نشریه مدیریت خاک و تولید پایدار
سال یازدهم شماره 3 (پیاپی 37، پاییز 1400)

Intensive agriculture has reduced soil fertility and has had harmful effects on human health and the environment. Therefore, the use of low-input and environmentally-friendly agricultural methods such as sustainable agriculture is necessary to achieve the required sustainability in food supply. Preservation and revitalization of beneficial microbial communities in the soil, is one of the important strategies of sustainable agriculture. These microorganisms with diverse activities (such as residue decomposition, mineralization and fixation of nutrients for plant growth, production of plant hormones, decomposition of pollutants, plant growth and biological control of plant pathogens), play very important roles in the function and sustainability of terrestrial ecosystems. Understanding the factors affecting these communities particularly the different methods of managing agricultural lands helps to manage them towards improving soil fertility, optimal plant growth and health, and increasing the productivity and stability of agricultural ecosystems. For selecting the best cultivation methods that preserve the diversity and strengthen microbial communities as well as avoiding activities that lead to the destruction and reduction of its diversity of microorganisms, fast, reliable, sensitive and specific methods are needed that provide comprehensive knowledge about the effect of different agricultural activities on the structure and diversity of these communities, including its unculturable part. Among molecular techniques, polymerase chain reaction-based methods have been widely used to study the diversity and structure of soil microorganisms, and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) is one of the most well-known and widely used methods. PCR-DGGE has been used successfully for more than two decades to investigate the effect of different crop managements on the diversity and structure of microorganisms in different soils or in a soil under different crop managements. Despite the availability of new generation of high-throughput sequencing technologies in the study of soil microbial communities, PCR-DGGE method due to various advantages with less hassle, cost and time and immediate presentation of components in both qualitative and semi-quantitative form is still an important way to study the impact of various agricultural practices and managements on microbial communities. With the help of the findings of this technique, the best management methods in agriculture could be selected and the way can be paved for the realization of sustainable agriculture and stable food supply. In this review, some researches and references that have used the efficacy of PCR-DGGE in studying the impact of various agricultural managements and activities on the composition and diversity of soil microbial communities and some of their results have been mentioned. The features, advantages, limitations, and principles of this method have also been outlined.

Zinc (Zn) is an essential element for plants growth at low concentrations and at high concentrations, it acts as a heavy metal and soil pollutant. Biochar is used to improve soil quality, plant growth and also to reduce the availability of heavy metals in contaminated soils. The biochar behavior in soil and its effect on Zn availability rely on the feedstock nature and pyrolysis temperature. This study aimed to investigate the effects of produced biochars on Zn bioavaiability in two acidic and alkaline soils with different levels of applied Zn, during one year-long incubation.

The experiment was conducted as a factorial split arrangement in a completely randomized design in two acidic and alkaline soils, with two factors including biochar types at 9 levels and extraction times at 12 levels with two replications. Four types of biochar were produced from rice straw (RB) and apple wood waste (WB) biomasses at two pyrolysis temperatures (300 and 600 °C). Two acidic (pH=5.8) and alkaline (pH=8.1) soils were collected and treated with 3 levels of Zn (0, 10, and 200 mg kg-1) from zinc sulfate (ZnSO4.7H2O) source. Biochars were added to soils in two doses (1 and 4 % w/w) and incubated at around FC moisture condition for 360 days at 25±2◦C. The pH, EC, moisture content and DTPA extractable-Zn were measured in the studied soils at 12 designated extraction times (0.25, 1, 3, 5, 15, 30, 60, 90, 120, 180, 270 and 360 day).

In acidic soil and Zn level of 200 mg kg-1, levels of 1 and 4 % biochars caused the significant decrease in DTPA-Zn concentration and the elapsing of time had a significant effect on the reduction of DTPA-Zn concentration and maximum decrease (48 %) was observed in the treatment of 4% RB600 and 360th day (p<0.05). At the Zn levels of 0 and 10 mg kg-1, in acidic soil, DTPA-Zn concentration was significantly increased in 4% RB300, 1% RB600, and 4% RB600 treatments, and passage of time had a decreasing effect on it and DTPA-Zn concentration significantly reduced with time in 4% WB300 treatment compared to the control (without biochar). A significant increase of pH in acidic soil was observed in 4% RB600 and 4% WB600 treatments during the 360 days of incubation while the significant decrease was showed in 4% WB300 treatment. In alkaline soil and under Zn=0, the maximum increment of DTPA-Zn concentration compared to the control (without biochar) was obtained in 4% RB600 treatment but the elapsing of time had a significant reduction effect on it. In alkaline soil at Zn level of 10 mg kg-1, only the 4% WB300 treatment could significantly decrease the concentration of DTPA-Zn over time, but in the same soil at the level Zn of 200 mg kg-1, the significant decrease of DTPA-Zn concentration was observed at the 4% RB300, 1% RB600, 4% RB600 and WB300 4% treatments. A significant decrease in alkaline soil pH was observed in the 4% RB300 and 4% WB300 treatments and an increase in electrical conductivity (EC) in both acidic and alkaline soils was observed in rice straw-derived biochars treatments.

Although the application of rice straw derived biochar (pyrolysis at 600 °C) decreased the availability of Zn in both acid and alkaline soils with the high level of Zn (200 mg kg-1), it did not have a negative effect on Zn availability in normal levels of Zn (0 and 10 mg kg-1) and even increased the concentration of DTPA-Zn in both acidic and alkaline soils under without Zn application conditions.

Photosynthetic parameters are the most sensitive process in the physiological metabolism of plants that are affected by irrigation regime and silicon fertilization. Thus, silicon is one of the effective elements in increasing the net rate of leaf photosynthesis, water use efficiency, stomatal conductance and intercellular carbon dioxide. Therefore, the aim of this study was to determine the effects of different levels of silicon sources and irrigation regimes on rice.

A pot experiment was conducted to investigate the effect of different levels of silicon sources and irrigation regimes on rice photosynthetic parameters at Sari Agricultural Sciences and Natural Resources University in 2018. The experiment was laid out in a split-factorial design with three replications. In this design, soil texture was considered as the main-plot factor, and irrigation regime and different levels of silicon sources as factorial-subplot factors. Factors included two Si doses of 60 and 120 mg Si Kg–1 as potassium silicate (Ps), sodium silicate (Ss), calcium silicate (Cs) and biochar (Bi) sources under two irrigation regimes (continuous flooding (W1) and periodic wetting-drying (W2)) in two soil series with different textures (Sandy-loam (S1) and Silty-clay (S2)). After plant growth, dry matter weight of straw and photosynthetic parameters such as relative leaf moisture content, transpiration intensity, stomata conductance, chlorophyll index and photosynthesis were measured in flag leaf at the flowering stage of rice.

The results showed that the highest leaf relative moisture content (63.80%), transpiration intensity (12.03 mmolm-2s-1), stomata conductance (384.79 mmolm-2s-1), chlorophyll content (55.00), photosynthesis rate (24.33 µmolm-2s-1) and dry matter weight of straw (33.3 gr/pot) were observed in plants treated with potassium silicate at a concentration of 120 mg Si Kg–1 of silty-clay soil under continuous flooding irrigation regime. The lowest dry matter weight of straw and photosynthetic parameters were observed in sandy-loam soil under periodic wetting-drying irrigation regime without using silicon fertilizer. Also, in sandy-loam soil, the leaf relative moisture content (58.95%), transpiration intensity (11.20 mmolm-2s-1), stomata conductance (340.32 mmolm-2s-1), chlorophyll content (51.80), photosynthesis rate (19.55 µmolm-2s-1) and dry matter weight of straw (18.6 gr/pot) was the highest in biochar treatment at a concentration of 120 mg Si Kg–1 under continuous flooding conditions. Also, a decrease in dry matter weight of straw and photosynthetic parameters was observed at the higher Si rates (120 mg Si Kg–1 compared to 60 mg Si Kg–1) in treatments of potassium silicate and sodium silicate in sandy-loam soil under periodic wetting-drying irrigation regime. This may be due to the inhibitory effect of high concentrations of silicon on photosynthetic function.

Although most of the photosynthetic parameters of plants and dry matter weight of starw in periodic wetting and drying irrigation regime were somewhat reduced compared to continuous flooding irrigation regime, application of different sources of silicon to both soil textures under both irrigation regimes improved relative leaf moisture content, transpiration rate, stomata conductance, chlorophyll content, photosynthesis rate and dry matter weight of straw were compared to treatments without silicon fertilizer application. This reflects the protective effect of silicon against low irrigation conditions. Therefore, in the scope of this experiment, it seems that the use of silicon to improve the photosynthetic parameters of rice plant and dry matter weight of straw under low-irrigation regime was satisfactory. But, the amount of use of this element is very important to maintain the balance of soil and plant properties.

Citrus trees are sensitive to zinc deficiency and zinc deficiency in citrus trees is a common nutritional disorder that causes changes in the anatomy, morphology and cytology of citrus trees, leading to reduced flowering, fruit set, performance and production stability. Due to the limitation of zinc in the soils and the economic importance of citrus for Mazandaran province, the study of zinc status in citrus orchards and the management of Zn application (accordance to growth phenology) and its effect on Zn deficiency and quality of Thomson Navell fruits were conducted.

To study zinc(Zn) status and its effect on yield and quality of Thomson navell orange, two separate experiments were conducted in East of Mazandaran Province, Iran. The first experiment was conducted in citrus orchards of the region, and the second, as a randomized complete block design with seven treatments and four replications was conducted in an orchard of Thomson navel on sour orange rootstock. Treatments included: 1- First control (without zinc); 2- Second control (without zinc and with urea spray); 3- 200 g zinc sulfate per tree as soil application, before leaf development; 4- 200 g zinc sulfate per tree as fertigation, in the first stage of fruit growth; 5- 200 g zinc sulfate per tree as fertigation, in the first and second stages of fruit growth; 6- zinc sulfate spraying in the first stage of fruit growth; 7- zinc sulfate spraying in the first and second stages of growth.

The first experiment showed that the orchards of Behshahr and Galogah had the lowest deficiency symptoms and Ghaemshar and Juybar had the most deficiency symptoms. The results of the second experiment showed that soil application before leaf development had no effect on chlorosis, yield, fruit and zinc concentration in leaf and fruit, but its application as fertigation and spraying increased fruit yield, diameter, and fruit weight, in leaf and fruit zinc concentration. The highest leaf Zn concentration was obtained from spray treatment in the first and second stages of fruit growth. Fertigation treatment significantly increased the root Zn concentration compared to the control.

Generally, according to the results of this experiment, for orchards with a history of mild symptoms of zinc deficiency or probable zinc deficiency, the application of zinc sulfate as fertigation or spray after petal fall in the first stage of fruit growth is recommended, However, for orchards that have severe symptoms of zinc chlorosis, two fertigation or foliar application with zinc sulfate at the first and second stages of fruit growth is recommended.

Biochar application is one of the effective methods to reduce the harmful effects of heavy metals in contaminated soils. Biochar is an organic amendment may change some of the chemical properties of the soil and create suitable conditions for immobilizing of heavy metals in the soil. Biochar is a carbon solid obtained from the pyrolysis of residues under limited oxygen conditions. Biochar have high surface area, porous structure, and functional groups, which can reduce the risk of heavy metal contamination in the soil and their entry into the food chain. The aim of this study was to investigate the effect of sugarcane bagasse biochar produced at 400 and 600 °C on the availability and fractions of Cd in saline and cadmium-contaminated soil.

Initially, 15 mg kg-1 Cd as cadmium chloride was added to sandy soil sample (200 g) and mixed with the soil. The soils were incubated for 3 weeks at 25±2 °C at a moisture content of 80% field capacity in incubator. After incubation period, salinity levels of 1170 and 2340 mg kg-1 as sodium chloride was added to the soils. Then, the 1% (w/w) of the sugarcane bagasse and biochars produced at 400 and 600 °C were added to the soil and incubated for 3 months at 25±2 °C. At the end of the incubation period, a soil sample was removed from each of the treatments and available Cd (DTPA) and its fractions (Tessier et al. 1979) were extracted.

The results showed that the application of biochar reduced Cd extracted by DTPA (p<0.05). Also, effect of biochar on pH wasnot significant (p>0.05) and increased EC (p<0.05). Salinity increased Cd extracted by DTPA (p<0.05). Also, biochar application reduced exchangeable Cd (13.7%) and Cd associated with carbonates (24.1%), while, increased Cd associated with oxides (37.2%) and residual (30.6%) compared to control. Cadmium associated with Fe/Mn oxides and associated with carbonates in 2340 mg kg-1 treatment compared to 1170 mg kg-1 treatment increased 31.5 and 25.8% respectively. The results reveled that Cd associated with OM in 1170 and 2340 mg kg-1 treatments compared control reduced 38.8 and 22.2% respectively. Also, residual Cd reduced (24.9%) in 2340 mg kg-1 treatment compared to 1170 mg kg-1 treatment.

Application of sugarcane bagasse biochar in soil led to change Cd from unstable fractions (exchange and associated with carbonates) to stable fractions (associated with Fe/Mn oxides and residual), therefore reduced the mobility of Cd in saline calcareous sandy soil.

Corn is considered as one of the most important and strategic cereals in the world that needed a lot of nitrogen fertilizer and often this need is supplied by chemical fertilizers. In addition to the severe need to fossil fuels for chemical fertilizers production, they are also important environmental pollutants (23). Therefore, organic fertilizers such as green manures of legume species can be a good alternative to chemical fertilizers. Also, conservation tillage operations that are accompanied by proper management of crop residues, it is an appropriate solution to prevent the elimination of residues in sustainable agriculture, and plays an important role in improving the physicochemical and biological properties of soil, and can lead to increasing crop yield (22). Therefore, developing and promoting the use of green manure and conservation tillage operations is essential. Therefore, the present study investigates the effect of organic fertilizer application on corn yield under different tillage levels.

This experiment was carried out as split plot in randomized complete block design with three replications at 2018-19 in a farm located in Ghale-No village, Zahak city. Vetch (Vicia villosa) was used as a green manure in this study. The experimental treatments were included two levels of green manure, consumption and no consumption as main factors; and three levels of tillage, no tillage, minimum tillage and conventional tillage as sub plots. In this experiment agronomic traits of plant height, dry and fresh forage yield and seed yield; ecological traits of weeds biomass, photosynthetically active radiation, soil moisture percentage and soil temperature; and some soil physicochemical properties such as soil porosity, bulk density, particle density, organic carbon and nitrogen percentage were evaluated. Data analysis was performed with SAS software.

The experimental results showed that the highest amount of dry and fresh forage yield and seed yield, photosynthetically active radiation, soil porosity percentage, soil organic carbon and nitrogen percentage was obtained from green manure consumption and conventional tillage treatment and there was no statistically significant difference between the consumption of green manure under conventional and minimum tillage conditions. The lowest amounts of the above traits were obtained in the treatment without green manure and no tillage. In addition, the treatment green manure consumption and no tillage system resulted in obtaining the highest soil moisture percentage and the lowest soil temperature. For weed biomass, it was also found that the use of conventional tillage significantly reduces weed biomass, but green manure consumption hadn’t any significant effect on weed biomass.

In this experiment, it was shown that the green manure consumption by increasing the amount of soil organic matter and improving soil structure increased the amount of access to nutrients, especially nitrogen for the plant, which led to enhancing plant yield and growth. Also, increasing the soil porosity and reducing the soil bulk density under the influence of minimum tillage led to soil structure improvement, and it increases the root permeability in soil which this allows the plant to absorb more water and nutrients. Therefore, according to the results of this experiment, it can be suggested that the combination of green manure consumption with minimum tillage can create a good yield in corn cultivation in the study region.

Soil as a living system is one of the factors affecting the balance of the ecosystem and many processes, especially on a small scale, take place in it. Soil microorganisms play an important role in maintaining soil quality through decomposition of organic material and nutrient cycling. The use of microorganisms in ecosystems whose biological community stability has been severely compromised due to high consumption of fertilizers, salinity and chemical toxins, is to improve the efficiency of nutrient consumption and biological control of pests and diseases. Soil organic matter increases soil microbial activity. On the other hand, enrichment of organic matter with microorganisms increases their nutrients release. To understand the vital role of soil microorganisms in the release and storage of energy and nutrients in the soil, in recent years, increased attentions has been paid to the estimation of microbial biomass in the soil. Therefore, the aim of this study was to investigate the effect of urea, Streptomyces inoculation and wheat straw on available phosphorus, microbial respiration, microbial biomass C, metabolic coefficient and microbial biomass turnover time.

This study was conducted under controlled laboratory conditions. A factorial experiment with two levels of urea (0 and 1.6 g/100g wheat straw), two levels of Streptomyces sp. (0 and 5%) and wheat straw treatments (0 and 1%, w/w) was conducted using a completely randomized design with three replications. Wheat straw was treated with the urea fertilizer and Streptomyces sp. inoculum firstly and the treated straw was then thoroughly mixed with the soil. The mixtures were incubated at 25±2 ° C for 90 days. Microbial biomass C and available phosphorus were measured monthly for three months and microbial respiration was measured weekly. To revive the microbial population, the containers were pre-incubated at room temperature for two weeks and soil moisture was adjusted to about 70% of the field capacity.

Streptomyces inoculation, addition of wheat straw and urea increased available phosphorus concentration, respiration and soil microbial biomass C. In this experiment, the amount of respiration and microbial biomass C with the simultaneous addition of Streptomyces, wheat straw and urea to the soil was the highest and the effect of Streptomyces inoculation on wheat straw on the studied parameters was more than the two other factors. The lowest amount of microbial respiration, microbial biomass C and phosphorus was in control soil (without urea, Streptomyces and wheat straw). Addition of wheat straw to the soil increased microbial respiration and microbial biomass C by providing the required substrate. Also, the use of wheat straw and urea led to an increase in soil available phosphorus.

The results of this study showed that in carbon-restricted soils, the use of plant residues enriched with Streptomyces and urea increased microbial respiration and microbial biomass carbon in the soil. Also, wheat plant residues addition to the soil increased the soil available phosphorus. Treatment of soil with Streptomyces also increased soil available phosphorus, which was more perceptible in the plant residues enriched with Streptomyces. The results show that the simultaneous application of plant residues, urea and Streptomyces, has increased soil microbial activity. Therefore, in carbon-restricted soils, increasing the level of organic matter and its enrichment can lead to increased microbial activity and biological potentials in the soil.Keywords: Microbial biomass C, Microbial respiration, Plant residue, Streptomyces, Urea

Land suitability evaluation is one of basic efforts to sustainable managements of any region. Shortcomings in traditional land suitability evaluation assessments have drawn the attention of this field users to use of artificial intelligence and multi-criteria decision making methods. Subsystems of mentioned methods alone or in the combination with each other were used to increase accuracy of evaluation, simplify of calculations and achievement of useful side results. Fuzzy-Delphi approach is one of discussed methods that in this study, its efficiency has been measured behind investigating of Horand region potential for irrigated wheat production.

In this study, 662 ha of lands in Horand region were selected in the form of 12 land units and after completing the climate, landscape and soil database, the Fuzzy-Delphi method was applied to qualitative and quantitative land suitability evaluation of irrigated wheat. The qualitative evaluation was done by land index determination and the quantitative one was completed based on predicted yield which calculated by combination of archived potential yield from Agro-ecologic method with soil index. In this regard, the Delphi method was used to select and determine weights of the factors which are involved in the evaluation based on the experts’ opinion and were validated by Kendall coefficient. The properties matrix which obtained from fuzzyization of land properties with kandel membership function were combined with weight matrix and leads to suitability matrix. The suitability zoning of the study area were identified according to suitability classes which were determined based on resulted soil and land index from defuzzification of suitability matrix with triangle Tnorm way. Validation of Fuzzy-Delphi method was done by conventional statistical tests.

According to experts’ opinion, the 8 properties (Climate, slope, texture, calcium carbonate equivalent, gypsum, EC, drainage and flooding) of studied lands with Entisols and Inceptisols, were selected for land suitability evaluation that climate and gypsum have had maximum and minimum weight respectively, that its accuracy was confirmed by an incompatibility rate of 0.07. The conformed suitability evaluation showed S1 to S3 classes by qualitative and quantitative methods for irrigated wheat utilization type with limitation of slope, salinity, texture and gypsum. Difference of land units classes in qualitative and quantitative methods was seen only in one land unit which quantitative one take lower class. According to mean management index of 0.73, the middle management level was estimated for region. Chi-square value of 1.32, r2 0.91, RMSE 2.1% and GMER 1.34 obtained in the validation of Fuzzy-Delphi method.

Applying main agricultural lands users opinions in selecting and valuating land suitability evaluation parameters, combination of characterize weight with their rating and also considering intermediate classes, identified as the main advantages of the studied model over traditional methods that introduced the fuzzy-Delphi approach as an efficient method based on estimation of the land potential. The reliability of mentioned approach was confirmed by checked statistical accuracy and validity although with little over estimation. Beside main finding of this research work, coordination of qualitative and quantitative suitability evaluation with discussed approach, possibility of ranking the land limitation remove by sub data and also, pay attention to the land suitability class along with the management index for future land management planning are the cases that can be useful for researchers and executive experts. However, in order to find other capabilities of the model and recommending its use at the wide level, it is suggested to run this new model in different areas for various utilization types.