مجله کشاورزی بوم شناختی
سال دوم شماره 2 (1391)

A high level of cadmium (Cd) in the environment generally influences the population، activity and composition of soil microorganisms، especially N dynamics and enzyme activities، with a consequence for nutrient cycling and availability. The addition of organic materials to the Cd-polluted soils may reduce the detrimental effects of Cd on microbial activities and biochemical properties. The objective of the current study was to examine the effect of compost as a soil amendment on N mineralization، microbial biomass N and urease activity in soils spiked with fresh Cd. A 2×5 factorial experiment consisting of two levels of compost (0 and 2. 5 t ha-1) and five levels of Cd (0، 50، 100، 150 and 200 mg Cd kg-1) arranged in a completely randomized design with three replicates was carried out under laboratory conditions. Measured total and available cadmium at the end of incubation period indicated a stronger (and negative) correlation between the available fraction of Cd with soil N mineralization، microbial biomass N and urease activity than the total Cd level. Results showed that increasing Cd level had a significant، negative effect on all the measured soil properties. However، compost addition to soils contaminated with Cd resulted in a reduction of Cd toxicity on indicators of N dynamics، most likely through decreasing its bioavailability to soil biota. In brief، the application of organic materials in Cd-contaminated soils could alleviate the unfavorable and inhibitory effects of Cd on soil N dynamics and subsequently N availability to plant may increase.

In order to evaluate the effects of planting beds and methods on vegetative and reproductive characteristics of saffron، a field experiment was conducted as factorial based on randomized complete block design with three replications at the Agricultural Research Station، Ferdowsi University of Mashhad، during two growing seasons of 2009-2010 and 2010-2011. Treatments consisted of five planting beds including leaf mould، mushroom compost، municipal waste compost، cow manure and bean stover (5 t ha-1 for each one) and two sowing methods of row and mass planting. Criteria such as leaf and tunic dry weight، leaf length، corm diameter، number of daughter corm، number and weight of corm in each weight categories (2-4، 4-8 and 8-16 g)، flower number، flower fresh weight and stigma dry weight were measured. Results indicated that simple effects of planting bed and sowing method significantly affected all measured criteria during two years of experiment. The highest stigma weight obtained by application of cow manure (around 0. 7 and 0. 8 kg. ha-1) in the first and second years، respectively and using leaf mould (0. 5 and 0. 6 kg ha-1) caused the lowest stigma weight in the first and second years، respectively. Mass planting at the first and second years enhanced stigma yield up to 13 and 10% compared with row planting، respectively. Interaction effects of different planting beds and methods on corm diameter، number of daughter corm، number and weight of corm in each weight categories showed significant effect in which these criteria were improved by application of cow manure in mass planting method.

Kochia is an annual، drought and salinity resistant plant، that recently it is a valuable source for feeding animals. In order to evaluate germination characteristic of Kochia under different dose of gamma ray and salinity stress، an experiment was conducted in a completely randomized design with 4 replications. Treatment included three level of salinity (10، 20، 30، dS/m) using NaCl and also treatment without salt (control) and 6 gamma rays level (50، 100، 200، 300and 400 Gray). Variance analysis showed that different levels of dose of gamma ray and salinity stress had a significant effect (P<0. 01) on percentage of germination، germination rate، mean germination time، germination index and dry weight and interaction between them had the same effect. In control condition، control seed had the highest germination characteristics. With increasing in salinity stress to 10 and 20 dS/m، 50 Gray and at 30 dS/m، 200 Gray showed the highest germination characteristics. So using gamma rays in salinity stress can increase germination capability.

The mathematical formulas for evaluation of intercropping advantage provides accurately assess of intercropping systems based on economic and competitive parameters. In order to study the economic and competitive indices on intercropping of soybean with sweet basil (Ocimum basilicum L.) and borage (Borago officianalis L.) an experiment was performed in a randomized complete block design with 9 treatments and 3 replications in 2011 at a field located 10 km of Shirvan (Northern Khorasan). Treatments were included different ratios of intercropping of soybean with sweet basil and borage (100:0، 75:25، 50:50، 25:75، and 0:100، soybean: sweet basil or borage). In this experiment، we used the indices of land equivalent ratio (LER)، relative crowding coefficient (K)، aggressivity (A)، competitive ratio (CR)، system productivity index (SPI)، actual yield loss (AYL)، area-time equivalent ratio (ATER) and competitive index (CI) and economic indices of monetary advantage (MAI) and intercropping advantage (IA). The results showed that intercropping had superiority compared to monoculture. In all ratios، aggressivity indices indicated that soybean was dominant compared to sweet basil and borage. The results suggested that there was a relationship between economic and competitive indices، so that economic advantageous was observed in treatments with LER and K higher than one. In general، treatments of 75% soybean: 25% sweet basil and 50% soybean: 50% borage were superior than other treatments. The indices indicated that intercropping soybean with sweet basil has a high efficiency when compared to intercropping soybean with borage.

In order to study agrobiodiversity and the factors which affect it، a study was conducted in six villages of Kashan county in Iran in 2011. Villages were Nahsalj، Borzabad، Sensen، Hassanabad، Shadian and Vidoja. All villages except for Nashalj were in plain areas while Nashalj was situated in a mountainous area. Semi-structured questionnaires were used to gather information about the species diversity and socioeconomic characteristics of the villages. Households were considered as sampling units for this study. Simpson diversity index (SDI) was calculated as a criterion of agrobiodiversity status. Stepwise regression was used to find out the contributing factors to SDI. Results indicated that there were significant differences between villages in case of all socioeconomic variables except for the percentage of income from non-agricultural sector and the number of land pieces. Results showed that all villages had relatively high SDI indicating that agrobiodiversity was satisfactory in all villages. Hassanabad and Sensen villages had the highest (0. 88) and lowest (0. 69) diversity، respectively. It was also revealed that the percentage of income from agronomy and livestock sectors، experience of farming and the percentage of income from non-agricultural sector were the four most influencing variables of SDI. Overall، it was concluded that agrobiodiversity in Kashan is relatively in good status and a combination of farmers'' experience and higher income from agronomy and livestock sectors favors agrobiodiversity in this county.

Recently، there is an increasing concern about the effects of pesticides on non-target organisms. Fungicides are a group of pesticides that use widely and also have harmful effects. Residual of fungicides cause environment pollution and put in danger the human health. This is very important and must be considered. This study consider the harmful effects of authorised fungicides in Iran and their potential and environmental risks using EIQ model. The results showed Bordeaux mixture and copper oxychloride from inorganic compounds and tebuconazole and hexaconazole from triazole group have highest and lowest field EIQ، respectively. The most dangerous group of fungicides are multiple locations contact in mode of action that Bordeaux mixture and copper oxychloride belong to this group. There is suitable fungicides that could easily eliminate hazardous fungicides based on number of groups and mode of actions. With a good planning، Triazole fungicides can use instead of hazardous fungicides. It seems the best way is using right alternative program in using fungicides that have different mode of action.

In order to study of crop rotation and weed management methods effects on weed population، a 5-yr experiment was conducted from 1384 at field research of plant protection research institute، Karaj، Iran. The experimental treatments were crop rotation (including: sugar beet-sugar beet and sugar beet-wheat) and weed management method (including: chemical، chemical+ mechanical and hand weeding) that arranged in factorial experiments based a randomized complete block design with 4 replications. In contrast with sugar beet- wheat treatment، results indicated that annual and perennial weed populations increased in the end of rotational period in mono-culture system. Annual weed population also decreased in integrated weed management plots but it had no effect on perennials. Result suggested that the weed seed community in a sugar beet- wheat rotational system differs in structure and composition from communities associated with continuous sugar beet system، which in the end of 5 years experiment، percentage of bindweed and Johnson grass seeds in soil (in compare with knotweed and amaranth) were fewer in rotational treatments and they distributed in layers deeper than in 0-10 (cm) layer of soil.

In order to investigation of mechanical and chemical weeds management on Fajr cultivar of rice agronomical traits، an experiment was conducted in Rice Research Institute at Amol، Mazandaran province، Iran during 2010 growing season. The experiment was conducted as a spilt-plot trail under Randomized Complete Block Design (RCBD) with three replications and 21 treatments. Main plots at three levels were without cono-weeder application، one time cono-weeder and two time applications cono-weeder and subplots at seven levels were Bentazon herbicide، Londux، Ronestar، Butachlor، Satern، hand weeding and without herbicide (weed infested). Results showed that cono-weeder effects، herbicide application and interaction effects of both methods، had significant effect at 1% level on all of rice plant measured traits. Between integrated treatments، twice cono-weeder applications without herbicide، hand weeding treatment and also twice cono-weeder applications including different herbicide application have shown highest grain yield، so that، between three treatments، Twice application of cono-weeder without using of herbicide، was the best treatment.