Iranian Journal of Soil Research
Year:2019 | Volume:33 | Issue:1 |Papers Count:13

In order to achieve sustainable agriculture, improving soil characteristics by proper residue management is necessary. The objective of this research was to compare the effect of conservation tillage (reduced tillage and no tillage) and the effect of wheat residues management on some soil properties and corn yield. Tillage treatments included three levels of reduced tillage by disk, reduced tillage by combined machine, and no tillage (chisel packer). Wheat residue-management treatments consisted of removing the residue by burning (conventional method) and retention of 100%, 75% and 35% of residue. This experiment was performed as split block in randomized complete block design with three replications. According to the results, the two reduced tillage treatments were in one statistical group and no tillage was in another, with the grain yield of 12370 kg/ha. Grain yield in reduced tillage using chisel packer was more than the yield of no tillage by 635 kg/ha. In the two methods of reduced tillage, the corn yield was more than the yield of no tillage by about 5%. Soil organic carbon and potassium (K) were affected by tillage method and residue, so that burning the residue treatment in all three tillage treatments had the least soil organic carbon (SOC) and the highest available phosphorus (P) and potassium (K). Interaction effect of tillage and residue management in year showed that, in the third year, burning of the wheat residue in reduced tillage condition had the highest available potassium in the soil. In the third year of the experiment, soil organic carbon in the residue retention treatments increased by, respectively, 13%, 19%, and 19%. In the same year, reduced tillage by using chisel packer increased the soil organic carbon (SOC) about 8% by preserving the 75% of residue. Based on the results of this research, for the region of study, burning of the plant residues should be avoided and retention of 35-75% of residue and using reduced tillage methods is recommended.

One of the problems associated with the production of granular microbial fertilizer is the elimination of bacteria in the drying process of fertilizer. One solution for this problem is using thermal resistant phosphate solubilizing bacteria (PSB). In this study, the efficiency and effectiveness of some PMFs prepared by using two thermal resistant PSB (isolates RPS9 and RPS7) and one thermal sensitive PSB (isolate RPS4) in the basal formulation of rock phosphate (45 g), bagasse (30 g) and sulfur (15 g) were evaluated on the maize growth. The experimental design was CRD with 7 treatments including control treatment (without chemical and microbe fertilizer), triple super phosphate fertilizer treatments at the rates of 100% and 50% of the fertilizer recommendation (equivalent to 300 and 150 mg/kg soil, respectively), with bacterial treatments (RPS4, RPS7, and RPS9), in three replications. The results obtained from the greenhouse experiments showed that total wet and dry weight of the plants and uptake of phosphor in the root and shoot of corn S. C. 704 were significantly influenced by the PMFs. RPS4 bacteria treatments had similar performance to triple super phosphate 100% and RPS9 had similar performance to 50% triple super phosphate. RPS7 had lower performance than the other two bacteria. From the two heat resistant isolates that were recently isolated and both belonged to the species Pantoea agglomerans, RPS9 seemed more promising for this purpose.

Soil tests play a very important role in management of nutrients in the field. Critical level of soil nutrient elements in a region is the basis of interpretation of the soil test for the same region. Therefore, these tests should be carried out in the soils of the target areas, so that the soil test could be used for fertilizer recommendation. Beans (Phaseolus vulgaris L. ) with high protein content are an important crop that is cultivated in Markazi province. Due to the lack of information on phosphorus critical level and regional calibration, this study was conducted on soil under bean cultivation in Markazi province. Twenty-three soil surface samples (0-30 cm) were selected with wide range of soil properties and phosphorus concentration (extracted with Olsen method) from the different locations of the province and were prepared for greenhouse cultivation. Bean plant responses were investigated by application of two levels of phosphorus (0 and 50 mg kg-1 soil as mono calcium phosphate) in greenhouse experiment. The study was conducted in factorial experiment as complete randomized design with three replications. At the end of vegetative period, the aboveground parts of plants were cut, and plant responses including, dry matter weight, phosphorus concentration, total phosphorus uptake, and relative yield were determined. Analysis of variance showed that the main effects and interaction of soil and phosphorus fertilizer were significant at 1% probability level for dry matter weight, phosphorus concentration and phosphorus uptake. The mean comparison of plant responses was significant as affected by phosphorus fertilizer consumption. By using Cate-Nelson graphic method, the critical level of phosphorus in soils was determined to be 13 mg kg-1. Dry matter showed positive significant correlation with available phosphorus and organic carbon. The total phosphorous uptake showed a positive significant correlation with available phosphorous concentration, electrical conductivity, sand and organic carbon content, and a negative significant correlation with clay content.

Mycorhizal fungi increase uptake of phosphorus and other mineral nutrients from unavailable sources. Plant hormones promote root production (rhizogenesis) and thus affect plant growth by increasing uptake of nutrients. Thus, the present study aimed to assess the effects of plant hormones and mycorhizal fungi on yield and macronutrient concentrations of potato (Fontane cultivar). For this purpose, a factorial experiment was conducted in the greenhouse using a randomized complete block design and three replications. The experimental factors were types of plant hormones sprayed [without hormone (control), gibberellic acid (GA), indole acetic acid (IAA) and naphthalene acetic acid (NAA)] and soil inoculation with mycorhizal fungi [without inoculation (control) and inoculation with Funneliformis mosseae, Rhizophagus intraradices, and Funneliformis mosseae + Rhizophagus intraradices]. There were significant effects due to soil inoculation by mycorhizal fungi and application of plant hormones on fresh yield, diameter, dry matter content and concentrations of nitrogen, phosphorus and potassium of potato tuber. The highest fresh yield, dry matter content and nitrogen concentration of potato tuber were measured in treatments inoculated by Funneliformis mosseae + Rhizophagus intraradices and sprayed with GA. The highest diameter and potassium concentration of potato tuber were obtained from the treatments inoculated by Funneliformis mosseae and sprayed with GA. The treatments inoculated by Rhizophagus intraradices and sprayed with NAA had the highest concentration of phosphorus in the tuber. Generally, the results of this study indicate that inoculation of soil by mycorhizal fungi and spraying potato plant with growth hormones increase yield and macronutrient concentrations of potato tuber.

Salinity stress is one of the most important problems in agriculture sector, especially in dry and semi-dry land regions of the world. To evaluate salt tolerance of different varieties of barley, cotton, canola, and forage sorghum, some experiments were conducted in Salinity Research Farm, National Salinity Research Center, Yazd, Iran. Species and cultivars included barley (Rodasht, Afzal. Line1 and Line4), cotton (Siokra, Bakhtgan and Varamin varieties), canola (Hyola401, Hyola420, Rindow, Zarfam, SLM, Sarigol, Talent, Option500, Option501, RGS, Opera, Elite, Mozart, CV. Star, CV. Roby, SYN, Milena, Okapi and GoldRush), and forage sorghum (KFS1, KFS2, KFS3, KFS4, Speedfeed, Sugargraze, Jumbo, and Nectar varieties). These were tested by irrigated water treatments with salinity of 2 to 14 dS. m-1 for two years. Results of the experiments showed that there were some inter and intra species differences in salinity tolerance. Generally, salinity tolerance indexes of barley and cotton were 18. 70 and 13. 80, respectively. The parameter C50, which indicates 50 percent reduction in yield, was 18 and 12. 6 dS/m for barley and cotton, respectively. The salinity tolerance threshold values of the barley and cotton species were 3. 6 and 4. 6 dS/m, respectively, based on two linear models. The slope of decreasing yield for this species was 3. 6% and 5. 7%, respectively. The most salinity tolerant variety among the studied varieties were Rodasht for barley, Siokra for cotton, varieties Hyola420, Hyola401, Option501, Mozart and RGS for canola, and Speedfeed for hybrid sorghum and Line KFS3 for local varieties of sorghum. It should be noted that, for selection of tolerant varieties, in addition to threshold values, other parameters like absolute yield, STI and Tol indices need to be considered.

Due to recent drought periods in Hormozgan province, boron toxicity has been increased significantly. One of the applicable practices to rectify toxicity of boron is application of some nutrients such as silicon to the plant growth medium. To investigate this phenomenon, an experiment with the following treatments was designed and conducted. Six levels of boron, i. e. 0, 5, 10, 20, 40 and 80 mg B per kg of soil from the H3BO3 source and four levels of silicon, i. e. 0, 70, 140 and 280 mg Si per kg of soil from the Na2Si3O7 source, in four replications on potted mango seedlings. Seven-month old seedlings were harvested and B, Si, N, P, K, Na, Ca and Mg were measured in the plants tissue. The results indicated that application of the highest level of B resulted in high concentration of boron with different ratios in different tissues. The average concentration of B measured for the leaves was 2. 4 X and root 1. 2 X compared to the stem tissue. With increasing levels of boron, nitrogen concentration in leaves and roots decreased by 11. 8% and 4. 2%, respectively, and in opposite direction, nitrogen increased in the stems by 6. 9%. However, at high levels of boron, with increased application of silicon, phosphorus concentration of the leaves exhibited an upward trend. Concentration of potassium in mango leaves increased by increasing levels of boron and silicon, but it was the opposite in the stem and root where the trend was decreasing. Interaction effects between boron and silicon in lower levels of boron was found a decreasing effect in absorption of calcium, which changed the direction to increasing effect in higher levels of boron. The interaction was always a decreased effect on concentration of magnesium. In overall, excessive boron caused a negative effect on concentration of nitrogen, phosphorus, and magnesium, and a positive effect on concentration of potassium and calcium. However, silicon application failed to exhibit a generally impressive correction role to suggest for field conditions.

Application of N fertilizer to soil is known as an effective practice for crop yield improvement, but its inappropriate use could result in N loss, which is important from both environmental pollution and economic feasibility standpoints. Therefore, one of the great concerns lies in finding suitable methods for effective use of N fertilizers. Research on the effects of simultaneous application of biochar, resides, and nitrogen fertilizer on plants growth and chemical composition, especially N use efficiency (NUE), is very limited. In this study, an experiment was designed according to a completely randomized factorial design, in which the treatments consisted of three levels of urea (0, 100 and 200 mg N kg-1) and four levels of biochar/residue (0, 2% biochar, 2% crop residue, and 2% biochar+crop residue) with three replication. Biochar increased the uptake and concentration of N and P in spinach shoots as compared to the control, but had not effects on the uptake of Fe, Mn, Cu and Zn. Results indicated that biochar and crop residue had a positive effect on N use efficiency, especially at 100 mg kg-1 level of urea. Results also showed that co-application of biochar and residues with urea significantly improved plant wet and dry matter yield. Due to the desirable effects of biochar and residues application on plant responses and improving nitrogen use efficiency, more attention should be paid to the use of such materials in fertilizer recommendation programs. Before making recommendations, further investigations under field conditions are crucial to verify the results of the present study.

Development of a land evaluation decision support system to identify the suitable lands for selected crops is necessary. The aim of the present research was to develop a land suitability evaluation system based on the FAO framework, with some modifications to suit the local conditions. For this purpose, a model was made by GIS capability and integrated with modeling function using Visual Basic. This model was based on a hierarchy process rather than a set of AHP model. For equilibration of the model, soil data were obtained from 60 soil profiles located in Amol region (Mazandaran Province, Iran), covering about 3200 ha. Fourteen land characteristics and their suitability degrees were determined and categoried in eight land qualities. The results of F test between land indexes calculated by FAO method and Decision Support Tool were not significantly different (P>5%). Also, the calculated correlation coefficients between land index and observed production by Decision Support Tool method was r= 0. 85, more than that of FAO (r= 0. 77). Besides, the overall overlap between the FAO and Decision Support Tool with the observed production point map was 86% and 95. 4 %, respectively. Thus, Decision Support Tool provided good results by using land qualities and considering local conditions. Finally, based on these results, it can be concluded that the developed system can help farmers and experts as a decision support tool.

Sodic soils are widely spread in arid and semiarid regions. To use sodic soils for crop production, reclamation of physico-chemical properties of these soils is necessary. To study the effects of different levels of gypsum (0, 50 and 100% of gypsum requirement) alone and with three levels of organic carbon (0, 1. 5 and 3% w/w) from different sources (alfalfa and corn residue, saw dust and date fruit waste) on some properties of a sodic soil, a factorial experiment was conducted with 27 treatments and three replications using a completely randomized design. After application of gypsum or gypsum+ organic matter to the sodic soil, the physic-chemical properties of it were measured every 15 days. The studied soil was leached at the end of the incubation time. The results showed that the physicochemical characteristics of the sodic soil improved with the increase in incubation time. Before performing leaching treatment, the application of gypsum equal to gypsum requirement had the greatest impact on decreasing SAR, ESP, and dispersible clay (DC). Maximum microbial respiration rate was obtained from the application of 3% organic carbon from date fruit waste. The application of organic materials + gypsum had the greatest impact on improvement of sodic soil behaviors after leaching. The addition of organic matter caused some characteristics of sodic soil to become undesirable before leaching. After leaching, pH, SAR, ESP, DC and hydraulic conductivity (HC) decreased in all treatments. The treatment of gypsum at the rate of 100% gypsum requirement + 3% organic carbon from date fruit waste was the most effective reclamation treatment for the sodic soil. The organic materials + gypsum had the maximum reclamation effect on sodic soils, when the soils had been leached two months after incubation.

The effect of water quality on soil water retention, structure, and hydraulic conductivity in two soil textures was studied. Undisturbed soil samples were treated in 5 wetting and drying periods with 6 different types of water quality consisting of 2 levels of EC (0. 2 and 10 dS m-1) and three levels of SAR (1, 5 and 12). Undisturbed soil samples were equilibrated on sand box apparatus to soil matric suctions of 0, 10, 20, 40 and 60 cm and on pressure plate apparatus to soil matric suctions of 100, 300, 1000, 2000, 4000 and 15000 cm. The van Genuchten-Mualem model was fitted to simulate the measured soil water characteristic curve. Soil physical quality index (S) and the inflection point of water retention curve (θ INFL) were evaluated using fitted parameters. Also, the macro-porosity, meso-porosity, micro-porosity, available water content (AWC100 and AWC300), and saturated hydraulic conductivity were measured. The study was conducted in a completely randomized design with three replications. Results showed that increasing EC caused soil particles flocculation, by developing some new pores and, consequently, increasing water retention capacity. Although increase in SAR dispersed soil particles, alteration of some macro-pores and meso-pores to micro-pores enhanced water retention, especially at high matric suctions. But, the available water content did not change significantly. Also, increase in water EC enhanced water retention at all matric suctions and the highest moisture content at inflection point was seen at EC of 10 dSm-1. The increase in SAR and decrease in EC were directly related to decrease in saturated hydraulic conductivity. Soil physical quality index (S) decreased by sodium increment, which indicated the reduced soil physical quality.