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Agricultural Water Management
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ffects of drip irrigation regimes and basin irrigation on Nagpur mandaringronomical and physiological performance
. Panigrahi ∗, A.K. Srivastava, A.D. Huchcheational Research Centre for Citrus, P.O. Shankar Nagar, Nagpur 440 010, Maharastra, India
r t i c l e i n f o
rticle history:eceived 25 August 2011ccepted 27 November 2011vailable online 21 December 2011
eywords:itrusater management
oil chemical changeseaf nutrient compositioneaf physiologyield parameters
a b s t r a c t
The scarcity of irrigation water is one of the major causes of low productivity and decline of citrus orchards.The present study was planned with a hypothesis that the drip irrigation (DI) could save a substantialamount of water over surface irrigation, besides improving the yield of citrus plants. The experimentwas conducted for 3 seasons during 2006–2009, with ‘Nagpur’ mandarin (Citrus reticulata Blanco) plantsbudded on rough lemon (Citrus Jambhiri Lush) rootstock in central India. The effects of DI and basinirrigation (BI) on soil chemical properties and crop responses were studied. DI was scheduled every-other-day at 40%, 60%, 80% and 100% of the alternate day cumulative evaporation (Ecp) measured inClass-A evaporation pan. DI except irrigation at 40% Ecp proved superior to BI, producing more growthand fruit yield of plants. The higher plant growth was recorded with higher regime of DI. The maximumfruit yield in DI at 80% Ecp, using 29% less irrigation water resulted in 111% improvement in irrigationwater productivity under this treatment over BI. The heavier fruits, with lower acidity and higher totalsoluble solids, were harvested in DI at 80% Ecp compared with BI. The significant variation of soil watercontent at 0–0.2 m depth under DI indicated the confinement of effective root zone of the plants in top0.2 m soil. The maximum rate of net-photosynthesis, stomatal conductance and transpiration in leafswas recorded in DI at 100% Ecp. However, the plants under DI at 80% Ecp exhibited the highest leaf wateruse efficiency. The maximum salinity build-up with highest decrease in pH was observed in 0–0.2 m soilunder DI, whereas the salinity development was prominent in 0.4–0.6 m soil with an increase in pH underBI. The gain in available macronutrients (N, P and K) and loss of micronutrients (Fe, Mn, Cu and Zn) in
soil followed the similar trend of EC. The leaf nutrient (N, P, K, Fe, Mn, Cu and Zn) analysis revealed thatDI produced significantly (P < 0.05) higher concentration of macronutrients in leafs than that with basin-irrigated plants. However, the effect of irrigation on micronutrients in leafs was statistically insignificant.Overall, these results reveal that the application of optimum quantity of water through DI (80% Ecp)could impose desirable water stress on ‘Nagpur’ mandarin plants, improving their yield and fruit quality,without producing the higher vegetative growth.
. Introduction
Availability of irrigation water is the major constraint to croproduction in many parts of the world. The advent of drip irrigationDI) is a significant technological improvement in irrigation system,hich helps to combat water scarcity in agriculture. In recent years,
he adoption of DI gains momentum owing to its positive impact onater saving, productivity and quality of produces in many crops.
Citrus, a high water requiring evergreen perennial fruit crop, isrown in tropical and sub-tropical regions of the world. The sub-ptimum soil water in root zone of the plant during any stage of
its growth drastically reduces the fruit yield (Davies and Albrigo,1994). Irrigation is practiced in all most all citrus groves of the worldto avoid water stress in cropping season. Efficient use of irrigationwater is a prerequisite for successful cultivation of citrus in waterscarcity areas.
Basin is the most common method of irrigation used in perennialfruit crops including citrus, though the use of DI has been increasedin recent years (Fereres et al., 2003). The role of DI in improvingplant growth and fruit yield along with water economy is well rec-ognized in different citrus cultivars grown in various regions ofthe world (Germanà et al., 1992). Irrigation scheduling is vital forimproving the efficiency of DI system, as excessive or sub-optimum
water supply has detrimental effects on yield and fruit quality ofcitrus (Davies and Albrigo, 1994). Various methods have been pro-posed for DI scheduling of citrus based on soil, environmental andplant physiological parameters. Chartzoulakis et al. (1999) reported
hat ‘Bonanza’ orange growth and fruit yield did not differ in −0.01nd −0.05 MPa soil water potential treatments, but were signifi-antly reduced at −1.5 MPa soil water potential. Irrigation basedn pan coefficient that varied from 0.6 to 1.2 by 0.2 incrementsid not show any significant result in relation to yield performancef ‘Washington navel’ orange (Kanber et al., 1996). Abu-Awwad2001) compared the lemon tree performance under different irri-ation regimes: 0.0%, 25%, 50%, 75%, 100% and 150% Class-A panvaporation, and reported that irrigation at 100% evaporation pro-uced the maximum plant growth and highest fruit yield. Velezt al. (2007), measuring maximum daily trunk shrinkage (MDS),oncluded that maintaining MDS ratio (MDS value of any treatmentelative to MDS of fully irrigated plant) at 125% was useful for deficitrrigation scheduling of ‘Clementina de Nules’ orange plant. García-ejero et al. (2010) demonstrated that irrigation at 0.5, 0.65, 0.75nd 1.0 water stress index (ratio of actual volume of water supplyo estimated crop evapotranspiration) did not impact significantlyn tree yield, but rather affected the fruit qualities of ‘Salustiana’range.
‘Nagpur’ mandarin (Citrus reticulata Blanco), a commerciallymportant citrus cultivar, is grown in around 0.2 million hectaresf central India (Singh and Srivastava, 2004). Irrigation is practicedn post rainy season (November–June) for higher productivity ofhe crop. The soil type in citrus orchards of central India is pre-ominantly cracking black clay soils (Vertisols), with 35–60% clayontent (Srivastava et al., 2000). The crop is basically irrigated byasin and/or furrow method using ground water in this region.or last few years, the ground water level has declined alarmingly,reating water shortage in citrus orchards. On the other hand, therea under citrus production is increasing exponentially due to theigher economic return from this crop compared with other cropsGangwar et al., 1997). Farmers are more concerned with increas-ng yield of ‘Nagpur’ mandarin using less water, which could bechieved through adoption of efficient irrigation system like driprrigation in this crop.
The nutritional status of plant is one of the important indicatorsf its health and productivity. Nitrogen is associated with properrowth, flower initiation, and fruit drop, development and qualityf citrus plants (Davies and Albrigo, 1994). Phosphorous is essentialor better root development and proper functioning of cell energyystems, whereas potassium plays a major role in regulating ionicalances in the cell and for developing adequate fruit size and reg-lating peel thickness (Davies and Albrigo, 1994). Micronutrientsuch as iron, manganese, copper and zinc are greatly necessary forroper enzyme functioning and are present in small quantities inhe citrus plant (Singh and Sharma, 2000). Deficiency in any onef the essential nutrients prevents the metabolic activity resultingn reduced vegetative growth and less yield and may ultimatelye responsible for complete decline of the plants. The availabilityf required nutrients in soil plays a major role in nutrients uptakey plants. However, the soil chemical properties (pH, EC, etc.) androp management practices including irrigation plays an importantole in governing the nutrients availability to plants (Amberger,006). Srivastava et al. (1999) reported that the sub-optimum levelf available N, P and micronutrients (Fe, Mn, Cu, and Zn) in soilsith high pH (>7.5), coupled with the higher loss of nutrients from
ffective root zone of plants through leaching under surface irriga-ion causes low nutrients acquisition by mandarin plants in centralndia. Leaf nutrients analysis is an effective tool for monitoring theutritional status of citrus plant (Tucker et al., 1995).
The plant water status regulates many physiological processesncluding leaf physiology, which affects crop productivity in citrus
Gomes et al., 2004). Information on leaf physiological parametersnet-photosynthesis, stomatal conductance and transpiration) inesponse to irrigation offers a better understanding of plant–waterelationship and its effect on crop performance under water deficit
Management 104 (2012) 79– 88
condition (Vu and Yelenosky, 1988). Moreover, this informationcould be used for optimizing irrigation scheduling in citrus.
The studies on nutrients uptake, leaf physiological parameters,plant growth and fruit yield response of mandarin cultivars of cit-rus to drip irrigation in clay soils are very limited worldwide. Withthis background, research was carried out to develop the optimalirrigation schedule in relation to vegetative growth, yield and leafnutrient composition of ‘Nagpur’ mandarin, by comparative evalua-tion of pan evaporation-based DI with conventional basin irrigationmethod under a hot sub-humid tropical climate of central India.
2. Materials and methods
2.1. Experimental site
The field experiment was conducted at the Research Farm ofNational Research Centre for Citrus, Nagpur (latitude 21◦08′45′′ N,longitude 79◦02′15′′ E, 340 m above mean sea level), Maharash-tra state, India. The citrus plant used in the study was ‘Nagpur’mandarin (C. reticulata Blanco) budded on rough lemon (Citrusjambhiri Lush) rootstock. The experiment was started with 5-year-old plant and continued for three consecutive years (2006–2007,2007–2008 and 2008–2009) with the same plantation. The plantspacing was 6 m × 6 m. At the beginning of experiment, the aver-age height, canopy spread diameter, stock girth diameter and sciongirth diameter of the plants were 2.7 m, 2.2 m, 90 mm and 84 mm,respectively.
The texture of experimental soil was clay. Basic soil physicalproperties of different horizons are presented in Table 1. The soilwas alkaline in nature. The cation exchange capacity of the soil was42.8 cmol(p+) kg−1. The important chemical properties of differentsoil layers are presented in Table 2. The irrigation water was freefrom salinity (EC, 0.74 dS m−1) and alkalinity (pH 7.1). The meanconcentrations of Ca2+, Mg2+, Na+, K+, SO4
−2, HCO3−, and Cl− in
irrigation water during irrigation seasons were 1.4, 1.1, 1.2, 0.4,0.6, 0.7, 3.0, and 1.2 mequiv. l−1, respectively. The water level inthe wells situated at 30–50 m distance from the experimental plotwas 12–13 m deep from ground surface. The weather data werecollected at the meteorological observatory of the Research Cen-tre present at about 500 m away from the experimental site. Theclimate is characterized as sub-humid tropical, with hot and drysummers. Mean air temperature varies from 14.1 ◦C in winter to35.7 ◦C in summer. However, the maximum daily temperature insummer seldom rises up to 45 ◦C. The mean daily evaporation lossmeasured in USWB (United State Weather Bureau) Class-A panranges from 2.4 mm in December to as high as 13.2 mm in May.The mean annual rainfall of 810 mm is concentrated mostly (>90%of total rainfall) during July to October. However, in the experimen-tal years, the mean annual rainfall and rainfall during irrigationseason (November–June) were 796 mm and 15 mm, respectively.Mean monthly meteorological parameters during the experimentalyears are presented in Fig. 1.
2.2. Treatments and layout
Five irrigation treatments applied to ‘Nagpur’ mandarin plantswere DI at 40% alternate day cumulative Class-A pan evaporationdata (40% Ecp), DI at 60% Ecp, DI at 80% Ecp, DI at 100% Ecp andbasin irrigation (BI). DI was scheduled every other day. A circularbasin of radius 0.8 m, keeping the plant at the centre was made forbasin irrigation. The peripheral ridge height of the basin was 0.3 m.
The watering period was from early November to end of June ineach year of the experiment. Area of the experimental block was6480 m2 (72 m × 90 m), accommodating 180 mandarin plants in 15rows. Each row contained 12 plants. The experimental design was
P. Panigrahi et al. / Agricultural Water Management 104 (2012) 79– 88 81
Table 1Physical properties of soil (0–0.9 m) at the experimental site.
andomized complete block, with four replicates per treatment. Thentire block was divided into 4 equal size plots (18.0 m × 90.0 m)nd each plot was again divided into 5 sub-plots (18.0 m × 18.0 m).ine plants in three adjacent rows (3 plants in each row) in each
ub-plot were taken as a replicated unit. Three plants present inhe central line of each replicated plot were considered for dataecording, so-called experimental plants.
.3. Irrigation scheduling and crop management practices
DI was imposed through two on-line 4 l h−1 pressure compen-ated emitters per plant, placed at 0.6 m away from plant stem. Theater quantities applied under DI treatments were estimated using
he following formula (Germanà et al., 1992):
id = �
(D2
4
)× Kp × Kc ×
(Ecp − Re
Ei
)(1)
here Vid is the irrigation volume applied in each irrigationl plant−1), D the mean plant canopy spread diameter measured inorth–south and east–west directions (m), Kp the pan factor (0.7),c the crop coefficient (0.7) as suggested by Allen et al. (1998), Ecp
he cumulative Class-A pan evaporation depth for two consecutive
ays (mm), Re the effective rainfall depth for corresponding 2 daysmm) and Ei the irrigation efficiency of drip system (90%). The totalainfall depth during the irrigation seasons was considered as effec-ive rainfall, as drainage (surface runoff + deep percolation) induced
by each rainfall event was negligible within the experimental plots(Panigrahi et al., 2009).
For BI, water was applied at 50% depletion of available soil waterin 0–0.3 m soil layer. Irrigation water quantity required for BI wascomputed using the formula:
Vib = (FC − RSM) × d × �
(D2
4
)× 103 (2)
where Vid is the volume of irrigation water (l), FC the field capacityof soil (%, volume basis), RSM the required soil water content at 50%depletion of available soil water (24.2%, volume basis), d the depthof effective root zone (0.3 m) of 5- to 7-year-old ‘Nagpur’ mandarinplants as observed by Autkar et al. (1988) and D the mean plantcanopy spread diameter measured in north–south and east–westdirections (m). Irrigation was applied to each basin through flexiblehosepipe. The volume of mean daily water applied per plant in var-ious months of the study years under both drip and basin irrigationmethods are presented in Table 3. The quantity of water appliedper plant increased with increase in plant canopy spread diameterfrom 2006–2007 to 2008–2009. The water supply to each irrigationtreatment was regulated by adjusting the operating hours with thehelp of water meters and gate valves provided at the inlet end of
sub-mains.
The recommended dose of fertilizers (600 g N as both ureaand urea-phosphate, 200 g P2O5 as urea-phosphate and 100 gK2O as muriate of potash per plant) was uniformly applied in
g the experimental years (2006–2009).
82 P. Panigrahi et al. / Agricultural Water Management 104 (2012) 79– 88
Table 3Water applied (l plant−1 day−1) for ‘Nagpur’ mandarin plants in different months under various irrigation treatments during 2006–2009.
Year Treatment Months
November December January February March April May June
DI at 40% Ecp 7.9 6.5 12.2 13.4 18.9 25.9 28.2 28.7DI at 60% Ecp 11.8 9.8 18.4 20.0 28.4 38.8 42.4 43.1DI at 80% Ecp 15.7 13.0 24.5 26.7 37.9 51.8 56.5 57.4DI at 100% Ecp 19.6 16.3 30.6 33.4 47.3 64.7 70.6 71.8
4.2
D tive d
aemfd
2
amwidmc0w
01opw1fm
tfimop2e2aaSw
a1a
2.5. Statistical analysis
BI 21.8 17.9 3
I: drip irrigation; BI: basin irrigation, Ecp: Class-A pan evaporation for two consecu
ll treatments (Srivastava and Singh, 1997). Ground floor of thexperimental orchard was kept weed free and the plant protectioneasures against insect pests and diseases were adopted uniformly
or all plants in the experimental block, following the recommen-ations given for ‘Nagpur’ mandarin cultivation in central India.
.4. Measurements and analysis
The volumetric soil water content was monitored twice in week (1 day prior and 1 day after irrigation) using a neutronoisture meter (Troxler Model-4300, USA). The water contentas measured at 0–0.2 m, 0.2–0.4 m, and 0.4–0.6 m soil depths,
nstalling 2 access tubes per plant (3 plants per treatment) at aistance of 0.45 and 0.90 m from the plant stem. The depth wiseean soil water content was calculated. Four number of ceramic
up tensiometers per plant (3 plants per treatment) were placed at.2, 0.4, 0.6 and 0.8 m depths below the soil surface to measure soilater suction.
Soil samples were collected from 0 to 0.2, 0.2 to 0.4 and 0.4 to.6 m soil layers, at the sites located at a distance of 0.5, 0.75 and.0 m from plant stem, at beginning (November) and end (June)f irrigation seasons. One plant basin from each replicated plot (4lants per treatment) was taken for soil sampling. Each soil sampleas analysed for EC (soil:water ratio of 1:2), pH (soil:water ratio of
:2) and available nutrients (N, P, K, Ca, Mg, Fe, Mn, Cu and Zn), byollowing the standard procedures (Tandon, 2005). The depth wise
ean values of EC, pH and available nutrients were calculated.Five to seven months old leaf samples (3rd and 4th leaf from
ip of non-fruiting branches) at a height of 2.0 m from ground sur-ace were collected surrounding the plant canopy at the end ofrrigation seasons and analysed for macronutrients (N, P, K) and
icronutrients (Fe, Mn, Cu, and Zn). The leaf samples were thor-ughly washed and dried at 65 ◦C for 48 h. The dried samples wereowdered homogenously and then digested in tri-acid mixture of
parts HClO4 + 5 parts HNO3 + 1 part H2SO4. Analysis made in acidxtracts of leaves consisted of N by auto-nitrogen analyzer (Model-410, Perkin Elmer Inc., USA), P using vanadomolybdo-phosphoriccid method, K by flame photometry and micronutrients (Fe, Mn, Cund Zn) by atomic absorption spectrophotometer (Model-908, GBCcientific equipment, Australia). The leaf nutrient concentrationsere calculated as dry weight basis of leafs.
The net photosynthesis rate (Pn), stomatal conductance (gs)nd transpiration rate (Tr) of leafs were recorded fortnightly, in
h interval from 9 am to 5 pm on a clear-sky day by CO2 gasnalyser (model-301PS, CID Bio-Science, USA) during irrigation
36.8 52.8 70.1 76.8 80.1
ays.
seasons. Four mature leaves per plant (3rd or 4th leaf from tipof shoot) from exterior canopy position (one leaf in each North,South, East and West direction) and two plants per treatment weretaken for these measurements. Leaf water use efficiency (LWUE)was calculated as Pn divided by Tr of leafs (García-Sánchez et al.,2007).
The plant height (distance from ground surface to top of plantcrown), stem height (distance from ground surface to base of firstbranch on stem), canopy diameter (mean of canopy spread diame-ter measured in north–south and east–west directions), stock girthdiameter (stem diameter measured at 0.1 m above ground surface)and scion girth diameter (stem diameter measured at 0.1 m abovebud union) were recorded annually. Plant canopy volume was esti-mated using the following formula (Obreza, 1991):
Vpc = 0.5233 H (D)2 (3)
where Vpc is the plant canopy volume (m3), H the plant canopyheight (difference between plant height and stem height) in mand D the mean plant canopy spread diameter (north–south andeast–west) in m.
The number and weight of fruits harvested from eachexperimental plant (3 plants from each replicated plot) wererecorded and the mean yield per plant under various treat-ments was calculated. Irrigation water productivity (IWP) wasworked out in terms of fruit yield (kg plant−1) per unit quan-tity of irrigation water applied (m3 plant−1). Five fruits perexperimental plant were taken randomly and their qualityparameters (juice percent, acidity, total soluble solids) were deter-mined.
Juice of fruits was extracted manually using juice extractorand juice percent was estimated on weight basis with respect tofruit weight. The juice acidity was determined by volumetric titra-tion with standardized sodium hydroxide, using phenolphthaleinas an internal indicator (Ranganna, 2001) and total soluble solids(TSS) was measured by digital refractometer (Atago model-PAL1, Japan).
The data generated were subjected to analysis of variance(ANOVA), and separation of means was obtained using Duncanmultiple range test (DMRT), according to the methods describedby Gomez and Gomez (1984).
ater
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ooaictiEeai0biTh(wttiotoacwet(osslts1
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P. Panigrahi et al. / Agricultural W
. Results and discussion
.1. Soil water variation
Fig. 2 shows the mean monthly volumetric water contentsbserved in 0–0.2, 0.2–0.4 and 0.4–0.6 m soil layers under vari-us irrigation treatments. All the DI treatments except irrigationt 40% Ecp resulted in significantly (P < 0.05) higher water contentn 0–0.2 m (26.1–29.1%) and 0.2–0.4 m (26.8–29.3%) soil layers inomparison to that under BI (25.7–27.2% and 26.5–28.4%, respec-ively). The soil water content at both 0–0.2 and 0.2–0.4 m depthsncreased with increasing irrigation regime from 40% Ecp to 100%cp. Moreover, the water content in 0–0.2 m and 0.2–0.4 m soil lay-rs increased invariably in all irrigation treatments during Januarynd February, due to some unseasonal rainfall of 11.5–20.0 mmn these months. The difference in daily soil water fluctuation at–0.40 m soil between any two irrigation events was estimated toe higher under BI (1.2–6.4 mm) than that under DI (0.8–4.8 mm),
ndicating higher evapotranspiration (ET) of basin-irrigated plants.he higher ET of basin-irrigated plants was probably due to theigher leaf transpiration rate caused by increased soil water content28.7–29.2%) in root zone up to 2–3 days after irrigation, coupledith higher evaporation from larger wetted surface area under
his irrigation method. Likewise, the range of soil water deple-ion at 0.2 m depth between any two irrigations increased withncreasing irrigation regime with DI. This indicated the higher ETf drip-irrigated plants under high regime of irrigation. However,he magnitudes of soil water fluctuation in 0–0.2 soil layer wasbserved to be significantly (P < 0.05) higher than that in 0.2–0.4nd 0.4–0.6 m soil layers with DI. The higher fluctuation of waterontent in top 0.2 m soil under DI was due to the maximum plantater uptake from this soil layer, indicating the confinement of
ffective root zone of mandarin plants in this soil. Our observa-ion marginally differs from the earlier observation of Autkar et al.1988), which concluded that the effective root zone of 5- to 7-year-ld basin-irrigated ‘Nagpur’ mandarin plants exists in top 0.30 moil. The shallow rooting system of drip-irrigated plants in ourtudy might be caused due to higher soil water content in upperayer (0–0.20 m) under frequent water application (alternate day)hrough drip. The similar result of development of shallow rootingystem under DI was earlier reported in sweet orange (Kanber et al.,996).
The soil water content at 0.4–0.6 m depth under DI decreasedrrespective of irrigation regime. However, BI showed an increasingrend of soil water content at 0.4–0.6 m depth, in spite of the irriga-ion application for top 0.30 m soil layer in this treatment. This wasue to the percolation of irrigation water from top 0.30 m soil, prob-bly caused by transport of water through preferential pathwayscracks and fissures) developed in this shrinking and swelling typelay soil at low soil water content (50% available soil water) underI. Moreover, the increase in soil water content at 0.4–0.6 m depthnder BI was relatively higher during April to June than Novembero March, indicating the higher percolation under higher quantumf water application during summer months (April–June).
.2. Changes in EC and pH of soil
The electrical conductivity (EC) of soil (0–0.2, 0.2–0.4 and.4–0.6 m depth) at the end of irrigation season was observed toe higher by 0.01–0.71 dS m−1 over that at beginning of irrigationTable 4). Under DI, the maximum salinity build-up was observedn top 0.2 m soil. This happened due to the higher evaporation rate
rom wetted surface area, coupled with lower leaching of solublealts from this soil layer with low water application rate under DIAbu-Awwad, 2001). The higher salt accumulation in surface soilnder DI had also been documented earlier in avocado (Gustafson
Management 104 (2012) 79– 88 83
et al., 1979) and pistachio (Butt and Isbell, 2005). However, at theend of irrigation season, the salinity development in 0–0.6 m soillayer under DI (0.77–1.01 dS m−1) was within the salinity tolerancelimit of ‘Nagpur’ mandarin plants (1.3 dS m−1), as reported by Ramet al. (1993). In basin-irrigated plots, the EC value increased up to0.04 dS m−1 at 0–0.4 m soil, whereas at 0.4–0.6 m soil, EC reducedby 0.71 dS m−1. The reduction of salinity in top 0.4 m soil under BIwas attributed to higher leaching of soluble salts from this soil layerby flooding of irrigation water in the plant basin under this treat-ment. The substantial losses of soluble salts from top soil layer oforchards causing lower soil EC under surface irrigation was earlierreported by Myhre et al. (1991) in ‘Valencia’ orange. On the otherhand, the highest increase in EC value at 0.4–0.6 m soil under BIreflects the accumulation of salts in sub-soil layer under this irri-gation method. At the end of rainy season (November), the salinitylevel of soil reduced to initial values (0.64–0.83 dS m−1), indicat-ing that the monsoonal rainfall (700–800 mm) takes place in thisregion is sufficient to leach out the accumulated salts from soil.
The pH values of drip-irrigated soil at 0–0.2, 0.2–0.4 and0.4–0.6 m depths decreased by 0.3–0.8, 0.1–0.4 and 0.1–0.2 units,respectively, at the end of irrigation season over that at the begin-ning of irrigation (Table 4). The lowering of soil pH can probably beattributed to acidic conditions in the soil induced by ammonium-based fertilizers (urea and urea-phosphate) applied to citrus plantsin our study. The chemistry behind soil acidity under application ofammonium-based fertilizers is that during nitrification of ammo-nium (NH4
+) to nitrate (NO3−) in the presence of soil microbes, two
H+ ions get released in soil, which is acidic in nature (Eq. (4)).
NH+4 + 2 O2 → NO−
3 + H2O + 2 H+ (4)
The lower acidity of soil caused by application of ammonium-basedfertilizer was earlier observed by He et al. (1999) in citrus. ThepH value in top 0.2 m soil under BI showed a similar trend as DI.However, the magnitude of decrease in pH of basin-irrigated soil at0–0.2 m was lower (0.3 units) than that of drip-irrigated soil. Thelower acidification of 0–0.2 m soil under BI in comparison to dripirrigation probably reflects the higher loss of ammonium-basedfertilizers from soil surface to atmosphere through denitrificationand ammonia volatilization under BI. The pH value in 0.2–0.4 and0.4–0.6 m soil layers was observed to increase by 0.1 and 0.4 unitsunder BI. Similar findings of increase in pH with concomitantincrease in salinity in sub-soil layers under surface irrigation (flood-ing) was earlier reported by Myhre et al. (1991) in citrus. However,the pH of different soil layers followed the similar trend of EC, atthe end of rainy season.
3.3. Changes in available nutrients in soil
The changes in available macronutrients (N, P and K) at 0–0.20,0.20–0.40 and 0.40–0.60 m soil depths under various irrigationtreatments show that the nutritional status of top 0.20 m soilimproved (Table 5). This happened due to the application ofNPK-based fertilizers to the plants during irrigation season. Themagnitudes of incremental N, P and K in 0–0.20 m soil layer wasmarginally higher in drip-irrigated plots (15.0–32.5, 0.5–2.1 and9.9–21.0 mg kg−1, respectively) compared to that in basin-irrigatedplots (9.0, 0.3 and 9.7 mg kg−1, respectively). The increase in N, Pand K showed a decreasing trend with soil depth under DI, whereasthe reverse trend was observed under BI. The better availability ofplant nutrients in 0.20 m upper soil under DI was probably facili-tated by optimum soil–water and low soil pH, coupled with lowernutrients leaching from this soil layer under this irrigation method
compared with BI. Moreover, the increase in nutrients contentsat both 0–0.2 m and 0.2–0.4 m soils was higher at higher level ofDI. The higher nutrients availability in effective root zone of theplants under DI indicated a greater efficacy of fertilizer application
84 P. Panigrahi et al. / Agricultural Water Management 104 (2012) 79– 88
Fig. 2. Mean soil water content in 0–0.2 m (a), 0.2–0.4 m (b), 0.4–0.6 m (c) soil depths under various irrigation treatments in ‘Nagpur’ mandarin during 2006–2009. Thevertical bar at each data point represents the standard error of mean.
Table 4Changes in EC and pH of soil in different soil layers of ‘Nagpur’ mandarin orchard under various irrigation treatments.*
Soil depth (m) Treatments
+DI at 40% Ecp DI at 60% Ecp DI at 80% Ecp DI at 100% Ecp BI
* Mean of 2006–2007, 2007–2008 and 2008–2009.+ DI: drip irrigation; BI: basin irrigation.# Plus sign (+) indicates gain and minus sign (−) indicates loss in EC and pH of soil.z Data within a row followed by same letters do not differ significantly at P < 0.05.
P. Panigrahi et al. / Agricultural Water Management 104 (2012) 79– 88 85
Table 5Changes in available macronutrients (N, P and K) in different soil layers of ‘Nagpur’ mandarin orchard under various irrigation treatments.*
Soil depth (m) Treatments
+DI at 40% Ecp DI at 60% Ecp DI at 80% Ecp DI at 100% Ecp BI
* Mean of 2006–2007, 2007–2008 and 2008–2009.+ DI: drip irrigation; BI: basin irrigation.#
.
ttgs7acs
Cmmfuclsodtlt
3
ih(NbewDit(coopi4mM
Plus sign (+) indicates gain in available-N, P, and K in soil.z Data within a row followed by same letters do not differ significantly at P < 0.05
hrough this irrigation system, and suggests some further studieso optimize the fertilizer doses for drip-irrigated mandarin plantsrown in central India. However, the N, P and K contents in 0.4–0.6oil under BI were observed to be higher by 12.1–13.1, 1.0–1.1 and.6–10.6 mg kg−1, respectively, over that under DI. This was prob-bly due to higher deposition of leached out nutrients than theombination of plant use and losses (leaching, denitrification) ofuch nutrients from this soil layer under BI.
The magnitudes of available micronutrients (Fe, Cu, Zn, Mn andu) in different soil layers decreased, irrespective of irrigation treat-ents (Table 6). The highest decrease in concentration of availableicronutrients at top 0.4 m soil was observed with DI at 100% Ecp,
ollowed by DI at 80% Ecp. The higher loss of micronutrients in soilnder DI at 100% Ecp in comparison to other treatments might beaused due to higher plant uptake of these nutrients induced byower soil pH under this treatment in this alkaline soil. The con-istent decrease of micronutrients in soil suggests the applicationf appropriate quantity of micronutrients-based fertilizers to man-arin plants. As the changes of micronutrients concentration withinhe soil layers did not show any significant variation under BI, theeaching of such nutrients is not highly expected during the irriga-ion seasons.
.4. Leaf nutrient composition
Nutrient composition of leafs showed a differential response torrigation treatments (Table 7). All the DI regimes produced theigher concentrations of N (1.92–2.37%), P (0.095–0.152%) and K1.58–1.98%) in leafs over that with basin-irrigated plants (1.73%, 0.092% P and 1.49% K). The higher leaf-N, P and K was causedy higher plant uptake with increased availability of such nutri-nts in soil under DI. The concentrations of leaf nutrients increasedith increase in irrigation regime from 40% Ecp to 100% Ecp withI. However, the amount of N, P and K in leafs was adequate
n all the DI treatments, when compared to the foliar diagnos-ic chart developed for optimum ‘Nagpur’ mandarin productivity1.70–2.81% N, 0.09–0.15% P and 1.02–2.59% K) in central Indiaondition (Srivastava and Singh, 2008). This reflects some scopef curtailment of NPK-based fertilizer doses applied under DIver that recommended for surface-irrigated ‘Nagpur’ mandarinlants. The concentration of micronutrients (Fe, Mn, Cu and Zn)
n leafs was observed higher under DI (Fe, 99.1–108.1 ppm; Mn,8.2–57.3 ppm; Cu, 8.7–13.1 ppm; Zn, 10.3–14.2 ppm), with maxi-um value at DI at 100% Ecp, in comparison to BI (Fe, 98.4 ppm;n, 46.3 ppm; Cu, 8.2 ppm; Zn, 9.9 ppm). However, the effect
of irrigation treatments on micronutrient composition in leafswas statistically insignificant (P > 0.05), possibly due to the sub-optimum availability and lower solubility of these nutrients insoil–water continuum. Overall, in all irrigation treatments exceptDI at 80% Ecp, the leaf micronutrient (Mn, Cu and Zn) content wasless than their threshold values (54.8–84.6 ppm Mn, 9.8–17.6 ppmCu and 13.6–29.6 ppm Zn) required for optimum productivity of‘Nagpur’ mandarin (Srivastava and Singh, 2008).
3.5. Leaf physiological parameters
The mean values of net photosynthesis rate (Pn), stomatal con-ductance (gs) and transpiration rate (Tr) of leafs were significantlyinfluenced by irrigation treatments (Table 8). The Pn value washigher at higher level of irrigation under drip, indicating the neg-ative effect of soil water deficit on Pn of citrus plants (Tomar andSingh, 1986; Vu and Yelenosky, 1988). Moreover, the highest reduc-tion in Pn value was calculated in between DI at 80% Ecp and 60%Ecp (0.68 �mol m−2 s−1), followed by that in between DI at 60%Ecp and 40% Ecp (0.47 �mol m−2 s−1). The higher reduction of Pn
in between 80% and 60% Ecp irrigation treatments indicated theexistence of threshold limit of soil water deficit with DI at 80%Ecp, resulting in optimum Pn of mandarin plants under this treat-ment. The basin-irrigated plants exhibited a marginally higherPn value (2.03 �mol m−2 s−1) than the plants with DI at 60% Ecp
(2.45 �mol m−2 s−1). However, the difference in Pn values betweenDI at 40% Ecp and BI was insignificant (P > 0.05).
The gs and Tr values decreased with decreasing irrigation regimefrom 100% Ecp to 40% Ecp with DI. The highest values of gs and Tr
in DI at 100% Ecp attributed to higher soil water content in rootzone of plants under this treatment. However, the highest per centreduction in gs and Tr was observed in between 100% Ecp and 80%Ecp, whereas, the Pn reduced to higher extent in between 80% Ecp
and 60% Ecp. The maximum reduction in gs and Tr at higher irri-gation level compared to Pn reflects the higher sensitivity of theformer parameters to soil water deficit than the later one. More-over, the reduction of gs (12.5–17.4%) was comparatively higherthan that of Tr (7.7–16.2%), with corresponding irrigation regimes.The lower reduction of Tr could be probably due to the contributionof residual or mesophyll conductance (movement of water throughintercellular spaces and mesophyll cells of leafs) to transpiration of
leafs (Davies and Albrigo, 1994). Leaf transpiration depends on totalconductance (stomatal conductance + mesophyll conductance) ofleaf. As water stress occurs, the stomatal closure restricts the entryof both CO2 and water fluxes from surrounding atmosphere to
86 P. Panigrahi et al. / Agricultural Water Management 104 (2012) 79– 88
Table 6Changes in available micronutrients (Fe, Mn, Cu and Zn) in different soil layers of ‘Nagpur’ mandarin orchard under various irrigation treatments.*
Soil depth (m) Treatments
+DI at 40% Ecp DI at 60% Ecp DI at 80% Ecp DI at 100% Ecp BI
* Mean of 2006–2007, 2007–2008 and 2008–2009.+ DI: drip irrigation; BI: basin irrigation.# Minus sign (−) indicates loss of micronutrients in soil.z Data within a row followed by same letters do not differ significantly at P < 0.05.
Table 7Mean leaf nutrients composition of ‘Nagpur’ mandarin under various irrigation treatments.*
DI at 60% Ecp 2.08b 0.098c 1.73c 102.5a 52.3a 10.1a 12.7a
DI at 80% Ecp 2.35c 0.141d 1.97d 106.4a 55.6a 12.7a 13.9a
DI at 100% Ecp 2.37d 0.152ab 1.98d 108.1a 57.3a 13.1a 14.2a
BI 1.73a 0.092a 1.49a 98.4a 46.3a 8.2a 9.9a
* Mean of 2006–2007, 2007–2008 and 2008–2009.
0.05.
lrv8
fig1ehvTEYS
TNt
+ DI: drip irrigation; BI: basin irrigation.z Data within a column followed by same letters do not differ significantly at P <
eaf, but mesophyll conductance remains same and transpirationeduces disproportionately to stomatal conductance. The gs and Tr
alues of basin-irrigated plants exists in between that with DI at0% Ecp and DI at 100% Ecp.
The magnitude of leaf water use efficiency (LWUE, �mol CO2xed per mmol H2O transpired) increased with increase in irri-ation regime from 40% Ecp to 80% Ecp, and then decreased at00% Ecp with DI. However, the LWUE value in DI at 100% Ecp
xisted in between that in DI at 40% Ecp and DI at 60% Ecp. Theigher LWUE in DI at 80% Ecp is due to the marginal decrease in Pn
alue (0.22 �mol m−2 s−1) associated with the higher decrease inr value (0.42 mmol m−2 s−1) under this treatment over DI at 100%
cp. These results are in concurrence with the findings of Vu andelenosky (1988) in Valencia orange and Ribeiro et al. (2009) inatsuma mandarin.
able 8et photosynthesis rate (Pn), stomatal conductance (gs), transpiration rate (Tr), and le
reatments.*
Treatments Pn (�mol m−2 s−1) gs (mmo
+DI at 40% Ecp 1.98az 36.45a
DI at 60% Ecp 2.45b 41.65b
DI at 80% Ecp 3.13c 48.95c
DI at 100% Ecp 3.35c 59.25ab
BI 2.03a 55.45d
* Mean of 2006–2007, 2007–2008 and 2008–2009.+ DI: drip irrigation; BI: basin irrigation.z Data within a column followed by same letters do not differ significantly at P < 0.05.
3.6. Plant growth response
The annual increase in vegetative growth parameters was sig-nificantly affected by irrigation treatments (Table 9). The mean ofincremental height (0.51–0.62 m), stock girth (42–51 mm), sciongirth (40–49 mm) and canopy volume (0.681–1.231 m3) of theplants registered under DI except irrigation at 40% Ecp was sig-nificantly higher (P < 0.05) than that with basin-irrigated plants(plant height, 0.46 m; stock girth, 40 mm; scion girth, 38 mm andcanopy volume, 0.627 m3). The lower growth performance of man-darin plants under DI at 40% Ecp over BI was due to higher plantwater stress caused by lower soil water availability in root zone
under the former treatment (350–410 mm m−1 soil depth) thanthe later one (510–660 mm m−1 soil depth). All the growth char-acteristics increased with increasing irrigation level with DI. The
af water use efficiency (LWUE) of ‘Nagpur’ mandarin under different irrigation
l m−2 s−1) Tr (mmol m−2 s−1) LWUE
1.67a 1.18b
1.81a 1.35c
2.16b 1.44c
2.58c 1.29c
2.21d 0.91a
P. Panigrahi et al. / Agricultural Water Management 104 (2012) 79– 88 87
Table 9Annual incremental plant growth parameters of ‘Nagpur’ mandarin under various irrigation treatments.*
+ DI: drip irrigation; BI: basin irrigation.z Data within a column followed by same letters do not differ significantly at P < 0
igher increase in plant growth parameters with higher irrigationegimes is attributed to more quantity of photosynthate formed byncreased rates of net-photosynthesis in leafs under these treat-
ents.
.7. Yield parameters and irrigation water productivity
Table 10 shows the numbers of fruits per plant, average fruiteight and fruit yield produced in various irrigation treatments.
he maximum number of fruits (242 plant−1) was harvested inI at 100% Ecp, followed by DI at 80% Ecp (235 plant−1). However,
he heavier fruits were recorded with DI at 80% Ecp (148 g fruit−1)han DI at 100% Ecp (136 g fruit−1). The increased number of fruitsith DI at 100% Ecp could be a reason for smaller fruits in this
reatment. Both fruit number per plant and mean fruit weightecreased with decreasing irrigation regime from 80% Ecp to 40%cp with DI. The basin-irrigated plants produced marginally higherumber of fruits with higher weight as compared to DI at 40%cp.
The highest fruit yield was recorded in DI at 80% Ecp
34.78 kg plant−1), followed by DI at 100% Ecp (32.91 kg plant−1).he possible reasons for higher fruit yield under DI at 80% Ecp maye that the water deficit (15–20% available soil water depletion) inoot zone under this treatment suppressed the vegetative growth ofhe plants without bringing much effect on leaf photosynthesis ratend the citrus plants invested higher quantity of photosynthatesowards reproductive growth (fruiting) than vegetative growth.he fruit yield decreased with decreasing irrigation level from 80%cp to 40% Ecp, resulting from less number of fruits with lower fruiteight under lower regime of DI. However, the yield obtained fromI at 40% Ecp (15.07 kg plant−1) was significantly (P < 0.05) lower
han that with basin-irrigated plants (23.18 kg plant−1). This coulde caused by lower photosynthesis rate of leaves under contin-ous soil water deficit prevailed under DI at 40% Ecp comparedo BI. The similar results of lower fruit yield with higher level ofeficit irrigation were earlier reported by Pérez-Pérez et al. (2008)
n ‘Lane late’ orange and García-Tejero et al. (2010) in ‘Salustiana’range.
The mean annual quantities of water applied under differentrrigation treatments indicate that the water consumed under DI at
able 10nnual fruit yield, water productivity and fruit quality of ‘Nagpur’ mandarin as affected b
Treatment Yield parameters
No. of fruits plant−1 Average fruit weight (g) Fruit yield (kg plant
DI at 40% Ecp 110az 137a 15.07a
DI at 60% Ecp 172c 142b 24.42b
DI at 80% Ecp 235d 148b 34.78c
DI at 100% Ecp 242d 136a 32.91c
BI 168b 138a 23.18b
* Mean data during 2006–2009; IWU: irrigation water used; IWP: irrigation water prod+ TSS: total soluble solids; DI: drip irrigation; BI: basin irrigation.z Data within a column followed by same letters do not differ significantly at P < 0.05.
80% Ecp (6.965 m3 plant−1) was 29% lower than BI (Table 10). Earlierstudies also demonstrated the reduction of water consumption upto 30% in lemon grown in central Tajikistan (Tashbekov et al., 1986),30–40% in ‘Verna’ lemon in Spain (Sánchez Blanco et al., 1989) and15% in ‘Salustiana’ orange in Spain (Castel et al., 1989) under DI overconventional BI method. These variations are due to the nature ofcitrus cultivars studied under varied soil–climate and the methodsused in scheduling irrigation.
The IWP was computed to be maximum under DI at 80% Ecp
(4.993 kg m−3), followed by DI at 60% Ecp (4.675 kg m−3). The higherwater productivity resulted in DI at 80% Ecp was attributed to higherincrease in fruit yield with comparatively less increase in irrigationwater use under this treatment over other treatments. An improve-ment in IWP with optimal DI regime was also earlier reportedin citrus (Pérez-Pérez et al., 2008; García-Tejero et al., 2010). AllDI treatments resulted in higher IWP (3.780–4.993 kg m−3), withminimum value at DI at 100% Ecp in comparison to that with BI(2.361 kg m−3).
3.8. Fruit quality
Fruit quality (juice content, acidity and total soluble solids)assessment under various irrigation treatments showed that thejuice content increased with increasing irrigation level from 40%Ecp to 100% Ecp with DI (Table 10). However, the highest totalsoluble solid (10.2 ◦Brix) with lower acidity (0.83%) in juice wasobserved in DI at 80% Ecp. The higher juice content is one of the rea-sons for dilution of soluble solids concentrations in fruits with DI at100% Ecp (Davies and Albrigo, 1994). Moreover, the higher TSS andlower acidity in fruits with DI at 80% Ecp and 60% Ecp was probablycaused by enhanced transformation of acids to sugars in dehydratedjuice sacs, which is required to maintain the osmotic pressure offruit cells under mild water deficit condition prevailed under thesetreatments (Huang et al., 2000). Earlier studies also demonstratedthe higher TSS in citrus fruits under soil water deficit conditionin root zone of plants (García-Tejero et al., 2010). However, the
basin-irrigated plants produced the fruits with higher juice con-tent (37.5%) and higher TSS (9.8 ◦Brix), with lower acidity (0.86%)than that with the fruits produced in DI at 40% Ecp (juice content,36.4%; acidity, 0.88%; TSS, 9.5 ◦Brix).
y various irrigation treatments.*
IWU (m3 plant−1) IWP (kg m−3) Quality parameters
−1) Juice (%) Acidity (%) +TSS (◦Brix)
3.482 4.327b 36.4b 0.88c 9.5a
5.223 4.675c 38.8c 0.84a 10.1c
6.965 4.993c 40.2d 0.83a 10.2c
8.706 3.780b 40.4d 0.86b 9.7b
9.814 2.361a 37.5a 0.86b 9.8b
uctivity.
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8 P. Panigrahi et al. / Agricultural W
. Conclusions
DI is found as a potential water saving technique for ‘Nagpur’andarin cultivation in central India. The higher leaf nutrient (N,
and K) content of drip-irrigated plants is associated with thencreased nutrients availability in their effective root zone. Theub-optimum micronutrient content in leafs and their reductionn soil during the experimental years advocate for the applicationf required amount micronutrients-based fertilizers to mandarinlants. The higher salinity development in surface soil of drip irri-ated plots indicated the lower leaching of soluble salts under lowater application rate with drip irrigation in high clay content soil
f the experimental site. However, the salinity development underrip with sufficient water application had no clear-cut effect onlant performance. Among net-photosynthesis, stomatal conduc-ance and transpiration rate of leafs, the stomatal conductance wasound most sensitive to soil water deficit, reflecting the scope ofts use a tool for efficient irrigation scheduling in drip-irrigateditrus. All the DI regimes except irrigation at 40% Ecp proved supe-ior to BI, in relation to plant growth, fruit yield and fruit quality,ith highest irrigation water productivity under DI at 80% Ecp.
he overall reduction in growth and yield under DI at 40% Ecp
ver BI was apparently due to low photosynthesis rate caused byub-optimum soil water content in root zone of plants under theormer treatment. Irrigation water quantity of 1.2–4.5, 5.6–9.8 and2.5–21.3 l plant−1 day−1 applied through drip system in betweenecember to June is sufficient to grow 5-, 6- and 7-year-old man-arin plants, respectively, in central India condition. The significantP < 0.05) variation of soil water content at 0–0.20 m depth under DIuggests that irrigation scheduling based on soil water deficit mea-ured in 0–0.20 m soil layer through drip may be used for ‘Nagpur’andarin.The overall results of the present field investigation demon-
trate that the adoption of optimal DI regime (80% Ecp) could save substantial amount of irrigation water over traditional BI in ‘Nag-ur’ mandarin cultivation. This will help in bringing more areander irrigation, resulting in higher production of quality citrusruits. Further studies related to optimizing the quantities of NPK-ased fertilizers and micronutrients applied through DI system for
Nagpur’ mandarin is suggested.
cknowledgement
The authors acknowledge the help rendered by Mrs. Jayashree,-2-3 of National Research Centre for Citrus, Nagpur, India, innalysing the chemical properties of soil samples.
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