Search

Restoring and reconstructing the salt-affected degraded ecosystem is receiving more and more attention in many parts of the world, especially semi-arid areas. Unfortunately, knowledge about the potential role of natural arbuscular mycorrhizal (AM) fungi was limited. This work examined the regional factors that drove the variations in AM fungal diversity in Songnen Plain, a typical saline-sodic degraded grassland. Soils were sampled in 45 random sites, 150 operational taxonomic units (OTUs) belonging to Glomeromycota were identified. Among these OTUs, 129 and 103 OTUs were classified to Glomerales and Glomus, respectively. The coefficients of variation of total diversity index were 35.61% and the total effects of soil salinity and nutrients collectively accounted for 31.2, 11.8, 47.3, and 64.2% of the variations in Sobs, Chao, Shannon, and Simpson indices, respectively. The climatic variables and geographical location had no significant effects on the variations of AM fungal diversity. Multiple linear regression models showed that soil pH, electrical conductivity (EC), available N and organic C were the most main influencing factors. This research highlighted the wide distribution of AM fungi and thus might promote the development of new techniques that apply natural AM fungi to restore saline-sodic degraded grasslands. [ABSTRACT FROM AUTHOR]

Application of sand can ameliorate rice paddy fields converted from saline–sodic land. However, the requirement of huge amount of sand has been limiting its practical application. In this study, flushing during saline sodic-sensitive stages of rice plant growth was incorporated into the ameliorating system to reduce the sand usage. A split-plot design was adopted with sand application (SA) with two levels as main plots and flushing during the sensitive stages (FL) with two levels as subplots in a hard saline–sodic soil, Northeast China. Four treatments included CK (no-sand, no-flush flooding), NF (non-sand, flush flooding), SN (sand, no-flush flooding), and SF (sand, flush flooding). The results showed that both SA and FL significantly affected all the investigated yield parameters. The combined effect of SA and FL on the grain yield was additive in the first year in respect of the effect on panicle density and seed weight per panicle; while it showed synergistic effect on the seed weight per panicle and grain yield in the second year. The rice yield in different treatments was in the order of SF > SN > NF > CK in both years, with the highest yield (4.37 t ha−1) obtained by SF treatment in the second year. Our results demonstrate that half the traditional amount of sand in combination with water-flushing during the saline–sodic-sensitive growth stages of rice is sufficiently effective in ameliorating saline–sodic soil and thereby enhancing rice grain yield in saline–sodic paddy fields. [ABSTRACT FROM AUTHOR]

• Soil salinization in the west of Jilin province for a long term was monitored. • Meteorological conditions are the most relevant and important factors in soil salinization. • The implementation of government policies reversed the saline soil expansion. • Salinized soil was mainly converted to grassland and cropland. Soil salinization is a serious land degradation phenomenon that significantly affects regional economies and agricultural development. Since the 1980s, the state of soil salinization has been constantly changing due to various climatic conditions, human activities, and the application of soil improvement measures. In this study, the Landsat-5 TM and Landsat-8 OLI satellites, launched in 1984 and 2013, respectively, were used to track changes in soil electrical conductivity (EC), a key indicator of soil salinity. A remote-sensing inversion model for the EC of saline-sodic soil was established (R = 0.5), and the soil EC in western Jilin Province from 1989 to 2019 was inverted. Then, the temporal and spatial variation characteristics of the soil salinization degree were counted, and the related variables and influencing factors were analyzed. The results are in good agreement with the conclusion that meteorological conditions are the most relevant and important factors in soil salinization. The area of saline soil increased continuously in the natural state (from 1989 to 1999), and the implementation of government policies (1999 to 2019) reversed the saline soil expansion, converting large areas of saline soil to grassland and cropland. This study is the first to quantitatively analyze the degree of soil salinization and its influencing factors in western Jilin Province from 1989 to 2019; this work also successfully predicted and monitored the variation in soil salinization. This provides data support for the study of the dominant elements in soil salinization changes and the rational development of land. [ABSTRACT FROM AUTHOR]

Abstract: Field experiments were carried out to investigate water and salt management and its effects on Leymus chinensis growth under drip irrigation on saline-sodic soils of the Songnen Plain, China. The ECe of the experiment soil here is 15.2dS/m and SARe is 14.6 (mmolc L−1)1/2. The threshold of soil matric potential (SMP) was preset in different treatments (−5, −10, −15, −20 and −25kPa) to control the timing of the irrigation cycle using vacuum tensiometers buried at 0.2m depth immediately under drip emitters. Drip irrigation frequency and soil matric potential significantly influenced water and salt distributions and L. chinensis growth. In the root zone, the soil water content increased with the SMP, but at deeper layers there were no significant differences in soil water content due to the effect of groundwater. Electrical conductivity showed that there was a low-salt zone near the emitters and that drip irrigation inhibited the buildup of salts in the root zone. There was more leaching of salts for −5 and −10kPa treatments than for the −15, −20 and −25kPa treatments. After two years of drip irrigation, the surface salts were well leached, and had moved down with the water to depths below 40cm. The pH of each treatment was a little decreased and the soil nutrient of S1–S5 were all increased after reclamation, but there were no obvious differences of the five treatments. The best growth was achieved with soil matric potentials of −5 and −10kPa: the plant height, number and length of spikes, number of tillers, coverage and aboveground biomass all attained their maximum values during the growth periods of L. chinensis, with no significant differences between those two treatments. Thus, in the Songnen Plain, drip irrigation can be used on transplanted L. chinensis for restoration of saline-sodic soils. The results provide theoretical and technological guidance for sustainable reclamation salt-affected soil and the quick restoration and reconstruction of saline-sodic grassland. [Copyright &y& Elsevier]

Soil sodicity is a major ecological problem in the western Songnen Plain of Northeast China and rice cultivation is the main approach used to mitigate saline-sodic soils. However, rice cultivation alone may not be the most effective practice. This study aimed to investigate the combined effects of annual tillage and rice cultivation with either phosphogypsum or farmyard manure on soil salinity, mineral status, and concentration of heavy metals in saline-sodic paddy fields. Treatments were: 1) untreated (no amendments), untilled, and uncultivated (no rice) saline-sodic native grasslands (UG); 2) untreated, tilled, rice-cultivated paddy fields (PFU); 3) tilled, rice-cultivated, amended paddy fields with phosphogypsum (PFPG); and 4) tilled, rice-cultivated, amended paddy fields with farmyard manure (PFFM). The effectiveness of these treatments on soil improvement was evaluated after a 10-year field experiment. Compared to the UG control, the 0–20 cm topsoil layer of PFU, PFPG, and PFFM had respective decreases in Na+ concentrations of 42.9%, 61.5%, and 60.9%; in CO 3 2- + HCO 3 - concentrations of 18.9%, 63.2%, and 57.9%; in Cl- concentration of 64.6%, 75.7%, and 79.9%; in pH units of 0.57, 1.05, and 1.30; in soil electrical conductivity (EC 1:5) of 18.3%, 49.1%, and 48.3%; and in exchange sodium percentage (ESP) of 47.2%, 66.9%, and 72.5%. Also, the 0–20 cm topsoil layer of PFPG and PFFM had its concentrations of soil organic matter (SOM), available nitrogen (AN), and available phosphorus (AP) significantly (P < 0.05) increased compared to the UG control. However, the concentrations of five heavy metals (As, Pb, Cd, Cr, and Hg) were kept within a safe range in saline-sodic paddy fields amended with phosphogypsum or farmyard manure and were far below the environmental quality standard held for Chinese soils. Therefore, phosphogypsum and farmyard manure significantly decreased soil salinity and sodicity while increased soil fertility and SOM. Because these amendments are locally available and affordable to farmers, their use is deemed suitable for large-scale soil reclamation and the mitigation of salinity and sodicity in soils destined for rice cultivation in Northeast China. • High soil pH and salinity significantly inhibited soil fertility improvement. • Tillage and rice crop alone did not significantly reduce soil salinity and sodicity. • Phosphogypsum and farmyard manure significantly improved soil chemical characteristics. • Phosphogypsum or farmyard manure did not increase soil heavy metals. • Tillage and both amendments are feasible resources for saline-sodic soil improvement. [ABSTRACT FROM AUTHOR]