Soil science
Sahar Mehrnoosh; Ali Beheshti Ale Agha; Fatemeh Rakhsh; Morteza Pourreza; Ali Akbar Safari Sinegani
Abstract
IntroductionThe maintenance of planted forests in arid and semi-arid lands is important. Soil formation in forest ecosystems is different with different tree species. Tree species have a direct and indirect effect on soil organisms. Forest ecosystems change their species composition and abundance of ...
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IntroductionThe maintenance of planted forests in arid and semi-arid lands is important. Soil formation in forest ecosystems is different with different tree species. Tree species have a direct and indirect effect on soil organisms. Forest ecosystems change their species composition and abundance of microorganisms, and consequently their biogeochemical cycles. The accumulation of vegetation biomass and the improvement of soil fertility can play a significant role in soil restoration.Materials and MethodsIn order to investigate the biological characteristics of the soil from 5 treatments, including agricultural (dry farming and relatively poor lands that are usually cultivated barley and wheat and have low productivity), pasture (pastures with minimal vegetation and high slopes that are affected by overgrazing have been changed to barren lands), forest with Acacia type (under and outside the crown), forest with the Cupressus arizonica type (under and outside the crown) and forest with the Pinus brutia type (under and outside the crown) randomly. Sampling was done in 3 repetitions from the 0 to 5 cm layer. The statistical sampling design of this research was completely random, in which, according to the type of afforested species, two types of coniferous forest stands (including Cupressus arizonica and Pinus brutia) and one broadleaf stand (Acacia species) were selected. Also, the area under the crown trees and outside the crown trees was also investigated. Soil samples were sampled with sterile equipment and crushed through a 4-mm sieve. Fresh and moist soil was kept at 4 °C temperature for soil biological tests. Microbial biomass carbon, soil basal respiration (197 days), substrate-induced respiration, and metabolic quotient were measured. Streptomycin sulfate was used to measure fungal respiration and cycloheximide was used to measure bacterial respiration. The activities of urease, acid, and alkaline phosphatase enzymes were determined. After measuring the biological properties of the soil, the normality of the data was checked by the Anderson–Darling test, and the homogeneity of the variance of the treatments was checked by using Levene's test. Analysis of data variance was done using One-Way ANOVA and average data comparison was done using Duncan's test at 5 and 1% probability levels (SAS 9.4 and SPSS 26).Results and DiscussionThe results of soil biological characteristics analysis showed that the highest values of soil respiration and amount of consumed organic matter, substrate-induced respiration, microbial biomass carbon, enzyme activities, and fungal respiration were measured in conifers. Although the amount of these features was also significant in broadleaf trees, they had significant differences. In this study, the high soil respiration rate in coniferous covers compared to broadleaf can be due to the high organic carbon content of the soil in this cover. According to the results of substrate-induced respiration in different coatings, likely the activity of microorganisms involved in the decomposition of organic matter in the studied habitats had a significant difference; Therefore, different coatings can affect the population of soil microorganisms as the main source of decomposition and emission of carbon dioxide by changing the quantity and quality of organic matter and other factors. Also, the highest values of metabolic quotient and bacterial respiration were observed in agricultural and pasture covers. A higher metabolic quotient in these covers indicates a decrease in the efficiency of the use of leaf litter by the soil microbial community. In general, the metabolic quotient in the bacterial community is higher than the fungal community; Therefore, it seems that the predominance of the bacterial population in agricultural and pasture cover has caused this index to increase, although plowing and cultivation, and disturbance of these covers have caused stress to this bacterial community and as a result increased the metabolic quotient deficit in these covers.ConclusionThe results of this research showed that the type of planted tree species causes significant changes in the biological characteristics of the soil. The current research shows that the forest, whether coniferous or broadleaf, had the highest values of enzyme activities, basal respiration, substrate-induced respiration, microbial biomass carbon, and the lowest values of metabolic quotient compared to agricultural and pasture covers. Afforestation increases biological activity and possibly the number and diversity of microorganisms, and improves soil characteristics in the long term. In agriculture and pasture land, due to the destruction of soil and aggregates by agricultural activities such as plowing or excessive livestock grazing, the amount of organic carbon and the activity of microorganisms decreases, and with the decrease of other soil characteristics, the quality of the soil decreases over time. From this research, it can be concluded that the planting of forest species in the soils of degraded areas in the long term can increase soil organic carbon due to high-quality leaf litter, and as a result, increase permeability and soil moisture. Increasing soil organic carbon increases the activity of microorganisms, and in the long term, it will improve various soil characteristics. Planting forest plants in the natural areas of the country, which were destroyed due to the change of use to agriculture and indiscriminate cultivation and finally abandoned, can improve the characteristics of the soil and, as a result, establish the native vegetation of the region, and increase the permeability of water in the soil, the risk of soil erosion, floods, etc. reduce.
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.
