Effect of Drip Lateral Spacing and Irrigation Regime on Yield, IrrigationWater Use Efficiency and Net Return of Tomato and Onion in KoboGirrana Valley, Northeastern Amhara Region

Effect of Drip Lateral Spacing and Irrigation Regime on Yield, IrrigationWater Use Efficiency and Net Return of Tomato and Onion in KoboGirrana Valley, Northeastern Amhara Region

� Onion and Tomato are among themajor vegetable crops grown inKobo Girana valley.� Recently, use of drip irrigation forthese crops has increased throughgovernment assisted ground waterresources development projects.� However, the drip lateral spacingis fixed to 1m for all irrigated crops.This lead to low crop waterproductivity, loss of land, less netreturn income and un-optimizedirrigation production.� Lateral spacing is always acompromise between optimal waterdistribution and lateral cost. So, it isimperative to investigate whetherspacing adjustment and using onelateral pipe between two plant rowsis effective and economical in termsof initial investment cost andirrigation management efficiency.

Introduction

Objectives� This study was conducted todetermine the effect of drip linespacing and irrigation regime onyield, net return, and irrigation wateruse efficiency.

Results and discussion

Solomon Wondatir, Zeleke Belay and Gizaw Desta

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Fig. 1 Schematic layout of laterals and plants in the experimental plots for tomato and onion

� The Pw was the average horizontal area wetted in the top 15–30 cm of the crop rootzone as a percentage of the each lateral line area. Thus, the percentages of wetted areameasured in the experimental site were 90%or 45%for lateral spacing of single ordouble respectively.� The first irrigation for all plots was based on water deficit that would be needed tobring the 0–60 cm layer of soil to field capacity. Subsequent irrigations were appliedconsidering the 4-day irrigation interval.� IWUE was calculated as fresh fruit weight (kg) obtained per unit volume ofirrigation water applied (m3).� The net income for each treatment was computed by subtracting all the productioncosts from gross incomes. All calculations were done based on a unit area of 1 ha.

Lateralspacing

Marketableyield (tone/ha)

Waterproductivity(kg/m3)

Irrigationregime

Marketableyield (tone/ha)

Waterproductivity(kg/m3)

Onion Tomato Onion Tomato Onion Tomato Onion TomatoSingle 19.01 17.21 3.48 1.997 80%Kp 20.01 20.48 6.93 3.87

� The value of water productivitywas decreased as the amount ofirrigation amount increased.� For tomato crops the maximumirrigation water use efficiency of6.13kg/m3 was obtained fromdouble lateral spacing (2m) with80% pan coefficient.� On the other hand, waterproductivity can be increased byincreasing yield per unit landarea. In addition, watermanagement strategies andpractices should be considered inorder to produce more crops withless water.

3. Economical analysis andevaluation

� Based on lateral length, connections,tapes and drippers for the treatment inwhich double lateral spacing had 26%and 20.64% less investment costs thanin single row lateral spacing for onionand tomato respectively.� According to the calculationmaximum 81,415.93 birr and49,175.00birr yearly net income wereobtained by the effect of 1m lateralspacing with 120% irrigation regimeand 2m (double row) lateral spacingwith 80% irrigation regime for onionand tomato respectively.

� This study was conducted todetermine the effect of drip linespacing and irrigation regime onyield, net return, and irrigation wateruse efficiency.

Materials and Methods

Location: Kobo irrigation researchsite

Years: 2011 and 2012Geographically located at 12.080 N

latitude and 39.280 E longitudes at analtitude of 1470 m asl.

Mean annual rainfall is about 630 mmand average daily reference evapo-transpiration rate of 5.94 mm. Soiltype: silty clay loam, infiltration rate of8 mm/hr, pH =7.8, FC=11.5% andPWP=3.2% on volume basisrespectively

The drip system was gravitationaltype and consisted of PE laterals of16mm in diameter and PE manifoldpipeline of 32mm diameter.

The discharge rates of the emitterswere 0.9l/hr and emitter spacing was0.50m.

Design: factorial RCBD with 4replications. lateral spacing (single anddouble) and three irrigation regimes(0.8, 1 and 1.2).

For onion 0.5 & 1m and for tomato1m & 2m lateral spacing were used.

Amounts of irrigation water applied(Im3) in the irrigation were determinedusing the equation given below:

I = A*Ep* Kp*Pwhere A- is the plot area (m2),Ep- is the cumulative pan evaporationamount for the 4-days irrigationinterval.Kp -is the coefficient of panevaporation (i.e. Kp =0.8, 1.0 & 1.2)andP –is the percentage of wetted area(Pw) or percentage

CONCLUSION

Onion Tomato Onion Tomato Onion Tomato Onion TomatoSingle 19.01 17.21 3.48 1.997 80%Kp 20.01 20.48 6.93 3.87double 22.45 21.53 8.13 4.935 100%Kp 20.14 20.03 5.5 3.81

120%Kp 22.04 17.60 4.99 2.72LSD 1.24*

*2.06** 0.38** 0.244** 1.515* ns 0.46** 0.29**

CV(%) 10.2 18.1 11 12 10.2 18.1 11 12GM 20.73 19.37 5.80 3.466 20.73 19.37 5.80 3.466

Lateral spacing andIrrigation Regime

Seasonal irrigationamount (mm)

Marketable yield(tone/ha)

Water productivity(kg/m3)

Onion Tomato Onion Tomato Onion TomatoSingle row, 80%KP 461.5 449.79 18.26 17.55 4.02 1.601Single row,. 100%Kp 576.9 562.24 18.21 18.21 3.36 2.293Single row, 120%Kp 692.3 674.69 20.55 15.88 3.06 2.098Double row, 80%Kp 230.8 224.9 21.76 23.41 6.91 6.130Double row, 100%Kp 288.5 281.12 22.06 21.85 9.85 5.330Double row, 120%Kp 346.1 337.35 23.54 19.33 7.63 3.343LSD ns ns 0.65** 0.423**CV (%) 10.2 18.1 11 12GM 20.73 19.37 5.80 3.466

Table3. Interaction effects of lateral spacing and irrigation amount on marketable yield andwater productivity of onion and tomato.

� Based on lateral length, connections,tapes and drippers for the treatment inwhich double lateral spacing had 26%and 20.64% less investment costs thanin single row lateral spacing for onionand tomato respectively.� According to the calculationmaximum 81,415.93 birr and49,175.00birr yearly net income wereobtained by the effect of 1m lateralspacing with 120% irrigation regimeand 2m (double row) lateral spacingwith 80% irrigation regime for onionand tomato respectively.

1. Effects of treatments on marketable yield of onion and tomato� The highest and the lowest marketable bulb yield of onion 23.54 and 18.21 ton/hawere obtained due to the effects of 1m lateral spacing with 120% of pan amount and0.5m with 100% of pan amount respectively.� A maximum of 21.53tone/ha marketable fruit yield of tomato was obtained due tothe effect of double lateral spacing.� The amount of tomato marketable yields was slightly decreases as the amount ofirrigation water applied increased.� The maximum (23.41tone/ha) and minimum (15.88tone/ha) marketable yield oftomato were obtained due to effects of double row spacing with 80% pan coefficientand single row spacing with 120% pan coefficient.

� The highest fresh marketableyield of onion and tomato wereobtained by the effect of 1mlateral spacing with 120% pancoefficient and 2m lateral spacingwith 80% pan coefficients, whichrequires a total seasonal irrigationrequirement of 346mm and225mm respectively.� Investment costs in the designof one lateral for two crop rowswere 26% and 20.6% less than thedesign of one lateral for each croprow for onion and tomatorespectively.� As a result 1m lateral spacingwith 120% irrigation amount wasgiven the highest as 81,415.93birryearly net income return while fortomato treatment of 2m lateralspacing by 80% pan coefficientcontribute for a high economicalyearly net return income of49,175birr.� An optimized production andirrigation efficiency can beattained by applying irrigationdepth adjusted by the given pancoefficients and drip lateralspacing in Kobo Girana areas.� Generally in kobo Girana areadouble lateral spacing is moreeconomical than a single lateralspacing design for onion andtomato vegetables.

2. Irrigation water use efficiency� For tomato, maximum 9.85 and minimum 3.06kg/m3 water productivity wereexisted due to the effects of double row with 100%pan coefficient and Single rowwith 120% pan coefficient respectively.

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Nile

*-significant difference **-high significant difference

Table1. Main effects of lateral spacing and irrigation amount on marketable yieldand water productivity of onion and tomato