کمال خلخال

Composting is an effective approach to organic waste management, but it also has disadvantages such as greenhouse gases emission (CH4, CO2, and N2O), bad smells, nitrogen loss, and contamination of soil and water resources. Therefore, it is crucial to develop a method to reduce gas emissions and improve the quality of compost at the same time. To overcome these disadvantages, some additives are usually used. The use of additives at the beginning of the composting process to produce valuable compost is known as "co-composting". Various materials can be incorporated into waste during composting. These materials fall into three categories: organic, mineral, biological, or a combination of these. Some of these added materials serve as bulking agents, primarily affecting the physical structure of the compost (such as aeration). However, most of the time, these substrates also have direct or indirect impacts on other composting factors and can be considered as additives. Additives play a role in enhancing the composting process by reducing leaching and gas emissions, improving aeration, accelerating organic matter breakdown, and enhancing nutrient content and availability in the final product. The research published so far showed that the effect of wood biochar along with leonardite and coal on the quality of compost obtained from animal manure and forest organic matter had not been studied in Iran, and considering the importance of the feasibility of improving the quality of compost, this research was conducted.

In this research, the effect of wood biochar, leonardite and coal on some characteristics and quality indices of the co-compost of animal manure and forest organic matter was studied. The biochar was produced at 400° C from the pyrolysis of mixed pruning plum and pomegranate brunches. Leonardite and coal were also prepared from companies active in this field. The experiment was conducted as a factorial in a completely random basic design with three replications. The first factor of treatment included wood biochar, leonardite and coal at two levels of 2 and 4% by dry weight and the second factor of time included 12 weeks. During the composting process, temperature, pH, EC, total nitrogen concentration, organic carbon content and some quality indices of composting such as humification index (HR), humification ratio (HI), degree of polymerization (DP) and total materials Humic (HS) were measured.

According to the results, the treatments were significantly different from the control regarding the temperature of the compost pile, and the coal treatment showed the highest temperature at the level of 2%, and the duration of the thermophilic phase in the leonardite treatment was 2% longer than the other treatments. Among the additives, 2% and 4% leonardite treatments created the highest total nitrogen content in the compost. The additives used in this research did not make a significant difference in compost pH, but coal at the level of 4% caused a significant increase in electrical conductivity (EC). Biochar and coal increased organic carbon concentration in the compost pile. Leonardite treatments of 2% and 4% produced the highest values of humification indices (HS, DP, HI, HR), but they were not significantly different from each other. The biochar used in this research increased the C/N ratio of co-compost.

In general, leonardite treatments were found to be useful in terms of the indicators of final compost and biochar and coal treatments to accelerate composting in the early stages. But the results of this research showed that it can be used at the end of composting processes in order to enrich and improve the quality of the produced compost. The results of this research showed that considering the costs of raw materials, coal is a suitable treatment to accelerate the production and improve the quality of compost. The results obtained about the effect of biochar obviously cannot be generalized to all biochars and different results may be obtained depending on the type of biomass and pyrolysis conditions. Therefore, it is recommended to use the combination of organic and biological or organic and inorganic additives in future research. Other traits such as indices of microbial contamination and abundance of weed seeds should also be measured and the effect of treatments should be studied. Finally, it is recommended to study the effect of final compost on the characteristics of calcareous and acidic soils.

In this study, the effect of biochar, leonardite and coal was investigated on humification and germination index, and the concentration of some elements in the co-composting of manure and forest organic materials. The experiment was conducted in a factorial design with two factors, namely treatments at two levels (2 and 4% by weight) mixed with the raw materials and time was the second factor. Sampling was carried out during the composting process in the first to 12 weeks, measuring temperature, EC, C/N ratio, nitrate, and total concentrations of P, K, Ca, Mg, Na, Fe, Zn, Cu, and Mn, humification and germination index in the compost. The results showed that the coal (2%) had the highest temperature, while the leonardite (2%) had the longest thermophilic phase period. The coal (4%) led to a significant increase in EC, and biochar increased nitrate concentration and C/N ratio. The addition of leonardite resulted in a significant increase in humic and fulvic acids concentrations, as well as the highest values of humification and of polymerization index. The additives did not have a significant effect on germination index and the E3/E5 and E4/E6 ratios. The control had higher concentrations of measured elements compared to other treatments. The results of this study suggest that considering the cost of raw materials, coal is a suitable treatment for accelerating the production and improving the quality of compost, and leonardite, due to its high humic substrate, can be used at the end of composting for the enrichment of the produced compost.

In this research available iron was measured in 21 calcareous surface soil samples (0-30 cm) by five methods including DTPA, AB-DTPA, AC-EDTA, hydroxylamine, reference ammonium oxalate and rapid ammonium oxalate. Fe fractions were also determined by the modified sequential extraction procedures introduced by Singh et al. According to results, rapid ammonium oxalate and AC-EDTA methods extracted the maximum (856.03 mg.kg-1) and minimum (4.46 mg.kg-1) amounts of Fe, respectively. Rapid ammonium oxalate extraction method, in addition to Fe-Afeox, extracted other fractions of iron such as Fe-Ex, Fe-Om, Fe-CFeox and Fe-Res. Hydroxylamine method compared to other methods, ectracted Fe mostly from the amorphous oxides source. Regression analysis indicates that Fe-Ex, Fe-AFeox and Fe-Res fractions have major and Fe-Car and Fe-Mnox have minor role in releasing available Fe (with AB-DTPA and DTPA) in the studied soil. According to the statistical relationships, carbonates associated Fe, does not seem a potential source of available Fe in calcareous soils. Organic carbon content and cation exchange capacity of the soils appear the two most influential soil properties that predict available Fe in the studied soils.

Knowledge about the iron (Fe) critical level and plant response to application of Fe can effectively help to proper use of this element. Corn is used in human nutrition, poultry and livestock in pharmaceticals, starch, and alcohol and oil production. Because of the calcareous soils, low organic matter content, low solubility of iron in alkaline pH, carbonate and bicarbonate ions present in irrigation water, and phosphorus over fertilization, Fe deficiency is common in most fields and gardens.The aim of this study was investigation effect of Fe-EDDHA on corn growth indices and determination of Fe critical level in some calcareous soils of East Azerbaijan province using DTPA and ABDTPA by conventional methods.
In this research, Fe critical level for corn (Zea mays L.) was determined in 21 soils from corn fields of East Azerbaijan province during 2014-2015. Corn plant was cultivated in two level of Fe (zero and 10 mg Fe kg-1 as Fe-EDDHA) as a factorial experiment in a randomized complete blocks design with three replications in pots containing 4 kg air-dried soil. After 60 days, the plant growth parameters were measured. Fe available of studied soils were extracted by DTPA and ABDTPA methods and measured by atomic absorption spectroscopy (AAS).
The results showed that soil type had a significant effect on the growth indices of corn and the effect of applied Fe levels was significant in some of growth indices while the fertilizer and soil interaction was not significant. Critical level of soil Fe for corn with DTPA-Fe, based on 90% relative yield, was determined 10.08, 5, 11.4 and 7.44 mg Fe kg-1 soil by using plant response column order procedure, graphical Cate–Nelson, Cate–Nelson analysis of variance and Mitscherlich-Bray, respectively and for AB-DTPA method was 6.19, 4.4, 9.8 and 4.53 (mg Fe kg-1 soil) respectively. As well as to achieve a 90% relative concentration of active Fe in shoot by using graphical Cate–Nelson and DTPA and AB-DTPA methods, critical soil Fe level were 6.8 and 4.8 mg Fe kg-1 soil, respectively. Mitscherlich-Bray equation coefficients, C1 and C2, for DTPA-Fe were 0.1344 and 0.0356 kg soil mg-1Fe, respectively and for AB-DTPA-Fe were 0.2207 and 0.0556 kg soil mg-1Fe.
In this study, statistical Kate- Nelson's method due to very low coefficient of determination was unsuccessful. Also, due to the low level of applied Fe fertilizer, C2 factor of Mitscherlich--Bray equation was mostly negative. Iron critical levels by averaging and using DTPA and AB-DTPA methods for corn in these areas, respectively, 33/7 and 98/4 mg kg is suggested.

This research was conducted to evaluation of extraction methods for determining the available iron (Fe) and active Fe in corn plant (Zea mays L.) at 21 calcareous surface soil samples in the East Azerbaijan province. In a greenhouse experiment, corn plant single cross 704 cultivar has been cultivated with 3 replications. After 60 days, the plant growth parameters were measured. According to the results, DTPA and AB-DTPA had the highest linear correlation coefficient with growth indices of corn such as active Fe concentration, chlorophyll index, Fe content, fresh weight and shoot dry weight as well as with some physical and chemical properties of soils. AB-DTPA due to a correlation coefficient greater than DTPA and simultaneous extraction of multiple nutrients was chosen as the best extractant. On the average, rapid ammonium oxalate and AC-EDTA extracted the maximum and minimum amounts of Fe, respectively. The both of 1.5% o-phenanthroline and 1N HCl methods were suitable for measuring corn active Fe concentration. Significant correlation (r=0.66 ,p