Effect of Different Irrigation Water Qualities on Turnip Production and Water Productivity under Furrow Irrigation Method

Abstract: A field experiment was conducted at Sindh Agriculture University Tandojam during the year 2015-16, aiming to investigate the response of turnip crop to various salinity levels of irrigation. The experiment was placed applying randomized complete block design (RCBD) with four different treatments i.e. Freshwater (I1), ECw with 2.5, 3 and ECw3.5 dS m (I2, I3 and I4) respectively replicated thrice. The results for experiment placed revealed an average increase in soil ECe 0.09, 0.17, 0.26 and 0.38 dS m under I1, I2, I3 and I4 respectively. An decrease in dry density (g cm) of soil profile, decrease in pH 0.19, 0.38, 0.5 and 0.84 in treatments I1, I2, I3 and I4 respectively and an decrease in agronomical data i.e. weight and diameter were also observed with an increase in ECw by the water being irrigated. Crop water productivity with 5.83, 4.35, 2.97 and 1.85 kg m for treatmentsI1, I2, I3 and I4 respectively also decreased with an increase in ECw and Nacl. Average yield of 19.27, 14.37, 9.83 and 6.12 kg was obtained with applied treatments i.e. I1, I2, I3 and I4 respectively, thus a decrease in yield with 25.45%, 31.60% and 37.72% with treatments I2, I3 and I4 was observed when compared as treated by freshwater (I1). Therefore farmers can use irrigation water having ECw 3.5 dS m for the turnip crop at reduction of 37.72% (approximately).


INTRODUCTION
Pakistan lies in arid and semi-arid region.It is estimated that Pakistan has an annual rainfall of 250 mm on about 68% of the geographical area [1].It is therefore required to fulfil the water requirement of crop for essential crop production, which is possible when supplemented through irrigation.The agriculture sector is under increasing pressure to sustainably produce higher yields with less inputs under declining land and water productivity potential [2].In the world Pakistan is counted to be sixth most heavily populated country, having a population of 177.1 million which at a rate of 2.05% is growing annually [3].With continual population growth, these areas are now becoming depleted because of over exploitation of soils, plant and water resources [4].Pressure on the use of fresh water used for the consumption of human, agriculture and industries is being tremendously developed in arid and semi-arid regions [5].New methods are need to be developed imperatively in which low quality water and degraded land could be used to increase the productivity [6].Considering the rapid increase in demand for food, feed, fuel, fiber and low per capita availably of water resources, it is necessary to use saline water to grow plants [7].Saline irrigation water *Address correspondence to this author at the Faculty of Agricultural Engineering, Sindh Agriculture University Tandojam, Sindh, Pakistan; Tel: +92-332-3996362; E-mail: shakeelsoomro@live.comcan also be utilised to grow crops without long term hazardous consequences to crops or soils [8].Plant height, germination rate, production and the water use efficiency do effects with applied irrigation method and the quality of water [9].Furrow irrigation is said to be 30% in water use efficiency as compared to other conventional methods [10].Worldwide furrow irrigation is being adopted at about 90 percent of lands, reason behind is it's less need of energy [11].The water is being conserved in furrow irrigation method, as the water is applied to the root zones which are refilled at requited depth [12].
Turnip (Brassica rapa L.) belongs to Cruciferae family and is an important root crop of winter season.Turnips are grown both for greens and for the fleshy roots.Turnip leaves contain more than 18% crude proteins, while the roots contain about 10% crude protein.Turnips with Europe are widely cultivated throughout the world [13].At present turnips are under cultivation in many countries, including Indo-Pak subcontinent.During 2011, the total area under cultivation of turnip in Pakistan was 15700 hectares, with total production of 275,700 tonnes [14].Keeping in view the above facts, this study was conducted to observe the effect of irrigation water quality on growth, yield and water productivity of turnip crop.

Preparation of Irrigation Water
Sodium Chloride (NaCl) of Daejung chemicals and metals company limited Korea was manually mixed in irrigation water in drum (30 liters) to obtain the required EC w as per designed treatment (Table 3) and were then checked with digital EC meter every time for EC w .

Irrigation
Pre-soaking irrigation of 10.2 cm was applied before the preparation of seedbed whereas preparation of seedbed was done when the soil reached at field capacity.The depth of irrigation was kept at 7.62 cm per irrigation at an interval of days, A.R.I. [18].Relationship of volumetric method given below was used to estimate quantity of irrigation water Volume of water (m 3 ) = Length of furrow x width of furrow x depth of water The volume of water per furrow per irrigation was calculated to be 0.09906m 3 (with Length of 2.6m, Width of 0.5m and Depth of 0.0762 m).Each plot had four furrows, the total volume of water per plot per irrigation was calculated to be 0.39624 m 3 .

Manures and Fertilizers
20 cartloads per acre of well rotten farmyard manure were incorporated in the soil at the time of last ploughing.One bag of DAP per acre was also mixed with soil, PAR [19].These recommendation doses application were calculated on experimental field basis as farm yard manure (408 kg plot-1) and DAP (1.97 kg plot-1).

Crop Water Productivity
Equation given below was used for determining Crop water productivity per hectare, Isaac et al. [20]:

CWP = Y h TW
Ten plants were randomly selected in each plot.Observation viz., diameter (cm), weight of turnip fruit -1 (g), yield (kg plot -1 ) and yield (kg ha -1 ) were recorded and tabulated.Statistix Software (ver.8.1) was used for the analysis of variance and mean separation.

Electrical Conductivity of Soil (dS m -1 )
Pre and post results for electrical conductivity of the soil profile at various depths are given in Table 4.The average electrical conductivity of soil at all depths for pre experiment was 3.05 dS m The results are in line with Wenjun et al. [21] and Gandahi et al. [22], who stated that average EC e values of soil irrigated with saline water were higher than that of soil irrigated with fresh water.

pH of Soil
pH of the soil profile (pre and post) at various depths are presented in Table 5.The average pH at all depths for pre experiment was 7.63 and 7.44 for post experiment for treatment I 1 , 7.69 for pre experiment and 7.31 for post experiment for treatment I 2 , 7.66 for pre experiment and 7.16 for post experiment for treatment I 3 and 7.79 for pre experiment and 6.95 for post experiment for treatment I 4 .The Analysis of variance for interaction showed non-significant (P>0.05)effect of different irrigation water qualities treatments on post experiment of pH of soil profile.Results are in line with Anwar et al. [23], they observed a decrease in pH of soil with increasing EC of irrigated water.

Dry Density (g cm -3 )
Table 6 shows the pre and post experiment for dry density of the soil profile.The average dry density for pre experiment was 1.35 g cm -3 and for post experiment it was 1.22g cm -3 for treatment I 1 , 1.36 g cm -3 for pre experiment and 1.20g cm -3 for post experiment for treatment I 2 , 1.35 g cm -3 for pre experiment and 1.22 g cm -3 for post experiment for treatment I 3 and 1.36 g cm -3 for pre experiment and 1.24 g cm -3 for post experiment for treatment I 4 .The Analysis of variance for interaction showed a nonsignificant (P>0.05)effect of different irrigation water qualities treatments on post experiment of dry density of soil profile.The outcomes of conducted experiment are related to those stated by Gandahi et al. [22], who observed a decrease in dry density of soil on the top layer treated with saline water which was further decreased at higher depth.

Turnip Yield Per Treatment
Table 7 shows the three replicated average yield of turnip crop under different irrigation treatments.Average yield was calculated to be 19.27kg, 14.37 kg, 9.83 kg and 6.12 kg for treatments I 1 , I 2 , I 3 and I 4 respectively.Calculated yield per hectare was 19,504.05kg, 14,541.16kg, 9,946.02kg and 6,194.33kg under I 1 , I 2 , I 3 and I 4 respectively.Analysis of variance showed that there was a significant (P<0.05)effect of different irrigation water qualities treatments on turnip yield (kg plot -1 ) and (kg ha ).The experimental observations are in line with Yaohu et al. [24] they reported that crops irrigated with saline water decreased in yield as compared to crop irrigated with fresh water.

Decrease in Crop Yield
Table 7 shows the decreasing percentage of the yield when compared with the yield of the experimental crop irrigated with freshwater.The yield was 19,504.05kg ha -1 with I 1 (control).The yield decreased 25.45 %, 31.60% and 37.72% with treatment I 2 , I 3 and I 4 respectively.

Agronomical Parameters of Turnip Crop
Table 8 shows the average weight, and average diameter of selected ten different fruits of all the treatments.Analysis of variance showed that there was a significant (P<0.05)effect of different irrigation water qualities treatments on turnip weight (g) and diameter (cm).

Weight
Ten different sizes of fruits were weighted by weight balance.The average weight of the selected fruits was 124.6 g, 91.2 g, 62.9 g, and 38.5 g for I 1 , I 2 , I 3 and I 4 respectively.The same has been observed by Maliwal [25], that plant growth; shoot dry weight, root length and root dry weight decreased with increasing salinity.

Diameter
The diameter of ten different selected turnip fruit were measured through Vernier calliper and were found to be 5.71 cm, 4.63 cm, 3.27 cm and 2.77 cm for I 1 , I 2 , I 3 and I 4 respectively.

Irrigation Water
Schedule of Irrigation water applied is given in Table 9.Total water applied from sowing to the harvesting was calculated to be 3.30408 m 3 and 3344.211m 3 per hectare.

Crop Water Productivity
Table 10 shows the crop water productivity of turnip crop.The average of three replications was calculated to be 5.83kg.m-3 , 4.35kg.m-3 , 2.97 kg.m -3 and 1.85 kg.m -3 for I 1 , I 2 , I 3 and I 4 respectively.Analysis of variance showed that there was a significant (P<0.05)effect of different irrigation water qualities treatments on water productivity of turnip crop.Similar results has also been reported by Aich et al. [26] and by Yaohu et al. [24], that grain yield decreased with increase in salinity of irrigation water.

CONCLUSION
The study has shown that saline water can be used to irrigate crops, but long term use may reduce crop experiment it was 3.14 dS m -1 for treatment I 1 , 3.07 dS m -1 for pre experiment and 3.24 dS m -1 for post experiment for treatment I 2 , 3.06 dS m -1 for pre experiment and 3.32 dS m -1 for post experiment for treatment I 3 and 3.06 dS m -1 for pre experiment and 3.44 dS m -1 for post experiment for treatment I 4 .The Analysis of variance (ANOVA) showed a significant (P<0.05)effect of different irrigation water qualities treatments on post experiment of ECe of soil profile.