It can survive long dry periods thanks to its deep-seated roots, thick, waxy leaves and physiological mechanisms that allow it to use water economically. However, enduring drought is not the same as yielding a bountiful crop: Studies show that even a limited amount of water given at the right periods can significantly increase yields.
In this article, we discuss the drought resistance mechanisms of carob, rainfall and water needs, critical irrigation periods, the effect of irrigation on yield and the importance of irrigation in young saplings in the light of scientific studies.
How Drought Resistant Is Carob?
The monograph published by IPGRI states that carob lags only behind pistachios in terms of resistance to dry environments. According to the monograph, carob is a xerophyte (xerivorous plant) that has adapted well to the ecological conditions of the Mediterranean region, and it owes this adaptation to its effective adjustment of its pores and regulation of water loss, leaf structure and anatomy (Batlle and Tous, 1997).
In the collection of Dahmani et al., it is emphasized that carob shows a strong resistance to drought and behaves like a real drought-resistant species that adapts morphologically and physiologically to water scarcity. In the same review, it is stated that carob in Morocco is very drought resistant even with 200 mm of rainfall, but not cold.
The authors of a study conducted in Cyprus also define carob as a heat and drought-resistant crop that can grow in arid areas with almost no inputs, and draw attention to the increasing importance of such products in today's world where the climate crisis is deepening (Varnava et al., 2023).
Mechanisms of Drought Resilience
The ability of carob to survive in arid conditions is not based on a single feature, but on many mechanisms that complement each other.
Deep Root System
Deep roots lie at the heart of drought resistance. According to the IPGRI monograph, the rooting habit of carob is similar to that of pistachios; its extensive root system goes deep into the soil. Carob develops roots to explore deeper layers where water can be found under stress conditions, allowing it to survive long periods of drought.
The values regarding root depth are also remarkable. Dahmani et al. state that taproot can reach a depth of 18 meters, while the investor guide of the Ministry of Agriculture and Forestry states that the roots can go 15-20 meters deep from the soil surface, allowing the tree to bear fruit even during severe drought periods. In the study of Şahin and Taşlıgil, it is emphasized that the deep root system supports high productivity in arid conditions.
Natural habitats in Turkey are suitable for this root structure. According to Günal, in the red Mediterranean soils on limestone, which is the most preferred by carob, the crack systems in the rocks function as channels for the roots to reach deep; the water leaking from the surface clings to these cracks and meets the water needs of the plant, especially in the dry period.
Leaf Structure
Carob leaves have properties that limit water loss. According to the IPGRI monograph, the leaves are hard (sclerophyll) in structure; the upper epidermis is very thick and the pores are found only on the underside of the leaf, in clusters. The monograph also states that leaf wax production increases in arid conditions, which reduces the permeability of the cuticle and protects the plant from excessive transpiration.
Physiological Adjustments
Carob survives drought by not only saving water, but also managing it wisely. According to studies cited in the IPGRI monograph:
- Carob trees can keep their pores open and maintain a high water content in the leaf even when water in the soil is low.
- This is made possible by a sharp decrease in leaf water potential in response to small water losses.
- Leaves can maintain cell tension (turgor) in soil drought by using different strategies depending on the season.
- Like other Mediterranean species with long-lived leaves and long flowering periods, it has developed mechanisms that optimize the use of water, carbon and nitrogen according to reproduction.
A two-year study of mature 'Mulata' trees in Portugal found that the leaf water potential measured before dawn in the morning remained above –1.1 MPa in all applications, while the values at noon varied very greatly according to the season and were very low regardless of the applications. The researchers found these results to be in line with the "water-wasting strategy" previously proposed for carob, which is defined as a drought adaptation mechanism (Correia and Martins-Loução, 1995).
Mycorrhizal Partnerships
Arbuscular mycorrhizal fungi that establish symbiosis in the roots of carob may also contribute to drought resilience. In a study conducted on seedlings of two different locust bean ecotypes in Morocco, pore conductivity, water content, and mineral nutrient uptake were found to be significantly higher in plants inoculated with local mycorrhizal fungi during drought and subsequent re-irrigation period compared to plants without mycorrhiza (Boutasknit et al., 2020).
In another study conducted by the same research group with young carob trees, the combined application of mycorrhizal fungus and compost in drought-stressed plants maintained at 35 percent of field capacity increased pore conductivity by 20 percent and leaf water potential by 23 percent at the end of eight months compared to the control (Boutasknit et al., 2021). These results belong to controlled trials at the seedling and young tree stage; the effect in adult gardens should be evaluated separately.
Carob's Water and Rainfall Needs
Drought resistance does not mean that carob does not need water at all. A clear distinction is made between the amount of water required for the survival of the tree and for economic production in the springs.
| Status | Annual rainfall | Source |
|---|---|---|
| The range in which it can live without irrigation | 250–500 mm | Batlle and Tous, 1997 |
| Considered sufficient for fruit set | 350 mm | Batlle and Tous, 1997 |
| Threshold required for supplemental irrigation | Below 400 mm | Batlle and Tous, 1997 |
| Required for commercial product | At least 500–550 mm | Batlle and Tous, 1997 |
| Average annual water requirement | 500–600 mm | Ministry of Agriculture and Forestry, 2020 |
In natural ranges in Turkey, precipitation is generally above these thresholds. According to Günal, the average annual precipitation in these areas is mostly above 600 mm; between Marmaris and Anamur, it exceeds 1,000 mm. However, more than half of the precipitation falls in winter, and the share of summer precipitation is less than 2 percent on the Aegean coast and in the western part of the Mediterranean. In other words, carob spends the summer months with almost no precipitation, even if the annual total is high.
Critical Irrigation Periods
Since water resources are scarce in the Mediterranean region, irrigation is usually reserved for more profitable horticultural crops and carob is mostly grown in dry farming conditions. The IPGRI monograph states that water in this drought-resistant species should be considered as complementary irrigation within certain dose and period limits, and lists the main irrigation periods for carob as follows (Batlle and Tous, 1997):
| Spring and early summer | Possible flower bud formation and rapid growth of pods |
| Autumn | Flowering and reserve nutrient accumulation |
These periods are directly related to the life cycle of carob. Pods go through the fastest growth phase between April and June; the transition to flower formation is thought to begin around June. In autumn, the tree blooms and accumulates reserve nutrients for next year's crop.
In the ministry guide, it is stated that irrigation of carob orchards in spring and autumn will contribute positively to fruit yield. In the IPGRI monograph, it is also stated that nitrogen and potassium can be given in irrigated orchards in May and June, which coincide with the rapid growth phase of pods.
The Impact of Irrigation on Yield
Many studies have shown that irrigation increases the yield in carob. According to the IPGRI monograph, the benefit of even limited water doses of 100 mm per year in adult gardens is clearly reflected in the yield. The comparative data cited in the monograph are as follows:
- Some modern 10-year-old orchards in Spain and Portugal yielded about 5,000 kg/ha in dry conditions and about 7,000 kg/ha with limited irrigation.
- In Israel, it has been reported that approximately 7,400 kg/ha can be obtained from full-yield trees in gardens without irrigation with an annual rainfall of 550 mm, and an average yield of 12,300 kg/ha can be obtained in irrigated gardens.
- The average garden yield in Spain was given as about 1,500 kg/ha, which was considered quite low.
In the study conducted with 'Mulata' trees in Portugal, two different nitrogen doses were applied together with irrigation at the level of 0, 50 and 100 percent of evaporation; it was observed that vegetative growth and fruit production increased as the amount of fertilized irrigation water given increased (Correia and Martins-Loução, 1995).
A recent field trial conducted in 2022–2024 in an 8-hectare commercial orchard in Murcia, Spain, compared full irrigation, reduced irrigation, and no-irrigation application. Full irrigation provided higher and more stable fruit production; pore conductivity was the indicator that reflected the water status of the plant the fastest. The researchers noted that carob can tolerate low-quality irrigation water and can be satisfied with very low water amounts, such as 100–200 mm per year, in complementary or restricted strategies (Pedrero Salcedo et al., 2025).
Watering and Fruit Quality
Water can affect not only yield but also pod quality. In the Alanya Carob geographical indication certificate, it is stated that irrigation is carried out as much as possible for the development and strengthening of the trees, and that the blackening of the fruit flesh and sugar content vary according to irrigation (Turkish Patent and Trademark Office, 2025). Therefore, when planning irrigation, not only the quantity but also the targeted product quality should be taken into account.
Watering in young seedlings
Although the adult carob tree is drought tolerant, the same is not true for the young sapling. Regular water support is critical in the early years, as the roots have not yet reached the deep layers.
According to the IPGRI monograph, life water should be given immediately after planting, the second watering should be done within two weeks, and irrigation should be done 2-3 times in the first summer. Even in gardens without irrigation, it is emphasized that giving some water with a tractor and tank in late spring and summer during the first two years after planting helps the tree to grow and start the product. In the geographical indication certificate, it is stated that irrigation must be done for two years after planting, depending on the climate and soil characteristics. We discuss the planting phase in our article "How to Plant Carob Saplings?".
Irrigation Method and Things to Consider
It is stated in the IPGRI monograph that drip irrigation gives good results in regions where water resources are limited. The Ministry's guideline states that irrigation can be done by drip or sprinkler methods according to the available possibilities.
Here are the main points to consider when watering:
- Carob cannot withstand waterlogging; overwatering and ponding should be avoided.
- Irrigation should be planned according to critical periods in the tree's life cycle.
- In arid regions, even a limited amount of supplemental irrigation can increase yields.
- If saline irrigation water is to be used, analysis should be done beforehand.
Weed control is also a part of water management. In the IPGRI monograph, it is emphasized that competition for water and nutrients with weeds in young gardens can significantly reduce the development and yield of the tree. In the ministry guide, it is stated that reducing water loss by breaking soil capillarity with hoeing in hot and dry periods will positively affect the success of the saplings.
Frequently Asked Questions
Does carob grow without watering? Yes, adult carob trees can live and produce crops without irrigation in Mediterranean conditions. However, it is reported that at least 500-550 mm of rainfall or complementary irrigation is required per year for the product at the commercial level.
When should carob be watered? Sources indicate spring and early summer (flower formation and rapid pod growth) and autumn (flowering and reserve nutrient accumulation) as the primary watering periods.
How much should carob saplings be watered? Life water is recommended for planting, second watering in two weeks and 2–3 irrigations in the first summer. During the first two years, support irrigation should be done in summer.
How much does irrigation increase the yield of carob? It varies according to the region and method. According to the data cited in the monograph, the yield increased from approximately 5,000 kg/ha to 7,000 kg/ha with reduced irrigation in Spain and Portugal, and from approximately 7,400 kg/ha to 12,300 kg/ha with irrigation in Israel.
The Products of a Drought-Tolerant Tree with Carob Türkiye
Carob is one of the most resilient trees in Mediterranean agriculture, with its structure that can live with little water and produce even in arid conditions. In a period when water resources are increasingly limited, the product provided by this tree with limited water gains even more value.
At Carob Türkiye, we supply carob fruit, crumbs, flour/powder, seeds, and extracts. Our Products Carob Fruit, Carob Flour / Powder and Our Products You can review it on the pages. For your wholesale and export requests Contact Now You can contact us on our page.
Domestic resources
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