Regulatory Mechanism of Wheat Straw and Cotton Stalk Biochar on Silicon Morphological Transformation and Salt Ion Dynamics in Rhizosphere Soil

doi:10.11924/j.issn.1000-6850.casb2026-0228

Abstract

Abstract:

This study was designed to investigate the pathways and mechanisms by which biochars with contrasting silicon contents ameliorate rhizosphere salinized soils. A pot experiment was established using wheat-straw (WS) and cotton-straw (CS) biochars pyrolyzed at 300℃ and 500℃, designated as WS300, WS500, CS300, and CS500, with a no-biochar treatment as the control (CK). The effects of these biochars on rhizosphere microenvironments, silicon speciation transformation, and ionic uptake were systematically assessed. The results revealed that WS-derived biochars consistently outperformed CS-derived counterparts in terms of labile silicon fractions (i.e., water-soluble and amorphous silicon) and ion-releasing capacity, with low-temperature (300℃) pyrolysis being more favorable for retaining these active constituents. Specifically, WS300 triggered a rapid efflux of salt ions at the tillering stage, substantially elevating rhizosphere electrical conductivity (EC) and concurrently increasing the concentrations of Na⁺, Cl^-, K⁺, and Ca²⁺, thereby establishing a high-salt priming microenvironment. By the harvest stage, the available silicon content under WS300 treatment was approximately 1.15-fold and 2.35-fold higher than that under CS300 and CS500, respectively. Post-incubation characterization of WS300 biochar showed surface Si enrichment accompanied by decreased Cl and Ca levels, indicating a surface-mediated process wherein rapid salt release was coupled with concurrent silicon immobilization. In contrast, CS500 biochar, possessing a denser microstructure, exhibited lower silicon availability and slower salt release. WS500 biochar, however, continuously optimized rhizospheric ionic balance by reducing the Na/Cl ratio and elevating the K/Na ratio at tillering, maintaining Ca/Mg stability at flowering, and sustaining the highest K/Na ratio at harvest. These findings further suggest a synergistic coupling between salt liberation and silicon activation. The functional traits of the tested biochars were distilled into two dominant axes: WS300 was distinguished by its superior labile silicon content and high K/Na selectivity, whereas CS500 was characterized by high salt loading. Collectively, this work clarifies the divergent regulatory pathways of wheat-straw versus cotton-straw biochars in modifying rhizosphere environments, providing a theoretical basis for the targeted design and application of silicon-variable biochars in arid saline agricultural regions.

Key words: wheat straw biochar, rhizosphere soil, silicon morphological transformation, salt ions, K/Na ratio

CLC Number:

S153

HU Tianqiao, WANG Yaofeng. Regulatory Mechanism of Wheat Straw and Cotton Stalk Biochar on Silicon Morphological Transformation and Salt Ion Dynamics in Rhizosphere Soil[J]. Chinese Agricultural Science Bulletin, 2026, 42(17): 76-88.

Figures/Tables 20

References 48

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处理	pH(1:20)	EC(1:20)/(mS/cm)	产率/%	灰分/%	Na⁺/(g/kg)	K⁺/(g/kg)	Ca2+/(mg/kg)	Mg²⁺/(mg/kg)	Cl^-/(g/kg)
WS300	9.64	8.33	36.69	24.25	10.03	33.65	23.00	8.052	1.30
WS500	10.55	6.59	33.33	35.25	2.55	32.70	10.80	3.90	1.08
CS300	9.58	2.89	35.44	20.25	3.43	18.32	23.50	58.56	0.25
CS500	10.14	3.89	33.33	18.00	3.98	22.60	31.50	11.59	0.40

处理	pH(1:20)	EC(1:20)/(mS/cm)	产率/%	灰分/%	Na⁺/(g/kg)	K⁺/(g/kg)	Ca2+/(mg/kg)	Mg²⁺/(mg/kg)	Cl^-/(g/kg)
WS300	9.64	8.33	36.69	24.25	10.03	33.65	23.00	8.052	1.30
WS500	10.55	6.59	33.33	35.25	2.55	32.70	10.80	3.90	1.08
CS300	9.58	2.89	35.44	20.25	3.43	18.32	23.50	58.56	0.25
CS500	10.14	3.89	33.33	18.00	3.98	22.60	31.50	11.59	0.40

处理		Na⁺	Cl^-	K⁺	Ca²⁺	Mg²⁺
分蘖期	CK	0.27±0.17b	0.05±0.02c	0.2±0.03c	0.15±0.02b	0.03±0.02a
	WS300	0.54±0.09a	0.2±0.05a	1.5±0.17a	0.60±0.31a	0.08±0.06a
	WS500	0.33±0.07b	0.14±0.04b	1.53±0.22a	0.29±0.14ab	0.12±0.08a
	CS300	0.32±0.09b	0.07±0.02c	0.73±0.16b	0.17±0.03b	0.07±0.04a
	CS500	0.27±0.04b	0.06±0.01c	0.63±0.07b	0.20±0.04b	0.12±0.1a
扬花期	CK	0.14±0.04ab	0.03±0bc	0.2±0.04b	0.3±0.03a	0.02±0.02a
	WS300	0.33±0.13a	0.10±0.04a	1.11±0.29a	0.26±0.09ab	0.08±0.03a
	WS500	0.28±0.16ab	0.08±0.03ab	1±0.2a	0.31±0.1a	0.17±0.05a
	CS300	0.09±0.02b	0.03±0c	0.21±0.05b	0.13±0.02bc	0.08±0.04a
	CS500	0.11±0.03b	0.03±0bc	0.32±0.07b	0.12±0.03c	0.05±0.03a
收获期	CK	0.17±0.08a	0.04±0.01bc	0.2±0.08c	0.2±0.07a	0.09±0.03a
	WS300	0.2±0.02a	0.06±0ab	0.69±0.06ab	0.21±0.1a	0.08±0.03a
	WS500	0.18±0.05a	0.06±0.02a	0.87±0.23a	0.19±0.02a	0.08±0.03a
	CS300	0.19±0.05a	0.04±0.01abc	0.41±0.16bc	0.16±0.03a	0.10±0.04a
	CS500	0.14±0.04a	0.03±0.01c	0.32±0.12c	0.17±0.03a	0.04±0.02a

处理		Na⁺	Cl^-	K⁺	Ca²⁺	Mg²⁺
分蘖期	CK	0.27±0.17b	0.05±0.02c	0.2±0.03c	0.15±0.02b	0.03±0.02a
	WS300	0.54±0.09a	0.2±0.05a	1.5±0.17a	0.60±0.31a	0.08±0.06a
	WS500	0.33±0.07b	0.14±0.04b	1.53±0.22a	0.29±0.14ab	0.12±0.08a
	CS300	0.32±0.09b	0.07±0.02c	0.73±0.16b	0.17±0.03b	0.07±0.04a
	CS500	0.27±0.04b	0.06±0.01c	0.63±0.07b	0.20±0.04b	0.12±0.1a
扬花期	CK	0.14±0.04ab	0.03±0bc	0.2±0.04b	0.3±0.03a	0.02±0.02a
	WS300	0.33±0.13a	0.10±0.04a	1.11±0.29a	0.26±0.09ab	0.08±0.03a
	WS500	0.28±0.16ab	0.08±0.03ab	1±0.2a	0.31±0.1a	0.17±0.05a
	CS300	0.09±0.02b	0.03±0c	0.21±0.05b	0.13±0.02bc	0.08±0.04a
	CS500	0.11±0.03b	0.03±0bc	0.32±0.07b	0.12±0.03c	0.05±0.03a
收获期	CK	0.17±0.08a	0.04±0.01bc	0.2±0.08c	0.2±0.07a	0.09±0.03a
	WS300	0.2±0.02a	0.06±0ab	0.69±0.06ab	0.21±0.1a	0.08±0.03a
	WS500	0.18±0.05a	0.06±0.02a	0.87±0.23a	0.19±0.02a	0.08±0.03a
	CS300	0.19±0.05a	0.04±0.01abc	0.41±0.16bc	0.16±0.03a	0.10±0.04a
	CS500	0.14±0.04a	0.03±0.01c	0.32±0.12c	0.17±0.03a	0.04±0.02a

处理		水溶态硅	有效态硅	有机结合态硅	铁锰结合态硅	无定形硅
分蘖期	CK	0.40±0.13a	8.65±1.62a	14.74±5.95a	0.36±0.08a	0.43±0.05a
	WS300	0.33±0.09a	6.72±1.44a	15.56±5.42a	0.34±0.07a	0.43±0.06a
	WS500	0.47±0.16a	8.07±1.11a	15.44±3.76a	0.29±0.03a	0.42±0.05a
	CS300	0.52±0.08a	9.23±1.73a	10.67±2.58a	0.34±0.05a	0.47±0.04a
	CS500	0.54±0.06a	9.16±2.21a	11.04±2.48a	0.53±0.30a	0.42±0.05a
扬花期	CK	0.42±0.07a	6.76±1.93a	15.05±6.58a	0.67±0.54a	0.51±0.06a
	WS300	0.40±0.05a	10.36±4.36a	20.75±14.42a	0.44±0.08a	0.57±0.07a
	WS500	0.54±0.26a	6.08±1.10a	20.91±4.88a	0.4±0.07a	0.44±0.03a
	CS300	0.46±0.06a	6.51±2.18a	21.11±9.27a	0.46±0.06a	0.49±0.13a
	CS500	0.49±0.11a	6.52±1.31a	18.34±3.87a	0.44±0.05a	0.54±0.18a
收获期	CK	0.42±0.08a	6.18±1.39ab	21.19±3.93ab	0.46±0.14a	0.43±0.02a
	WS300	0.50±0.04a	10.64±3.49a	30.52±6.54a	0.39±0.14a	0.45±0.01a
	WS500	0.44±0.05a	7.04±1.57ab	31.11±4.09a	0.36±0.06a	0.38±0.04a
	CS300	0.45±0.08a	9.26±2.04a	15.46±7.58b	0.43±0.11a	0.37±0.04a
	CS500	0.45±0.04a	4.53±0.32b	20.73±2.72ab	0.36±0.07a	0.41±0.04a