Grain yield and water use efficiency of two types of winter wheat cultivars under different water regimes

To improve grain yields of winter wheat and water-use efficiency in the water-shortage region of the North China Plain (NCP), field experiments involving three irrigation levels and two types of winter-wheat cultivars (Shijiazhuang 8 and Xifeng 20, with moderate and strongly drought tolerance, respectively) were conducted over three growing seasons with different levels of precipitation. The results showed that irrigation significantly improved the grain yield of both wheat cultivars. The response of grain yield was largest in the dry year, followed by the normal and wet years. Shijiazhuang 8 responded more strongly than Xifeng 20. Compared to aboveground biomass under no irrigation treatment, the aboveground biomass of Shijiazhuang 8 and Xifeng 20 improved by 87.0% and 57.8%, respectively, in a dry year, by 27.2% and 18.3%, respectively, in a normal year, and by 13.7% and 11.7%, respectively, in a humid year when irrigation were applied twice. The total water use (TWU) of the two cultivars also increased upon irrigation. The increase was more pronounced in the dry year than in the normal or humid years. However, there were no significant differences in the TWUs of the two cultivars. The water-use efficiency at grain-yield level (WUE_y) of Shijiazhuang 8 increased significantly upon irrigation in the dry year, did not change in the normal year, and showed a clear decline in the humid year, while the WUE_y of Xifeng 20 was reduced by irrigation in each of the three growing seasons. The harvest index (HI) was not altered by irrigation but it did vary by growing season. The HI of Shijiazhuang 8 was always higher than that of Xifeng 20. A positive correlation was found between both the WUE_y and the water-use efficiency at the aboveground-biomass level (WUE_bm) and the HI. This suggests that the changes in WUE_y as a result of irrigation are mainly due to changes in the WUE_bm and that the differences in WUE_y between the two cultivars were due to differences in WUE_bm and HI. These results suggest the following. (1) The TWUs in the two cultivars were roughly equal, although their levels of drought tolerance differed. (2) A wheat cultivar with moderate drought tolerance is expected to be more suitable for the semi-arid region of the NCP. The variety with strongly drought tolerance was able to keep its biomass high and to maintain grain yield under serious drought stress. (3) In order to both increase grain yield and WUE_y, two irrigations in a dry year, one irrigation in a normal year, and no irrigation in a humid year will give optimal results in the studied region.     

Grain yield,yield components,drought sensitivity and water use efficiency of spring wheat subjected to water stress at various growth stages

Summary The influence of water stress at various growth stages on yield and yield structure of spring wheat (Triticum aestivum, L., cv. Sappo) was investigated using lysimeters in the field, automatically protected from rain by a mobile glass roof. Each drought treatment consisted of a single period without irrigation. Irrigation was resumed when all available soil water (100 mm between field capacity and permanent wilting to a depth of 100 cm) had been used. The drought periods were defined as beginning when relative evapotranspiration decreased below one and ending at reirrigation. The first drought occurred during tillering and jointing and the final one during grain formation.     

Potato water use and yield under furrow irrigation

Field experiments were conducted to study the effects of plant-furrow treatments and levels of irrigation on potato (Solanum tuberosum L.) water use, yield, and water-use efficiency. The experiments were carried out under deficit irrigation conditions in a sandy loam soil of eastern India in the winter seasons of 1991/92, 1992/93, and 1993/94. Two plant-furrow treatments and two levels of irrigation were considered. The two plant-furrow treatments were F₁ - furrows with single row of planting in each ridge with 45 cm distance between adjacent ridges, and F₂ - furrows with double rows of planting spaced 30 cm apart in each ridge with 60 cm distance between adjacent ridges. The two levels of irrigation (LOI) were I₁ - 0.9 IW/CPE and I₂ - 1.2 IW/CPE, where IW is irrigation water of 5 cm and CPE is cumulative pan evaporation. Treatment F₂ produced highest tuber yield in all years with average value of 10,610 kg ha ^-1 and 12,780 kg ha ^-1 at LOI of I₁ and I₂, respectively. On average, six irrigations with a total of 25 cm, and seven irrigations with a total of 30 cm were required for both treatments F₁ and F₂ at LOI of I₁ and I₂, respectively. Treatment F₂ resulted in a significantly higher number of branches and tubers per plant, foliage coverage and water-use efficiency for both irrigation levels than treatment F₁. Average daily crop evapotranspiration was found to range from 1.1 to 3.4 mm and from 1.2 to 3.9 mm for treatment F₁ and from 1.1 to 3.6 mm and from 1.2 to 4.0 mm for treatment F₂ at LOI of I₁ and I₂, respectively.     

Responses of crop yield and water use efficiency to climate change in the North China Plain

Based on future climate change projections offered by IPCC, the responses of yields and water use efficiencies of wheat and maize to climate change scenarios are explored over the North China Plain. The climate change projections of 21st century under A2A, B2A and A1B are from HadCM3 global climate model.A climate generator (CLIGEN) is applied to generate daily weather data of selected stations and then the data is used to drive CERES-Wheat and Maize models. The impacts of increased temperature and CO₂ on wheat and maize yields are inconsistent. Under the same scenario, wheat yield ascended due to climatic warming, but the maize yield descended. As a more probable scenario, climate change under B2A is moderate relative to A2A and A1B. Under B2A in 2090s, average wheat yield and maize yield will respectively increase 9.8% and 3.2% without CO₂ fertilization in this region. High temperature not only affects crop yields, but also has positive effect on water use efficiencies, mainly ascribing to the evapotranspiration intensification. There is a positive effect of CO₂ enrichment on yield and water use efficiency. If atmospheric CO₂ concentration reaches nearly 600 ppm, wheat and maize yields will increase 38% and 12% and water use efficiencies will improve 40% and 25% respectively, in comparison to those without CO₂ fertilization. However, the uncertainty of crop yield is considerable under future climate change scenarios and whether the CO₂ fertilization may be realized is still needed further research.     

Canopy-air temperature differentials,water use and yield of chickpea in a semi-arid environment

Summary Stress degree days (SDD) and canopy-air temperature differential summation procedures were used to quantify the response of crops of chickpea (Cicer arietinum L.) to soil water availability and atmospheric demand over a four year period on a deep and medium-deep Vertisol in India using different irrigation treatments and planting dates. Canopy temperatures measured between 13.00–14.00 h provided a good index of the daily mean canopy temperature. Differences in the diurnal variation in the canopy-air temperature differentials between irrigated and non-irrigated chickpea reflected clearly the differential response of the crop to soil water availability. Total water use of chickpea decreased with increasing SDD. Data pooled over three growing seasons showed a close relationship between SDD and yield of chickpea. Calculated water stress index (WSI) which includes the vapor pressure deficit term showed a similar relationship with yield to that with SDD.Approved for publication as ICRISAT Journal Article 580(Via Paris)     

Tuber yield, water and fertilizer productivity in early potato as affected by a combination of irrigation and fertilization

Excessive amounts of irrigation water and fertilizers are often utilized for early potato cultivation in the Mediterranean basin. Given that water is expensive and limited in the semi-arid areas and that fertilizers above a threshold level often prove inefficacious for production purposes but still risk nitrate and phosphorous pollution of groundwater, it is crucial to provide an adequate irrigation and fertilization management. With the aim of achieving an appropriate combination of irrigation water and nutrient application in cultivation management of a potato crop in a Mediterranean environment, a 2-year experiment was conducted in Sicily (South Italy). The combined effects of 3 levels of irrigation (irrigation only at plant emergence, 50% and 100% of the maximum evapotranspiration - ETM) and 3 levels of mineral fertilization (low: 50, 25 and 75 kg ha⁻¹, medium: 100, 50 and 150 kg ha⁻¹ and high: 300, 100 and 450 kg ha⁻¹ of N, P₂O₅ and K₂O) were studied on the tuber yield and yield components, on both water irrigation and fertilizer productivity and on the plant source/sink (canopy/tubers dry weight) ratio. The results show a marked interaction between level of irrigation and level of fertilization on tuber yield, on Irrigation Water Productivity and on fertilizer productivity of the potato crop. We found that the treatments based on 50% ETM and a medium level of fertilization represent a valid compromise in early potato cultivation management. Compared to the high combination levels of irrigation and fertilization, this treatment entails a negligible reduction in tuber yield to save 90 mm ha⁻¹ year⁻¹ of irrigation water and 200, 50 and 300 kg ha⁻¹ year⁻¹ of N, P₂O₅ and K₂O, respectively, with notable economic savings for farmers compared to the spendings that are usually made.     

Nutrient management adaptation for dryland maize yields and water use efficiency to long-term rainfall variability in China

Rainfed crop production in northern China is constrained by low and variable rainfall, and by improper management practices. This study explored both the impact of long-term rainfall variability and the long-term effects of various combinations of maize stover, cattle manure and mineral fertiliser (NP) applications on maize (Zea mays L.) yields and water use efficiency (WUE) under reduced tillage practices, at Shouyang Dryland Farming Experimental Station in northern China from 1993 onwards. The experiment was set up according to an incomplete, optimal design, with 3 factors at five levels and 12 treatments including a control with two replications. Grain yields were greatly influenced by the amount of rain during the growing season, and by soil water at sowing. Annual mean grain yields ranged from 3 to 10 t ha⁻¹ and treatment mean yields from 4.2 to 7.2 t ha⁻¹. The WUE ranged from 40 in treatments with balanced nutrient inputs in dry (weather/or soil) years to 6.5 kg ha⁻¹ mm⁻¹ for the control treatments in wet years. The WUE averaged over the 15-year period ranged from 11 to 19 kg ha⁻¹ mm⁻¹. Balanced combination of stover (3000-6000 kg), manure (1500-6000 kg) and N fertiliser (105 kg) gave the highest yield and hence WUE. It is suggested that 100 kg N per ha should be a best choice, to be adapted according to availability of stover and manure. Possible management options under variable rainfall conditions to alleviate occurring moisture stress for crops must be tailored to the rainfall pattern. The potentials of split applications, targeted to the need of the growing crop (response nutrient management), should be explored to further improve grain yield and WUE.     

Effects of water deficits on growth, yield and water productivity of drip-irrigated onion (Allium cepa L.) in an arid region of Northwest China

Aiming at investigating an appropriate irrigation management strategy that could lead to increase onions yields and improve water productivity (WP), a two-year field experiment was conducted in the arid region of Northwest China with drip irrigation and plastic mulch. Eight treatments were considered: four with different levels of water stress throughout the crop season, and four where water stress was applied at the establishment, development, bulbification and ripening stages. The seasonal actual evapotranspiration (ET_a), plant height, above-ground biomass, yield (total, high-quality and marketable quality yields) as well as related irrigation and total water productivity were determined. Plant heights, above-ground biomass and the referred yields have shown to be sensitive to water stress, particularly during the development and bulbification stages. Due to the importance of quality of horticultural products, the WP computed with the yields of high-quality bulbs revealed the most informative contrarily to the WP computed with the total yields. It could be concluded that water stress has to be avoided during the development and bulbification stages, and only small deficits are acceptable if applied throughout the crop season.     

Forage sorghum yield and water use efficiency under variable irrigation

The response of forage sorghum [Sorghum bicolor (L.) Moench] to three irrigation treatments in a semiarid environment was studied in the field for two seasons. Treatments were light frequent, moderate less frequent, and heavy infrequent irrigation, where irriga-tion water at 8 mm day^–1 was delivered every 7, 10, and 13 days, respectively. These irrigation regimes meant heavier water inputs with increasing irrigation frequency. Plant heights and leaf area indices of forage sorghum were higher in the frequently watered plots than in plots where irrigation water was delivered less frequently. Averaged over the two seasons, maximum dry matter (DM) yields were 16.3, 11.8, and 10.5 tonnes ha^–1 for frequent, intermediate, and infrequent irrigation regimes, respectively. Light, frequent irrigation resulted in a significantly higher water use efficiency (WUE) compared to the other two regimes, thus increasing the return from irrigation. These results suggest that in such semiarid environments, DM yields and WUE of forage sorghum could be increased by combining light irrigation with a short interval. Received: 6 February 1997     

灌水量对烤烟产量和水分利用效率的影响

灌水时期不当或灌水量过大会降低烟叶的产量,同时造成水分的浪费,探究烟草适宜的灌水量至关重要。在蒸渗仪中开展试验,研究了不同灌水量对土壤水分、烤烟的水分利用效率和产量的影响。结果表明：烤烟 K326各处理不同土层含水率变化规律比较一致,（0,10]cm 土层含水率受气温、日照等气候因素较大;（10,20]cm 土壤含水率变化较剧烈;（20,60]cm 土壤含水率在整个生育期变化比较平缓,尤其在成熟后期各处理均出现不同程度的回升趋势,结合烤烟成熟期生理活动减弱、需水量减少,说明成熟期采取较小的灌水量比较适宜。成熟期烤烟的干物质产量在一定范围内随灌水量的增大而增加,如果继续加大灌水量将出现“报酬递减”现象。结合烟叶产量、烟株长势、耗水量和水分利用效率的结果,表明2700～3000 m3／hm2可以作为烤烟K326适宜的灌水量。在烤烟生产中,应均衡协调产量、水分利用效率与耗水量之间的关系,在高产前提下,适当减少灌水量,可达到既高产又节水的协调统一。     

Water use,water-use efficiency and yield of dryland chickpea as influenced by P fertilization,stored soil water and crop season rainfall

Dryland chickpea is grown on stored water in the soil profile and with limited crop season rainfall (CSR). In a field experiment, carried out for 3 years on silty loam soil, water extraction pattern, water use and its efficiency by chickpea in relation to P application, stored soil water and crop season rainfall have been investigated. Stored soil water varied from 182 to 246 mm in a meter profile and the CSR varied from 72 to 184 mm.Response of P application increased with increasing initial water storage in the soil profile. The first 60–100 days of crop growth appeared to be the most critical. Water stress during this period severely affected the yield. Rainfall after 100 days did not appear to have been fully utilized by the crop, especially when the crop had already suffered from water stress between 60 and 100 days. Compared with the control, P application increased yield, water use and water-use efficiency. Soil water depletion was 25% greater for the fertilized crop than for the unfertilized crop.     

Effects of different water supply regimes on water use and yield performance of spring wheat in a simulated semi-arid environment

This research explores the limited irrigation strategies based on root-to-shoot communication that exists in spring wheat, and examines the effects of root-sourced signals on water use and yield performance of three genotypes of spring wheat (Triticum aestivum) under three different irrigation regimes. Four treatments, CT (well-watered management), DIu (supplying water to the upper layer to maintain soil moisture in the entire pot at 50–60% of field water capacity (FWC)), and DId (supplying water to the lower layer to maintain soil moisture in the entire pot at 50–60% FWC), were employed. The treatment DIu was used to simulate frequent post-sowing irrigation with small amount of water in each time, and DId was used to simulate pre-sowing irrigation with the same amount of water. Plants were grown in cylinder pots outdoors. A non-hydraulic root signal was induced from seedling to tillering stage in the treatment DId. But after the jointing stage, the signal resulted in a reduction in root biomass and root length in the upper layer and an increase in root biomass and root length in the middle layer as compared with the treatment DIu. The water use efficiencies of the three genotypes were the highest in the treatment DId and the lowest in the treatment DIu for the genotypes A and C. This suggests that under the conditions of the same amount of water supply frequent post-sowing irrigation to the upper soil layer had lower water use efficiency and grain yield, whereas pre-sowing irrigation to the lower soil layer tended to have higher grain yield and higher water use efficiency.     

Effect of saline water on cucumber (Cucumis sativus L.) yield and water use under drip irrigation in North China

Saline water has been included as an important substitutable resource for fresh water in agricultural irrigation in many fresh water scarce regions. In order to make good use of saline water for agricultural irrigation in North China, a semi-humid area, a 3-year field experiment was carried out to study the possibility of using saline water for supplement irrigation of cucumber. Saline water was applied via mulched drip irrigation. The average electrical conductivity of irrigation water (EC_iw) was 1.1, 2.2, 2.9, 3.5 and 4.2 dS/m in 2003 and 2004, and 1.1, 2.2, 3.5, 4.2 and 4.9 dS/m in 2005. Throughout cucumber-growing season, the soil matric potential at 0.2 m depth immediately under drip emitter was kept higher than −20 kPa and saline water was applied after cucumber seedling stage. The experimental results revealed that cucumber fruit number per plant and yield decreased by 5.7% per unit increase in EC_iw. The maximum yield loss was around 25% for EC_iw of 4.9 dS/m, compared with 1.1 dS/m. Cucumber seasonal accumulative water use decreased linearly over the range of 1.5-6.9% per unit increase in EC_iw. As to the average root zone EC_e (electrical conductivity of saturated paste extract), cucumber yield and water use decreased by 10.8 and 10.3% for each unit of EC_e increase in the root zone (within 40 cm away from emitter and 40 cm depths), respectively. After 3 years irrigation with saline water, there was no obvious tendency for EC_e to increase in the soil profile of 0-90 cm depths. So in North China, or similar semi-humid area, when there is no enough fresh water for irrigation, saline water up to 4.9 dS/m can be used to irrigate field culture cucumbers at the expense of some yield loss.     

生物可降解地膜对棉花产量及水分利用效率的影响

为了探求华北平原棉花可降解地膜覆盖替代普通膜覆盖的可行性,解决白色污染问题,试验设置4种处理:6 μm PE普通地膜(PE)、8 μm生物可降解地膜(M1)、6 μm生物可降解地膜(M2)及不覆盖地膜(CK),分析比较各处理对棉花出苗率、叶面积指数(LAI)、农田耗水速率、产量及水分利用效率(WUE)的影响.结果表明,与处理CK相比,覆盖地膜显著提高了棉花出苗率,但3种覆膜处理间差异不具有统计学意义;在棉花生育前期,2种生物可降解地膜处理的LAI显著低于PE处理的.3种覆膜处理之间的籽棉产量和霜前花率的差异均不具有统计学意义.3种覆膜处理间WUE的差异不具有统计学意义,但均显著高于CK的.2种生物可降解地膜处理相较于PE,对棉花的出苗率、霜前花率、籽棉产量及WUE的差异均不具有统计学意义.相较于PE,使用6 μm生物可降解膜不会造成棉花耗水量升高,而8 μm可降解膜则显著增加了棉花的耗水量.因此6 μm生物降解膜取代PE膜较好.     

Effect of irrigation and nitrogen on yield,yield components and water use efficiency of barley in Saudi Arabia

Water use efficiency and yield of barley were determined in a field experiment using different irrigation waters with and without nitrogen fertilizer on a sandy to loamy sand soil during 1994–1995 and 1995–1996. Depending upon different fertilizer treatments, the overall mean crop yield ranges for two crop seasons were: greenmatter from 19.48–55.0 Mg ha⁻¹ (well water) and 21.92–66.5 Mg ha⁻¹ (aquaculture effluent); drymatter from 6.86–20.69 Mg ha⁻¹ (well water) and 7.87–20.90 Mg ha⁻¹ (aquaculture effluent); biomass from 4.12–21.31 Mg ha⁻¹ (well water) and 8.10–19.94 Mg ha⁻¹ (aquaculture effluent) and grain yield from 2.12–5.50 Mg ha⁻¹ (well water) and 3.25–7.25 Mg ha⁻¹ (aquaculture effluent). The WUE for grain yield was 3.37–8.74 kg ha⁻¹ mm⁻¹ (well water) and 5.17–11.53 kg ha⁻¹ mm⁻¹ (aquaculture effluent). The WUE for total biomass ranged between 6.55–33.88 kg⁻¹ ha⁻¹ mm⁻¹ (well water) and 12.88–31.70 kg ha⁻¹ mm⁻¹ (aquaculture effluent). The WUE for drymatter was 10.91–32.90 kg ha⁻¹ mm⁻¹ (well water) and 12.51–33.22 kg ha⁻¹ mm⁻¹ (aquaculture effluent). It was found that grain yield and WUE obtained in T-4 and T-5 irrigated with well water and receiving 75 and 100% nitrogen requirements were comparable with T-4 and T-5 irrigated with aquaculture effluent and receiving 0 and 25% nitrogen requirements. In conclusion, application of 100 to 150 kg N ha⁻¹ for well water and up to 50 kg N ha⁻¹ for aquaculture effluent irrigation containing 40 Mg N l⁻¹ would be sufficient to obtain optimum grain yield and higher WUE of barley in Saudi Arabia.     

Effects of rainfall harvesting and mulching technologies on water use efficiency and crop yield in the semi-arid Loess Plateau, China

In semi-arid areas, crop growth is greatly limited by water. Amount of available water in soil can be increased by surface mulching and other soil management practices. Field experiments were conducted in 2005 and 2006 at Gaolan, Gansu, China, to determine the influence of ridge and furrow rainfall harvesting system (RFRHS), surface mulching and supplementary irrigation (SI) in various combinations on rainwater harvesting, amount of moisture in soil, water use efficiency (WUE), biomass yield of sweet sorghum (Sorghum bicolour L.) and seed yield of maize (Zea mays L.). In conventional fields without RFRHS, gravel-sand mulching produced higher biomass yield than plastic-mulching or straw-mulching. In plastic-mulched fields, an increasing amount of supplemental irrigation was needed to improve crop yield. There was no effect of RFRHS without plastic-covered ridge on rainwater harvesting when natural precipitation was less than 5 mm per event. This was due to little runoff of rainwater from frequent low precipitation showers, and most of the harvested rainwater gathered at the soil surface is lost to evaporation. In the RFRHS, crop yield and WUE were higher with plastic-covered ridges than bare ridges, and also higher with gravel-sand-mulched furrows than bare furrows in most cases, or straw-mulched furrows in some cases. This was most likely due to decreased evaporation with plastic or gravel-sand mulch. In the RFRHS with plastic-covered ridges and gravel-sand-mulched furrows, application of 30 mm supplemental irrigation produced the highest yield and WUE for sweet sorghum and maize in most cases. In conclusion, the findings suggested the integrated use of RFRHS, mulching and supplementary irrigation to improve rainwater availability for high sustainable crop yield. However, the high additional costs of supplemental irrigation and construction of RFRHS for rainwater harvesting need to be considered before using these practices on a commercial scale.     

水肥耦合对温室番茄产量、水分利用效率和品质的影响

为指导日光温室番茄高产节水优质的灌溉施肥,以番茄为研究对象,设置3种施肥方式(总施肥量相同,施肥时间不同,其中F₁:不施底肥,番茄移栽后随水追施总肥量的30%,剩余70%平分6次追肥,F₂:底肥施1/2,剩余平分6次追肥,F₃:全施底肥不追肥)和3种土壤水势的灌水下限(W₁:-30 kPa,W₂:-50 kPa,W₃:-70 kPa),研究滴灌条件下水肥耦合对番茄耗水量、产量、水分利用效率和品质的影响.结果表明:施肥方式对番茄的耗水量差异不具有统计学意义,而灌水下限对耗水量有极显著性影响,且耗水量与灌水量呈极显著的正相关关系(P<0.01);与产量最大处理F₂W₁相比,F₂W₂处理产量降低6.91%,但节水14.83%,水分利用效率提高8.51%;TTS质量分数与平均单果重呈极显著负相关,而与除糖酸比外其他影响品质指标呈显著性正相关关系;综合考虑产量、WUE及TTS质量分数,利用TOPSIS综合评价方法,确定了温室滴灌条件下番茄节水调质的最优灌溉施肥模式为:移栽前施入底肥为总肥量的50%,移栽后灌水20 mm,进入开花坐果期以后,20 cm土层的土壤水势控制在-50 kPa以上,每次灌水定额为10 mm,剩余肥料每隔1次灌水追肥1次,将剩余50%的肥料分6次追肥.研究成果为制定日光温室番茄节水高产优质的灌溉模式提供了理论依据.     

Impacts of water saving on groundwater balance in a large-scale arid irrigation district,Northwest China

Water saving practices are essential for sustainable use of water resources in semiarid regions. To understand the impacts of different water saving measures on groundwater resources, the Hetao Irrigation District in Northwest China was chosen in this study. Based on the data from 1991 to 2010, a groundwater balance model was calibrated and validated. The simulation results showed that irrigation-induced infiltration (92 % of the total groundwater recharge) and groundwater evaporation (92 % of the total groundwater discharge) were the primary factors controlling groundwater table fluctuations during irrigation seasons. The impacts of different water saving scenarios on groundwater balance components were then evaluated. The results revealed that the conjunctive use of water resources was the most effective way to improve water use efficiency (reducing surface water diversions by 52 %) and the depth to groundwater table increased by up to 79 cm. However, deeper groundwater tables may have a negative effect on crop growth due to reduced upward fluxes of groundwater into root zones. Therefore, future studies are needed to evaluate the impacts of different water saving measures on both water resources and crop yields. The results of this study provide further insights into effectively managing water resources in water-limited agricultural areas.     

Effects of irrigation regimes on the yield and water use of strawberry

Summary Strawberry plants (Fragaria x annanasa D. cv Chandler) were grown in field plots and in drainage lysimeters under controlled soil moisture regimes. Four irrigation treatments were established by watering the plants when soil water potential reached -0.01, -0.03,-0.05 and -0.07 MPa. The maximum yield was attained at -0.01 MPa soil water potential. Differences in yield were caused by both changes in the number of fruits per plant and in the fresh weight per fruit. Yield reductions were associated with reductions in total assimilation rate resulting from the decreased assimilatory surface area in plants irrigated at lower soil water potentials. The crop water production function calculated on a fruit fresh weight basis resulted in a yield response factor (K _y) of 1.01.     

The effect of drought on barley yield and water use in two contrasting years

Summary Results are presented for an experiment in 1979 in which mobile shelters were used to exclude rainfall; responses are compared with those in a hotter and drier year, 1976. The continuous drought treatment achieved a larger maximum deficit in 1979 than in 1976. The relationship between rate of water use as a fraction of the potential evaporation rate and soil water deficit was similar in the two years. Yield reductions due to drought were smaller in 1979, as expected from the smaller evaporation rates and therefore smaller potential soil water deficits. Dry matter production was related to water use, but the relationship differed between years. The difference can be related to the saturation vapour pressure deficit. Components of yield were affected differently in the two years; drought after anthesis decreased yield in 1979 by decreasing grain numbers not grain size.