Partial Root-zone Drying Irrigation Research Articles

Partial root-zone drying irrigation improves intrinsic water-use efficiency and maintains high photosynthesis by uncoupling stomatal and mesophyll conductance in cotton leaves.

Partial root-zone drying irrigation (PRD) can improve water-use efficiency (WUE) without reductions in photosynthesis; however, the mechanism by which this is attained is unclear. To amend that, PRD conditions were simulated by polyethylene glycol 6000 in a root-splitting system and the effects of PRD on cotton growth were studied. Results showed that PRD decreased stomatal conductance (gs) but increased mesophyll conductance (gm). Due to the contrasting effects on gs and gm, net photosynthetic rate (AN) remained unaffected, while the enhanced gm/gs ratio facilitated a larger intrinsic WUE. Further analyses indicated that PRD-induced reduction of gs was related to decreased stomatal size and stomatal pore area in adaxial and abaxial surface which was ascribed to lower pore length and width. PRD-induced variation of gm was ascribed to the reduced liquid-phase resistance, due to increases in chloroplast area facing to intercellular airspaces and the ratio of chloroplast surface area to total mesophyll cell area exposed to intercellular airspaces, as well as to decreases in the distance between cell wall and chloroplast, and between adjacent chloroplasts. The above results demonstrate that PRD, through alterations to stomatal and mesophyll structures, decoupled gs and gm responses, which ultimately increased intrinsic WUE and maintained AN.

Biochar addition and reduced irrigation modulates leaf morpho-physiology and biological nitrogen fixation in faba bean-ryegrass intercropping

Intercropping legume with grass has potential to increase biomass and protein yield via biological N2-fixation (BNF) benefits, whereas the joint effects of biochar (BC) coupled with deficit irrigation on intercropping systems remain elusive. A 15N isotope-labelled experiment was implemented to investigate morpho-physiological responses of faba bean-ryegrass intercrops on low- (550 °C, LTBC) or high-temperature BC (800 °C, HTBC) amended sandy-loam soil under full (FI), deficit (DI) and partial root-zone drying irrigation (PRD). LTBC and HTBC significantly reduced intrinsic water-use efficiency (WUE) by 12 and 14 %, and instantaneous WUE by 8 and 16 %, respectively, in faba bean leaves, despite improved photosynthetic (An) and transpiration rate (Tr), and stomatal conductance (gs). Compared to FI, DI and PRD lowered faba bean An, gs and Tr, but enhanced leaf-scale and time-integrated WUE as proxied by the diminished shoots Δ13C. PRD enhanced WUE as lower gs, Tr and guard cell length than DI-plants. Despite higher carbon ([C]) and N concentration ([N]) in faba bean shoots amended by BC, the aboveground C- and N-pool of faba bean were reduced, while these pools increased for ryegrass. The N-use efficiency (NUE) in faba bean shoots was reduced by 9 and 14 % for LTBC and HTBC, respectively, but not for ryegrass. Interestingly, ryegrass shoots had 52 % higher NUE than faba bean shoots. The N derived from atmosphere (% Ndfa) was increased by 2 and 9 % under LTBC and HTBC, respectively, while it decreased slightly by reduced irrigation. Quantity of BNF in faba bean aboveground biomass decreased with HTBC coupled with reduced irrigation, mainly towards decreased biomass and soil N uptake by faba bean. Therefore, HTBC might not be a feasible option to improve WUE and BNF in faba bean-ryegrass intercropping, but PRD is permissible as the clear trade-off between BC and PRD.

Biochar amendment modulates xylem ionic constituents and ABA signaling: its implications in enhancing water-use efficiency of maize (Zea mays L.) under reduced irrigation regimes

While biochar amendment is known to enhance plant productivity and water-use efficiency (WUE), particularly under water-limited conditions, the specific mechanisms driving these benefits remain largely elusive. Thus, the present study was conducted to elucidate the synergistic effects of biochar and reduced irrigation on maize (Zea mays L.) plants, focusing on xylem composition, root-to-shoot signaling, stomatal behavior, and WUE. Maize plants were cultivated in split-root pots filled with clay loam soil, amended by either wheat-straw (WSB) or softwood (SWB) biochar at 2% (w/w). Plants received full (FI), deficit (DI), or alternate partial root-zone drying (PRD) irrigation from the fourth leaf to the grain-filling stage. Our results revealed that WSB amendment significantly enhanced plant water status, biomass accumulation, and WUE under reduced irrigation, particularly when combined with PRD. Although reduced irrigation inhibited photosynthesis, it enhanced WUE by modulating stomatal morphology and conductance. Biochar amendment combined with reduced irrigation significantly increased xylem K+, Ca2+, Mg2+, NO3-, Cl-, PO43-, and SO42- while decreased Na+, which in turn lowered xylem pH. Moreover, biochar amendment and especially WSB amendment further resulted in increased abscisic acid (ABA) contents in both leaf and xylem sap under reduced irrigation conditions due to changes in xylem ionic constituents and pH. The synergistic interactions between xylem components and ABA led to refined adjustments in stomatal size and density, thereby affecting stomatal conductance and ultimately improving WUE of maize plants at different scales. The combined application of WSB and PRD can therefore emerge as a promising approach for improving the overall plant performance of maize plants with increased stomatal adaptations and WUE especially under water-limited conditions.

Optimizing deficit irrigation in Monastrell vines grafted on rootstocks of different vigour under semi-arid conditions

A progressive irrigation reduction was applied during five years (from 2017 to 2021) by using regulated deficit irrigation (RDI) and partial root-zone drying irrigation (PRD) in field-grown mature Monastrell grapevines grafted on five different rootstocks (140Ru, 1103P 41B, 110R, and 161–49C) in the semi-arid wine-growing region of D.O. Bullas, South-Eastern (SE) Spain. The main goal was to adjust the irrigation volume applied during the growing season for each rootstock depending on the drought tolerance/vigour/productivity of the rootstock. Thus, the annual irrigation volume was progressively reduced (from 104 mm year−1 [2017] to 45 mm year−1 [2018‐2019] and 15 mm year−1 [2020‐2021] in the most drought-tolerant, vigorous, and productive rootstocks [1103P, 140Ru], and from 104 mm year−1 [2017] to 74 mm year−1 [2018‐2019] and 58 mm year−1 [2020‐2021] in the less drought-tolerant, vigorous, and productive rootstocks [110R, 161–49C, 41B]. A severe reduction of the irrigation in 140Ru and 1103P substantially reduced vigour, productivity, and berry weight and increased water productivity (WP) (220% and 97%, respectively) and phenolic berry quality (50% and 92%, respectively). Medium/low-vigour rootstocks also had a decrease in vigour, yield, and berry weight in response to an irrigation reduction, enhancing WP (between 17% [41B] and 41% [161‐49C] and phenolic berry quality (between 11% [161–49C] and 46% [110R] With a low water volume DI (53–77 mm year−1), vines grafted on 161–49C delivered the highest berry quality compared to other rootstocks. Physiological changes produced by very low water volume PRD were reflected in a reduced root water and nutrient uptake and leaf gas exchange and a slightly increased technological berry quality compared to RDI. However, PRD did not produce a significant improvement in WP, phenolic concentration, and global berry quality compared to RDI.

Improving mango production using partial root drying technique and organic fertilisation: Field and modeling study

ABSTRACT The decreasing in water availability due to climate change can affect agricultural production. The water shortage problem led to the development of several water saving techniques. One of the waters saving techniques in irrigation is the partial root-zone drying (PRD) method. Tow field experiments accompanied by a modeling study were carried out during seasons 2020/2021 and 2021/2022, respectively, using four deficit irrigation strategies [FI (100% of full irrigation), DI1 (0.75FI), DI2 (0.5FI) where water was supplied to both sides of the mango trees and DI3 (Partial Root-zone Drying, PRD = 0.5FI) where water was supplied to a single side of each tree in an alternating manner)]. The four irrigation methods were designated as the study’s major plots. Then, for the purpose of adding compost, each main plot was divided into four smaller plots [NC (No-Compost), C12 (12 ton ha−1), C18 (18 ton ha−1) and C24 (24 ton ha−1)] to investigate the effects of such treatments on increasing water productivity, yield, and the quality of mango fruits. The results indicated that adding compost with PRD irrigation method decreased water stress throughout the root zone and increased the yield, water productivity and fruit quality. Compost addition C24 (24 ton ha−1) with PRD irrigation increased the amount of soil organic matter and microorganism activity when compared to other treatments. Additionally, C24 treatment improved mango quality under both FI and PRD treatments, the PRD technique enhanced fruit yields by 3.8% and 7.3% and water productivity by 51.6% and 53.8% for 2021 and 2022 seasons, respectively, compared to FI, while reducing the applied irrigation water by 50% for each season. In comparison to other irrigation strategies, the PRD strategy had shown superior outcomes in enhancing the yield, water productivity, and quality of mango yield. With the use of compost “C24” as organic matter fertilizer, PRD proved to be an effective dual technique to save water and increase productivity. Under both current and future water scarcity caused by climate change, it could be a successful adaptation technique. The SALTMED model produced accurate simulations of the soil moisture content, mango production, and water productivity during the two seasons.

Combined application of biochar and partial root-zone drying irrigation improves water relations and water use efficiency of cotton plants under salt stress

Reduced irrigation in combination with biochar application can improve stomatal anatomy, water relations and intrinsic water use efficiency (WUEi), thus having a positive effect on the alleviation of salinity and drought stresses. A split-root pot experiment was executed to explore the effects of two biochar applications (WSP: wheat straw biochar; SWP: soft wood biochar) in combination with three irrigation strategies (FI: full irrigation; DI: deficit irrigation, PRD: partial root-zone drying irrigation) on stomatal anatomy, water relations and WUEi of cotton plants under normal soil (S0, EC=0.36 dS m-1) and saline soil (S1, EC=16.55 dS m-1). The results revealed that both salinity and drought stresses negatively affected plant water relations and reduced stomatal conductance, carbon isotope discrimination (Δ13C), stomatal size (SS) and hydraulic conductance (Kl) while increased leaf abscisic acid (ABA) concentration ([ABA]leaf). However, biochar amendment under salt stress significantly decreased [ABA]leaf while improved leaf water relations, increased Kl, stomatal density (SD), SS, Δ13C and maximum stomatal conductance (gsmax). Meanwhile, compared with FI and DI, PRD plants had greater SD, gsmax, and WUEi but lowered stomatal conductance (gs). Among all treatments, the combined application of WSP and PRD significantly increased SD and gsmax, improved leaf water relations, Kl and [ABA]leaf and WUEi. It is concluded that the altered stomatal features caused by the biochar and irrigation treatments are associated with changes in [ABA]leaf and Kl, and have a major role in affecting plant hydraulic integrity and water use efficiency of cotton exposed to salinity stress.

The effect of alternate partial root-zone drying and deficit irrigation on the yield, quality, and physiochemical parameters of milled rice

While paddy fields produce a high yield, they also require a large amount of water and produce a significant amount of methane. Therefore, the adoption of water-saving irrigation techniques for rice cultivation is critical. Furrowed rice farming may be a viable alternative to paddy rice cultivation. The objective of the present study was to evaluate the impact of alternate partial root-zone drying irrigation on rice yield, milled rice quality, and cooking quality under furrow rice cultivation. A two-year field trial was conducted on a local rice cultivar, Tarom Hashemi, in 2015 and 2016. Seven water regimes, including three levels of regulated deficit irrigation (RDI), three levels of alternate partial root-zone drying irrigation (APRDI), and conventional flooding irrigation (CFI), were used in this study. In RDI and APRDI treatments, plots were irrigated when soil matric potential had reached −0.1 (RDI1 and APRDI1), −0.3 (RDI3 and APRDI3), and −0.6 bar (RDI6 and APRDI6). RDI1 and APRDI1 treatments produced milled rice yield similar to the CFI, while irrigation water productivity (IWP) was significantly higher by 22.9% and 45.7%, respectively. Regardless of the soil water potential, the IWP in APRDI treatments was 16% higher than that of RDI treatments. Severe water stress (RDI6 and APRDI6) caused a marked increase in amylose content and alkali spreading value of milled rice resulting in improved cooking quality. Nitrogen uptake in APRDI treatments was 2% higher than that of RDI treatments. On average, methane emission per milled grain yield declined by 77.9% and 78.7% in RDI and APRDI treatments, respectively. Our data indicate that the expensive and laborious practice of puddling can be avoided to increase water productivity and improve rice quality without sacrificing yield. The results also show that furrow rice cultivation could significantly reduce the methane emission contribution of rice production.

Assessment of Physiological Performance and Yield of Three Olive Cultivars Under Partial Root-Zone Drying Irrigation in a Semi-arid Environment

Assessment of Physiological Performance and Yield of Three Olive Cultivars Under Partial Root-Zone Drying Irrigation in a Semi-arid Environment

Ammonium nitrogen combined with partial root-zone drying enhanced fruit quality of tomato under elevated atmospheric CO2

Increasing nitrogen fertilization and reduced irrigation regimes can alleviate the negative effect of elevated CO2 (e[CO2]) on fruit quality of tomatoes, yet little is known about the effects of N forms combined with partial root-zone drying irrigation (PRI) on tomato growth and fruit quality under e[CO2]. This study aimed to investigate the response of tomato plants to N forms, PRI and their interactions under e[CO2]. Tomato plants (Solanum lycopersicum L.) were grown in split-root pots in climate-controlled growth chambers with CO2 concentration of 400 ppm and 800 ppm, respectively, supplied with two N forms i.e. nitrate nitrogen (NN) and ammonium nitrogen (AN). Three irrigation regimes, i.e. full irrigation (FI), deficit irrigation (DI) and PRI were applied from anthesis to fruit maturity. The results showed that e[CO2] decreased plant water use (WU) while increased biomass accumulation (ΔDW), water use efficiency (WUE) and fruit number (FN). Under e[CO2], AN plants had less ΔDW, leaf area and WU while similar yield, as compared with NN plants. Additionally, under e[CO2] with PRI treatment, AN fruits had greater [N], [K], [N/P], and soluble solid (Brix) to acid ratio, but lower [C/N], [P/K] and acid concentration, and similar fruit [C], [P], [Ca], [Mg] and [S], in comparison with the NN fruits. Collectively, AN treatment combined with PRI under e[CO2] improved fruit mineral nutrition and the flavor of tomato fruits without reduction in yield and WUE. Therefore, AN combined with PRI could be an alternative strategy to improve tomato fruit quality in future drier and CO2-enriched environment.

Biochar amendment combined with partial root-zone drying irrigation alleviates salinity stress and improves root morphology and water use efficiency in cotton plant

An adsorption experiment and a pot experiment were executed in order to explore the mechanisms by which biochar amendment in combination with reduced irrigation affects sodium and potassium uptake, root morphology, water use efficiency, and salinity tolerance of cotton plants. In the adsorption experiment, ten NaCl concentration gradients (0, 50, 100, 150, 200, 250, 300, 350, 400, and 500 mM) were set for testing isotherm adsorption of Na+ by biochar. It was found that the isotherms of Na+ adsorption by wheat straw biochar (WSP) and softwood biochar (SWP) were in accordance with the Langmuir isotherm model, and the Na+ adsorption ability of WSP (55.20 mg g−1) was superior to that of SWP (47.38 mg g−1). The pot experiment consisted three factors, viz., three biochar amendments (no biochar, WSP, and SWP), three irrigation strategies (deficit irrigation, partial root-zone drying irrigation – PRD, full irrigation), and two NaCl concentrations gradients (0 mM and 200 mM). The findings indicated that salinity stress lowered K+ concentration, root length, root surface area, and root volume (RV), but increased Na+ concentration, root average diameter, and root tissue density. However, biochar amendment decreased Na+ concentration, increased K+ concentration, and improved root morphology. In particular, the combination of WSP and PRD increased K+/Na+ ratio, RV, root weight density, root surface area density, water use efficiency, and partial factor productivity under salt stress, which can be a promising strategy to cope with drought and salinity stress in cotton production.

Compost tea supplied by partial root-zone drying irrigation affected growth and productivity of eggplants and cucumbers grown in succession

ABSTRACT Partial root-zone drying irrigation techniques and application of compost tea are practices that, when used separately, have demonstrated beneficial effects on crop productivity in organic farming, with efficient use of natural resources. The aim of this work was to investigate effects of the combination of applying compost tea and using partial root-zone drying irrigation on the growth of eggplants (Solanum melongena L.) and cucumbers (Cucumis sativus L.) grown in succession, on the quantity and quality of the fruits produced, and on soil nutrients after the two growing seasons. The objective was to assess how the two factors, irrigation technique and fertilising method, and the combination of the two, influenced the parameters investigated. Application of compost tea via partial root-zone drying irrigation resulted in well-developed plants and high yields with good quality fruit for both eggplants and cucumbers and did not lead to depletion of soil nutrients, compared with the use commercial organic fertilizers or standard irrigation. Most of the investigated parameters were affected by the interaction of the two factors, though the yield of both crops was more affected by the irrigation technique, while the fertilising approach had a greater effect on the quality of the cucumber fruit. Nevertheless, the combination of compost tea with partial root-zone drying irrigation resulted in competitive performance against the other treatments, whilst reducing the use of resources. The findings showed the effectiveness of applying compost tea by partial root-zone drying irrigation and this was recommended for organic agriculture systems.

Application of water-saving irrigation and biostimulants on the agronomic performance of maize (Zea mays)

Water deficit can limit maize yield; therefore, appropriate choices of irrigation schemes or water-saving irrigation strategies to maximize WUE are needed for sustainable agriculture in response to environmental challenges and climate change. The objectives of our study were to evaluate and compare the effects of regulated deficit irrigation (RDI) and partial root-zone drying irrigation (PRDI) schemes with various field capacity (FC) conditions on yield components, water use efficiency (WUE), photosynthesis capacity, and chlorophyll fluorescence parameters of the maize plant in a pot experiment. Moreover, we also investigated foliar application of glycine betaine (B, 50 mM) and soil-treated chitin (C, 2 g/kg) to plants against water supply limitations and highlighted their potential for the sustainable production of maize. Significantly higher plant height, cob fresh and dry weights, and total dry weight of maize were observed in RDI with the 75 % FC condition compared to the control (full irrigation with 100 % FC). PRDI treatment resulted in significantly higher economic yield, WUEyield, and WUEbiomass compared to RDI treatment. Total water used in PRDI at 50 % FC saved 72 % of water resources compared to the control. Furthermore, values for effective quantum yield (ФPSII), photochemical quenching (qP), and electron transfer rate (ETR) of maize subjected to 75 % FC were higher than under 50 % FC and the control, while maximal quantum efficiency (Fv/Fm) levels of maize were higher under 50 % FC than under 75 % FC. All agronomic traits, chlorophyll content (as SPAD value), transpiration rate, net photosynthesis value, WUEyield, and WUEbiomass of plants subjected to PRD-50 %FC with spraying B alone showed higher values compared to other chemical applications and no chemical treatment. Applying C alone to maize plants under PRDI-50 % FC increased qP and Fv/Fm compared to other chemical treatments. Evaluating water deficits with non-destructive measurements are applicable to large-scale water management of maize plants, thereby enabling scarce water resources to be conserved.

Effect of biochar addition and reduced irrigation regimes on growth, physiology and water use efficiency of cotton plants under salt stress

To alleviate the salinity and drought stresses faced in agricultural production, and to improve crop water use efficiency (WUE) in drought-prone regions, novel management strategies are needed. The combination of biochar amendment and reduced irrigation regimes could mitigate the negative effects of salinity and drought stresses and improve WUE of cotton plants. A split-root pot trial was performed in order to investigate the effects of two biochar amendments [wheat straw pellets biochar (WSP) and soft wood pellets biochar (SWP)] combined with three irrigation schemes [full irrigation (FI), deficit irrigation (DI), and partial root-zone drying irrigation (PRD)] on the growth, physiology and WUE of cotton plants under two salinity levels [0 mM NaCl (S0) and 200 mM NaCl (S1)]. The results showed that salt stress depressed plant growth and physiology, and reduced seed cotton yield and lint yield by 19.33–47.22% and 40.43–58.81%, respectively. However, the biochar amendment alleviated salt stress and increased plant dry biomass allocation ratio by 3.85%–12.54%, 5.07%–14.39% and 9.78%–46.62% in boll, seed cotton and lint cotton under S1, respectively, and also increased lint ginning out turn (GOT), harvest index (HI), WUE at plant and yield level (WUEp and WUEy) by 0.21%–28.69%, 5.07%–14.39%, −0.30%–15.71% and 5.83%–32.44%, respectively. Moreover, WSP was superior to SWP in terms of improving plant growth and yield. PRD showed better growth and physiological effects than DI, especially WUEp and WUEy were 6.88%–13.73% and 9.16%–22.78% greater under PRD than under DI. The combined application of biochar and PRD counteracted the decrease in WUE caused by biochar application alone under S0. Collectively, WSP combined with PRD could be a promising strategy in sustainable cotton production under drought and salinity stress.

Effect of partial root-zone drying irrigation (PRDI) on alfalfa available soil P

ABSTRACT This study focused on alfalfa (Medicago sativa) to investigate the effect of partial root-zone drying irrigation (PRDI) on N-fixing crops available soil P. A three-year field experiment was designed with two irrigation methods and four irrigation volumes. Two irrigation methods consisted of PRDI and conventional furrow irrigation (CFI), and four irrigation volumes were set as 70% ETc (alfalfa water requirement), 85% ETc, 100% ETc and 115% ETc. This study showed that the PRDI had no effect on alfalfa seasonal forage yield but increased alfalfa P uptake. The PRDI decreased the soil available P content and stock but had no effect on the total P content and stock, which demonstrates that effect of PRDI on crop available soil P was different when different P forms were used to estimate crop available soil P. This study also showed that the variation in the coefficient was below 3% between soil P (available or total P) contents and soil P stocks, indicating that soil P contents and stocks were similar when estimating alfalfa available soil P under PRDI conditions. The findings of this study present a pattern of estimating the N-fixing crops available soil P in relation to PRDI.

Biochar amendment alters root morphology of maize plant: Its implications in enhancing nutrient uptake and shoot growth under reduced irrigation regimes.

Biochar amendment provides multiple benefits in enhancing crop productivity and soil nutrient availability. However, whether biochar addition affects root morphology and alters plant nutrient uptake and shoot growth under different irrigation regimes remain largely unknown. A split-root pot experiment with maize (Zea mays L.) was conducted on clay loam soil mixed with 2% (w/w) of wheat-straw (WSP) and softwood (SWP) biochar. The plants were subjected to full (FI), deficit (DI), and alternate partial root-zone drying (PRD) irrigation from the fourth leaf to the grain-filling stage. The results showed that, compared to plants grown in unamended soils, plants grown in the biochar-amended soils possessed greater total root length, area, diameter, volume, tips, forks, crossings, and root length density, which were further amplified by PRD. Despite a negative effect on soil available phosphorus (P) pool, WSP addition improved soil available nitrogen (N), potassium (K), and calcium (Ca) pool and cation exchange capacity under reduced irrigation. Even though biochar negatively affected nutrient concentrations in shoots as exemplified by lowered N, P, K (except leaf), and Ca concentration, it dramatically enhanced plant total N, P, K, Ca uptake, and biomass. Principal component analysis (PCA) revealed that the modified root morphology and increased soil available nutrient pools, and consequently, the higher plant total nutrient uptake might have facilitated the enhanced shoot growth and yield of maize plants in biochar-added soils. Biochar amendment further lowered specific leaf area but increased leaf N concentration per area-to-root N concentration per length ratio. All these effects were evident upon WSP amendment. Moreover, PRD outperformed DI in increasing root area-to-leaf area ratio. Overall, these findings suggest that WSP combined with PRD could be a promising strategy to improve the growth and nutrient uptake of maize plants.

Biomass accumulation and water use efficiency of faba bean-ryegrass intercropping system on sandy soil amended with biochar under reduced irrigation regimes

Intercropping is advantageous for optimizing crop productivity and resources utilization efficiency compared to monocultures. Yet, the effects of water/fertilizer management on crop growth and water use efficiency (WUE) in intercropping systems composed of legumes and non-legumes remain largely elusive. Biochar, as a soil amendment, could increase soil water storage and crop yield, but its interaction with soil water deficit and response of WUE are ambiguous. We investigated the growth, biomass and WUE in faba bean-ryegrass intercropping system amended with 550 ℃-pyrolyzed wheat straw (WSBC) and 800 ℃-pyrolyzed cleaning residues biochar (CRBC) under different irrigation treatments. Compared to the no biochar controls, CRBC decreased aboveground biomass (FDM) and seed yield (FGY) of intercropped faba bean, despite improved soil water-holding capacity, leaf water potential (LWP) and leaf hydraulic conductance (Kl) of faba bean. In contrast, CRBC significantly increased ryegrass aboveground biomass (GDM), although reduced the total aboveground biomass (TDM) and WUE (WUEf+g) of faba bean-ryegrass mixtures. These effects were not evident under WSBC. Compared to full irrigation, deficit (DI) and partial root-zone drying (PRD) irrigation enhanced GDM and WUEf+g, but lowered LWP and Kl, FDM and FGY, and PWU (plant water consumption) and TDM. Despite lower maximum quantum yield of photosystem II, PRD outperformed DI in improving biomass and WUE. The principal component analysis showed that PWU rather than biomass contributed significantly to the enhanced WUEf+g under DI and particularly PRD. Moreover, reduced irrigation regimes limited photosynthetic capacity of faba bean by depressing apparent quantum yield and increasing light compensation point, yet biochar addition did not. It was concluded that biochar produced at high temperatures might not be conducive in improving WUE of faba ban-ryegrass intercropping. Instead, PRD could be a prospective option to offset the adverse effect of biochar on plant under water-scarcity conditions.

Partial root-zone drying irrigation for higher water use efficiency in papaya (Carica papaya L.)

A field experiment to standardize the partial root-zone drying irrigation in papaya (Carica papaya L.) cultivar ‘Red Lady’ indicated that replenishing 70 % of the evaporative demand and changing the irrigation sides once in 12 days stored higher soil moisture (14.6 %) in the root zone. Irrigation meeting 60 % ER found to enhance the photosynthetic rate (13.9µ mol/m2/s) significantly, while shifting the irrigation at 16 days was found to reduce the rate (9.9 µ mol/m2/s). ABA production increased with an increase in the interval between the changing irrigation sides. Vertical growth of roots was significantly higher (67.3 cm) when irrigation was scheduled meeting 60 % pan evaporation with irrigation side changing once in 16 days. Replenishing 60 % of evaporation recorded significantly higher number of fruits (46.1/plant) and further changing the irrigation sides once in 12 days found to yield considerably more papaya fruits (53 /plant) and total yield (32.4 kg/plant) accounting to 100 t/ha. This treatment also recorded substantially higher water use efficiency (100.4 kg/ha.mm), saving 14.3 % water. Further, scheduling irrigation at 60 % ER and changing the irrigation sides at 12 day intervals was found to be more economical with higher gross returns (Rs. 10,00,000), net returns (Rs. 6,09,340) and benefit-cost ratio (2.60).

Partial root-zone drying irrigation improves growth and physiology of tobacco amended with biochar by modulating phytohormonal profile and antioxidant system

Partial root-zone drying irrigation improves growth and physiology of tobacco amended with biochar by modulating phytohormonal profile and antioxidant system

Effect of alternate partial root-zone drying (PRD) on soil nitrogen availability to alfalfa

Available soil N is critical for N fertilizer management in crop production but the effects of alternate partial root-zone drying (PRD) on the dynamics of N and the impact of these effects on perennial crops such as alfalfa (Medicago sativa L.) have not been evaluated. A field experiment was conducted to compare two irrigation modes (PRD and conventional furrow irrigation (CFI)) in combination with four irrigation levels (70% ETc (evapotranspiration), 85% ETc, 100% ETc, and 115% ETc). PRD improved the mineralization of organic matter to increase available N and the NO3−-N/NH4+-N ratio. Thus, it increased N uptake, water productivity and maintained seasonal forage yield. The combination of PRD and irrigation level (100% Etc) produced maximum NO3−-N stock. These results present an evaluation of how PRD influences soil N availability to N-fixing perennial crops.

Assessing the potential of partial root zone drying and mulching for improving the productivity of cotton under arid climate

Water scarcity constrains global cotton production. However, partial root-zone drying (PRD) and mulching can be used as good techniques to save water and enhance crop production, especially in arid regions. This study aimed to evaluate the effects of mulching for water conservation in an arid environment under PRD and to further assess the osmotic adjustment and enzymatic activities for sustainable cotton production. The study was carried out for 2 years in field conditions using mulches (NM = no mulch, BPM = black plastic mulch at 32 kg ha-1, WSM = wheat straw mulch at 3 tons ha-1, CSM = cotton sticks mulch at 10 tons ha-1) and two irrigation levels (FI = full irrigation and PRD (50% less water than FI). High seed cotton yield (SCY) achieved in FI+WSM (4457 and 4248 kg ha-1 in 2017 and 2018, respectively) and even in PRD+WSM followed by BPM>CSM>NM under FI and PRD for both years. The higher SCY and traits observed in FI+WSM and PRD+WSM compared with the others were attributed to the improved water use efficiency and gaseous exchange traits, increased hormone production (ABA), osmolyte accumulation, and enhanced antioxidants to scavenge the excess reactive oxygen. Furthermore, better cotton quality traits were also observed under WSM either with FI or PRD irrigation regimes. Mulches applications found effective to control the weeds in the order as BPM>WSM>CSM. In general, PRD can be used as an effective stratagem to save moisture along with WSM, which ultimately can improve cotton yield in the water-scarce regions under arid climatic regions. It may prove as a good adaptation strategy under current and future water shortage scenarios of climate change.