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).
Ali Barikloo; Parisa Alamdari; kamran Moravej; Moslem Servati
Abstract
Introduction: In recent decades, the most important issue for agricultural activities is maximizing the productions. Today, wheat is grown on more lands than any other commercial crops and continues to be the most important food grain source for humans. Sustainable agriculture is a scientific activity ...
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Introduction: In recent decades, the most important issue for agricultural activities is maximizing the productions. Today, wheat is grown on more lands than any other commercial crops and continues to be the most important food grain source for humans. Sustainable agriculture is a scientific activity based on ecological principles with focus on achieving sustainable production. It requires a full understanding of the relationships between crop production with soil and land characteristics. Furthermore, one of the objectives of sustainable agriculture is enhancing the agricultural production efficiency through applying proper management, which requires a deep understanding of relationships between production rate, soil and environment characteristics. Hence, the first step in this process is finding appropriate methods which are able to determine the correct relationships between measured characteristics of soil and environment with performance rate. The aim of this study was evaluating the performance of neuro-genetic hybrid model in predicting wheat yield by using land characteristics in the west of Herris City.
Materials and Methods: The study area was located in the northwest of east Azarbaijan province, Heris region. In this study, 80 soil profiles were surveyed in irrigated wheat farms and soil samples were taken from each genetic horizon for physical and chemical analyses. In this region, soil moisture and temperature regimes are Aridic border to Xeric and Mesic, respectively. The soils were classified as Entisols and Aridisols. We used 1×1 m woody square plots in each profile to determine the amounts of yield. Because of nonlinear trend of yield, a nonlinear algorithm hybrid technique (neural-genetics) was used for modeling. At first step, the average weight of soil characteristics (from depth of 100 cm) and landscape parameters of selected profiles were measured for modeling according to the annual growing season of wheat. Then, land components and wheat yield were considered as inputs and output of model, respectively. For this reason, genetic algorithm was investigated to train neural network. Finally, estimated wheat yield was obtained using input data. Root mean square error (RMSE) and Coefficient of determination (r2), Nash-Sutcliffe Coefficient (NES) indices were used for assessing the method performance.
Results and Discussion: The sensitivity analysis of model showed that soil and land parameters such as total nitrogen, available phosphorus, slope percentage, content of gravel, soil reaction and organic matter percentage played an important role in determining wheat yield in the studied area. The soil organic matter and total nitrogen had the highest and lowest correlation with wheat yield quantity and quality, respectively, indicating the total nitrogen was the most important soil property for determination of wheat yield in our studied area. We found that network learning process based on genetic algorithms in the learning process had lower error. The findings showed that beside of confirming the desired results in the case of using sigmoid activation function in the hidden layer and linear activation function in the output layer of all neural networks, it is demonstrated that the proposed hybrid technique had much better results. These findings also confirm better prediction ability of neural network based on error back propagation algorithm or Levenberg-Marquardt training algorithm compared to other types of neural network confirms.
Conclusion: Using nonlinear techniques in modeling and forecasting wheat yield due to its nonlinear trend and influencing variables is inevitable. Recently, genetic algorithms and neural network techniques is considered as the most important tools to model nonlinear and complex processes. Despite the advantages of these techniques there are a lot of weaknesses. Imposing specific conditioned form by researchers in the techniques of genetic algorithms and stopping neural network learning at the optimal points are the main weaknesses of these techniques, while searching for global optimal point and not imposing a specific functional forms are the robustness of genetic algorithm techniques and neural networks, respectively. Results of this study indicated that the proposed hybrid technique had much better results. Correlation coefficient (0.87) and average deviation square error (473.5) were high and low, respectively. It can be concluded that the surveyed soil properties have very strong relationship with the yield. Implementation of appropriate land management practices is thus necessary for improving soil and land characteristics to maintain high yield, preventing land degradation and preserving it for future generations required for sustainable development.
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.
Solmaz Kazemalilou; Nosratollah Najafi; adel reyhanitabar
Abstract
Introduction: Sunflower as one of the most important oil crops in the world is affected by water deficit stress. Water deficit stress is one of the most important limiting factors of crops growth and production in Iran and many regions of the world. Because of the low water productivity in Iran, the ...
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Introduction: Sunflower as one of the most important oil crops in the world is affected by water deficit stress. Water deficit stress is one of the most important limiting factors of crops growth and production in Iran and many regions of the world. Because of the low water productivity in Iran, the water conservation and increasing of water use efficiency through good management including integrated application of organic and chemical fertilizers and balanced nutrition of plants are necessary. One of the negative effects of water deficit stress is impaired uptake of nutrients such as phosphorus (P) by plants and a decrease in plant yield. It has been found that use of P can reduce the negative effects of drought stress on plants that means the tolerance of plants to drought stress increases with optimal nutrition of P. In Iran, due to the lack of organic matter and the high cost of chemical fertilizers, farmers tend to use organic wastes such as sewage sludge that can have an important contribution in the improvement of soil fertility and plant nutrition and lead to an increase in water use efficiency. Also, integrated and suitable nutrition of plants is a method of sustainable management of soil fertility under environmental stresses. Therefore, this study aimed to evaluate the effects of sewage sludge (SS) and triple superphosphate (TSP) on sunflower (Helianthus annuus L. cv. Farrokh) seed yield and its components and determining the optimal levels of their consumption under optimum and limited irrigation conditions.
Materials and Methods: This experiment was conducted as a split-plot factorial arrangement in a randomized complete block design in Agricultural Research Station of Khoy under field conditions for two years. Experimental factors were irrigation time at two levels (irrigation after 60 and 150 mm evaporation from class A evaporation pan), triple superphosphate at three levels (0, 100 and 200 kg/ha), sewage sludge at four levels (0, 14.2, 28.4 and 56.7 t/ha) and year at two levels (2014 and 2015) with three replications. The 1000 seed weight of sunflower, weight and number of seeds per plant, the percentage of empty achenes, head diameter and seed yield were measured at the end of plant growth period. Statistical analysis of the data was performed using MSTATC software and means comparison was done by Duncan’s multiple range test at 5% probability level.
Results and Discussion: The combined analysis of variances showed that the effect of year was significant for weight of seeds per plant, head diameter and seed yield but it is not significant for 1000 seed weight, number of seeds per plant and percentage of empty achenes. Although water deficit stress significantly increased the percentage of empty achenes but 1000 seed weight, weight and number of seeds per plant, head diameter and seed yield significantly decreased compared to optimum irrigation conditions. The application of integrated application of 200 kg TSP and 56.7 tons SS per ha increased yield and yield components significantly compared to the control treatment. The interaction effects of TSP×SS×irrigation were significant for all studied characteristics. Under optimum irrigation condition, the highest 1000 seed weight (64 g), weight of seeds per plant (85 g), number of seeds per plant (1513), head diameter (22 cm) and seed yield (5576 kg/ha) were observed in intergrated treatment of 200 kg TSP+56.7 tons SS/ha. Under limited irrigation condition, the highest 1000 seed weight (57 g), seeds weight per plant (81 g), seeds number per plant (1494), head diameter (19.6 cm) and seed yield (5322 kg/ha) were obtained from 56.7 tons SS/ha treatment which showed no significant difference with 100 kg TSP+56.7 tons SS/ha treatment. Under optimum and limited irrigation conditions, the percentage of empty achenes were significantly decreased by integrated treatments of 200 kg TSP+56.7 tons SS/ha and 100 kg TSP+56.7 tons SS/ha (70 and 81 percent, respectively) compared to the control.
Conclusion: The results of this study indicated that integrated application of triple superphosphate and sewage sludge can mitigate negative effects of drought stress; therefore in order to reduce the use of chemical fertilizers, increasing sunflower seed yield and development of sustainable agriculture, integrated treatments of 200 kg TSP+56.7 tons SS/ha under optimum irrigation and 100 kg TSP+56.7 tons SS/ha under limited irrigation can be recommended at similar conditions (from the aspect of soil, plant, sewage sludge and climate).
