اثر بقایای گندم غنی شده با قارچ پلوروتوس بر برخی شاخص‌های میکروبی خاک شور

ماده آلی فعالیت میکروبی خاک را افزایش می‌دهد و غنی‌سازی مواد آلی با ریزجانداران موجب افزایش قابلیت دسترسی عناصر غذایی در مواد آلی می‌گردد‌. هدف این پژوهش، مطالعه اثر شوری، تلقیح قارچ صدفی پلوروتوس و بقایای گندم بر کربن آلی، سرعت تنفس میکروبی، تنفس ناشی از سوبسترا، کربن زیست‌توده میکروبی، شاخص قابلیت دسترسی به کربن و ضریب متابولیکی بود. آزمایش به صورت طرح پایه کاملاً تصادفی با آرایش فاکتوریل و در سه تکرار در شرایط آزمایشگاهی انجام شد. فاکتورها شامل سه سطح شوری (0، 8 و 15 دسی‌زیمنس بر متر)، دو سطح مایه‌زنی پلوروتوس (0 و 5 درصد) و دو سطح بقایای گیاهی (0 و 1 درصد وزنی/وزنی) بود. نتایج نشان داد مایه‌زنی پلوروتوس و افزودن بقایای گندم باعث افزایش کربن آلی (98%)، سرعت تنفس میکروبی (90%)، تنفس ناشی از سوبسترا (%69) و کربن زیست‌توده میکروبی (%79) و کاهش ضریب متابولیکی (%6) خاک گردید. در مقابل شوری باعث کاهش تنفس (%78)، کربن زیست‌توده میکروبی (%81)، و قابلیت دسترسی به کربن (%23) شد. کمترین و بیشترین میزان فعالیت و زیست‌توده میکروبی به ترتیب در خاک شور تیمار نشده با بقایای گندم و پلوروتوس (s2f0r0) و در خاک غیرشور تیمار شده با بقایای گندم غنی‌شده با پلوروتوس (s0f1r1) مشاهده شد. نتایج نشان داد که در خاک‌های شور با محدودیت کربن آلی، افزایش سطح ماده آلی و غنی‌سازی آن با قارچ پلوروتوس، می‌تواند منجر به افزایش فعالیت میکروبی خاک گردد.

effect of wheat residue enriched with pleurotus on microbial characteristics of a saline soil

introduction: soil microorganisms play an important role in maintaining soil quality through the decomposition of organic matter and nutrients cycling. the quantity of plant residue has a positive effect on the accumulation of organic carbon in the soil. one of the most important problems hampering the release of nutrients from plant residues is the high content of lignocellulose in their structure. therefore, biological treatment has been considered as a candidate to improve lignocellulosic conversion and more release of nutrients from them. salinity reduces microbial biomass and decreases their activity in decomposition of soil organic matter and organic matter input into soil. due to the importance of the role of microorganisms in the storage and release of energy and nutrients in the soil, in recent years, increasing attention has been paid to the estimation of microbial activity and biomass in soil. therefore, the aim of this study was to study the effect of salinity, inoculation of pleurotus astreatus and wheat residue on respiration, microbial biomass carbon, organic carbon, carbon availability index and metabolic quotient.materials and methods: the experiment was conducted as a completely randomized design with factorial arrangement in three replications under controlled laboratory conditions at gorgan university of agricultural sciences and natural resources. factors included three salinity levels (0, 8 and 15 ds m-1), two fungal levels (0 and 5%) and two wheat residue levels (0 and 1%, w/w). salinity treatments including (control), 8 and 15 ds m-1 was applied using a mixture of salts (nacl, kcl and mgcl2 with a molar ratio of 3:2:1). wheat straw was treated pleurotus fungus and the treated straw was then thoroughly mixed into the soil. to activate the microbial population, soil moisture was adjusted to about 70% of the field capacity and the containers were pre-incubated at room temperature for 2 weeks. the samples were incubated at 25±2°c for 90 days. microbial biomass carbon, organic carbon was measured at monthly intervals, microbial respiration was measured weekly and substrate-induced respiration (sir) was measured once at the end of the incubation period.results and discussion: the results show that salinity has a negative effect on microbial activity and population, but wheat residues reduce the effect of salinity stress on soil microbial community. inoculation of pleurotus into the soil also increased the respiration and microbial biomass. the interaction of wheat residues and pleurotus on microbial activity in saline soil was greater than their effect alone. according to the results, the simultaneous addition of pleurotus and wheat residue increases organic carbon (%98), microbial respiration rate (90%), substrate respiration (69%) and microbial biomass carbon (79%) and decreases the metabolic coefficient (6%). salinity reduced respiration (78%), microbial biomass carbon (81%) and carbon availability index (23%), which indicates a decrease in carbon for microbial activity in saline soils. the lowest and highest microbial activity and biomass were in saline soil (15 ds m-1) not treated with wheat residues and pleurotus (s2f0r0) and in non-saline soils treated with wheat residues enriched with pleurotus (s0f1r1), respectively. the results showed that higher salinity level (15 ds m-1) further decreased the measured characteristics including carbon availability index, respiration and microbial biomass carbon compared with 8 ds m-1 salinity level in all treatments. in non-treated soil with wheat residue and pleurotus, salinity level of 8 ds m-1 reduced mbc by 43, 46 and 44 % compared to control (non-saline) soil.