Exploring the impact of high density planting system and deficit irrigation in cotton(Gossypium hirsutum L.):a comprehensive review

Lessons learned from past experiences push for an alternate way of crop production.In India,adopting high density planting system(HDPS)to boost cotton yield is becoming a growing trend.HDPS has recently been considered a replacement for the current Indian production system.It is also suitable for mechanical harvesting,which reducing labour costs,increasing input use efficiency,timely harvesting timely,maintaining cotton quality,and offering the potential to increase productivity and profitability.This technology has become widespread in globally cotton growing regions.Water management is critical for the success of high density cotton planting.Due to the problem of freshwater availability,more crops should be produced per drop of water.In the high-density planting system,optimum water application is essential to control excessive vegetative growth and improve the translocation of photoassimilates to reproductive organs.Deficit irrigation is a tool to save water without compromising yield.At the same time,it consumes less water than the normal evapotranspiration of crops.This review comprehensively documents the importance of growing cotton under a high-density planting system with deficit irrigation.Based on the current research and combined with cotton production reality,this review discusses the application and future development of deficit irrigation,which may provide theoretical guidance for the sustainable advancement of cotton planting systems.

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.

Peach yield and fruit quality is maintained under mild deficit irrigation in semi-arid China

We conducted a two-year study of deficit irrigation impact on peach yield and quality in semi-arid northwest China. Over two years, four-year-old peach trees were irrigated at 100, 75, 50 and 25% of peach evapotranspiration （ETc）, here, ETc= Coefficient （Kc）×Local reference evapotranspiration （ET0）. During the April-July fruit production season we measured root zone soil water depletion, sap flow velocity, net photosynthetic rate （Pn）, transpiration rate （Tr）, stomatal conductance （Gs）, water use efficiency （WUE=Pn/Tr）, fruit quality, and yield under a mobile rain-out shelter. Increased soil water depletion reasonably mirrored decreasing irrigation rates both years, causing progressively greater water stress. Progressive water stress lowered Gs, which in turn translated into lower T as measured by sap flow. However, mild deficit irrigation （75% ETc） constricted T more than Pn. Pn was not different between 100 and 75% ETc treatments in both years, and it decreased only 5-8% in June with higher temperature than that in May with cooler temperature. Concurrently under 75% ETc treatment, was reduced, and WUE was up to 13% higher than that under 100% ETc treatment. While total fruit yield was not different under the two treatments, because 75% ETc treatment had fewer but larger fruit than 100% ETc trees, suggesting mild water stress thinned fruit load. By contrast, sharply decreased T and Pn of the driest treatments （50 and 25% ETo） increased WUE, but less carbon uptake impacted total fruit yield, resulting 13 and 33% lower yield compared to that of 100% ETc treatment. Irrigation rates affected fruit quality, particularly between the 100 and 75% ETc trees. Fewer but larger fruit in the mildly water stressed trees （75% ETc） resulted in more soluble solids and vitamin C, firmer fruit, and improved sugar：acid ratio and fruit color compared to the 100% ETo treatment. Overall, trees deficit irrigated at 75% ETc maintained yield while improving fruit quality and using less water.

Improvement in winter wheat productivity through regulating PSⅡ photochemistry,photosynthesis and chlorophyll fluorescence under deficit irrigation conditions

Deficit irrigation is critical to global food production,particularly in arid and semi-arid regions with low precipitation.Given water shortage has threatened agricultural sustainability under the dry-land farming system in China,there is an urgent need to develop effective water-saving technologies.We carried out a field study under two cultivation techniques:(1) the ridge and furrow cultivation model(R);and(2) the conventional flat farming model(F),and three simulated precipitation levels(1,275 mm;2,200 mm;3,125 mm) with two deficit irrigation levels(150 and 75 mm).We demonstrated that under the ridge furrow(R) model,rainfall harvesting planting under 150 mm deficit irrigation combined with 200 mm simulated precipitation can considerably increase net photosynthesis rate(P_(n)),quantum yield of PSII(ΦPSⅡ),electron transport rate(ETR),performance index of photosynthetic PSII(F_(v)/F_(m)′),and transformation energy potential of PSII(F_(v)/F_(o)).In addition,during the jointing,anthesis and grain-filling stages,the grain and biomass yield in the R model are 18.9 and 11.1% higher than those in the flat cultivation model,respectively,primarily due to improved soil water contents.The winter wheat fluorescence parameters were significantly positively associated with the photosynthesis,biomass and wheat production.The result suggests that the R cultivation model with irrigation of 150 mm and simulated precipitation of 200 mm is an effective planting method for enhancing P_(n),biomass,wheat production,and chlorophyll fluorescence parameters in dry-land farming areas.

Yield Response to Deficit Irrigation and Partial Root-Zone Drying in Processing Tomato （Lycopersicon esculentum Mill,）

Due to the global expansion of irrigated areas and the limited availability of irrigation water, it is necessary to optimize water use in order to maximize crop yields under water deficit conditions. To evaluate the yield response of two processing tomato hybrids （Ercole and Genius） grown under different irrigation treatments, a field trial was conducted during the 2008 growing season in Southern Italy. Three irrigation treatments were used： the restitution of 70% of maximum evapotranspiration （ETc） both under ＂Deficit Irrigation＂ （70DI） and ＂Partial Root-zone Drying＂ （70PRD） strategies; full irrigated （FI： 100% ETc）. The two water deficit irrigation treatments （DI and PRD） showed stomatal conductance values lower than FI treatment and saved a substantial amount of water maintaining reasonable marketable yield. Moreover, PRD strategy showed slightly higher ＂Water Use Efficiency＂ （WUE） values than DI. Finally, ＂yield response factor＂ （Ky） showed always values less than unity, indicating the possibility to adopt, within certain limited condition, both DI and PRD in field-grown processing tomato cultivated in Southern Italy. In conclusion, in our experimental conditions, deficit irrigation practices seem to be acceptable relatively to processing tomato yield aspects and Ky could be promoted as a useful indicator for irrigation in water deficit conditions.

Effect of Sustained Deficit Irrigation on Stem Water Potential of Navel Oranges in Jordan Valley

Research was conducted to find the relationship between deficit irrigation treatments （DIT） and stems water potential. The study was conducted on 14 years old navel orange trees grafted on sour oranges for the growing season 2006/2007 at a private farm in the Northern part of Jordan Valley （latitude： 32° 50′ N, longitude： 32° 50′ E, altitude： -254 m）. Three levels of irrigation treatments （IT） were applied; namely 100%, 75% and 50% of reference evapotranspiration, representing over irrigation （OIT）, full irrigation （FIT）, and deficit irrigation （DIT）, respectively. A drip irrigation using one irrigation source line with drippers spaced 0.5 m having average discharge of 2.3 L/hr at pressure 1.5 bar, was used. Stem water potential （SWP） at 100% over irrigation treatment （OIT） of navel orange trees had less negative value during the irrigation seasons （-1.57 MPa）, whereas the highest negative value （-2.17 MPa） occurred at 50% deficit irrigation treatment （DIT）.

Effect of Deficit Irrigation at Different Growth Stages on Wheat Growth and Yield

In order to evaluate the effect of deficit irrigation at various growth stages on wheat growth and yield, a field experiment was conducted in the 2008-2009 growing season based on the completely randomized block with four replications at the experimental farm of the College of Agriculture, Shiraz University, Shiraz, Iran, located at Badjgah. Treatments involved 13 irrigation regimes which applied in stem elongation, heading and grain filling growth stages. The highest seed yield （4,333 kg-ha-1） and the lowest ones （1,377 kg＇hal） were obtained from T1 （100% field capacity （FC） in all growth stages） and T13 （50% FC in all growth stages）, respectively. With limitation in water amount seed yield was diminished, but this trend was not significant at T4 （100%, 100% and 50% FC） and TI 1 （100%, 100% and 75~/0 FC）. Stepwise regression results revealed that, seed number per spike had the largest contribution （partial R2 = 0.72） in seed yield variation. Also at TI, T4, and TI 1 treatments （well water treatments） as well as TI3 （sever stress） head number m2 contribute most in seed yield determination （partial R2 = 0.96）. It can be concluded that water shortage during the grain filling period and its allocation to the other consecutive crop, can increase crop production in southern regions of Iran.

Positive Impact of Deficit Irrigation on Physiological Response and Fruit Yield in Citrus Orchards： Implications for Sustainable Water Savings

Different strategies of deficit irrigation based on water stress dynamics were applied in an 11-year old citrus trees （Citrus sinensis L. Osb. cv. Navelina） grafted on carrizo citrange （Citrus sinensis L. Osb.×Poncirus Trifoliata L. Osb.）. The trees were subjected to two irrigation treatments： （1） sustainable deficit irrigation （SDI） established with water supplied at 60% of the crop evapotranspiration （ETc） and （2） low frequency deficit irrigation （LFDI） irrigated according to the plant water status. In addition, a treatment irrigated at 100% of ETc was included as a control （C）. Midday stem-water potential （ψUstem）, stomatal conductance （gs）, and micrometric trunk diameter fluctuations were measured during the maximum evapotranspirative demand period to evaluate the plant-water status, and establish the main relationships among them. The seasonal pattern of the studied variables had a behavior consistent with the contributions made by the volumes of applied irrigation water. Especially significant close relationships of ψstem with gs, and with the maximum daily shrinkage （MDS） were found. The lowest ψstem and gs values were registered in the treatments with lowest irrigations levels （SDI and LFDI）, being the MDS was significative higher than in the C treatment. The LFDI showed an oscillating behavior in these parameters, which was on line with the supplied irrigation restrictions cycles. Thus, according to the results of the present experiment the physiological stress indexes based in MDS or ψstem allow establishing different irrigation restriction cycles, encouraging important water saving without significant impact on yield and the fruit quality parameters.

Effect of Deficit Irrigation Practice on Nitrogen Mineralization and Nitrate Nitrogen Leaching under Semi-Arid Conditions

Agricultural sector acts as a major consumer of water which accounts for 70 percent of global freshwater use. Water scarcity acts as an imminent threat to agriculture, there is a need to use those irrigation and management practices that could overcome this overwhelming situation of water scarcity. Lab incubation study was designed to evaluate the effect of different moisture levels (50%, 60%, 70%, 80%, 90%, and 100% FC) on nitrogen mineralization rate. Net nitrogen mineralization was shown at 60% and 80% FC levels. Two optimized irrigation levels (I0.6 and I0.8) along with four levels of dairy manure (10, 15, 20, and 25 Mg ha-1) were used in a lysimetric trial. Nitrate-nitrogen was measured at four depths (D1: 30 cm, D2: 60 cm, D3: 90 cm, and D4: 120 cm). Results showed strong interaction of irrigation and dairy manure at all depths. Mean maximum nitrate-nitrogen concentration was shown under full irrigation at 120 cm soil depth with the application of DM ®25 Mg ha-1. Under two levels of deficit irrigation, I0.8 has shown maximum nitrate-nitrogen concentration at 90 cm soil depth with the application of DM25, however, deficit irrigation level I0.6 restricted nitrate-nitrogen movement up to 60 cm soil depth, and high concentration was found at 30 cm soil depth. We concluded that deficit irrigation practice along with dairy manure resulted in more nitrate-nitrogen in the upper 60 cm layer of soil where it can be more available for the crops.

The effects of deficit irrigation on nitrogen consumption,yield,and quality in drip irrigated grafted and ungrafted watermelon

The aim of this study is to determine the effects of deficit irrigation on nitrogen consumption,yield,and quality in grafted and ungrafted watermelon.The study was conducted in Cukurova region,Eastern Mediterranean,Turkey,between 2006 and 2008,and employed 3 irrigation rates（full irrigation（l_（100）） with no stress,moderate irrigation（Dl_（70））,and low irrigation（Dl_（50））;Dl_（70） and Dl_（50） were considered deficit irrigation） on grafted（CTJ,Crimson Tide＋Jumbo） and the ungrafted（CT,Crimson Tide） watermelon.The amount of irrigation water（IR） applied to the study plots were calculated based on cumulative pan evaporation that occurred during the irrigation intervals.Nitrogen consumption was 16%lower in CTJ plants than in CT plants.On the other hand,consumption of nitrogen was 28%higher in Dl_（50） plants than in Dl_（70） plants while it was 23%higher in Dl_（50） plants than in l_（100） plants.By grafting,the average amount of nitrogen content in seeds,pulps and peels for CTJ was 30,43 and 56%more than those of CT,respectively.The yield and the quality were not significantly affected by the deficit irrigation.In this respect,grafting of watermelon gave higher yield,but,it had a slight effect on fruit quality.The highest yield values of 16.90 and 19.32 kg plant^（-1） in 2008 were obtained with l_（100）and in CTJ plants,respectively.However,Dl_（50） treatment could be taken into account for the development of reduced irrigation strategies in semiarid regions where irrigation water supplies are limited.Additionally,the yield increased by applying CTJ treatment to the watermelon production.

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）.

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.

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.

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.

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.

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.

Effects of nitrogen application rates and irrigation regimes on grain yield and water use efficiency of maize under alternate partial rootzone irrigation

Faced with the scarcity of water resources and irrational fertilizer use,it is critical to supply plants with water and fertilizer in a coordinated pattern to improve yield with high water use efficiency(WUE).One such method,alternate partial root-zone irrigation(APRI),has been practiced worldwide,but there is limited information on the performance of different irrigation regimes and nitrogen(N)rates under APRI.The objectives of this study were to investigate the effects of varying irrigation regimes and N rates on shoot growth,grain yield and WUE of maize(Zea mays L.)grown under APRI in the Hexi Corridor area of Northwest China in 2014 and 2015.The three N rates were 100,200 and 300 kg N ha–1,designated N1,N2 and N3,respectively.The three irrigation regimes of 45–50%,60–65%and 75–80%field capacity(FC)throughout the maize growing season,designated W1,W2 and W3,respectively,were applied in combination with each N rate.The results showed that W2 and W3 significantly increased the plant height,stem diameter,crop growth rate,chlorophyll SPAD value,net photosynthetic rate(Pn),biomass,grain yield,ears per ha,kernels per cob,1000-kernel weight,harvest index,evapotranspiration and leaf area index(LAI)compared to W1 at each N rate.The N2 and N3 treatments increased those parameters compared to N1 in each irrigation treatment.Increasing the N rate from the N2 to N3 resulted in increased biomass and grain yield under W3 while it had no impact on those under the W1 and W2 treatments.The W3 N3 and W2 N2 and W2 N3 treatments achieved the greatest and the second-greatest biomass and grain yield,respectively.Increasing the N rate significantly enhanced the maximum LAI(LAI at the silking stage)and Pn under W3,suggesting that the interaction of irrigation and fertilizer N management can effectively improve leaf growth and development,and consequently provide high biomass and grain yield of maize.The W2 N2,W2 N3 and W3 N3 treatments attained the greatest WUE among all the treatments.Thus,either 60–65%FC coupled with 200–300 kg N ha–1 or 75–80%FC coupled with 300 kg N ha–1 is proposed as a better pattern of irrigation and nitrogen application with positive regulative effects on grain yield and WUE of maize under APRI in the Hexi Corridor area of Northwest China and other regions with similar environments.These results can provide a basis for indepth understanding of the mechanisms of grain yield and WUE to supply levels of water and nitrogen.

A simulation of winter wheat crop responses to irrigation management using CERES-Wheat model in the North China Plain

To improve efficiency in the use of water resources in water-limited environments such as the North China Plain（NCP）, where winter wheat is a major and groundwater-consuming crop, the application of water-saving irrigation strategies must be considered as a method for the sustainable development of water resources. The initial objective of this study was to evaluate and validate the ability of the CERES-Wheat model simulation to predict the winter wheat grain yield, biomass yield and water use efficiency（WUE） responses to different irrigation management methods in the NCP. The results from evaluation and validation analyses were compared to observed data from 8 field experiments, and the results indicated that the model can accurately predict these parameters. The modified CERES-Wheat model was then used to simulate the development and growth of winter wheat under different irrigation treatments ranging from rainfed to four irrigation applications（full irrigation） using historical weather data from crop seasons over 33 years（1981–2014）. The data were classified into three types according to seasonal precipitation： 〈100 mm, 100–140 mm, and 〉140 mm. Our results showed that the grain and biomass yield, harvest index（HI） and WUE responses to irrigation management were influenced by precipitation among years, whereby yield increased with higher precipitation. Scenario simulation analysis also showed that two irrigation applications of 75 mm each at the jointing stage and anthesis stage（T3） resulted in the highest grain yield and WUE among the irrigation treatments. Meanwhile, productivity in this treatment remained stable through different precipitation levels among years. One irrigation at the jointing stage（T1） improved grain yield compared to the rainfed treatment and resulted in yield values near those of T3, especially when precipitation was higher. These results indicate that T3 is the most suitable irrigation strategy under variable precipitation regimes for stable yield of winter wheat with maximum water savings in the NCP. The application of one irrigation at the jointing stage may also serve as an alternative irrigation strategy for further reducing irrigation for sustainable water resources management in this area.