Iran's Land Suitability for Agriculture

Abstract

Increasing population has posed insurmountable challenges to agriculture in the provision of future food security, particularly in the Middle East and North Africa (MENA) region where biophysical conditions are not well-suited for agriculture. Iran, as a major agricultural country in the MENA region, has long been in the quest for food self-sufficiency, however, the capability of its land and water resources to realize this goal is largely unknown. Using very high-resolution spatial data sets, we evaluated the capacity of Iran's land for sustainable crop production based on the soil properties, topography, and climate conditions. We classified Iran's land suitability for cropping as (million ha): very good 0.4% (0.6), good 2.2% (3.6), medium 7.9% (12.8), poor 11.4% (18.5), very poor 6.3% (10.2), unsuitable 60.0% (97.4), and excluded areas 11.9% (19.3). In addition to overarching limitations caused by low precipitation, low soil organic carbon, steep slope, and high soil sodium content were the predominant soil and terrain factors limiting the agricultural land suitability in Iran. About 50% of the Iran's existing croplands are located in low-quality lands, representing an unsustainable practice. There is little room for cropland expansion to increase production but redistribution of cropland to more suitable areas may improve sustainability and reduce pressure on water resources, land, and ecosystem in Iran.

Figure 1

Iran’s land suitability for agriculture based on soil and topographic variables. See Table 3 for the definitions of suitability classes. Map was generated using QGIS 2.18.

Figure 2

Edaphic and topographic constraints of agriculture in Iran. Geographical distribution of the limiting soil and topographic factors for lands classified as unsuitable, very poor, and poor as shown in Fig. 1. Suitability > 0.4 refers to as medium, good, and very good lands (see Table 3). Acronyms: Cation Exchange Capacity, CEC; Organic carbon, OC; Base saturation, BS; Exchangeable Sodium Percentage, ESP; Available Water Content, AWC. Map was generated using QGIS 2.18.

Figure 3

Spatial distribution of the length of the growing period (months) in Iran. Length of moist growing period was defined as the number consecutive months wherein precipitation exceeds half the PET (see Table 2 for source of data and Methods for more details). Map was generated using QGIS 2.18.

Figure 4

Land suitability for rainfed agriculture. Iran’s land suitability with potential for rained agriculture was assessed based on soil properties, terrain, and a minimum precipitation threshold of 250 mm year⁻¹. See Table 3 for the definitions of suitability classes. Map was generated using QGIS 2.18.

Figure 5

Land suitability based on precipitation scaling method. Iran’s agricultural land suitability based on soil properties, terrain, and climate conditions. In this analysis, the suitability of land increases with annual precipitation over the range of 100 to 500 mm year⁻¹ (see Methods for details and Table 3 for definition of suitability classes). Map was generated using QGIS 2.18.

Figure 6

Land suitability of existing croplands. Distribution of Iran’s agricultural lands (cultivated or uncultivated) among different suitability classes corresponding to Fig. 6. Left figure shows the percentage of the land within each of the suitability classes that have been used for cropping. The donut chart (right) shows the proportion of Iran’s total agricultural area that falls within each suitability class. The slope, intercept, and R² values for the linear regression model (dashed line) are 108.8, 6.2 and 0.98, respectively.

Figure 7

Rainfed wheat yield as related to land suitability. Georeferenced data on rainfed wheat yield in Iran, obtained from FAO, showed a linear relationship with land suitability values. The slope, intercept, and R² values for the linear regression model (dashed line) are 1.46, 0.12 and 0.98, respectively.