خدیجه سالاری نیک

Application 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.

To 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.

The 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.

The 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.

Large 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. 

To 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. 

In 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. 

The 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.

The combined effects of biochemical composition and amount of plant residues returned to soils affect stability of aggregation and the rate of aggregate turnover. To investigate the influence of vegetation type on aggregate size distribution, five vegetation types including rainfed wheat (RW), grasses (G), Astragallus–Bromus (A-B), Astragallus–Lactuca (A-L) and Astragallus–Artemisia (A-A) were studied under similar environmental conditions in terms of parent material and slope aspect in Gonbad watershed, Hamadan. Total organic carbon (TOC), soil carbohydrates (Ch), mean weighted diameter (MWD), size distribution of water-stable aggregates (AS) and aggregate carbon (AC) were measured in surface (0-15 cm) soils. The amounts of TOC, Ch, MWD and AC (present in all aggregate size fractions) were significantly greater in soils under A-B and A-A than the soils of other vegetation covers, while the lowest values were observed in soils under RW and G. The highest AS>2 mm and lowest AS 2 mm were lower in soils under A-L, G and RW compared to other aggregate sizes. A-B and A-A vegetation types had greater canopy, annual production, plant diversity and litter content compared to other vegetation types.Frequent soil ploughing in RW site andlow plant diversity and canopy cover in A-L and G sites contributed to reduced soil aggregation and lower content of coarse aggregates;AS in 0.5-0.053 (mm) fraction in soils of aforementioned vegetation types was greater than other aggregate sizes. It was concluded that Ch and 0.5-0.053 (mm) aggregate size fraction might be reliable soil quality indicators that reflected land use and vegetation type changes.

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.
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.
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.
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.

The knowledge of rangeland vegetation types and factors influencing on their establishment and stability is essential for sustainable management and regeneration of rangeland areas. With this aim, Gonbad watershed, due to different vegetation types, environmental conditions and grazing managements was studied. The watershed was stratified to homogenous units based on morphology of vegetation types and environmental factors. Land properties, total canopy and canopy of the main five vegetation forms (annual grasses, perennial grasses, annual forbs, perennial forbs, and shrubs) were determined in 3 to 4 plots (1 x 1 m2) in each unit; plant and surface soil were sampled. Using TWINSPAN method, Silen sp., Centaura virgate, Astragalus verus and Cousinia bijarensis were identified as indicator species. DCA analysis subdivided the watershed into six ecological groups based on indicator plant species, production of perennial grasses and environmental factors, such as percent of sand and clay, and slope aspect. Based on the analysis of indicator species Asteragalus gossypinus (p= 0.001), Taeniatherum crinitum (p= 0.002) and Heteranthelium piliferum (p= 0.007) classified the vegetation cover into three main groups. Silen sp., Astragalus gossypinus, Centaurea virgat, Artemisa siberi, and Festuca ovina represent mountainous steppe and semi-steppe ecological environments. These deep rooting species are resistant to dry conditions. Therefore, ecological