Document Type : Original Article

Authors

• Hamid Reza Bagheri ¹
• Mohammad Hosein Gharineh ²
• Abdolmehdi Bakhshandeh ³
• Javad Taei ⁴
• Abdolmohammad Mehnatkesh ⁵
• Bahram Andarzian ⁶

¹ PhD student of Agronomy, Ramin University of Agriculture and Natural Resources, Khuzestan

² Associate Professor, Department of Agronomy, Faculty of Agriculture, Ramin University of Agriculture and Natural Resources, Khuzestan, Iran

³ Professor, Department of Agronomy, Faculty of Agriculture, Ramin University of Agriculture and Natural Resources, Khuzestan, Iran

⁴ Assistant Professor, Faculty of Agriculture, Jiroft University, Iran

⁵ Assistant Professor of Chahar Mahal va Bakhtiari Research Center of Agriculture and Natural Resources, Iran

⁶ Assistant Professor of Khuzestan Research Center of Agriculture and Natural Resources, Iran

Abstract

 
Introduction
Potato (Solanum tuberosum L.) is one of the most important crops that plays a major role in feeding the world. The growing demand for potato, as both a fresh and processed food, along with the increase in world population, mean that yield will have to be improved through some combination of germplasm enhancement, better crop protection and more efficient and productive management of irrigation and fertilization (Haase et al., 2007). Researches have proved potato is sensitive to drought stress at all stages of growth, especially at tuber formation stage due to reduction of leaf area and photosynthesis (Fabeiro et al., 2001; Ayas, 2013; Shock et al., 2013). Abiotic stress factors, such as drought, have severe, adverse effects on potato growth and yield. In particular, a regular water supply is necessary to achieve a high quality yield (Ierna and Mauromicale, 2006). In comparison with other species, potato is very sensitive to water stress because of its shallow root system (Ayas, 2013).
Water shortage during tuber differentiation can delay growth and reduce earliness, whereas during tuber growth and bulking can decrease tuber size and have a drastic effect on yield (Alva et al., 2012; Liu et al.; 2006; Ayas, 2013).
For processing potato, a careful N and water management is required to ensure regular growth, high dry matter content and marketable tubers (Shock et al., 1998; Zhang et al., 2006; Shahnazari et al., 2007).
So this research was done to evaluate effects of different levels of water deficit and nitrogen fertilizer on tuber yield, yield components and water use efficiency of potato crop in Chahar Mahal va Bakhtiari province, in Iran.
Materials and methods
In order to study the effects of different levels of water deficit and nitrogen fertilizer on tuber yield and other agronomic traits of potato crop (Boren variety), a split plot experiment based on randomized complete block design, conducted at Chahar Mahal va Bakhtiari Research Center of Agriculture and Natural Resources, in 2013. The levels of water deficit were S₁, S₂ and S₃ (100, 75 and 50% of the water requirement of potato crop after emergence by the end of the growing season, respectively), as the main plots and nitrogen fertilizer treatments were N₁, N₂, N₃ and N₄ (100, 66, 33 percent of plant nitrogen requirement and without nitrogen consumption, respectively) as sub plots.
Results and discussion
In this experiment water deficit had decreasing effect on tubers dry matter percent but nitrogen changes had no distinct effect on this trait. By applying water deficit and decreased levels of nitrogen, the number of tubers per plant and the average tubers weight also fell. The greatest and the lowest number of tubers per plant were seen at S₁ and S₃ treatments (8.4 and 7.4 respectively). The maximum weight of tubers observed at full irrigation treatment (118 g) that had no significant difference with S₂, but at treatment S₃ (50% of the water requirement), tubers were produced lighter with an average weight of 86.6 grams. So it can be concluded, in this irrigation regime, the average weight of tubers is closer to weight of seed tuber class. Many studies have confirmed these findings (Fabeiro et al., 2001; Ayas and Korukcu, 2010; Ayas, 2013).
The results showed that maximum tuber yield gained from S₁ treatment (55.9 ton/ha) that had no significant difference with S₂, but intensive drought stress (S₃) produced minimum tuber yield (31.7 ton/ha). N₁ and N₂ treatments led to highest tuber yield but the lack of nitrogen (N₄) caused the lowest tuber yield (38.7 ton/ha). Generally, in S₂ and S₃ drought stress levels, N₂ produced maximum tuber yield. The reduction of tuber yield in S₂ and S₃ treatments within increment of nitrogen consumption (N₁), caused the significant interaction between drought stress and nitrogen on tuber yield.
Ierna and Mauromicale (2006) reported that water deficit stress as much as 50% of the water requirement, had increased stomatal resistance and caused the reduction of leaves photosynthesis, biomass, tuber growth and tuber yield. Demelash, 2013; Alva et al., 2012 and Ayas, 2013 studies also confirm the results of this Research.
The second level of nitrogen (N₂) in S₃ treatments led to maximum, but S₁N₄ led to minimum water use efficiency (9.21 and 5.24 kg/m³ respectively). Liu et al. (2006) reported, by reducing the amount of irrigation volume, tuber yield decreases baut water use efficiency will increase.The stepwise regression analysis showed that the average tuber weight explains most changes of marketable tuber yield per plot.
Conclusions
Based on the results of the present study, since there is no statistical difference in tuber yield, between S₁ and S₂ irrigation regimes, it is recommended that for proper utilization of water resources and achieve economic yield, potato crop, produce with 6400 m³ water per hectare with irrigation at 7 days period. Results showed, at S₂ irrigation regime, N₂ Treatment (consumption of 270 kg Urea/ ha) had produced the highest yield, so S₂N₂ treatments is the best option for potato crop production.

Keywords

• Boren
• Dry matter
• Interaction
• Irrigation regime
• tuber weight