An ASABE Meeting Presentation DOI: 10.13031/aim.20162460172 Paper Number: 162460172
Tuber yield, irrigation water use efficiency and starch content of two potato varieties as affected by drip tape and solid set irrigation systems Behnaz Molaei, Former graduate student Department of Water Engineering, College of Agriculture, Isfahan University of Technology Isfahan, 84156-83111, Iran, e-mail:
[email protected]
Mahdi Gheysari, Assistant professor Department of Water Engineering, College of Agriculture, Isfahan University of Technology Isfahan, 84156-83111, Iran, e-mail:
[email protected]
Behrouz Mostafazadeh-Fard, Professor Department of Water Engineering, College of Agriculture, Isfahan University of Technology Isfahan, 84156-83111, Iran, e-mail:
[email protected]
Esmaeil Landi, Instructor Department of Water Engineering, College of Agriculture, Isfahan University of Technology Isfahan, 84156-83111, Iran, e-mail:
[email protected]
Khashayar Molaei, Former under-graduate student Department of Water Engineering, College of Agriculture, Isfahan University of Technology Isfahan, 84156-83111 Iran, e-mail:
[email protected]
Written for presentation at the 2016 ASABE Annual International Meeting Sponsored by ASABE Orlando, Florida July 17-20, 2016
Abstract. Iran’s potato production in arid areas mainly relies on groundwater that is being discharged by long-established and extensive sprinkler irrigation systems across the region. Within the past few years, drought, excess withdrawal, and slow recharging processes have all contributed to a rapid and drastic decline in the groundwater levels. Under these circumstances, drip tape irrigation (DTI) can be considered as a possible alternative. The objective of this study was to evaluate and compare the effects of solid set portable sprinkler (SS) and DTI systems on the irrigation water use efficiency (IWUE), tuber yield (TY), and growth characteristics of two potato varieties of Satina and Burren. A randomized complete block design experiment with three replications was applied during the 2011-2012 growing season at Isfahan, Iran. Results indicated that the DTI system in comparison with SI system, consumed 16% less water and produce 37% more tuber yield. IWUE for the DTI and the SS systems were 3.83 kg m-3 and 1.95 kg m-3, respectively, which the difference was statistically significant. The DTI increased the shoot height (SH), root dry matter (RDM), and root length (RL) by 11, 34 and 35% respectively. The microclimate under the SS system not only delayed the germination by 9 days, but also prolonged the growing season due to its effect on increasing the required cumulative growing degree days (GDD) at each growing stage. The drip tape irrigation can be considered as a good alternative irrigation system for potato production in the arid regions. Keywords: Arid region, Drip irrigation, Irrigation water use efficiency, Potato, sprinkler, Yield.
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2016 ASABE Annual International Meeting Paper
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Introduction Iran is located in arid and semiarid regions and because of water shortage, the great challenge for agricultural development is to use less water to produce more food (FAO, 2009; Gheysari et al., 2015). Lack of rainfall and insufficient surface water flows reduces groundwater resources (Mosaedi et al., 2015). About 52 percent of agricultural lands in Iran are irrigated and about 62 percent of these lands are using groundwater for irrigation (FAO, 2009). Most of over-exploitation occurs in the central basins of Iran like Isfahan province where less water is available. Sprinkler irrigation is the most widely accepted method in Iranian agricultural fields (Gholamrezai et al. 2014; Gheysari et al., 2009), but because of drought and lower recharge of water resources, drip tape irrigation can be a profitable alternative method of irrigation. Potato production ranks fourth in the world after rice, wheat and maize. Iran, ranks 11th among potato grower countries in the world (FAOSTAT 2012). Although potato seed with high quality is the basic factor which affect potato yield, application of fertilizers, irrigation and appropriate crop management could be more effective to increase productivity (Wang 2008). Potato productions have been studied for different irrigation systems and irrigation regimes under different soil and climate conditions. Many studies on potato productions using different irrigation systems such as furrow and drip (Akhavan et.al. 2007), drip and solid set sprinkler (Shalhevet et. al.1983; Yavuz et. al. 2012; unlu et. al. 2006), surface and subsurface drip (Hosam and Hiekal. 2009) have conducted in different parts of world. Also different irrigation strategies such as deficit irrigation (Ierna et.al.2011) deficit and partial root zone drying (Ahmadi et. al. 2010) were applied for potato production. Recent studies on the effects of sprinkler irrigation system on crop microclimate (Liu and Kang. 2006; Olanya et. al. 2007) and on soil surface sealing and its effects on infiltration (Lehrsch and Kincaid. 2010; Ragab, 1983) have been reported. Potatoes fields in Isfahan province are primarily irrigated with long-established sprinkler irrigation. Because of lack of adequate water in semi-arid regions such as Isfahan, it is better to compare different irrigation systems for potato production and select suitable irrigation system with high water use efficiency. The objective of this study was to compare the effect of drip tape irrigation (DTI) and solid set sprinkler irrigation system (SS) on tuber yield and yield characteristics of two potato varieties of Burren and Satina.
Material and methods: Site description and experimental design: This study was conducted in 2011-2012 growing season at Molaei Agro-Industry Coorporation in Shahreza, Isfahan province, located in the central part of Iran (31º 47ʹ 44.62ʺ N, 52º 00ʹ 33.86ʺ E, 1986 m a. s. l). The field has uniform slope and the soil texture was clay loam up to a 90 cm depth. Soil chemical and physical properties of the experimental field are summarized in Table 1. The region has a dry climate with moderate summer and cold winter. The average annual precipitation is 144 mm which most of the precipitation occur during autumn and winter. Soil depth (cm) 0-30 30-60 60-90
Sand % 31 35 37
Table 1: Soil chemical and physical properties of experimental field Silt Clay EC OC N Soil texture pH % % dS/m % % 32 37 Clay Loam 4.3 7.6 0.73 0.065 28 37 Clay Loam 32 31 Clay Loam -
P % 12 -
K % 245 -
The experimental field was 4032 m2. Experimental variables were two irrigation systems, solid set sprinkler irrigation systems (SS) and drip tape irrigation systems (DTI) and two potato varieties of Burren and Satina. Four treatments were arranged in randomized complete block design with three replications. The dimension of each experimental plot was 12 m by 28 m. The two potato varieties of Burren and Satina were early and semi-early varieties with S and SE class seeds which were imported from Ireland and Germany, respectively. They were selected for this project because of good marketing and high demand in Iran. The potatoes were cultivated on 20 July 2011. Each plot consisted of 14 rows with 75 cm row spacing and 20 cm plant spacing on the rows. Fertilizer Management Nitrogen, potash and phosphorus fertilizer demand were determined based on soil test results and local fertilizer recommendations. Nitrogen, potash and phosphorus were applied uniformly in the field before potato sowing. Nitrogen in the form of urea (46% N) at a rate of 100 kg ha-1, potassium sulfate (44% potash) at a rate of 200 kg ha-1 and triple superphosphate (TSP) (46% phosphate) at a rate of 200 kg ha-1, respectively. Fertigation was applied six times during the growing season. Ammonium sulfate (21% N, 24% S) was applied three times at 30, 2016 ASABE Annual International Meeting Paper
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55 and 64 days after planting (DAP) at a rate of 82, 82 and 41 kg ha-1, respectively. Sangral urea phosphate (18% urea and 44% P2O5), urea (46% N) and NPK (20-20-20) were applied at 64, 70 and 74 DAP at a rate of 41, 82 and 41 kg ha-1, respectively. For fertigation, the fertilizers were mixed with water in a tank with1000 liters capacity and then it was injected to sprinkler or drip tape irrigation system. After finishing the fertilizer application, irrigation was continued with only sufficient water to remove fertilizer from pipes. The coefficient of distribution uniformity and the efficiency of the systems were computed to evaluate two irrigation systems. Irrigation management The sprinkler irrigation system in this project was a part of long established solid set sprinkler system in the field with triangular arrangement, set at a 28 m by 24 m spacing. The sprinklers were used with full rotation (360º). Risers’ with height of 1.0 m were used from beginning to the end of the growing season. In order to control the amount of irrigation, volumetric flow meters were installed on the manifold pipes of irrigation system. The plots that were irrigated with DTI were also part of long established SS which changed to DTI for this experiment. All DTI plots were irrigated at the same time. Drip-tapes (made in Iran) were placed on each plant row with dripper’s space of 20 cm. A 2.7 liters per hour flow rate was maintained for each dripper at 1 atm pressure. The diameter and nominal thickness of drip tape were 16 mm and 175 microns, respectively. All of the plot were irrigated based on soil moisture requirement 42 DAP considering distribution uniformity (DU) of 75% and 89% for sprinkler and drip-tape irrigation systems, respectively. The DU was measured in the experimental field. Irrigation scheduling, including timing and amount of each application, was based on the daily soil moisture balance measurements (Gheysari et al. 2009). Soil moisture was measured at soil depths of 10, 20, 30, 40, 60 and 100 cm with the PR2 profile probe (Delta-T Devices Ltd, UK). The soil moisture at potato root depth of 40 cm, was used for irrigation scheduling. In both irrigation systems, time of irrigation was estimated based on management allowed depletion (MAD) equal to 40±4 % for full irrigation without stress (Allen et.al. 1998). Irrigation was applied when the weighted averaged volumetric moisture content in the root zone of each irrigation treatments reached θIR as describe by the following equation (Gheysari et al. 2015; Kiani et al. 2016): n
θ IR =
∑ [θ i =1
FC i
− (θ FC i − θ PW Pi ) × MAD ] × D i
(1)
n
∑D i =1
i
Where, θFC is soil moisture content at field capacity (m3/m3), θPWP is the soil moisture content at wilting point (m3/m3), MAD is management allowed depletion equal to 40±4 % in this study, Di is the thickness of each soil layer (m), and n is the number of soil layers in the root zone. The irrigation frequency during the growing season varied due to the crop requirement. The irrigation depth was calculated based on the amount of water required to replenish soil water depletion for the FC point (Allen et al., 1998). The net irrigation depth was assumed equal to SMD at irrigation time (Gheysari et al. 2015; Kiani et al. 2016):
SMD=
n
∑ [θ i =1
FC
− θ BI )i × D i
(2)
Where, θBI is soil moisture content before irrigation time (m3/m3). Growing degree days Growing degree days was calculated (McMaster and wilhelm 1997; Worthington and Hutchinson 2005) by the following equation:
= GDD
n
T max +T min ) −T base ]i 2
∑ [( i =1
(3)
Where, Tmax and Tmin are maximum and minimum temperature of day in ºc; Tbase is degree for days temperature which is 7ºc for potato. Crop measurements Three plants per treatment were sampled at physiological maturity stage (95 DAP) to measure plant 2016 ASABE Annual International Meeting Paper
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characteristics of different treatments. Shoot height (SH) was measured, the shoot (stem and leave) oven-dried at 85ºc for 24 h and root at 60 ºc for 24 h (Ahmadi et.al. 2010) to measure shoot dry mass (SHD) and root dry mass (RDM), respectively. Root length (RL) was measured with Delta-T Scanner and the starch was measured in dry matter (STDM) (Aman and Hesselman, 1984). The total harvest was done on November 10th in 2011. Each plot was harvested thoroughly and the potato yield per plot was weighted separately.
Results Effect of irrigation systems and potato varieties on TY, IWUE and STDM Results indicated that tuber yield (TY) and irrigation water use efficiency (IWUE) were significantly affected by irrigation systems (p
