Yields,growth and water use under chemical topping in relations to row configuration and plant density in drip-irrigated cotton

Background Water deficit is an important problem in agricultural production in arid regions.With the advent of wholly mechanized technology for cotton planting in Xinjiang,it is important to determine which planting mode could achieve high yield,fiber quality and water use efficiency(WUE).This study aimed to explore if chemical topping affected cotton yield,quality and water use in relation to row configuration and plant densities.Results Experiments were carried out in Xinjiang China,in 2020 and 2021 with two topping method,manual topping and chemical topping,two plant densities,low and high,and two row configurations,i.e.,76 cm equal rows and 10+66 cm narrow-wide rows,which were commonly applied in matching harvest machine.Chemical topping increased seed cotton yield,but did not affect cotton fiber quality comparing to traditional manual topping.Under equal row spacing,the WUE in higher density was 62.4%higher than in the lower one.However,under narrow-wide row spacing,the WUE in lower density was 53.3%higher than in higher one(farmers’practice).For machine-harvest cotton in Xinjiang,the optimal row configuration and plant density for chemical topping was narrow-wide rows with 15 plants m-2 or equal rows with 18 plants m-2.Conclusion The plant density recommended in narrow-wide rows was less than farmers’practice and the density in equal rows was moderate with local practice.Our results provide new knowledge on optimizing agronomic managements of machine-harvested cotton for both high yield and water efficient.

Effects of thinning and understory removal on water use efficiency of Pinus massoniana:evidence from photosynthetic capacity and stable carbon isotope analyses

Understanding the relationship between forest management and water use efficiency(WUE)is important for evaluating forest adaptability to climate change.However,the effects of thinning and understory removal on WUE and its key controlling processes are not well understood,which limits our comprehension of the physiological mechanisms of various management practices.In this study,four forest management measures(no thinning:NT;understory removal:UR;light thinning:LT;and heavy thinning:HT)were carried out in Pinus massoniana plantations in a subtropical region of China.Photosynthetic capacity and needle stable carbon isotope composition(δ^(13)C)were measured to assess instantaneous water use efficiency(WUE_(inst))and long-term water use efficiency(WUE_(i)).Multiple regression models and structural equation modelling(SEM)identified the effects of soil properties and physiological performances on WUE_(inst)and WUE_(i).The results show that WUE_(inst)values among the four treatments were insignificant.However,compared with the NT stand(35.8μmol·mol^(-1)),WUE_(i)values significantly increased to 41.7μmol·mol^(-1)in the UR,50.1μmol·mol^(-1)in the LT and 46.6μmol·mol^(-1)in HT treatments,largely explained by photosynthetic capacity and soil water content.Understory removal did not change physiological performance(needle water potential and photosynthetic capacity).Thinning increased the net photosynthetic rate(A_n)but not stomatal conductance(g_s)or predawn needle water potential(ψ_(pd)),implying that the improvement in water use efficiency for thinned stands was largely driven by radiation interception than by soil water availability.In general,thinning may be an appropriate management measure to promote P.massoniana WUE to cope with seasonal droughts under future extreme climates.

Effects of Water-Fertilizer Coupling on Growth Characteristics and Water Use Efficiency of Camellia petelotii Seedlings

Camellia petelotii(Merr.)Sealy is an endangered Chinese native species that originates from Guangxi Zhuang Autonomous Region,China.Previous research demonstrated that proper water and fertilizer treatments could improve the growth and quality of Camellia species.This study uses a three-factor,five-level quadratic rotational combination experimental design to investigate the impact of water-fertilizer coupling on plant growth character-istics and the most suitable treatment for 24-month-old grafted C.petelotii seedlings.The experimental design includes irrigation levels[30%,40%,55%,70%,80%offield capacity(FC)],nitrogen application(0,2.17,5.43,8.70,10.87 g·plant^(-1)),and phosphorus application(0,0.96,2.40,3.85,4.81 g·plant^(-1)).The results indicated that:(1)Water-nitrogen and water-phosphorus interactions significantly affected ground diameter,chlorophyll content and specific leaf weight(SLW),while water-nitrogen interactions significantly affected plant height and photo-synthesis;(2)Application of nitrogen(8.70 g·plant^(-1))and phosphorus(3.85 g·plant^(-1))fertilizers under appropri-ate irrigation conditions(40%FC and 70%FC)improved growth.Applying fertilizers containing either nitrogen(10.87 g·plant^(-1))or phosphorus(4.81 g·plant^(-1))under adequate irrigation(55%FC)increased the Chl content.However,high nitrogen levels(10.87 g·plant^(-1))reduced photosynthesis.Conversely,it was enhanced under appropriate phosphorus(4.81 g·plant^(-1))when the irrigation level was 55%FC,indicating the sensitivity of C.pete-lotii seedlings to nitrogen fertilizer.(3)Under specific conditions of 40%FC or 70%FC irrigation and 8.70 g·plant^(-1) or 2.17 g·plant^(-1) nitrogen fertilizer application,3.85 g·plant^(-1) phosphorus addition boosted the SLW whereas,0.96 g·plant^(-1) phosphorus addition inhibited it.Under W=55%FC,deficiencies in either nitrogen(N=0 g·plant^(-1))or phosphorus(P=0 g·plant^(-1))significantly decreased leaf growth,affecting SLW.In summary,C.petelotii was more sensitive to nitrogen fertilizer at W=55%FC,and nitrogen deficiency inhibited C.petelotii growth in terms of ground diameter more than phosphorus deficiency.The C.petelotii seedlings performed best when treated with 55%FC,5.43 g·plant^(-1) nitrogen,2.40 g·plant^(-1) phosphorus per plant.These parameter esti-mates could optimize water and fertilizer application for C.petelotii seedlings.

Regulation effects of water and nitrogen on yield,water,and nitrogen use efficiency of wolfberry

Wolfberry(Lycium barbarum L.)is important for health care and ecological protection.However,it faces problems of low productivity and resource utilization during planting.Exploring reasonable models for water and nitrogen management is important for solving these problems.Based on field trials in 2021 and 2022,this study analyzed the effects of controlling soil water and nitrogen application levels on wolfberry height,stem diameter,crown width,yield,and water(WUE)and nitrogen use efficiency(NUE).The upper and lower limits of soil water were controlled by the percentage of soil water content to field water capacity(θ_(f)),and four water levels,i.e.,adequate irrigation(W0,75%-85%θ_(f)),mild water deficit(W1,65%-75%θ_(f)),moderate water deficit(W2,55%-65%θ_(f)),and severe water deficit(W3,45%-55%θ_(f))were used,and three nitrogen application levels,i.e.,no nitrogen(N0,0 kg/hm^(2)),low nitrogen(N1,150 kg/hm^(2)),medium nitrogen(N2,300 kg/hm^(2)),and high nitrogen(N3,450 kg/hm^(2))were implied.The results showed that irrigation and nitrogen application significantly affected plant height,stem diameter,and crown width of wolfberry at different growth stages(P<0.01),and their maximum values were observed in W1N2,W0N2,and W1N3 treatments.Dry weight per plant and yield of wolfberry first increased and then decreased with increasing nitrogen application under the same water treatment.Dry weight per hundred grains and dry weight percentage increased with increasing nitrogen application under W0 treatment.However,under other water treatments,the values first increased and then decreased with increasing nitrogen application.Yield and its component of wolfberry first increased and then decreased as water deficit increased under the same nitrogen treatment.Irrigation water use efficiency(IWUE,8.46 kg/(hm^(2)·mm)),WUE(6.83 kg/(hm^(2)·mm)),partial factor productivity of nitrogen(PFPN,2.56 kg/kg),and NUE(14.29 kg/kg)reached their highest values in W2N2,W1N2,W1N2,and W1N1 treatments.Results of principal component analysis(PCA)showed that yield,WUE,and NUE were better in W1N2 treatment,making it a suitable water and nitrogen management mode for the irrigation area of the Yellow River in the Gansu Province,China and similar planting areas.

Response of Growth and Water Use Efficiency of Spring Wheat to Whole Season CO_2 Enrichment and Drought

Whole_growing season pot experiments were conducted to examine the response of growth and water use efficiency ( WUE ) of spring wheat ( Triticum aestivum L. cv. Gaoyuan 602) to CO 2 enrichment. Wheat plants were grown in open_top chambers (OTCs) subject to two concentrations of CO 2 ()(350 and 700 μL/L, hereafter 'ambient' and 'elevated' respectively) and three soil water levels (80%, 60% and 40% field water capacity ( FWC ), hereafter 'high soil moisture', 'medium soil moisture' and 'low soil moisture' respectively). Elevated CO 2 greatly increased leaf net photosynthesis ( Pn ) at all three soil water levels. The Pn of plants growing under elevated was 22% lower than that of plants growing at ambient when measured with the same (700 μL/L). Plant growth was enhanced by elevated throughout the growing season, with an increase of 14.8% in shoot dry weight at harvest under high soil moisture, and leaf area was increased by about 20% at all three soil water levels. Elevated in combination with high soil moisture increased the ratio of plant shoot dry weight to height by 15.7%, while this ratio was decreased by over 50% when plants were subject to drought. Elevated also increased the water use efficiency of wheat, mainly due to decreases in transpiration and cumulative consumption of water, and an increase in shoot dry weight, with the biggest value of 30% occurring at high soil water moisture level. Compared to high soil moisture, drought decreased shoot dry weight by 72% under ambient , and by 76% under elevated . Similarly, drought also reduced WUE by 19% under ambient , and 23% under elevated . Our results indicate that: (1) elevated can increase the photosynthetic rates, growth and WUE of wheat plants; (2) long_term exposure to high may result in lower photosynthetic capacity; (3) high stimulates plants lateral growth more than vertical growth; (4) the effects of CO 2 enrichment on plants depend on soil water status, with plants benefiting more from CO 2 enrichment if sufficient water is supplied; and (5) drought may cause relatively more reduction in plant growth and WUE under future elevated conditions.

Variations in Composition and Water Use Efficiency of Plant Functional Groups Based on Their Water Ecological Groups in the Xilin River Basin

Major plant species in the Xilin River Basin were grouped into six plant functional groups (PFGs) based on their water ecological groups: xerophytes, mesoxerophytes, xeromesophytes, mesophytes, hygromesophytes and hygrophytes. We surveyed the composition, delta(13)C values and proline concentration of PFGs in eight different plant communities along a soil moisture gradient. Results show that: (1) PFGs occurred variously in eight steppe communities with different soil moisture status. In wetter habitats, hygromesophytes and hygrophytes were more abundant and accounted for the majority of aboveground biomass, whereas xerophytes and mesoxerophytes became more conspicuous in dryer habitats; (2) the numerical order of the mean delta(13)C values of PFGs is as follows: xerophytes (-26.38parts per thousand) = mesoxerophytes (-26.51parts per thousand) > xeromesophytes (-27.02parts per thousand) > mesophytes (-27.56parts per thousand) = hygromesophytes and hygrophytes (-27.80parts per thousand); (3) xerophytes maintained relative higher delta(13)C values and water use efficiency (WUE) in habitats of different water availability, whereas delta(13)C values of xeromesophytes were more sensitive to change in soil water availability; (4) From xerophytes to hygrophytes, their proline content markedly increased. Significantly positive correlations existed between proline and biomass or delta(13)C values of different water ecological groups.

Species- and Habitat-variability of Photosynthesis, Transpiration and Water Use Efficiency of Different Plant Species in Maowusu Sand Area

Photosynthesis ( P n ), transpiration ( E ) and water use efficiency ( WUE ) of more than 66 arid sand species from different environmental habitats, shifting sand dune, fixed sand dune, lowland and wetland in the Maowusu Sand Area were analyzed and the relation among these characteristics and the resource utilization efficiency, taxonomic categories and growth forms of the species were assessed. The results showed that species from Chenopodiaceae, Gramineae, Leguminosae which possessed the C 4 photosynthesis pathway, or C 3 pathway and also with nitrogen_fixation capacities had higher or the highest P n values, i.e., 20～30 μmol CO 2·m -2 ·s -1 , while that of evergreen shrub of Pinaceae had the lowest P n values, i.e., 0～5 μmol CO 2·m -2 ·s -1 . Those species from Compositae, Scrophulariaceae, and Gramineae with C 3 pathway but no N_fixation capacity had the highest E rates, i.e., 20～30 mmol H 2O·m -2 ·s -1 and again the evergreen shrub together with some species from Salicaceae and Compositae had the lowest E rates, i.e., 0～5 mmol H 2O·m -2 ·s -1 . Species from Leguminosae, Gramineae and Chenopodiaceae with C 4 pathway or C 3 pathway with N_fixation capacity, both shrubs and grasses, generally had higher WUE . However, even the physiological traits of the same species were habitat_ and season_specific. The values of both P n and E in late summer were much higher than those in early summer, with average increases of 26%, 40% respectively in the four habitats. WUE in late summer was, however, 12% lower. Generally, when the environments became drier as a result of habitats changed, i.e., in the order of wetland, lowland, fixed sand dune and shifting sand dune, P n and E decreased but WUE increased.

Water Use of Leymus chinensis Community

Soil moisture of Leymus chinensis (Trin.) Tzvel. community has obviously stratified phenomena: the layer (0-40 cm) in which roots are concentrically distributed is directly influenced by precipitation and evapotranspiration. It can be called interaction layer of precipitation and evapotranspiration. The layer (40-120 cm), where water-storage capacity exchange lagged exchange of the root-layer water-storage capacity and the community evapotranspiration, can be called major water-storage layer. The layer (under 120 cm) can be called water relatively stable/balanced layer. The year 1996 was a normal flow year, and soil water had a surplus of 18 mm at the end of the growing season. The year 1998 was a high flow year, because leakage took place under continuous heavy rainfall, soil water had a deficit of 15 mm at the end of the growing season. Transpiration to evapotranspiration ( T/ET) value reflected not only the luxuriance degree of the community, but also the water use regime of the environmental resources. T/ET value was low (0.5) in May 1998, reaching 0.7 in June, then decreasing to 0.6 in July, due to the impact of rainfall inclining, while August reached the maximum (0.9), and September decreased to 0.6. Water use efficiency (WUE) was mainly restricted by the growing rate of plants under sufficient water condition (1998). Its seasonal changes were coincident with the grand period of growth of the plants. When both meanings of WUE and T/ET were analyzed profoundly, the concept of evapotranspiration efficiency (ETE) which can all-side reflect utilization regime of the environmental water resources was advanced.

Effects of Different Tillage Techniques on Yield and Water Use Efficiency in Broomcorn Millet

[Objective] The effects of different tillage techniques on dry matter accu- mulation, soil water content, water use efficiency and yield of broomcom millet were studied. [Method] With Jinsu 9 as an experiment material, the effects of deep tillage, traditional tillage and no tillage and rotary tillage on dry matter accumulation, soil water content, water use efficiency and yield of broomcom millet were investi- gated. [Result] Dry matter accumulation rate and accumulated amount were signifi- cantly higher in the deep tillage, no tillage and rotary tillage treatments than in the conventional tillage treatment, and the highest in the deep tillage treatment. The soil water content of the deep tillage treatment at 0-100 cm was higher than those of other tillage techniques, deep tillage also exhibited the highest soil water storage, and water use efficiency values were in order of deep tillage〉rotary tillage〉no tillage〉conventional tillage. The deep tillage treatment also showed the highest grain weight per spike, 1 000-grain weight and yield, while conventional tillage exhibited the lowest values, indicating that deep tillage is most beneficial to improvement of yield and water use efficiency of broomcom millet. [Conclusion] This study provides a scientific basis for water use efficiency of broomcorh millet in its main producing areas.

Research Advance on Influencing Factors of Crop Water Use Efficiency

The research advance on the influencing factors of crop water use effi-ciency （WUE） was reviewed in this paper. Based on the discussion on the conno-tation of crop WUE, the influencing factors of crop WUE, such as crop, environ-ment, chemicals, cultivation measures, cropping systems, etc, were elaborated. A-mong them, the species and varieties of crop, soil and chemicals were discussed in detail.

Suitable Date of Seeding, Planting Density and Water Use Efficiency for Propagation of Stock Seed Potato in Mountainous Region of Southwest Sichuan

[Objective] The experiment was conducted to study suitable date of seed- ing and density of spring potato at the stock breeding base in Ebian County at an elevation of 1 200 to 1 500 m. [Methods] Virus-free Potato ＂Chuanyu 13＂ was used as material to study the effects of date of seeding and density on growing period, germination rate, yield and water use efficiency of spring potato in the field. [Result] With the postponement of date of seeding, the days from sowing to germination shortened, while the germination rate, the number of tubers per plant, the number of middle and small tubers in a group, yield and water use efficiency all increased. Planting density had no effects on the days from sowing to germination and the ger- mination rate, while the number of tubers per ptant, the number of middle and small tubers in a group, yield and water use efficiency increased significantly along with the increasing planting density. [Conclusion] At an elevation of 1 200 m to 1 250 m in Ebian County, the suitable date of seeding for potato was from February 9 to March 1, and the suitable planting density was 12×10^4 plants per hm^2, however, in the optimum planting density has not been found so that it needs further research,

Effects of Different Irrigation Amounts on Water Consumption and Water Use Efficiency of Dripirrigated Celery

This study aimed to investigate the effects of different irrigation amounts on water consumption and water use efficiency of celery under the condition of drip irrigation, so as to provide a scientific basis for high-yielding, high-quality and highefficiency cultivation and water-saving irrigation of greenhouse celery. Total five irrigation amounts were designed, 117.5 （T1）, 160.0 （T2）, 202.5 （T3）, 245.0 （T4） and 287.5 （CK） mm/hm2, and the effects of different irrigation amounts on yield, water consumption and water use efficiency of celery were studied by plot experiment. The results showed that at the soil depth of 0-40 cm, the soil water storages of different treatments ranked as T3＇s〉T4＇s〉CK＇s〉T2＇s〉T1＇s, and the celery water consumptions ranked as CK＇s〉T4＇s〉T3＇s〉T2＇s〉T1＇s. At the same time, the soil water storage in different treatment group declined with the growth of celery, and finally increased at the harvest period. Among different irrigation amounts, the water use effi- ciency and irrigation water use efficiency all ranked as T1＇s〉T2＇s〉T3＇s〉T4＇s〉CK＇s. The water consumption of celery was positively related to irrigation amount （P〈 0.01）, and was negatively related to water use efficiency （P〈0.01） and irrigation water use efficiency （P〈0.05）. When the irrigation amount was below 253 mm/hm2, the celery yield was positively related to irrigation amount （P〈0.01）. There was also a positive correlation between celery output and irrigation amount. Compared with those of CK, the benefit of the T4 treatment group was equal, and the water consumption was reduced by 14.78%. In high-efficiency solar greenhouse, the irrigation amount of drip-irrigated celery is recommended as 245 mm/hm2.

Research on Relationship between Recovery Ability after Drought Stress-rewatering and Water Use Efficiency of Winter Wheat Varieties

The study aims at exploring the possibility of using the recovery ability af- ter drought stress-rewatering at vegetative growth stage as the evaluating index in water use efficiency （WUE） of winter wheat varieties. ＇Jing 411 ＇, ＇Jinmai 47＇ and their 34 near isogenic lines （NILs） were used as test materials. Semi-automatic rainproof shelter and the percolating pools were used for simulating drought treat- ment. After suffering severe drought stress, winter wheat crops were rewatered at early jointing stage. The biomass accumulation after rewatering was determined as recovery ability index. In the meanwhile, plant height in the end of vegetative growth stage was measured, and WUE of varieties/lines was also determined. Thereafter, the differences in recovery ability, plant height and the population WUE, together with the correlation between recovery ability and population WUE were analyzed, respectively. The results showed that there were significant differences in recovery ability among some varieties/lines. The recovery ability was affected by both geno- type and environment, and the interaction existed in these two factors. Significant differences existed in plant height and population WUE among the 34 NILs along with their parents. There was a significantly positive correlation between recovery ability and plant height of varieties/lines. Recovery ability and plant height were very significantly and positively correlated with population yield WUE respectively. The re- sults indicated that recovery ability after drought stress-rewatering could be used as an evaluating index of population WUE under drought condition.

Strategies for Jointly Enhancing Water Use Efficiency and Yield of Crops in the North China Plain

The North China Plain （NCP） is one of the most important agricultural re- gions in China, but it is experiencing a serious water-resource crisis due to exces- sive exploitation of groundwater reserves. Improving water-use efficiency （WUE） of crops is thought to have good potential for conserving groundwater and in maintain- ing high crop production in the region, In this paper, firstly, strategies for improving WUE of crop cultivars in the NCP were discussed. According to studies on key factors affecting cultivar WUE, stomatal conductance, which has large genotypic variability and differs among cultivars in response to drought, is an important physio- logical trait associating closely with the performance of cultivars in WUE and yield. Higher WUE and higher yield may be obtained through strategies of cultivar adop- tion with appropriate stomatal characteristics suitable to different conditions of water availability. Secondly, irrigation scheduling in the North China Plain was further dis- cussed. The irrigation frequency currently employed in this area could be reduced by at least one application （from four to three applications） to obtain higher produc- tion and also higher WUE. Finally, straw mulching and the use of early vigor culti- vats were suggested as two practices that had the potential to be effective in in- creasing crop WUE.

Effects of Different Irrigation Amounts on Physiological Indexes and Water Use Efficiency of Rice at the Jointing-booting Stage

[Objective] This study was conducted to investigate the effects of different irrigation amounts on rice leaf physiology and water use efficiency. [Method] The irrigation test with three different treatments was carried out in the Agrometeo- rological Experimental Station of Nanjing University of Information Science ＆ Technology. [Reset] Under flood irrigation, the rice leaf temperature was lower than wet irrigation by 0.4-0.7 ℃; when the strength of photosynthetically active radiation was in the range of 800-1 800 gmol/（m^2·s）, the average stomatal conductance of rice leaves under flood irrigation was higher than that of the wet irrigation treatment by 0.123-0.183 mol H2O/（m^2·s）, and the leaf water use efficiency was higher than that of the wet irrigation treatment by 0.24 g/kg; after 10：00 every day, the water use efficiency under flood irrigation was always higher than that of the wet irrigation treatment; and compared with the wet irrigation treatment, the rice of the flood irrigation treatments had higher leaf water use efficiency, and final yields were also remarkably improved by 5.89%-13.97%. [Conclusion] This study will provide a practical reference basis for field management.

Effects of Different Tillage Systems on Soil Properties,Root Growth,Grain Yield,and Water Use Efficiency of Winter Wheat (Triticum aestivum L.) in Arid Northwest China

Studies on root development, soil physical properties, grain yield, and water-use efficiency are important for identifying suitable soil management practices for sustainable crop production. A field experiment was conducted from 2006 through 2008 in arid northwestern China to determine the effects of four tillage systems on soil properties, root development, water-use efficiency, and grain yield of winter wheat （Triticum aestivum L.）. The cultivar Fan 13 was grown under four tillage systems：conventional tillage （CT） without wheat stubble, no-tillage without wheat stubble mulching （NT）, no-tillage with wheat stubble standing （NTSS）, and no-tillage with wheat stubble mulching （NTS）. The soil bulk density （BD） under CT system increased gradually from sowing to harvest, but that in NT, NTSS, and NTS systems had little change. Compared to the CT system, the NTSS and NTS systems improved total soil water storage （0-150 cm） by 6.1-9.6 and 10.5- 15.3% before sowing, and by 2.2-8.9 and 13.0-15.1% after harvest, respectively. The NTSS and NTS systems also increased mean dry root weight density （DRWD） as compared to CT system. The NTS system significantly improved water-use efficiency by 17.2-17.5% and crop yield by 15.6-16.8%, and the NTSS system improved that by 7.8-9.6 and 7.0-12.8%, respectively, compared with the CT system. Our results suggested that Chinese farmers should consider adopting conservation tillage practices in arid northwestern China because of benefits to soil bulk density, water storage, root system, and winter wheat yield.

Effect of Nitrogen Management on Yield and Water Use Efficiency of Rainfed Wheat and Maize in Northwest China

A field experiment with four treatments and four replicates in a randomized complete block design was conducted at the Changwu Experimental Station in Changwu County, Shaanxi Province, of Northwest China from 1998 to 2002. The local cropping sequence of wheat, wheat-beans, maize, and wheat over the 4-year period was adopted. A micro-plot study using ^15N-lahelled fertilizer was carried out to determine the fate of applied N fertilizer in the first year. When N fertilizer was applied wheat （years 1, 2 and 4） and maize （year 3） grain yield increased significantly （P 〈 0.05） （〉 30%）, with no significant yield differences in normal rainfall years （Years 1, 2 and 3） for N application at the commonly application rate and at 2/3 of this rate. Grain yield of wheat varied greatly between years, mainly due to variation in annual rainfall. Results of ^15N studies on wheat showed that plants recovered 36.6%-38.4% of the N applied, the N remained in soll （0-40 cm） ranged from 29.2% to 33.6%, and unaccounted-for N was 29.5%-34.2%. The following crop （wheat） recovered 2.1%- 2.8% of the residual N from N applied to the previous wheat crop with recovery generally decreasing in the subsequent three crops （beans, maize and wheat）.

Response of yield,quality,water and nitrogen use efficiency of tomato to different levels of water and nitrogen under drip irrigation in Northwestern China

The objective of this study was to investigate the effects of applying different amounts of water and nitrogen on yield, fruit quality, water use efficiency （WUE）, irrigation water use efficiency （IWUE） and nitrogen use efficiency （NUE） of drip-irrigated greenhouse tomatoes in northwestern China. The plants were irrigated every seven days at various proportions of 20-cm pan evaporation （Ep）. The experiment consisted of three irrigation levels （11, 50% Ep; 12, 75% Ep; and 13, 100% Ep） and three N application levels （N1, 150 kg N ha^-1; N2, 250 kg N ha^-1;and N3, 350 kg N ha^-1）. Tomato yield increased with the amount of applied irrigation water in 12 and then decreased in 13. WUE and IWUE were the highest in Ii. WUE was 16.5% lower in 12 than that in I1, but yield was 26.6% higher in 12 than that in I1. Tomato yield, WUE, and IWUE were significantly higher in N2 than that in N1 and N3. NUIE decreased with increasing N levels but NUE increased with increase the amount of water applied. Increasing both water and N levels increased the foliar net photosynthetic rate. I1 and 12 treatments significantly increased the contents of total soluble solids （TSS）, vitamin C （VC）, lycopene, soluble sugars （SS）, and organic acids （OA） and the sugar：acid ratio in the fruit and decreased the nitrate content. TSS, VC, lycopene, and SS contents were the highest in N2. The harvest index （HI） was the highest in 12N2. 12N2 provided the optimal combination of tomato yield, fruit quality, and WUE. The irrigation and fertilisation regime of 75% Ep and 250 kg N ha^-1 was the best strategy of water and N management for the production of drip-irrigated greenhouse tomato.

Grain yield and water use efficiency of super rice under soil water deficit and alternate wetting and drying irrigation

This study investigated if super rice could better cope with soil water deficit and if it could have better yield performance and water use efficiency （WUE） under alternate wetting and drying （AWD） irrigation than check rice. Two super rice cultivars and two elite check rice cultivars were grown in pots with three soil moisture levels, well watered （WW）, moderate water deficit （MWD） and severe water deficit （SWD）. Two cultivars, each for super rice and check rice, were grown in field with three irrigation regimes, alternate wetting and moderate drying （AWMD）, alternate wetting and severe drying （AWSD） and conventional irrigation （CI）. Compared with that under WW, grain yield was significantly decreased under MWD and SWD treatments, with less reduction for super rice than for check rice. Super rice had higher percentage of productive tillers, deeper root distribution, higher root oxidation activity, and greater aboveground biomass production at mid and late growth stages than check rice, especially under WMD and WSD. Compared with CI,AWMD increased, whereasAWSD decreased grain yield, with more increase or less decrease for super rice than for check rice. Both MWD and SWD treatments and eitherAWMD orAWSD regime significantly increased WUE compared with WW treatment or CI regime, with more increase for super rice than for check rice. The results suggest that super rice has a stronger ability to cope with soil water deficit and holds greater promising to increase both grain yield and WUE by adoption of moderate AWD irrigation.

Moderate wetting and drying increases rice yield and reduces water use, grain arsenic level, and methane emission

To meet the major challenge of increasing rice production to feed a growing population under increasing water scarcity,many water-saving regimes have been introduced in irrigated rice,such as an aerobic rice system,non-flooded mulching cultivation,and alternate wetting and drying(AWD).These regimes could substantially enhance water use efficiency(WUE) by reducing irrigation water.However,such enhancements greatly compromise grain yield.Recent work has shown that moderate AWD,in which photosynthesis is not severely inhibited and plants can rehydrate overnight during the soil drying period,or plants are rewatered at a soil water potential of-10 to-15 k Pa,or midday leaf potential is approximately-0.60 to-0.80 MPa,or the water table is maintained at 10 to 15 cm below the soil surface,could increase not only WUE but also grain yield.Increases in grain yield WUE under moderate AWD are due mainly to reduced redundant vegetative growth;improved canopy structure and root growth;elevated hormonal levels,in particular increases in abscisic acid levels during soil drying and cytokinin levels during rewatering;and enhanced carbon remobilization from vegetative tissues to grain.Moderate AWD could also improve rice quality,including reductions in grain arsenic accumulation,and reduce methane emissions from paddies.Adoption of moderate AWD with an appropriate nitrogen application rate may exert a synergistic effect on grain yield and result in higher WUE and nitrogen use efficiency.Further research is needed to understand root–soil interaction and evaluate the long-term effects of moderate AWD on sustainable agriculture.