Document Type : Research Paper
Authors
Abstract
Introduction: After salinity, drought is of the most common environmental stress for plants in the world and a significant proportion of natural ecosystems and agricultural world is located under salt stress. In general, preventing plant growth of salinity may be due to improper plant photosynthesis, and stomata closure due to the limitation of carbon dioxide is absorbed. Previous studies have shown an increase in the electrical conductivity of the soil with microbial biomass, microbial respiration, and plant residue decomposition rate is negative. The results of studies have showed that the organic matter in soils with high salinity levels even with low vegetation can cause grow the microbial populations resistant to salinity, rapidly. Therefore, the increase residual plants enhance the activity of soil microbes which are beneficial to decompose and release carbon dioxide, nitrate and other ingredients. In arid and semi-arid lands soil organic matter in the soils is generally poor, because of the high temperature maintain and preserve organic matter in these soils is very difficult. Although the use of mineral fertilizers is apparently the faster way is to maintain soil fertility, but the high cost of fertilizer, and cause soil pollution and environmental degradation, is unfavorable act. The aim of this study was to evaluate the effect of plant residues on soil microbial characteristics such as carbon, nitrogen and phosphorus biomass influence on barley plant growth at different levels of soil salinity.
Materials and Methods: To make salty soil 40 liters of salinity effluent collected with EC about 33.4 dS /m and after the initial analysis, was diluted and three levels of salinity (2, 4, 8 dS m) were created. After preparing the soil with 3 levels of salinity (2, 4, 8 dS/m), 2 types of debris from wheat straw and alfa alfa (2 levels, zero and 100 g per pot) with 3 replications (total of 36 pots) were prepared. After cultivation of barley seeds, the pots were irrigated. The experiment was conducted in a completely randomized design in a greenhouse. Wet pots were kept at 60 percent of field capacity and irrigation was done by weight. To evaluate the plant's response to the effects of crop residue added at the end of the experiment, after 60 days, shoot and root samples were collected. All samples of barley leaves and stems of the plants were collected two months after planting. The amount of chlorophyll by chlorophyll meter was measured manually by Spad units. Plant height was determined by ruler from the surface to the end of the cluster. For the measurement of pH and EC plant debris from shattered remnants extract ratio (1: 8) was used. Carbon and nitrogen biomass by fumigation extraction method was measured.
Results and Discussion: Effect of salinity and crop residue application on barley plant height was significant at 1% level. But, there was no significant interaction between salinity and treated straw. The effect of wheat residue treatment was significant on plant height, but showed a decreasing trend with increasing salinity. Comparison of means of salinity levels showed the greatest reduction in leaf area in 3 salinity levels of the treated straw and the lowest was of the hay treatment. The comparison of means of salinity levels showed that the treated straw had the lowest chlorophyll compared to other treatments. The effect of the addition of plant residues in different levels of salinity on microbial biomass carbon was significant at 1% level. Adding mineralization of organic waste leads to increased precursor enzymes and microbial growth increases. The results showed that moderate amounts of carbon, nitrogen and phosphorus microbial biomass was affected by increasing salinity in reverse. The amount of phosphorus added to the soil was deeply influenced by phosphorus ratio of carbon to biomass and biomass is phosphorus. P ratio of carbon to biomass increased by reducing the availability of phosphorus. Changes in the ratio of carbon to microbial biomass P refers to changes in microbial communities in soil. Reduced microbial biomass carbon in soils containing straw because of organic compounds toxic like phenols produced the soil micro-organisms. Increased alfalfa and crop residue as organic fertilizer to the soil salinization significantly affects the microbial biomass nitrogen. Comparison of the results showed that microbial biomass phosphorus in 3 salinity levels was, at 1%, significantly different from control and treatment straw and in between treatments; alfalfa treatment significantly increased microbial biomass phosphorus.
Conclusion: The results indicated that salinity reduced height, leaf area and plant chlorophyll content of barley. Added plant residues at different levels of salinity, while increasing soil organic matter and soil microbial, somewhat affected the barley crop yields. This effect was different depending on the type and quality of plant residues. Hay debris due to available nutrients, especially nitrogen and phosphorus, reduced soil salinity, and crop yield was somewhat increased, but the impact of wheat residues was not observed on the plant atmosphere. The results also showed that with increasing salinity of soil, microbial indexes such as microbial biomass carbon and nitrogen was decreased.
Keywords
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