مجله مدیریت اراضی
سال سوم شماره 1 (بهار و تابستان 1394)

Rational use of fertilizers in soil depends on the awareness of the condition of fertility and nutrient in soil. One approach is based on a comprehensive understanding and correct use of precision agriculture of agricultural soils. Thus the map of spatial variability of soil properties is a key step in the application of precision agriculture which based on the map, application of agricultural inputs could be managed in a systematic way. To this end, comprehensive study of paddy soils fertility in Guilan province through GIS mapping were counducted. Soil characters including Total N, P, K, pH, EC, OC and clay were measured in 8567 soil samples collected from arable land of Guilan province. These characters were analyzed through descriptive statistics, geostatistics and GIS. Mapping showed that most soils of the province in terms of pH and EC were favorable for the growth of rice plants, while total nitrogen, potassium and phosphorus need to be managed. Many paddy fields in the Central Plains area of Guilan and in the alluvial soils of Sepeedrud basin showed nitrogen deficiency which soil response to nitrogen fertilizer is high. In nearly 40% of the land surface, P concentration is less than critical level because of the continued cultivation of plants without use of phosphate fertilizers by farmers or the low ability of soil to preserve native soil phosphorus. Agricultural land of Guilan province was divided into Eastern and Western parts based on potassium content. In the most part of western area, available potassium is low, while in the eastern part, available potassium was higher than western part because of Sepeedrud sediment. In nearly 68% of the study area available potassium of soil was less than critical level(160 mg per kg) for growing cultivated Rice. The results in general showed that the nutrient status of paddy fields is not distributed uniformly from geographical point of view .Therefore, to prevent soil fertility decline and increase of production cost fertilizer distribution in the region and consumption of fertilizer in the field should be based on achieved results.

Production potential of land for human food, especially wheat supply is limited and depends on environmental factors affecting production, such as climate, soil, landscape, and management. This paper examines these factors and provides guidelines for understanding the limitations of these factors and their role in the production were also investigated. The study area were in Aghili plain of Gotvand and Mianab plain of Shooshtar in Khuzestan. The result showed that land production potential for irrigated wheat in mian ab from 933 to 6023 kg/ha and for Gotvand is 2254 to 6687 kg/ha. The main soil limiting factors in both area were salinity, alkalinity, drainage and calcium carbonate limitations. predicted yield were compared with farmer wheat yield in both areas and showed coefficient factor equal 0.80 for Gotvand and 0.77 for Shoushtar. That means model can predict farmer yield with 80 percent in Gotvand and 77 percent of accuracy for Shoushtar.The reason of higher wheat yield in Gotvand to shoushtar is because of lower salinity limitations in Gotvand area.

The rhizosphere is a microecological zone in direct proximity of plant roots. The theoretical extent of the rhizosphere is dependent on the zone of influence of the plant roots and associated microorganisms. The rhizosphere is a metabolically busier, faster moving, more competitive environment than the surrounding soil. The rhizosphere include three zones which are defined based on their relative proximity to and thus influence from the root: Endorhizosphere,Rhizoplane and Ectorhizosphere. The rhizodeposites include: Root Exudates, Secretion, Lysates and Gaseous Compounds. Compounds in root exudates assist plants in accessing nutrients by acidifying or changing the redox condition within the rhizosphere or directly chelating with the nutrient. As the soil dries and its hydraulic potential decrease, exudates will subsequently begin to lose water to soil. When this occurs, the surface tension of the exudates decreases and its viscosity increases. In addition, as viscosity increase, the resistance to movement of soil particles in contact with exudates will increase, and a degree of stabilization within the rhizosphere will be achieved. Traditional nutrient management strategy was highly dependent on external chemical fertilizer input, but ignored exploring biological potential of efficient acquisition and use of soil nutrient resources by plants intrinsically. Rhizosphere is the key center of interactions among plants, soils and microorganisms; the chemical and biological processes occurring in the rhizosphere not only determine mobilization and acquisition of soil nutrients, but also control nutrient use efficiency by crops. The rhizosphere management strategy lays emphasis on maximizing the efficiency of root and rhizosphere processes in nutrient acquisition towards high-yield and high-efficiency sustainable crop production by optimizing nutrient supply in root zone, regulating root morphological and physiological traits, and manipulating rhizosphere processes and interactions.

Rhizobia are one of the most important soil bacteria that have a symbiosis nitrogen fixation relation with legumes. The average amounts of fixed nitrogen in legumes are about 200-300 Kg N.ha-1. It is fixed annually 30-40 million tones of nitrogen by symbiosis systems. Legumes have important roles in feeding and protein needs of human and livestock. The largest areas under grain legumes cultivation in Iran belongs to Lorestan province. About 60 percent of grain legumes are produced in Fars, Lorestan, Khuzestan and Azerbayjan-Sharghi provinces. The largest areas under forage legumes cultivation in Iran belongs to Azerbayjan-Sharghi and Azerbayjan-Sharghi provinces. The researches revealed that rotation with legumes and using them as green fertilizers have significant effects on increasing of soil nitrogen. Low efficiency of native bacteria in nitrogen fixation, salinity, acidity, temperature and humidity, toxicity and deficiency of elements, are the most important limiting factors of nitrogen fixation. The best recommendations are evaluation of native symbiotic Rhizobia and necessity of inoculation and study of possibility of new legumes cultivation with high rating in fixation or with rotation of other crops. Utilization the guidelines presented in this paper along with education and extension of recent development for awareness of benefits and advantages of green manures and legumes cultivation is a hopefully approach.

Black Cumin (Bunium Persicum L.) is a perennial herbal plant, with tuber(corm),from Apiaceae family, that is native of some parts in west Asia including east of Iran. The studies show that there is a valuable potential of domestic use of black cumin in Khorassan province of Iran. Nitrogen, Phosphorus and Potassium, are three main nutrient elements that are used in large amounts, as fertilizers. Black cumin needs these elements for its growth. That’s way research focused on determining effects of N.P.K on black cumin growth in the first Step. Research results showed that nitrogen application is essential for the yield increase, but high amount of nitrogen can decrease its seed yield. This plant will fulfill its expected yield with the minimum amount of nitrogen. Meanwhile its response to balance use of potassium is appropriate and use of phosphorus resulted expected yield. Use of nitrogen, phosphorus and potassium increased the seed yield about 51% compared to its native habitat without fertilizer application. Under the Khorasan climate conditions(Mashhad), application of 40 kg/ha N, 30 kg/ha P2O5 and 80 kg/ha K2O is recommended for black cumin. This recommendation in respect to the yield increase (about 150 kg seed/ ha) and the price of black cumin (800000 rials/kg) can economically, produce an appropriate income for farmers.

Despite increasing agricultural production in the last three decades, large part of arable soils in Iran are faced with loss of organic carbon, depletion of nutrients, and soil erosion. It is obvious each of these factors will have a direct impact on soil fertility and production sustainability, and for this reason, it is possible that the continuity of this process lead to environmental problems and reduce agricultural production. In this regard integrated soil fertility management is view beyond the supply of nutrients and consists of methods, which aims to maximize the agronomic efficiency and productivity of crop. Atthe present time, the studies show that due to soil and climatic conditions of the country, in addition to optimal use of nutrients and soil fertility, national programs should focus on improving the efficiency of nutrient management and soil organic carbon. Thus, it will be protected the sustainability of soil and agricultural productivity.