مجله کشاورزی بوم شناختی
سال یکم شماره 1 (1390)

Remediation of heavy metals polluted soils by physical and chemical methods requires large investments and complicated technologies. Phytoremediation is a relatively new technology that employs plants to decontaminate soils، water، sediments and atmosphere. This technology، compared to other technological approaches، is an environmental-friendly، easy to use and inexpensive method. Modeling Phytoremediation process is needed for further understanding the governing process and also to manage the contaminated soils. The objective of this study was to present a macroscopic phytoremediation model for of Ni-Polluted Soil. For this purpose، a new formulation was derived based on soil and plant responses to Ni pollutants. This approach assumes that relative yield reduction function can resemble the total Ni concentration in the soil. Combining the related functions of soil and plant responses to soil Ni concentrations، the phytoremediated amounts of Ni were predicted. In order to verify the proposed models، large quantities of soil was thoroughly polluted with Ni. After achieving soil and pollutants equilibrium، the contaminated soils were then carefully packed into pots. Upland Cress (Lepidum sativum) seeds were germinated in these pots. The Ni of soil samples and plant materials were extracted by 4M HNO3 oxidation and wet oxidation methods، respectively. Ni concentrations in the soil extracts and plant digestion were measured by Atomic Absorption Spectrometer (Shimadzu، AA 670-G) and Inductively Coupled Plasma Optical Emission Spectrometry (Varian Vista-PRO). The results indicated that relative yield reduction function followed a non-linear reduction trend. The results indicated that the proposed model for quantifying Ni concentration in plant can simulate the experimental data well (R2>0. 93(. The results also indicated that combining the non-linear relative yield reduction function and the proposed power model for Ni concentration in plant، provides a reasonable performance to predict Ni phytoremediation (R2>0. 93).

Canada thistle Cirsium arvense (L) Scop is one of the most important of world weed and third important weed in Europe. Weed Biological control is a safe، environmental friendly and practical method for weed management in agroecosystems. After finding an appropriate insect biocontrol agent of weed، the first necessary stage is doing host range tests. Host range studies on green thistle beetle (Cassida rubiginosa)، in which feeds actively on this weed as larva and Adult، were studied in 20 crops with two methods of no-choice and multiple-choice، and in 22 weeds through field surveys. The results showed that plant feeding and female ovipositor by green Thistle was observed in Russian knapweed، Common Russian thistle، Bull thistle and Canada thistle. Green Thistle beetle fed on safflower but only about 5% of plant shoots only in no choice treatments; however this beetle did not deposit any eggs on sunflower. Green thistle beetle could be a promissing classical biocontrol agent for Canada thistle in grasses، natural grasslands، agricultural fields and pastures.

Sulfosulfuron as a very important member of sulfonylurea herbicides is able to control of wide range of grassy and broad-leaf weeds spectra in wheat. In order to study its persistence behavior in soil، an experiment was conducted with two factors included herbicide application dose (common and overdose) and planting cover (with natural stand covered and bare soil) in randomized completely block design with three replications. Soil samples were collected at predetermined intervals after herbicide application and residues of sulfosulfuron were analyzed by HPLC using photodiode array detector. The dissipation of sulfosulfuron was found to have first-order kinetics in soil but its degradation rate was not different in the natural stand covered soil than bare one in spite of application rates. Faster rates were observed in overdose than common application rate however it was not significantly different between them. The Half-time (t0. 5) of sulfosulfuron were 32. 8 and 23. 5 days in common and overdose in natural stand covered soil and 33. 8 and 25 days in bare soil respectively. These quantities for t0. 1 (90% reduction in initial herbicide concentration) were 109. 2 and 78. 1 days in natural stand covered and 112. 2 to 83. 2 days in bare one. Sulfosulfuron residue was detectable in 97 days after application at wheat harvest time.

Biodiversity of natural ecosystems is often studied at three levels، ecosystem، species and genetic diversity. In fact، agrobiodiversity is the outcome of species، genetic and management diversity interactions. In order to investigate the species and functional diversity and structure of weed communities in sugar beet fields of different cities in Khorassan Razavi and Khorassan Shomali، 178 farms from 12 cities were studied. Data were collected from questioners، weed population sampling and interview with farmers. The results showed that weed population in different cities composed of 56 species in 14 plant families، in which dicotyledon species were more than monocotyledons. This community، 47 species were C3 plants and others were C4 species. These 56 species also included of 36 annuals، 2 biennials and 18 prennials. Poaceae and Asteraceae families showed the most diversity amongst the monocotyledon and dicotyledon، respectively. The results also shown that Chenaran and Khauf had the most (27 species) and the least (5 species) species richness. Sorenson and Steinhaus similarity indices were showed that Chenaran and Ghouchan showed highest similarity (0. 9%) whereas، Ghouchan and Khauf showed the least similarity index (0. 2%).

Nowadays organizing of farmers’ participation in the rural and agricultural organizations plays a vital and determining role in the process of sustainable development. Accordingly، the institutionalization of Farmers’ participation in a systematic framework due taking stages of individual motivation، socialization، social motivation and sustainable participation of the community in institutions، guarantee stability on different aspects of their life has a special status and should be considered as an efficient strategy in the agricultural extension and rural development policies. The purpose of this survey is enquiry of the indicators of sustainable participation of 138 farmers who are the land owner and the member of Farmers’ Organizations in the villages which are located in Haji Arab river basin in Sagz Abad District of Boein Zahra County. This research is a survey، descriptive (non-experimental) and correlation study and in enquiry and comparing means ranking of the studied group، the statistics of Man White Ne U (M. W. U) and Koruscal Walis has been used. According to the results of correlation among the variables، there is no significant relationship between age، education level، and land owned amount، annual income، intellectual participation and institutionalized participation of the farmers in the study. Moreover، since there is a significant difference between the attitude of two studied groups in case of ranking mean of institutionalization of participation according to membership and non-membership in the production organizations، it is suggested making benefit by participation of the identified members of production cooperatives، range growing projects، animal husbandry and poultry cooperatives in extension programs.

Crop residues could be considered as nitrogen supply resources. To study the effects of diffrenet crop residues on soil mineral nitrogen a four replicated experiment with six treatments as a RCB desing was conducted. Four crop residues (including cotton، corn، wheat and alfalfa)، urea and check were treatments were used. Crop residues were sliced to <5mm and were incorporated with soil. Nitrate and ammonia were analyzed during different phonological stages of wheat. Results revealed that nitrate + ammonia values in soil were not different significantly. The highest and leas values (75. 3 and 62. 77 kg ha-1) belonged to urea and check treatments respectively. The highest value among residues was seen in alfalfa treatment. Yield and yield components also were affected significantly، as the highest and least grain yield (8695 and 6962 kg ha-1) were obtained in alfalfa and urea treatment، respectively. Results indicated that nitrogen changes interpretation without considering two directional path of nitrogen releasing in soil and its uptake by plants is impossible. Non significant difference between residue and urea treatment with check treatment in respect to nitrate + ammonia revealed that this variety (N8019) is a high-demanding variety with high uptake rate. Also، results revealed that residues are advisable، at least because of reducing fertilizers application even if no yield reduction occurs.

In this research، the seed viability and growing status of Swallow-wort (Cynanchum acutum Willd.)، as an alien weed، which has been invasive in pistachio orchards of Aran and Bidgol، north of Esfehan province، was studied. The viability of seeds of this plant which were collected from previous year was tested using tetrazolium solution. The periods of growth stages of the weed in pistachio orchards from seedling emergence up to seed repining were recorded. Further more، seed and rhizome germination of this plant from soil depth was studied. Results indicated that 80-96 percent of the seeds collected from previous year were alive. In nature، emerging the first rhizome-originated seedlings were observed in initiation of March، maximized in mid March and stopped in the first days of June. Emerging of the seed-originated seedlings started from mid April، maximized in initiation of May and stopped at the end of this month. Most rhizome- and seed-originated seedlings were grown respectively in 10-19 and 1-9 cm soil depths. The plants originated from seeds didn''t attach to the pistachio trees.