Biochar amendment ameliorates soil properties and promotes Miscanthus growth in a coastal saline-alkali soil

Highlights

• Biochar ameliorated physicochemical and biological properties of saline-alkali soil.

• Biochar application mitigated salinity induced injuries to Miscanthus plants.

• Biochar application significantly promoted Miscanthus growth in saline-alkali soil.

Abstract

Biochar amendment has been proposed to be as a promising means to improve soil properties and enhance plant productivity in different types of soils. However, biochar application in the improvement of plant productivity in saline-alkali soils has received less attention. In the present study, we carried out a pot experiment in greenhouse to evaluate the effect of biochar amendment on the growth of Miscanthus lutarioriparius, a promising bioenergy crop, in a coastal saline-alkali soil during a 92-day growth period. The biochar was added at 0, 1.0%, 2.0%, 2.5%, 5.0%, and 10.0% (w/w) levels in a random block design with three replicates. The results showed that biochar applications at 2.0% and 2.5% levels significantly promoted Miscanthus growth by ameliorating the physicochemical and biological properties of the saline-alkali soil. The soil moisture, soil organic matter (SOM), nitrate nitrogen (NO₃⁻-N), available phosphorus (Olsen-P), and concentrations of potassium (K⁺), calcium (Ca²⁺) and magnesium (Mg²⁺) ions were significantly increased, while soil pH, bulk density, ammonium nitrogen (NH₄⁺-N), sodium (Na⁺) ion, and exchangeable sodium percentage (ESP) contents were substantially reduced. In addition, the soil bacterial community structure and diversity were substantially shifted after the biochar amendment, which in turn affected soil N and P cycling and improved soil physicochemical properties. Meanwhile, biochar application considerably mitigated the salinity stress to Miscanthus plants by activating anti-oxidative enzymes superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), therefore enhancing the scavenging capability of reactive oxygen species (ROS). Together, our results indicated that biochar amendment effectively promoted Miscanthus growth by ameliorating soil physical, chemical and biological properties, and alleviated salt stress injuries to plants in a coastal saline-alkali soil.

Introduction

Soil salinization is a worldwide problem, especially in arid and semi-arid regions. It has become one of the major limiting factors that hamper agriculture production globally (Wild, 2003). It is estimated that >1.1 billion hectare land, accounting for approximately 7% of the global land area, is affected by soil salinity to varying degrees (Wicke, 2011). Moreover, the area of salinity-affected land is keep increasing at a rate of approximately 1–2% annually due to global climate change, and improper irrigation and tillage practices (Munns and Tester, 2008).

Salinity adversely affects the growth of crops and causes an annual economic loss of at least 27.2 billion dollars in agriculture production all over the world (Qadir et al., 2014). On the one hand, it causes the increase of osmotic pressure of soil solution, and hinders normal water absorption from roots, resulting in physiological dehydration of plants (Munns, 2002). Salinity stress also triggers the excessive accumulation of reactive oxygen species (ROS) in plants, causing substantial oxidative damages that adversely affect plant growth (Miller et al., 2010). On the other hand, salinity adversely affects soil chemical and physical properties such as water retention capability, soil organic matter (SOM) and soil fertility. (Amini et al., 2016; Crescimanno et al., 1995; Läuchli and Lüttge, 2002). It also adversely affects the absorption of nutrients by plants, resulting in severe growth inhibition (Läuchli and Lüttge, 2002; Parida and Das, 2005). In addition, salinity stress affects soil biological properties by decreasing the abundance and diversity of microbial communities (Canfora et al., 2014). Moreover, soil salinization is usually accompanied by alkalization, thus causing more serious deteriorations of soil properties such as severe degradation in soil structural property, additional osmotic and toxicity effects on plants (Rengasamy, 2010).

As the global population is predicted to surge to 9.7 billion by 2050, the current arable land available cannot fulfill the increasing demands for the growing population. To cope with the ever-increasing global population, it is imperative to exploit the abundant saline-alkaline marginal land to cater for the rising demands in agricultural production (Wild, 2003). Recently, biochar amendment has received increasing attentions as an effective means in the remediation of various degraded soils including salinity-affected soils (Ahmed et al., 2016; Saifullah et al., 2018; Yu et al., 2019). Biochar is a carbon-rich porous material produced by pyrolysis of biomass under anaerobic or limited oxygen at relatively low temperature (<700 °C) conditions (Lehmann and Joseph, 2015). It possesses several extraordinary characteristics including porous structure, high specific surface area, and special physicochemical properties (Lehmann and Joseph, 2015). Biochar has been widely employed in various applications including carbon sequestration and reducing greenhouse gas emissions, improving soil fertility and crop yield, and remediating the contaminated or degraded soils (Ahmed et al., 2016; Laghari et al., 2016; Smith, 2016; Yu et al., 2019). Among these applications, biochar has attracted a particularly increasing attention as an effective means in the remediation of salinity-affected soils (Ali et al., 2017; Saifullah et al., 2018).

Recent years have witnessed increasing literature reports demonstrating that biochar application effectively promotes plant growth and improves plant productivity in saline-alkali soils. For example, incorporation of biochar remarkably ameliorates the adverse effects of salinity on potato growth and yield in saline soils (Akhtar et al., 2015a). Likewise, biochar application significantly decreases Na⁺ uptake and enhances the growth and productivity of wheat in a salinity-affected soil (Akhtar et al., 2015b). Similarly, biochar application alleviates salt stress by reducing Na⁺ uptake and leads to enhanced yield and quality of tomato in a saline soil (She et al., 2018). Additionally, biochar amendment significantly promotes the growth of two halophyte plants by improving soil physicochemical properties, and shifts the bacterial community structure in a coastal saline-alkali soil (Zheng et al., 2018). Despite that the recent application of biochar in the reclamation of saline-alkali soil has attracted increasing attention, there are still large knowledge gaps underlying the mechanisms of biochar amendment in ameliorating soil properties and mitigating salinity-induced stress in plants.

In this study, we examined the effects of biochar amendment on soil physicochemical and biological properties, and the growth performance of Miscanthus lutarioriparius, a promising bioenergy crop, in a coastal saline-alkali soil. The main objective of our investigation lies in the following aspects: (1) explore the mechanisms of biochar application in the improvement of physicochemical properties of saline-alkali soil; (2) clarify the effects of biochar application on the alteration in bacterial community composition and diversity in saline-alkali affected soil; (3) elucidate the mechanisms of biochar amendment in mitigating salt stress and promoting Miscanthus establishment in the saline-alkali soil. The results obtained may provide beneficial guidance for the reasonable application of biochar in the reclamation of salinity-affected soils.