Effects of irrigation strategies and soils on field grown potatoes: Root distribution

Root distribution of field grown potatoes (cv. Folva) was studied in 4.32 m² lysimeters and subjected to full (FI), deficit (DI), and partial root-zone drying (PRD) irrigation strategies. Drip irrigation was applied for all irrigations. Irrigations were run in three different soils: coarse sand, loamy sand, and sandy loam. Irrigation treatments started after tuber bulking and lasted until final harvest with PRD and DI receiving 65% of FI. Potatoes irrigated with water-saving irrigation techniques (PRD and DI) did not show statistically different dry root mass and root length density (RLD, cm root per cm³ soil) compared with root development in fully irrigated (FI) potatoes. Highest RLD existed in the top 30-40 cm of the ridge below which it decreased sharply. The RLD was distributed homogenously along the ridge and furrow but heterogeneously across the ridge and furrow with highest root density in the furrow. Most roots accumulated in the surface layers of coarse sand as compared to the other soil types. In the deep soil profile (30-70 cm) a higher root density was found in loamy sand compared with the sandy loam and coarse sand. Approximately twice the amounts of roots were found below the furrows compared with the corresponding layers below the ridges. The RLD values in the soil profile of the ridges and the furrows followed the Gerwitz and Page model: RLD = α × exp(−β × z). The highest value of surface root density (α) and rate of change in density (β) was found in coarse sand while the lowest values of α and β were found in the sandy loam and loamy sand. The model estimated the effective rooting depth in coarse sand and sandy loam quite well but did slightly overestimate it in the loamy sand. Statistical analysis showed that one α and β value can be used for each soil irrespective of the irrigation treatment. Thus, the effective rooting depths corresponding to root length densities of 0.1 and 0.25 cm cm⁻³ for sandy loam, loamy sand, and coarse sand soils were 99, 141, and 94 cm, and 80, 115, and 78 cm, respectively, calculated from top of the ridge. The findings of this study can be used in practice for efficient use of water and nutrients in the field.     

Effects of irrigation strategies and soils on field-grown potatoes: Gas exchange and xylem [ABA]

Gas exchange was measured in potatoes (cv. Folva) grown in lysimeters (4.32 m²) in coarse sand, loamy sand, and sandy loam and subjected to full (FI), deficit (DI), and partial root-zone drying (PRD) irrigation strategies. PRD and DI as water-saving irrigation treatments received 65% of FI and started after tuber bulking and lasted for six weeks until final harvest. Midday photosynthesis rate (A_n) and stomatal conductance (g_s) of fully irrigated (FI) plants were lowest in coarse sand and mean A_n of diurnal measurements in FI, PRD and DI tended to be lower in this soil as compared with the loamy sand and sandy loam. The results revealed that diurnal values of A_n and g_s in PRD and DI were consistently lower than FI without reaching significant differences in accordance with findings that xylem [ABA] in PRD was significantly higher than FI, and tended to be higher than in DI. Diurnal measurements showed that A_n reached peak values during mid-morning and midday, while g_s were highest during the morning. Intrinsic water use efficiency (A_n/g_s) correlated linearly well with the leaf to air vapor pressure deficit (VPD) and the slope of the line revealed the rate of A_n/g_s increase per each kPa increase in VPD, i.e. approximately 10 μmol mol⁻¹. Transpiration efficiency (A_n/T) of PRD was higher than DI, which shows slightly better efficient water use than DI. The slope of the linear relationship between transpiration efficiency and VPD decreased from −2.03 to −1.04 during the time course of the growing season, indicating the negative effect of leaf ageing on photosynthesis and thus on plant water use efficiency. This fact shows the possibility to save water during last growth stages through applying water-saving irrigations without much effect on transpiration efficiency.     

Soil microbial response, water and nitrogen use by tomato under different irrigation regimes

The objectives of this study were to investigate the effects of full irrigation (FI), deficit irrigation (DI) and partial root-zone drying (PRD) on plant biomass, irrigation water productivity (IWP), nitrogen use efficiency (NUE) of tomato, and soil microbial C/N ratio. The plants were grown in pots with roots split equally between two soil compartments in a climate-controlled glasshouse. During early fruiting stage, plants were exposed to FI, DI, and PRD treatments. In FI, both soil compartments were irrigated daily to a volumetric soil water content of 18%; in PRD, only one soil compartment was irrigated to 18% while the other was allowed to dry to ca. 7-8%, then the irrigation was shifted; in DI, the same amount of water used for the PRD plants was equally split to the two soil compartments. The results showed that, the FI treatment produced significantly higher dry biomasses of leaves, stems, and fresh weight of fruit and water productivity of aboveground dry biomass production than either DI or PRD, however, fruit IWP in DI was 25% higher than that of FI, and harvest index in DI and PRD were 50% and 22% higher than FI, respectively, for the 26% and 23% less water used in the DI and PRD, respectively, than the FI treatment. The DI treatment caused the smallest losses of N and highest N use efficiency by fruit. Both DI and PRD caused a significant increase in the soil microbial C/N ratio, meaning ratio of fungal biomass was high at low soil water contents. The result indicates that more work is needed to link the aboveground N uptake and the underground microbially mediated N transformation under different water-saving irrigation regimes.     

Irrigation, tillage and mulching effects on soybean yield and water productivity in relation to soil texture

Depleting groundwater resources in Indian Punjab call for diversifying from rice to crops with low evapo-transpiration needs and adopting water-saving technologies. Soybean offers a diversification option in coarse- to medium-textured soils. However, its productivity in these soils is constrained by high soil mechanical resistance and high soil temperature during early part of the growing season. These constraints can be alleviated through irrigation, deep tillage and straw mulching. This 3-years field study examines the individual and combined effects of irrigation, deep tillage, and straw mulching regimes on soybean yield and water productivity (WP) in relation to soil texture. Combinations of two irrigation regimes viz., full irrigation (I_f), and partial irrigation (I_p) in the main plot; two tillage regimes viz., conventional-till (CT)-soil stirring to 0.10 m depth, and deep tillage (DT)-chiseling down to 0.35 m depth followed by CT in the subplot; and two mulch rates viz., 0 (M₀) and 6 t ha⁻¹ (M) in the sub-subplot on two soils differing in available water capacity were evaluated.Seed yield was greater in the sandy loam than in the loamy sand reflecting the effects of available water capacity. Irrigation effects were greater on loamy sand (40%) than on sandy loam (5%) soil. Deep tillage benefits were also more on loamy sand (14%) compared to sandy loam (5%) soil. Yield gains with mulching were comparable on the two soils (19%). An evaluation of interaction effects showed that mulching response was slightly more in I_p (20%) than in I_f regimes (17%) in the sandy loam; while in the loamy sand, mulching gains were comparable (18-19%) in both irrigation regimes. Benefits of deep tillage in the loamy sand soil were more in I_p (20%) than in I_f regimes (17%). Deep tillage and straw mulching enhanced WP (ratio of seed yield/water use) from 1.39 to 1.97 kg ha⁻¹ mm⁻¹ in I_p regime, and from 1.87 to 2.33 kg ha⁻¹ mm⁻¹ in I_f regime in the loamy sand soil. These effects on WP were less in the sandy loam soil with greater available water capacity. Yield and WP gains are ascribed to deeper and denser rooting due to moderation of soil temperature and water conservation with straw mulching and tillage-induced reduction in soil mechanical resistance. Root mass in CTM₀, CTM, DTM₀ and DTM was 2.79, 5.88, 5.34 and 5.58 mg cm⁻² at pod-filling in the loamy sand soil. Comparable yield responses to deep tillage or mulching in the loamy sand soil suggest that either of the options, depending on their cost and availability considerations, can be employed for improving soybean yield and water productivity.     

Deficit irrigation based on drought tolerance and root signalling in potatoes and tomatoes

Agriculture is a big consumer of fresh water in competition with other sectors of the society. Within the EU-project SAFIR new water-saving irrigation strategies were developed based on pot, semi-field and field experiments with potatoes (Solanum tuberosum L.), fresh tomatoes (Lycopersicon esculentum Mill.) and processing tomatoes as model plants. From the pot and semi-field experiments an ABA production model was developed for potatoes to optimize the ABA signalling; this was obtained by modelling the optimal level of soil drying for ABA production before re-irrigation in a crop growth model. The field irrigation guidelines were developed under temperate (Denmark), Mediterranean (Greece, Italy) and continental (Serbia, China) climatic conditions during summer. The field investigations on processing tomatoes were undertaken only in the Po valley (North Italy) on fine, textured soil. The investigations from several studies showed that gradual soil drying imposed by deficit irrigation (DI) or partial root zone drying irrigation (PRD) induced hydraulic and chemical signals from the root system resulting in partial stomatal closure, an increase in photosynthetic water use efficiency, and a slight reduction in top vegetative growth. Further PRD increased N-mineralization significantly beyond that from DI, causing a stay-green effect late in the growing season. In field potato and tomato experiments the water-saving irrigation strategies DI and PRD were able to save about 20-30% of the water used in fully irrigated plants. PRD increased marketable yield in potatoes significantly by 15% due to improved tuber size distribution. PRD increased antioxidant content significantly by approximately 10% in both potatoes and fresh tomatoes. Under a high temperature regime, full irrigation (FI) should be undertaken, as was clear from field observations in tomatoes. For tomatoes full irrigation should be undertaken for cooling effects when the night/day average temperature >26.5 °C or when air temperature >40 °C to avoid flower-dropping. The temperature threshold for potatoes is not clear. From three-year field drip irrigation experiments we found that under the establishment phase, both potatoes and tomatoes should be fully irrigated; however, during the later phases deficit irrigation might be applied as outlined below without causing significant yield reduction:

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Potatoes

°

After the end of tuber initiation, DI or PRD is applied at 70% of FI. During the last 14 days of the growth period, DI or PRD is applied at 50% of FI.

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Fresh tomatoes

°

From the moment the 1st truce is developed, DI is applied at 85-80% of FI for two weeks. In the middle period, DI or PRD is applied at 70% of FI. During the last 14 days of the growth period, DI or PRD is applied at 50% of FI.

•

Processing tomatoes

°

From transplanting to fruit setting at 4th-5th cluster, the PRD and DI threshold for re-irrigation is when the plant-available soil water content (ASWC) equals 0.7 (soil water potential, Ψ_soil = −90 kPa). During the late fruit development/ripening stage, 10% of red fruits, the threshold for re-irrigation for DI is when ASWC = 0.5 (Ψ_soil = −185 kPa) and for PRD when ASWC (dry side) = 0.4 (Ψ_{soil, dry side} = −270 kPa).

The findings during the SAFIR project might be used as a framework for implementing water-saving deficit irrigation under different local soil and climatic conditions.     

Comparative effects of partial root-zone drying and deficit irrigation on nitrogen uptake in potatoes (<Emphasis Type="Italic">Solanum tuberosum</Emphasis> L.)

The effects of partial root-zone drying (PRD) as compared with deficit irrigation (DI) and full irrigation (FI) on nitrogen (N) uptake and partitioning in potato (Solanum tuberosum L.) were investigated. Potato plants were grown in split-root pots and were exposed to FI, PRD, and DI treatments at tuber bulking stage. Just before onset of the irrigation treatment, each plant received 0.6 g N (in the form of urea) with 5% of which was ¹⁵N-labeled. After 4 weeks of irrigation treatments (i.e., one drying/wetting cycles completed in the PRD treatment), the plants were harvested and plant dry mass and N content were determined. The results showed that although the plant dry mass was not affected by the irrigation treatments, due to a reduced water use by the plant, both the PRD and DI treatments significantly increased crop water use efficiency. Compared with the FI and DI plants, PRD plants had significantly higher N contents in the leaves, stems and tubers; whereas, the ¹⁵N content in the plant organs was similar for the FI, PRD, and DI plants. It is suggested that not the root N uptake efficiency but the soil N availability was enhanced by the PRD treatment.     

Effect of small irrigation amounts on the yield of wheat

Yields of dryland crops are governed by the moisture in the soil profile at seeding and by rainfall during the growing season. Occasionally limited amounts of water may also be available for irrigation. Field experiments were conducted over a period of 4 years on loamy sand and 3 years on sandy loam to study the effects of pre-seeding, post-seeding and split application of limited amounts of water on root growth, water use, dry matter accumulation and grain yield of wheat. This article reports the treatment effects on dry matter accumulation and grain yield.Early season water stress decreased the rate of dry matter accumulation. Grain yield responded significantly to irrigation 30 days after seeding irrespective of the amount of water, year and soil type. Yield with post-seeding irrigation averaged 3518 kg ha^?1 against 2317 kg ha^?1 for unirrigated control in loamy sand and 4440 kg ha^?1 against 3391 kg ha^?1 in sandy loam. The increase in yield was manifested by a significant increase in the number of effective tillers per m row length, number of grains per ear and thousand grain weight.     

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.     

Analysis of AET and yield predictions under surface and buried drip irrigation systems using the Crop Model PILOTE and Hydrus-2D

Innovative irrigation solutions have to face water scarcity problems affecting the Mediterranean countries. Generally, surface (DI) or subsurface drip irrigation systems (SDI) have the ability to increase water productivity (WP). But the question about their possible utilisation for crops such as corn would merit to be analysed using an appropriate economic tool. The latter would be necessary based on the utilisation of a modelling approach to identify the optimal irrigation strategy associating a water amount with a crop yield (Yc). In this perspective, a possible utilisation of the operative 1D crop model PILOTE for simulating actual evapotranspiration (AET) and yield under a 2D soil water transfer process characterizing DI and SDI was analysed. In this study, limited to a loamy soil cultivated with corn, the pertinence of the root water uptake model used in the numerical code Hydrus-2D for AET estimations of actual evapotranspiration (AET) under water stress conditions is discussed throughout the Yc = F(AET) relationship established by PILOTE on the basis of validated simulations. The conclusions of this work are (i): with slight adaptations, PILOTE can provide reliable WP estimations associated to irrigation strategies under DI and SDI, (ii): the current Hydrus-2D version used in this study underestimates AET, compared with PILOTE, in a range varying from 7% under moderate water stress conditions to 14% under severe ones, (iii): A lateral spacing of 1.6 m for the irrigation of corn with a SDI system is an appropriate solution on a loamy soil under a Mediterranean climate.A local Yc = F(AET) relationship associated with a Hydrus-2D version taking into account the compensating root uptake process could result in an interesting tool to help identify the optimal irrigation system design under different soil conditions.     

Yield response of greenhouse grown tomato to partial root drying and conventional deficit irrigation

Greenhouse grown tomato was used to test partial root drying (PRD), a newly developing irrigation technique to save irrigation water, in Spring- and Fall-planted fresh-market tomato (Lycopersicon esculentum L., cv. Fantastic) cultivar. The PRD practice simply requires wetting of one half of the rooting zone and leaving the other half dry, thereby utilizing reduced amount of irrigation water applied. The wetted and dry sides are interchanged in the subsequent irrigations. Six irrigation treatments were tested during the two-year work in 2000 and 2001: (1) FULL, control treatment where the full amount of irrigation water, which was measured using Class-A pan evaporation data, was applied to the roots on all sides of the plant; (2) 1PRD30, 30% deficit irrigation with PRD in which wetted and dry sides of the root zone were interchanged with every irrigation; (3) 1PRD50; (4) 2PRD50, 50% deficit irrigation with PRD in which wetted and dry sides of the root zone were interchanged every and every other irrigation, respectively; (5) DI30 and (6) DI50, 30 and 50% deficit irrigations, respectively. The defined deficit levels were all in comparison to FULL irrigation. During the first year study in 2000, only three treatments (FULL, 1PRD30 and 2PRD50) were tested. Five treatments with exception of 2PRD50 were included in 2001. The FULL irrigation treatment, in Spring-planted tomato having a 153 day growth period, yielded 110.9 t ha⁻¹. The resulting irrigation-water-use efficiency (IWUE) was 321.8 kg (ha mm)⁻¹. The 1PRD50 treatment gave 86.6 t ha⁻¹, which was not statistically different (P ≤ 0.05) from the FULL irrigation (the control) and had 56% higher IWUE. Although yield differences were not statistically significant in Fall-planted tomato, the highest fruit yield was again obtained under FULL irrigation treatment (205.2 t ha⁻¹) over a growth period of 259 days after transplanting. The PRD treatments had 7–10% additional yield over the deficit irrigation receiving the same amount of water. The PRD treatments gave 10–27% higher marketable tomato yield (>60 g per fruit), compared with the DI treatments. Abscisic acid (ABA) concentrations measured in fresh leaf tissue was the highest under PRD practice relative to FULL and DI treatments. The high ABA content of fresh-leaf tissue observed in the work supports the root signalling mechanism reported earlier in plants having undergone partial root drying cycles.     

Irrigation and tillage effects on root development,water use and yield of wheat on coarse textured soils

Summary Rapid drying of surface layers of coarse-textured soils early in the growth season increases soil strength and restricts root growth. This constraint on root growth may be countered by deep tillage and/or early irrigation. We investigated tillage and irrigation effects on root growth, water use, dry matter and grain yield of wheat on loamy sand and sandy loam soils for three years. Treatments included all combinations of two tillage systems i) conventional tillage (CT) — stirring the soil to 10 cm depth, ii) deep tillage (DT) — subsoiling with a single-tine chisel down to 35–40 cm, 40 cm apart followed by CT; and four irrigation regimes, i) I₀ — no post-seeding irrigation, ii) I₁ — 50 mm irrigation 30 days after seeding (DAS), iii) I₂ — 50 mm irrigation 30 DAS and subsequent irrigations of 75 mm each when net evaporation from USWB class A open pan (PAN-E) since previous irrigation accumulated to 82 mm, and iv) I₃ — same as in I² but irrigation applied when PAN-E accumulated to 62 mm. The crop of wheat (Triticum aestivum L. HD 2329) was fertilized with 20kg P, 10kg K and 5kg Zn ha^–1 at seeding. The rate of nitrogen fertilization was 60 kg ha^–1 in the unirrigated and 120 kg ha^–1 in the irrigated treatments. Tillage decreased soil strength and so did the early post-seeding irrigation. Both deep tillage and early irrigation shortened the time needed for the root system to reach a specified depth. Subsequent wetting through rain/irrigation reduced the rate of root penetration down the profile and also negated deep tillage effects on rooting depth. However, tillage/irrigation increased root length density in the rooted profile even in a wet year. Better rooting resulted in greater profile water depletion, more favourable plant water status and higher dry matter and grain yields. In a dry year, the wheat in the DT plots used 46 mm more water, remained 3.3 °C cooler at grain-fill and yielded 68% more grain than in CT when unirrigated and grown in the loamy sand. Early irrigation also increased profile water depletion, more so in CT than DT. Averaged over three years, grain yield in DT was 12 and 9% higher than in CT on loamy sand and sandy loam, respectively. Benefits of DT decreased with increase in rainfall and irrigation. Irrigation significantly increased grain yield on both soils, but the response was greatly influenced by soil type, tillage system and year. The study shows that soil related constraints on root growth may be alleviated through deep tillage and/or early irrigation.     

Irrigation of sunflower (Helianthus annuus) in relation to tillage and mulching

For sustainable sunflower production in semi-arid sub-tropical regions, it is essential to increase its water use efficiency. Field studies were conducted for three years on deep alluvial loamy sand (Typic Ustipsamment) and sandy loam (Typic Ustochrept) soils at Punjab Agricultural University, Ludhiana, India, to evaluate the interactive effects of three irrigation regimes (irrigation water to net open pan evaporation ratios, I₁, I₂, I₃) on sunflower yield in relation to tillage (conventional tillage, CT, and deep-tillage, DT) and mulching (no mulch, M₀, and residue mulch, M₁).Both deep tillage and mulch significantly increased crop yield irrespective of soil type and year. Increase in mean achene yield across soils during three years with DT over CT varied between 10 and 16% and that with mulch over no mulch by 8 to 17%.Deep tillage and/or mulching helped the crop in efficient utilization of water by increasing leaf area index (LAI) and the depth and density of rooting. Irrigation and tillage interacted for their effects on yield on loamy sand, as the crop responded to higher level of irrigation with CT than with DT. On loamy sand, mean achene yield increased with increase in water supply up to IW/PE = 1.5 in a dry year and upto IW/PE = 1.2 in relatively wetter years. On sandy loam, mean yield response to irrigations was observed upto IW/PE = 1.0 in all the three years.Regression analysis of relative yield against water supply during the three years on both the soils, showed that for 80% relative yield the crop required 105 cm water in CTM₀, 90 cm in CTM or DTM₀ and only 80 cm in DTM. The study suggests that deep tillage or straw mulch may be used to achieve higher water use efficiency in sunflower on coarse textured soils in semi-arid, sub-tropical regions.     

小滴头流量下灌水频率对膜下土壤湿润区的影响

为了探明灌水频率对小滴头滴灌土壤湿润区的影响,在实验室对沙土和中壤土进行了膜下间歇滴灌试验,滴头流量分别为0．3、0．5、0．7L／h;灌水频率分别为1、2、3、4次灌完。在灌水量相同的情况下观测了土壤的湿润区运移过程和含水率分布。结果表明,小滴头流量下改变滴水频率对土壤湿润体的大小影响很小;随着灌水频率的增加,土壤湿...     

滴灌条件下山区典型土壤水分运移规律分析

在广西山区选择沙土、壤土和黏土等3种典型土壤,并开展滴灌在这3种土壤条件下的土壤水分运移规律研究。试验结果表明:1在地埋黏土、壤土和沙土以及0.10 MPa工作压力条件下,滴灌管的单米流量为4.17、5.92和6.10 L/h,为地表自由出流的67.58%、95.05%和98.87%;2滴灌在黏土的水分运移形状基本为圆形,在沙土和壤土的湿润形状为上小下大的椭圆形;3同等条件下,水分在沙土的水平和垂直向下运移速率最大,壤土次之,黏土最小;4在土箱相同位置,黏土的土壤含水率最大,壤土次之,沙土最小;5根据滴灌的土壤水分运移规律,提出滴灌管在广西山区沙土、壤土和黏土的适宜埋深分别为10、15和20 cm;6滴灌应用在山区条播作物时,在黏土、壤土、沙土的适宜滴孔间距应为35、30和25 cm。     

Agronomic response and water productivity of almond trees under contrasted deficit irrigation regimes

We investigated the long-term effects of different deficit irrigation (DI) options on tree growth, shoot and leaf attributes, yield determinants and water productivity of almond trees (Prunus dulcis, cv. Marta) grown in a semiarid climate in SE Spain. Three partial root-zone drying (PRD) irrigation treatments encompassing a wide range of water restriction (30%, 50% and 70% of full crop requirements, ET_c) and a regulated deficit irrigation treatment (RDI, at 50% ET_c during kernel-filling) were compared over three consecutive growth seasons (2004–2006) to full irrigation (FI). The results showed that all deficit irrigation treatments have a negative impact on trunk growth parameters. The magnitude of the reduction in trunk growth rate was strongly correlated through a linear relationship with the annual volume of water applied (WA) per tree. Similarly, a significant relationship was found between WA and the increase in crown volume. In contrast, leaf-related attributes and some yield-related parameters (e.g., kernel fraction) were not significantly affected by the irrigation treatments. Except in PRD₇₀, individual kernel weight was significantly reduced in the deficit irrigated treatments. Kernel yield, expressed in percent of the maximum yield observed in the FI treatment, showed a linear decrease with decreasing WA and a slope of 0.43, which implies that a 1% decrease in water application would lead to a reduction of 0.43% in yield. Water productivity increased drastically with the reduction of water application, reaching 123% in the case of PRD₃₀. Overall, our results demonstrate the prevalence of direct and strong links between the intensity of the water restriction under PRD – i.e., the total water supply during the growing season – and the main parameters related to tree growth, yield and water productivity. Noteworthy, the treatments that received similar annual water volumes under contrasted deficit irrigation strategies (i.e., PRD₇₀ and RDI) presented a similar tree performance.     

Long-term evaluation of yield components of young olive trees during the onset of fruit production under different irrigation regimes

A four-year study was conducted on young Olea europaea L. trees to investigate the effect of deficit irrigation starting from the onset of fruit production. Subsurface drip irrigation was used to supply 100% (FI), 46–52% (DI), or 2–6% (SI) of tree water needs. Tree growth was reduced by deficit irrigation, whereas, return bloom was not. Per tree fruit yield of DI trees was 68% that of FI, but fruit yield efficiency based on tree size was similar between treatments. Fruit set and the number of fruits of FI trees were similar to those of DI trees and significantly higher than in SI trees. No significant differences in fruit fresh weight were found between FI and DI. The oil yield and oil yield efficiency of the DI treatment were 82 and 110% that of FI trees, respectively. A level of about 50% deficit proved sustainable to irrigate trees for oil production.     

滴头流量和灌水量对滴灌土壤水分运动的影响

滴头流量和灌水量对于滴灌系统的设计具有非常重要的实际价值。通过室内试验,对不同土质、不同滴头流量情况下滴灌土壤水分运动进行了室内试验研究。结果表明,砂土条件下,滴灌湿润体呈现越来越"尖"的直立半椭球体,滴头流量的增大会使垂直湿润锋的运移更加显著。轻壤土条件下,滴灌湿润体基本上一直呈现为平卧的半椭球体,逐渐变成半球体。滴头流量的增大会使水平湿润锋的运移更加显著。在灌水量一定的情况下,滴头流量的增加在砂土条件下会加快水分在垂直方向的运移,在轻壤土条件下则会加快水分在水平方向的运移。     

基于ORYZA2000的水量平衡要素和

在对水稻生产模型ORYZA2000充分验证的基础上，以2003年团林水肥耦合试验设计为背景，应用ORYZA2000模拟分析了不同施肥条件下传统淹灌和3种节水灌溉方式下的稻田田间水量平衡要素、产量以及水分生产率。结果表明，节水灌溉方式灌水量大大低于传统淹灌，其中无水层灌溉节水效果又明显优于沟灌，可靠性高，雨养灌溉虽然能最大限度的节约灌溉水量，但其应用取决于区域气候特点，应结合气候预测应用。水分胁迫可以增大不同施氮水平下稻田腾发量的差异，施氮可以减少株间蒸发，增加作物蒸腾，从而增加稻田腾发量和产量。     

滴灌和微润灌条件下桂西北山区典型土壤水分运移规律分析

为了研究滴灌和微润灌在广西山区主要土壤的水分运移规律,在广西山区选择砂土、壤土和黏土等三种典型土壤,在室内建立并开展土壤水分运移规律试验。试验结果表明:1在地埋黏土、壤土和砂土以及0.10 MPa工作压力条件下,微润管的单米流量分别为0.24、0.31和0.43L/h,为地表出流量的67.6%~98.8%,滴灌管的单米流量为4.17、5.92和6.10L/h,为地表出流量的38.1%~68.2%;2在3种土壤中,滴灌和微润灌的水分运移形状初期为圆形,后期为椭圆形,但砂土的湿润范围最大、壤土次之、黏土最小;3在土箱相同位置,黏土的土壤含水率最大,壤土次之,砂土最小;4根据滴灌和微润灌的土壤水分运移规律,提出滴灌管和微润管在砂土、壤土的适宜埋深为20cm,在黏土的适宜埋深为10cm。     

The effects of irrigation methods with effluent and irrigation scheduling on water use efficiency and corn yields in an arid region

A great challenge for the agricultural sector is to produce more food from less water, particularly in arid and semi-arid regions which suffer from water scarcity. A study was conducted to evaluate the effect of three irrigation methods, using effluent versus fresh water, on water savings, yields and irrigation water use efficiency (IWUE). The irrigation scheduling was based on soil moisture and rooting depth monitoring. The experimental design was a split plot with three main treatments, namely subsurface drip (SSD), surface drip (SD) and furrow irrigation (FI) and two sub-treatments effluent and fresh water, which were applied with three replications. The experiment was conducted at the Marvdasht city (Southern Iran) wastewater treatment plant during 2005 and 2006. The experimental results indicated that the average water applied in the irrigation treatments with monitoring was much less than that using the conventional irrigation method (using furrows but based on a constant irrigation interval, without moisture monitoring). The maximum water saving was obtained using SSD with 5907 m³ ha⁻¹ water applied, and the minimum water saving was obtained using FI with 6822 m³ ha⁻¹. The predicted irrigation water requirements using the Penman-Monteith equation (considering 85% irrigation efficiency for the FI method) was 10,743 m³ ha⁻¹. The pressure irrigation systems (SSD and SD) led to a greater yield compared to the surface method (FI). The highest yield (12.11 × 10³ kg ha⁻¹) was obtained with SSD and the lowest was obtained with the FI method (9.75 × 10³ kg ha⁻¹). The irrigation methods indicated a highly significant difference in irrigation water use efficiency. The maximum IWUE was obtained with the SSD (2.12 kg m⁻³) and the minimum was obtained with the FI method (1.43 kg m⁻³). Irrigation with effluent led to a greater IWUE compared to fresh water, but the difference was not statistically significant.