Pablo Botía

Effects of regulated deficit irrigation under subsurface drip irrigation conditions on vegetative development and yield of mature almond trees

The influence of several regulated deficit irrigation (RDI) strategies, applied under subsurface drip irrigation (SDI), on vegetative development and yield parameters in mature almond (Prunus dulcis (Mill.) D.A. Webb, cv. Cartagenera) trees was analysed during a 4-year field experiment. Five treatments were applied: T1 (100% crop evapotranspiration (ETc), full season); T2 (irrigated at 100% ETc except in the kernel-filling stage (20% ETc)); T3 (equal to T2 but in SDI); T4 (SDI, 100% ETc, except in the kernel-filling stage (20% ETc) and post-harvest (75% ETc)); T5 (SDI, 100% ETc except in the kernel-filling stage (20% ETc) and post-harvest (50% ETc). A close correlation between applied water, plant water status (Ψpd) and tree growth parameters was observed. After four years, the vegetative development in T5 was reduced significantly due to a larger annual cumulative effect of water stress on growth processes, resulting in a smaller tree size (trunk and branch growth, canopy volume and pruning weight) compared to other treatments. Moreover, water stress during kernel-filling produced a significant reduction in the leaf expansion rate and a stimulation of premature leaf abscission, resulting in a smaller tree leaf area in this treatment. SDI produced a greater horizontal distribution of fine roots in the soil profile than surface drip system. The RDI practices applied under subsurface drip irrigation stimulated a deeper root development (40–80 cm) than surface treatments (0–40 cm), producing also a higher root density in the subsurface treatments watered the least (T4 and T5). Water stress during the pre- and post-harvest periods had no important effect on bud development, bloom, fruit growth or fruit abscission. Moreover, there were no significant reductions in kernel dry weight or kernel percentage. Reductions in kernel yield were significant compared to T1, being of 11% in T2, 15% in T3, 20% in T4 and 22% in T5. Water use efficiency (kg m−3) was increased significantly in the SDI treatments T4 and T5. A significant correlation between kernel yield and tree growth parameters was observed. We conclude that the application of overall reductions of water use of up to 50% during high water stress sensitivity periods (such as post-harvest) under SDI system, is a promising alternative for water management in semiarid regions in order to improve water use efficiency. Nevertheless prolonged water stress during kernel-filling and post-harvest can reduce excessively the vegetative development of almond, negatively affecting the long-term yield response.

Response of sweet orange cv ‘Lane late’ to deficit-irrigation strategy in two rootstocks. II: Flowering, fruit growth, yield and fruit quality

We evaluated the effects of a deficit-irrigation (DI) strategy in mature ‘Lane late’ sweet orange (Citrus sinensis (L.) Osb.) trees grafted on two different drought-tolerant rootstocks, ‘Cleopatra’ mandarin (Citrus reshni Hort. ex Tanaka) and ‘Carrizo’ citrange (Citrus sinensis (L.) Osbeck x Poncirus trifoliata L.). Two treatments were applied: a control treatment, irrigated at 100% of crop evapotranspiration (ETc) during the entire season, and a DI treatment, irrigated at 100% ETc, except during phases I (initial fruit-growth period,) and phase III (final fruit-growth period, ripening, harvest), when no irrigation was applied. Flowering, fruit abscission and fruit growth of trees on ‘Carrizo’ were more affected by DI than on ‘Cleopatra’. Deficit irrigation reduced yield in both rootstocks due mainly to a decrease in the number of fruits. The phase most sensitive to drought stress was phase I. Moreover, DI altered fruit quality depending on the period when drought stress was applied. Fruit quality was modified by DI: total soluble sugars and titratable acidity increased when a severe drought stress occurred only in phase III but only increased the peel/pulp ratio if it occurred only in phase I. The quality of fruits from trees on ‘Carrizo’ under DI was affected more than that of fruits from trees on ‘Cleopatra’. Under DI in semi-arid regions ‘Cleopatra’ mandarin can mitigate more the negative effects of drought stress on yield and fruit quality than ‘Carrizo’ citrange.

Effects of regulated deficit irrigation under subsurface drip irrigation conditions on water relations of mature almond trees

The influence of several regulated deficit irrigation (RDI) strategies under subsurface drip irrigation (SDI) conditions on water relations and gas exchange activity was analysed during a four year period for mature trees of a local variety of almond (Prunus dulcis (Mill.) D.A. Webb, cv. Cartagenera), in a commercial plantation in the district of Aljorra, Murcia (Southern Spain). Five treatments were applied: T1 (surface drip), which was irrigated at 100% ETc (crop evapotranspiration) for the full season, applying 603 mm per year; T2 (surface drip), irrigated at 100% ETc, except during the kernel-filling stage (from early June to early August), when 20% ETc was applied; T3 (SDI), equal to T2, but in subsurface drip irrigation; T4 (SDI), irrigated at 100% ETc, except during kernel- filling (20% ETc) and post-harvest (75% ETc); T5 (SDI), equal to T4, but a greater reduction of post-harvest irrigation (50% ETc). The severity of water stress was characterised by measurements of soil water content (θv), predawn leaf water potential (Ψpd), osmotic potential (Ψπ), relative water content (RWC), and gas exchange rates. Under stress (during the kernel-filling stage) and non-stress conditions (during active growth and post-harvest periods) in treatments T2, T3 and T4 there were not significant differences in the soil water content, nor in the plant water status and gas exchange parameters measured. Only T5 (SDI) showed a significant reduction in gas exchange activity at the end of the kernel-filling stage (point of maximum stress). This response was closely correlated with the severity of the stress reached. Minimum values of Ψpd reached in this period were −2.37 MPa in T2, −2.26 MPa in T3, −1.95 MPa in T4 and −2.52 MPa in T5. Maximum reductions in photosynthesis rate (A), with regard to the control, were 64%, 61%, 58% and 75%, respectively. Reductions in A,E and stomatal conductance (gs) in response to severe water stress were reversible. Although soil and plant water status recovered rapidly when trees were irrigated post-harvest, gas exchange activity (gs,E and A) recovered more slowly in all treatments. T5 showed a recovery of soil water status that was slower and incomplete compared to the other treatments, post-harvest (early August-early September), although gas exchange activity was not affected in this period. These results indicate that these RDI strategies, with a severe irrigation deprivation during kernel-filling (20% ETc), and a recovery post-harvest at 75% ETc or up to 50% ETc under SDI, can be adequate in this orchard under semiarid conditions, due to a higher water application efficiency of this irrigation system, saving between 220–273 mm year−1 irrigation water.

Effects of salinity and rate of irrigation on yield, fruit quality and mineral composition of 'Fino 49' lemon

Potential problems associated with saline irrigation waters can be compounded by irrigation practices. Methods for water application become of prime importance under saline conditions. The effect of irrigation water quantity and salinity on fruit yield, fruit quality and leaf mineral composition were studied in a field experiment with 6-year-old lemon trees, cv. Fino 49, on the Macrophylla (Citrus Macrophylla Wester) rootstock during 1998/2000. Trees were irrigated with three different qualities of water, having an electrical conductivity 1, 2.5 and 4 dS/m, respectively. For each salinity treatment, trees were irrigated with two different quantities of water, 100 and 125% crop evapotranspiration. Lemon fruit yield significantly decreased with increasing salinity, due to a decrease in the number of fruits per tree. This reduction was caused by an increase in fruitlet drop off induced by salinity. A significant increase of lemon fruit yield was observed in the last year by increasing the quantity of water. Salinity and amount of water applied affected fruit quality. The percentage of fruit juice, with respect to the total fruit weight, was greater in fruits from the control than for those in the salinity treatments. The opposite effect was observed for peel and pulp contents. Titratable acidity (TA) and total soluble solids (TSS) decreased with salinity, although the ratio TSS:TA was similar in all treatments. Chloride and sodium concentrations in leaves were raised by salinity and amounts of water applied. Data on accumulation of other nutrients in relation to salinity, water application and season are also presented. # 2002 Elsevier Science B.V. All rights reserved.

Partial rootzone drying increases water-use efficiency of lemon Fino 49 trees independently of root-to-shoot ABA signalling

To determine whether irrigation strategy altered the sensitivity of Citrus leaf gas exchange to soil, plant and atmospheric variables, mature (16-year-old) Fino 49 lemon trees (Citrus limon (L.) Burm. fil. grafted on Citrus macrophylla Wester) were exposed to three irrigation treatments: control (irrigated with 100% of crop potential evapotranspiration, ETc), deficit irrigation (DI) and partial rootzone drying (PRD) treatments,which received 75% ETc during the period of highest evaporative demand and 50% ETc otherwise. Furthermore, to assess the physiological significance of root-to-shoot ABA signalling, the seasonal dynamics of leaf xylem ABA concentration ([X-ABA]leaf) were evaluated over two soil wetting-drying cycles during a 2-week period in summer. Although stomatal conductance (gs) declined with increased leaf-to-air vapour pressure deficit (LAVPD), lower leaf water potential and soil water availability, [X-ABA]leaf was only related to stomatal closure in well irrigated trees under moderate (<2.5kPa) atmospheric vapour pressure deficit (VPD). Differences in [X-ABA]leaf were not detected between treatments either before or immediately after (<12h) rewatering the dry side of PRD trees. Leaf water potential was higher in control trees, but decreased similarly in all irrigation treatments as daily LAVPD increased. In contrast, DI and PRD trees showed lower stomatal sensitivity to LAVPD than control trees. Although DI and PRD decreased stomatal conductance and photosynthesis, these treatments did not significantly decrease yield, but PRD increased crop water use efficiency (WUE) by 83% compared with control trees. Thus PRD-induced enhancement of crop WUE in a semiarid environment seems to involve physiological mechanisms other than increased [X-ABA]leaf.

Influence of deficit irrigation timing on the fruit quality of grapefruit (Citrus paradisi Mac.).

The irrigation necessities for grapefruit production are very high. Due to the scarcity of water resources, growers use deficit irrigation (DI) - which could affect the fruit quality. Different DI strategies were studied: Control (irrigated at 100% ETc) and T1, T2 and T3 (50% ETc at phases I, II and III of fruit growth, respectively). Strategy T1 only delayed external maturation depending on the duration of the water stress. High water stress in T2 delayed fruit maturation, increased acidity and reduced the sugar concentration. Under T2, trees suffering moderate water stress showed increased flavonoid and phenolic contents but decreased lycopene levels. External maturation was delayed in T3 when severe stress occurred during the first part of phase III. Strategy T3 advanced internal ripening when moderate water stress occurred during the first 40 days of phase III, increasing sugar accumulation, promoted by the high acidity of the fruits. Moderate water stress also increased β-carotene, flavonoids and phenolics levels.

Partial root zone drying exerts different physiological responses on field-grown grapevine (Vitis vinifera cv. Monastrell) in comparison to regulated deficit irrigation

Regulated deficit irrigation (RDI) and partial root zone irrigation (PRI) were compared for 4 years at two irrigation volumes (110mm year-1 (1) and 78mm year-1 (2)) in field-grown grafted Monastrell grapevines (Vitis vitifera L.) to distinguish the effects of deficit irrigation from specific PRI effects. PRI-1 and RDI-1 vines received ~30% of the crop evapotranspiration (ETc) from budburst to fruit set, 13-15% from fruit set to veraison and 20% from veraison to harvest. RDI-2 and PRI-2 vines received around 20% of ETc from budburst to fruit set, no irrigation from fruit set to veraison, and recovery (21-24% ETc) thereafter. Compared with RDI-1, PRI-1 increased irrigation depth and total soil water (θv) availability in the root zone, and stimulated greater fine root growth and water uptake. Increased soil volume exploration supported greater canopy water use, vegetative development, biomass accumulation and internal water storage capacity. PRI-1 vines had higher stomatal conductance, lower leaf-level water use efficiency and increased leaf xylem sap concentration ([X-ABA]leaf) following reirrigation. Compared with RDI-2, PRI-2 decreased total θv availability, fine root growth and water uptake, gas exchange, leaf water status, [X-ABA]leaf, biomass accumulation and storage capacity. Xylem ABA decreased with total θv availability in PRI-2, probably from limited sap flow when θv in drying soil was low (≈20%). For this rootstock-scion combination, high irrigation volumes applied to the wet part of the roots (θv>30%) are critical for increasing root-to-shoot ABA signalling and growth, and improving performance under semiarid conditions.

Uptake, Transport, and Concentration of Chloride and Sodium in Three Citrus Rootstock Seedlings

ABSTRACT Seedlings of three citrus rootstocks, sour orange (Citrus aurantiumL.; SO), Carrizo citrange (Citrus sinensis L., Osbeck x P. trifoliata L. Ref.; CA), and Macrophylla (Citrus macrophylla Wester; MA) were grown in nutrient solution and exposed for 60 days to different levels of salinity (0, 10, 20, 40, or 80 mM NaCl). The effects of the salinity treatments on growth, uptake, transport, and accumulation of Cl− and Na+ ions, in leaves and roots, were studied. Rootstock differences in leaf Cl− and Na+ concentrations were less evident at low salinity (10–20 mM NaCl) and clearly observed at higher external NaCl (40–80 mM NaCl). The most salt-tolerant rootstock was sour orange (SO), which experienced less growth reduction even when it accumulated high concentrations of Cl− and Na+ in the leaves. In addition, SO maintained the uptake and transport rates of ions similarly during the experiment, at all salinity levels. However, in Macrophylla (MA) and Carrizo (CA), at 40 and 60 days, the uptake and transport rates were greatly reduced for both ions, values being close to those of the control plants. CA and MA had high transport rates of Cl− and Na+ at low and moderate salinity, leading to a rapid influx of ions to the shoot and a reduction of growth. The analysis of ion accumulation and uptake rates within the leaves and roots indicated the absence of a direct correlation between vigor and salt tolerance at high salinity. The net transport rate to leaves in the first 20 days seemed to be the main factor regulating Cl− and Na+ concentrations in the leaves.

Transcriptional profile analysis of young and mature leaves of citrus trees acclimated to salinity

11 paginas.-- 3 figuras.-- 2 tablas.-- 32 referencias.-- Articulo publicado en XII International Citrus Congress - International Society of Citriculture