Comparative effects of deficit irrigation (DI) and partial rootzone drying (PRD) on soil water distribution,water use,growth and yield in greenhouse grown hot pepper

This study was conducted to compare two water-saving practices, deficit irrigation (DI) and partial rootzone drying (PRD), and examine how they affected soil water distribution, water use, growth and yield of greenhouse grown hot pepper compared to commercial irrigation (CI). Control (CI) in which irrigation water was applied to both sides of the system when soil water content was lower by 80% of field capacity; deficit irrigation (DI50, DI75) in which 50% and 75% irrigation water of CI supplied to both sides of the root system; 1PRD with half of the root system exposed to soil drying and other half kept well-watered with 50% irrigation water of CI, and 2PRD with 50% irrigation water of CI supplied, half to fixed side of the root system. The results showed mean soil volumetric water content of DI75, DI50, 1PRD and 2PRD were lower by 21.06%, 28.32%, 24.48% and 34.76%, respectively than that of CI after starting the experiment. Water consumption showed some significant effect of irrigation treatments during the growing period of drought stress application, and therefore decreased in DI75, DI50, 1PRD and 2PRD to a level around 75% and 50% of CI. All the DI and PRD treatments resulted in a reduction of total dry mass of 7.29–44.10%, shoot biomass of 24.97–47.72% compared to CI, but an increase in the root–shoot ratio of 12.50–35.42% compared to the control and with significant differences between 2PRD, 1PRD, DI50 and CI. The yield of 1PRD was significantly reduced by 23.98% compared to CI (19,566 kg hm⁻²) over a period of 109 days after transplanting. However, the 1PRD treatment had 17.21% and 24.54% additional yield over the DI50 and 2PRD treatments and had 52.05% higher irrigation water use efficiency (IWUE) than CI treatment. At harvest, although there was a significant difference recorded as single fruit weight and single fruit volume were reduced under the DI and PRD treatments, total soluble solids concentration of fruit harvested under the water-deficit treatments were higher compared to CI. Stomatal conductance measured in fresh leaf was the lowest under 1PRD treatment relative to CI and other treatments. The low stomatal conductance of fresh-leaf issue observed in the work supported the root signaling mechanism reported earlier in plants having undergone partial root drying cycles.     

Effects of oxygen-enriched nutrient solution on greenhouse cucumber and pepper production

A series of experiments were conducted with greenhouse cucumber and pepper plants to determine the effects of oxygen enrichment of the irrigation water on yield and fruit shelf-life. The experiments were carried out in soilless culture in research greenhouses. Depending on the experiment, treatments included sub-ambient (2 mg L⁻¹), ambient (5–6 mg L⁻¹), medium (16 mg L⁻¹) and high (30–40 mg L⁻¹) levels of oxygen in the supply tank. Cucumber plants were grown in yellow cedar sawdust and pepper plants in either sawdust or perlite. Oxygen enrichment resulted in a promotion of cucumber yield in only one experiment; in two other experiments, none of the oxygen treatments, including those at sub-ambient levels, had an effect. There were no effects of oxygen enrichment on pepper yield. However, in both cucumber and pepper, fruit shelf-life was extended in oxygen-enriched treatments. In terms of system efficacy, oxygen levels in the irrigation water were measured at the dripper and found to decrease by 20–67% of initial values compared to the supply tank values, depending on the initial oxygen concentration and on the experiment. Oxygen concentrations decreased even further to virtually ambient levels when measured in the drain water or in the substrate reservoir. Cucumber plant growth was promoted under conditions which facilitated consistently high oxygen in the root zone, achieved through heavy irrigation (1 min in two) with oxygen-enriched nutrient solution of plants grown in saturated substrate (pumice). However, those extreme irrigation rates would not be practical for commercial cucumber or pepper production. Overall, this study demonstrates that oxygen enrichment of porous substrates under typical hydroponic conditions is difficult and possibly because of this, effects on yield are infrequent. However, fruit shelf-life may be improved.     

Energy partitioning and evapotranspiration of hot pepper grown in greenhouse with furrow and drip irrigation methods

Studying crop energy partitioning and evapotranspiration for different irrigation methods is important in optimizing efficient water-saving irrigation, developing suitable irrigation scheduling and improving crop water use efficiency. Two experiments were conducted to compare the energy partitioning and evapotranspiration of hot pepper (Capsicum annum L.) between furrow and drip irrigation methods under two adjacent solar greenhouses in northwest China. Results indicate that irrigation method affected the energy partitioning and evapotranspiration of hot pepper plants and these results were corroborated in a greenhouse study. Compared to drip irrigation, furrow irrigation increased daytime average net radiation (R_n), latent (λET) and sensible (H) heat fluxes by 12–29, 37–53 and 9–23%, respectively, but decreased soil heat flux (G) by 7–19%. Furrow irrigation also resulted in higher λET/R_n and lower H/R_n and G/R_n and increased total evapotranspiration by 55.5% and produced a higher crop coefficient. Total evapotranspiration was 562.3 and 361.6 mm over whole growth stage for furrow and drip irrigation methods, respectively. And drip irrigation increased the total yield and water use efficiency by 18.2 and 80.4%, respectively, before late fruit bearing and harvesting stage. In conclusion, drip irrigation is an effective and water-saving irrigation method in hot pepper production to be used in greenhouse.     

Water relations,growth, yield,and fruit quality of hot pepper under deficit irrigation and partial rootzone drying

We compared two water-saving irrigation practices, deficit irrigation (DI) and partial rootzone drying (PRD), for their effects on growth and quality of ‘Ancho St. Luis’ hot pepper (Capsicum annum L.). The treatments were: commercial irrigation (CI) considered as the control, irrigating both sides of the rootzone with half of the volume of CI considered as DI, and alternating irrigation between two sides of the rootzone with half the volume of CI at each irrigation time considered as PRD. Midday leaf water potentials of PRD and DI plants were lower by 0.15 and 0.30 MPa, respectively, than of CI plants from 130 days after sowing. Total fresh mass of fruit was reduced by 19 and 34.7% in PRD and DI, respectively, compared to CI. Fruit number per plant was reduced by more than 20% in PRD and DI compared to CI. Total dry mass of fruit was similar among the treatments. At harvest, DI fruit had 21% higher total soluble solids concentration and better colour development than other treatments. Although incidence of blossom-end rot was high in PRD and DI fruit, more than 80% of fruit from PRD was not affected. DI and PRD saved 170 and 164 l of water, respectively, compared to CI and they could be feasible irrigation strategies for hot pepper production where the benefit from saving water outweighs the decrease in total fresh mass of fruit.     

Partial rootzone drying maintains fruit quality of ‘Golden Delicious’ apples at harvest and postharvest

Partial rootzone drying (PRD) has been evaluated at harvest, but its effects on apple fruit postharvest life is little known for apples grown in semi-arid regions. The objective of this study was to test the hypothesis that water savings via PRD may affect fruit quality at harvest and postharvest-life of ‘Golden Delicious’ apples grown in a semi-arid region. The experiment was conducted from 2005 to 2007. The irrigation treatments were commercial irrigation as control (CI) and PRD. After 3 years of evaluation, fruit quality at harvest, measured as fruit weight, flesh firmness, and total soluble solids concentration, was similar between CI fruit and PRD fruit. Dry matter concentration (DMC) was higher in PRD fruit than in CI fruit in 2005. The fruit quality after 18 days storage at room temperature (13–18 °C and 51–56% relative humidity) was similar between CI fruit and PRD fruit. The DMC was the highest in PRD fruit in the 2005 and 2007 growing seasons, and tended to be higher in PRD fruit than in CI fruit in 2006. Total soluble solids concentration was ≈8.7% higher in PRD fruit than in CI fruit in 2007. Fruit weight loss was similar between treatments. This study suggests that water deficit via PRD did not damage fruit quality at harvest or after storage at room temperature. Additionally, PRD irrigation saved about 3240 m³ of water per hectare. Therefore, PRD can be recommended for commercial use in semi-arid regions and to those growers interested in either long-term storage or distant markets.     

Effectiveness of water pillow irrigation method on yield and water use efficiency on hot pepper (Capsicum annuum L.)

A study was conducted to elucidate the effect of water pillow (WP) irrigation method, a new alternative method to furrow irrigation, on the yield and water use efficiency (WUE) of hot pepper in a semi-arid climatic condition. In this research, treatments used were: (i) WP method and its 7-day irrigation interval (WP₇), (ii) WP method and its 9-day irrigation interval (WP₉), (iii) WP method and its 11-day irrigation interval (WP₁₁) and (iv) furrow irrigation (FI) method and its 5-day irrigation interval (control) were employed. Although the plants were grown under different irrigation methods and interval conditions, there were no statistical differences in yield and biomass of hot pepper plants between FI and WP treatments (P < 0.05). Water use efficiency (WUE) and irrigation water use efficiency (IWUE) values significantly increased with the application of WP irrigation method (P < 0.05). The highest WUE and IWUE values obtained from WP₁₁ treatment in both years. As a result, we conclude that WP method is a way to save water and increase the yield in semi-arid areas where climatic conditions require repeated irrigation in the hot pepper production area.     

Root zone soil nitrogen management to maintain high tomato yields and minimum nitrogen losses to the environment

Greenhouse field experiments on tomato were carried out at Shouguang, Shandong province, over four double cropping seasons between 2004 and 2008 in order to understand the effects of manipulating root zone N management (RN) on fruit yields, N savings and N losses under conventional furrow irrigation. About 72% of the chemical N fertilizer used in conventional treatment (CN) inputs could be saved using the RN treatment without loss of yield. The cumulative fruit yields were significantly higher in the RN treatment than in the CN treatment. Average seasonal N from irrigation water (118 kg N ha⁻¹), about 59% of shoot N uptake, was the main nitrogen source in treatments with organic manure application (MN) and without organic manure or nitrogen fertilizer (NN). N losses in the RN treatment were lowered by 54% compared with the CN treatment. Lower N losses were found in the MN and NN treatments due to excessive inputs of organic manure and fruit yields were consequently substantially affected in the NN treatment. The critical threshold of N_min supply level in the root zone (0–30 cm) should be around 150 kg N ha⁻¹ for sustainable production. April to May in the winter–spring season and September to October in the autumn–winter season are the critical periods for root zone N manipulation during crop growth. However, control of organic manure inputs is another key factor to further reduce surplus N in the future.     

Fruit yield and water use efficiency of eggplant (Solanum melongema L.) as influenced by different quantities of nitrogen and water applied through drip and furrow irrigation

Elucidation of the effects of different quantities of nitrogen (N) and water applied through drip and furrow irrigation on fruit yield and water use efficiency (WUE) in eggplant is essential for formulating proper management practices for sustainable production. The present investigation was undertaken to evaluate the independent and interactive effects of four levels of N and different quantities of water applied through drip as well as furrow irrigation on eggplant fruit yield, agronomic efficiency of N and WUE. In the present field investigation, ridge planting with each furrow and alternate furrow irrigation were compared with drip irrigation at three levels of water: 100%, 75% and 50% of each furrow irrigation (designated as D_1.0, D_0.75 and D_0.5). The four levels of N studied were 90, 120, 150 and 180 kg N ha⁻¹ (designated as N₉₀, N₁₂₀, N₁₅₀ and N₁₈₀). The eggplant hybrid BH-1 was transplanted on August 5, 2004 at the spacing of 60 cm × 45 cm.     

A comparative study of young ‘Thompson Seedless’ grapevines (Vitis vinifera L.) under drip and furrow irrigation. II. Growth, water use efficiency and nitrogen partitioning

The response of 3-year-old grapevines (Vitis vinifera L. cultivar ‘Thompson Seedless’) to furrow and drip irrigation was quantified in terms of water status, growth, and water use efficiency (WUE). Drip irrigation was applied daily according to best estimates of vineyard evapotranspiration while furrow irrigations were applied when 50% of the plant available soilwater content had been depleted. Drip and furrow irrigated vines showed similar water status (midday leaf water potential, Ψ₁) and shoot growth patterns throughout the season. Dry weight partitioning was not significantly different between treatments but root mass was somewhat larger for the furrow than drip irrigated vines. Nitrogen concentrations of the fruit and roots were significantly (P < 0.05) less for the drip irrigated vines when compared with the furrow treatment. Similar WUE (kg water kg⁻¹ fresh fruit wt.) were obtained for both treatments indicating that furrow irrigation was as efficient as drip irrigation under the conditions of this study. The data indicate that drip irrigation may increase the potential for control of vine growth by making vines more dependent on irrigation and N fertilization than furrow irrigation.     

Combining cover cropping with deficit irrigation in a Mediterranean low vigor vineyard

The aim of this research was to test the effects of vineyard soil management practices combined with deficit irrigation strategies on the performance of the grapevine (Vitisvinifera L.) red variety Tempranillo. Two soil management practices (soil tillage – ST and permanent resident vegetation – RV) were combined with three deficit irrigation treatments (regulated deficit irrigation – RDI, partial rootzone drying – PRD and conventional sustained deficit irrigation – DI) during two growing cycles. Compared to ST, RV reduced soil water content during spring, inducing a significant reduction in vine vegetative growth, yield and must titratable acidity. The effects of irrigation treatments were not much pronounced. Only in the second season RDI showed a significant reduction on vine vegetative growth, yield and must titratable acidity as compared to PRD and DI whose results were similar to one another.     

Water relations of pistachio (Pistacia vera L.) as affected by phenological stages and water regimes

Pistachio is a drought tolerant fruit tree that can be cultivated in rainfed and irrigated conditions. The water requirements of the tree, however, are considerable so in most of the commercial orchards deficit irrigation is a common practice. Regulated deficit irrigation in pistachio trees has been described in several works, which reported that the phenological stage of shell hardening, so called stage II, is the most drought tolerant. This paper proposes that such drought resistance is related to changes in water relations linked to the phenological stages, even in conditions of no water stress. In order to evaluate such changes, the daily pattern of stem water potential and gas exchange (net photosynthesis, P_n, and leaf conductance, g_s) was measured, determining also the pressure–volume curves, in three different phenological stages of mature pistachio trees (Pistacia vera cv Kerman on P. terebinthus L. rootstock.). The daily pattern of stem water potential and gas exchange were performed in three different irrigation treatments: control, regulated deficit irrigation and rainfed. The pressure–volume curves were made only in the control and rainfed treatments. Significant differences were found in the daily pattern of stem water potential in all the phenological stages considered, while only in the last one the net photosynthesis was affected by water stress. The daily pattern of gas exchange at the beginning of the season was not affected by the evaporative demand, with a constant value when radiation was not limiting. Moderate levels of water stress during the last measurement date reduced the maximum values of g_s and P_n resulting also in a clear change in the pattern of the daily curve, with maximum values only at the beginning of the day. The relationships between stem water potential and gas exchange parameters were different during stage II and almost the same in stages I and III. The parameters drawn from the pressure–volume curves also indicated a change in the elastic modulus of the leaf cells in stage II. In addition, differences in the osmotic adjustment (OA) index suggested different degree of osmotic adjustment of the phenological stages in the response to water stress. The results showed that different mechanisms of drought resistance are operating in the different phenological stages in pistachio trees.     

Comparative effects of regulated deficit irrigation (RDI) and partial root-zone drying (PRD) on growth and cell wall peroxidase activity in tomato fruits

The effects of regulated deficit irrigation (RDI) and partial root-zone drying (PRD) on tomato fruit growth and cell wall peroxidase activity in tomato exocarp were investigated in growth chamber conditions. The RDI treatment was 50% of water given to fully irrigated (FI) plants and the PRD treatment was 50% of water of FI plants applied to one half of the root system while the other half dried down, with irrigation shifted when soil water content of the dry side decreased 15–20%. RDI significantly reduced fruit diameter, though PRD reduced fresh weight while having no significant effect on fruit diameter. The activity of peroxidase was significantly higher in RDI and PRD treated plants compared to those of FI. Differences between RDI and PRD were expressed on temporal basis. In the fruits of RDI treated plants peroxidase activity began to increase in the phase when fruit growth started to decline with the peak of enzyme activity of 6.1 HRPEU g⁻¹ FW reached in the phase of mature green fruits when fruit growth rate was minimal. Increase of peroxidase activity in PRD fruits coincided with the ripening phase and the peak of enzyme activity (5.3 HRPEU g⁻¹ FW) was measured at the end of fruit ripening. These data potentially identified contrasting and different roles of tomato exocarp cell wall peroxidase in RDI and PRD treated plants. In RDI treated plants peroxidase may have a role in restricting fruit growth rate, although the increase in enzyme activity during ripening of PRD treated fruit pointed out that peroxidase may also control fruit maturation by inducing more rapid process.     

Evaluating variability of root size system and its constitutive traits in hot pepper (Capsicum annum L.) under water stress

The importance of root size system has long been recognized as crucial to cope with drought conditions. This investigation was conducted to: (i) evaluate the variability in root size system of hot pepper at maturity; (ii) estimate the effect of root size system on yield under drought conditions; and (iii) effect of water stress on xylem vessel development and total xylem cross-sectional area in roots of hot pepper cultivars. Twelve diverse hot pepper cultivars were grown in wooden boxes with two different water treatments, normal and in 50% water application as water deficit condition. Mean primary root length (PRL) showed a significant positive correlation with final fruit yield at normal as well as stressed condition. Total dry mass of fruit was reduced by 34.7% in drought treatments (DI) compared to full watered treatment (FI). At harvest, water-stressed plants had 21% lower root dry weight mass but higher root:shoot ratio other than FI. PRL, lateral root density, total xylem area per root cross-section showed a significant positive relationship with fruit yield. Also, lateral root density was higher in cultivars with higher xylem density, particularly in tolerant cultivars. Lateral root density (r = 0.847, P < 0.001) and total xylem cross-sectional area in root (r = 0.926, P < 0.001) were tightly related with total biomass production. The importance of root traits contributing to withstand drought in hot pepper is discussed.     

Fruit thinning in ‘Conference’ pear grown under deficit irrigation: Implications for fruit quality at harvest and after cold storage

Fruit thinning in pear is feasible for mitigation of water stress effects. However, it is not well known how fruit quality at harvest and after cold storage is affected by pre-harvest water stress. Even less is known about the effects of fruit thinning on quality under these circumstances. To elucidate these, we applied deficit irrigation (DI) and fruit thinning treatments to ‘Conference’ pear over the growing seasons of 2008 and 2009. At the onset of Stage II (80 and 67 days before harvest in 2008 and 2009, respectively), two irrigation treatments were applied: full irrigation (FI) and DI. FI trees received 100% of crop evapotranspiration (ETc). DI trees received no irrigation during the first three weeks of Stage II to induce water stress, but then received 20% of ETc to ensure tree survival. From bud-break until the onset of Stage II and during post-harvest, FI and DI trees received 100% of ETc. Each irrigation treatment received two thinning levels: no thinning leaving commercial crop load (∼180 fruits tree⁻¹), and hand-thinning at the onset of Stage II leaving a light crop load (∼85 fruits tree⁻¹). Under commercial crop loads, DI trees were moderately water-stressed and this had some positive effects on fruit quality. DI increased fruit firmness (FF), soluble solids concentrations (SSC) and acidity at harvest while no changes were observed in fruit maturity (based on ethylene production). Differences in FF and acidity at harvest between FI and DI fruit were maintained during cold storage. DI also reduced fruit weight loss during storage. But fruit size was reduced under DI. Fruit thinning under DI resulted in better fruit composition with no detrimental effect on fresh-market yield compared to un-thinned fruit. Fruit size at harvest and SSC values after five months of cold storage were higher in fruit from thinned trees than fruit from un-thinned trees. Fruit thinning increased fruit ethylene production, indicating advanced maturity. This may lead to earlier harvest which is desirable in years with impending drought. Fruit thinning is therefore a useful technique to enhance pear marketability under water shortage.     

Effects of deficit irrigation on biomass,yield, water productivity and fruit quality of processing tomato under semi-arid Mediterranean climate conditions

Processing tomato is a high water demanding crop, thus requiring irrigation throughout growing season in arid and semiarid areas. The application of deficit irrigation (DI) strategies to this crop may greatly contribute to save irrigation water. A two-year study was carried out in order to assess the effects of DI upon water productivity, final biomass, fruit yield and some quality traits of open-field processing tomato cv. Brigade in a typical semi-arid Mediterranean environment of South Italy. Four irrigation treatments were studied: no irrigation following plant establishment (V0); 100% (V100) or 50% (V50) evapotranspiration (ETc) restoration up to fruit maturity, 100% ETc restoration up to flowering, then 50% ETc restoration (V100-50). Total dry biomass accumulation was significantly depressed by early soil water deficit in V0; irrigation at a reduced rate (50% ETc) from initial stages (V50) or from flowering onwards (V100-50) did not induce any losses in final dry biomass. The marketable yield did not significantly differ among plots irrigated, but an averaged irrigation water saving of 30.4% in V100-50 and 46.2% in V50 was allowed as compared to V100. Marketable yield was negatively affected by the early water shortage in V0, due to the high fruit losses (>44%). The effects of DI on fruit quality were generally the converse of those on fruit yield. DI improved total soluble solids content, titratable acidity and vitamin C content. Water use efficiency was positively affected by DI, suggesting that the crop does not benefits from the water when this last is supplied to fulfil total crop requirements for the whole season. Yield response factor, which indicates the level of tolerance of a crop to water stress, was 0.49 for total dry biomass (Kss) and 0.76 for marketable yield (Ky), indicating that in both cases the reduction in crop productivity is proportionally less than the relative ET deficit. In conclusion, the adoption of DI strategies where a 50% reduction of ETc restored is applied for the whole growing season or part of it could be suggested in processing tomato, to save water improving its use efficiency, minimizing fruit losses and maintaining high fruit quality levels. This aspect is quite important in semi-arid environments, where water scarcity is an increasing concern and water costs are continuously rising.     

Water relations and yield of lysimeter-grown strawberries under limited irrigation

The effects of partial root-zone drying (PRD), as compared to deficit irrigation (DI) and full irrigation (FI), on strawberry (cv. Honeoye) berry yield, yield components and irrigation water use efficiency (WUE_I) were investigated in a field lysimeter under an automatic rain-out shelter. The irrigation treatments were imposed from the beginning of flowering to the end of fruit maturity. In FI the whole root zone was irrigated every second day to field capacity viz. volumetric soil water content (θ) of 20%; while in DI and PRD 60% water of FI was irrigated to either the whole or one-half of the root system, respectively, at each irrigation event. In PRD, irrigation was shifted from one side to the other side of the plants when θ of the drying side had decreased to 8–11%. Compared to FI plants, leaf water potential was significantly lower in DI and PRD plants in 3 out of 10 measurement occasions, while stomatal conductance was similar among the three treatments. Leaf area, fresh berry yield (FY), individual berry fresh weight, berry water content, and berry dry weight (DW) were significantly lower in DI and PRD plants than those of FI plants; whereas the total number of berry per plant was similar among treatments. Compared with FI, the DI and PRD treatments saved 40% of irrigation water, and this led to a 28 and 50% increase of WUE_I based on berry FY and DW, respectively, for both DI and PRD. Conclusively, under the conditions of this study PRD had no advantage compared to DI in terms of berry yield and WUE_I. DI and PRD similarly decreased berry yield and yield components and thus cannot be recommended under similar conditions.     

Responses of pepper to deficit irrigation for paprika production

Pepper (Capsicum annuum L.) production is normally carried out under irrigation as the crop is very susceptible to water shortage. Deficit irrigation strategies in pepper for paprika could increase production and facilitate mechanical harvest and, at the same time, save water. We conducted a field experiment that imposed water deficits, either during ripening (T1) or throughout the season (T2), and compared them to a fully irrigated control (T3). Stem water potential varied from −0.6 MPa in T3, early in the season to −1.5 MPa in T2 prior to harvest. Applied irrigation water for T1, T2, and T3 was 456, 346 and 480 mm, respectively. Water deficits depress leaf area and biomass production but did not affect the proportion of flowers that set fruit. Dry fruit weight in T2 at harvest was 66% of T3, but did not differ significantly between T1 and T3. However, commercial yield (based on colour production) was significantly higher in T3 than in the other two treatments, as the late water deficits imposed in T1 delayed harvest. We concluded that water deficits, either sustained or applied at fruit ripening, required for mechanical harvest do not hasten ripening and are detrimental to commercial yields and that pepper plants should be well supplied with water until harvest for maximum paprika production.     

吐鲁番市日光温室蔬菜不同种植模式水分利用效率调查

为明确吐鲁番市设施蔬菜水分高效利用的合理灌溉方式，调查了沟灌和滴灌对吐鲁番市日光温室早春茬哈密瓜、黄瓜、辣椒和番茄产量、效益和水分利用效率的影响。结果表明：在吐鲁番市，滴灌哈密瓜每667 m² 产量比沟灌高100 kg，每667 m²纯收入多1 017.6 元；滴灌黄瓜、辣椒和番茄每667 m²产量和经济效益均稍低于沟灌；但滴灌哈密瓜、黄瓜、辣椒和番茄的水分利用效率和水分经济利用效率比沟灌高1～3 倍。综合考虑，滴灌是吐鲁番市日光温室蔬菜生产中应重点推广的灌溉方式。     

Interaction of Crop Load and Irrigation on Yield,Fruit Size,Color and Stem-end Splitting Ratio of Apple c.v. ‘Gala,Galaxy’

In this study, the interaction between crop load and irrigation level on yield, fruit size, skin color and stem-end splitting fruit ratio in the apple cultivar ‘Gala, Galaxy’ grafted on rootstock M9 were investigated. Six irrigation programs were applied during the whole growth season: deficit irrigation (rates of 0.25 kc, 0.50 kc, 0.75 kc), full irrigation (rate of 1.00 kc), excess irrigation (rate of 1.25 kc) and non-irrigation (rates of 0.00 kc of “Class A” pan evaporation coefficient). Four crop loads in each irrigation application were performed by hand thinning after the June drop as a- a low crop load (3 fruits cm^?2 TCA), b- a medium crop load (5 fruits cm^?2 TCA), c- a heavy crop load (7 fruits cm^?2 TCA), and d- an un-thinned crop load (>?7 fruits cm^?2 TCA). The total tree yield increased with crop load and irrigation levels. Fruit size was significantly increased by the low crop load. Irrigation increased the fruit size compared to non-irrigation treatment. Further 0.75 kc, 1.00 kc and 1.25 kc irrigation treatments significantly increased the fruit length. Irrigation reduced the fruit flesh firmness. While the low crop load increased the skin red color, it decreased the fruit skin brightness. The yellowness of skin decreased with increasing in the irrigation amount. Irrigation reduced the skin brightness and yellowness, but it increased red color. Crop load and irrigation significantly affected the stem-end splitting fruit ratio. While the splitting fruit ratio increased with a decrease in the crop load, it decreased with an increase in irrigation amount, relatively. Consequently, the low and medium crop load treatments would be beneficial to increase the ratio of marketable fruits without any significant losses in yield for ‘Gala’ apple, especially under 0.75 kc deficit irrigation treatment.     

Yield,blossom-end rot incidence,and fruit quality in pepper plants under moderate salinity are affected by K and Ca fertilization

One of the most important factors limiting agricultural expansion and production is the restricted supply of good quality water. The present study examines the effects of K⁺ and Ca²⁺ fertilization on sweet pepper production, blossom-end rot (BER) incidence and fruit quality of pepper plants (Capsicum annuum L.) grown under moderate saline conditions. Pepper plants were grown in a controlled-environment greenhouse under hydroponic conditions with different nutrient solutions obtained by modifying the Hoagland solution. The experiment consisted on four K⁺ treatments (0.2, 2, 7 and 14 mM) +30 mM NaCl, and four Ca²⁺ treatments (0.2, 2, 4 and 8 mM) +30 mM NaCl, having in common a control without salt with 7 mM K⁺/4 mM Ca²⁺. Salinity decreased total fruit yield and marketable fruit yield by 23% and 37%, respectively. The marketable fruit yield reduction by salt treatment was mainly due to the increase in the number of fruit affected by BER. This typical physiopathy of the pepper fruits occurred between 18 and 25 days after anthesis (DAA), when the highest fruit growth rate was reached. Fruit quality parameters were also affected by salt treatment where the fruit pulp thickness and firmness were decreased, and fructose, glucose and myo-inositol fruit concentrations increased with salinity relative to fruits from control treatment. Under saline conditions an increased supply of K⁺ reduced the fruit fresh weight, the percentage of BER and the marketable yield although promoted the vegetative growth. However, increasing Ca²⁺ concentration in the nutrient solution increased the fruit production, and the marketable yield as consequence of decreasing the percentage of fruit affected with BER. Fruit quality parameters also were affected by the K⁺ and Ca²⁺ treatments.