Agro ecological requirements for growing pistachio trees A Literature Review
Pistachio is one of the most important export and strategic agricultural product in the word and comprehensive study on its agro ecological requirements can lead to find out the suitable areas for producing pistachio as well as addressing the best management practices to achieve the sustainability. This paper tries to review agro ecological requirements (climate, soil and site) for pistachio after describing the role and the limitation levels of the climatic, landscape and soil properties that influencing on the yield and quality of the pistachio trees and their nuts, respectively. (c) 2016 Elixir All rights reserved. Elixir Agriculture 96 (2016) 41450 41454 Agriculture Available online at www.elixirpublishers.com (Elixir International Journal) Ardavan Kamali and Alireza Owji/ Elixir Agriculture 96 (2016) 41450 41454 41451 In the both cases, consideration of pistachio water requirement is in high importance for the land suitability evaluation of pistachio. 1.2. Chilling requirement A minimum period of low temperatures which is required by pistachio trees to their fruit set be successful called as the chilling requirement (Beede et al. 2005) The ranges of chilling requirement for pistachio trees are between 500 to 1000 cumulative hours below 7.2 degC depending on the trees' age, location and even cultivars (Kuden et al. 1994; Beede et al. 2005) If the climate at the selected region does not fulfill optimal accumulation of chilling hours, yields will be negatively affected (Kuden et al. 1994) Some researchers have reported inadequate cumulative chilling hours as a constant problem to produce pistachio in Kerman provinces during considered years (Javanshah et al. 2005) Elevation above the sea level is one of the main factors to receive enough chilling hours for pistachio. The elevations between 1000 to 3000 m above sea level are suitable for regions with mild climates (Faust, 1989) Another important factor effects on the chilling requirement for pistachio is the latitude of the allocated area. The less the latitude of that region is, the more elevations will be needed. In areas with lower latitudes, trees do not go through complete dormancy (Faust, 1989) Furthermore, the occurrence of shadow or foggy weathers causes the dormancy of the blossoms to break sooner, especially blossoms of plants with higher chilling requirement. It is probable that in shadowy or foggy weathers, the chilling requirement is fulfilled better because of the lower temperature (Erez, 2000) 1.3. Radiation Radiation influences, together with temperature, on the rate of photosynthesis. The photosynthesis process provides plants with assimilated substances that are necessary for its growth (Sys et al. 1991) All plants, however, do not need sunshine to the same extent. Some of them require minimum and some need maximum rates of sunshine. In terms of sensitivity to sunshine, pistachio is categorized as a sun plant (Javanshah et al. 2005) 1.4. Temperature Temperature generally determines the rate of plant growth (Sys et al. 1991) Plants are different in the optimum ranges of temperature they tolerant to various winter and summer air temperatures as well. Cold winters and hot dry summers with 2200 to 2800 heat units are required by pistachio (Ferguson et al. 2005a; Ferguson et al. 2005b) However, spring frost can kill flowers and young leaves. Although pistachio can easily tolerate the temperature as low as 20 degC in winter and as high as about 45 degC in summer (Javanshah et al. 2005) both extreme (low and high) temperatures, and low annual rainfalls, were considered as the two major constraints to pistachio growth in Turkey (Sykes, 1975) The optimum temperature for pistachio has been reported between 25 and 35 degC (Ferguson, 2003; Ferguson et al. 2005a; Ferguson et al. 2005b) 2. The role of landscape and soil factors on pistachio yield Landscape and soil are the other main parameters influencing on agricultural land utilization types. Slope, drainage and flooding play important roles on success or failure of a specific land uses. Slope determines directly the irrigation system (i.e. surface or sprinkler) and land management practices (i.e. mechanized or traditional) to be applied in desired land utilization types (Sys et al. 1991) For instance, the surface and sprinkler irrigation systems are not applicable in slopes more than 6 to 8 and 25 percent, respectively (Dent and Young, 1981; Sys et al. 1991; Soil Survey Staff, 1993) Moreover, the use of machinery to manage agricultural land uses is not possible in slopes more than 12 percent without land tracing because of the difficulty of tillage practices (Dent and Young, 1981; Sys et al. 1991; Soil Survey Staff, 1993) It also indirectly effects on land properties like vegetation, air temperature and depth to water table (Buol et al. 2011) Good and perfect soil drainage classes tougher with the deep water table (i.e. locating deeper than 1.5 m from the soil surface) are essential land qualities for almost all perennial plants to reach the optimum yield with high quality (Dent and Young, 1981; Sys et al. 1985; Sys et al. 1991; Soil Survey Staff, 1993) Flooding is also one of the land qualities associated to land form that certifies the consistency of the crop planted in a certain land and the settled infrastructures instruments (Sys et al. 1985) Although various plant types show different tolerance to characteristics related to the landscape, many researchers (Storie, 1933; Sys and Verheye, 1974; Dent and Young, 1981; Sys et al. 1985; Sys et al. 1991; Soil Survey Staff, 1993) have suggested the same limitation levels for most of the fruit trees in respect to the impact of the landscape factors. These limitations have similar effects on the growth and management of pistachio trees as well. Among soil characteristics, the percentage of coarse fragments has similar effect on crop production and farm management in the most of the fruit trees like pistachio trees since the coarse fragments make tillage problems and decrease the water and nutrient retention capacity (Storie, 1933; Sys and Verheye, 1974; Dent and Young, 1981; Sys et al. 1985; Sys et al. 1991; Soil Survey Staff, 1993) Hence, no specific limitation level is necessary to be considered for assessing the influence of coarse fragments on the pistachio yield. The other important soil characteristics for pistachio production, has been described as follow. 2.1. Soil texture Soil texture is one of the most important factors to determine land suitability for almost all crops (Storie, 1933; Sys and Verheye, 1974; Dent and Young, 1981; Sys et al. 1985; Sys et al. 1991; Soil Survey Staff, 1993) This soil property influences on availability of water and nutrient in soil as well as soil management practices. Fine texture soils are often preferred for allocating to agricultural lands because of their high cation exchange and water holding capacity (Brady and Weil, 2007) However, these soils encounter generally with the decrease in infiltration of water into the soil. In severe conditions water ponding occurs around the roots and causes aeration problems for plants (Hillel, 1998, 2003) Moreover, high water holding capacity in these soils increases the probability of fungal diseases invasion to the pistachio roots (Jaime Garcia and Cotty, 2006) Another problem in soils with heavy texture is the volatilization of the N fertilizers (Power and Prasad, 1997; Havlin et al. 2005) High clay contents as a major limiting factor in soil of the pistachio orchards in some parts of Kerman province, south east Iran have reported by some researchers (Hosseinifard et al. 2005; Hosseinifard et al. 2010) In the other hand, the low cation exchange and water holding capacity in coarse texture soils are the main problems of such soils that lead to leaching of essential nutrients as well as drought stress (Brady and Weil, 2007) Nevertheless, different soil textures are required by various plants. Pistachio trees like any other crops can survive in wide ranges of soil texture (Ferguson et al. 2002; Ferguson, 2003; Goldhamer, 2005; Ferguson et al. 2005a; Ferguson et al. 2005b) However, sandy loam is preferred by Ardavan Kamali and Alireza Owji/ Elixir Agriculture 96 (2016) 41450 41454 41452 them for high quality yield production (Ferguson et al. 2002; Ferguson, 2003; Goldhamer, 2005; Ferguson et al. 2005a; Ferguson et al. 2005b) 2.2. Soil salinity and sodicity Salinity is mainly considered as an important soil limitation because of its inverse effects on the plant growth and yield quality. Such problems occur as results of the soil osmotic pressure induced water stress and specific ion toxicity that endangered the plants life (Zhu, 2001; Lee et al. 2004; Kao et al. 2006) Despite pistachio is a common crop of arid and semiarid regions with saline soils, many researchers have been illustrated that salt stress has an inhibiting effect on its growth and development because of the reduction in photosynthesis, respiration, protein synthesis and consequently decrease of biomass production especially in sensitive species (Boyer, 1982; McKell, 1994; Ungar, 1996; Khan et al. 2000a, 2000b; Pal et al. 2004; Mehari et al. 2005) Pistachio trees, however, are able to tolerate higher amounts of soil salinity than the other similar fruit trees. As laboratory and farmlands researches (Ferguson, 2003; Sanden et al. 2004) have been shown, pistachio trees can be irrigated by water with 8 dS/m electrical conductivity without any remarkable decrease in the yield. Moreover, Sanden et al. (2004) have pointed out that soil electrical conductivities up to 6 dS/m exert no limitation to the pistachio growth, but raising the soil electrical conductivity to 8 dS/m declines about 50 percent of the pistachio yield. Beside the soil salinity, high amounts of sodium ions in soil solution that is lead to high exchangeable sodium percentage (ESP) or sodiu