Study on the Soil Moisture Stress Level in Regulated Deficit Irrigation Experiment

On the basis of discussing the influencing mode of plant moisture stress on plant physiological process and the division of soil moisture availability range, the water suction values partitioning soil moisture were put forward, and then the corresponding water moistures under water stress were obtained by conversing together with characteristic curve of water moisture.

Effects of Regulated Deficit Irrigation on Twig Water Potential of Korla Fragrant Pear

With 7-year-old Korla fragrant pear trees as the experimental material, different root-zone irrigation patterns were arranged to study the effects of soil moisture on twig water potential of Korla fragrant pear trees at different growth stages. The results showed that under the condition of regulated deficit irrigation, the diurnal dynamics of twig water potential of Korla fragrant pear trees was V shaped at different growth stages, and the twig water potential of Korla fragrant pear trees reached the minimum during 14：00-16：00. At different growth stages, the twig water potential of Korla fragrant pear trees under drought stress was significantly lower than that of pear trees irrigated normally. Under both drought stress and normal irrigation, the diurnal variation of twig water potential of Korla fragrant pear trees during the flowering period was most gentle, that during the fruit-setting and mature periods showed some ups and downs, and that during the fruit enlargement period was greater. Under the experimental conditions, the twig water potential of Korla fragrant pear trees was positively correlated with soil moisture content, and the functional relationships between them at different growth stages were studied by regression analysis. In addition, the limits of twig water potential and soil moisture content for normal growth of Korla fragrant pear trees at different growth stages were determined.

Effects of regulated deficit irrigation on soil salinity,physiological processes and fruit quality of gray jujube under desert conditions

Regulated deficit irrigation(RDI)was applied to gray jujube trees in an oasis region,to determine the effects of this irrigation system on soil salinity,gray jujube physiological processes,fruit yield,and fruit quality.Treatments consisted of severe,moderate and low deficit irrigation(irrigated with 85%,70%and 55%of CK,respectively)at the flowering stage to fruit set stage.During the other growth stages,all treatments were irrigated with 80%of pan evaporation,which was the same as that in control.The results indicated that soil salinity was enhanced during the periods of water stress,but the high value of soil salinity declined by 3.48%-37.27%,at each depth,after irrigation was resumed.RDI caused a decline in the photosynthetic rate,transpiration rate,and stomatal conductance,but enhanced the water use efficiency of the leaves.However,the leaf photosynthetic rate was effectively enhanced after the recovery of irrigation,especially in the moderate deficit irrigation treatment,which exceeded the control.This led to an improved fruit yield,which was 9.57%higher than that of the control.The deficit treatments caused a significant increase in the soluble solid content,soluble sugar content,single fruit weight and sugar/acid ratio.Enhanced vitamin C content,resulting from deficit treatments,has also been observed in the gray jujube.Therefore,this research shows that RDI provides some benefits in the production of gray jujube trees in desert conditions.

Effects of regulated deficit irrigation on the growth and berry composition of Cabernet Sauvignon in Ningxia

The adoption of water-saving irrigation strategies is required particularly for wine grape variety,which has been widely cultivated in arid and semiarid areas.To assess vine response to regulated deficit irrigation(RDI),the grape growth and berry composition under five treatments that irrigated at a certain percentage of the crop evapotranspiration(ET c)were evaluated over a 3-year period in a vineyard with the grape variety of Cabernet Sauvignon.The results indicated that RDI had a significant effect on the grape berry size and yield.The largest berry size(12.20 mm)was obtained under the T50 in 2014,while the smallest berry size(9.83 mm)one was obtained under the CK treatments in the same season.The highest individual yield occurred in the T50 treatment,with an average of 1.99 kg,followed by the T25-50 treatment.However,both weights were significantly larger than that of the CK treatment.Compared with the T50 treatments,the individual grape vine yield in the T50-25 treatments were slightly less by 16.9%for 2013,15.3%for 2014 and 18.1%for 2015.Compared to control(CK)treatment,the soluble solid and reducing sugar contents decreased,the total acid content increased,and the sugar/acid ratio basically showed a downward trend.The treatment irrigated at 50%ET c until veraison and 25%thereafter(T50-25)increased the phenolic compound content in grape skins.The treatment received only rain water during the grape growing season(CK)and the one irrigated at 25%of the ET_(c) crop evapotranspiration(T25)caused defoliation and negatively affected the yields and grape composition during all 3 years.Therefore,the RDI not only inhibited the vine vegetative growth but also improved the fruit quality.In terms of productivity and grape composition,the Cabernet Sauvignon grape variety was most sensitive to water stress post-veraison.Over the comprehensive consideration of yield,water-use efficiency and berry composition,the T50-25 treatment was the most efficient irrigation strategy in this area.

YIELD AND FRUIT QUALITY OF ALMOND,PEACH AND PLUM UNDER REGULATED DEFICIT IRRIGATION

The effects of regulated deficit irrigation(RDI)on the performance of almond cv.Tuono,peach cv.JH-Hall and plum cv.Stanley were assessed on the Saiss Plain(NW,Morocco)over three consecutive growing seasons(2011–2013).Irrigation treatments consisted of a control,irrigation applied to fully satisfy crop water requirements(100%ETC),and two RDI treatments,irrigation applied to 75%ETC(RDI-75)and 50%ETC(RDI-50).These three treatments were applied during fruitgrowth slowdown periods corresponding to Stages II and III in almond and Stage II in peach and plum.Yield and fruit quality traits were determined.The effect of RDI differed between species.Yield and fruit size were reduced significantly only in peach under RDI-50.Fruit quality improved in this species in the first year of the experiment,with an increase of sugar/acid ratio and polyphenol content.Plum quality also improved but the effects were significant only in the second and third years.Similar results were recorded in almond kernel,but their epidermal grooves were deeper under RDI-50,and this may have affected their commercial value.It is concluded that water can be saved during the fruitgrowth slowdown period by up to 25%in peach and 50%in almond and plum with improvements in fruit quality without affecting total yield.

Regulated deficit irrigation:an effective way to solve the shortage of agricultural water for horticulture

The deficient agricultural water caused by water shortage is a crucial limiting factor of horticultural production.Among many agricultural water-saving technologies,regulated deficit irrigation(RDI)has been proven to be one of the effective technologies to improve water use efficiency and reduce water waste on the premise of maintaining the quality of agricultural products.RDI was first reported more than 40years ago,although it has been applied in some areas,little is known about understanding of the implementation method,scope of application and detailed mechanism of RDI,resulting in the failure to achieve the effect that RDI should have.This review refers to the research on RDI in different crops published in recent years,summarizes the definition,equipment condition,function,theory illumination,plant response and application in different crops of RDI,and looks forward to its prospect.We expect that this review will provide valuable guidance for researchers and producers concerned,and support the promotion of RDI in more horticultural crops.

Deficit Irrigation as a Strategy to Save Water:Physiology and Potential Application to Horticulture

Water is an increasingly scarce resource worldwide and irrigated agriculture remains one of the largest and most inefficient users of this resource. Low water use efficiency （WUE） together with an increased competition for water resources with other sectors （e.g. tourism or industry） are forcing growers to adopt new irrigation and cultivation practices that use water more judiciously. In areas with dry and hot climates, drip irrigation and protected cultivation have improved WUE mainly by reducing runoff and evapotranspiration losses. However, complementary approaches are still needed to increase WUE in irrigated agriculture. Deficit irrigation strategies like regulated deficit irrigation or partial root drying have emerged as potential ways to increase water savings in agriculture by allowing crops to withstand mild water stress with no or only marginal decreases of yield and quality. Grapevine and several fruit tree crops seem to be well adapted to deficit irrigation, but other crops like vegetables tend not to cope so well due to losses in yield and quality. This paper aims at providing an overview of the physiological basis of deficit irrigation strategies and their potential for horticulture by describing the major consequences of their use to vegetative growth, yield and quality of different crops （fruits, vegetables and ornamentals）.

Water use efficiency and yield responses of cotton to field capacity-based deficit irrigation in an extremely arid area of China

The objectives of present investigation were to test the effects on water use efficiency(WUE)and cotton yield of implementing a range of deficit irrigation regimes triggered at specific fractions of root zone soil moisture,field capacity(θfc)and different crop phenological stages.The study was conducted on southern oasis of the Taklamakan desert,China.The cotton crop’s WUE was quantified,as were leaf photosynthesis and yield.From a photosynthetic perspective,deficit irrigation resulted in 16.8%,10.3%and 2.2%increases in leaf WUE underθfc-based regulated deficit irrigation(T1,T2,and T3),compared to the control,respectively.Cotton yield and its components were significantly affected by irrigation depths(p≤0.05).A relatively high seed yield(0.65 kg/m3)and the highest WUE were achieved,under T3(70%θfc at seedling stage,60%θfc at squaring,50%θfc at full-bloom,70%θfc at boll,70%θfc at boll cracking stage),showing it to be the most effective and productive irrigation schedule tested.As the application ofθfc-based deficit irrigation in surface-irrigated cotton fields showed great potential in saving water,maintaining a high WUE,and improving cotton seed yield,a management strategy consisting or irrigation thresholds of 70%θfc in the root zone at the seedling,boll and boll cracking stages,and of 60%θfc at the squaring stage,and 50%θfc at the full-bloom stage,would be recommended for this extremely arid region.

Assessing effects of deficit irrigation techniques on water productivity of tomato for subsurface drip irrigation system

Water resources are subjected to ever-increasing supply constraints due to extensive agricultural water demand for irrigated lands.Therefore,water-saving irrigation strategies need to be explored.The present study was conducted to explore the possibilities of using regulated deficit irrigation(RDI)and partial root zone drying irrigation(PRD)methods as water-saving irrigation techniques for subsurface irrigation.The objective of this study are to assess the effects of RDI and PRD irrigation on the water productivity of vegetable crops(tomato)under SSD systems in arid climatic conditions,and to compare the responses of tomato crops to PRD,RDI,and FI under an SSD system in terms of productivity,crop quality,and the amount of water saved.The field experiment was conducted during the fall 2014-2015 and 2015-2016 seasons in an experimental field located on an educational farm owned by the Faculty of Food and Agriculture Sciences Department,King Saud University,Riyadh,Kingdom of Saudi Arabia.An area of 102.7 m^(2)(13 m×7.9 m)was allocated for the experiment to manage three treatments:RDI,PRD,and full irrigation(FI).The RDI and PRD treatments received 70%of the irrigation water volume of FI.Each was replicated three times.The most important results indicated that the soil water content(SWC)for the RDI and PRD treatments was lower than that of the FI treatments.FI had the highest stomatal conductance values(gs),while PRD had the lowest stomatal conductance values.The photosynthetic rate(A_(n))was lower under RDI and PRD compared to FI.However,there was no significant change in A_(n) between treatments for most readings taken during both time periods,which means that the water saving treatments(PRD and RDI)did not affect the net photosynthesis rate,thereby enhancing irrigation water use efficiency(IWUE)under DI treatments.The water-saving irrigation techniques decreased transpiration rate(T)compared to the FI treatment.The values of the abscisic acid(ABA)contents were higher under PRD and RDI than FI.The marketable yield under the FI treatment yielded the highest values.The fruit quality parameter results showed that the RDI and PRD treatments increased the total soluble solids,vitamin C,and titratable acidity of tomato compared to the FI treatment.Most of the minimum IWUE values were associated with FI.These results indicate the effects of deficit levels on IWUE.