Journal of Land Management
Year:2018 | Volume:6 | Issue:1 |Papers Count:8

Soil loss tolerance plays an important role in soil conservation programs. As no well-documented soil loss tolerance values are currently available for Iran, the present study was conducted to determine well-founded limits of tolerable soil loss in Iran. For this purpose, a preliminary survey was conducted of the various definitions of tolerable soil loss reported in the literature, the factors involved in the process, the relevant estimation methods, and the advantages/disadvantages associated with each estimation method. The data currently available on Iran were compared with those thus collected to derive and develop an appropriate method for soil loss tolerance estimation in Iran. The data collected on 292 erosion plots were subjected to analysis and such factors as soil thickness, limiting layer, land use, and climate were selected as the criteria to be used in the determination of soil erosion tolerance. The tolerance values thus obtained were then tabulated to classify the factors into five categories. Based on this classification, the allowable limits of tolerable soil loss in (semi-)arid rangelands might range from a minimum of 0. 25 to a maximum of 1. 25 ton/ha/year. These values might have a five-fold increase for the forests located at the Zagros Range, those in semi-arid to semihumid areas, and dry farms. Moreover, a ten-fold increase might be allowed in the coastal forests along the Caspian Sea. Finally, the values reported in the USDA recommended by US Soil Conservation Service are suggested for irrigated lands in Iran.

Diamonium phosphate is the basic fertilizer commonly applied to sugarcane cultivations. Under the climatic conditions in southern Khuzestan with its calcareous soils, a lot of the fertilizer nitrogen may become unavailable to the plant due to its loss as gaseous ammonia. This study was carried out to explore the effects of soil, time lapse, and weather conditions on nitrogen losses emitted in the form of gas. For this purpose, an experiment was conducted using plots in two sugarcane fields with different soil textures (Clay and Silty Clay Sand). To each plot, 300 kg ha-1 of diamonium phosphate fertilizer was applied along sugarcane furrows (soil surface) using the stripping method. Samples of the fertilizer spread in the plots were taken over a period of six weeks to measure residual nitrogen in the samples. Soil samples were also taken before and after fertilizer application to determine soil physicochemical characteristics. The results obtained were analyzed in a randomized complete block design and the mean of treatments were compared using the Duncan method. No significant differences in gaseous nitrogen losses from diamonium phosphate fertilizer were observed between the soil of a silty clay loam texture and that with a clay texture. Time lapse and temperature changes, however, showed significant effects (α = 1%), with the highest nitrogen loss recorded from the third week onwards. It was concluded that shorter time intervals between fertilizer application (base fertilizer) and sugarcane cultivation might help prevent high nitrogen losses and improve upon fertilizer effects.

Soil forms the main source of agricultural production; hence, preserving its health and fertility plays an important role in sustainable food production. This warrants maintaining adequate soil nutrients and moisture and minimizing its pollutant load. Nanotechnology might be exploited to achieve these goals toward improved soil properties. Applications of nanotechnology in soil science might include the uses of such materials as nanomodifiers to improve the efficiency of agronomic operations and soil aeration, porous nanozeolites for the slow and effective release of nutrients present in chemical fertilizers, nanohydrogels to increase soil water retention capacity and reduce irrigation water, and nanoparticles to remove contaminants from the soil. However, excessive use of nanomaterials might have toxic effects on soil microorganisms. It follows that sound and proper utilization of nanotechnology as an emerging technology might lead to such beneficial outcomes as food security and development of environment-friendly and sustainable agriculture in developing countries.

Soil maturation is affected by the the five factors of climate, bedrock, topography, living organisms, and time. Topography, as the most important factor involved, contributes to the maturation of soil profiles through creating micro-climatic environments that, in turn, affect soil-water relations, diversity in vegetative cover along the northern and southern stretches, intensity of soil erosion, and transport of rolling boulders or suspended materials. The present study was conducted to achieve a two-fold objective: to unravel the likely relations between geomorphology and agricultural land use, and to exploit geomorphological parameters as ancillary tools in small-scale soil classification without the need for soil sampling. The methodology used is based on the relationships among landform types and their relations with soil. For this purpose, use was made of the relationship between the soil map of the study region (prepared by the Institute of Soil and Water) and the dominant geomorphological parameters including slope, aspect, drainage network, and alluvial fan. Initially, the geomorphology maps of the relevant parameters were prepared in the GIS environment before they were mapped onto those of soil classes using geostatistical tools in the Arc map environment in order to derive the following relationships between soil and each of the slope, hydrology, and alluvial fan parameters: 1) soil quality improves with reducing slope, 2) soil materials and compounds improve in quality for cultivation with increasing depth from the cone tip toward the base of the alluvial fans, 3) more cultivable soils of grade II are observed at the joints of rivers of grade 3 or higher, 4) downstream stretches and alluvial fan ends are dominated by soil with only moisture limitation, and 5) grade I soils are located in areas with low slopes and vertical drainage.

The phenomenon of agricultural land dispersion and fragmentation is neither new nor particular to Iran; rather, it is observed in the land management systems of most Asian, European, African, and American countries. The present study attempts to study the present situation in agricultural land dispersion and fragmentation across these continents. The image emerging from the survey will be compared with that of Iran emerging from an agricultural census by the Ministry of Agriculture. It is the objective of this study to use the general image of the existing agricultural land distribution at both global and national levels toward developing strategies and measures required for controlling land dispersion. The data required are derived from a library research and the censuses conducted by FAO, the European Union, and the state ministries of agriculture in the countries surveyed. Based on the results obtained, the world average cultivated area is 8. 7 hectares comprising 1. 06, 1. 3, 14. 7, 22. 2, 50. 7, and 186 hectares in Asia, Africa, Europe, Central America, South America, and North America, respectively. Iran records an average cultivated area of 4. 9 hectares, which is approximately half the world average.

Crop rotation is an indispensable part of any sustainable land management program. An experiment was conducted in 2014 in Dehestan Dasht, Shahreza, Iran, to study agronomic rotations. For this purpose, rotational efficiency index in the study area was calculated as an ecological criterion, while production efficiency, water use efficiency, and land use efficiency indices were calculated as agronomic criteria. Based on the results obtained, the two rotations of (autumn onion-summer safflower-wheat) and (cotton-fallow-first forage sorghum cultivation) did not record acceptable values of rotational index. This is while the crop rotations of (wheat-summer safflower-barley), (wheat-second millet cultivation-barley), and (wheat-second sunflower cultivation-barley) recorded superior rotation indices of 1. 67, 2, and 2, respectively. Except for rotations including forage plants and vegetables, the two rotations of (wheat-intermediate mature corn-barley) and (wheat-second grain sorghum cultivation-barley) were the best rotations with production efficiency indices of 28. 07 and 30. 7 kg per day, respectively. Water use efficiency recorded its highest and lowest values of 1. 54 and 1 kg m-3, respectively, with the two rotations of (wheat-second grain sorghum cultivation-barley) and (wheat-second sunflower cultivation-barley). Finally, land use efficiency in the study area was found to range from 58 to 88%. Short crop rotation chains, implementation of incomplete rotations, and lack of a rotation-oriented approach were identified as the underlying reasons for the inefficiency of the crop rotations practiced in the study area.

It is essential to plan for the optimal use of both conventional and non-conventional water resources in order to successfully address water scarcity and to supply water for the growing population and urbanization in present-day Iran. Treated wastewater reuse may be considered as one solution to overcome water shortage and to avoid its wastage. The present study was, hence, designed and implemented to investigate the feasibility of reusing the effluent from Ekbatan Treatment Plant for irrigating farmlands and urban green spaces. For this purpose, certain physical, chemical, and biological characteristics of the effluent were measured on a daily basis during the one-year period from April to March 2016. The values obtained were then evaluated against the standards recommended by the Iranian Environmental Protection Organization and WHO. Results revealed that the effluent complied with the standards with respect to all the parameters measured so that the effluent could be safely reused for irrigating farms and urban green spaces. The treatment process used at Ekbatan Plant was also found to record BOD and COD removal efficiencies of 97% and 95%, respectively. The findings of the present study confirm the claim that wastewater treatment and reuse may be regarded as one of the most important solutions toward optimal management of water resources under the current conditions in Iran to meet part of the growing water demand.

Azospirillum plays a significant role in the quantitative and qualitative enhancement of crop yield. Its isolates, however, exhibit extreme differences as reflected in their impacts on crop yield. In this study, isolates of Azospirillum were initially compared with respect to their morphological traits and such growth promoting characteristics as nitrogen fixation; solubility of insoluble phosphorus; and their auxin, sidrophore, hydrogen cyanide (HCN), and ACC-deaminas enzyme production. Furthermore, five isolates characterized by superior growth promoting characteristics were investigated for their effects on yield and its components in wheat Morvarid cultivar. For this purpose, an experiment was conducted in a randomized complete block design with 6 bacterial treatments including five Azospirillum isolates and one control treatment (without bacterial inoculation) with 4 replicates at Iraqimahaleh Station, Golestan Agricultural and Natural Resources Research Center, where the soil is classified in the large Torriorthents Group. Results of seed inoculation in selected isolates showed that the impacts of different Azospirillum isolates on wheat yield components such as panicle length, peduncle length, number of seeds per panicle, number of panicles per square meter, weight of 1000 seeds, seed yield, and straw yield were statistically significant at 1% confidence level, as evidenced by increases of 14. 91, 47. 94, 25. 98, 24. 97, 82. 86, 20. 42, and 37. 88%, respectively, in the above traits of Mordavid cultivar relative to those of the control with no inoculation.