Controlled Deficit Irrigation Research Articles

New challenges for Uruguayan viticulture: water management in the context of a changing climate

Climate scenarios in the medium and long term (2010-2070) foresee increased summer rainfall for Uruguay and the region, with increased water deficits and excess episodes. Although at the international level irrigation in viticulture has a long experience and tradition, at the local level (Uruguay), only 10% of the vineyard surface area implements a fixed or complementary system for water supply in their crops. This work aimed to model the crop water requirements for a vineyard in southern Uruguay based on pedo-climatic variables. In addition, the plant response to controlled deficit irrigation was evaluated in two consecutive seasons. The experiment was conducted in a 1.1 ha commercial vineyard in Canelones, Uruguay (34°36'S, 56°14W), during two successive seasons (2020-2021). The additional irrigation (I) treatment was compared against a control (C) without irrigation. A controlled water deficit was established from flowering to harvest. The adjustment in the demand was made as a function of a percentage of crop evapotranspiration. The Kc of the crop was estimated using digital tools. The simulation of the water balance made it possible to evaluate the vineyard water needs. Plants subjected to controlled deficit irrigation showed higher vegetative growth, positively impacting yield and the accumulation of sugars and anthocyanins in the berry. Based on our results, a supplementary water supply, at the right doses and time, allows us to face water deficit situations, positively impacting the productive and economic variables. Knowing the variability in a vineyard is necessary to achieve proper irrigation scheduling and optimize water use. New technologies applied to irrigation are an opportunity for winegrowers to obtain more sustainable vineyards and production.

EDTA biodegradability and assisted phytoextraction efficiency in a large-scale field simulation: Is EDTA phasing out justified?

Enhanced phytoextraction of metal-polluted soils using EDTA is phasing out in favor of biodegradable chelants. However, these are too short-lived to be effective in the acclimated biodegrading soil environment established in long-term phytoextraction operations. We hypothesize that full-scale EDTA-enhanced phytoextraction can be both effective and environmentally safe, provided that soil leaching is prevented while EDTA persists in the soil profile. This was tested for 4 years in two sealed, well-monitored constructed lagoons (70-m3 each) packed with Cd-contaminated dredged sediment. Fast-growing, high-biomass, salinity-resistant eucalypts were planted in June 2010. Under controlled deficit irrigation, the 3-year average EC was 14.2 dS m−1. Summer leakage accounted for ∼1.2 % of the overall irrigation water and was prescribed for monitoring the composition of the soil solution. Altogether, 486 leachate and 261 suction-cap solutions were collected at average intervals of 5.5 days. EDTA was intermittently applied with summer irrigation, in multiple low doses at average seasonal concentrations of 1.1–9.2 mM. The soil solution EDTA biodegraded quickly after those applications were stopped. This cessation was timed well before the start of the rainy season. Spontaneous EDTA leaching during the three winters accounted for <0.02 % of the total 423 mol/basin applied. Prescribed summer leaching constituted ∼1 % of this total. Peak heavy metal (HM) concentrations in the leachate and suction-cap solutions (e.g., Cd, up to 18.5 and 14 mg L−1, respectively) were observed soon after EDTA application. Winter HM concentrations were not significantly different from the background. As the amounts of EDTA diminished, HM also disappeared from the soil solution, probably by adsorption. Eucalyptus occidentalis was by far the most efficient Cd sink of the five species tested,. The results of this study strongly support our hypothesis that EDTA-enhanced phytoextraction can be both effective and environmentally safe.

Sustainability of Vine Cultivation in Arid Areas of Southeastern Spain through Strategies Combining Controlled Deficit Irrigation and Selection of Monastrell Clones

The use of rootstocks and clones with different vigor and sensitivity to water deficit is an important and useful agronomic tool for vineyard management. It is essential to search for systems and strategies that maximize efficiency and productivity in the use of water. The objective of this work was to carry out a comparative economic and environmental evaluation, using the life cycle cost (LCC) and life cycle assessment (LCA) methodology, of the organic cultivation of seven Monastrell clones under two irrigation strategies, as well as to evaluate the productivity of water. The grape production depended significantly on the clone and the irrigation treatment, but the interaction between these factors was not significant. The differentiating effect of the °Brix on the price and gross receipts was very insignificant. Thus, the most important differences in productivity were those that determined the differences in economic productivity; clones 188 and 94 stood out for their high profitability. In relation to water, the most productive, water-use-efficient clones (94 and 188) showed very high WUE values. The combination of the selected plant material with the application of controlled deficit irrigation programs is a strategy with relevant economic and environmental effects on the sustainability of wine grape cultivation, especially in semi-arid areas with limited water resources.

A review on smart irrigation management strategies and their effect on water savings and crop yield

AbstractAppropriate irrigation water management has attracted a considerable degree of attention because it is crucial to guarantee water and food security worldwide. A smart irrigation system is applied for the rational use of water in agricultural fields and for maximizing crop yield. Thus, the high demand for water resources is decreased, and the adverse environmental impacts of irrigation are reduced. Different irrigation approaches were developed to reduce overirrigation by assessing the soil moisture content or crop water stress index. This paper aims to review conventional and smart irrigation technologies and discuss their effect on water savings, yield, and crop quality. The analysis of prominent studies highlighted that the water use efficiency based on soil moisture sensors depends on the volumetric moisture content threshold value set by farmers. Soil moisture sensor controllers, evapotranspiration controllers, and rain sensors have been shown to save 20%–92%, 20%–71%, and 7%–50% of water, respectively, while maintaining crop growth and quality. The optical sensor‐based system showed a better ability to assess crop and soil variability in the field than the on‐site measurements. The conventional controlled deficit irrigation technique was found to decrease the crop yield to less than 25% with water savings of up to 13%.

An ICT-based decision support system for precision irrigation management in outdoor orange and greenhouse tomato crops

The digitalization of the agricultural sector through the implementation of cutting-edge technologies allows for the optimization of the use of water, whose scarcity has become one of the most relevant and complex environmental global problems. Water consumption data collected on site using different technologies is key to achieving optimal irrigation scheduling. Technology is also a useful tool that provides a real and transparent inventory of water use in irrigated crops. The water footprint obtained in accordance with ISO standard 14046 (using the Life Cycle Analysis methodology) and jointly with irrigation management information allows determining water use efficiency with great accuracy. This work presents a decision support system developed for precision irrigation management at farm scale called DSSPIM. The system provides a verifiable inventory of water use and an analysis/diagnosis of the adequacy of the irrigation performed using information and communication technologies (ICTs), as well as real-time knowledge of water inputs and outputs during crop development based on data received from water meters and soil moisture sensors installed in the field. Additionally, to achieve both purposes, a methodology is proposed to more accurately estimate rainwater use (green water) based on real measurements and the use of ICTs. The proposed methodology was applied during one season in two organic crops (greenhouse tomatoes and orange trees) located in southern Spain. The model allowed detecting inefficiencies in irrigation water use. A comparison between the actual management practices and the practices recommended by the DSSPIM underlines the importance of irrigation management in improving water use. In the case of orange trees, different irrigation system management scenarios were compared and showed that the application of controlled deficit irrigation strategies using DSSPIM can reduce irrigation water use by 20%.

Controlled deficit irrigation – effects on growth and water relations of Daucus carota L. roots

Controlled deficit irrigation – effects on growth and water relations of <i>Daucus carota</i> L. roots

Effects of Deficit Irrigation Scheduling on Water Use, Gas Exchange, Yield, and Fruit Quality of Date Palm

Water scarcity is very common in the arid region due to the low yearly rainfall. The cost of water for agricultural usage is extremely high in dry locations. Date palm is a high water-demanding tree throughout the year in arid regions. Therefore, the application of deficit irrigation strategies for date palm cultivation may significantly contribute to conserving irrigation water. The present study aimed to assess the effects of controlled deficit irrigation using two modern micro-irrigation systems on water use efficiency (WUE), gas exchange, fruit yield, and quality of date palm (Khalas cv.). The irrigation systems included drip irrigation (DI) and subsurface irrigation (SI) systems. The study was conducted during the 2020 and 2021 seasons at the Date Palm Research Center of Excellence, King Faisal University, Saudi Arabia. The meteorological variables of the study area were real-time monitored using cloud-based IoT (Internet of Things) to calculate the evapotranspiration reference (ETo) and control the irrigation scheduling. Three irrigation treatments (50, 75, and 100% ETc) were applied using DI and SI systems compared with the traditional surface bubbler irrigation (Control). The actual applied water at the deficit irrigation treatments of 50, 75, and 100% ETc were 27.28 ± 0.06, 44.14 ± 1.07, and 55.55 ± 0.37 m3 palm−1, respectively. At all deficit irrigation treatments, the leaf chlorophyll and gas exchange were significantly higher in the SI compared to the DI system. The yield of date palms did not differ significantly between the control and SI systems at both the level of 100 and 75% ETc. The WUE under the SI (1.09 kg m−3) was significantly higher than the DI system (0.52 kg m−3) at the 50% level. There was no significant difference regarding the fruit quality parameters between SI at 50% ETc and control at 100% ETc. Therefore, adopting deficit irrigation strategies using the SI system at 50% ETc level throughout the year could be suggested for date palm irrigation to save water, improve WUE, and maintain fruit quality.

Mating Communication of the Variegated Leafhopper, Erasmoneura variabilis, With Notes on Vibrational Signaling of Other Grapevine Cicadellids in California

Abstract Leafhoppers in the tribe Erythroneurini are a concern for grape growers in California due to direct feeding damage by piercing the leaves. Management of leafhopper populations in vineyards may be accomplished by insecticide applications, the release of natural enemies, conservation biological control, exploitation of controlled deficit irrigation, or a combination of the above. Based on research on other leafhopper species, a behavioral mating disruption is a viable option, but nothing is known about the mating communication and circadian signaling of these species in vineyards. The objectives of this study were to identify and describe vibrational signals associated with mate selection behavior of Erasmoneura variabilis and Erythroneura ziczac, and evaluate the occurrence of vibrational signals within sympatric populations of E. variabilis, E. ziczac, and Homalodisca vitripennis on grapevines. Analysis of vibrational communication signals revealed that 1) one female signal and two distinct male signals are used in E. variabilis pair formation, 2) the pair formation process in E. variabilis is divided into three communication phases, 3) E. variabilis pre-copulatory communication is longer in the presence than in the absence of male-male rivalry, 4) two distinct signals are used in E. ziczac pair formation, and 5) E. variabilis, E. ziczac, and H. vitripennis sing at night and during the day. Results include detailed descriptions of leafhopper communication signals that are relevant for future development of vibrational disruption as a novel method to suppress populations under field conditions.

Effects of Water Stress on the Phenolic Compounds of ‘Merlot’ Grapes in a Semi-Arid Mediterranean Climate

Of all the abiotic stress types to which plants grown in fields are exposed, the most influential is water stress. It is well accepted that adopting controlled deficit irrigation strategies during the growing season has beneficial effects on the chemical compositions of grapes and red wines. However, there is a discrepancy in the timing, intensity and duration of deficit. This study aimed to evaluate the changes in phenolic composition of ‘merlot’ cultivar grapes when subjected to different levels of water stress in a semi-arid Mediterranean climate. Four treatments with different water stress levels were applied within two phenological intervals (flowering-veraison, veraison-maturity) to 128 grapevines for two consecutive years. The water stress levels for Treatments 1, 2, 3 and 4 were: no-light, light-moderate, moderate-intense and intense for the flowering-veraison and veraison-maturity intervals, respectively. Water stress distinctly affected the phenolic compounds in skin and seeds. The concentrations of flavan-3-ols and total polyphenols were much higher in seeds than in skin, and in both fractions, tannins are the major compounds.

Physiological and Yield Responses of Green-Shelled Beans (Phaseolus vulgaris L.) Grown under Restricted Irrigation

Common bean is an important crop, consumed as green-shelled bean in several countries. In Chile, green-shelled beans are cultivated often as a dry land crop, vulnerable to drought. The objective of this study was to characterize the hydric and productive responses of four green-shelled bean genotypes subjected to deficit irrigation in order to outline production strategies in the face of increasing water scarcity. Two experiments were evaluated: one pot experiment with three irrigation treatments, supplying 100% of the crop evapotranspiration (ETc) (T100), 50% (T50), and 30% (T30); and an open field experiment with two treatments: 100% (I100) and 40% of ETc (I40). Treatments were applied during reproductive stage in determinate cultivars and vegetative stage in indeterminate plants. Severe water restriction (T30 and I40) in both experiments showed a significant decrease in stomatal conductances, as well as biomass and number of grains per pod; I40 treatment also showed a reduction in chlorophyll fluorescence. Water use efficiency (WUE) was higher under water stress in field (I40), but lower on the T30 treatment from the pot experiment. Determinate cultivars showed 22.7% higher of 100-seed weight compared to indeterminate type, and, thus, higher tolerance to drought. Our results indicate that severe water stress is highly harmful in terms of yield, and a moderate controlled deficit irrigation plus the use of determinate genotypes may be a strategy for producing green-shelled bean successfully under a drought scenario.

Influence of kaolin application on most important fruit and leaf characteristics of two apple cultivars under sustained deficit irrigation

BackgroundApple is one of the oldest and most valuable fruits. Water restriction is one of the major problems in the production of this fruit in some planting areas.MethodsEffects of kaolin spray treatments were studied on two early apple cultivars of Golab and Shafi-Abadi under sustained deficit irrigation (SDI) in Alborz province, Iran during 2017 and 2018. Irrigation treatments were 100%, 85%, and 70% ETc and kaolin application were concentrations of 0, 3 and 6% in 2017 and 0, 1.5 and 3% in 2018.ResultsResults showed that 85% ETc treatment compared to other irrigation treatments improved apple tree crown volume in 2017. Deficit irrigation treatments significantly reduced fruit weight in both years. Application with 6% kaolin resulted in 33.3% increase in apple fruit weight compared to non-kaolin treatment at 100% ETc irrigation in the first year. Severe deficit irrigation (70% ETc) significantly reduced apple fruit length in both years, but 6% kaolin increased fruit length in both apple cultivars in 2017. Severe deficit irrigation treatment increased the firmness of apple fruit compared to control and mild deficit irrigation (85% ETc) in the first year of experiment. There was no significant difference between irrigation treatments for apple fruit firmness in the second year of experiment. Kaolin treatments of 1.5% and 3% at full irrigation increased the soluble solids content of apple fruit by 36.6% and 44.1% in 2018, respectively. Deficit irrigation treatments significantly increased leaf proline content compared to control in both years. In the first year, kaolin treatments increased leaf proline but in the second year, leaf proline was not significant. Deficit irrigation treatment of 70% ETc and 6% kaolin had the highest amount of glycine betaine content, malondialdehyde and hydrogen peroxide in apple leaf in the first year of experiment.ConclusionsSevere deficit irrigation stress (70% ETc) increased the activity of nonenzymatic defense systems of apple trees. Kaolin as a drought stress reducing agent can be recommended in apple orchards of Golab and Shafi-Abadi cultivars as an effective and inexpensive method to improve tolerance to drought stress conditions.

Controlled deficit irrigation as a water-saving strategy for processing tomato

In a complex scenario characterized by climate change and increasing population demand, it is necessary to adopt production strategies involving a lower use of water. For this purpose, controlled deficit irrigation, CDI, strategies with an initial full irrigation covering 100 % crop evapotranspiration (ETc) followed by mild (50 %ETc) and moderate (75 %ETc) irrigation restrictions after the fruit set stage were evaluated. The study was performed during two years in two growing areas of processing tomato in Spain, using conventional and high-lycopene cultivars. With moderate levels of CDI an average saving of water of 26.1 % was achieved, but productivity was reduced on average by 10.7 %. It should be considered though, that the effect was dependent on the environment and genotype, and high-yield cultivars seemed to be more sensitive to the negative effects of moderate CDI on productivity. In contrast, mild CDI levels did not affect productivity and still entailed a water saving of 13 %. Moderate CDI levels increased soluble solids content, but this increase was not due to a higher accumulation of taste-related compounds, such as sugars and acids. Indeed, irrigation dose had no significant effect on the levels of fructose, glucose, citric and glutamic acid nor on derived variables related to tomato acceptability and CDI decreased the levels of malic acid. Considering previous results, mild CDI strategies would be preferred to continuous deficit irrigation strategies as the former contribute to reduce the use of water, an increasingly scarce resource, avoiding negative impacts on productivity, a key parameter to promote farmer adoption of CDI strategies.

Terrestrial and Remote Indexes to Assess Moderate Deficit Irrigation in Early-Maturing Nectarine Trees

Monitoring plant water status is relevant for the sustainable management ofirrigation under water deficit conditions. Two treatments were applied to an early-maturingnectarine orchard: control (well irrigated) and precise deficit irrigation (PDI, based on soilwater content thresholds). Moderate water deficits generated by PDI were assessed bycomparing terrestrial: stem water potential (Ψstem) and gas exchange parameters, with remote:canopy temperature, normalized difference vegetation (NDVI), and soil adjusted vegetationindex (SAVI), plant water status indicators. The Ψstem was the only indicator that showedsignificant differences between treatments. NDVI and SAVI at the postharvest period wereappropriate indexes for estimating winter pruning, although they did not serve well as plantstress indicator. Vapor pressure deficit along with Ψstem values were able to predict remotesensing data. Ψstem and canopy to air temperature difference values registered the highestsignal intensity and NDVI the highest sensitivity for detecting water deficit situations. Theresults suggest that care should be taken when using instantaneous remote indicators toevaluate moderate water deficits in deciduous fruit trees; more severe/longer water stressconditions are probably needed. The proposed PDI strategy promoted water saving whilemaintaining yield, and could be considered a promising tool for semi-arid agrosystems.

Technological Challenge of Agriculture in Climate Change and the Advancement of Desertification in Developing Countries

Climate change has a strong impact on agricultural production, which accentuates in developing countries, due to the lack of technology. From the perspective of food production, we must answer how to maintain agriculture in developing countries strongly affected by climate change, population growth, poverty and lack of technological capacity. The present mini review aims to explore the options that these communities have, which are fundamentally based on the development of technologies accessible to their reality, as the use of tolerant species such as quinoa and aloe or irrigation systems that improve water use efficiency. This article analyzes mechanisms and strategies of the plants to improve the efficiency in the use of water and the necessary requirements to establish a controlled deficit irrigation system

Potential of Deficit and Supplemental Irrigation under Climate Variability in Northern Togo, West Africa

In the context of a growing population in West Africa and frequent yield losses due to erratic rainfall, it is necessary to improve stability and productivity of agricultural production systems, e.g., by introducing and assessing the potential of alternative irrigation strategies which may be applicable in this region. For this purpose, five irrigation management strategies, ranging from no irrigation (NI) to controlled deficit irrigation (CDI) and full irrigation (FI), were evaluated concerning their impact on the inter-seasonal variability of the expected yields and improvements of the yield potential. The study was conducted on a maize crop (Zea mays L.) at a representative site in northern Togo with a hot semi-arid climate and pronounced dry and wet rainfall seasons. The OCCASION (Optimal Climate Change Adaption Strategies in Irrigation) framework was adapted and applied. It consists of: (i) a weather generator for simulating long climate time series; (ii) the AquaCrop model, which was used to simulate the irrigation system during the growing season and the yield response of maize to the considered irrigation management strategies; and (iii) a problem-specific algorithm for optimal irrigation scheduling with limited water supply. We found high variability in rainfall during the wet season which leads to considerable variability in the expected yield for rainfed conditions (NI). This variability was significantly reduced when supplemental irrigation management strategies (CDI or FI) requiring a reasonably low water demand of about 150 mm were introduced. For the dry season, it was shown that both irrigation management strategies (CDI and FI) would increase yield potential for the local variety TZEE-W up to 4.84 Mg/ha and decrease the variability of the expected yield at the same time. However, even with CDI management, more than 400 mm of water is required if irrigation would be introduced during the dry season in northern Togo. Substantial rainwater harvesting and irrigation infrastructures would be needed to achieve that.

Influence of controlled deficit irrigation on tomato functional value

The effect of controlled deficit irrigation (CDI) on the accumulation of carotenoids, polyphenols and l-ascorbic acid was studied in conventional and high lycopene tomato cultivars. Plants were initially irrigated to cover 100%ETc and after the fruit set phase, the dose was reduced to 75% or 50% of ETc. CDI had no significant effect on the accumulation of carotenoids, while it increased the levels of the hydroxycinnamic acids chlorogenic and ferulic acids, the flavonoid rutin and l-ascorbic acid. Nevertheless, there were important interactions and this effect was highly dependent on the year and site of cultivation. Certain growing areas would be more favorable to supply high quality markets, and, fortunately, CDI would maximize polyphenol (100–75%ETc) and l-ascorbic acid (100–50%ETc) in these areas. A combination of the best genotype and growing area with CDI would offer high quality products, preserving a scarce resource: water.

Automatically controlled deficit irrigation of lettuce in “organic potponics”

Concerns with water crisis involve all sectors of society and irrigated agriculture remains the main water consumer. This study evaluated an agricultural production system for lettuce cultivation in greenhouse, “organic potponics”, to economize water and manure use, using a Simplified Irrigation Controller (SIC), based on soil matric potential monitoring. Five irrigation volumes were evaluated in pots with 4.8 L, fertilized with 200 g of vermicompost. One of the volumes was controlled with the SIC. The other volumes represented 130, 80, 60 and 33 % of that controlled by the SIC and all treatments received water at the same time. Shoot fresh weight, head diameter and stomatal conductance (gs) increased linearly with irrigation volumes. For shoot dry weight, number of leaves and water use efficiency (WUE), the regression was quadratic with maximum values at 126, 114 and 83 %, respectively. Leaf relative water content did not show variation among treatments and changes in some fluorescence parameters (Reo/RC, Sm, N and φR0) were much more remarkable to drought compared with the FV/ FM ratio, one of the most commonly used stress indicators. The data indicated a tradeoff between WUE and plant growth thus the economic values of water and lettuce should be taken into account to indicate the best SIC irrigation volume. Organic potponics is promising and should be further improved to save on water, labor and fertilizer use.

Leaf temperature of maize and Crop Water Stress Index with variable irrigation and nitrogen supply

Crop canopy temperature and Crop Water Stress Index (CWSI) are used for assessing plant water status and irrigation scheduling, but understanding management interactions is necessary. This study evaluated whether nutrient deficiencies would confound interpretation of plant water status from leaf temperature. Leaf temperature and CWSI in maize (Zea mays L.) were evaluated with different irrigation strategies and varying nitrogen (N) supply for replicated glasshouse and field studies. Glasshouse treatments consisted of well-watered or simulated drought and sufficient, intermediate, or deficient N. Field study treatments consisted of well-watered, controlled deficit irrigation, or simulated drought and sufficient, sufficient delayed, or deficient N. Average CWSI values varied across irrigation treatments, with 0.37 and 0.54 for glasshouse well-watered and drought and 0.34, 0.47, and 0.51 for field well-watered, drought, and controlled deficit treatments, respectively. Nitrogen levels created widely different leaf chlorophyll contents without affecting leaf temperature or CWSI. Canopy water stress measurements were robust across varying N levels, but CWSI did not correlate well with leaf area due to confounding effects of irrigation timing and nitrogen levels. Leaf temperature and CWSI are useful for evaluating crop water status, but nutrient status and timing of water stress must also be considered for crop growth prediction.

Controlled deficit irrigation for orange trees in Mediterranean countries

Orange tree cultivation is widespread throughout the world, and the Mediterranean Basin is an important producer. The Mediterranean climate is characterised by scarce water resources that limit crop sustainability. In this study, controlled deficit irrigation is evaluated as a water conservation strategy with the aim of improving crop sustainability. To accomplish this objective, a trial is conducted in southern Spain for nine months with four treatments (five repetitions each): normal irrigation (the control variable), deficit irrigation and two treatments of controlled deficit irrigation. In relation to the crop, physiological parameters, production and fruit quality were analysed, all with respect to water usage. Finally, an efficiency curve was established for water usage, which determined the optimum water usage to be between 700 and 800 mm. It has been experimentally determined that controlled deficit irrigation reduces water used by 5% compared with constant deficit irrigation and improves productivity by 4%. The primary conclusion is that controlled deficit irrigation strategies present certain advantages to crop management and are an alternative to reducing water inputs with minimal effects on production and fruit quality, thus contributing to crop sustainability.

Qualitative response of roselle to planting methods, humic acid application, mycorrhizal inoculation and irrigation management

ABSTRACTCrop management is an important factor affecting the quality of medicinal plants. Therefore, objectives of our investigation on roselle (Hibiscus sabdariffa L.) were: 1) To identify an appropriate planting method in semi-arid regions and 2) to study crop production under water-deficit conditions using eco-friendly techniques. We specifically investigated the effects of planting methods (direct sowing vs. transplanting) (experiment 1, in a randomized complete-block design), as well as effects of water regimes [irrigation after pan evaporation of 100 mm (normal irrigation) and 200 mm (deficit irrigation)], humic acid application (0 and 4 kg ha −1) and mycorrhizal inoculation (Glomus versiforme, Glomus intraradices, and control) (experiment 2, in a split-split-plot layout) on certain qualitative indices of roselle. The amounts of total soluble solids (TSS), anthocyanin content, and maturity index for direct seeding were, respectively, 17%, 15%, and 33% higher than those for transplanting, whereas vitamin C content and total acidity for transplanting treatment were, respectively, 17% and 20% more than those for direct sowing. According to data obtained from the average of the three mycorrhizal treatments, normal irrigation combined with humic acid application increased total acidity (0.88 mg.100 g−1), anthocyanins (67.1 mg.l−1), and vitamin C content (2177 mg.100 g−1) over the control (deficit irrigation and no humic acid application, which had lower acidity (0.53 mg.100 g−1), anthocyanins (38.8 mg.l−1), and vitamin C content (1882 mg.100 g−1). Total phenol and anthocyanins content under mycorrhizal inoculation were relatively higher than under control treatment at both levels of irrigation. G. intraradices produced the largest amount of vitamin C (2353 mg.100 g−1) under deficit irrigation. On average, no-inoculation treatment had higher TSS, pH, and total acidity than any mycorrhizal inoculation treatment. Humic acid application and mycorrhizal inoculation, especially using G. intraradices, showed the highest values of anthocyanins (56.9 mg.l−1) and vitamin C (2309 mg.100 g−1) content. Overall, normal irrigation, combined with humic acid application and mycorrhizal inoculation, partially improved the quality indices of roselle.