Regulated deficit irrigation improved fruit quality and water use efficiency of pear-jujube trees

Regulated deficit irrigation (RDI) was applied on field-grown pear-jujube trees in 2005 and 2006 and its effects on crop water-consumption, yield and fruit quality were investigated. Treatments included severe, moderate and low water deficit treatments at bud burst to leafing, flowering to fruit set, fruit growth and fruit maturation stages. Different deficit irrigation levels at different growth stages had significant effects on the fruit yield and quality. Moderate and severe water deficits at bud burst to leafing and fruit maturation stages increased fruit yield by 13.2-31.9% and 9.7-17.5%, respectively. Fruit yield under low water deficit at fruit growth and fruit maturation stages was similar to that of full irrigation (FI) treatment. All water deficit treatments reduced water consumption by 5-18% and saved irrigation water by 13-25% when compared to the FI treatment. During the bud burst to leafing stage, moderate and severe water deficits did not have effect on the fruit quality, but significantly saved irrigation water and increased fruit yield. Low water deficit during the fruit growth stage and low, moderate and severe water deficits during the fruit maturation stage had no significant effect on the fruit weight and fruit volume but reduced fruit water content slightly, which led to much reduced rotten fruit percentage during the post-harvest storage period. Such water deficit treatments also shortened the fruit maturation period by 10-15 d and raised the market price of the fruit. Fruit quality shown as fruit firmness, soluble solid content, sugar/acid ratio and vitamin C (V_C) content were all enhanced as a result of deficit irrigation. Our results suggest that RDI should be adopted as a beneficial agricultural practice in the production of pear-jujube fruit.     

Response of Clementina de Nules citrus trees to summer deficit irrigation. Yield components and fruit composition

The effects of mid-summer regulated deficit irrigation (RDI) treatments were investigated on Clementina de Nules citrus trees over three seasons. Water restrictions applied from July, once the June physiological fruit drop had finished, until mid September were compared with a Control treatment irrigated during all the season to match full crop evapotranspiration (ET_c). Two degrees of water restrictions were imposed based on previous results also obtained in Clementina de Nules trees ( [Ginestar and Castel, 1996] and [González-Altozano and Castel, 1999]). During the RDI period, deficit irrigation was applied based on given reductions over the ET_c, but also taking into account threshold values of midday stem water potential (Ψ_s) of −1.3 to −1.5 MPa for RDI-1 and of −1.5 to −1.7 MPa for RDI-2. Results showed that water savings achieved in the RDI-2 treatment impaired yield by reducing fruit size. On the contrary, the RDI-1 strategy allowed for 20% water savings, with a reduction in tree growth but without any significant reduction in yield, fruit size nor in the economic return when irrigation was resumed to normal dose about three months before harvest. Water use efficiency (WUE) in the RDI trees was similar or even higher than in Control trees. RDI improved fruit quality increasing total soluble solids (TSS) and titratable acidity (TA). In conclusion, we suggest that the RDI-1 strategy here evaluated can be applied in commercial orchards not only in case of water scarcity, but also as a tool to control vegetative growth improving fruit composition and reducing costs associated with the crop management.     

Assessment of maximum daily trunk shrinkage signal intensity threshold values for deficit irrigation in lemon trees

The response of adult Fino lemon trees (Citrus limon L. Burm. fil.) on sour orange (Citrus aurantium L.) to an irrigation schedule based exclusively on maximum daily trunk shrinkage (MDS) measurements was studied during the 2005-2006 and 2006-2007 seasons. Plants irrigated above their crop water requirements (T0 treatment) were compared with plants under deficit irrigation, whereby the MDS signal intensity (actual MDS/reference MDS) threshold values were maintained at around 1.15 (T1 treatment), 1.25 (T2 treatment) and 1.35 (T3 treatment). Cumulative crop evapotranspiration (ETc) values reached 536.9 and 719.4 mm during the first and the second season, respectively, and the cumulative amounts of applied water in the deficit irrigation treatments were 662.4 mm (T1, 2006-2007 season), 396.3 mm (T2, 2005-2006 season), 554.0 mm (T2, 2006-2007 season) and 220.3 mm (T3, 2005-2006 season), which generated mild, moderate and severe water stress in T1, T2 and T3 plants, respectively. Results indicated that measurements of MDS are suitable for scheduling irrigation, except for rainy periods of low evaporative demand. Therefore, to improve the precision of irrigation management, some changes in the irrigation protocol should be introduced, for instance, using higher MDS signal intensity threshold values and/or a lower irrigation frequency. According to market demand, lemon fruits were harvested on two occasions, showing no effect of irrigation treatment on total yield and total number of fruits per tree. T2 and T3 treatments resulted in a lower yield and number of fruits per tree at the first harvest and modified fruit characteristics. In contrast, the yield at first harvest and number of fruits per tree was not affected in T1 (92% ETc) plants and fruit characteristics were hardly impaired.     

The effects of contrasted deficit irrigation strategies on the fruit growth and kernel quality of mature almond trees

The aim of this study was to quantify and compare the effects of two different deficit irrigation (DI) strategies (regulated deficit irrigation, or RDI, and partial rootzone drying, PRD) on almond (Prunus dulcis (Mill.) D.A. Webb) fruit growth and quality. Five irrigation treatments, ranging from moderate to severe water restriction, were applied: (i) full irrigation (FI), irrigated to satisfy the maximum crop water requirements (ET_c); (ii) regulated deficit irrigation (RDI), receiving 50% of ET_c during the kernel-filling stage and at 100% ET_c throughout the remaining periods; and three PRD treatments – PRD₇₀, PRD₅₀ and PRD₃₀ – irrigated at 70%, 50% and 30% ET_c, respectively, during the whole growth season. The DI treatments did not affect the overall fruit growth pattern compared to the FI treatment, but they had a negative impact on the final kernel dry weight for the most stressed treatments. The allocation of water to the different components of the fruit, characterized by the fresh weight ratio of kernel to fruit, appeared to be the process most clearly affected by DI. Attributes of the kernel chemical composition (lipid, protein, sugar and organic acid contents) were not negatively affected by the intensity of water deprivation. Overall, our results indicated that PRD did not present a clear advantage (or disadvantage) over RDI with regard to almond fruit growth and quality.     

调亏灌溉对枣树生长与果实品质和产量的影响

为探究开花坐果期调亏灌溉对南疆绿洲区灰枣树品质和产量的影响,以大田生长7年的成龄灰枣树为试验试材,在开花坐果期进行轻度调亏处理T1(80%ET₀,其中ET₀为阶段水面蒸发量)、中度调亏处理T2(60%ET₀)、重度调亏处理T3(40%ET₀)、对照处理CK(100%ET₀),探究开花坐果期调亏灌溉对灰枣树枣吊生长、果实品质、产量、经济效益等影响.结果表明:开花坐果期调亏对枣吊生长速率有显著影响,且随着水分胁迫的加剧,对枣吊生长的抑制作用越大;调亏灌溉对提高单果重、可溶性固形物、糖酸比影响显著,其中,中度处理T2灰枣最终产量提高了9.6%,经济效益增加33.92%.因此,开花坐果期中度调亏有利于提高灰枣品质、产量及经济效益.     

Response of Leucadendron ‘Safari Sunset’ to regulated deficit irrigation: Effects of stress timing on growth and yield quality

Leucadendron ‘Safari Sunset’ is the most important cultivar in the worldwide Protea industry. The commercial product consists of long branches that terminate in a female inflorescence (“head”), surrounded by large, deep-wine-red leaves. The dimensions of the colourful head have a predominant effect on the attractiveness and price of ‘Safari Sunset’ in the floricultural markets. The objective of the present study was to assess the effect of regulated deficit irrigation at different growth phases, on plant growth and crop quality. The experiment included two control treatments applied throughout the growth season: non-stress irrigation and deficit irrigation (40% of non-stress irrigation). The intermittent deficit irrigation treatments included periodic water stress during the fast vegetative growth (phase I) or during the head development (phase II). In addition, short events of water stress in the middle of the growth season, followed by a water non-stress irrigation regime were tested. Water stress throughout the growth season induced significantly low vegetative growth and small heads. Intermittent water stress (both periods) impaired crop quality, mainly because of reduction of head dimensions. Short or moderate periodic water stress barely affected head dimensions or the number of marketable branches, but impaired the product by diminishing the leaf dimensions. Continuous measurements of soil-water tension or plant indicators such as stem diameter or length were found to be very useful for on-line control of plant-water status.     

Response of vegetative growth and fruit development to regulated deficit irrigation at different growth stages of pear-jujube tree

In order to investigate the response of vegetative growth, fruit development and water use efficiency to regulated deficit irrigation at different growth stages of pear-jujube tree (Zizyphus jujube Mill.), different water deficit at single-stage were treated on field grown 7-year old pear-jujube trees in 2005 and 2006. Treatments included severe (SD), moderate (MD) and low (LD) water deficit treatments at bud-burst to leafing (I), flowering to fruit set (II), fruit growth (III) and fruit maturation (IV) stages. Compared to the full irrigation (control), different water deficit treatments at different growth stages reduced photosynthesis rate (P_n) slightly and transpiration rate (T_r) significantly, thus it improved leaf water use efficiency (WUE_L, defined as the ratio of P_n to T_r) by 2.7-26.1%. After the re-watering, P_n had significant compensatory effect, but T_r was not enhanced significantly, thus WUE_L was improved by 31.4-42.2%. I-SD, I-MD, II-SD and II-MD decreased new shoot length, new shoot diameter and panicle length by 8-28%, 13-23% and 10-31%, respectively. Simultaneously, they reduced leaf area index (LAI) and pruning amount significantly. Flowering of pear-jujube tree advanced by 3-8 days in the water deficit treatments at stage I, Furthermore, SD and MD at stage I increased flowers per panicle and final fruit set by 18.9-40.5% and 15.5-36.6%, respectively. After a period of re-watering, different water deficit treatments at different growth stages improved the fruit growth rate by 15-30% without reduction of the final fruit volume. Compared to the control, I-MD, I-SD, I-LD, I-MD and I-SD treatments increased fruit yield by 13.2-31.9%, but reduced water consumption by 9.7-17.5%, therefore, they enhanced water use efficiency at yield level (WUE_Y, defined as ratio of fruit yield to total water use) by 17.3-41.4%. Therefore, suitable period and degree of water deficit can reduce irrigation water and restrain growth redundancy significantly, and it optimize the relationship between vegetative growth and reproductive growth of pear-jujube trees, which maintained or slightly increased the fruit yield, thus water use efficiency was significantly increased.     

Response of citrus trees to deficit irrigation during different phenological periods in relation to yield, fruit quality, and water productivity

Four strategies of deficit irrigation based on a different water-stress ratio (WSR) applied in each phenological stage, and a control treatment were implemented in 11-year-old citrus trees (Citrus sinensis L. Osb. Cv. Navelina) grafted onto carrizo citrange (C. sinensis L. Osb. × Poncirus Trifoliata L. Osb.). The midday stem-water potential and stomatal conductance were measured during the periods considered, and these parameters were used to estimate the plant-water status. Integrated stem-water potential (Ψ_Int) and integrated stomatal conductance (g_Int) were calculated for all treatments and used as a water-stress indicator for the crop. Reference equations were formulated to quantify the relations between water-stress indicators (WSR, Ψ_Int, g_Int) and the crop response, expressed as yield, yield components, and fruit-quality parameters under limited seasonal water availability. Significant differences in yield were found in the second year of experiment between the stressed treatments and control, although these differences were evident during the first year. The main effects were detected in treatments with a water-sever stress applied during the flowering and fruit-growth phases. When this degree of stress was applied during the maturity phase, it was reflected mainly in fruit-quality parameters (total soluble solids, and titrable acidity). These results lead to the conclusion that, in mature orange trees, deficit irrigation affects yield and fruit quality, while enabling water savings of up to 1000 m³ ha⁻¹. Therefore, yield declined on average 10-12% but boosted water productivity 24% with respect to the fully irrigated treatment. Regarding the water-stress indicators used, Ψ_Int and g_Int showed highly significant correlations with the yield and fruit-quality parameters.     

Effects of soil water deficit on yield and quality of processing tomato under a Mediterranean climate

In order to assess the effect of soil water deficit (SWD) during fruit development and ripening, on yield and quality of processing tomato under deficit irrigation in the Mediterranean climate, an open-field experiment was carried out in two sites differing from soil and climatic characteristics, in Sicily, South Italy. Six irrigation treatments were studied: no irrigation following plant establishment (NI); 100% (F = full) or 50% (D = deficit) ET_c restoration with long-season irrigation (L) or short-season irrigation up to 1st fruit set (S); and long-season irrigation with 100% ET_c restoration up to beginning of flowering, then 50% ET_c restoration (LFD). The greatest effect of increasing SWD was the rise in fruit firmness, total solids and soluble solids (SS). A negative trend in response to increasing SWD was observed for fruit yield and size. Tough yield and SS were negatively correlated, the final SS yield under the LD regime was close to that of LF, and 47% water was saved. However, SS seems to be more environmental sensitive than SWD, since it varied more between sites than within site. The variations between sites in fruit quality response to deficit irrigation demonstrate that not only SWD but also soil and climatic characteristics influence the quality traits of the crop.     

Water use efficiency and fruit quality of table grape under alternate partial root-zone drip irrigation

Two-year field experiments were conducted to investigate the effect of alternate partial root-zone drip irrigation on fruit yield, fruit quality and water use efficiency of table grape (Vitis vinifera L. cv Rizamat) in the arid region of northwest China. Three irrigation treatments were included, i.e. CDI (conventional drip irrigation, both sides of the root-zone irrigated), ADI (alternate drip irrigation, both sides of the root-zone irrigated alternatively with half the water) and FDI (fixed drip irrigation, only one side of the root system irrigated with half the water). Results indicated that compared to CDI, ADI kept the same photosynthetic rate (P_n) but reduced transpiration rate, thus increased leaf water use efficiency (WUE) of table grape. And diurnal variation of leaf water potential showed no significant differences during 7.00 a.m. to 14.00 p.m. in both years. ADI also produced similar yield and improved WUE_ET by 26.7–46.4% and increased the percentage of edible grape by 3.88–5.78%, vitamin C content in the fruit by 15.3–42.2% and ratio of total soluble solid concentration/titrated acid in both years as compared to CDI. Thus ADI saved irrigation water, improved the water use efficiency and fruit quality of table grape without detrimental effect on the fruit yield in arid region.     

Economic analysis of navel orange cv. ‘Lane late’ grown on two different drought-tolerant rootstocks under deficit irrigation in South-eastern Spain

During a three-year period, we evaluated the profitability of a deficit-irrigation (DI) treatment in mature ‘Lane late’ navel orange (Citrus sinensis (L.) Osb.) trees grafted on two different drought-tolerant rootstocks, ‘Cleopatra’ mandarin (Citrus reshni Hort. ex Tanaka) and ‘Carrizo’ citrange (C. sinensis (L.) Osb. × Poncirus trifoliata L. Raf.). The irrigation strategies for each rootstock were a control treatment, irrigated at 100% crop evapotranspiration (ETc) during the entire season, and a DI, irrigated at 100% ETc except during phase I (fruit set) and phase III (fruit maturation) of fruit growth, when complete irrigation cut-off was applied. The main difference found was between rootstocks, orchards of ‘Carrizo’ being 39% more profitable than those of ‘Cleopatra’ due to the greater yield and fruit size and higher price (0.02 € kg⁻¹) for trees on ‘Carrizo’. The application of the DI treatment increased the profit for ‘Carrizo’ since the decrease in pruning costs was greater than the reduction of incomes. The profit of ‘Cleopatra’ under DI decreased due to yield reduction. The variable and fixed operating costs during the growth cycle were decreased by the DI treatment, with a reduction of fertiliser (40%), water applied (30%) and electricity consumed (30%) compared with the control. In addition, in ‘Carrizo’, DI decreased the pruning (16%), machinery (11%) and phytosanitary products (9%) costs as a result of the reduction of the canopy growth. From these results, we conclude that, with similar crop management, orchards of ‘Lane late’ navel orange on ‘Carrizo’ rootstock were more profitable than those on ‘Cleopatra’ under deficit-irrigation conditions.     

Is partial root-zone drying an effective irrigation technique to improve water use efficiency and fruit quality in field-grown wine grapes under semiarid conditions?

We investigated the effects of partial root-zone drying (PRD) applied at different periods on leaf water relations, vegetative development, fruit yield, must and wine quality in wine grapes (Vitis vinifera L. cv. Monastrell) during a 3-year field experiment in order to determine the importance of the timing of PRD application on physiological and agronomical vine response under semiarid conditions. Two irrigation treatments were applied: conventional drip irrigation (CI) and PRD. Both treatments received the same annual water quantity. Each year the PRD treatment was applied at different periods of the growth cycle. In 1999 PRD was applied from veraison to harvest (end July–early September); in 2000 from fruit set to harvest (mid June–early September); and in 2001 PRD from budburst to harvest (mid April–early September). Leaf water relations and gas exchange during the experimental period were not significantly affected by PRD treatment. In 1999 and 2000 there was no significant treatment effect on vegetative development, yield or fruit quality. However, in 2001 (when PRD was applied from budburst to harvest), reproductive and vegetative development was clearly altered in PRD vines. Fruit set percentage and vegetative development (shoot length, pruning weight and primary and lateral leaf area) were significantly increased in PRD vines compared to CI. This resulted in both higher yield (kg per vine) (43%) and water use efficiency (40%) compared to CI vines. Berry number per cluster and cluster weight were also significantly increased in PRD vines. Notwithstanding higher yield in PRD vines and a similar berry size, the must and wine quality was not significantly altered, indicating a higher synthesis and accumulation of photoassimilates and metabolites in the berries of PRD vines. We conclude that there was an positive effect on vegetative and reproductive growth when long-term PRD was applied from the beginning of growing season (budburst), suggesting that early onset of PRD is desirable to intensify PRD response under these semiarid conditions. Nevertheless from these results we need to further investigate the long- and short-term effects of PRD, with moderate water amounts, on vegetative and reproductive development such as flowering and fruit set processes in wine grapes.     

液体硅肥对青脆李品质的影响

液体硅肥对青脆李树进行“根部灌施”和“叶面喷施”两种处理方式。果实成熟后测定其单果重、可溶性固形物、硬度、糖、酸组分和Vc含量。结果表明：施硅处理后单果重、可溶性固形物、果糖、Vc等品质指标较对照有明显提高,根部灌施有效硅为34g（0.4kg液体硅肥原液）、叶面喷施有效硅为1.92g（16ml硅肥稀释900倍）效果较优。     

番茄果实不同发育阶段水分亏缺对其风味品质的影响

对番茄果实膨大期和成熟期各设充分供水、中度和重度亏水3个水平,进行盆栽试验,分析了膨大期和成熟期亏水水平及其交互作用对番茄可溶性固形物、可溶性糖、可滴定酸含量及糖酸比的影响.结果表明:果实膨大期、成熟期亏水水平及其交互作用对番茄可溶性固形物、可溶性糖、可滴定酸含量及糖酸比有显著影响(膨大期亏水对可溶性糖含量影响除外);成熟期中度亏水时,膨大期中度亏水较充分供水使可滴定酸和可溶性固形物含量显著提高,增幅分别为57.8%和29.4%,糖酸比显著降低,降幅为46.6%;膨大期重度亏水时,成熟期重度亏水较充分供水使可溶性糖、可溶性固形物和糖酸比依次减小49.3%,33.9%和75.0%,而使可滴定酸含量增加129.7%;果实发育阶段持续重度亏水较充分供水使可溶性糖、可溶性固形物含量和糖酸比分别减小16.5%,16.0%和36.5%.表明番茄果实膨大期和成熟期的水分供应均会对其风味品质产生显著影响,而且,各时期单独亏水的效应与其他时期的水分供应有密切关系;两时期适度亏水可显著改善番茄果实风味品质,膨大期到成熟期持续重度亏水反而不利于其风味品质的提高,只是获得了较高的酸度.     

Positive impact of regulated deficit irrigation on yield and fruit quality in a commercial citrus orchard [Citrus sinensis (L.) Osbeck, cv. salustiano]

The impact that different regulated-deficit irrigation (RDI) treatments exert on a 12-year-old orange orchard (Citrussinensis L. Osbeck, cv. salustiano) was studied from 2004 to 2007. The experiment consisted of a control irrigation treatment which was irrigated at 100% of the crop evapotranspiration (ET_c) values for the whole season, and three deficit treatments imposed as a function of the water-stress index (WSI), which is defined as the ratio of the actual volume of water supply to the ET_c rate. In our case, these WSI values were 0.75, 0.65, and 0.50, respectively. The stem-water potential at noon (Ψ_Stem) was used as a parameter to estimate the water status of the plant. Yield and fruit quality was evaluated at harvest in each treatment (taking into account the temporal variability of the results due to the climatic characteristics of each of the years of this study) and an overall analysis was made using the whole dataset. Significant differences were found in fruit quality parameters (total soluble solids and titrable acidity), which also showed significant regression coefficients with the values of the integrated stem-water potential. These results led us to conclude that in mature orange trees grown under these conditions, regulated-deficit irrigation has important and significant effects on the final fruit quality, but the effects are not so clear-cut in tree yield, where the differences in the case of reducing a 50% of the crop ET_c, were not considered to be statistically significant despite an approximate 10% decrease in fruit yield. A global rescaled distance cluster analysis was performed in order to summarize the main relationships between the variables evaluated and to establish a different correlation matrix. Finally, a classification tree was derived and principal-component analysis was undertaken in order to identify and evaluate the variables which had the strongest effect on the crop response to different irrigation treatments.     

调亏灌溉对大棚滴灌甜瓜生长发育的影响

在大棚滴灌条件下对厚皮甜瓜伊丽莎白不同生育期进行不同程度的亏缺灌溉,研究调亏灌溉对其植株生长、产量、品质及水分利用效率的影响.以土壤相对含水量为标准,在营养生长期和生殖生长期分别设置不同的土壤水分灌溉下限处理,分别是T1(75%~75%),T2(75%~55%),T3(65%~65%),T4(55%~75%),T5(55%~55%)5个试验处理.结果表明:在营养生长期,随着水分亏缺程度的加大,株高、茎粗、叶面积均呈减小趋势.在果实发育阶段,营养生长期及生殖生长期的水分亏缺对果实的生长、产量都有影响,均随亏缺程度的加大而降低,产量以处理T1和T2的最高,T5的最低,T3的大于T4的,各处理间差异具有统计学意义.水分利用效率为处理T2的最高,T1和T4的较低,T2与T4相比,在灌水基本相同的条件下,产量增加了26.2%,水分利用效率提高了27.7%.品质方面,水分亏缺提高了TSS含量;在营养生长期充分灌溉、生殖生长期亏水灌溉可以提高可溶性蛋白、游离氨基酸、维生素C的含量;而营养生长期亏水灌溉、生殖生长期充分灌溉有利于可滴定酸的合成.经综合分析,认为处理T2的灌溉下限设置可以作为武汉地区大棚滴灌条件下的甜瓜灌溉制度.     

Regulated deficit irrigation effects on growth, yield, grape quality and individual anthocyanin composition in Vitis vinifera L. cv. ‘Tempranillo’

Regulated Deficit Irrigation (RDI) is an irrigation scheduling technique, originally developed for fruit orchards, that has been successfully adapted for winegrape production. The aim of this work is to evaluate the effect of RDI in vegetative growth, yield and harvest quality in ‘Tempranillo’ vineyards grown under semiarid conditions typical in Mediterranean areas. Two RDI strategies were compared with conventional irrigation practices (CI). CI that consisted in a progressive increase in water deficit as summer progressed, whereas RDI strategies (RDI1 and RDI2) had in common a deficit period just after fruit set and, in RDI2, vines were subjected to an additional stress period shortly after veraison. The experiment was carried out in four consecutive seasons in a commercial vineyard.Water stress at the beginning of berry development resulted in an important reduction of both vegetative growth and berry weight in RDI strategies. No differences in sugar concentration were found between treatments, and RDI berries tended to have lower acidity. The most relevant effect of RDI strategies on grape quality was an increase in anthocyanin and phenolics concentration. In RDI1 berries, this increase was mainly an indirect consequence of smaller berry size. However, in the RDI2 treatment the higher berry anthocyanin concentration reported was not exclusively due to a reduction in berry size. Since harvest quality has been clearly improved by any of the RDI strategies in both years, it can be concluded that RDI constitutes an interesting technique to be applied in ‘Tempranillo’ vineyards grown in semiarid areas aiming to obtain high quality grape.     

绿洲灌区膜下滴灌调亏对辣椒品质及产量的影响

为揭示滴灌水分亏缺对辣椒营养品质及产量的影响,以"陇椒6号"为对象,在辣椒苗期分别施加轻度(65％～75％田间持水量)、中度(55％～65％田间持水量)和重度水分调亏(45％～55％田间持水量),在盛果期和后果期分别施加轻度水分亏缺,以全生育期充分供水(75％～85％田间持水量)为对照,分别测定各水分处理辣椒青果营养品...     

Effect of modern irrigation methods on growth and energy production of sweet sorghum (var. Keller) on a dry year in Central Greece

The subject of this project is to estimate the growth and productivity of sweet sorghum [Sorghum bicolor (L.)] var. Keller, under two different irrigation methods – the conventional surface drip method (two treatments) and the subsurface drip method – in a dry year in Central Greece, as an energy crop for the production of bio-ethanol. A field experiment was carried out on the experimental farm of the University of Thessaly during 2005, comprising of a completely randomized block design with four treatments in four blocks, including control (non-irrigated). In the treatments of surface drip method the evapotranspiration needs were satisfied by using full (100% ETm) and supplement (80% ETm) irrigation doses, while in the treatments of subsurface drip method only supplement irrigation water was used (80% ETm) with the aim of more efficient water conservation. Irrigation was fully automated, and application depths were determined, using a class A open evaporation pan for matching the evapotranspiration needs. The growth of the crop was measured by means of plant height and leaf area index, which were determined periodically throughout the growing period. Fresh and dry biomass productions were measured over six harvests covering the entire growth and production process of cultivation. The results of the first year demonstrated a clear superiority of the subsurface drip method on plant heights, leaf area index and total fresh and dry biomass production compared with the surface drip method for equal values of irrigation water. Maximum yield was attained by mid-September, before crop maturation, something which should be taken into consideration when choosing the best harvesting time of the crop. After late September, large negative growth rates were recorded, resulting in an appreciable drop in the final fresh and dry matter yield.     

Effects of grapevine (Vitis vinifera L.) water status on water consumption, vegetative growth and grape quality: An irrigation scheduling application to achieve regulated deficit irrigation

Precision irrigation in grapevines could be achieved using physiologically based irrigation scheduling methods. This paper describes an investigation on the effects of three midday stem water potential (midday Ψ_S) thresholds, imposed from post-setting, over water use, vegetative growth, grape quality and yield of grapevines cv. Cabernet Sauvignon. An experiment was carried out on a vineyard located at the Isla de Maipo, Metropolitana Region, Chile, throughout the 2002/03, 2003/04 and 2004/05 growing seasons. Irrigation treatments consisted in reaching the following midday Ψ_S thresholds: −0.8 to −0.95 MPa (T1); −1.0 to −1.2 MPa (T2) and −1.25 to −1.4 MPa (T3) from post-setting to harvest. Results showed significant differences in grape quality components among treatments and seasons studied. In average, T3 produced smallest berry diameter (6% reduction compared to T1), high skin to pulp ratio (13% increment compared to T1) and significant increments in soluble solids and anthocyanins. Improvements in grape quality attributes were attributed to mild grapevine water stress due to significant reductions in water application (46% for T2 and 89% for T3 less in average, both compared to T1). This study found significant correlations between midday Ψ_S and berry quality components, no detrimental effects on yield by treatments were found in this study. This research proposes a suitable physiological index and thresholds to manage RDI and irrigation scheduling on grapevines to achieve high quality grapes on mild water stress conditions.