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... In heavy clay, compacted, saturated soils, or when subsurface drainage is impeded, an inadequate oxygen concentration in the root zone can negatively affect the biological functioning of plants (Letey, 1961). For avocado trees, root hypoxia or anoxia usually results in reduced stomatal conductance (gs), transpiration (T), net CO2 assimilation (A), root and shoot growth, as well as inhibited leaf expansion, moderate to severe stem and leaf wilting, leaf abscission, and root necrosis Schaffer, 1998;Schaffer and Whiley, 2002). ...
... Water content and physical soil properties such as texture and structure are the factors that most affect soil aeration. The higher the soil water content, the lower the air volume, and greater are the limitations to the aerobic metabolism of the roots (Letey, 1961;Blokhina et al., 2003). Fine textured soils have a greater water retention capacity than coarser textured soils. ...
... Fine textured soils have a greater water retention capacity than coarser textured soils. Therefore, a slight error in the irrigation rate or frequency may lead to continuous anaerobic conditions in the root zone (Letey, 1961;Blokhina et al., 2003). The physical soil characteristics measured in this experiment are summarized in Table 1. ...
Commercial avocado production in Chile has expanded to areas with poorly drained soils presenting low oxygenation over significant periods of time throughout the year. In many of these areas, irrigation management is difficult because plantations are often placed on slopes of hills. Poorly aerated soils combined with irrigation design and management problems can limit avocado fruit production and quality, particularly if hypoxia stress occurs between spring and the beginning of summer. It is well known that avocado trees are very sensitive to waterlogging and the relatively low productivity of this species may be related to root asphyxiation. Therefore, in order to get adequate yield and fruit quality, proper irrigation management and better soil oxygen conditions in avocado orchards are necessary. The objective of this study was to evaluate the effect of the hydrogen peroxide (H 2O 2) injection into the soil as a source of molecular oxygen, on plant water status, net CO 2 assimilation and biomass of avocado trees established in clay loam soil with water content at field capacity. Three-year-old 'Hass' avocado trees were planted outdoors in containers filled with heavy loam clay soil with moisture content kept at field capacity. Plants where divided into 2 treatments, those with H 2O 2 injected into the soil through subsurface drip irrigation and plants in soil with no H 2O 2 added (control). In addition to determining physical soil characteristics, net CO 2 assimilation (A), transpiration (T), stomatal conductance (g s) and shoot and root biomass were determined for plants in each treatment. Injecting H 2O 2 into the soil significantly increased the biomass of the aerial portions of the plant, but had no significant effect on measured A, T or g s. The increased biomass of the aerial portions of plants in treated soil indicates that H 2O 2 injection into heavy loam clay soils may be a useful management tool in poorly aerated soil.
... In heavy clay, compacted, saturated soils, or when subsurface drainage is impeded, an inadequate oxygen concentration in the root zone can negatively affect the biological functioning of plants (Letey, 1961). For avocado trees, root hypoxia or anoxia usually results in reduced stomatal conductance (gs), transpiration (T), net CO2 assimilation (A), root and shoot growth, as well as inhibited leaf expansion, moderate to severe stem and leaf wilting, leaf abscission, and root necrosis Schaffer, 1998;Schaffer and Whiley, 2002). ...
... Water content and physical soil properties such as texture and structure are the factors that most affect soil aeration. The higher the soil water content, the lower the air volume, and greater are the limitations to the aerobic metabolism of the roots (Letey, 1961;Blokhina et al., 2003). Fine textured soils have a greater water retention capacity than coarser textured soils. ...
... Fine textured soils have a greater water retention capacity than coarser textured soils. Therefore, a slight error in the irrigation rate or frequency may lead to continuous anaerobic conditions in the root zone (Letey, 1961;Blokhina et al., 2003). The physical soil characteristics measured in this experiment are summarized in Table 1. ...
In Chile, avocado (Persea americana Mill.) orchards are often located in poorly drained, low-oxygen soils, situation which limits fruit production and quality. The objective of this study was to evaluate the effect of injecting soil with hydrogen peroxide (H2O2) as a source of molecular oxygen, on plant water status, net CO2 assimilation, biomass and anatomy of avocado trees set in clay loam soil with water content maintained at field capacity. Three-year-old 'Hass' avocado trees were planted outdoors in containers filled with heavy loam clay soil with moisture content sustained at field capacity. Plants were divided into two treatments, (a) H2O2 injected into the soil through subsurface drip irrigation and (b) soil with no H2O2 added (control). Stem and root vascular anatomical characteristics were determined for plants in each treatment in addition to physical soil characteristics, net CO2 assimilation (A), transpiration (T), stomatal conductance (gs), stem water potential (SWP), shoot and root biomass, water use efficiency (plant biomass per water applied [WUEb]). Injecting H2O2 into the soil significantly increased the biomass of the aerial portions of the plant and WUEb, but had no significant effect on measured A, T, gs, or SWP. Xylem vessel diameter and xylem/phloem ratio tended to be greater for trees in soil injected with H2O2 than for controls. The increased biomass of the aerial portions of plants in treated soil indicates that injecting H2O2 into heavy loam clay soils may be a useful management tool in poorly aerated soil.
... Measurement of ODR with a platinum electrode shows a high correlation with plant performance (Bryce et al., 1982). Earlier observations (Letey, 1961) revealed that roots could not grow into soil where the ODR is < 0.2 mg cm À2 min À1 . An ODR of between 0.2 and 0.3 mg cm À2 min À1 was associated with moderate growth, and an ODR rate above 0.5 or 0.6 mg cm À2 min À1 gave healthy looking growth (Drew and Stolzy, 1996). ...
... Mechanical methods have been developed for piercing cavities in the soil (Kurtz and Kneebone, 1980), but the benefit is passive rather than active and is not maintained for long, and root injury is common and can predispose crops to root disease. This type of aeration is frequently used for turf grass (Huang and Nesmith, 1990), where the aim is to increase total pore space by piercing through the soil profile, or removing small cores of soil (Letey, 1961). Such aeration improves aeration in soils compacted close to the surface, and as such is less relevant to oVset poor aeration caused by frequent irrigation. ...
... Root respiration increased by 9% and 25% and salt exclusion increased by 6% and 25%, respectively, for cotton and soybean, in response to oxygation of a saline soil (Bhattarai, 2005). Soil aeration even reduced plant accumulation of sodium on soils not particularly high in sodium (Letey, 1961). Oxygation also reduced direct damage of mesophyll cells and of the epidermal cells of root tissues due to salt (Fig. 3). ...
Subsurface drip irrigation (SDI) offers well‐documented potential for improving water use efficiency in irrigated agriculture. However, SDI in common with other forms of irrigation is liable to exclude soil air (and therefore oxygen) around the root zone during and following irrigation events, thus reducing root function and crop performance. When SDI is practiced with oxygation (i.e., aerating the rhizosphere by way of the irrigation stream) it could transform the irrigation industry, for it provides a source of oxygen in a root environment that suffers from temporal hypoxia, and occasionally from anoxia. The oxygen is introduced into the irrigation stream by way of the venturi principle, or with solutions of hydrogen peroxide. Oxygation assures optimal root function, microbial activity, and mineral transformations, and leads to enhanced yield and water use efficiency under hypoxic conditions. It also improves plant performance and yield under irrigated conditions previously considered to be satisfactory for crop growth, and offers scope to offset some of the negative impacts of compaction and salinity, related to poor soil aeration, on crop growth. Representing minimal capital investment and recurrent costs, economic returns appear very favorable, as do associated benefits to the environment, measured as reduced drainage, containment of rising water tables, better nutrient use efficiency, and reduced demand by agriculture for irrigation water.The aeration status of irrigated soils deserves more attention than it has received in the past if we wish to unlock yield potential constrained by soil oxygen limitations and effect the yield increases essential to keeping pace with future food (and fibre) demand.
... Thus, root asphyxiation is a growing concern for avocado growers when trees are planted on these marginal soils. In heavy clay, compacted, saturated soils, or when subsurface drainage is impeded, an inadequate oxygen concentration in the root zone can negatively affect the biological functioning of plants (Letey, 1961). For avocado trees, root hypoxia or anoxia usually results in reduced stomatal conductance (gs), transpiration (T), net CO2 assimilation (A), root and shoot growth, as well as inhibited leaf expansion, moderate to severe stem and leaf wilting, leaf abscission, and root necrosis (Schaffer et al., 1992; Schaffer, 1998; Schaffer and Whiley, 2002). ...
... Water content and physical soil properties such as texture and structure are the factors that most affect soil aeration. The higher the soil water content, the lower the air volume, and greater are the limitations to the aerobic metabolism of the roots (Letey, 1961; Blokhina et al., 2003). Fine textured soils have a greater water retention capacity than coarser textured soils. ...
... Fine textured soils have a greater water retention capacity than coarser textured soils. Therefore, a slight error in the irrigation rate or frequency may lead to continuous anaerobic conditions in the root zone (Letey, 1961; Blokhina et al., 2003). The physical soil characteristics measured in this experiment are summarized inTable 1. ...
In Chile, avocado (Persea americana Mill.) orchards are often located in poorly drained, low-oxygen soils, situation
which limits fruit production and quality. The objective of this study was to evaluate the effect of injecting soil with
hydrogen peroxide (H2O2) as a source of molecular oxygen, on plant water status, net CO2 assimilation, biomass and
anatomy of avocado trees set in clay loam soil with water content maintained at field capacity. Three-year-old ‘Hass’
avocado trees were planted outdoors in containers filled with heavy loam clay soil with moisture content sustained at
field capacity. Plants were divided into two treatments, (a) H2O2 injected into the soil through subsurface drip irrigation
and (b) soil with no H2O2 added (control). Stem and root vascular anatomical characteristics were determined for
plants in each treatment in addition to physical soil characteristics, net CO2 assimilation (A), transpiration (T),
stomatal conductance (gs), stem water potential (SWP), shoot and root biomass, water use efficiency (plant biomass
per water applied [WUEb]). Injecting H2O2 into the soil significantly increased the biomass of the aerial portions
of the plant and WUEb, but had no significant effect on measured A, T, gs, or SWP. Xylem vessel diameter and
xylem/phloem ratio tended to be greater for trees in soil injected with H2O2 than for controls. The increased biomass
of the aerial portions of plants in treated soil indicates that injecting H2O2 into heavy loam clay soils may be a useful
management tool in poorly aerated soil.
... Since it can survive under various abiotic stress than other crops as a C 4 crop; however, excess or deficit soil moisture stress [5,[7][8][9] due to erratic rainfall as well as a heavy soil texture are the most important constraints for the sustainability of maize production in worldwide [10]. Additionally, in clay-rich soils, due to soil compactness, or when sub-surface drainage is impeded, an inadequate oxygen rate in the root zone could adversely impact on the biological functioning of plants including maize [11,12]. Therefore, to ensure adequate yield and grain quality, proper irrigation management is very essential, particularly in clay-rich soils. ...
... Similar results were also identified for maize, where a significant improvement of biomass was found due to HP treatment to soil exhibiting excellent structure and adequate the levels of irrigation [28,29]. Whereas the fine-textured soils have a greater water retention capacity which leads to continuous anaerobic conditions in the root zone [11,29]. . SDI, Sub-surface drip irrigation; SDI Deficit , Deficit irrigation under sub-surface drip irrigation system; SDI Full , Full irrigation under sub-surface drip irrigation system; HP, H 2 O 2 ; SDI Full irrigation (100% FC) + 0 ppm HP with full SDI irrigation; SDI Full irrigation (100% FC) + 250 ppm HP with deficit SDI irrigation; SDI Deficit irrigation (70% FC) + 0 ppm HP, SDI Deficit irrigation (70% FC) + 250 ppm HP and SDI Deficit irrigation (70% FC) + 500 ppm HP Several researchers [12,30] revealed that injecting HP into the soil through irrigation system, significantly increased the water use efficiency, finally growth and development of plants; whereas, plants in low-oxygen soils exhibit a decrease in the xylem/phloem ratio which ultimately alters the physiological process of the plant [12,16,31] found that soil injection HP through SDI system increased the oxygen content in the crop rhizosphere which leads to increase xylem/phloem ratio in plants. ...
Maize being subtropical crop is sensitive to water deficit during the early growth stages; particularly clay-rich soil, due to the compaction of the soil. It is well-documented that potential sub-surface drip irrigation (SDI) (Full irrigation ; SDIFull (100% field capacity (FC)), Deficit irrigation; SDIDeficit (70% FC)) improves water use efficiency, which leads to increased crop productivity; since it has a constraint that SDI excludes soil air around the root-zone during irrigation events, which alter the root function and crop performance. Additionally, in clay-rich soils, the root system of plants generally suffers the limitation of oxygen, particularly the temporal hypoxia, and occasionally from root anoxia; while SDI system accomplishes with the aerating stream of irrigation in the rhizosphere could provide oxygen root environment. The oxygen can be introduced into the irrigation stream of SDI through two ways: the venturi principle, or by using solutions of hydrogen peroxide through the air injection system. Therefore, the application of hydrogen peroxide (H 2 O 2 ; HP) can mitigate the adverse effect of soil compactness and also lead to improving the growth, yield and yield attributes of maize in clay-rich soil. Considering the burning issue, a field study was conducted in consecutive two seasons of 2017 and 2018; where hybrid maize was cultivated as a second crop, to evaluate the effect of liquid-injection of H 2 O 2 (HP) into the irrigation stream of SDI on the performance of maize in a clay-rich soil field of Adana, Turkey. When soil water content decreased in 50% of available water, irrigation was performed. The amount of water applied to reach the soil water content to the field capacity is SDIFull (100% FC) and 70% FC of this water is SDIDeficit (70% FC). In the irrigation program, hydrogen peroxide (HP) was applied at intervals of 7 days on average according to available water with and without HP: SDIFull (100% FC) + 0 ppm HP with full SDI irrigation; SDIFull (100% FC) + 250 ppm HP with deficit SDI irrigation; SDIDeficit (70% FC) + 0 ppm HP, SDIDeficit (70% FC) + 250 ppm HP and SDIDeficit (70% FC) + 500 ppm HP. Deficit irrigation (SDIDeficit (70% FC)) program was started from tasseling stage and continued up to the physiological maturity stage with subsoil drip irrigation. H 2 O 2 was applied 3 times during the growing This work is licensed under a Creative Commons Attribution 4.0 International License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Article ech T Press Science season. Two years' results revealed that the liquid-injection of H 2 O 2 into the irrigation stream of SDI improved the growth and yield-related attributes and grain yield of maize. Based on the obtained results, during the extreme climatic condition in the year 2017, SDIFull (100% FC) + 250 ppm HP was more effective than SDIFull (100% FC) + 0 ppm HP on all traits for relative to full irrigation. While, during the favourable climatic condition in the 2018 season, SDIFull (100% FC) + 250 ppm HP was more effective than full irrigation with SDIFull (100% FC) + 0 ppm HP for the grain yield, grains, and SPAD value. Accordingly, the most effective treatment was SDIFull (100% FC) + 250 ppm HP, as it gave the highest growth and yield-related attributes and grain yield of maize followed by SDIDeficit (70% FC) + 250 ppm HP. Therefore, SDIFull with 250 ppm H 2 O 2 using as liquid-injection may be recommended to mitigate the adverse effect of soil compactness particularly water-deficit stress in clay-rich soil for the sustainability of maize production.
... Lack of oxygen commonly prevails in heavy clay soils and those compacted, saturated or with impeded subsurface drainage (Letley, 1961). The importance of aeration on the functioning of higher plants and effects of limited aeration (Grable, 1966;Armstrong, 1979;Blokhina et al., 2003) and anaerobiosis and its consequences are well studied (Vartapetian & Jackson, 1997;Visser et al., 2003). ...
... Root oxygen supply also plays a crucial role in shoot growth. Increased oxygen enhances K and P uptake (Letley, 1961). ...
Inadequate oxygen concentration in the root zone is a constraint to plant performance particularly in heavy, compacted and/or saline soils. Sub-surface drip irrigation (SDI) offers a means of increasing oxygen to plant roots in such soils, provided irrigation water can be hyper-aerated or oxygenated. Hydrogen peroxide (HP) at the rate of 5 litre ha−1 at the end of each irrigation cycle was injected through SDI tape to a field-grown zucchini (courgette) crop (Cucurbita pepo) on a saturated heavy clay soil in Queensland, Australia. Fruit yield, number and shoot weight increased by 25%, 29% and 24% respectively due to HP treatment compared to the control. Two pot experiments with vegetable soybean (Glycine max) and cotton (Gossypium hirsutum) compared the effectiveness of HP and air injection using a Mazzei air injector (a venturi), throughout the irrigation cycle in raising crop yield in a heavy clay soil kept at saturation or just under field capacity. Fresh pod yield of vegetable soybean increased by 82–96% in aeration treatments compared with the control. The yield increase was associated with more pods per plant and greater mean pod weight. Significantly higher above ground biomass and light interception were evident with aeration, irrespective of soil water treatment. Similarly cotton lint yield increased by 14–28% in aeration treatments compared with the control. The higher lint yield was associated with more squares and bolls per plant which accompanied greater above ground biomass and an increase in root mass, root length and soil respiration. Air injection and HP effected greater water use, but also brought about an enhancement of water use efficiency (WUE) for pod and lint yield, and increased leaf photosynthetic rate in both species but had no effect on transpiration rate and stomatal conductance per unit leaf area. Aeration-induced enhanced root function was arguably responsible for greater fruit set and yield in all three crops, while in vegetable soybean greater canopy cover, radiation interception and total vegetative biomass were responsible for additional yield benefit. Increased aeration of the root zone in heavy clay soils employing either air injection or HP proved beneficial to SDI irrigated crops, irrespective of the soil water conditions, and can add value to grower investments in SDI.
... The negative impacts of salinity are severe when the rhizosphere is exposed to water-logging or hypoxia; root uptake of sodium and chloride ions increase with decreasing O 2 concentration in the rhizosphere (Letey 1961). Oxygation, that is, the supply of air-rich irrigation water, can offset the negative effects of salt in sodic/saline soils. ...
... Soybean and cotton accumulated more Na + and Cl − in the root, leaf and stem with increase in salinity and in soybean Na + accumulation decreased somewhat, as did Cl − , in response to oxygation. Letey (1961) likewise reported a decrease in Na + uptake with aeration of the rhizosphere. Accumulation of Na + in the leaf is species-specific (Storey and Walker 1987); however, most glycophytes maintain a low concentration of sodium in the leaves and excrete on the leaf surface (Rudich and Luchinsky 1986). ...
Impacts of salinity become severe when the soil is deficient in oxygen. Oxygation (using aerated water for subsurface drip irrigation of crop) could minimize the impact of salinity on plants under oxygen-limiting soil environments. Pot experiments were conducted to evaluate the effects of oxygation (12% air volume/volume of water) on vegetable soybean (moderately salt tolerant) and cotton (salt tolerant) in a salinized vertisol at 2, 8, 14, 20 dS/m EC(e). In vegetable soybean, oxygation increased above ground biomass yield and water use efficiency (WUE) by 13% and 22%, respectively, compared with the control. Higher yield with oxygation was accompanied by greater plant height and stem diameter and reduced specific leaf area and leaf Na+ and Cl- concentrations. In cotton, oxygation increased lint yield and WUE by 18% and 16%, respectively, compared with the control, and was accompanied by greater canopy light interception, plant height and stem diameter. Oxygation also led to a greater rate of photosynthesis, higher relative water content in the leaf, reduced crop water stress index and lower leaf water potential. It did not, however, affect leaf Na+ or Cl- concentration. Oxygation invariably increased, whereas salinity reduced the K+ : Na+ ratio in the leaves of both species. Oxygation improved yield and WUE performance of salt tolerant and moderately tolerant crops under saline soil environments, and this may have a significant impact for irrigated agriculture where saline soils pose constraints to crop production.
... Y, por último, la capacidad de incrementar el oxígeno en el agua de riego debido a su generación residual en dicho proceso. Hay evidencias de que la aireación del suelo puede disminuir los efectos de la deficiencia de oxígeno, permitiendo una reducción del daño directo sobre las células del mesófilo y de las células epidérmicas de los tejidos de la raíz sometidos a condiciones salinas (aguas residuales) [11], permitiendo al mismo tiempo, un incremento de la difusión de dióxido de carbono y etileno desde la raíz, un aumento de la exclusión y/o acumulación de sales, así como un incremento de la respiración y crecimiento del sistema radicular [12][13][14]. ...
... Su carácter efímero, hace que deba producirse in situ, para poder utilizarlo en el momento que se precise. En su creación, se deriva además, la producción de oxígeno, el cual podría ser utilizado como una ventaja adicional para los cultivos (Abuarab et al., 2013;Bhattarai et al., 2004;Bhattarai, 2005;Letey, 1961). ...
Durante la campaña 2019-2020, se llevó a cabo un experimento para evaluar el
comportamiento de una instalación de ozonización a pie de parcela cuando se utilizan
aguas de diferente naturaleza (Regenerada y Trasvase) y obtener resultados preliminares
a nivel agronómico y fisiológico de un cultivo de pomelo en estas condiciones. El ensayo se llevó a cabo, en una finca experimental en Campotejar (Murcia), sobre la variedad ´Star
Ruby´, empleando un diseño bifactorial (Tipo de agua y Ozonización), con bloques
completos al azar y 6 repeticiones por combinación. La aplicación de ozono, se realizó entre los meses de junio y agosto mediante una instalación creada exprofeso, y situada a pie de parcela, utilizando un generador de O3 de 20 gr/hora, procurando mantener una dosis constante del mismo (entre 600 y 650 mV en valor redox a pH 6 a la salida de la
instalación). En todos los riegos, durante este periodo, se aplicó el O3 durante todo el tiempo de mismo, menos en la fase de abonado y post-abonado, para evitar posibles efectos indeseables sobre la fertilización. Durante el resto del año, los árboles fueron fertirrigados según criterio del agricultor, utilizando el agua disponible (nunca regenerada). Durante el periodo de estudio, se evaluaron en continuo los valores redox durante todos los eventos de riego, a la entrada y la salida de la instalación, el volumen de agua aplicado, así como algunos parámetros de crecimiento vegetativo y del fruto y estado hídrico del cultivo. Los parámetros de producción y calidad, así como el estado nutricional del cultivo de la campaña, también fueron evaluados. Nuestros resultados denotan que las instalaciones utilizadas para la aplicación de un tratamiento de ozonización a pie de parcela, cuando se utilizan aguas regeneradas, pueden presentar dificultades derivadas de la naturaleza de estas aguas (elevados niveles de materia orgánica y otras sustancias altamente oxidables), lo que hace necesario un estudio más exhaustivo de estos sistemas para poder llevar a cabo un tratamiento eficaz de O3 en estas condiciones. Dimensionar adecuadamente la generación de O3 para cada instalación en función de la naturaleza de las aguas utilizadas e implementar sistemas que garanticen la presurización de la instalación y procuren la dosificación adecuada de medio ácido, pueden ser algunas de las recomendaciones a seguir para este tipo de instalaciones. Por otra parte, la respuesta agronómica y fisiológica, ante estos tratamientos requiere igualmente de un mayor y más largo estudio, para poder alcanzar resultados confiables, dado que en el presente estudio solo se evaluaron los efectos de la aplicación de estos tratamientos durante una etapa muy concreta del desarrollo del fruto.
... In addition, the negative impacts of salinity are severe when the rhizosphere is exposed to hypoxia. The root uptake of Na + and Cl − increases with decreasing O 2 concentration in the rhizosphere [20]. NaCl stress causes greater increases in Na + and Cl − concentrations in the shoots and greater decreases the concentrations of K + [21]. ...
Background:
Salt stress is one of the environmental factors that greatly limits crop production worldwide because high salt concentrations in the soil affect morphological responses and physiological and metabolic processes, including root morphology and photosynthetic characteristics. Soil aeration has been reported to accelerate the growth of plants and increase crop yield. The objective of this study was to examine the effects of 3 NaCl salinity levels (28, 74 and 120 mM) and 3 aeration volume levels (2.3, 4.6 and 7.0 L/pot) versus non-aeration and salinity treatments on the root morphology, photosynthetic characteristics and chlorophyll content of potted tomato plants.
Results:
The results showed that both aeration volume and salinity level affected the root parameters, photosynthetic characteristics and chlorophyll content of potted tomato plants. The total length, surface area and volume of roots increased with the increase in aeration volume under each NaCl stress level. The effect was more marked in the fine roots (especially in ≤1 mm diameter roots). Under each NaCl stress level, the photosynthetic rate and chlorophyll content of tomato significantly increased in response to the aeration treatments. The net photosynthetic rate and chlorophyll a and t content increased by 39.6, 26.9, and 17.9%, respectively, at 7.0 L/pot aeration volume compared with no aeration in the 28 mM NaCl treatment. We also found that aeration could reduce the death rate of potted tomato plants under high salinity stress conditions (120 mM NaCl).
Conclusions:
The results suggest that the negative effect of NaCl stress can be offset by soil aeration. Soil aeration can promote root growth and increase the photosynthetic rate and chlorophyll content, thus promoting plant growth and reducing the plant death rate under NaCl stress conditions.
... Plant-root interactions with nutrient elements are entirely different when the roots are exposed to an oxygen deficient environment compared to an aerated rhizosphere. Reduction in the uptake of Na and Cl by aerated roots compared to roots exposed to hypoxia is one such example (Letey 1961). Reduced uptake of Ca by hypoxic roots leading to tomato cause blossom end rot -a physiological disorder (Bhattarai et al. 2005) and rapid development of carrot cavity spot -a pathological problem in the hypoxic root environment of carrot (Hiltunen and White 2002), are examples of the issue pertinent to multigation. ...
... Lesser root density at 0.9 m in SDI at 105 % ETc and furrow irrigation (Figure 2) was possibly responsible for the deeper loss of irrigation water resulting in deep drainage (Figure 4) under the higher irrigation rate. Drip irrigation, because delivery of unit volume of water is concentrated into a much smaller soil volume than with furrow irrigation (as evidenced by drier soil distant from the drip line but at or just below the depth of the emitter - Figure 3) results in saturated soil leading to low oxygen diffusion rates (Silberbush et al., 1979) below that required for root growth (Letey, 1961). During and after drip irrigation when the oxygen diffusion rate is so low, growth and yield advantages are evident for cotton with the aeration of irrigation water (Bhattarai et al., 2004). ...
The practice and management of subsurface drip irrigation (SDI) on heavy clay soils is poorly understood.
Over-irrigation can lead to excessive runoff and drainage, with associated negative environmental
consequences. Experiments were conducted in 2001/2002 and 2002/2003 on cotton (Gossypium hirsutum)
in a Vertisol in Australia to evaluate the effect of SDI at various application rates on cotton yield and
quality, and the results were compared with those for conventional furrow irrigation. Irrigating with SDI
that supplied 50 % or 75 % of daily crop evapotranspiration (ETc) maintained a dry upper soil profile
throughout the season. SDI at 50 % ETc could potentially capture 250 mm more rain during the season
compared to SDI 90 % ETc, and even more than furrow irrigation. However, supplying only 50 % ETc
with SDI hastened the maturity of the crop by on average 25 days compared with furrow irrigation and
higher SDI rates, fewer bolls were set and yields were lower than in the other treatments. Nevertheless, a
shorter season, if yield sacrifice is acceptable, favours logistics when integrating winter crops with summer
cotton. It also reduces the number and cost of pesticide sprays and irrigation. Yield plateaued when 75 %
or more of daily ETc was supplied by SDI. The two drier treatments (SDI at 50 % and 75 % of ETc)
had consistently higher water use efficiency (WUE) for lint production compared with those of the two
wetter SDI treatments (SDI at 90 % and 105/120 % ETc). All SDI treatments were also more efficient in
the first year in the use of water for lint production than was furrow irrigation, but improved irrigation
management in the form of faster irrigation and reduction of tail water in the second year obviated the
advantage of SDI. Irrigation of cotton with SDI at 75 % ETc offered significant benefits in terms of saved
irrigation water over wetter SDI treatments, resulted in the highest average WUE for lint production over
the two years, and reduced drainage and runoff compared with higher SDI rates and furrow irrigation.
... Long duration irrigation events result in root development concentrated around the emitters and the relatively low hydraulic conductivity mainly in heavy soils retains the saturation in the root zone, resulting in lack of air, which is detrimental to the root functioning and directly influences crop development. Theoretical and experimental approaches [6,7] indicate that aeration of the root zone improves the yield of crops cultivated in both hydroponics and soil. ...
Subsurface drip irrigation as a source that provides the water directly to the root zone develops a saturated wetted front in the rhizosphere, particularly when the irrigation is close to 100% of evapotranspiration. Long duration irrigations collect root development around the drip emitters and relatively low hydraulic conductivity, mainly in heavy soils, lead to preservation of saturation in the root layer, resulting in lack of air, which is detrimental to the function of roots and directly influences crop development. The objective of this study is to examine whether the root zone aeration can improve the distribution of moisture in the soil thereby improving plant performance. For the investigation of this approach, a three-year experimental research was conducted, in a sugar beet crop, irrigated by a subsurface drip irrigation system. A technique for ventilating the root zone was developed, which comprises passing air in the irrigation water throughout the duration of irrigation using a venturi device and air supply under pressure after irrigation through a compressor. The air application (aerogation) affected the soil moisture in the root zone reducing the water content or repelled the water from the proximal environment of the emitter. Regarding the crop yield characteristics, the continuous air application gave a higher yield, although not statistically significant, than the conventional (without air) irrigation and aeration at the end of irrigation.
... It has been observed that in soils with water content maintained near field capacity , stomatal conductance (gs), transpiration (Tr), stem water potential (SWP) and net CO 2 assimilation (A) of avocado were higher in soils with low water-to-air ratios compared to those with high water-to-air ratios, although soil oxygen content never reached hypoxic levels (Gil, 2008). In soils with high clay content that are compacted, saturated or with slow subsurface drainage, an inadequate oxygen concentration in the root zone can negatively affect plant growth and productivity (Letey, 1961). For avocado trees, root hypoxia or anoxia usually results in reductions in gs, Tr, and A, physiological responses that can negatively affect root and shoot growth and leaf expansion (Schaffer and Ploetz, 1989; Schaffer et al., 1992; Schaffer, 1998; Schaffer and Whiley, 2002). ...
In Chile, expansion of avocado production has resulted in many orchards established in marginal soils that are poorly drained and have high soil water-to-air ratios when soil moisture is at field capacity. However, avocado trees are sensitive to poor soil aeration. A study was conducted to determine the effects of different soil water-to-air ratios (W/A) on biomass and nutrient content of avocado trees. Two-year-old avocado trees were grown for 2 seasons in containers in soils, with different W/A, collected from different avocado growing regions of Chile. There were five treatments corresponding to each of the five soils. At field capacity, the two-season average W/A was 1.7, 1.3, 0.6, 0.4 or 0.3 for treatments T1, T2, T3, T4, or T5, respectively. The same amount of fertilizer was applied to each soil. Mineral element concentrations and total mineral element contents in leaves, shoots, wood and roots were determined for each tree in each treatment at the end of the experimental period. Shoot and root fresh and dry weights, leaf area and leaf retention were also determined. Although all treatments showed non-limiting soil oxygen conditions for avocado root growth, trees in soils with lower W/A had greater shoot and root dry weights and longer autumn leaf retention. Macro- and micronutrient concentrations in any plant tissue were not related to soil W/A. However, total tissue contents of N, P, K, Ca, Mg, C, N and B in roots and whole plants were highest in treatments with lower soil W/A. The results indicate that soil W/A significantly affects growth and mineral nutrition of avocado trees and should be considered for avocado site selection and management.
Keywords: mineral nutrition, nutrient uptake, soil aeration, avocado.
... Lesser root density at 0.9 m in SDI at 105 % ETc and furrow irrigation (Figure 2) was possibly responsible for the deeper loss of irrigation water resulting in deep drainage (Figure 4) under the higher irrigation rate. Drip irrigation, because delivery of unit volume of water is concentrated into a much smaller soil volume than with furrow irrigation (as evidenced by drier soil distant from the drip line but at or just below the depth of the emitter - Figure 3) results in saturated soil leading to low oxygen diffusion rates (Silberbush et al., 1979) below that required for root growth (Letey, 1961). During and after drip irrigation when the oxygen diffusion rate is so low, growth and yield advantages are evident for cotton with the aeration of irrigation water (Bhattarai et al., 2004). ...
The practice and management of subsurface drip irrigation (SDI) on heavy clay soils is poorly understood. Over-irrigation can lead to excessive runoff and drainage, with associated negative environmental consequences. Experiments were conducted in 2001/2002 and 2002/2003 on cotton (Gossypium
hirsutum) in a Vertisol in Australia to evaluate the effect of SDI at various application rates on cotton yield and quality, and the results were compared with those for conventional furrow irrigation. Irrigating with SDI that supplied 50% or 75% of daily crop evapotranspiration (ETc) maintained a dry upper soil profile throughout the season. SDI at 50% ETc could potentially capture 250mm more rain during the season compared to SDI 90% ETc, and even more than furrow irrigation. However, supplying only 50% ETc with SDI hastened the maturity of the crop by on average 25 days compared with furrow irrigation and higher SDI rates, fewer bolls were set and yields were lower than in the other treatments. Nevertheless, a shorter season, if yield sacrifice is acceptable, favours logistics when integrating winter crops with summer cotton. It also reduces the number and cost of pesticide sprays and irrigation. Yield plateaued when 75% or more of daily ETc was supplied by SDI. The two drier treatments (SDI at 50% and 75% of ETc) had consistently higher water use efficiencies (WUE) for lint production compared with those of the two wetter SDI treatments (SDI at 90% and 105/120% ETc). All SDI treatments were also more efficient in the first year in the use of water for lint production than was furrow irrigation, but improved irrigation management in the form of faster irrigation and reduction of tail water in the second year obviated the advantage of SDI. Irrigation of cotton with SDI at 75% ETc offered significant benefits in terms of saved irrigation water over wetter SDI treatments, resulted in the highest average WUE for lint production over the two years, and reduced drainage and runoff compared with higher SDI rates and furrow irrigation.
... Plant-root interactions with nutrient elements are entirely different when the roots are exposed to an oxygen deficient environment compared to an aerated rhizosphere. Reduction in the uptake of Na and Cl by aerated roots compared to roots exposed to hypoxia is one such example (Letey 1961). Reduced uptake of Ca by hypoxic roots leading to tomato cause blossom end rot -a physiological disorder (Bhattarai et al. 2005) and rapid development of carrot cavity spot -a pathological problem in the hypoxic root environment of carrot (Hiltunen and White 2002), are examples of the issue pertinent to multigation. ...
The socio-economic pressure for improvements in irrigation efficiencies is increasing due to intense competition for water between agricultural, domestic and industrial users as well as demands for compliance with environmental regulations. Precision irrigation technology involving less irrigation water and uniform application across the field is therefore important. In the context of declining water allocation for irrigation and the variations in weather and drought patterns attributed to global climate change, efficient and precise applications are necessity. Traditional irrigation methods such as furrow, flood and sprinkler are neither efficient nor environmentally benign. Precision irrigation methods such as drip and subsurface drip irrigation are advocated because they are more water use efficient and because they offer a possible approach to meet projected food demand, a doubling by the 2050. In spite of greater water use efficiency afforded by minimal soil surface evaporation and deep drainage, and ease of automation, wide scale adoption of surface and subsurface drip irrigation technology is limited. This is due to their high investment cost for installation. They often lack a significant yield benefit when compared to conventional irrigation practice. Reasons are probably linked to a sustained wetting front around emitters. These emitters impose a condition of low oxygen content in the root-dense rhizosphere surrounding emitters that impede root respiration, and negatively impact on plant uptake of water and nutrients, leading to constrained yield performance.
... Tomato leaf tissues in the current experiment accumulated more Na + at higher salinity and less Na + in response to aeration. Letey (1961) has earlier reported a decrease in Na + uptake with aeration of the rhizosphere. The accumulation of Na + in the leaf of tomato occurs at the expense of K + , Ca 2+ , and Mg 2+ . ...
Water logging and salinity of the soil alter both the physical and biological environment of plant roots. In two experiments, we investigated the effects of imposed aeration on yield and the physiological response of tomato (Lycopersicon esculentum L.) variety Improved Apollo growing under protected conditions over a range of salinities (the salinity experiment), and under constant field capacity (FC) or drier soil conditions (the moisture experiment). Subsurface irrigation with aerated water (12% air in water) stimulated above-ground growth, and enhanced the reproductive performance through earliness for flowering and fruiting compared with the control. Fruit yield of tomato with aeration in the moisture experiment was increased by 21% compared with the control (4.2 kg versus 3.7 kg per plant), and the effect of aeration on fruit yield was greater in FC than in the drier treatment. Fruit yield was increased by 38% in saline soil due to aeration compared with the non-aerated control. Increasing salinity from 2 to 8.8 dS m−1, and 10 dS m−1 reduced fruit yield by 18% and 62%, respectively, but 4 dS m−1 did not suppress yield. Aeration in both the experiments increased plant water use and water use efficiency (WUE), expressed as weight per unit of applied water. Biomass WUE was greater by 16% and 32% in the moisture and salinity experiments, respectively. The increased yield with aeration was also accompanied by an increased harvest index (HI) defined as the proportion of dry fruit biomass to total dry biomass, greater mean fruit weight, high fruit DM, and increase in leaf chlorophyll content and shoot: root ratio, and a reduced water stress index (computed from the difference between air and leaf temperature). The benefit gained from aerating irrigation water was not only observed under conditions where air-filled porosity may be low (e.g., in poorly structure sodic soils, or at field capacity in clay soils), but also in drier soils.
In natural and agroecosystem, plants are continuously exposed to environmental stresses. Besides having evolved several indigenous tolerance mechanisms, proper management of agricultural practices contribute to avert deleterious impact of stressful conditions. Mineral nutrients have irreplaceable role in plant metabolism. Deficiency in any mineral nutrients impedes plant growth, which has direct association with yield potential of the plant. Mineral nutrients participate in the synthesis of essential organic molecules, such as amino acids and proteins, and nutrient imbalance can affect many biological processes. Soil water deficit disturbs mineral nutrient relations, inhibiting plant growth and development, which reflects on the final crop yield. Water deficit normally reduces mass flow-dependent mineral nutrient uptake and the translocation of these nutrients from the roots to the shoot, affecting all metabolic processes of plant physiology. On the other hand, proper supplementation of mineral elements to crop plants can contribute to avoid stress for soil water deficit through their active participation in several defense mechanisms. Global climate changes are expected to increase the occurrence and duration of soil water deficit in arid and semi-arid regions, leading farmers, and governments to face an increasing risk of food security.
In order to diminish environmental stresses of saline water, it is essential to increase soil porosity. One pot experiment with three levels of water salinity (3, 35 and 85 mM NaCl) and two levels of oxygen concentration (Control: about 3.0 mg-L-1; Aeration: 7.0-9.0 mg-L-1) in water was conducted on tomato plants. The results showed that with increased water salinity, plant height, leaf area, biomass and fruit yield were reduced. However, aeration could minimize the impact of salinity, especially at 85 mM water salinity. Leaf water potential was higher under aeration treatment compared to the control. The rates of photosynthesis (Pn) and transpiration (Tr) were elevated by 2.33 umol-m-2-s-1 and 0.69 mmolm -2s-1, respectively, under aeration at 85 mM water salinity, while transpiration efficiency (the ratio of Pn/Tr) was increased by 51.2%. Aeration improved the absorption of K+ and increased the ratio of K+Na+ in the leaf. At 35 mM and 85 mM salinity levels under aeration, the activity of superoxide dismutase in the leaf was up-regulated by 40.8% and 19.2%, the activity of catalase was increased by 38.3% and 61.2%, while the malondialdehyde concentration was reduced by 15.2% and 17.7%, and the electrolyte leakage ratio decreased by 8.9% and 14.7%, respectively. Based on these results, it was concluded that under aeration, the water status and membrane integrity of the plant was improved, with higher antioxidant enzyme activities and greater K+ absorption, which led to a higher salt tolerance, higher Pn and more efficient use of water by the plant.
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