Root adaptation of urban trees to a more precise irrigation system: Mature olive as a case study

Water scarcity encourages municipalities to use more precise irrigation systems in arid urban landscapes. However, major concerns are associated with the adaptation of mature trees to new irrigation systems after they have matured under traditional management. We investigated the adaptation of mature olive trees to a change in irrigation system from a traditional surface to an automatic drip irrigation system in a coarse-textured urban forest park. The growth indices of eight-year-old olive trees were monitored for the period of 2012–2014 under three irrigation systems: (1) automated drip irrigation (ADI) for trees that matured under traditional basin-surface irrigation (TSI), (2) TSI since plantation, and (3) traditional drip irrigation (TDI) irrigating the trees depending on water availability since the time of planting. We additionally determined the spatial pattern of root development by collecting 156 soil samples from each irrigation system with a 20 × 20-cm grid system (120 cm width × 80 cm depth) in the soil profile. Results showed no significant differences in terms of fruit productivity between TSI and recently established ADI systems. Automated drip irrigation resulted in the maximum root density with a uniform root distribution pattern, where roots expanded all over the soil profile. In TSI, however, the roots were distributed irregularly, with the highest density close to the irrigation basin. The wide spacing between drippers in the TDI system created large gaps between the wetted zones in the soil with a low water-holding capacity, leading to a discrete small root system. The present study highlights the positive response of mature olive trees to the replacement of the irrigation system in an urban forest park with limited available water and low soil quality. Our findings will help municipalities to properly preserve mature urban trees and the ecosystem services for their inhabitants.Non peer reviewe

Effect of recycled water applied by surface and subsurface irrigation on the growth, photosynthetic indices and nutrient content of young olive trees in central Iran

Water shortage has encouraged the quest for alternative sources of water for food production and agricultural development. Recycled water (RW) is one of the most available water resources with great potential for use in farm irrigation. This experiment was carried out to investigate the use of RW as the irrigation source and its application method, subsurface leaky irrigation (SLI) system or surface irrigation, in an orchard with young olive trees in central Iran. The results revealed that the SLI system was able to enhance tree growth, leaf area, maximum fluorescence (Fv/Fm) and photosynthesis rate by 68%, 26%, 4%, and 42%, respectively. In addition, trees irrigated with the SLI system using RW exhibited increased N and Mg uptakes by 138% and 8%, respectively. Plants irrigated with RW showed a growth improvement (42%), leaf area (26%), and photosynthesis rate (23.4%) compared with those irrigated with clean water. Furthermore, Mg, Na, K, P, and N content increased by 12%, 59%, 30%, 7%, and 92%, respectively, in leaf tissue when RW was applied. The results indicated that RW could be employed as a reliable irrigation source especially when it was delivered with the SLI system

Effects of inoculation with four mycorrhizal species on seed phenolic and fatty acids of sesame plants grown under different irrigation regimes

Abstract This study evaluated the interaction effects of irrigation level (well-watered and water stress conditions) and inoculation by different mycorrhizal species (non-inoculated, Funneliformis mosseae, Rhizophagus irregularis, Claroideoglomus claroideum, and Glomus fasciculatum) on mycorrhizal colonization, antioxidant activity, seed yield and oil quality of two sesame cultivars (Yekta and Naz). Water deficit decreased mycorrhizal colonization, seed yield and oil concentration but increased antioxidant activity and seed total phenol and flavonoid concentrations. However, mycorrhizal inoculation increased antioxidant activity, seed yield, oil concentration and total phenolic and flavonoids. The lowest reduction by water stress and the highest increase by inoculation in seed yield were observed in Naz plants inoculated by Cl. claroideum. Principal component analysis showed the highest differentiation effect of water stress compared to mycorrhizal inoculation on both cultivars, indicating the relative sensitivity of the two cultivars to water deficit. However, the application of different species of mycorrhizal fungi versus the non-inoculation conditions was somewhat discriminative. In terms of fatty acids, in most cases, water stress increased oleic, palmitic and stearic acids and decreased linoleic and linolenic acids but inoculation increased oleic and linoleic acids and decreased linolenic, palmitic and stearic acids. Regarding phenolic and flavonoids components, the contents of chlorogenic and caffeic acids were increased by water stress but no consistent trend was noted in response to water stress for the other compounds. Mycorrhizal inoculation generally decreased chlorogenic acid but increased gallic, caffeic, p-coumaric, and ferulic acids. In conclusion, the results of the present study may help to increase the level of valuable compounds in sesame for further pharmaceutical purposes under water stress conditions and mycorrhizal symbiosis

Effect of Silicon on Growth and Development of Strawberry under Water Deficit Conditions

Water stress is a major factor that limits agricultural crop production. Silicon (Si) is generally considered as a beneficial element for the growth of higher plants, especially for those grown under stressful environment. This study was conducted to examine the effects of Si on growth and development of strawberry (Fragaria × ananassa ‘Camarosa’) under water stress conditions. A factorial experiment, in a completely randomized design, was used to investigate the effects of three irrigation levels and four Si treatments consisting of 0, 5, 10, and 15 mmol·L−1 potassium silicate (K2SiO3). The results showed that an increase in the levels of water stress caused a decrease in most of the quantitative characteristics such as specific leaf area, chlorophyll fluorescence, net photosynthesis rate, and stomata conductance; addition of Si significantly increased most of the mentioned factors; water stress increased electrolyte leakage, proline, and water use efficiency (WUE); Si treatment significantly decreased transpiration rate and improved chlorophyll content and WUE. Water stress stimulated mineral nutrient absorption whereas Si application decreased it under water stress. In conclusion, it was found that in most of the investigated factors, 10 mmol·L−1 potassium silicate had the best effect on growth and development of strawberry. Besides, Si application had beneficial effects on strawberry plants and the addition of it could alleviate water stress. Keywords: Fragaria × ananassa, potassium silicate, water stress, photosynthesis, mineral nutrien

Water requirements of urban landscape plants in an arid environment: The example of a botanic garden and a forest park

Creation and conservation of urban parks is challenging in arid environments where daily thermal extremes, water scarcity, air pollution and shortage of natural green spaces are more conspicuous. Water scarcity in the arid regions of Iran is major challenge for water managers. Accurate estimation of urban landscape evapotranspiration is therefore critically important for cities located in naturally dry environments, to appropriately manage irrigation practices. This study investigated two factor-based approaches, Water Use Classifications of Landscape Species (WUCOLS) and Landscape Irrigation Management Program (LIMP), to measure the water demand of two heterogeneous urban landscapes: a botanic garden and a sparse forest park. The irrigation water volume applied was compared with the gross water demand for the period from 2011 to 2013. In this research, WUCOLS estimated the annual water requirement of a botanic garden and a sparse forest park to be 5% and 44% lower, respectively, than LIMP. Comparison of estimated and applied irrigation showed that water savings can be made by the LIMP method. The outcomes of this research stressed the need to modify the irrigation requirements based on effective rainfall throughout the year, rather relying on long-term average data

Nitrate leaching in a silage maize field under different irrigation and nitrogen fertilizer rates

Quantification of the interactive effects of nitrogen (N) and water on nitrate (NO3) loss provides an important insight for more effective N and water management. The goal of this study was to evaluate the effect of different irrigation and nitrogen fertilizer levels on nitrate-nitrogen (NO3-N) leaching in a silage maize field. The experiment included four irrigation levels (0.7, 0.85, 1.0, and 1.13 of soil moisture depletion, SMD) and three N fertilization levels (0, 142, and 189kgNha-1), with three replications. Ceramic suction cups were used to extract soil solution at 30 and 60cm soil depths for all 36 experimental plots. Soil NO3-N content of 0-30 and 30-60-cm layers were evaluated at planting and harvest maturity. Total N uptake (NU) by the crop was also determined. Maximum NO3-N leaching out of the 60-cm soil layer was 8.43kgNha-1, for the 142kgNha-1 and over irrigation (1.13 SMD) treatment. The minimum and maximum seasonal average NO3 concentration at the 60cm depth was 46 and 138mgl-1, respectively. Based on our findings, it is possible to control NO3 leaching out of the root zone during the growing season with a proper combination of irrigation and fertilizer management.Sprinkler irrigation Fertigation Nitrogen Environment Water quality Deficit irrigation

Persistence, recovery and root traits of tall fescue genotypes with different flowering date under prolonged water stress

International audienceClimate change models predict more frequent and severe droughts in the world. For the future adaptation of perennial forage grasses, identification and selection of genotypes with enhanced recovery and persistence under repeated drought is crucial. The aim of the present study was to investigate traits related to persistence, recovery, and root adaptation in three sets of tall fescue genotypes with different flowering date, after successive drought stress. A total of 72 genotypes of tall fescue (24 medium, 24 late, 24 early flowering) were assessed for agro-morphological traits and persistence during 2010-2014 under two levels of soil moisture. In 2015, irrigation was withheld and all genotypes were evaluated for drought recovery in the field. Then 18 genotypes were chosen based on field results to evaluate their root traits at two irrigation levels (control and intense drought stress) in pots. In the field, plant persistence decreased from year 2 to 5 under both control and intense drought stress conditions in all three sets of genotypes, although persistence of late flowering genotypes was higher. The results also indicated that most of the genotypes with greatest persistence had higher recovery after the final severe drought. Persistence and recovery were positively correlated with root length (RL), root area (RA), root volume (RV), root weight (RW) and root to shoot ratio (R/S) under both soil moisture. Moreover, genotypes with higher recovery after drought had more RL, RA, RV and R/S than others. Application of principle component analysis to identify genotypes of interest for future breeding programs is discussed

A principal components/singular spectrum analysis approach to ENSO and PDO influences on rainfall in western Iran

This paper analyzes the spatio-temporal variability of precipitation in western Iran by means of the Standardized Precipitation Index (SPI), calculated in annual and seasonal aggregations for wet and dry conditions over 46 synoptic stations with monthly data from 1957 to 2008. Regions of homogeneous SPI realizations were delimited using principal components analysis (PCA) to highlight major variation modes distinguishable in the basin and singular spectrum analysis (SSA) was performed over the reconstructed values of SPI to identify their oscillation modes. Extreme SPI values associated with El Nino\u2013Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) were also evaluated. Results show two significant oscillations around four and eight years on the SPI with an increase in precipitation variability since 1990 and a tendency to have less rain during the cold season and more rain during the warm season. We calculated standardized products among SPI, ENSO, and PDO to determine years in which the indices reinforce each other, 1986, 1992, 1999, and 2008 being particularly significant in the associations. These results are important for water managers in western Iran because they indicate significant changes in precipitation regimes associated with ENSO and PDO signals that will help to assess the occurrence of droughts and floods in the area