Application of carboxymethyl cellulose sodium (CMCNa) in maize-wheat cropping system (MWCS) in coastal saline-alkali soil

Sodium carboxymethyl cellulose (CMCNa) application has been a promising approach to improve soil quality. The purpose of this study was to explore the effects of CMC-Na on soil infiltration, evaporation, water-salt distribution, crop growth, water use efficiency and net profit (Net) in a coastal saline-alkali soil maize-wheat cropping system (MWCS). Five CMC-Na application amounts (0, 0.1, 0.2, 0.4 and 0.6 g kg-1) were designed for the soil column experiment indoor, and five CMC-Na application amounts were used in 2019-2020 field experiment (CK: 0, C10: 10 kg ha-1, C20: 10 kg ha-1, C30: 10 kg ha-1 and C50: 10 kg ha-1), No treatment will be applied in 2021. The results showed that (1) CMC-Na treatment reduced soil cumulative infiltration, infiltration rate, daily evaporation, and cumulative evaporation. (2) After the application of CMCNa, the average soil water storage (SWS) in the 0-60 cm soil layer increased, and soil salinity (SSC) decreased in most treatments. (3) In the 2019-2020, the maize aboveground biomass (B), yield (Y) and water use efficiency (WUE) were the highest under the C20 and C30 treatments, which were 15.24 and 15.32 t ha-1, 5.67 and 5.49 t ha-1 and 1.74 and 1.52 kg ha-1 mm-1, respectively, and the wheat under C30 treatment is the highest, which were 10.98 t ha-1, 5.27 t ha-1 and 1.78 kg ha-1 mm-1. (4) A dose of 25.5 kg ha-1 and 38.9 kg ha-1 was recommended as the most optimal CMC-Na application for maize and wheat in coastal saline alkali soil, respectively.

Effects of different Tamarix chinensis-grass patterns on the soil quality of coastal saline soil in the Yellow River Delta, China

Construction of circumlittoral shelter forest is of great significance to maintain ecological security of coastal zones, the safety of people's lives and property in the Yellow River Delta (YRD) in China. Tamarix chinensis-grass patterns have shown obvious advantages in construction of circumlittoral shelter forest and improving the soil quality of coastal saline soil. This study aimed to explore the soil-improving effects of various Tamarix chinensis-grass community patterns and identify the best vegetation pattern for improving the soil quality in the coastal saline-alkali land. Six kinds of Tamarix chinensis-grass community patterns were selected from the saline-alkali soil of the YRD, with bare land as the control. Effects of different Tamarix chinensis-grass patterns on the coastal saline soil were evaluated using statistical methods (e.g. principal component analysis and fuzzy membership function method). The results showed that various Tamarix chinensis-grass community patterns significantly decreased the salt contents and increased the available nutrient contents in the coastal saline-alkali soil. The soil improvement effects showed obvious distinctions among the different Tamarix chinensis-grass patterns. The mixed forest-grass pattern consisting of Tamarix chinensis, Phragmites australis, and other salt-resistant grasses showed the best effects in relation to reducing salt, preventing alkalization and increasing the soil nutrients, which resulted in the lowest salt contents and the highest nutrients. Grass species play a major role in increasing soil nutrient contents, and the density of new Tamarix chinensis forest contributes greatly to the decrease of soil salt. And the more kinds of grass species are, the better improvement effects they will have. Therefore, during the construction of the circumlittoral shelter forest system in the muddy coastal zone of the YRD, it is recommended to prioritize the high density Tamarix chinensis-Phragmites australis (TPA) community pattern, and live together with other kinds of salt-resistant grasses.

Biochar and effective microorganisms promote Sesbania cannabina growth and soil quality in the coastal saline-alkali soil of the Yellow River Delta, China

Soil salinization and nutrient deficiency have emerged as the major factors negatively impacting soil quality and primary productivity in the coastal saline-alkali soil of the Yellow River Delta. Biochar has been proposed as an efficient strategy for promoting plant growth and restoring degraded saline-alkali soil. However, knowledge is inadequate regarding the effects of adding Spartina alterniflora-derived biochar alone or in combination with effective microorganisms (EM) on the growth of Sesbania cannabina and soil quality in saline-alkali soil. To enhance this knowledge, a pot experiment with different EM treatments (without EM addition, EM-; with EM addition, EM+) and a gradient of biochar treatments (0%, B₀; 0.5%, B₁; 1.5%, B₂; and 3%, B₃; biochar weight/soil weight) was conducted. Our results showed that biochar addition alone and in combination with EM significantly increased seed germination, plant height, stem diameter, total biomass and plant nutrient uptake of S. cannabina. Biochar addition, EM addition and their interaction significantly decreased soil salt content efficiently and increased soil total carbon (TC), total nitrogen (TN), available phosphorus (AP) and available potassium (AK) but had little effect on soil pH. Biochar addition increased soil organic carbon, soil NH₄⁺ and NO₃-, microbial biomass carbon, and soil enzyme activities and these effects increased in strength when biochar and EM were present simultaneously. Of the treatments, the EM + B₃ treatment had the largest effects in terms of inhibiting salinization, increasing soil fertility, elevating soil nutrients and enzyme activities, and improving plant growth. Moreover, the application of biochar and EM promoted the growth of S. cannabina by enhancing plant nutrient uptake, improving soil fertility (e.g., TN, AP, AK, NH₄⁺ and NO₃^-), and elevating soil enzyme activities (urease and alkaline phosphatase activity). Overall, the integrated use of an appropriate biochar rate (3%) and EM for coastal saline-alkali soil could be an effective strategy to ameliorate soil salinity, improve soil quality and promote plant productivity.

Effects of pyrolysis temperature on soil-plant-microbe responses to Solidago canadensis L.-derived biochar in coastal saline-alkali soil

Because salinity of coastal soils is drastically increasing, the application of biochars to saline-alkali soil amendments has attracted considerable attention. Various Solidago-canadensis-L.-derived biochars prepared through pyrolysis from 400 to 600 °C were applied to coastal saline-alkali soil samples to optimise the biochar pyrolysis temperature and investigate its actual ecological responses. All biochars reduced the soil bulk density and exchangeable sodium stress and increased soil water-holding capacity, cation exchange capacity, and organic matter content. Principal-component-analysis results showed that pyrolysis temperature played an important role in the potential application of biochars to improve the coastal saline-alkali soil, mainly contributed to ameliorating exchangeable sodium stress and decreasing biochar-soluble toxic compounds. Furthermore, soil bulk density and organic matter, as well as carboxylic acids, phenolic acids and amines of biochar were major driving factors for bacterial community composition. Compared to low-temperature biochar (pyrolyzed below 550 °C), which showed higher toxicity for Brassica chinensis L. growth due to the higher content of carboxylic acids, phenols and amines, high-temperature biochar (pyrolyzed at or above 550 °C) possessed less amounts of these toxic functional groups, more beneficial soil bacteria and healthier for plant growth. Therefore, high-temperature biochar could be applied as an effective soil amendment to ameliorate the coastal saline-alkali soil with acceptable environmental risk.