Soil science
M. Bazi Abdoli; M. Barani Motlagh; A. Bostani; T. Nazari
Abstract
IntroductionOrganic matter and alkaline pH are the main causes of nutrient deficiencies in calcareous soils of arid and semi-arid regions. The availability of some nutritional elements, including the micronutrients such as iron, zinc, copper, and manganese is very low in calcareous soils, although the ...
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IntroductionOrganic matter and alkaline pH are the main causes of nutrient deficiencies in calcareous soils of arid and semi-arid regions. The availability of some nutritional elements, including the micronutrients such as iron, zinc, copper, and manganese is very low in calcareous soils, although the total concentration of these elements may be relatively high. Burning crop residues results in substantial loss of nutrients, and may lead to air pollution and human health problems. An alternative approach is to apply crop residues to soil in the form of biochar. The biochar modification with acid may increase the solubility of nutrients (P, Fe, Zn, Cu, Mn) present in biochar, thereby significant improvement in mineral nutrition of plants grown in calcareous soils. Therefore, the object of this study is to investigate the effect of acid-modified biochar from rice residues on the amount of chlorophyll and the micronutrient concentration of quinoa plant (Chenopodium quinoa) in a calcareous soil. Methods and MaterialsThe soil was air-dried and ground to pass through a 2-mm sieve then was analyzed to determine various soil physico-chemical properties using standard methods. To achieve the aim of this study the factorial experiment was carried out based on a completely randomized design in 4 replications. Factors include 3 types of biochar (unmodified, modified by pre-acidic method and modified by post-acidic method) and different levels of biochar (0, 2, and 5% by weight). Then 10 quinoa seeds were planted in each pot at 2-cm depth which after emergence, declined to 3 plants in each pot. The pots were randomly moved twice a week during the growth period to eliminate environmental effects. Irrigation and weeding operations were performed by hand. Determination of chlorophyll content (a, b, and ab) and carotenoids were measured precisely before harvesting in fresh plants using Arnon method. Plants were harvested at 187 days after planting, washed with distilled water and dry with tissue paper. The samples were air-dried and then oven dried at 65˚C to a constant weight in a forced air-driven oven. Then the total micronutrient content of the plant was determined after dry ashing. The statistical results of the data were analyzed using SAS software (9.4) and LSD test (at 5% level) was used for comparing the mean values. Results and DiscussionBased on the variance analysis, all attributes responded positively to different types and levels of biochar and modified biochar (p<0.01). The comparison of the average effect of the studied treatments showed that with the increase in the levels of all three types of biochar, the amount of chlorophyll a, b, total, and carotenoid increased so the highest amount of chlorophyll a, b, total, and carotenoid respectively, with an average of 2.58 and 1.54, 4.13 and 1.36 mg g-1 were obtained from the treatment of 5% post-acidic biochar. The results showed that the highest amount of Fe concentration in shoots with an average of 229.48 mg kg-1 was obtained from the treatment of 5% post-acidic biochar, although there was no statistically significant difference with the treatment of 5% pre-acidic biochar with an average of 220.48 mg kg-1 and its lowest value with an average of 95.95 mg kg-1 was related to unmodified biochar. The highest amount of Zn concentration in shoots with an average of 13.42 mg kg-1 was related to the treatment of 5% post-acidic biochar which showed an increase of 13.24 and 33.26% compared to the treatment of 5% pre-acidic and unmodified biochar, respectively. Also, the highest concentrations of Cu and Mn in shoots were obtained with an average of 3.85 and 23.37 mg kg-1 respectively, from the treatment of 5% post-acidic biochar. ConclusionPost-acidic biochar had better results in terms of physiological indices and the concentration of micronutrients (Fe, Zn, Cu, and Mn) than unmodified biochar in quinoa. The increase of nutrients in quinoa can be attributed to the dissolution of biochar nutrients after being modified with acid and the reduction of pH and the availability of these elements in the soil. Therefore, biochar modified with acid or biochar produced from sources that have acidic properties can be recommended as a suitable method for improving fertility and increasing micronutrients in calcareous soils affected by salt.
A. Jahandideh; M. Barani; E. Dordipour; R. Ghorbani Nasrabadi
Abstract
Introduction: One of the most important needs in the farm planning is the evaluation of different systems of plant nutrition. By supplying the correct way of plant nutrition, one can preserve the environment and increase the efficiency of agricultural inputs. Humic acid contains many nutrients that increase ...
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Introduction: One of the most important needs in the farm planning is the evaluation of different systems of plant nutrition. By supplying the correct way of plant nutrition, one can preserve the environment and increase the efficiency of agricultural inputs. Humic acid contains many nutrients that increase soil fertility, soil organic matter content, and access to macro- and micro-nutrients by preventing the formation of insoluble salts and chelating properties. Phosphorus and humic acid stimulate vegetative growth, improve reproductive growth, and increase the quantitative and qualitative yield of plants. In this regard, the positive effects depend on the amount and how they are applied. The present study was conducted with the aim of investigating the effects of different levels of humic acid and phosphorus fertilizer on phosphorus availability and photosynthetic pigments (a, b and carotenoids) in canola (cv. Hyola 50).
Methods and Materials: The soil used in this study was collected from 0-30 cm layer of a soil profile passed through a 2-mm sieve after air-drying. The soil chemical and physical properties were then determined. The pot experiment was conducted as factorial based on completely randomized design with three replications. Treatments include phosphorous fertilizer as super phosphate in three levels (0, 50 and 100 mg/kg) and humic acid in three levels (0. 0.5 and 1 gr/kg soil), phosphorous and humic acid application ways. Humic acid and phosphorous treatments were mixed in various forms including simultaneous mixing of humic acid and phosphorous fertilizer in the soil matrix, application of humic acid and phosphorous via irrigation water and coting of phosphorous fertilizer via solid humic acid before soil application. Then 10 canola seeds were planted in each pot at 2-cm depth which were declined to 4 plants in each pot after emerging and greening phases. At the end of the growth period (158 days), the plants were harvested. Determination of phosphorus concentrations of plant extracts by molybdenum vanadate or yellow method and chlorophyll content (a, b and ab) and carotenoids were measured precisely before harvesting using Barnes method. After harvesting the plants, the soil was immediately air-dried and passed through a 2mm sieve. Then, the amount of phosphorus was determined by sodium-DTPA and sodium bicarbonate. The statistical results of the data were analyzed using SAS software and LSD test (at 5% level) was used for comparing the mean values.
Results and Discussion: The interactions of humic acid and phosphorus and its application methods were significant for all measured traits at the 5% level. The results of the triple effects of humic acid levels and its application at the presence of phosphorus treatments showed that the highest chlorophyll (a, b and ab) and carotenoid content was obtained at 100 mg/kg phosphorus and 1 g/kg humic acid along with irrigation water. The highest concentration of plant shoot phosphorus with an average of 0.30% was observed in 1 g/kg humic acid with irrigation water at the level of 100 mg/kg phosphorus, although had no significant difference with 0.5 g/kg of humic acid with irrigation water. Maximum amount of P was extracted by Olsen method with the mean of 16.14 mg/kg and Soltanpour and Schwab method with the mean of 5.24 mg/kg obtained in 100 mg/kg phosphorus and 1 g/kg soil humic acid application. There was a significant correlation between the phosphorus extracted by Olsen method and Soltanpour and Schwab method (r = 0.95), which was significantly correlated with concentration of phosphorus (r = 0.84) and (r = 0.85) (P<0.05). There was also a significant correlation between fresh and dry above-ground biomass, types of chlorophyll (a, b and ab) and carotenoids with phosphorus extracted by Olsen and Soltanpour and Schwab methods at 5% significance level.
Conclusion: P adsorption capacity is a function of many factors. Application of phosphorous fertilizers in calcareous soils, due to the presence of calcium with high activity, results in the formation of calcium phosphates, which becomes insoluble, over time. Humic material in interaction with phosphorus in the soil can reduce phosphorus stabilization and increase plant available phosphorus. The results of this study showed that the use of phosphorus with humic acid, rather than the use of phosphorus alone, could increase the available phosphorus in the soil and also the phosphorus concentration within the plant.
