JOURNAL OF AGROECOLOGY (کشاورزی بوم شناختی)
Year:2014 | Volume:4 | Issue:1|Papers Count:7

During the past four decades, the need for chemical fertilizers in Iran has continuously increased. Each year, millions of dollars are spent on buying chemical fertilizers and the Government also provides a large amount of subsidies to help farmers in supplying chemical fertilizers. As a consequence, the related environmental hazards have led to increased consumer health risks from exposure to specific compounds such as the nitrate accumulation in agricultural products. Predicting the amount of fertilizer needed over the long-term is an essential key for ensuring food security and public health for the future. To estimate the required amount of fertilizer, data on the area under cultivation, production and yield for a 45-year period (1962 to 2007) were collected from the databases of the Ministry of Agriculture, the Statistical Center of Iran and the Food and Agriculture Organization (FAO). Among the causal models applied, the Tenkorang model with variables included―yield, previous year yield, cultivation area and pervious year fertilizer consumption― gave the best estimate of the amount of fertilizer demanded with a correlation coefficient of 0.94. Coefficients for the model were calculated based on data belonging to the period 1962 to 1991. The accuracy of the model was demonstrated by comparing the predicted and actual values for the years 1993 to 2007. According to the Tenkorang model, the total amount of chemical fertilizers required for Iran’s agricultural production in 2021 will be apporximately 5 million tons.

The vertical distribution of leaf area and dry matter is considered to be an impact factor on light absorption, evapotranspiration of canopy, dry matter accumulation and seed yield. To study the vertical distribution of leaf area and dry matter of the maize canopy in competition with weeds and cover crops, an experiment was conducted at Sari in 2011. This experiment was performed in a randomized complete block design with 8 treatments and three replications. Three cover crops, namely bean (Phaseolus vulgaris), soybean (Glycine max L.) and berseem clover (Trifolium alexandrium), were planted on two dates: simultaneous with and 21 days after maize sowing (delayed planting). In addition, maize sole crop with weed control and weed interference was added to the treatments. The results showed that dry matter and leaf area index of bean and soybean were higher than for clover. The delayed planting of bean and soybean increased the leaf area index of maize upper layer canopy rather than sole cropping of maize with weed interference: this approach caused an increase in the competitive ability of maize against weeds. The leaf area and dry matter of weeds were reduced more by bean and soybean than by berseem clover. The cover crops caused the maximum amount of weed (in particular, veveltleaf and bermuda grass) dry matter to be accumulated in the primary layer. The cover crops reduced the number of layers and dry matter of per layers in the weed canopy. For maize, the dry matter was less in the presence of berseem clover than for the two other cover crops. The maximum amount of weed dry matter was accumulated in the primary layer. Grain yield in maize was higher in simultaneous sowing than in delayed planting of cover crops, especially soybean. The cover crops’ dry matter had a positive correlation with dry matter of maize and was negatively correlated with dry matter of weeds. The yield of maize in the present of crop cover was higher than for sole cropping of maize under weed interference. The grain yield of maize with a delayed presence of cover crop was higher than at the same sowing date.

Studying the productivity of production factors, especially of scarce inputs such as land and water, can help to increase productivity with a view to reducing dependence on external inputs and resources as well as to achieve the goals of sustainable agriculture. Saffron is one of the main agricultural products and export items of South Khorasan Province and Iran, which not only reaps high economic benefits for producers, but is also one of the most efficient crops in terms of economic productivity, especially with respect to water consumption. The aim of this study was to evaluate the productivity and optimum use of inputs into the saffron production systems in South Khorasan Province. Required data were collected through questionnaires and interviews with 98 farmers.The trans-log production function was used to determine the relationship between production and inputs. Based on the data collected, the elasticity of inputs was calculated and used to determine the production areas for each input and the reasonable rate of input consumption. The results showed that the production elasticity values for land, water, fertilizer and saffron corms (for planting) were positive, but were negative for manure and pesticides. This means that the farmers’ use of the inputs of land, water and fertilizer and saffron corms were within economic parameters, but their use of animal manure and pesticide were in the third region and higher than the optimum amount. Furthermore, the sum of elastic values of inputs was equal to 0.91 indicating that there are decreasing returns towards scale in saffron production in South Khorasan province.

Irrigation systems have various impacts on agriculture in terms of their ecological, social and economic aspects. Understanding these effects may contribute to develop appropriate policies and strategies for sustainable agriculture. Accordingly, the present research was conducted to determine the impacts of irrigation systems development on agriculture in Tehran. A survey was undertaken with a sample of 72 experts and specialists of irrigation systems development selected using the Snowball technique as a non-probability sampling. The main research tool was a questionnaire the validity of which was reviewed by members of the expert group. Reliability of the questionnaire was obtained at 0.85. The results revealed that sustainable resource management, employee and income, environmental impacts, intuitional trust and development, mechanization, productivity, improvement of quality of life, expansion of land fields and improvement of population profile are all key impacts of irrigation systems development on Iranian agriculture. These factors could measure about 73.142 per cent of total variance.

There are many rainfall variations in dry lands so the application of a Supplemental Irrigation (SI) system may result in increased seed yield. Dry land pulses are grown without chemical fertilizers. Since the root of pulse has a nitrogen-fixation ability, improving the biological conditions and moisture content can increase seed yield. The effect of seed inoculation with phosphate-solubilizing-bacteria (PSB) and Arbascular Mycorrhizae fungi (AM) on yield and water use efficiency of lentil was examined under conditions of SI. This study was performed at the Rainfed Agricultural Research Station in Northern Khorasan over two years with four replications in a split plot design. Three levels of irrigation were applied as the main factor including: no irrigation, a single irrigation at planting and one at the flowering stage. The application of biological materials at three levels as sub factor was considered including: no use of biological materials, seed inoculation with PSB, and a mixture of PSB and AM. The results showed that SI had significant effect on some traits including seed yield, biological yield, harvest index (HI), evapotranspiration (ET), water use efficiency (WUE), and N and P seed content. Biological materials only caused a significant effect on ET, WUE and P seed content and no significant interaction was observed between these factors in the two years. Irrigation at flowering stage increased seed yield 20% more than irrigation at the planting stage. The use of biological materials in conjunction with irrigation had no effect on seed yield. Water use efficiency in rainfed conditions diminished with the use of PSB while using of mycorrhizal fungi was important, especially due to positive effects on water use efficiency and, throughout mycorrhizae, enhanced sustainability of plant production.

Exploring weather variability and its effects on crop yield may help to provide a better understanding of its effects on agricultural production. In this study, the relationship between weather descriptors and wheat (Triticum aestivum L.), barley (Hordeum vulgare L.) and potato (Solanum tuberosum L.) yields were assessed under irrigated farming conditions in Hamadan Province. Long term data (1990 to 2010) of yield and weather variables (rainfall and temperature) were collected from the Agricultural and Meteorological Organizations of Hamadan Province. The relationships between crop yields and climatic variables were studied using correlation and simple linear regression analysis. Results indicated that the association between various crop yield and descriptors varied in different study locations. In Razan and Bahar, yields of the crops studied did not correlate with weather indicators whereas, in other regions, the relationship between rainfall and temperature with crop yields was strong. In Kabodar Ahang, the correlation between wheat and barley yields and Malayer wheat yield with the growing season maximum was negative and decreased with an increasing maximum temperature during the growing season. In all study areas, potato yield did not correlate with rainfall. However, was a significant and positive correlation between barley yield with rainfall in Hamedan, Toyserkan and Nahavand and wheat yield with rainfall in Malayer, Nahavand and Toyserkan. The association of results between various crop yields on a monthly scale, indicate a high and significant correlation (positive or negative) between temperatures in March and April rainfall with crop yield in each part of Hamedan Province.

In order to study the impacts of various wheat straw and nitrogen fertilizer levels on the combination, relative density and population of weeds in a garlic field, an experiment was conducted as factorial based on randomized complete block design with three replications at the Agricultural Research Station of Ferdowsi University, Mashhad, during the 2011-2012 growing season. Treatments were four levels of wheat straw (0, 5, 10 and 15 t ha-1) and four nitrogen levels (0, 50, 100 and 150 kg ha-1). The combination, density and dry weight of weeds were measured both before and simultaneously with garlic canopy closure. The results indicated that the simple and interaction effects between wheat straw and nitrogen fertilizer levels were significant on density and dry weight of garlic. By increasing wheat straw from zero to 15 t ha-1 the density and biomass of weeds declined in both sampling stages. Spreading wheat straw on the soil surface reduced the number and density of weeds through preventing their germination by limiting the radiation reaching the soil. Nitrogen weed density and biomass increased due to their vegetative growth. Although nitrogen is one of the essential nutrients for growth improvement but causes changes in soil fertility, it seems that management of nitrogen consumption and use of crop residues are ecological and integrated approaches for decreasing the population and density of weeds in garlic fields.