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DIFFERENT IRRIGATION SYSTEMS AFFECT THE YIELD AND WATER USE EFFICIENCYOF KINNOW MANDARIN(CITRUS RETICULATA BLANCO.).

Byline: A. Raza, M. A. Zaka, T. Khurshid, M. A. Nawaz, W. Ahmed and M. B. S. Afzal

Keywords: citrus, irrigation methods, high efficiency irrigation systems, yield, fruit quality.

INTRODUCTION

Citrus is extensively cultivated(9.276 million hectares) fruit crop across the world with an annual production of 146.60 million ton(AMIS, 2017). Citrus is also the leading fruit crop of Pakistan. Citrus orchards are prevalent over an area of 0.195 million hectares with an annual production of 2.267 million tons(FAO, 2017). Kinnow is the leading citrus cultivar in Pakistan and its share in the total citrus fruit production exceeds 95%(Fateh et al., 2017; Nawaz et al., 2008). In Pakistan, total share of fruit crops in earning foreign exchange is 399.51 million US dollars(1.72%); out of this 68.30 million US dollars are earned by the export of Kinnow(TDAP, 2019) Kinnow is hybrid of two citrus cultivars; a King(Citrus nobilis) x Willow Leaf(Citrus deliciosa) and belongs to family Rutaceae(Khalid, 2013). In Pakistan, district Sargodha is very popular for the production of superior quality of Kinnow fruit.

Rough lemon is used as a rootstock predominantly in Punjab, Pakistan on a commercial scale(Ahmed et al., 2007; Khalid et al., 2012; Shireen et al., 2018).

The flood irrigation system is adopted by farmers on large scale to irrigate the Kinnow orchard. Flood irrigation system is considered sub-economical because of maximum water losses and it is reported to damage citrus plants being the source of disease inoculum or carries disease inoculum from diseased to healthy plants(Savita and Nagpal, 2012). In the near future, the irrigated agriculture need two-third increase in food production to meet the food requirement of increasing population(Rockstrom et al., 2007).

According to a report, Pakistan is facing severe shortage of water, passed the water stressed level and soon may be listed into water scarce country. In Asia, Pakistan is being considered as worst performer in terms of water use(Mirjat et al., 2011). Citrus is not considered a water dependent crop but frequent irrigation is important for its proper growth and development and quality fruit(Carr, 2012). According to a report, peach trees irrigated frequently by drip irrigation performed better and had an improved fruit size and yield compared with other methods of irrigation. Frequent irrigation helped to maintain the high water status in peach plants, thus improved plant performance(Bryla et al.(2005).

Although flood irrigation is considered as a low cost and easy method of irrigation to orchards but it causes water losses, leaching of essential nutrients from the root zone and transfer of soil borne fungal diseases(Singh and Sharma, 2012); Shirgure et al., 2000). Traditional irrigation systems such as overhead sprinkler and flooding system keep the soil, leaves and tree's stem wet for a longer period of time which may promote infection by molds and fungi. Flood irrigation consumes extra water while the drip irrigation technique slowly supplies measured quantity of water to the root zone of the plants, only(Kumar, 2016). Pressurized irrigation system such as drip and sprinklers are modern methods of irrigation through which a control and desired amount of water is applied to the orchard. Besides water saving, the drip system also increases the fruit yield of citrus fruits(Morgan et al., 2010).

In drip irrigation system water is supplied frequently, often daily to maintain favorable soil moisture conditions and prevent the plants from moisture-stress and also to ensure proper use of water resources(Galande and Agrawal, 2013).

Many farmers in developed countries such as USA and Australia have already adopted these modern techniques(Shirgure, 2012). Kumar et al.(2008) stated that the real water saving would be more for row crops such as fruit orchards, cotton, fennel, castor, and many vegetables. He further added that under traditional irrigation system a large area between the plants row is directly exposed to solar radiation and wind, and as a result the non-beneficial evaporation would be a major component of the total water depletion. Kanber et al.(2007) have pointed out that enhancement in WUE depends on productivity gains depicted by consistent increase in output per unit input and the irrigation technique. Improved WUE in agriculture is important for water conservation and to obtain higher yields. Modern irrigation technologies such as sprinkler and micro irrigation are efficient and have the potential to substantially improve yield.

Furthermore, among pressurized irrigation systems, drip system ensures more irrigation water saving compared with full cover and strip cover sprinklers(Kadyampakeni et al., 2014). According to the best of our knowledge, limited reports are available regarding the impact of pressurized irrigation systems for fruit plants in Pakistan. This study was conducted to assess the effect of pressurized irrigation systems on the fruit yield and WUE of Kinnow mandarin under agro-climatic conditions of Sargodha, Pakistan.

MATERIALS AND METHODS

Experimental area and design: The study was conducted at CRI, Sargodha, Punjab, Pakistan(32Adeg 4' ' N and 72Adeg 40' ' E) on 25 years old Kinnow mandarin plants. The plants were grafted onto rough lemon rootstock cultivated on silt clay loam soil(soil characteristics of the experimental area are provided in Table 1). The experiment duration was 4 years from 2011-2015. A 0.5 ha Kinnow block with planting geometry of 6.1 m x 6.1 m square system, previously under flood irrigation system was equally divided into three blocks. Four different irrigation systems: drip irrigation(DI), full cover sprinkler(FCS), and strip cover sprinkler(SCS) irrigation systems were established in each block separately and for traditional flood irrigation(TFI) system a separate block of 0.5 ha was selected as a control. Experiment was laid out according to randomized complete block design(RCBD).

Three plants were selected as a treatment unit and each treatment was replicated four times. One complete row between the experimental plants was kept as buffer line to eliminate any kind of error caused by seepage effect. Each block of every irrigation system received equal amount of nutrients including 1000 g nitrogen, 500 g phosphorus and 500 g potash per plant, annually. All phosphorus and potash fertilizers were applied in January whereas nitrogen(except drip irrigation system) was applied in three equal splits(last week of February, last week of May and August. In drip irrigation system nitrogenous fertilizer(Urea) was applied as fertigation. Through fertigation, 20% N was applied before flowering(February to March), 60% N was applied from fruit setting to cell division and cell development stage(April to June), and remaining 20% N was applied during late summer to colour break stage(July to mid October).

Physiochemical properties of the soil: The soil was silt clay loam. EC and pH indicated that it was a normal but calcareous in nature. The phosphorus and potassium contents were found in optimum range but organic matter percentage was in deficient range(Table 1).

Irrigation schedule: Irrigation schedule for different irrigation systems such as DI, FCS and SCS was developed on the basis of soil pit examination at experimental site and evapotranspiration source from University of Agriculture Faisalabad, Pakistan.

Installation of tensiometers and measurement of water discharge: Tensiometers were installed in each block at 30 cm, 60 cm, and 90 cm soil depth to monitor the moisture level in the soil. The irrigation was applied when tensiometer reading reached above 40 centibars(an average reading of tensiometers which were installed at 30 cm and 60 cm depth). A flume meter was used to measure the total quantity of water applied under flood irrigation system. In DI system, two drip lines were installed under the tree canopy along each tree row planted in 6.1 m x6.1 m distance. Each drip line had 15 pressure compensator drippers with water discharge of 1.66 mmh-1, and 30 drippers were used for each tree, therefore each tree received irrigation water of 49.8 mmh-1.

In FCS, one sprinkler with discharge of 5.5 mmh-1 was installed within each tree row whereas in SCS, three sprinklers were installed under each tree's canopy with discharge of 3.5 mmh-1, and therefore, received irrigation water of 10.5 mmh-1 tree-1. The total operational hours per season were recorded and total irrigation water applied to each pressurized system was calculated as:

Total irrigation water applied to each tree= Total operational hoursxDischarge rate(mm h - 1)

Water Use Efficiency(kg m-3): WUE was calculated using the following formula:

WUE = {Total yield(t ha-1)/Total water used(mm)}x100

Measurement of yield and different fruit characteristics: At fruit maturity, total fruit yield(kgtree-1) was determined by harvesting all fruits on a tree. Fruit size(diameter) of one hundred fruits per tree at random was measured with digital vernier caliper at maturity stage. Ten fruits tree-1 were collected for measuring the average fruit weight(gfruit-1) and further used for physicochemical analysis of the fruit. Rotary squeezer was used to extract the juice from the fruits. The juice was filtered using 0.8 mm sieve. The weight of juice was measured using an electric balance and juice percentage was calculated according to the following formula(Ahmed et al., 2007):

juice% = juice weight(g) / fruit weight x 100

The rag percentage was determined using the following formula:

juice weight + peel weight/fruit weightx100

Total soluble solids(TSS) were determined using a refractometer. The acidity was determined by titration with 0.1 N NaOH using a known volume of representative sample of the fruit juice. Phenolphthalein was used as an indicator to check the persistent pink colour(Lacey et al., 2009; Nawaz et al., 2008).

Statistical analysis: The data were analyzed using Statistix software version 8.1(Analytical Software, Miller Landing Rd, Florida, USA). Four years data were pooled and then analysis of variance(ANOVA) was performed(Steel et al., 1997). Treatment means were compared using Fishers least significant difference test at P a$? 0.05.

RESULTS

Yield and physicochemical properties of Kinnow fruit: Different irrigation systems significantly affected the fruit yield and physicochemical characteristics of Kinnow. Number of fruitstree-1(1288) and fruit yield(181kgtree-1) were significantly(Pa$?0.05) increased by using DI system followed by FCS(151 kg tree-1). Different irrigation systems had no effect on individual fruit weight.

Fruit diameter was significantly improved for the fruits obtained from the plants irrigated with TFI system; however, the diameter of the fruits obtained from plants irrigated by all other irrigation systems was not significantly different(Table 4).

A gradual increasing trend was observed on the yield during four years of this study in DI, FCS and SCS irrigation systems. In TFI system, fruit yield during different years of the study did not increase significantly. An average higher yield(43.88 t ha-1) was found in drip irrigation system(40.46% higher) compared with TFI system(26.12 t ha-1). Fruit yield was 28.45% and 27.19% higher in FCS and SCS irrigation systems, respectively compared with TFI system(Table 5).

Juice percentage was significantly(P a$? 0.05) affected because of different irrigation systems(Table 6). FCS and DI system produced significantly higher fruit juice percentage of 48.70% and 47.68%, respectively whereas lower juice percentage of 46.41% and 47.01% was observed for SCS irrigation system and TFI system, respectively.

Total water consumption and irrigation water saving in different irrigation systems: During the crop season from 2011-15 the average water saving in drip irrigation system was 55% and 30% in strip cover sprinkler irrigation system compared with flood irrigation system. An economical water consumption was observed for drip irrigation system(195.92 mm year-1 and total water 904.37 mmyear-1), followed by strip cover sprinkler where irrigation water usage and total water consumption was 300.89 mmyear-1and 1009.34 mmyear-1, respectively. Full cover sprinkler and flood irrigation systems used comparatively high delta of water compared with drip irrigation, strip cover sprinkler irrigation system(Table 7).

Water Use Efficiency(WUE) of different irrigation systems: Average WUE was higher(4.85 kgm-3) for DI system followed by SCS irrigation system. The better WUE of 10.65kg m-3, 9.99kg m-3 and 5.83 kg m-3 was observed for DI, SCS and FCS, respectively during 2013-14(Fig. 1).

Table 1. Fertility status of experimental area(pretreatment).

Soil depth(cm)###pH###EC(dS m-1)###OM###Av. P###Av. K###Texture

###(%)###(ppm)###(ppm)

0-15###7.9###0.15###0.90###20.20###168###Silt clay loam

15-30###8.0###0.11###0.65###14.16###75

30-60###8.0###0.09

60-90###7.9###0.10

90-120###8.0###0.09

120-150###7.8###0.08

Table 2. Evapotranspiration, crop coefficient, monthly, and daily water requirement for large citrus trees - 70% ground cover.

Month###Evapotranspiration(mm)###Crop###Monthly water requirements###Daily water requirement

###per day###Coefficient###(full production)(mm)###(full production)(mm)

January###1.4###0.7###30###1

February###2.2###0.7###48###1.5

March###3.5###0.7###76###2.5

April###4.8###0.7###101###3.4

May###6.2###0.7###130###4.3

June###6.5###0.7###141###4.6

July###5.4###0.7###117###3.8

August###4.9###0.7###106###3.4

September###4.7###0.7###102###3.3

October###3.3###0.7###69###2.3

November###1.9###0.7###41###1.3

December###1.5###0.7###32###1.1

Table 3. Approximate irrigation requirement for drip, full cover sprinkler(FCS) and strip cover sprinkler(SCS) irrigation systems.

Month###Approximate irrigation###Approximate irrigation###Approximate irrigation

###requirement for drip###requirement for FCS###requirement for SCS

January###10 h / 15 days###10 h / 1 per month###8 h/ 1 per month

February###10 h / 10 days###10 h / 1 per month###8 h/ 15 days

March###10 h / 6 days###10 h / 15 days###8 h/ 10 days

April###10 h / 4 days###10 h / 15 days###8 h/ 7 days

May###10 h / 3 days###10 h / 10 days###8 h/ 5 days

June###10 h / 2 days###10 h / 10 days###8 h/ 5 days

July###10 h / 4 days###10 h / 12 days###8 h/ 6 days

August###10 h / 4 days###10 h / 15 days###8 h/ 7 days

September###10 h / 4 days###10 h / 15 days###8 h/ 7 days

October###10 h / 6 days###10 h / 15 days###8 h/ 10 days

November###10 h / 11 days###10 h / 1 per month###8 h/ 15 days

December###10 h / 13 days###10 h / 1 per month###8 h/ 1 per month

Table 4. Effect of different irrigation systems on the fruit yield and yield attributes.

Irrigation systems###No. fruit tree-1###Fruit yield(Kg tree-1 )###Fruit weight(g)###Fruit diameter(mm)

Drip irrigation###1228 A###181.13 A###152.14 A###68.78 BC

Full cover sprinkler###1029 B###151.34 B###149.15 A###70.12 B

Strip cover sprinkler###1045 B###147.92 B###155.18 A###67.58 C

Traditional Flood irrigation###687 C###104.55 C###152.34 A###73.16 A

CVa###151.15###20.32###6.4606###2.12

Table 5. Impact of different irrigation systems on yield(t ha-1) of Kinnow.

Irrigation systems###2011-12###2012-13###2013-14###2014-15###Average

Drip irrigation(DI)###28.75###32.37###49.66###64.74###43.88

Full cover sprinkler(FCS) irrigation###27.26###24.72###35.69###58.38###36.51

Strip cover sprinkler(SCS) irrigation###32.71###22.28###40.11###48.4###35.88

Traditional flood irrigation(TFI) system###30.02###23.72###23.65###27.11###26.12

Table 6. Effect of different irrigation systems on the physicochemical properties of the Kinnow fruit.

Irrigation systems###Juice(%)###Rag(%)###Peel(%)###TSS/Acidity ratio

Drip irrigation###47.68 AB###20.61 A###31.70 A###15.57 A

Full cover sprinkler###48.70 A###19.24 A###32.07 A###15.34 A

Strip cover sprinkler###46.41 B###20.90 A###32.68 A###15.90 A

Traditional flood irrigation###47.01 B###21.26 A###31.75 A###16.02 A

CVa###1.62###1.99###1.4###0.95

aCoefficient

Table 7. Total water consumption by different irrigation systems.

###Full cover sprinkler###Strip cover###Traditional flood

###Drip irrigation(DI)###(FCS)###sprinkler(SCS)###irrigation(TFI)

###Irrigation###Total W###Irrigation###Total###Irrigation###Total###Irrigation###Total

Year###W###W###W###Rainfall

###mm

2011-12###188.66###411.98###515.99###739.31###354.74###578.06###432.68###656.00###223.32

2012-13###338.62###755.62###951.36###1368.36###567.59###984.59###588.82###1005.82###417

2013-14###146.73###466.23###292.93###612.43###165.12###484.62###473.67###793.17###319.5

2014-15###109.65###1983.65###225.75###2099.75###116.10###1990.10###238.43###2112.43###1874

Average###195.92###904.37###496.51###1204.96###300.89###1009.34###433.40###1141.86###708.45

Table 8. Combined ANOVA

###SOV###MSE

###Number of fruit tree-1###Fruit yield###Fruit dia.###Fruit weight###Juice %###Peel %###Rag %

Treatment###812691**###15916.6**###92.25**###97.04 NS###15.4329*###3.287 NS###12.573 NS

Year###2190685**###29941.3**###350.407**###1539.65*###36.8764*###282.779**###173.761**

Treat*Year###261837**###4766.4**###215.564**###201.55*###5.1074NS###3.994 NS###6.846 NS

DISCUSSION

Effect of irrigation systems on the fruit yield and physicochemical properties of Kinnow fruit: Pressurized irrigation systems proved their advantage over flood irrigation system in terms of yield. Among pressurized irrigation systems, the drip and strip cover sprinkler performed better for producing higher fruit yield. Performance of drip irrigation system was excellent in terms of yield because in drip system a frequent irrigation supply was maintained in the active root zone of the tree and therefore losses of essential nutrients because of leaching were reduced. Another factor of increased fruit yield in drip irrigation system is application of the nitrogen fertilizer through fertigation method(Shirgure, 2012). In pressurized irrigation systems(DI, FCS and SCS irrigation system), yield was gradually increased from 1st year(2011) of experiment to the final year(2015) of the study.

This increase in yield can be attributed to maintenance of optimum moisture level in the soil, suppression of weed growth and less disturbance of the roots(Panigrahi et al., 2012) that promoted plant growth. Higher juice percentage was obtained from full cover sprinkler and drip irrigation system whereas this was lower in strip and flood irrigation systems. This might be due to larger sized fruit with higher peel and rage percentage, therefore less juice percentage was produced(Sandhu, 1991). Holzapfel et al.(2004) obtained higher yields in blueberry with drip irrigation system compared with sprinkler systems with similar amounts of applied water. In our study, fruit weight remained similar with all irrigation systems although fruits with larger diameter(fruit size) were produced in flood irrigation system compared with other irrigation system utilized in this study.

This increase in fruit size might be attributed to larger differences in fruit yield as compared to pressurized irrigation systems(Guardiola and Garcia-Luis, 2000; Smith and Samach, 2013). Katuuramu et al.(2011) and Meland(2009) also found similar results for apple and concluded that size and weight of apple fruit were affected by the crop load.

Total water consumption in different irrigation systems and irrigation water saving: According to the findings of our study, 55% water saving is achieved using drip irrigation system and 35% water saving is achieved using strip cover sprinkler irrigation system compared with TF. Sprinkler irrigation systems seems less suitable over drip irrigation system because under hot and dry climatic conditions of Pakistan temperature reaches to a maximum of 48-50 AdegC, thus evaporation losses are increased and a large amount of water cannot be available to the plants(Abbas and Fares, 2009). Furthermore, maintenance cost of sprinkler irrigation system is also higher compared with drip irrigation system. According to another report, water saving is generally higher for drip irrigation systems compared with sprinkler irrigation systems(Kumar and van Dam, 2013).

With drip irrigation, water could be directly applied to the plants, preventing non-beneficial evaporation. This will not be possible with sprinklers because sprinklers wet the entire field area instead of the plant root zone(Viswanathan et al., 2016). Similarly, Fallahi et al.(2010) observed that application of water using drip irrigation system, calculated based on full ETc rate and adjusted for groundcover, results in major water saving and improves the yield and fruit quality of apples. According to Hijazi et al.(2014) application of water by drip irrigation to olive trees also resulted in 34.40% water saving and improved the fruit yield by up to 19.20% compared with surface irrigation system using soil rings.

In drip irrigation system, water is applied directly to the root zone of area drop by drop in small amount thus subjected to less evaporation or deep percolation below the active root zone, whereas sprinkler system spreads water directly into the air thus water losses are increased. In this study, drip irrigation system consumed minimum amount of irrigation water(195.92 mm) followed by strip cover sprinkler(300.89 mm) compared with flood irrigation system(433.40 mm)(Table VII). Water consumption under flood irrigation system was higher because in flood irrigation a huge amount of water had been applied to irrigate the entire field without targeting the root zone of trees. Resultantly, a lot of water is lost because of evaporation and deep percolation. Rainfall is the major contributing factor that affects the irrigation water requirements.

There is greater difference in irrigation water consumption and rainfall contribution. According to data, rainfall ranged from a minimum of 223 mm during 2010-2011 to maximum of 1874 mm during 2014-2015. The highest rainfall received during 2014-2015 could not be considered beneficial for orchards because most of the rainfall occurred during two months(July to August, 2014-2015).

Water Use Efficiency(WUE) of different irrigation systems: WUE depends upon output [yield(t ha-1)] and input [total water(mm)] consumed. In this study, WUE was higher for drip irrigation system(4.85 kg m-3) followed by strip cover sprinkler irrigation system(3.55 kg m-3). The improved WUE for drip irrigation system can be attributed to low potential evaporative losses compared with sprinkler irrigation system. Similar results were also reported by Maisiri et al.(2005), they observed that drip irrigation uses only 35% of the water compared with surface irrigation system, providing higher IWUE(irrigation water use efficiency). Similarly, Yin et al.(2011) reported that drip irrigation system consumed only 21% to 29% of irrigation water compared with micro sprinkler irrigation system, and WUE was improved by 167% to 234% with drip irrigation system compared with micro sprinkler irrigation system.

Fruit yield and fruit quality including firmness, color, and size did not differ regardless of irrigation system. According to another report, surface and drip irrigation systems ensures 28% to 35% water saving compared with improved graded furrows, and increase water productivity from 0.43 kg m-3 to 0.61 kg m-3(Darouich et al., 2014).

Conclusion: This study shows that drip irrigation system improves the fruit yield of Kinnow and ensures water saving. Moreover, higher WUE was also achieved by using drip irrigation system compared with traditional flood irrigation system. Consumptive use of water was the minimum in drip irrigation system followed by strip cover sprinkler irrigation system. Taken together, drip irrigation is recommended followed by strip cover sprinkler among the different pressurized irrigation methods on the basis of good yield and higher WUE of Kinnow orchard. Thus, citrus growers of Sargodha(Punjab, Pakistan) area can adopt drip irrigation system to improve the Kinnow yield and WUE.

Acknowledgements: This study was supported by Agriculture Sector Linkage Program(ASLP), Citrus Project under Australian Aid Program. The authors are thankful to Prof. Jose Eduardo Serrao, Department of General Biology, Federal University of Vicosa, Brazil for improving the language of this manuscript.

Conflict of interest: All the authors declare no conflict of interest.

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Author:A. Raza, M. A. Zaka, T. Khurshid, M. A. Nawaz, W. Ahmed and M. B. S. Afzal
Publication:Journal of Animal and Plant Sciences
Geographic Code:9PAKI
Date:Oct 31, 2020
Words:5496
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