Alternate Partial Root-zone Irrigation Research Articles

Alternative partial root-zone irrigation enhances leaf flavonoid accumulation and water use efficiency of Ginkgo biloba

Alternative partial root-zone irrigation (APRI) is an irrigation management technique that enhances water use efficiency (WUE) and fruit quality without yield reduction. However, little information is available on the response of plantation forest exposed to APRI. To investigate the effects of APRI on WUE and flavonoid accumulation in leaves of ginkgo (Ginkgo biloba) seedlings, a split-root experiment was conducted with three irrigation modes: APRI, fixed partial root-zone drip irrigation (FD), and whole root-zone drip irrigation (WD). For each irrigation mode, three irrigation quotas were applied: normal water supply (75 % of the field water-holding capacity), mild drought (55 % of field capacity), and severe drought (35 % of field capacity). APRI increased the root:shoot ratio, feeder root biomass, total biomass, WUE, and leaf flavonoid concentration, but decreased transpiration rate under the mild drought condition compared with that under FD and WD. Linear regression analyses showed that leaf flavonoid concentration was significantly and positively correlated with WUE and root:shoot ratio, but was negatively correlated with total biomass of ginkgo seedlings. On the basis of the improvements in yield, WUE, and flavonoid accumulation observed in this study, we recommend applying the APRI mild-drought treatment for water management in ginkgo leaf-producing plantations.

Regulation of nitrogen forms on growth of eggplant under partial root-zone irrigation

Water and nitrogen (N) supply in eggplant (Solanum melongena L.) cropping system is an essential factor for controlling the production level, especially in water-limited areas. Shortage of available water and escalating irrigation costs along with high prices of fertilizers dictate adoption of practices that improve water- and N-use efficiency. This study investigated the effects of different irrigation amounts and modes as well as N forms on yield, photosynthesis and irrigated water-use efficiency (IWUE) of a local eggplant cultivar (Jing Yuan No. 1) under partial root-zone irrigation. Two irrigation treatments were sufficient irrigation (enough water to keep the soil moisture in the top 0–40cm at 90% of field water capacity) and deficit irrigation (60% of the water irrigated in sufficient irrigation treatment was applied). Three irrigation modes were conventional irrigation, alternate partial root-zone irrigation (APRI) and fixed partial root-zone irrigation (FPRI). The N treatments were nitrate-N and ammonium-N forms. Under sufficient irrigation, N forms had little effect on yield, leaf N concentration, IWUE, chlorophyll content, leaf water potential and the distribution of root mass, whereas the total length of root was higher in the irrigated furrow than in the non-irrigated furrow. Under deficit irrigation, eggplant had significantly higher biomass when supplied with nitrate-N than with ammonium-N. In addition, IWUE increased under deficit irrigation, particularly with nitrate-N than ammonium-N. With deficit irrigation, APRI increased eggplant growth, and improved fertilizer and water use efficiency more than FPRI at a given form of N fertilizer. Hence, under deficit irrigation, nitrogen forms had a significant effect on the growth of eggplant under partial root-zone irrigation; APRI as a water-saving irrigation technology could play a vital role in saving water and getting high yields in agricultural production.

不同水氮条件下灌溉方式对玉米干物质量和氮钾利用的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 不同水氮条件下灌溉方式对玉米干物质量和氮钾利用的影响 DOI: 10.5846/stxb201405090921 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金重点项目（U1033004）；国家863计划（2011AA100504） Effect of irrigation method on dry mass and nitrogen and potassium utilization of maize under different water and nitrogen conditions Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:由于作物需水随生育期的变化，分根区交替灌溉（AI）的节水效果也会随生育期而发生变化，探明不同生育期分根区交替灌溉对玉米生长和水分养分利用的影响，以期为分根区交替灌溉的实施和充分发挥其节水节肥效果奠定理论基础。通过盆栽试验，在2种灌水水平（正常灌水和轻度缺水）和2种有机无机氮比例（100%无机氮和70%无机氮+30%有机氮）下，以常规灌溉（CI）为对照，分别研究苗期-灌浆初期、苗期-拔节期以及拔节期-抽雄期进行AI对玉米干物质量、氮钾含量和吸收量以及土壤碱解氮和速效钾含量的影响。结果表明，在轻度缺水和有机无机氮肥配施下，与CI相比，拔节期-抽雄期分根区交替灌溉玉米地上部和总干物质量分别增加29.6%和27.4%，地上部和总N吸收量增加50.7%和50.4%。与单施无机氮肥相比，有机无机氮肥配施会在不同程度上增加地上部和总N吸收量，但是一般降低土壤碱解氮和速效钾含量，这说明在轻度缺水和有机无机N肥配施下，拔节期-抽雄期进行分根区交替灌溉提高玉米总干物质量和N吸收量。 Abstract:Crop water requirement varies with the growth stage, so water-saving effect of alternate partial root zone irrigation (AI) also varies with the growth stage. Understanding the effect of alternate partial root-zone irrigation at different growth stages on maize growth and water and nutrient utilization can provide the theoretical foundation for the implement of alternate partial root zone irrigation and fully exerting its effect of saving water and fertilizer. Taking conventional irrigation (CI) as the control, this study has investigated the effects of AI respectively at seedling- early grain filling, seedling-jointing and jointing-tasselling stages on dry mass, nitrogen and potassium contents and uptakes of maize and available N and K contents in soil using a pot experiment under two irrigation levels (normal irrigation and mild water deficit) and two ratios of inorganic to organic N (100% inorganic N and 70% inorganic N + 30% organic N). Results indicate that under mild water deficit and combined application of organic and inorganic N fertilizer condition, AI at the jointing-tasselling stage increased shoot and total dry masses by 29.6% and 27.4%, and shoot and total N uptakes by 50.7% and 50.4%, respectively, if compared to CI. Combined application of organic and inorganic N increased shoot and total N uptakes to some extent, but generally reduced soil available N and K contents when compared to only inorganic N. Thus alternate partial root-zone irrigation at the jointing-tasselling stage could increase total dry mass and N uptakes under mild water deficit and combined application of organic and inorganic N fertilizer. 参考文献 相似文献 引证文献

不同灌水施肥策略对土壤微生物量碳氮和酶活性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 不同灌水施肥策略对土壤微生物量碳氮和酶活性的影响 DOI: 10.5846/stxb201405090925 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金重点项目（U1033004）；国家863计划（2011AA100504）；中国科学院战略性先导科技专项子课题（XDA05070403） Effect of different irrigation and fertilization strategies on soil microbial biomass carbon and nitrogen and enzyme activity Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:根区局部灌溉形成一个土壤水分分布不均匀的环境，影响了土壤微生物量和酶活性。为探明这种影响，在2种灌水水平（正常灌水和轻度缺水）和2种有机无机N肥配施（单施无机N肥和有机无机N肥配施）下，以常规灌溉（CI）为对照，研究分根区交替灌溉（AI）和固定部分根区灌溉（FI）对土壤微生物量C（MBC）、微生物量N（MBN）和酶活性的影响。与CI相比，AI提高拔节期土壤MBC和抽雄期土壤脲酶活性，但是降低大喇叭口期土壤MBC以及拔节期和抽雄期土壤MBN和拔节期土壤脲酶活性；FI增加抽雄期土壤转化酶活性，但是降低大喇叭口期土壤MBC和可溶性碳（DOC）以及3个时期土壤MBN。与正常灌水相比，AI下轻度亏水增加拔节期和抽雄期土壤DOC，但是降低大喇叭口期土壤MBC和拔节期土壤MBN。与单施无机N肥相比，AI下有机无机N肥配施增加拔节期土壤DOC、MBN和过氧化氢酶活性，而FI下则降低大喇叭口期土壤MBC和转化酶活性。因此，在轻度缺水和有机无机氮配施条件下，分根区交替灌溉可以提高玉米拔节期土壤微生物量碳和可溶性碳。 Abstract:Partial root-zone irrigation creates a heterogeneous soil moisture distribution that may affect soil microbial biomass and enzyme activity. In order to understand such effect, a pot experiment was conducted to investigate the effects of alternate partial root-zone irrigation (AI) and fixed partial root-zone irrigation (FI) on soil microbial biomass C (MBC), microbial biomass N (MBN) and enzyme activity when conventional irrigation (CI) as the control, under two irrigation levels (normal irrigation and mild water deficit) and two ratios of inorganic to organic N (only inorganic N and combined application of inorganic and organic N fertilizers). Compared to CI, AI increased soil MBC at the jointing stages and urease activity at the tasselling stage, but reduced soil MBC at the bell-mouthed stage, MBN at the jointing and tasselling stages and urease activity at the jointing stage. FI enhanced soil invertase activity at the tasselling stage, but reduced soil MBC and dissolved oxidized C (DOC) at the bell-mouthed stage and MBN at the three stages. Compared to normal irrigation, mild water deficit increased soil DOC at the jointing and tasselling stages, but reduced soil MBC at the bell-mouthed stage and MBN at the jointing stages under AI. Compared to only inorganic N, combined application of inorganic and organic N fertilizers increased soil DOC, MBN and catalase activity at the jointing stage under AI, but it reduced soil MBC and invertase activity at the bell-mouthed stage under FI. Therefore, alternate partial root-zone irrigation increased soil microbial biomass C and dissolved C at the jointing stage under mild water deficit and combined application of inorganic and organic N fertilizers. 参考文献 相似文献 引证文献

不同水肥条件下分根区交替灌溉对玉米生理特性和水分利用的影响

不同水肥条件下分根区交替灌溉对玉米生理特性和水分利用的影响

Dynamics of root water uptake and water use efficiency under alternate partial root-zone irrigation

The distribution of root length density of maize in ridge culture under alternate partial root-zone furrow irrigation (APFI) and conventional furrow irrigation (CFI) was investigated, and two-dimensional models of root length density and root uptake were developed to investigate the water use efficiencies under different furrow irrigation modes. Results indicated that APFI increased root depth and horizontal extended distance of maize, as well as water use efficiency (WUE). Values of the mean absolute error (MAE), the root mean square error (RMSE), and the index of agreement (di) between measured and simulated values of root length density of maize under APFI ranged from 0.26 to 0.68, 0.03 to 1.51, and 0.64 to 0.85 cm m−3, respectively; and the coefficient of determination (R2) was greater than 0.80. Values of MAE, RMSE, and di between measured and simulated values of root length density of maize under CFI ranged from 0.01 to 0.26, 0.01 to 0.60, and 0.61 to 0.96 cm m−3, respectively; and R2 was higher than 0.86. Dynamics of root uptake at different sites were simulated using the model of root water uptake. Root growth of maize under furrow irrigation was modeled using the 2D model of root length density with reasonable accuracy. Compared with CFI, water consumption rate of the maize in APFI was lower in key water requirement period, root uptake rate was higher in the end period, and WUE in APFI was higher by 5% than that in CFI.

Effects of Partial Root Zone Irrigation on Leaf Photosynthetic Curves and Chlorophyll Fluorescence Parameters in Naked Oat

The objective of this study was to provide experimental evidence for photosynthetic mechanism under drought stress and practical technique of water-saving irrigation in naked oat(Avena nuda L.).In a pot experiment with instrument to control root zone irrigation and water amount,the effects on relative chlorophyll content(SPAD),photosynthetic curves,and chlorophyll fluorescence parameters were compared among irrigation models of alternative partial root zone irrigation(APRI),fixed partial root zone irrigation(FPRI),and conventional total root zone irrigation(CTRI).Compared to CTRI,partial root zone irrigation,including APRI and FPRI treatments,decreased leaf SPAD,net photosynthetic rate(Pn),and carboxylation efficiency(CE);however,APRI had no obvious effects on reducing initial quantum efficiency(α),maximum photochemical efficiency(Fv/Fm),actual photochemical efficiency of PSII(ФPSII),apparent electron transport rate(ETR),and photochemical quenching coefficient(qP).The leaf SPAD of APRI was significantly enhanced compared to that of FPRI(P0.05),and the maximum net photosynthetic rate(Pmax),α,light saturation point(LSP),light use efficiency(LUE),Ci/Ca,CE,CO2 saturation point(Ci,sat),Fo,Fm,ФPSII,ETR,qP,and NPQ were all higher in APRI than in FPRI.The reduction of Pn in partial root zone irrigation treatments resulted from stomatal factors,and structural damage of photosynthetic system II(PSII) was found in FPRI treatment.Clearly,partial root zone irrigation can improve the tolerance ability of naked oat against drought stress;particularly,APRI has the effect to maintain higher Pn than FPRI.

Effect of New Irrigation Technology on the Physiology and Water Use Efficiency of Potato by Reclaimed Water Irrigation

Agriculture is a big consumer of fresh water in competition with other sectors of the society. The agricultural sector continues to have a negative impact on the ecological status of the environment. The worlds interest in high quality food is increasing. Field experiments were conducted to investigate the effect of subsurface drip irrigation on physiological responses, yield and water use efficiency, Soil nitrogen, Root weight density of potato in the semi-humid region of middle China using subsurface drip irrigation. The experiment used second-stage treated wastewater with and without addition of chloride, and both subsurface drip and furrow irrigations were investigated. Results indicated that the alternate partial root-zone irrigation is a practicable water-saving strategy for potato. The drip with chlorinated and non-chlorinated water improved water use efficiency by 21.48% and 39.1%, respectively, and 44.1% in the furrow irrigation. Partial root zone drying irrigation stimulates potato root growth and enhances root density. The content of the heavy metal in the potato tubers is no more than the National Food Requirements, and it is consistent with National Food Hygiene Stands.

根系分区交替灌溉条件下水肥供应对番茄果实硝酸盐含量的影响

In recent years,the quality and security of vegetables have being increasingly concerned by people and investigated by researchers.However,vegetable quality decline is very common due to excessive irrigation and irrational fertilization.The nitrate content is an important index which is used to evaluate vegetable quality.Although tomatoes have been grown successfully for many years in many parts of the world,there is no accurate formula or recipe on both the amount of irrigation and fertilizer levels to get high quality tomato fruit.Alternate partial root-zone irrigation(APRI) is a new water-saving technique and may improve crop water use efficiency and fertilizer use efficiency.To determine the effects of irrigation amount and fertilizer rates of nitrogen,phosphorus,potassium and manure on the nitrate content in tomato fruits under APRI,the quadratic orthogonal regressive rotation design with five factors was used in pot experiment,in which five rates were set for every experimental factor.A regression model on the amount of irrigation water and fertilizers and the nitrate content in tomato fruits was established.Based on the regression equation,the single,interactive and coupling effects of these five experimental factors on the nitrate content in tomato fruit were analyzed.The results showed that if other factors were zero codes,the nitrate content in tomato decreased firstly and then rose with irrigation water increase,while it showed a reverse trend with N and P fertilizer levels.The nitrate content in tomato increased gradually with manure amount,but it was not affected by K fertilizer level.The interactions on the nitrate content in tomato fruits between P fertilizer and manure levels,N and P fertilizer levels showed positive effects,while the interactions between irrigation amount and K fertilizer or manure level,as well as N and K fertilizer levels were negative effects.The coupling effects between two of these five experimental factors showed that the nitrate content in tomato fruits increased markedly with higher irrigation amount when no manure was applied,while it decreased firstly and then increased with irrigation amount for the other manure and all K fertilizer rates.The nitrate content in tomato decreased with K fertilizer or manure increase when irrigation amount was above the mid level.The nitrate content in tomato increased firstly and then decreased with N fertilizer increase for any P or K fertilizer rate.The nitrate content was less when P fertilizer rate was at the highest than any other level,and it was the lowest when P and N fertilizer rate were at the highest and the lowest,respectively,suggesting that lower N fertilizer and higher P fertilizer rates could decrease the accumulation of nitrate content in tomatoes.Interestingly,the situation was different for K fertilizer.Higher K fertilizer rate could reduce the nitrate content significantly only when the N fertilizer rate was above the mid level.The coupling effects of P fertilizer with manure rates on the nitrate content in tomato fruits indicated that increasing P fertilizer properly and decreasing manure application at the same time could greatly contribute to less nitrate content in tomato fruits.

Evapotranspiration and yield of okra as affected by partial root-zone furrow irrigation

Partial root-zone drying or partial root-zone irrigation is a newly proposed water saving technique which may improve water use efficiency and nutrient uptake by a crop without affecting its yield. A study was conducted to investigate the response of furrow-irrigated okra to partial root zone drying in relation to cropevapotranspiration (ETc), vegetative growth, yield, and nutrient use efficiency in a sandy loam soil. The experiment was conducted during December-March with three furrow irrigation strategies: alternate partial root-zone irrigation (APRI), fixed partial root-zone irrigation (FPRI), and full root-zone irrigation (FRI). Two levels of irrigation: 25% available soil moisture depletion (ASMD) and 50% ASMD were imposed under each furrow treatment. The plant vegetative growth was significantly (P<0.05) higher in FRI, whereas the pod yield was more in APRI. Lower depletion soil water treatment produced higher vegetative growth and yield. However, APRI at 50% ASMD resulted in highest irrigation water use efficiency (IWUE) for pod yield, and FPRI at 25% ASMD resulted in highest IWUE for total biomass. The maximum ETc was observed under FRI, followed by APRI. The crop co-efficient (Kc) values of 0.38, 0.74, 0.98 and 0.49 may be used in initial growth stage, mid growth stage, final growth stage, and maturity stage of okra, respectively, to estimate the volume of irrigation water under APRI. Partial factor productivity for the nutrients (N, P and K) followed the similar trend as pod yield. Root biomass of the crop was more in FPRI, where as total root length was more in APRI. The higher root length with finer roots, in conjunction with better nutrients availability in soil produced the higher nutrients content in leaves and pods of alternate partially irrigated plants. Overall, these results reveal that the application of optimum quantity of water through APRI at 50% ASMD could impose desirable water stress on okra plants, improving their fruit yield and quality, without producing higher vegetative growth.

Effects of alternate partial root-zone irrigation on yield and water use of sticky maize with fertigation

To investigate an efficient mode of water and fertilizer supply, a pot experiment was conducted to study the effects of alternate partial root-zone irrigation on dry mass accumulation, yield and water use of sticky maize with fertigation. Three irrigation methods, i.e. conventional irrigation (CI), alternate partial root-zone irrigation (APRI) and fixed partial root-zone irrigation (FPRI), and three fertilization methods, i.e. 100% of total fertilizer (0.2gN, 0.15gP2O5 and 0.2gK2Okg−1soil) as basal fertilizer (F1), 100% of total fertilizer (0.2gN, 0.15gP2O5 and 0.2gK2Okg−1soil) as basal fertilizer and topdressing with irrigation water (F2), 80% of total fertilizer (0.16gN, 0.12gP2O5 and 0.16gK2Okg−1soil) as basal fertilizer and topdressing with irrigation water (F3), were designed. Results show that compared to CI, APRI decreased more water consumption than total dry mass of sticky maize, thus increased water-use efficiency (WUE) on the basis of total dry mass. Compared to F1, F2 increased dry seed yield of sticky maize under APRI, thus WUE on the basis of dry seed (WUEs) and WUEs per unit fertilizer were also increased. Therefore sticky maize with 100% of total fertilizer as basal fertilizer and topdressing with irrigation water is an efficient mode of water and fertilizer supply under APRI in this study.

Alternate partial root-zone irrigation improves fertilizer-N use efficiency in tomatoes

The objective of this study was to investigate the comparative effects of alternative partial root-zone irrigation (PRI) and deficit irrigation (DI) on fertilizer-N use efficiency in tomato plants under mineral N and organic N fertilizations. The plants were grown in split-root pots in a climate-controlled glasshouse and were subjected to PRI and DI treatments during early fruiting stage. When analyzed across the N fertilizer treatments, PRI treatment led to significantly higher N yield, agronomic N use efficiency (ANUE), and apparent N recovery efficiency (ANRE) as compared with the DI treatment, indicating significantly higher fertilizer-N use efficiency and soil N availability as well as enhanced plant’s N acquisition ability in the PRI treatment. Analysis across the irrigation treatments showed that the mineral N fertilizer treatment (MinN) significantly increased N yield, ANUE and ANRE relative to the organic N fertilizer treatment (OrgN). Compared with DI, the rhizosphere and bulk soil mineral N content in the soil were significantly lowered in the PRI treatment, indicating the enhanced root N uptake efficiency. It is suggested that PRI-enhanced soil water dynamics may have increased soil nitrate mass/diffusive flow to the root surfaces and root N uptake efficiency in the wetting soil and stimulated soil N mineralization and plant N demand, contributing to the improved fertilizer-N use efficiency in the PRI relative to the DI treatment.

Water use Efficiency and Physiological Responses of Oat under Alternate Partial Root-zone Irrigation in the Semiarid Areas of Northeast China

Water use efficiency (WUE) and some crop physiological responses were studied when oat (Avena nuda L.) was applied with alternate partial root-zone irrigation (APRI). A field experiment was carried out with two organic fertilizer levels (e.g. 0 and 240 kg hm-2) and three irrigation levels (i.e. 60, 90 and 120 mm). The irrigation methods included the conventional irrigation (CI) and APRI. Compared with CI, APRI under the moderate water stress reduced water consumption by 9.97-12.46%, and improved WUE by 0-9.09%, but the grain yield was slightly reduced by 2.1-12.76%. APRI under the severe water stress would significantly (P<0.05) reduce the plant height than CI. APRI with organic fertilizer could increase the root shoot ratio by 18.18-45.45% after the grain filling stage. Under the severe water stress APRI significantly reduced the net photosynthetic rate (Pn), and these treatments with organic fertilizer generally had much higher Pn than those without organic fertilizer. Our results indicate that APRI under the moderate water stress improves WUE and root shoot ratio, and slightly reduce grain yield and Pn with applied organic fertilizer.

Effects of partial root-zone irrigation on physiology, fruit yield and quality and water use efficiency of tomato under different calcium levels

Abstract Partial root-zone irrigation (PRI) is an irrigation technique to save irrigation water without much yield reduction. We investigated if the benefits of PRI on physiology, fresh fruit yield, fruit quality and water use efficiency (WUE) of pot-grown tomato could be modified by different calcium (Ca) levels in the greenhouse. Three irrigation methods, i.e. conventional irrigation (CI), alternate partial root-zone irrigation (APRI, alternate watering on both sides of the pot) and fixed partial root-zone irrigation (FPRI, fixed watering on one side of the pot), and five Ca levels in solution, i.e. 0, 0.3, 0.5, 0.8 and 1.0% of Ca supplied as calcium chloride, were designed. Results show that PRI reduced more transpiration rate than photosynthetic rate, which led to higher leaf WUE. APRI enhanced root activity, increased fresh fruit yield of tomato slightly and WUE on fresh yield greatly. APRI increased the contents of VC and soluble sugar in fruits by 12.6 and 4.5% but decreased organic acid content in fruits by 5.3%, so APRI increased the ratio of sugar/acid and improved fruit quality greatly. However, FPRI reduced fresh fruit yield and quality to some extent. Suitable concentration of Ca fertilizer can increase photosynthetic rate, fresh fruit yield, WUE on fresh yield and fruit quality. Thus APRI with suitable concentration of Ca fertilizer is a water-saving, quality-improving and practical irrigation technology. In this study, APRI with 0.8% of Ca supplied as calcium chloride is the best treatment.

Influence of geometric design of alternate partial root-zone subsurface drip irrigation (APRSDI) with brackish water on soil moisture and salinity distribution

Abstract in Undetermined In alternate partial root-zone irrigation (APRI) a significant amount of irrigation water can be saved without considerable yield reduction. In this paper, Hydrus-2D/3D was used to investigate the impact of geometric design of alternate partial root-zone subsurface drip irrigation (APRSDI) with brackish water for growing tomato on soil moisture and salinity distribution. Three inter-plant emitter distances (IPED; 20, 30, and 40 cm), two emitter depths (10 and 20 cm), and three irrigation water salinity levels (0, 1, and 2 dS m-1) were used to implement the proposed simulation scenarios in loamy sand soil during a 40-day simulation period. The simulation results showed that higher soil moisture content was found beneath the plant trunk in case of 20 cm (short IPED) and near the domain border in case of 30 and 40 cm IPED. Short IPED guarantees more water in the maximum root density zone. A deeper wetting front occurred for deep emitter depth, while the wetting front reached the soil surface for shallow emitter depth. Salinity results revealed that as irrigation water salinity increased, the salinity in the top soil increased. In addition, the salinity at the soil surface increased as IPED and emitter depth increased. Higher root water uptake rates were recorded in the case of 20 cm IPED while the emitter depth did not show any considerable effect on root water uptake rates. Moreover, the applied irrigation water was fully consumed by the plant in case of short IPED. Emitter depth and salinity of irrigation water had negligible effect on amount of irrigation water extracted by plant roots and percolated amount below the bottom boundary of the flow domain. Overall, short IPED is recommended in APRSDI with or without brackish irrigation water regardless of the emitter depth. (Less)

Alternate partial root-zone irrigation reduces bundle-sheath cell leakage to CO2 and enhances photosynthetic capacity in maize leaves.

The physiological basis for the advantage of alternate partial root-zone irrigation (PRI) over common deficit irrigation (DI) in improving crop water use efficiency (WUE) remains largely elusive. Here leaf gas exchange characteristics and photosynthetic CO2–response and light–response curves for maize (Zea mays L.) leaves exposed to PRI and DI were analysed under three N-fertilization rates, namely 75, 150, and 300 mg N kg−1 soil. Measurements of net photosynthetic rate (An) and stomatal conductance (gs) showed that, across the three N-fertilization rates, the intrinsic WUE was significantly higher in PRI than in DI leaves. Analysis of the CO2–response curve revealed that both carboxylation efficiency (CE) and the CO2-saturated photosynthetic rate (Asat) were significantly higher in PRI than in DI leaves across the three N-fertilization rates; whereas the N-fertilization rates did not influence the shape of the curves. The enhanced CE and Asat in the PRI leaves was accompanied by significant decreases in carbon isotope discrimination (Δ13C) and bundle-sheath cell leakiness to CO2 (Φ). Analysis of the light–response curve indicated that, across the three N-fertilization rates, the quantum yield (α) and light-saturated gross photosynthetic rate (Amax) were identical for the two irrigation treatments; whilst the convexity (κ) of the curve was significantly greater in PRI than in DI leaves, which coincided with the greater CE and Asat derived from the CO2–response curve at a photosynthetic photon flux density of 1500 μmol m−2 s−1. Collectively, the results suggest that, in comparison with the DI treatment, PRI improves photosynthetic capacity parameters CE, Asat, and κ of maize leaves and that contributes to the greater intrinsic WUE in those plants.

Effects of partial root-zone irrigation on hydraulic conductivity in the soil-root system of maize plants.

Effects of partial root-zone irrigation (PRI) on the hydraulic conductivity in the soil–root system (Lsr) in different root zones were investigated using a pot experiment. Maize plants were raised in split-root containers and irrigated on both halves of the container (conventional irrigation, CI), on one side only (fixed PRI, FPRI), or alternately on one of two sides (alternate PRI, APRI). Results show that crop water consumption was significantly correlated with Lsr in both the whole and irrigated root zones for all three irrigation methods but not with Lsr in the non-irrigated root zone of FPRI. The total Lsr in the irrigated root zone of two PRIs was increased by 49.0–92.0% compared with that in a half root zone of CI, suggesting that PRI has a significant compensatory effect of root water uptake. For CI, the contribution of Lsr in a half root zone to Lsr in the whole root zone was ∼50%. For FPRI, the Lsr in the irrigated root zone was close to that of the whole root zone. As for APRI, the Lsr in the irrigated root zone was greater than that of the non-irrigated root zone. In comparison, the Lsr in the non-irrigated root zone of APRI was much higher than that in the dried zone of FPRI. The Lsr in both the whole and irrigated root zones was linearly correlated with soil moisture in the irrigated root zone for all three irrigation methods. For the two PRI treatments, total water uptake by plants was largely determined by the soil water in the irrigated root zone. Nevertheless, the non-irrigated root zone under APRI also contributed to part of the total crop water uptake, but the continuously non-irrigated root zone under FPRI gradually ceased to contribute to crop water uptake, suggesting that it is the APRI that can make use of all the root system for water uptake, resulting in higher water use efficiency.

Antioxidation responses of maize roots and leaves to partial root-zone irrigation

Abstract Antioxidation responses of maize roots and leaves to water deficit and rewatering under partial root-zone irrigation (PRI) were investigated using a pot system. Plants were cultured using three irrigation methods, i.e. conventional irrigation (CI), alternate PRI (APRI) and fixed PRI (FPRI) with three different water regimes including W1 (70% field capacity, FC), W2 (50% FC) and W3 (35% FC). Compared to CI, root peroxidases (POD) activity was enhanced in the irrigated root zone of FPRI and both root zones of APRI during mild water deficit. After rewatering, POD activity was increased in the dry root zone under FPRI but reduced in the roots under APRI. Roots in the dry zone and leaves under FPRI remained high superoxide dismutase (SOD) activity after rewatering. In contrast, SOD activity decreased in the roots and leaves under CI and APRI. Malondialdehyde (MDA) contents were increased in leaves and two sub-roots under FPRI during water deficit and remained higher after rewatering compared to those under CI and APRI. MDA contents in the tissues under APRI showed similar levels to those under CI. Compared to CI, APRI showed the same biomass production, achieving significantly higher water use efficiency under mild water deficit. The results suggested that plants under APRI experienced less oxidative stress or damage induced by water deficit.

Carbon retention in the soil–plant system under different irrigation regimes

Carbon (C) sequestration through irrigation management is a potential strategy to reduce C emissions from agriculture. Two experiments (Exps. I and II) were conducted to investigate the effects of different irrigation strategies on C retention in the soil–plant system in order to evaluate their environmental impacts. Tomato plants (Lycopersicon esculentum L., var. Cedrico) were grown in split-root pots in a climate-controlled glasshouse and were subjected to full irrigation (FI), deficit irrigation (DI) and alternate partial root-zone irrigation (PRI) at early fruiting stage. In Exp. I, each plant received 2.0 g chemical nitrogen (N), while in Exp. II, 1.6 g chemical N and maize residue containing 0.4 g organic N were applied into the pot. The results showed that, in both experiments, the concentration and the amount of total C in the soil were lower in FI and PRI as compared to DI, presumably due to a greater microbial activity in the two treatments; particularly the PRI induced drying and wetting cycles of the soils may cause an increase of microbial activities and respiration rate, which could lead to more C losses from the soil. However, in both experiments the total C concentration in the PRI plants was the highest as compared with the FI and DI plants, and this was seemingly due to improved plant N nutrition under the PRI treatment. Consequently, the total amount of C retained in the soil–plant system was highest in the FI and was similar, but lower, for the PRI and DI. The different N input in the two experiments might have affected the C retention in the soil and in the plant biomass. Nevertheless, with a same degree of water saving, PRI was superior to DI in terms of enhancing C concentration in the plant biomass, which might have contributed to a better fruit quality in tomatoes as reported by Zegbe et al., 2004, Zegbe et al., 2006.

Alternate partial root-zone irrigation induced dry/wet cycles of soils stimulate N mineralization and improve N nutrition in tomatoes

Given the same amount of irrigation volume, applying alternate partial root-zone irrigation (PRI) has improved crop N nutrition as compared to deficit irrigation (DI), yet the mechanisms underlying this effect remain unknown. Therefore, the objective of this study was to investigate whether PRI induced soil dry/wet cycles facilitate soil organic N mineralization hereby contributing to the improvement of N nutrition in tomatoes. The plants were grown in split-root pots in a climate-controlled glasshouse and were subjected to PRI and DI treatments during early fruiting stage. 15N-labeled maize residues were incorporated into the soils. Results showed that PRI resulted in 25% higher net 15N mineralization than did DI, indicating that the enhanced mineralization of soil organic N alone could account for the 16% increase of N accumulation in the PRI than in the DI plants. The higher net N mineralization under PRI was coincided with an intensified soil microbial activity. In addition, even though soil chloroform fumigation labile carbon (CFL-C, as an index of microbial biomass) was similar for the two irrigation treatments, a significant increase of chloroform fumigation labile nitrogen (CFL-N) was found in the PRI wetting soil. Consequently, the C:N ratio of the chloroform fumigation labile pool was remarkably modified by the PRI treatment, which might indicate physiological changes of soil microbes or changes in labiality of soil organic C and N due to the dry/wet cycles of soils, altering conditions for net N mineralization. Moreover, in both soil compartments PRI caused significantly less extractable organic carbon (EOC) as compared with DI; whilst in the PRI wetting soil significantly higher extractable organic nitrogen (EON) was observed. A low EOC:EON ratio in the PRI wetting soil may indicate an increasing net mineralization of the organic N as a result of microbial metabolism. Conclusively, PRI induced greater microbial activity and higher microbial substrates availability are seemingly responsible for the enhanced net N mineralization and improved N nutrition in tomato plants.