جستجوی مقالات مرتبط با کلیدواژه « معدنی شدن نیتروژن » در نشریات گروه « آب و خاک »

The activities of earthworms and mycorrhiza affect on water and nutrient uptake and crop yield. The aim of this study was to evaluate the effect of earthworm (Eisenia fetida) and arbuscular mycorrhiza fungi (AMF, Funneliformis mosseae) on root colonization, shoot dry weight, phosphorus and nitrogen uptake, organic carbon and soil microbial biomass C. In this regard, a greenhouse experiment was conducted in a completely randomized design (CRD) with three replications in Agricultural Research Station of Ferdowsi University of Mashhad. The experimental treatments consisted of control, single and integrated treatments of earthworm and mycorrhiza. The results showed that inoculated treatments with arbuscular mycorrhizal fungi significantly increased the amount of root colonization. The same trend was observed in combined treatments with mycorrhizal fungi and earthworm. The results also revealed that the integrated application of earthworm and mycorrhiza treatment increased the concentration of P and N in shoot by 105% and 79% ,respectively, compared to control treatment (p

In order to investigate the effect of soil compaction on soil nitrogen mineralization process and its uptake by wheat a factorial experiment in a completely randomized design with three replications was designed. Experiment was conducted with three levels of compaction (normal, 10% and 20% compression), two soil textures (sandy and clay) and five sampling times (1, 7, 14, 30 and 60 days after planting). Ammonium and nitrate concentrations in soil were measured at five time intervals. Results indicated that the effect of soil compaction, time interval and the interaction of soil compaction and time intervals on concentrations of ammonium and nitrate were significant (p

Soil compaction as a global problem and a multi-dimensional and complex process involving the interaction of climate, soil Mashyn- Plant- known to have a significant economic and environmental impacts and to sustainable agriculture is an intractable problem.For In order to assess compaction effect on nitrogen mineralization process in soil in form of factorial completely randomized design with three repetitions have been done in the agricultural faculty of Guilan University. The soil compaction has been studied in three levels (natural compaction, 10% and 20% compaction), sort of soil in two levels (heavy and lightweight texture) and five periodical steps (days of 1, 7, 14, 30 and 60 after implant). Ammonium and nitrate concentration in soil have been determined in five periodical steps. Significant decrease of ammonium concentration in more compacted sample is related to second and third steps (with avarge 20.75 and 13.68 ppm in 20 present compaction, respectively). The results indicate that by increasing soil compaction, the amount of soil nitrogen will decrease. In the compaction sample, less organic nitrogen change into ammonium and formation nitrate decrease because of conversion to ammonium.

Earthworms are among the most important organisms in soil and their activities can be an indicator of soil quality. These organisms may be influenced by organic wastes application such as sewage sludge and subsequently affect soil quality. One of the quick and easy methods for soil quality monitoring is the use of biological indicators such as microbial activity. It is due to their quick response to changes in the environment. The purpose of this study was to evaluate the effect of earthworms on nitrification rate and arginine ammonification as microbial activity in a calcareous soil amended with urban sewage sludge.
The studied soil was sampled from Shahrekord University land and sewage sludge belonged to the refinery sludge ponds of shahrekord. Based on dry weight, this organic waste had carbon and nitrogen, approximately 67 and 110 times more than tested soil, respectively. The organic waste in terms of quality and heavy metal concentrations was in class A. Experimental treatments were sewage sludge (without and with 1.5% sewage sludge) and earthworm (no earthworm, Eiseniafoetida from epigeic group, Allolobophracaliginosa from endogeic group and a mixture of the two species) as 2×4 full factorial experiment arranged in a completely randomized design with three replications. After applying sewage sludge, the pots were irrigated three months to achieve a balance in the soil. An adult earthworm per kg of soil was added and in the mixed treatments comparison species were 1:1. To prevent the exit of earthworms, the pots was closed with a thin lace. At the end of the experiment, soil was completely mixed. Part of it was stored in the refrigerator to measure the microbiological parameters. Chemical properties were measured by the air-dried soil. The effectiveness of a factor in the observed changes is shown by partial effect size (Tabachnick and Fidell 2012). So, partial effect size (Eta2p) for each source of variation (SS, earthworm and SS×earthworm) was calculated.
Results According to Eta2p, the role of sewage sludge application to increase total nitrogen was almost twice the earthworm and had a greater effect on the property. Because of low concentrations of heavy metals and high nutrient in sewage sludge, it increased nitrification rate and arginine ammonification by 16.7 and 62.5 percent, respectively. Considering that the indices represent microbial biomass activity, so we can say sewage sludge application increased theri activities. Sewage sludge application increased total nitrogen, because provided the substrate for heterotrophic bacteria. Consequently, ammonium production improved and stimulated activity of Nitrosomonas and Nitrobacter. There was a positive and significant correlation between total nitrogen, arginine ammonification and nitrification rate, that confirmed the occurrence of this process. Earthworm inoculation affected these two indicators (p

Mountainous landscapes in Central Zagros are mainly used as grazing rangelands to feed animals and are heavily degraded. Overgrazing may impose a negative effect on rangeland productivity and sustainability through significant changes in soil properties. Soil nitrogen (N) mineralization is one of the key biological processes that might be affected by biotic and abiotic factors including range grazing regime or intensity. The primary objective of this study was to assess the effects of rangeland management (grazing and ungrazing regimes) on soil N mineralization in natural rangelands of Chaharmahal VA Bakhtiyari province. Three range management regimes including a) long-term ungrazed, b) controlled grazed and c) freely- (over)-grazed plots in a close vicinity were selected in three regions consisting of SabzKouh (protected from grazing for 18 years), Boroujen (protected from grazing for 23 years) and Sheida (protected from grazing for 2 years), and soil samples were collected from 0-15 cm depth for some physical and chemical properties. Soil N mineralization was measured under standard laboratory conditions. At SabzKouh, the effect of range management on the cumulative N mineralization and the proportion of N mineralized (%) was significant (P<0.05) and ungrazing regime resulted in 89% and 96% increases in soil N mineralization in ungrazed rangelands compared with controlled grazed and freely- grazed rangelands, respectively. Similarly, soil N mineralization was significantly greater (P<0.05) in ungrazed rangelands (3.3- to 3.5-folds) than in controlled grazed and freely-grazed rangelands at Boroujen site. However, at Sheida site with short-term ungrazing period and cropping history there were no significant and considerable differences in soil N mineralization among the three grazing regimes. Briefly, degraded rangelands at SabzKouh and Boroujen sites seem to recover rather quickly from long-term overgrazing with a proper grazing management, while rangeland ecosystems at Sheida site need a much longer period for steady-state conditions and for improvements in soil quality and fertility after long-term soil degradation and disturbance.

The growth and activity of microorganisms in arid soils have always been constrained withpersistent drought stresses. The aim of this study was to assess the role of superabsorbent Superab A200 in reducing drought stresses and its effect on N dynamics and enzyme activities of sandy and clay soils under laboratory conditions. A 2×4 factorial experiment consisting of two levels of soil moisture (30 and 70 % of the field capacity), and four levels of the superabsorbent (0, 0.1, 0.3 and 0.5 %, w/w) arranged in a completely randomized design with three replicates were carried out using two soil textures (sandy and clay). The application of the superabsorbent had a significant, positive effect on most measured properties. But the effect was largely depended upon the quantity of superabsorbent, soil texture and moisture level in the soil. Nitrogen mineralization, ammonification and nitrification rates, microbial biomass N, alkaline phosphatase and urease activities were significantly greater in the clay soils with 70% of the field capacity moisture than in the sandy soil with the same amount of moisture. This is likely due to the high level of C contents. Moisture and texture effects on most soil biological properties were significant. Results indicated that the cumulative ammonification and nitrification increased with increasing superabsorbent level where much of the increases occurred at lower levels than higher levels. The increase in nitrate and ammonium production with 0.1 % superabsorbent was greater than that with other superabsorbent levels.

Understanding nitrogen mineralization from different organic sources should be a key factor in developing efficient prediction of the need for nitrogen fertilization with minimal negative environmental impact. In order to investigate nitrogen mineralization rate in soils amended with compost, vermicompost and cattle manure, an experiment was done as factorial in a randomized complete block design in three replications. Four treatments (compost, vermicompost, cattle manure and soil alone), two temperature levels (8 and 25 0C) and two moisture levels (50% and 85% FC) were used for the 90 - day incubation study. Ammonium and nitrate were measured by spectrophotometer method. Results indicated that the mixed first-and zero-order kinetics model is the best model for our data. Cattle manure treatment had the highest Nmin at 25 0C (87.78 mgN/kg equal to 14.54% Ntotal) and the least value (23.62 mgN/kg equal to 4.62% Ntotal) was obtained for the compost treatment at 8 0C. N0k (nitrogen availability index) for treatments was in the following order: Cattle manure>Vermicompost >Compost. With increasing the temperature and moisture, N mineralization increased. Also Nmin positively correlated with N0 (r =0.583*), and N0k (r =0.834**).