Soil science
Kh. Salarinik; M. Nael; M. Sayyari; S.S. Moosavi
Abstract
IntroductionApplication of agricultural waste composts, in addition to improving soil fertility, has positive effects on the quality of agricultural products and the environment by reducing the use of chemical fertilizers and recycling agricultural waste. Spinach (Spinacea oleracea L.) is a suitable ...
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IntroductionApplication of agricultural waste composts, in addition to improving soil fertility, has positive effects on the quality of agricultural products and the environment by reducing the use of chemical fertilizers and recycling agricultural waste. Spinach (Spinacea oleracea L.) is a suitable plant for studying the effects of composts and chemical fertilizers due to some physiological characteristics such as high antioxidant activity and oxalic acid, significant amount of mineral compounds and vitamin C, and nitrate accumulation. Despite relatively extensive studies on the effect of different composts on plants, no study has been conducted so far to investigate the effect of grape pomace (GP) composts on plants in Iran. Therefore, the objectives of the present study were: 1- to investigate the effect of different GP composts on yield, nutrient elements, and some physiological parameters of spinach in comparison with two levels of urea fertilization in a pot experiment in two consecutive growing seasons, and 2- to investigate the relationship between nutrient elements and physiological indicators of spinach based on principal component analysis. Materials and MethodsTo investigate the effects of GP composts on yield, nutrient elements, and physiological parameters of spinach (Persius hybrid), an outdoor pot experiment was conducted in a randomized complete block design with eight compost treatments, two levels of urea fertilizer (46%), and a control treatment (C0) in three replications and two consecutive growing seasons (spring and fall). Compost treatments included: High grape pomace (HG) (60-63%) with chickpea straw and alfalfa (HG-Ch-A), high GP with chickpea straw and sugar beet pulp (HG-Ch-B), high GP with alfalfa and sugar beet pulp (HG-A-B), high GP combined with chickpea straw, alfalfa, and sugar beet pulp (HG-All); four other compost treatments included low level of grape pomace (LG) (37-42%) combined with other residues/wastes similar to the first four treatments (LG-Ch-A, LG-Ch-B, LG-A-B, and LG-All). Urea fertilizer treatments included: 150 kg per hectare (C150) (two-stage top dressing) and 500 kg per hectare (C500) (three-stage top dressing). Prior to planting, the composts were separately mixed into the soil (sandy loam) at a rate of 2% by weight(. The first crop was grown for 50 days in May 2018 and the second crop was grown for 45 days in September 2018. In both seasons, plant samples were taken in the early morning at the end of the growing season to determine the fresh and oven-dried weight of shoot and root samples, leaf area, nutrient elements, and some physiological indicators. Some of the shoot samples were wrapped in aluminum foil and stored in a freezer (-20 °C) to determine the amount of chlorophyll (type a, type b, and total), carotenoids, total phenol, vitamin C, and antioxidant activity. Oxalic acid, zinc, iron, copper, sodium, potassium, phosphorus, calcium, magnesium, and nitrate were determined in oven-dried samples. One-way ANOVA was applied separately to spring and fall data, and mean comparisons were made using Duncan's test at the 0.05% level. Principal component analysis was used to determine the relationships between nutrient elements and physiological indicators of spinach. Results and DiscussionThe LG-Ch-A and C500 treatments (in spring cultivation), and the LG-A-B, LG-All, and HG-All treatments (in fall cultivation) had the highest leaf number, leaf area, and yield and were significantly difference from the C0 treatment. The high yield in C500, LG-Ch-A, LG-All, and HG-All treatments was associated with nitrate accumulation in spinach. In both cultivations, there was a significant positive correlation between the amount of P, K, Mg and Zn in spinach and the amount of these elements in the corresponding composts. A synergistic relationship was also observed between P and Mg; P and Zn; and Mg and Zn in spinach. On the other hand, an antagonistic relationship was observed between Ca and Mg in spinach because a high concentration of calcium inhibits magnesium uptake by reducing cell permeability. In both seasons, the chemical fertilizer treatments showed the highest amount of chlorophyll and carotenoids because these compounds increase with increasing nitrogen availability. On the contrary, the amount of antioxidant activity was significantly higher in compost treatments than in chemical treatments. In the spring cultivation, the highest and lowest amount of oxalic acid and oxalic acid/Ca ratio were observed in the LG-Ch-B and HG-All treatments, respectively. Interactions between nutrients and physiological indicators were observed. The uptake of all micronutrients, P, and Mg (in both cultivations) and K (in the fall cultivation) was inhibited by high Ca concentration. With the decrease of micronutrients uptake, an increase in nitrate accumulation may occur because micronutrients are present in the structure of nitrate reducing enzymes. The interdependence between Mg and oxalic acid/Ca (in spring), K and oxalic acid (in fall), and Na and oxalic acid/Ca (in fall) may be related to the role of oxalates in the uptake of mineral ions by plants, since oxalates are usually combined with Na, Mg, Ca, and K in the form of soluble and insoluble salts. ConclusionThe use of urea chemical fertilizer (at two levels) and agricultural waste composts had different effects on the physiological indicators, growth and nutrients in spinach. Spinach grown in soils treated with composts rich in P, K, Mg, and Zn had higher nutritional value. The grouping of treatments by principal component analysis showed that chemical and control treatments were clearly separated from compost treatments with high amount of chlorophyll, carotenoid, nitrate, K, and Zn and low amount of oxalic acid, oxalic acid/Ca ratio, antioxidant activity, phenol, and Na. In general, the use of C500, LG-Ch-A, LG-All and HG-All treatments is not recommended due to nitrate accumulation in spinach.
Soil science
Kh. Salarinik; M. Nael
Abstract
IntroductionLarge amounts of agricultural waste such as straw, leaves and pulps, with high nutritional value are produced every year. Grape pomace (GP) is rich in macro- and micro-nutrients and can be used as a soil amendment. However, due to its slow decomposition rate and the spread of diseases and ...
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IntroductionLarge amounts of agricultural waste such as straw, leaves and pulps, with high nutritional value are produced every year. Grape pomace (GP) is rich in macro- and micro-nutrients and can be used as a soil amendment. However, due to its slow decomposition rate and the spread of diseases and pests, it should not be applied directly to the soil. Therefore, GP is composted in combination with other wastes. There is not enough information about the composting of GP and the effect of the produced composts on soil fertility in Iran. Hence, the aims of this study were twofold: to explore the impact of various GP composts on both soil fertility and spinach yield, relative to two levels of urea fertilizer, through a pot experiment conducted over two consecutive cultivation seasons; to categorize soil treatments based on fertilization regimes and timing (season), thus elucidating any patterns or trends in the observed effects. Materials and MethodsTo investigate the effects of GP composts on soil fertility and spinach (Persius hybrid) yield, was conducted as a randomized complete block design with eight compost treatments, two levels of urea fertilizer (46%), and a control treatment (C0), in three replications and two continuous cropping seasons (spring and fall). Compost treatments included: high grape pomace (HG) (60-63%) with chickpea straw and alfalfa (HG-Ch-A), high GP with chickpea straw and sugar beet pulp (HG-Ch-B), high GP with alfalfa and sugar beet pulp (HG-A-B), high GP combined with chickpea straw, alfalfa, and sugar beet pulp (HG-All); four other compost treatments included low level of grape pomace (LG) (37-42%) combined with other residues/wastes similar to the first four treatments (LG-Ch-A, LG-Ch-B, LG-A-B, and LG-All). Urea treatments included: 150 kg per hectare (C150) (two-step top dressing) and 500 kg per hectare (C500) (three-step top dressing). A sandy loam soil was used for this experiment. The composts were separately mixed into the soil at a rate of 2% (by weight(. The first crop was grown for 50 days in May 2018 and the second crop was grown for 45 days in September 2018. In both seasons, the fresh and oven-dried weigh of spinach shoot and root were determined. Also, total concentration of K, Na, Ca, Mg, P, Fe, Zn, Cu, and NO3- were measured in spinach to determine the amount of soil elements taken up by the crop. In both seasons, soil pH and EC, and contents of soil organic carbon (OC), active carbon (AC), total nitrogen (TN), NO3-, NH4+, and exchangeable K, Ca, Mg, and Na, as well as available forms of P, Fe, Cu, and Zn were determined. One-way ANOVAs were applied separately to spring and fall data, and mean comparisons were made using Duncan's test at 0.05% level. To determine the similarities and dissimilarities of the different treatments based on their effect on soil characteristics, cluster analysis was performed on all soil characteristics that showed significant differences between treatments. Results and DiscussionIn both cultivation periods, TN levels exhibited no significant variance across treatments. Notably, the highest potassium (K) levels were consistently observed in the HG-All and LG-All treatments, while the lowest K levels were consistently recorded in the C0, C150, and C500 treatments. In the initial cultivation period, no notable differences were observed between the C0, C150, and C500 treatments, except for potassium (K) and ammonium (NH4+), with significantly higher levels detected in the C0 treatment. Conversely, during the second cultivation period, significant disparities were observed among the C0, C150, and C500 treatments solely in terms of nitrate (NO3-) content, with notably higher nitrate levels detected in the C150 and C500 treatments. Through cluster analysis, all treatments from both cultivation periods were categorized into five distinct groups. Specifically, the C0, C150, and C500 treatments for each season were consistently grouped together, respectively, into groups one and two. All compost treatments of each season, except the HG-All treatment in the spring cultivation, were grouped into one class. In the second cultivation, the HG-Ch-A showed significantly higher EC than all treatments, except the HG-Ch-B. The LG-A-B treatment showed the highest amount of OC and C/N (in both cultivations), and NH4+ and Cu (in the second cultivation). The HG-Ch-A and HG-Ch-B treatments increased TN, P, K, Mg, OC, and AC in the second cultivation compared to the first. The amounts of all macronutrients and micronutrients, except Fe and Ca, increased in the compost treatments compared to the control and chemical treatments. In addition, an increase in EC was observed in the compost treatments compared to the control and chemical treatments, and an increase in pH compared to the C500 treatment. In the first cultivation, the LG-Ch-A and C500 treatments had significantly higher yields than the control. In the second cultivation, the LG-All, HG-All, HG-Ch-A, and LG-A-B treatments were the best compost treatments, while the LG-Ch-B and HG-Ch-B treatments were the weakest treatments in terms of soil fertility and plant yield. In both seasons, the absorption of elements by spinach depended on multiple factors, including the element type, its available content in the soil, its initial content in the composts (or fertilizer), soil pH, and yield. ConclusionThe application of GP composts over two consecutive growing seasons increased the levels of nitrogen, phosphorus, potassium, magnesium, zinc, copper, active carbon and organic carbon in the soils. These results are very important as magnesium, copper and zinc are rarely applied by farmers. In contrast, depletion of all elements, except organic carbon, occurred in the control and chemical fertilizer treatments due to plant uptake of elements. The combination of chickpea straw with sugar beet pulp is not recommended for the production of GP compost, especially at low GP levels, due to its minimal effect on soil fertility and plant yield. Despite the positive effect of the GP composts in increasing soil fertility, the continuous application of large amounts of these composts is not recommended in the arid regions due to the increase in soil EC and pH. The difference between the compost treatments after two applications of GP composts was less than after one application; these results were confirmed by cluster analysis, in the sense that all compost treatments in the second season were placed in one cluster.
Soil science
Tahmeineh Gheitasi Ranjbar; M. Nael
Abstract
IntroductionConventional cropping systems, dependent on heavy application of chemical fertilizers, are not ecologically and environmentally sustainable; they are a threat for soil and water quality and, in consequence, for plant and human health. Nitrogen fertilizers are heavily applied in conventional ...
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IntroductionConventional cropping systems, dependent on heavy application of chemical fertilizers, are not ecologically and environmentally sustainable; they are a threat for soil and water quality and, in consequence, for plant and human health. Nitrogen fertilizers are heavily applied in conventional leaf vegetable production systems to obtain maximum growth and yield. However, the excess nitrogen tends to accumulate in leaf vegetables in the form of nitrate, which pose serious human health hazards. Therefore, to supply nitrogen from non-chemical sources, such as organic amendments, is a sustainable practice for production of leaf vegetables. Spent mushroom substrate (SMS), which is the remaining material after the harvest of mushroom, is produced in large quantities (5 kg SMS for 1 kg of mushroom) and is enriched with organic carbon, N, P, K, and micronutrients. Therefore its reuse as a soil amendment not only provides essential elements for plants but also improves soil quality. Similarly, incorporation of green manures, especially legume green manures, into cropping systems is a sustainable practice for soil fertility and soil quality management. In this study, we aimed to investigate the short-term effects of two soil organic amendments (spent mushroom substrate and alfalfa residues) and their combination, in comparison to inorganic N fertilizer (urea), on soil fertility, and selected essential nutrients, and nitrate accumulation in a leaf vegetable, test plant (spinach). Materials and MethodA one-season pot experiment was led in a randomized complete block design with three replications in experimental greenhouse of Bu-Ali Sina University. Treatments were comprised of two levels of spent mushroom substrate (SMS-1: 2% SMS, and SMS-2: 5% SMS), two levels of alfalfa green manure (AGM-1: 1% AGM, and AGM-2: 3% AGM); two levels of the mixture of SMS and AGM (SMS+AGM-1: 1% SMS plus 0.5% AGM; and SMS+AGM-2: 2.5% SMS plus 1.5% AGM); two levels of urea fertilizer (U-1; 120 kg/ha, and U-2: 360 kg/ ha); and control. Selected properties of the initial soil and both organic amendments were determined. Spinach (Spinacea oleracea L.) was seeded as leaf vegetable, test plant in early autumn 2017. After ten weeks, spinach were harvested and the aboveground and root dry weights were determined. Moreover, the content of NO3-, P, Fe, Cu, Zn, and Mn in edible parts were measured. Soil samples were analyzed for EC, pH, total organic carbon, available P and K, and alkaline phosphatase activity.Results and DiscussionAll soil quality indicators were significantly affected by the treatments. TOC was significantly increased in all of the organic treatments compared to the chemical and control treatments. The maximum increase in TOC was observed in SMS-2, SMS+AGM-2, and AGM-2 treatments, compared to the control (134, 130 and 107%, respectively). A decreasing trend in TOC was detected in the high level of urea treatment (U-2) compared to the control which can be explained by the faster decomposition of soil organic matter in the presence of higher inorganic N inputs. Both organic amendments (in both levels) and the higher level of urea (U-2) decreased soil pH compared to the control. The initial low pH of SMS (5.6) and AGM (6.2), in the first case, and oxidation of urea to nitrate, in the latter, may justify this observation. In contrast, soil EC increased under the both organic amendments relative to the control and U-1 treatments. Moreover, the adverse effect of SMS on soil salinity was greater than AGM due to the initial differences in their corresponding source materials (5.8 vs. 3.0 ds/m). Available K was significantly increased in the second level of all organic treatments compared to the chemical and control treatments. As for available P, all organic treatments, except AGM-1, led to the significantly higher P than the chemical and control treatments. It is reported that organic materials compete with mineral particles for P adsorption and increase its availability. Moreover, all organic treatments, except SMS-1, significantly increased phosphatase activity compared to the chemical and control treatments. This could contribute to the mineralization of organic materials and increase available P. Spinach yield was affected by the experimental treatments. The highest increase in shoot dry weight occurred in SMS+AGM-2 and AGM-2 treatments by 235 and 230%, respectively, compared to the control. Moreover, the second level of all organic treatments as well as the first level of SMS plus AGM treatment significantly increased yield compared to the chemical treatments. Spinach P content was significantly higher in all organic treatments, except SMS-1 and AGM-1, compared to the chemical and control treatments. Organic amendments, by decreasing the surface adsorption of P and increasing soil microbial biomass, promote the availability of P for plants. Spinach nitrate content ranged from 265 (in control) to 7807 mg/kg (in U-2). According to the critical limit of nitrate in spinach (4000 mg/kg) presented by European Union, only U-2 treatment led to over-accumulation of NO3-. The two levels of AGM treatments and SMS+AGM-2 resulted in the comparable amounts of nitrate as the recommended amount of urea (U-1). A narrow variation in spinach Cu content (from 6.1 in SMS+AGM-2 to 9.8 mg/kg in AGM-2), all within the standard range reported for plants (5-20 mg/kg), was observed among the treatments. Spinach Fe content was increased under all organic treatments relative to the control, although some disparities were not significant. The lowest Fe was detected in U-2. It is reported that excessive N may diminish root growth and, in turn, reduce nutrient uptake. Spinach Zn content varied from 44.8 (in control) to 71.5 mg/kg (in SMS-2), which was close to the higher limit of standard range (20-50 mg/kg) reported for vegetables, but lower than toxic concentration range (200-400 mg/kg). Spinach Mn content varied from 17.4 (in control) to 32.1 mg/kg (in SMS-2), which was close to the lower limit of the standard range (40-400 mg/kg) reported for plants.ConclusionThe most appropriate treatments in view of improving yield and soil quality (i.e., optimum TOC, P, and K; and lower EC) as well as tolerable nitrate accumulation were SMA+AGM-1 and SMS-1 in decreasing order. These treatments are preferred over the chemical treatments (U-1 and U-2).
Soil science
M. Nael; S.S. Salehi; J. Hamzei; M. Zandi Baghche-Maryam
Abstract
IntroductionConservation agriculture (CA), as a sustainable cultivation system, aims at efficient use of natural resources with least environmental impacts, while achieving food security through increasing yield and crop diversification. CA consists of three main principles: 1- reduction or elimination ...
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IntroductionConservation agriculture (CA), as a sustainable cultivation system, aims at efficient use of natural resources with least environmental impacts, while achieving food security through increasing yield and crop diversification. CA consists of three main principles: 1- reduction or elimination of mechanical soil disturbance; 2- maintaining a permanent cover of crop residues on soil; and 3- diversification of crops. However, the total area under CA in Iran is less than 5% of arable lands. In Hamedan province, CA is mostly implemented in rainfed farming. Therefore, there is a necessity to expand CA in irrigated areas. Nonetheless, a lack of sufficient technical and local knowledge about CA acts as a barrier for its expansion in irrigated lands. Despite the large body of research conducted on CA, there is no detailed information about the combined effects of cover crops and conservation tillage systems on soil functioning and corn productivity in semi-arid regions of Hamedan province. Therefore, our aim was to study three-year effects of conservation tillage practices (no tillage and minimum tillage) and cover crops (hairy vetch and grass pea) on selected soil quality indicators and yield components of corn in a clay loam soil of a semi-arid region in Hamedan. Materials and Methods Combined effects of various tillage practices and cover crops on selected soil quality indicators and corn productivity were examined in a three-year experiment conducted in the research field of Bu-Ali Sina University. A factorial experiment in the basis of randomized complete block design with 3 replications and 2 factors were carried out, in which three levels of tillage practices (no tillage (NT), minimum tillage (MT), and conventional tillage (CT)), and three levels of cover crops (hairy vetch (V), grass pea (L), and no cover crop) were the treatments. Surface soil samples (0-15 cm) were collected two weeks after corn harvesting in the third year of experiment. Total organic carbon (TOC), organic carbon stock (CS), active carbon (AC), carbon management index (CMI), basal respiration (BR), alkaline phosphatase activity (APA), bulk density (BD), mean weight diameter of water-stable aggregates (MWD), and available phosphorous (P) and potassium (K) were determined. Corn yield components (including number of kernel rows per corn, number of grains per corn row, ear cob weight, hundred weight of grains, ear weight, grain weights per ear, biological yield and grain yield) were measured.Results and DiscussionThe highest TOC (0.96%), CS (18.7 ton/ha), AC (398 mg/kg), CMI (74.8), BR (0.118 mgCO2/g.d) and MWD (1.82 mm) were observed in MT treatment. However, no significant difference was detected between MT and CT in terms of AC, CS and CMI. Moreover, the lowest TOC (0.74%) was measured in NT, which showed no significant difference with CT treatment (0.83%). Reduced destruction of soil structure coupled with the increased MWD, and increased inputs of crop residues through MT, resulted to the protection of organic matter against microbial decomposition. Soil structuring, represented by BD, was improved under conservation tillage treatments (NT and MT).Among cover crops, hairy vetch treatment demonstrated the highest TOC (1.0%), CS (19.5 ton/ha), AC (427 mg/kg), CMI (80.3) and MWD (1.73 mm). However, these indicators, except CMI, were not significantly different between the two cover crops. On the contrary, these indicators were lowest in the control (no cover crop). Moreover, AC and CMI were not significantly different between grass pea and the control. Carbon stock was increased by 54 and 40% in hairy vetch and grass pea treatments, respectively, relative to the control. In general, cover crop cultivation combined with conservation tillage practices introduced additional biomass to the soil which in turn improved soil organic matter over time and enhanced soil quality.The lowest amounts of biological yield (1663 g/m2), grain yield (507 g/m2), hundred weight of grains 11.0 g), ear weight (91.4 g), grain weights per ear (62.9 g), and number of kernel rows per corn (13) were measured in CT system. In contrast, the highest grain yield (637 g/m2), hundred grain weight (13.6 g), ear weight (108.4 g), and grain weights per ear (81.9 g) were measured in NT treatment. However, the biological yield showed no significant difference between NT and CT. Soil quality improvement in conservation tillage treatments explains the enhancement of certain yield components. Biological yield and number of grains per row demonstrated significant difference between cover crop treatments; the maximum of biological yield (2103 g/m2) and of number of grains per row (44) was measured in hairy vetch treatment. Moreover, the lowest of biologigal yield (1589 g/m2) was observed in the control (no cover crop) treatment. Conclusions All soil quality indicators, except available P, were improved under MT as compared with CT. Our three-year study revealed that among conservation tillage treatments, MT improved majority of soil quality indicators compared to NT. Therefore, minimum tillage practice seems to be more sustainable in this study area. Conservation tillage treatments (MT and NT) also enhanced corn grain yield, grain weights per ear and number of grain rows per ear compared to to the CT. Both cover crops improved most soil quality indicators. Moreover, both cover crops induced significant effect on biological yield, although hairy vetch was more effective than grass pea. As a whole, the integration of minimum tillage with hairy vetch cover crop is considered as a sustainable cropping system for the improvement of soil quality and corn yield in this area.
Esmaeil Esfandiary Ekhlas; Mohsen Nael; Mohsen Nael; Javad Hamzei; Ali Akbar Safari Sinegani
Abstract
Introduction: Soil is a finite natural resource and non-renewable under agricultural production without implementation of sustainable management practices. Ecological sustainability of agroecosystems can be comparatively assessed by soil quality evaluation, which in turn is assessed by soil quality indices. ...
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Introduction: Soil is a finite natural resource and non-renewable under agricultural production without implementation of sustainable management practices. Ecological sustainability of agroecosystems can be comparatively assessed by soil quality evaluation, which in turn is assessed by soil quality indices. Soil quality is the general term used to refer to “the continued capacity of soil to function as a vital living system, within ecosystem and land-use boundaries, to sustain biological productivity, maintain the quality of air and water environments, and promote plant, animal, and human health”. Conservation tillage and use of cover crops are some of the sustainable agriculture practices that can improve the soil quality by adding organic matter and nutrients, and by acting as scavengers to trap leftover nutrients that otherwise might leach out. Cover crops are used as ground cover, mulches, green manure, nurse crops, smother crops, and forage and food for animals or humans. Given the significant role of tillage practices and crop residue management in soil quality improvement and crop production, a four-year field experiment was conducted to determine selected soil quality indices and Cucurbitapepo yield under different tillage and legume cover crop managements in Hamadan.
Materials and Methods: A four-year field experiment (2011-2014) was carried out at Bu-Ali Sina University experimental field in Dastjerd, Hamadan, as a factorial experiment in randomized complete block design with three replications. The area is located at 37 km of Hamadan, on 35◦ 01' N latitude and 48◦ 31' E langitude with 330 mm annual rainfall and 1690 m altitude. The treatments consisted of three levels of tillage practices (NT: no-till (direct seeding), MT: minimum tillage (chisel plowing + disk) and CT: conventional tillage (moldboard plowing + disk)) and two levels of cover cropping (C1: with legume cover crop (lathyrus sativus) and C0: without cover crop). These treatments were applied for four consecutive years in a way that lathyrus sativus as cover crop were planted in late winter for each year and returned to the soil surface with a trowel when 30% of the field was flowered. One week later, and prior to the cultivation of main crop, the mentioned tillage treatments were implemented. In the fourth year of the project,Cucurbita pepo was planted as the main crop. Soil and plant (Cucurbita pepo) were sampled early autumn (2014) and were analyzed for soil organic carbon, soil active carbon, macro and micro-aggregate carbon, mean weighted diameter of water stable aggregates, soil bulk density, basal microbial respiration and grain yield. Obtained data were analyzed using statistical software SAS 9.4 and the means were compared using LSD multiple range test at 5 percent level.
Results and Discussion: The results revealed that total organic carbon, active carbon, aggregate carbon, mean weighted diameter of water stable aggregates, bulk density, porosity and basal respiration were significantly affected by cover crop and tillage system so that the highest amount of these indicators were obtained in no-tillage system with cover crop treatment (NT-C1) and the lowest amounts were observed in the conventional tillage without cover crop (CT-C0). For instance, mean soil organic carbon increased from 0.4 percent in CT-C0 to about 0.7 percent in NT-C1. For majority of soil quality indices, no significant difference was observed between minimum and no-till; moreover, the application of cover crop in conventional tillage improved some aspects of soil quality. For instance, MWD was the highest (2.14 mm) in NT-C1, and was not significantly different with that of MT-C1 treatment. On the contrary, this index was significantly the lowest (0.48 mm) in CT-C0. The C. pepo grain yield was also significantly affected by tillage system, cover crop and their interactions. The highest grain yield (142.1 g.m-2) was obtained in MT-C1 treatment, which did not show significant difference with NT-C1 treatment. The lowest C. pepo grain yield (115.3 g.m-2) was observed in conventional tillage without cover crop (CT-C0) treatment, but it was in a same statistical group with NT-C0, MT-C0 and CT-C1 treatments. Cover crop increased organic carbon, active carbon, porosity, bulk density, microbial biomass activity and MWD by enhancing soil organic matter, probably; conservation tillage on its part further improved these effects by preventing the rapid decomposition of organic matter by reduced soil destruction, which eventually increased soil organic carbon, active carbon and production of stable aggregates.
Conclusions: Generally, after four years of applying different tillage practices and cover cropping, it was demonstrated that the integrated management of the conservation tillage (either no-tillage or minimum tillage) with legume cover cropping was the most appropriate management in the semi-arid region of Hamadan in view of selected soil quality indices and crop yield improvements.
Khadije Salarinik; Mohsen Nael; Ghasem Asadian; Ali Akbar Safari Sinegani
Abstract
Introduction: Soil organic matter is influenced strongly by vegetation cover and management, therefore it is proposed as the main indicator of soil quality and health. The changes in soil organic matter status occur much more rapidly in the labile pools than in organic C. Thus, labile pools can be used ...
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Introduction: Soil organic matter is influenced strongly by vegetation cover and management, therefore it is proposed as the main indicator of soil quality and health. The changes in soil organic matter status occur much more rapidly in the labile pools than in organic C. Thus, labile pools can be used as early indicators of changes in total organic matter that will become more obvious in the longer term here. In addition, the labile fraction has a disproportionately large effect on nutrient-supplying capacity and structural stability of soils. Land management as well as soil and environmental conditions lead to the deployment of different plant communities in rangeland ecosystems, which in turn may have different effects on soil quality indicators. The main objective of this research was to investigate the influence of different vegetation covers on the quantity and quality of soil organic carbon fractions in Gonbad experimental watershed, Hamadan. Moreover, the seasonal changes of selected soil carbon fractions were investigated.
Materials and Methods: Paired Gonbad watershed in Hamedan consists of two sub-basins: in control sub-basin no grazing management is applied, while in protected sub-basin, grazing has been restricted to a very short period in late autumn since 2002. Average annual precipitation and average annual temperature in the area are 304.4 mm and 9.5 °C, respectively (5). The soil cover of the watershed consists of TypicCalcixerepts, TypicHaploxerepts and Lithic Xerorthents (9). Five different vegetation typesof which, grasses (G), Astragalus-Bromus (A-B), Astragalus-Artemisia (A-A), Astragalus-Lactuca (A-L) in protected sub-basin, and Astragalus-Euphorbia (A-E) in control sub-basin, were selected. In addition, a formerly cultivated hilly land outside the watershed, now under rainfed wheat farming (RW) was selected as a non-pasture vegetation type. All of the six vegetation types were similar in terms of soil parent materials and slope aspect.. Soil and plant sampling were conducted in mid-autumn 2012 (a), and late spring 2013 (s). Three plots (1*1 m2) were studied in each vegetation type. Total organic carbon (TOC), carbon stock (CS), carbon stock normalized with sand(CS/Sa), active carbon (AC), normalized active carbon (AC/TOC), soil carbohydrates (Ch), normalized carbohydrates (Ch/TOC), basal respiration (BR) and normalized basal respiration (BR/TOC) were measured in surface soils (0-15 cm). A factorial experimental design with two factors, vegetation type (6 levels) and time (2 levels), was conducted. Prior to statistical analysis, data were normalized, if required.
Results and Discussion: TOC and CS contentswere significantly different between vegetation types. A-B and A-A had highest canopy cover, litter cover and species diversity. Species diversity in the rangeland ecosystems has direct effect on fodder production and soil organic carbon content. A-E site, despite its low TOC content, hadhigher CS/Sa (51.9 Mg/ha) due to higher amount of clay content, compared to A-A (43.1Mg/ha) with higher TOC content. The amount of AC andAC/TOC in different vegetation types is proportional to the amount of TOC, CS, total canopy, and the canopy and production of herbaceous species. AC content was significantly highest in A-B (711.7 mg/kg), and lowest in RW site(262.6 mg/kg). A-B site is rich in grass species with high amounts of readily decomposable root residues and exudates. The variation of carbohydrate contents in different vegetation types wasvery similar to that of total organic carbon, in that A-B and A-A exhibited the highest (5843 and 5258 mg/kg, respectively) and RW showed the lowest (1937 mg/kg) carbohydrate contents. The woody, not easily decomposible litters in A-A explainedthe high content of Ch/TOC (38.12%) in this site; low rate of humification entails increased soil carbohydrates. Ch/TOC was significantly lower in A-E than other covers. The highest BR andBR/TOC, were observed in A-B and A-A sites, mainly due to the high canopy cover, species richness,and soil organic matter. The lowest BR andBR/TOC were observed in A-E.Thesoil texture in this site was clay.The recirculation of organic matter in fine-textured soils is low because of organic materials protection from microbial decomposition. Total organic matter and labile organic carbon inputs werelower in A-L, A-E and G sites; this may explain the reduction of microbial activity in these vegetation types. Except for AC/TOC, Ch, and BR, seasonal changes of all other indicators were significant. Unlike other indicators, the content of Ch/TOC was significantly higher in autumn than spring.
Conclusion: Vegetation types had significant effects on selected soil quality indicators, so that A-A and A-B sites exhibited the highest soil quality, mainly because of higher vegetation cover, litter, and plant diversity. RW, followed by A-E site, demonstrated the lowest soil quality due to the tillage practices and low plant residue inputs in the first case, and overgrazing of vegetation cover and litter in the second. Total soil organic carbon and active carbon were significantly higher in spring compared to autumn. Seasonal changes of basal microbial respiration and carbohydrates were not statistically significant.
Sh. Nosratipoor; M. Nael; Mohsen Sheklabadi; A.A. Sepahi Garo
Abstract
To determine the origin of heavy metals, the effects of parent materials, soil genesis, and human activities on the content and distribution of selected metals in soils near Mofateh Martyr powerhouse, Hamedan, were assessed. Six types of parent materials including shale, schist, limestone, alluvial ...
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To determine the origin of heavy metals, the effects of parent materials, soil genesis, and human activities on the content and distribution of selected metals in soils near Mofateh Martyr powerhouse, Hamedan, were assessed. Six types of parent materials including shale, schist, limestone, alluvial plain, alluvial terraces and fan deposits were identified and soil genesis were studied. Total content of Cd, Cu, Mn, Ni, Zn, Pb, Fe were determined in soil horizons and parent materials. Concentration of the metals in four different chemical phases, including acetic acid extractable, reducible, oxidizable and residual fractions, was determined with four-step sequential extraction procedure. Soil development is limited in the studied region so that the discrepancy between solum and parent material in terms of heavy metal content is not great in general. Calcareous soils and limestone have the lowest amount of copper, manganese, nickel, zinc, lead and iron. Independent of soil types and parent materials, most of the heavy metals, except Mn, were present in the residual fraction. The concentration of Mn in all profiles is highest in reducible fraction. Low degree of soil development and the prevalent presence of metals in residual fraction show the influential role of parent materials in controlling metal concentration and distribution; pedogenic processes have minor effects. The role of human activities is limited for most of the selected metals; however, the tangible presence of Pb and, in some cases, Cd in acetic acid extractable fraction, reflects the impact of human activities on the concentrations of these two metals.