DRIP IRRIGATION AND FERTIGATION OF POTATO UNDER LIGHT-TEXTURED SOILS OF CAPPADOCIA REGION
*Mahmut Basri Halitligil, **Hüseyin Onaran, ***Nuri Munsuz, *Hakan Kışlal, *Ali Akın, **Abdullah Levent Ünlenen, ***Gökhan Çaycı, ***Cihat Kütük * Turkish Atomic Energy Authority, Ankara Nuclear Research Center in
Agriculture and Animal Science, Ankara - Turkey
** Ministry of Agriculture, General Directorate of Research, Potato Research Institute, Niğde - Turkey
*** Ankara University, Agricultural Faculty, Soil Science Department, Ankara – Turkey
Abstract
In order to evaluate potato respone to drip irrigation and N fertigation; and also to improve nitrogen and water use efficiencies of potato and eventually to obtain less nitrogen polluted surface and ground water, 10 field experiments were carried out at three different locations in Cappodocia Region of Turkey in 1997, 1998, 1999 and 2000.
Nitrogen as ammonium sulphate [(NH4)2So4], was supplied through drip irrigation water (fertigation) at rates of 0, 30, 60, and 90 kg N/da. Also, soil N application treatment equivalent to the fertigation treatment of 60 kg N/da was included. These five treatments were investigated in a completely randomized block design with four replications. Agria potato variety was used in all experiments and potato was planted in mid May and harvested at the end of October. 15N-labelled ammominum sulphate fertilizer were applied in isotope-sub plots within the macroplots for each treatment in order to determine the amount of nitrogen taken up by the plant, nitrogen use efficiency and the distrubution of residual nitrogen at different depths in the soil profile. Each year during the growth period 12 irrigations were done and 50 mm of water was applied at each irrigation. At harvest, plant samples (tuber and leaf+vein) and soil samples were taken and % N, % 15N atom excess (% 15N a.e.) and % Ndff determinations were done. Soil water contents at different soil depths were determined by soil moisture neutron probe at planting and at harvest so that water contents at different soil layers and water use efficiencies were calculated for each treatment.
The results obtained showed that 3350 kg/da mean total marketable tuber yield was obtained with application of 600 mm irrigation water. Also, it was found that water did not move below 90 cm of soil layer in drip irrigation-fertigation system, which showed clearly that no nitrogen movement occurred beyond 90 cm soil depth. Tuber yields and % Ndff increased when nitrogen is applied with drip irrigation-fertigation system in comparision to the application to
the soil and then drip irrigation. At harvest, more nitrogen was accumulated at shallower depths with fertigation treatments.
Introductıon
Soils in the Cappadocia region of Turkey are mainly light-textured (sandy, loamysand, or siltloam) and the prevailing irrigation method used by the farmers is sprinkler. Due to the very high N fertilizer and water usage (nearly 100 kg N/da and 1400-1700 mm of water, respectively) by the farmer in the region for the potato production, some researchers (Karaca and Demir, 1994; Halitligil et al., 2002) conducted field experiments at different locations in the region. Karaca and Demir, 1994 reported that 550 kg N/ha is the economical rate for potato under these light-textured soils. Halitligil et al., 2002 conducted field experiments with potato using 15N labelled fertilizer in order to find out the N balance under sprinkler irrigation in the region rate. Their results showed that nearly half of the applied fertilizer N (45.6 %) at 40 kg N/da rate and more than half of the applied fertilizer N (60.8 %) at 100 kg N/da rate was in 0-200 cm depth in the soil after harvest. In the region, the water for irrigation, animal and as well as human use is directly pumped from the ground water resources due to lack of other resources. As a result of their their findings, the researchers suggested that some agricultural measures to prevent or decrease the nitrate contamination of ground waters (as changing the prevailing sprinkler irrigation system to the drip irrigation-fertigation system) must be taken after the completion of the necessary investigations of the new irrigation + fertigation system in the region.
Therefore, the main objectives of this study are : (1) to find out the fate of 15N-labelled ammonium sulphate fertilizer applied under light textured soil when drip irrigation-fertigation system is used; and (2) to find out if the nitrate contamination of ground waters can be lessened or prevented by using drip irrigation-fertigation system.
Materıal and methods
Ten drip irrigation-fertigation field experiments were conducted at Niğde Potato Research Institute and Gölcük in 1997; at Niğde Potato Research Institute, Hasaköy and Suvermez in 1998, 1999 and 2000 in Niğde and Nevşehir provinces of the Cappadocia Region of Turkey.
The experimental design used in all experiments was a completely randomized block with four replications. Potato variety Agria was used in every experiment. Nitrogen as ammonium sulphate (NH4)2So4 was supplied through drip irrigation water (fertigation) at rates of 0, 30, 60, and 90 kg N/da (N0, N1, N2 and N3 treatments respectively ). Also, soil N application treatment (NSoil) equivalent to the fertigation treatment of 60 kg N/da was included; therefore five treatments were investigated in all experiments. Each plot consisted of four rows which measured 2.8 m x 5.0 m = 14.0 m2 with 70 and 30 cm between and within row
spacing, respectively, at planting and 1.4 m x 5.0 m = 7.0 m2 at harvest. There were four dripper lines (plastic hose with 13 and 20 mm inside and outside diameter, respectively, with drippers 25 cm apart which can supply 4 l/h at 2 atu pressure) in each plot placed in the furrows.
15N labelled ammonium sulphate fertilizer (with 2.0 and 1.634 % 15N a.e. enrichments, in 1997 and in other three years, respectively) was applied by inverted bottles, with drippers, simulating the drippers of the original irrigation line (Papadopoulos, 1995) to three plants in each plot.
In all experiments, irrigations began at the middle of June just after hilling and continued weekly for twelve weeks and at each irrigation 50 mm of water was applied. Thus, totally 600 mm of irrigation water was applied during the whole growth period.
Evapotranspiration (ET, mm) and water use efficiency (WUE, kg/da.mm) values were determined according to the following equations.
mm water mm water
ET (mm) = (at planting - at harvest ) + mm rainfall during groth season in 0-90 cm layer in 0-90 cm layer
Yield, kg/da WUE (kg/da.mm) = ET, mm
Plants from each plot were harvested and separated into tuber and leaf + vine. Marketable tuber and dry matter yields were determined from the main-plots. Meanwhile, tuber and leaf + vine of one out of three plants from each 15N micro-plots were harvested and dried at 70o C, ground and passed through a 2 mm screen for % N and % 15N a.e. analysis by micro Kjeldahl method (Keltech) and the Dummas dry combustion method and emission spectrophotometer (Jasco 150), respectively, according to Halitligil et al., 2002. The nitrogen yield (kg N/da), % Ndff, N fertilizer yield (kg N/da) and % NUE values were calculated according to Halitligil et al., 2000.
ANOVA of the data for fresh and dry matter yield, N upake, Ndff, NUE, total N, fertilizer N residue and fertilizer lost were done for each location and year separately and also for averages over location and years according to Steel and Torrie, 1960. Differences among means were tested using LSD test at P< 0.05 and lettered accordingly.
Results
15N balance data
Yields, N uptake and total N in the soil before planting and after harvest for the all treatments are averaged over locations and years in Table 1.
of application such as that they increased with increasing N rates and reached maximum values with 90 kgN/da N3 treatment Table 1. The soil application treatment (NS) gave significantly lower total fresh tuber yields than the equivalent fertigated treatment N2. Also for the total marketable tuber yield the soil application treatment gave lower yields than the equivalent fertigation treatment however the differences were not statistically significant.
Table 1. Fertilizer N effects on dry matter yield, N uptake, N derived from
fertilizer (Ndff; % and kg N/da), total N in the 0-90 cm layer after harvest and fertilizer N residue in the 0-90 cm layer, fertilizer N leached below 90 cm soil, fertilizer lost as denitrification or volatilisation at different N rates and locations.
N Treatments
N0 N1 N2 N3 N Soil
Total fresh tuber yield (kg/da) 2664d* 3586c 3624b 3768a 3545c Total marketable tuber yield
(kg/da) 2442c 3211b 3245b 3460a 3204b
Dry matter (kg/da) Tuber 506e 650c 667b 698a 636d Leaf+vein 758e 975d 1001b 1048a 950c Total 1264d 1625c 1668b 1746a 1589c N uptake (kg N/da) Tuber 8,8d 11,9c 12,0b 14,3a 11,1c Leaf+vein 16,2d 23,1c 27,7b 29,3a 22,0c Total 25,0d 35,0c 39,7b 43,6a 33,1c Ndff % 27,4d 41,8b 45,1a 32,9c kg N/da 9,6c 16,6b 19,7a 10,9c
% NUE 32,0a 27,7b 21,9c 18,2d
Total N (NH4+NO3) in soil at
harvest (kg N/da) 89d 105c 122b 144a 127b
Fertilizer N residue in 0 - 90 cm
soil layer (kg N/da) 8,3d 17,0b 32,8a 14,6c
Fertilizer N lost as denitrification or volatilisation (kg N/da)
11,1d 26,4c 37,5a 34,5b *means followed by the same letter in each row are not significantly different based on a LSD test at P< 0.05.
Potato responded positively to the N rates. This continuous response to the highest N rate suggested that the higher N rate was not sufficient in our drip irrigation + fertigation system and further increase in the N rates may cause additional increase in the yield. However, earlier investigations with potato in the region using sprinkler irrigation showed that 60 kg N/da rate gave the optimum yields (Halitligil et al., 2002).
Nitrogen uptake by tuber leaf+vein were the highest with 90 kgnN/da treatment and the lowest values were obtaineed with the lowest N rate (Table 1). Similar trend was obtained for the nitrogen dreived from fertilizer (Ndff) values.
Lower Ndff values were obtained with 30 kg N/da. Also, Ndff values for the soil application treatment was statistically different from the 60 kg N/da treatments. Percent nitrogen use efficiency (%NUE) values decreased significantly as the N rate increased which was expected. The soil application treatment (NS) gave significantly lower Ndff and NUE values than the equivalent fertigated treatment N2.
Amount of fertilizer N residual in 0-90 cm soil layer was the highest (32.8 kg N/da) for the highest N rate (90 kg N/da). The soil application treatment (NSoil) gave lower fertilizer N residual values than the equivalent fertigated treatment N2, however, highest fertilizer N lost values were obtained from Nsoil treatment (Table1).
Water Use and Water Use Efficiency Data :
The highest ET value (791.2 mm) was obtained from Nsoil treatment, meanwhile the highest WUE value (1.59 kg/da.mm) was obtained from N1 treatment (Figure 1). When the fertilizer is applied on to the soil rather than fertigated higher ET values were obtained.
750 755 760 765 770 775 780 785 790 795 800 N0 N1 N2 N3 Nsoil E T (mm) 1 1,1 1,2 1,3 1,4 1,5 1,6 1,7 WUE ( kg/ da. m m )
ET, mm WUE kg/da.mm
Figure 1. ET and WUE values averaged over locations and years.
Tensionics were installed at 65 and 85 cm in all experiments in 2002 in order to findout if there is movement of water downward in under drip irrigation+fertigation system (Tables 2, 3 and 4) and also to find out if the soil solution taken from them at those depths include 15N labelled fertilizer. Tensiometer reading taken from 65 and 85 cm soil depth did differ very little indicating that almost no water movement had occured below 85 cm depth. It is also obvious from the results given in the tables that at 85 cm depth no residual labelled N fertilizer was found in the soil solution, which clearly shows that under our drip irrigation+fertigation system conditions no nitrogen leaching below 85 cm occured. Therefore, nitrate contamination of ground waters in the region will be prevented if drip irrigation+fertigation system is used.
Table 2. Tensiometer readings obtained at different depths at Institute in 2000. N R a t e S * * D S D S D S D D N O 1 0 0 1 0 3 1 3 8 1 4 1 1 2 9 1 2 8 1 0 5 1 0 6 N 1 1 0 1 9 9 1 5 1 1 4 8 1 4 0 1 3 8 9 8 9 8 0 N 2 1 0 8 1 0 6 1 5 3 1 5 1 1 4 5 1 4 3 9 6 9 7 0 N 3 1 1 0 1 1 1 1 3 9 1 4 3 1 3 9 1 3 9 9 6 9 5 0 N s o il 9 4 9 5 1 4 5 1 4 7 1 3 5 1 3 5 9 0 9 2 0 * S = S h a llo w = 6 5 c m * D = D e e p = 8 5 c m 0 , 0 1 2 0 , 0 2 5 0 , 0 8 9 0 1 : 0 6 S T e n s io m e t e r R e a d in g D a t e s 2 1 . 0 7 . 2 0 0 0 2 3 . 0 8 . 2 0 0 0 2 2 . 0 9 . 2 0 0 0 % N - 1 5 a . e . 2 6 . 1 0 . 2 0 0 0 2 6 . 1 0 . 2 0 0 0
Table 3. Tensiometer readings obtained at different depths at Hasakoy in 2000.
NO 98 100 140 140 131 130 108 110 N1 92 90 141 138 133 135 102 103 0,009 0 N2 98 100 138 140 139 141 98 98 0,036 0 N3 109 109 131 129 140 138 98 98 0,076 0 Nsoil 96 97 133 135 129 130 95 95 0,041 0 * S = Shallow = 65 cm * D = Deep = 85 cm
Table 4. Tensiometer readings obtained at different depths at Suvermez in 2000.
N rate S * D * S D S D S D S D N O 87 88 129 130 135 136 111 114 0 0 N 1 92 90 141 138 133 135 102 103 0,019 0 N 2 98 100 138 140 139 141 98 98 0 N 3 109 109 131 129 140 138 98 98 0,095 0 N soil 96 97 133 135 129 130 95 95 0,055 0 * S = S hallow = 65 cm * D = D eep = 85 cm 28.10.2000 T ensiom eter R eading D ates
% N -15 a.e.
23.07.2000 25.08.2000 24.09.2000 28.10.2000
Dıscussıon
Earlier research with potato in the region using sprinkler irrigation had shown thatnearly 1400 – 1700 mm of irrigation water is needed to obtain 4 tons of marketable potato tubers (Karaca and Demir, 1995; Halitligil et al., 2002). As an
overal average from our experiments and from the farmer yield data for two years, who has used drip irrigation+fertigation system in 5 decar area with IAEA financial supports through TUR/5/020 project, nearly 4 tons of marketable potato tuber yields were produced by drip irrigation + fertigation systems. This shows that 50 % irrigation water is saved, economically this great help for the farmer because they are going to pay less for the irrigation water. Irrigation scheduling experiments must be conducted in the region including the potato varieties.
References
1. Karaca, M. and Demir, Z. (1995) Irrigation and N rate influences to potato tuber yields and inorganic N residue in the soil profile at Cappadocia region. In ‘Ilhan Akalan Soil and Environment Symposium‘ held at Ankara during 27 - 29 September 1995, Ankara Uni. Agricultural Faculty Publications. Ankara. 2. Halitligil, M. B., A. Akın, N. Bilgin, Y. Deniz, K. Öğretir, B. Altınel and
Y. Işık (2000) Effect of nitrogen fertilization on yield and nitrogen and water use efficiencies of winte wheat (durum and bread) varieties grown under conditions found in Central Anatolia. Biol. Fertil. Soils 31: 175-182.
3. Halitligil, M.B., A. Akın, A. İlbeyi (2002) Nitrogen balance of nitrogen-15 applied as ammonium sulphate to irrigated potatoes in sandy textured soils. Biol. Fertil. Soils 35 : 369-378
4. Papadopoulos, I. (1988) Nitrogen fertigation of trickle-irrigated potato. Fertilizer Research. 16: 157-167.
5. Steel, R.G.D. and Torrie, J.H. (1960) Principle and procedures in statistics. McGraw Hill, NewYork, 481 p
