江淮地区苜蓿短期连作对后作高丹草生长及土壤微环境的影响

doi:10.11686/cyxb2023424

摘要/Abstract

摘要：

为了探究苜蓿连作对后作高丹草产量品质及土壤健康状况的影响，分别以撂荒地正茬种植高丹草（yr₀）为对照、苜蓿1年龄（yr₁）、3年龄（yr₃）、5年龄（yr₅）后轮作高丹草3种处理方式为研究对象，采用传统方法，试剂盒及高通量测序方法检测了轮作后高丹草的生长状况及产量差异、轮作后土壤化学性质、酶活性及微生物结构组成的变化，阐明了苜蓿短期连作对后作高丹草生长及产量的影响，从土壤微环境的角度评价了苜蓿连作对后作高丹草的影响。研究结果显示，与正茬高丹草相比（yr₀），苜蓿轮作高丹草促进了后茬高丹草叶片数量及产量的增加，3年龄苜蓿（yr₃）轮作高丹草与正茬（yr₀）高丹草相比，后作高丹草产量增加了63.23%（P<0.05），粗蛋白及中性洗涤纤维含量也相应提高；后作高丹草土壤pH值随着前作苜蓿年龄的增加持续降低，土壤有机质、全氮含量持续增加，5年龄（yr₅）苜蓿轮作高丹草后有机质含量比正茬高丹草（yr₀）土壤增加了78.25%、全氮含量与正茬高丹草（yr₀）土壤相比增加了34.88%（P<0.05）；蔗糖酶活性在1年龄（yr₁）苜蓿轮茬高丹草土壤中最高，脲酶在3年龄（yr₃）后茬土壤中活性最高；在苜蓿轮作高丹草根际土壤中门水平优势细菌群落为变形菌、拟杆菌和厚壁菌，优势真菌群落为子囊菌、担子菌和聚合菌；前茬苜蓿3年龄（yr₃）时轮作高丹草土壤细菌丰富度及多样性指数均为最高（P<0.05）；前茬苜蓿5年龄（yr₅）时轮作高丹草土壤真菌Shannon指数最高（P<0.05）；苜蓿轮作高丹草土壤中的绿弯菌、浮霉菌、放线菌随着前作苜蓿年龄的增加呈先增加随后降低的变化趋势；相关性分析表明，土壤pH、有机质含量与土壤微生物结构关系紧密，苜蓿-高丹草轮作处理下，前作苜蓿分泌物和残体降解物进入土壤生态系统，加速特异微生物区系重构，缓解了土壤酸化及调整营养物质循环，具有改良土壤的作用，能够促产增效，但是种植年限不宜过久，种植年限超过3年后，土壤中的营养成分会打破平衡。该结果为江淮地区苜蓿连作障碍的生态修复，构建饲草可持续高效生产栽培关键技术体系提供了理论依据。

关键词: 苜蓿-高丹草轮作, 高丹草生长, 微生物群落结构, 土壤环境

Abstract:

This study investigated the effects of a previous alfalfa （Medicago sativa） crop on the performance of subsequent crops of sorghum-sudan grass hybrid （Sorghum bicolor×Sorghum sudanense）. We utilized abandoned land as a control treatment （yr₀）， compared with adjacent land planted in alfalfa for 1 year （yr₁）， 3 years （yr₃）， or 5 years （yr₅）， to determine the effect of previous length of time under alfalfa cropping on the yield， quality， and soil health of a subsequent sorghum-sudan grass hybrid crop. The research methodology combined traditional agronomy methods to measure sorghum-sudan grass hybrid crop growth, yield differences and soil chemical properties, the kit methods to measure enzyme activities and with high-throughput sequencing methods to detect changes in soil microbial community composition under the various alfalfa rotations. The results showed that， compared with yr₀， previous planting in alfalfa improved sorghum-sudan grass hybrid crop vigor and promoted an increase in the number of leaves and yield of the following crop. The yr₃ treatment was optimal， with an increase in yield of 63.23% （P<0.05） compared to the control （yr₀）. The crude protein and neutral detergent fiber contents of the sorghum-sudan grass hybrid crop were also increased by previous planting in alfalfa. With increasing length of time previously planted in alfalfa， the soil pH of the subsequent sorghum-sudan grass hybrid crop decreased， the soil organic matter and total nitrogen contents increased， and soil enzyme activities were generally increased. Specifically， soil organic matter of yr₅ sorghum-sudan grass hybrid crops was increased by 78.25% and soil total nitrogen was increased by 34.88% compared to yr₀ （P<0.05）. The soil sucrase activity of the subsequent sorghum-sudan grass hybrid was highest in the yr₁ treatment， while the urease activity was highest in yr₃. At the phylum level， the dominant bacterial communities in the rhizosphere soil of subsequent sorghum-sudan grass hybrid crop were Proteobacteria， Bacteroidetes， Firmicutes， and the dominant fungal communities were Ascomycota， Basidiomycota and Glomeromycota. The soil bacterial richness and diversity index was highest （P<0.05） in yr₃， while the Shannon index of soil fungi was highest （P<0.05） in yr₅. The abundance of Chloroflexi， Planctomycetes and Actinobacteria showed a trend of initial increase and then decrease across the time series yr₀ to yr₅. Correlation analysis showed that soil pH， organic matter content， and soil microbial community structure are closely related. For treatments yr₁， yr₃ and yr₅， the secretion and residual degradation products of the previous alfalfa crop enter the soil ecosystem， accelerating the formation of specific microbial communities， alleviating soil acidification and adjusting nutrient cycling. These changes improve soil quality， reduce the intensity of sorghum-sudan grass hybrid stress， and promote yield of the subsequent crop. However， the time planted in alfalfa should not be too long； after more than three years planted in alfalfa， there can be a reduction in the benefit to the following crop. These results provide research data for the Jianghuai area on ecological restoration using alfalfa cropping and show that a three-year planting of alfalfa is beneficial to the subsequent crop.

Key words: rotation of alfalfa and sorghum-sudan grass hybrid, growth of sorghum-sudan grass hybrid, microbial community structure, soil environment

李争艳, 徐智明, 李岩, 李杨. 江淮地区苜蓿短期连作对后作高丹草生长及土壤微环境的影响[J]. 草业学报, 2024, 33(9): 155-168.

Zheng-yan LI, Zhi-ming XU, Yan LI, Yang LI. Effects of short-term continuous cropping of alfalfa on the growth and soil microenvironment of subsequent sorghum-sudan grass hybrid crops in the Jianghuai area[J]. Acta Prataculturae Sinica, 2024, 33(9): 155-168.

图/表 8

表1 不同处理详细描述

Table 1 Description of each treatment

处理 Treatments	缩写 Abbreviation	处理描述 Description for treatments
正茬高丹草Newly plant sorghum-sudan grass hybrid	yr₀	2021年4月撂荒新地第一年种植高丹草，作为对照处理Planting sorghum-sudan grass hybrid in the first year of abandoned land as a control treatment in April 2021
1年龄苜蓿轮作高丹草1-year-old alfalfa rotated with sorghum-sudan grass hybrid	yr₁	2020年4月种植苜蓿，前作苜蓿种植1年后于2021年4月轮作高丹草Alfalfa was planted in April 2020， and rotating sorghum-sudan grass hybrid the second year in April 2021
3年龄苜蓿轮作高丹草3-year-old alfalfa rotated with sorghum-sudan grass hybrid	yr₃	2018年4月种植苜蓿，前作苜蓿种植3年后于2021年4月轮作高丹草Alfalfa was planted in April 2018， and rotating sorghum-sudan grass hybrid the fourth year in April 2021
5年龄苜蓿轮作高丹草5-year-old alfalfa rotated with sorghum-sudan grass hybrid	yr₅	2016年4月种植苜蓿，前作苜蓿种植5年后于2021年4月轮作高丹草Alfalfa was planted in April 2016， and rotating sorghum-sudan grass hybrid the sixth year in April 2021

表2 不同轮作处理对后作高丹草营养成分及产量的影响

Table 2 Effects of different rotation treatments on the nutrient composition and yield of sorghum-sudan grass hybrid

产量、品质及生长指标 Yield， quality and growth indexes	处理Treatments
产量、品质及生长指标 Yield， quality and growth indexes	yr₀	yr₁	yr₃	yr₅
酸性洗涤纤维Acid detergent fiber （g·kg^-1 DM）	32.49±0.87a	34.24±1.95a	33.45±0.89a	32.77±2.16a
中性洗涤纤维Neutral detergent fiber （g·kg^-1 DM）	55.18±0.83ab	57.31±1.72a	58.01±2.02a	53.22±1.27b
粗蛋白Crude protein （g·kg^-1 DM）	8.00±0.51b	8.90±0.39ab	9.21±0.18a	8.34±0.40b
粗灰分Crude ash （%）	6.24±0.98a	7.26±1.25a	6.88±0.41a	6.16±0.02a
产量Yield （t·hm^-2）	94.17±12.85b	149.34±36.95a	153.70±20.17a	136.49±11.86ab
株高Plant height （cm）	295.51±10.19a	294.77±5.33a	296.06±3.43a	287.97±0.68a
茎粗Stem diameter （cm）	1.64±0.14a	1.59±0.03a	1.65±0.11a	1.50±0.04a
叶数Leaf number （Pieces）	21.00±1.00b	20.33±1.16b	23.33±0.58a	21.00±1.00b

表3 不同轮作处理下土壤化学性质变化

Table 3 Changes of chemical characteristics of soil in different rotation treatments

化学性质 Chemical properties	处理Treatments
化学性质 Chemical properties	yr₀	yr₁	yr₃	yr₅
pH	8.15±0.06a	8.08±0.03a	7.91±0.05b	7.88±0.05b
有机质Organic matter （g·kg^-1）	12.83±1.35c	18.33±0.91b	19.90±1.71ab	22.87±2.11a
全氮Total nitrogen （g·kg^-1）	1.29±0.07b	1.40±0.11b	1.29±0.15b	1.74±0.23a
有效磷Available phosphorus （mg·kg^-1）	7.78±0.49a	7.35±0.07a	5.83±0.24a	6.40±0.29a
速效钾Available potassium （mg·kg^-1）	105.87±9.86c	238.40±17.49b	322.03±8.52a	257.13±6.62b

表4 不同轮作处理对土壤酶活性的影响

Table 4 Effects of different rotation treatments on soil enzyme activities

土壤酶活性 Soil enzymes activity	处理Treatments
土壤酶活性 Soil enzymes activity	yr₀	yr₁	yr₃	yr₅
碱性磷酸酶Alkaline phosphatase （μmol phenol·g^-1·24 h^-1）	13.00±3.80a	15.12±1.30a	12.93±9.20a	12.47±4.67a
过氧化氢酶Catalase （μmol H₂O₂·g^-1·24 h^-1）	176.76±7.40a	174.77±1.75a	178.25±1.09a	177.43±4.33a
蔗糖酶Sucrase （mg C₆H₁₂O₆·g^-1·24 h^-1）	28.74±2.34c	46.53±3.09a	39.65±5.46b	43.25±2.17ab
脲酶Urease （μg NH₃-N·g^-1·24 h^-1）	2268.89±215.18a	1287.04±91.53b	2298.37±424.21a	1024.45±177.39b

图1 不同轮作处理的土壤样品细菌、真菌组成A：不同年龄苜蓿后作高丹草根部土壤中细菌平均相对丰度；B：不同年龄苜蓿后作高丹草根部土壤中真菌平均相对丰度。“Others”是所有相对丰度较低稀有细菌、真菌门的总和。 A： Average relative abundance of bacterial phyla in different soil samples of the subsequent sorghum-sudan grass hybrid rotated with alfalfa； B： Average relative abundance of fungal phyla in different soil samples of the subsequent sorghum-sudan grass hybrid rotated with alfalfa. “Others” are the sum of all rare bacterial fungal phyla with low relative abundances.

Fig.1 Soil bacteria and fungal community for different rotation treatments

图2 不同轮作处理对土壤细菌（A）、真菌（B）多样性的影响采用t检验评估OTU水平各样本的细菌、真菌多样性。Student’s t-test for estimator were used to estimate the bacterial and fungal diversity of each sample on OTU level. *： 0.01<P≤0.05； **： 0.001<P≤0.01； ***： P≤0.001. 下同The same below.

Fig.2 Soil bacteria （A） and fungal （B） diversity of different rotation treatments

图3 不同处理细菌（A）、真菌（B）相对丰度变化采用单因素方差分析（ANOVA）和Kruskal-Wallis H检验进行多重比较。One-way analysis of variance （ANOVA） and Kruskal-Wallis H test were used for multiple comparisons.

Fig.3 Different bacteria （A） and fungal （B） abundance based on phylum level

图4 细菌、真菌群落组成与土壤化学性质的冗余分析图中不同颜色的点表示不同年龄前茬苜蓿轮作高丹草的土壤样本组；图中微生物物种以蓝色箭头表示；箭头为数量型环境指标，箭头长短表明该环境指标对微生物物种的影响程度；环境因子箭头间的夹角代表正、负相关性，锐角表示正相关，钝角表示负相关，直角为不相关。The dots with different colors in the Figure represent soil samples of the subsequent sorghum-sudan grass hybrid rotated with alfalfa； The microbial species in the Figure are represented by blue arrows； The arrow represents a quantitative environmental indicator， and the length of the arrow indicates the degree of impact of the environmental indicator on microbial species； The angle between the arrows of environmental factors represents positive and negative correlation， acute angle represents positive correlation， obtuse angle represents negative correlation， and right angle represents uncorrelated.

Fig.4 Redundancy analyses （RDA） between bacterial/fungal community composition and soil chemical properties

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