• Soil Fertility
SOIL FERTILITY REPORT: SHIRAZ, IRAN
prepared by: E. June Narber
Shiraz: General Facts
Shiraz, Iran is located in the south west part of Iran, near the Khuzistan Plain (which is an important agricultural area in Iran). The Persian Gulf is approximately 200 kilometers south. The population of Shiraz is 848,289. It is located at an altitude of 5,200 feet and 1000-2000 m elevation above sea level. The average winter temperature is 48 degrees Fahrenheit. Winters are mild, but summers are intensely hot and dry. The mean annual precipitation is 330 mm with the majority falling in the winter months of November through March (Mahjoory and Gharaee 1984:1115).
Common Characteristics of Soils in Region
Shiraz is located in an area that is called the Lowland Alluvial Plain. The soil is arid to semi arid, as is about 90% of the land in Iran . The soil is classified as an Aridisol.
It is in one of oldest and most stable geomorphic surface areas in the country (Mahjoory and Gharaee 1984:1115). Limestone rock outcrops are typical. Dark brownish-colored limy gravel occur on the surface and in the soil. The soil is well drained and calcareous though out the carbonate concretions, nodules, and powdery pockets present.
The Lowland Alluvial Plain is a product of deposition of thick, highly calcareous, fine textured Kor River alluvium (Mahjoory and Gharaee 1984:1115).
X-ray analysis indicated that the clay mineral components of the soil consisted of some discrete vermiculite, chlorite, clay mica (illite), and kaolinite. Vermiculite and clay mica are the major clay components in the soil (average vermiculite content of soil is 42.4%). The amount of clay mica decreases with the depth of the soil. The Cation Exchange Capacity (CEC) is 23.2 meq/100g of soil. ( Mahjoory 1975:1163).
Potential Environment/Soil Limiting Factors Influencing Crop Production
Iran lies in one of the worlds major earthquake zones (World Book 1995:400). The weather affects potential crop yields as summers are intensively hot, with little rainfall. Without irrigation being practiced, agriculture would be near impossible (McLacklan 1988:19). Hot, sand-laden winds are a problem as well. The soil in the area, being an aridisol and possessing a high bicarbonate content, is an obstacle for crop production.
Calcic (aridisols) are horizons of secondary carbonate enrichment that are >15 cm thick. Aridisols have the least depth of horizon and total pedon development of all the potential (geographic) soils (Steila and Pond 1980:107). The salts present in the soil consist of cations of calcium, magnesium, sodium, chloride, and sulfate anions. The soil also is low in organic matter and nitrogen content. The salts can cause an excessive leaching of soluble materials. Root systems in this type of soil are usually very few in number and very fine. To correct the saline accumulations in soil, general practices include: installing drainage facilities; subsequent application of surface water which might remove harmful salts through leaching; and subsurface draining (Steila and Pond 1980:112). Soil pH is at an average of 8.0. As soil pH is correlated with precipitation, soil around Shiraz tends to be alkaline or neutral. Calcareous soils have a maximum pH of about 8.3 when they are in equilibrium with the normal CO2 (Foth and Ellis 1988: 38). Ca, Mg, K, and Ha dominate the exchange site, with Ca having the most adsorption and N the least.
One of the largest problems facing agricultural/crop production in this area is the severe lack of water. As mentioned, irrigation is the most valuable tool to crop production. Water shortages, potential water sources for the future, and present water scarcity are ongoing discussions in relevance to crop yield. I would suggest that along side of my soil fertility plan, is research to better develop irrigation and potential water resources for this area. Without water, perfect soil fertility balancing is worthless for crop production.
Major Economic Crops
Wheat and Barley are grown on 75% of the cultivated land in Iran. Sugarbeets, fruit, maize, dates, cotton, tobacco, nuts, and tea are popular crops. The highest economic yielding crops are wheat, barley, sugarbeets, rice, soybeans, and maize. Maize is a relative newcomer crop to this area. As a country, Iran is becoming more aware of the need to be self-sufficient in feeding her people. Crops grown strictly for economic gain are no longer the main focus. Agricultural exports account for approximately 12% of the GNP. I choose to examine the soil fertility requirements for further production of the crops of maize (corn) and soybeans.
Special Production/Ecological Needs of Maize and Soybeans
Maize (Zea mays) is a summer crop in Iran. It can germinate in a wide range of temperature extremes and flourishes in almost any combination of soil and climate. Hybrids that have been developed can thrive in water reduced areas. Hybrids do not transmit their increased vigor to offspring, so parent stocks must be crossed each year to produce a new crop of hybrid seed.
Nitrogen is one of the most important nutrients for grain corn. Large amounts of it must be applied. The rate of nitrogen fertilizer is determined by the expected yield goal. Phosphorous is needed for building strong stalks. Sulfur deficiencies occur on soils with low organic matter. If soils are excessively alkaline, the phosphorus should be added as close to planting time as possible (Kimbrough and Blaine). Water drainage needs to be good.
Soybeans (Glycine max) are approximately 40% protein. An increase in soybean production can help Iran become more self-sufficient in its food production. Because soybeans are so nutritious and can be processed into a variety of edible forms, such as dried and ground into flour, they are an ideal crop to focus on in this report.
Soybeans grow best on soils of medium to high fertility with a favorable pH. High soil fertility reduces risks from weather stresses. Acid soil proves fatal for soybeans, and since Shirazs soil is more alkaline, the soil is safe for soybean growth. Lime content is important, as well as enough phosphorous and potassium. It is recommended to use a generous amount of plant food for high soybean crop yields. For example, a 30 pound yield removes 24 pounds of phosphate and 42 pounds potash in the seed alone. High crop yields will bring down soil fertility levels rapidly, so additional fertilizer must be added with each seasonal crop. Soybeans have a low need for nitrogen.
Recommendations for Soil Fertility of Corn Crops
As nitrogen is an important ingredient in corn production, it is recommended that nitrogen levels in the soil be closely monitored and sufficient nitrogen be added prior to planting corn or at the time of the corn planting. Working on the water drainage of the field may have to be a consistent effort, but a worthwhile one to ensure a high crop yield.
Zinc fertilizers applied to calcareous soils are not absorbed by the first crop and may affect the growth and chemical composition of subsequent crops (Kariman and Yasrebi 1995:277). Therefore it is recommended to add zinc as ZnSO4 X 7H2O. Zinc is removed from the solution in carbonate-containing soils through the formation of ZnS04. Addition of Sulfur to the soil is also necessary for corn crops.
Recommendations for Soil Fertility of Soybean Crops
Manganese becomes a limiting factor of plant growth in some soil conditions. High pH and abundance of free calcium carbonate in calcareous soils are conducive to Mn-deficient plants. Application of Mn increases dry matter yield of soybean crops (Ahangar, Kariman, and Abtahi 1995:1449). The Mn does not remain well in the soil, and must be reapplied every crop season. Additions of lime, phosphorus, and potassium are recommended as well to increase soybean yield by maintaining high soil fertility. Soil tests should be taken in every potential crop area to obtain the exact amounts of needed fertilizer to correct the nutrient deficiencies. Soybeans should be planted 2.5 cm deep in the soil.
Improvement of Agricultural Production Via A Fertility Plan
It is my recommendation to the nation of Iran that the focus for the agricultural future be on new crops, especially genetically altered hybrids, such as corn, that can do well in aridisol soils. Through consistent soil testing, and necessary additions to the soil for the projected crop/estimated yield, more of the Lower Alluvial Plain area can be developed for agriculture. As much of the eastern and north eastern areas of the country are desert, and the heavily forested areas of the west make agricultural development difficult to near impossible, it is important to focus on the land that has the highest developmental potential. The area surround Shiraz (+/-100 KM) is among the best choices. Fruit crops are encouraged to continue in this area, but as fruit trees can only produce a given amount of fruit in certain seasons, soil based agriculture has the best potential for increased food production, as there are summer and winter crop potentials (currently being implemented). It is the goal of this fertility plan to focus on the potential of growing more crops of corn and soybeans in this area. In addition, it is recommended that the traditional crops be maintained at certain percentages.
Because water shortage is the most pressing problem for Iran, I recommend that new water resources be found, and more irrigation systems be set up. As more water becomes available, more crops can be produced.
Futuristic crop yields can be projected through the creation of greenhouse "farms". Through this laboratory type of environment, soil fertility can be more easily controlled, and the environmental issues, such as wind and heat can be climatically controlled in an artificial
environment. As this is a current research project I am undertaking, I mention it in this report only as an introductory measure. Because of financial limitations, it is understood that the Iranian government/economy could not support such a project at this time. But in the future, perhaps through this sustainable environment, crops can be produced with ease to meet a populations food requirements.
Ahangar, A. Gholamalizadeh, N. Kariman, and A. Abtahi. 1995 "Growth and Manganese Uptake By Soybean In Highly Calcareous Soils As Affected By Native and Applied Manganese and Predicted By Nine Different Extractants" IN Communications In Soil Science and Plant Analysis; Volume 26 (9 & 10); pages 1441-1454.
Foth, Henry D. and Boyd G. Ellis. 1988 Soil Fertility; New York; John Wiley and Sons.
Kariman, N. and J. Yasrebi.1995 "Prediction of Residual Effects of Zinc Sulfate on Growth and Zinc Uptake of Corn Plants Using Three Zinc Soil Tests" IN Communications In Soil Science and Plant Analysis; Volume 26 (1 &2); pages 277-286.
Kimbrough, Lamar Dr. and Alan Blaine. 1995 Mississippi Agricultural Extension Report; Mississippi State University; US. Department of Agriculture; www. Internet document.
Mahjoory, Ramez A. and Hossein A. Gharaee. 1984 "Characteristics and Geomorphic Relationships of Some Representative Aridisols In Southern Iran" IN Soil Science Society of America Journal (48) September- October; pages 1115-1119.
Mahjoory, Ramez A. 1975 "Clay Mineralogy, Physical, and Chemical Properties of Some Soils in Arid Regions of Iran" IN Soil Science Society of America Proceedings (39) November-December; pages 1157-1164.
McLacklan, Keith.1988 The Neglected Garden: The Politics and Ecology of Agriculture in Iran; London; I.B. Tauris and Company, LTD.
Steila, Donald and Thomas E. Pond.1980 The Geography of Soils: Formation, Distribution and Management; Maryland; Rowmand and Littlefield Pub. Inc.
Worldbook Encyclopedia I-10, 1995 pages 400-407; Chicago.
Copyright © 2010 June Narber, All Rights Reserved.