不同肥力棕壤玉米根茬和茎叶残体碳氮的固定特征

doi:10.3864/j.issn.0578-1752.2022.23.008

摘要/Abstract

摘要： 目的秸秆还田是增加土壤碳固定和改善土壤养分状况的重要措施之一。研究玉米不同部位残体碳、氮在土壤中的固定特征，明确秸秆还田的土壤增碳培肥机制。方法以沈阳农业大学棕壤长期定位试验站为平台，采集不施肥和有机肥配施化肥处理的土壤分别作为低肥力（LF）和高肥力（HF）土壤，并分别与¹³C和¹⁵N双标记的玉米茎叶（S）、玉米根茬（R）混合，在25℃条件下进行室内培养试验。试验于第1、30、60、180和360 天取样并测定土壤总有机碳（SOC）、全氮（TN）含量及其同位素丰度，分析玉米不同部位残体碳、氮在不同肥力水平土壤中的固定特征。结果添加玉米残体显著提高土壤SOC，一年后仍能提高14.0%。添加玉米残体后，土壤系统中有一小部分氮素可能以反硝化方式流失，且外源玉米残体氮和土壤原有老氮均有损失。与添加根茬相比，添加茎叶更有利于外源新碳、氮的增加，而且具有更强的激发老碳、氮分解/损失的效应，不利于土壤老碳、氮的固持；根茬残体则更趋向于被分解，使土壤老碳、氮得到相对的保护和固定。外源残体碳虽然在低肥力土壤中的固定较少，但是对低肥力土壤碳库的提升具有更大的贡献。添加残体后低肥力土壤的C/N和¹³C/¹⁵N（代表土壤中来自于外源残体的C/N）显著高于高肥力土壤。但本研究结果表明¹³C/¹⁵N并不是限制低肥力土壤中残体分解和固定的主要因素，其主要原因可能在于底物长期选择条件下的特异性土著土壤微生物群落较为稳定，对于外源有机质加入的干扰具有抵抗力造成的。结论土壤中添加玉米不同部位残体均可显著提高土壤碳、氮水平，但其内在的残体新碳/氮和土壤老碳/氮的固定策略相异。低肥力土壤较高肥力土壤对外源碳的固定少，其对不同部位残体的固定在本研究中并不受到来自于外源残留残体C/N的影响。

关键词: 玉米残体, 土壤肥力水平, 土壤碳氮固定, 稳定同位素标记

Abstract:

【Objective】 Straw returning to the field is one of important measures to increase soil carbon (C) fixation and to improve soil nutrient status. Studying the C and nitrogen (N) fixation characteristics of different parts of maize residues in the soil is of great significance for clarifying the C and N sequestration mechanism under straw returning. 【Method】 This study was based on the long-term experiment station of Shenyang Agricultural University. The soils treated with no fertilization and organic fertilizer combined with chemical fertilizers were collected as low fertility (LF) and high fertility (HF) soils, respectively, and combined with ¹³C and ¹⁵N double-labeled maize residues. Maize stalk and leaf part (S) as well as root part (R) are mixed with collected soils, respectively, and incubated at 25℃. In the experiment, the samples were taken on the 1^st, 30^th, 60^th, 180^th and 360^th days to determine the total organic C (SOC), total N (TN) content, and their isotopic abundances, and to analyze C and N fixing dynamics of different parts of maize residues in the soil with different fertility levels..【Result】 Adding maize residues significantly increased soil SOC, and could still increase by 14.0% after one year. After adding maize residues, a small part of N in the soil system might be lost by denitrification, and both added N deriving from maize residues and native N in soil were contributed in the lost. Compared with the addition of root residues, the addition of straw residues was more conducive to retaining the added residual C and N, which had a stronger effect on stimulating the local C decomposition and N loss. In contrast, the root residues tended to be decomposed, while the native soil C and N were relatively protected. Although the fixation of added residual C in low-fertility soil was higher than that in high-fertility soil, the fixed added residual C presented a greater contribution to the promotion of C pool in the low-fertility soil. Under the treatment of residues addition, C/N and ¹³C/¹⁵N (representing residue-deriving C/N in the soil) in low-fertility soil were significantly higher than those in high-fertility soil. However, the results showed that ¹³C/¹⁵N was not the main factor limiting the decomposition and fixation of residues in low-fertility soil, which might be related to the distinctive soil microbial community favoring of utilizing the specific substrate under the long-term substrate selection..【Conclusion】 Adding maize residues from different parts of the soil could significantly increase soil carbon and nitrogen levels, but the immobilization strategies of new carbon/nitrogen in the residues and soil old carbon/nitrogen were different. The low-fertility soil had higher capacity to fix exogenous carbon and less fertility, and their fixation of residues in different parts was not affected by the limitation of C/N from exogenous residues in this study.

Key words: maize residue, soil fertility level, soil organic carbon and total nitrogen fixation, stable isotope labeling

李佳燕,孙良杰,马南,王丰,汪景宽. 不同肥力棕壤玉米根茬和茎叶残体碳氮的固定特征[J]. 中国农业科学, 2022, 55(23): 4664-4677.

LI JiaYan,SUN LiangJie,MA Nan,WANG Feng,WANG JingKuan. Carbon and Nitrogen Fixation Characteristics of Maize Root and Straw Residues in Brown Soil Under High and Low Fertility[J]. Scientia Agricultura Sinica, 2022, 55(23): 4664-4677.

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处理 Treatment	有机碳 Soil organic carbon (g·kg^-1)	全氮 Soil total nitrogen (g·kg^-1)	碳氮比 C/N	δ¹³C值 δ¹³C value (‰)	δ¹⁵N 值 δ¹⁵N value (‰)	pH
高肥土壤HF High-fertility soil, HF	15.22±0.17A	1.71±0.03A	8.90±0.11	-19.67±0.09A	8.67±0.57A	5.91±0.05B
低肥土壤LF Low-fertility soil, LF	11.72±0.01B	1.27±0.01B	9.23±0.09	-18.16±0.14B	8.39±0.35B	6.34±0.02A

处理 Treatment	有机碳 Soil organic carbon (g·kg^-1)	全氮 Soil total nitrogen (g·kg^-1)	碳氮比 C/N ratio	δ¹³C值 δ¹³C value (‰)	δ¹⁵N 值 δ¹⁵N value (‰)
根茬 Root, R	444.46	6.14	72.35	298.47	11003.51
茎叶 Stalk and leaf, S	407.54	8.49	48.00	386.06	11005.59

处理 Treatment	土壤总有机碳 Soil organic carbon (g·kg^-1)
处理 Treatment	1 d	30 d	60 d	180 d	360 d
HF	15.22±0.17aC	15.10±0.17aB	14.78±0.17bB	14.73±0.09bB	14.37±0.07bB
LF	11.72±0.01aD	11.05±0.19bC	10.99±0.26bC	10.75±0.23bD	10.48±0.04bD
HF+R	23.53±0.13aA	18.55±0.12bA	17.58±0.16cA	16.34±0.33dA	15.85±0.41dA
LF+R	20.70±0.28aB	15.47±0.24bB	15.26±0.20bB	13.36±0.20cC	12.33±0.21dC
HF+S	22.55±0.37aA	17.96±0.25bA	17.45±0.10bcA	16.59±0.31cdA	16.05±0.41dA
LF+S	19.56±0.30aB	15.63±0.21bB	14.95±0.14bB	12.71±0.29cC	12.85±0.23cC

处理 Treatment	土壤全氮 Soil total nitrogen (g·kg^-1)
处理 Treatment	1 d	30 d	60 d	180 d	360 d
HF	1.71±0.03aB	1.63±0.03abC	1.62±0.03abB	1.59±0.01bB	1.62±0.03abB
LF	1.27±0.01bD	1.37±0.02aD	1.27±0.04bC	1.31±0.01abC	1.20±0.01cC
HF+R	1.83±0.02aA	1.82±0.01aB	1.80±0.03abA	1.69±0.01cA	1.75±0.02bcA
LF+R	1.36±0.02abC	1.41±0.02aD	1.29±0.05bC	1.31±0.03abC	1.25±0.02bC
HF+S	1.87±0.02aA	1.89±0.01aA	1.73±0.04bA	1.68±0.01bcA	1.60±0.03cB
LF+S	1.39±0.01aC	1.37±0.03aD	1.33±0.02abC	1.25±0.03bcC	1.26±0.01bcC

处理 Treatment	土壤碳氮比 C/N
处理 Treatment	1 d	30 d	60 d	180 d	360 d
HF	9.23±0.11abC	9.45±0.12aC	9.15±0.21abD	9.29±0.08abC	8.87±0.14bC
LF	9.25±0.09aC	8.07±0.27bD	8.66±0.29abD	8.22±0.16bD	8.73±0.12abC
HF+R	12.89±0.13aB	10.20±0.12bB	9.75±0.17bcB	9.65±0.20cdB	9.07±0.14dB
LF+R	15.22±0.07aA	11.00±0.31bA	11.87±0.39bA	10.23±0.09cA	9.84±0.29cA
HF+S	12.08±0.09aB	9.48±0.13bC	10.09±0.30bC	9.85±0.14cB	10.01±0.09cB
LF+S	14.09±0.12aB	11.41±0.44bB	11.24±0.26cB	10.15±0.43dB	10.18±0.27dB