| Salinity is the most extending land degradation problem in the arid and semi arid regions of the world due to climate change and a severe environmental factor limiting the productivity of agriculture. Currently, half of the world irrigated land resources and approximately 20% of the agricultural land has been affected by salinity. Moreover, every year 1.5 million hectares of productive land severely affected by salinity and becomes unproductive. Accumulations of salts, particularly salts of sodium exert physiological threats to ecosystem, prevent normal metabolic functions, and hinder water absorption, nutrient uptake of the plant and soil biota. Salinity has drastic effects on plant, secondary effects of toxic salts causes injury of leaf cell, further reduces growth by specific ion toxicity. Salinity may also effects on the physical and chemical properties of soil, such a way increase soil compaction reduce the aeration. Thus, high levels of salts can dehydrate soil microbes and reduces soil microbial functions and nutrient transformation. Considering all inferior effects of soil salinity a study was designed with biochar based technology to reclaim salt-affected soil as a sustainable source for crop production and utilization of saline soil.This study is to address the potential of using biochar-based technology to ameliorate salt stressed soil with a number of experiments on soil and plant health changes. A two-year field experiment with soil amendment of biochar-poultry manure compost (BPC) and pyroligneous solution (PS) was conducted in a moderately salt stressed Entisol from Central China. The soil was amended with BPC at 12 t ha-1 following treatment with diluted PS solution at 0.15tha-1 1 week before winter wheat sowing. Samples of topsoil (0-20 cm) were collected for the determination of detailed soil physical and chemical properties, bulk and maize rhizosphere soil was collected for soil microbial community structure and soil enzymes activity. Plant samples were collected for major nutrient and sodium content in plant biomass while the yield of wheat and maize was measured when crop harvested. Plant samples for bio-molecules enzymes were collected at vegetative growth stage of maize crop.The detailed analysis of soil physical properties, leaching of salts from the root zone of crop, improvement in nutrient content in soil and plant biomass with the (BPC-PS) amendment and untreated salt-affected soil were determined through adopted laboratory techniques. Scanning electron microscopy (SEM) was used to examine the salt content in fresh and aged biochar particles collected from the salt-affected field. Soil microbial biomass and enzymes were determined by usual method. Microbes in bulk soil and maize rhizosphere (bacterial and fungal) community structure and abundances were assessed by culture-independent molecular techniques including polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and quantitative real-time (qPCR), respectively. Moreover, important band retrieved from DGGE gel were analyzed using sequencing and phylogenetic analysis for further details of soil organisms.The main results are:1) The changes in soil salinity, fertility properties as well as crop yield were examined with comparison between the plots treated for one year and for two years. In the first cropping year of 2010-2011, a significant decrease under BPC-PS amendment was observed in soil salinity, soil pH and in soil bulk density while increase was seen in soil organic carbon and available phosphorous. The yield was increased over the control by several folds under BPC-PS treatment respectively for 1 year and for 2 years. Furthermore, the decrease in soil salinity, soil pH, and bulk density was even greater in the plots treated for 2 years than for one year though the yield under the treatment was not significantly different between the consecutive two years with a spring drought in 2012. These results demonstrated a strong effect of BPC-PS treatment on salinity reduction and crop productivity enhancement in the salt stressed soil, which could sustain for at least two years.2) Amendment of (BPC-PS) show effective role in the improvement of soil properties and maize growth. Significant decreases in soil pH, SAR and ESP as well as in ECs and total salts with the amendment of BPC-PS over the untreated salt-affected soil. The scanning electron microscope (SEM) observation indicates high content of Na in old biochar particles collected from two year old amended salt-stressed soil compared with one year old amended biochar particles. Moreover, the maximum increase in maize plant growth, leaf area index, plant density, root length and leaf relative water content with were found with the (BPC-PS) amendment and a significant decrease in the leaf electrolytes leakage. Furthermore, the nutrient content maize leaf sap nitrogen, phosphorous, potassium, K/Na ratio and total chlorophyll concentration was increased at vegetative growth stage while sodium and chloride concentration decreased with BPC-PS amendment. The amendment greatly improves the physiological disorder in maize leaf and decrease proline, lipid peroxidation (MDA), ascorbic acid, soluble sugar and amino acids in the dry matter of maize leaf. Thus, the amendment greatly improved root and shoot growth of maize plant, nutrient content in leaf sap, low content of Na+ and Cl-,maintain physiological and biochemical disorder of maize crop while alleviated the salt stress on maize plant.3) The nutrient content in aliquots of leaf, root and maize grain, uptake of Na, K/Na ratio and protein content in grain was determined and yield reported at harvest of maize crop. Results showed a significant improvement in maize dry matter and grain yield with the (BPC-PS) amendment over the non-amended salt-affected crop plot. However, the major nutrient content (NPK) in maize leaves, roots, grains and grain protein content were increased with the amendment of BPC-PS 1 and BPC-PS2 over the untreated salt-stressed maize plant. Moreover, the significant reduction was observed in Na+ content in plant dry matter and increases in K/Na ratio with the amendment. However, the fungal infected, poor quality grains were observed in the maize plant was grown in untreated salt-affected cropland.4) Results showed that total soil microbial biomass carbon and nitrogen were significantly increased both in bulk and rhizosphere samples, being greater under BPC-PS2 than under BPC-PS 1. However, the increase in bacteria (16S rRNA gene) abundance was seen higher under BPC-PS2 than under BPC-PS 1, but the reverse for fungi (18S rRNA gene), both in bulk and rhizosphere samples. Furthermore, two new single bands belonging respectively to Alphaproteobacteria and Deltaproteobacteria emerged in the amended soil. Coincidently, activities of urease, invertase and phosphatase in rhizosphere were increased by 11-27% with the BPC-PS amendment over the control. Thus, total microbial biomass; gene abundance and bacterial diversity as well as soil enzyme activity was greatly enhanced with the use of biochar-based ecotechnology in the salt-stressed soil. Therefore, soil microbiological health was greatly improved under the biochar-based treatment, which could be beneficial for plant growth and yield performance observed. Therefore, the finding of this study showed that biochar-based ecotechnology is effective source for the reclamation of salt-affected soil, crop health, nutrient improvement and soil biodiversity. |
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