引用本文
杨封科, 何宝林, 张国平, 张立功, 高应平. 膜下秸秆还田添加腐解剂对旱地土壤碳氮积累及土壤肥力性状的影响. 草业学报, 2019,28(9): 67-76
YANG Feng-ke, HE Bao-lin, ZHANG Guo-ping, ZHANG Li-gong, GAO Ying-ping. Effects of straw incorporation with decomposer and film mulched ridge furrow tillage on soil carbon and nitrogen accumulation and soil fertility characters in dryland, China. Acta Prataculturae Sinica,2019,28(9): 67-76  
Doi:10.11686/cyxb2019186
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膜下秸秆还田添加腐解剂对旱地土壤碳氮积累及土壤肥力性状的影响
杨封科1,2,*, 何宝林1,2, 张国平1,2, 张立功3, 高应平3
1.甘肃省旱作区水资源高效利用重点实验室,甘肃 兰州 730070
2.甘肃省农业科学院旱地农业研究所,甘肃 兰州 730070
3.甘肃省庄浪县农技推广中心,甘肃 庄浪 744600
*通信作者: E-mail: yang_fk@163.com

作者简介:杨封科(1964-),男,甘肃合水人,研究员,博士。E-mail: yang_fk@163.com

收稿日期: 2019-03-14
基金项目:国家自然科学基金地区基金(31560137)和甘肃省科技支撑计划项目(1204NKCA108)资助
摘要

探索全膜双垄膜下秸秆还田添加腐解剂对旱地耕层土壤碳氮积累及土壤肥力性状的影响。2015-2017年在甘肃省农业科学院庄浪试验站,实施了以常规种植(CP)、常规种植+秸秆还田(CPS)、常规种植+秸秆还田+腐解剂(CPSD)、全膜双垄种植(FMRF)、全膜双垄种植+秸秆还田(FMRFS)和全膜双垄种植+秸秆还田+腐解剂(FMRFSD)为处理的田间定位试验。测定了耕层0~30 cm土壤有机质(SOM)、土壤全氮(TN)、全磷(TP)、全钾(TK)和速效氮(AN)、速效磷(AP)、速效钾(AK)、土壤容重(BD)和土壤pH,计算了耕层秸秆固存率(CSE)和碳氮积累量。结果表明,FMRFSD通过改善水热环境协同秸秆微生物腐解剂生产增效作用,加速了还田秸秆腐解与养分释放,产生的有机物抵消了土壤有机氮矿化损失,释放的养分补充了作物生长对土壤养分的消耗;改善后的水热肥条件又促进作物旺盛生长,使更多的有机物(落叶、根茬)回归土壤,从而显著促进了耕层SOC和TN的积累、提高了土壤TN、TP、TK和AN、AP、AK的含量,尤其是显著提高AP和AK的含量( P<0.05)。与CP比,FMRFSD 3年累计固存了41.17%的秸秆碳, 耕层年均增加SOC和TN贮量0.79 mg C·hm-2和0.04 mg N·hm-2;使耕层TN、TP、TK和AN、AP、AK 含量提高了0.05、0.03、3.05 g·kg-1和10.80、8.90、101.50 mg·kg-1,相应地增加了6.87%、6.94%、15.28%、10.24%、56.69%、55.34%。同时,FMRFSD使土壤BD和pH值分别降低了3.9%和0.2%。土壤碳氮贮量、氮磷钾养分含量的增加以及土壤BD和pH 值的降低,增加了土壤供肥能力、改善了土壤结构和性状,从而显著提高了肥力。因此,FMRFSD是适合当地的最有效的农田碳氮库土壤肥力管理模式。

关键词: 秸秆还田; 全膜双垄耕作; 腐解剂; 碳氮积累; 土壤肥力性状
Effects of straw incorporation with decomposer and film mulched ridge furrow tillage on soil carbon and nitrogen accumulation and soil fertility characters in dryland, China
YANG Feng-ke1,2,*, HE Bao-lin1,2, ZHANG Guo-ping1,2, ZHANG Li-gong3, GAO Ying-ping3
1.Key Laboratory of High Water Utilization on Dryland of Gansu Province, Lanzhou 730070, China
2.Institute of Dryland Farming, Gansu Academy of Agricultural Sciences, Lanzhou 730070, China
3.Agricultural Technology Promotion Center of Zhuanglang County, Zhuanglang 744600, China
*Corresponding author: E-mail: yang_fk@163.com
Abstract

Full plastic film mulched ridge-furrow tillage (FMRF) and straw incorporation (S) are two effective strategies for managing soil fertility in semiarid areas. However, the effect of these two practices in combination (FMRFS) and the key mechanisms by which FMRFS positively modifies soil fertility characteristics, especially following application of cellulose-decomposing microbial cultures has not been well studied. To address this lack of information, a three-year field experiment with six treatments [conventional planting (CP), conventional planting with straw incorporation (CPS), conventional planting with straw incorporation plus decomposer (CPSD), FMRF, FMRFS, and full plastic film mulched ridge-furrow tillage with straw incorporation (FMRFSD)], and using a randomized block design with three replications, was conducted from 2015-2017. Soil organic matter (SOM), soil total and available nitrogen, phosphorus and potassium (TN, TP, TK and AN, AP, AK), soil bulk density (BD) and pH values of the 0-30 cm soil profile were examined. Soil organic carbon (SOC) content, SOC and TN accumulation as well as straw sequestration efficiency (CSE) were calculated. Results indicated that FMRFSD considerably accelerated SOC and TN accumulation in topsoil, significantly ( P<0.05) increased the content of SOC, total and available N, P and K, especially the AP and AK content, in 0-30 cm soil profile, via enhanced straw decomposition and nutrient release that more than offset the loss of SOC by mineralization and replenished soil nutrients consumed by crop growth uptake, simultaneously enhancing crop growth and vigor, resulting in increased organic matter (litter and roots, etc.) returned to the soil to complement the soil nutrient reservoir through the synergistic effects of modified soil hydrothermal conditions and the added cellulose-decomposing microbial culture. Measurement results showed that, compared to CP, FMRFSD cumulatively sequestrated 41.17% of the straw carbon added over 3 years, which led to SOC and TN accumulation being increased by 0.79 mg C·ha-1 and 0.04 mg N·ha-1,respectively. This in turn increased the content of TN, TP and TK by 0.05, 0.03 and 3.05 g·kg-1, respectively, and the contents of AN, AP, and AK by 10.80, 8.90 and 101.50 mg·kg-1, respectively. These increases corresponded to elevations, respectively, of 6.87%, 6.94%, 15.28%, 10.24%, 56.69%, 55.34%. In addition, the soil BD was lowered by 3.9%, and the soil pH by 0.004 units. With the increase of soil carbon and nitrogen storage, nitrogen, phosphorus and potassium nutrient content and the decrease of soil BD and pH values, the ability of soil to supply plant nutrients was increased, the soil structure and properties were improved, and thus the fertility was significantly improved. Therefore, FMRFSD is a highly effective management regime for improving soil carbon-nitrogen status and fertility characters in dryland.

Keyword: straw incorporation; full plastic film mulched ridge-furrow tillage; decomposer; carbon and nitrogen accumulation; soil fertility character

秸秆还田(straw incorporation, S)作为土壤碳氮(soil organic carbon, SOC; total nitrogen, TN)和土壤肥力管理的重要措施之一越来越受到重视[1, 2]。秸秆还田同时也是秸秆处置的有效途径之一[3, 4]。以往秸秆焚烧或移除他用不仅减少了归还土壤有机物质的数量, 降低了土壤肥力, 还导致了土壤退化与环境污染[5]。而长期秸秆还田增加了土壤有机质[6, 7], 提高了土壤碳氮含量[8, 9, 10]和稳定性[11, 12], 增加了耕层土壤养分含量[13, 14, 15, 16], 改善土壤理化性状[17, 18, 19]、质量[20]和肥力[21, 22], 增加了作物产量[19, 23]。即使短期秸秆还田也有提高土壤肥力的潜势[24]。但低秸秆腐解率[18]限制了秸秆还田在黄土高原地区的应用[19]。因此, 探索更加高效的秸秆还田土壤肥力管理方法至关重要。

还田秸秆腐解与养分释放是秸秆还田培肥土壤的关键[3]。作物秸秆养分含量中以玉米(Zea mays)氮和磷养分含量最高[16], 但在自然状态下, 特别是北方旱区春秋低温环境下降解的速度较慢[3, 18], 地表覆盖还田则更慢[2], 制约了养分的释放。将秸秆粉碎后与土壤混合, 通过改善土壤水热条件促进秸秆腐解是新的尝试[3], 在此基础上添加秸秆纤维素分解菌剂(即腐解剂)促进作物秸秆腐解、缩短腐解转化时间、增加其养分释放量也是促腐的新手段[14, 25, 26, 27]。配施秸秆腐熟剂有利于有益微生物繁殖, 增加微生物多样性和活性, 降低秸秆C/N, 加速秸秆腐熟[28]。秸秆腐解也受还田方式、耕作方式、地点等交互作用的影响。秸秆还田与免耕深松、旋耕结合也有利于秸秆腐解与养分释放[3, 29, 30]。秸秆还田还可改善土壤结构、降低土壤酸度[3, 14], 而改善土壤相关性状。秸秆还田释放的氮、磷、钾营养元素可替代化肥而减少化肥使用量[1, 16, 28]。

秸秆还田、全膜双垄沟播(full plastic film mulched ridge-furrow tillage, FMRF)是旱地农业生产实践上土壤水肥调控的有效措施, 二者耦合(full plastic film mulched ridge-furrow tillage with straw incorporation, FMRFS)通过膜秸双覆盖在改善土壤水热环境的增效作用, 加速了还田秸秆腐解与养分释放, 从而有效提高了旱地土壤有机质(soil organic matter, SOM)和养分含量, 是一种更加高效的旱地土壤肥力管理增效模式[4, 14, 31]。但是, 由于秸秆分解及养分释放率仍然很低, 这种模式仍不足以满足获得可持续产量所需的土壤肥力水平[30]。如何进一步促进膜下还田秸秆腐解和养分释放, 更高效地提升土壤肥力水平是需要深入研究的科学问题。

土壤有机碳(SOC)是影响土壤肥力的决定性因子, 是土壤肥力和质量管理的核心[10, 32]。土壤有机碳和全氮(TN)积累与土壤氮、磷、钾等营养元素含量正相关[32]。秸秆还田向土壤添加了大量的有机碳源、添加腐解剂促进了秸秆腐解与养分释放, 对SOC和TN积累与存贮、转化和循环, 维持和提高土壤肥力等方面均起着极其重要的作用。但在FMRFS技术中添加腐解剂的研究还鲜有报道。基于此, 本研究将设置3年田间定位试验, 重点探讨全膜双垄种植膜下秸秆还田添加腐解剂对土壤SOC和TN积累的影响, 以及对土壤肥力性状指标N、P、K养分含量以及土壤容重(soil bulk density, BD)和pH的响应, 从而实现旱地全膜双垄膜下秸秆还田培肥土壤的创新模式, 为更新或提升旱地全膜双垄沟播集雨种植技术提供支撑。

1 材料与方法
1.1 研究区概况

试验设在甘肃省农业科学院庄浪试验站南坪试验基地(106° 05'28″ E, 35° 10'30″ N)。代表区域具有黄土丘陵沟壑的典型地貌特征, 也是全膜双垄沟播集雨技术与秸秆还田的重点推广区域之一。海拔1765 m, 多年平均气温7.9 ℃, 无霜期145 d, ≥ 0 ℃积温3280.6 ℃, ≥ 10 ℃活动积温2640.4 ℃, 年均降水量510.4 mm, 主要集中在7-9月。平均蒸发量为1289.1 mm, 平均干燥度1.55, 是典型的干旱半干旱气候类型。研究期2015-2017年, 玉米生育期(4-9月)年降水量和蒸发量分别为349.9、291.9、351.4 mm和 1305、1310、1290 mm, 与2000-2016年玉米生育期平均降水391 mm比, 都属于干旱年。试验地为耕作黄绵土, 基础土壤性状见表1。

表1 试验地0~20 cm土层基础理化性状 Table 1 Basal physicochemical characteristics of the 0-20 cm soil layers at the experimental fields
1.2 研究方法

1.2.1 试验设计 本研究为3年定位试验, 以先玉335玉米种为指示作物, 设6个处理(表2)。共18个小区, 随机区组设计, 3次重复。小区面积5 m× 8 m=40 m2, 玉米种植密度为 55000 株· hm-2, 株行距为55 cm× 33 cm。施P2O5 90 kg· hm-2(过磷酸钙含P2O5 12%)、N 540 kg· hm-2(尿素含N 46%)。磷肥全做底肥, N肥1/3作底肥, 2/3于玉米拔节期(出苗后55~60 d)在玉米种植行间追施, 施深10 cm。每年玉米收获后, 常规种植小区1、2、3按常规进行田间耕作, 不再加秸秆和腐解剂; 4、5、6小区清除残膜, 于次年玉米播种前2~3周重建, 不另加秸秆和腐解剂。3年的播种期为4月15-18日, 收获期为9月27-10月2日。

表2 试验处理描述 Table 2 Treatments description

1.2.2 采样与试验分析 采用“ S” 型5点取样方法, 于2017年9月底玉米收获后, 用直径为5.5 cm 的土钻, 按30 cm的取样深度, 每小区取5个样, 混合成一个1 kg的混合样。将土样去除植物根系和石块, 充分混匀带回实验室, 分别用重铬酸钾氧化法、凯氏定氮法、碱解扩散法、氢氧化钠熔融-钼锑抗比色法、碳酸氢钠-钼锑抗比色法和乙酸铵浸提-火焰光度计法测定土壤有机质、土壤全氮含量、碱解氮、全磷、速效磷和速效钾含量[23]。用环刀法[33]和酸度计法[23]测定土壤容重和pH。

1.2.3 参数计算 土壤有机碳(SOC)含量以及SOC和TN贮量, 参照Wang等[6]的方法, 按下式计算:

SOC=SOM× 0.58 (1)

D=EC× BD× H× 10 (2)

式中:SOC为土壤有机碳含量(g· kg-1); SOM为土壤有机质(g· kg-1); 0.58为SOM转化为SOC的转化因子; D为SOC和TN的贮量(mg C· hm-2, mg N· hm-2); EC为碳氮元素含量(g· kg-1); BD为土壤容重(g· cm-3); H为土壤深度(m), 本研究取0.3 m(30 cm耕层深度); 10是单位调整常数。

秸秆碳固存效率(straw-C sequestration efficiency, CSE)[6]:

CSE= SOC+S-SOC-S∑SC(3)

式中:SOC+S和SOC-S分别是有无秸秆还田处理的SOC贮量(mg C· hm-2); ∑ SC是试验期间累计秸秆碳输入(mg C· hm-2), 依据本试验设计, 研究期间总投入的秸秆碳为3.62 mg C· hm-2。

1.3 数据处理

采用Microsoft Excel 2013软件对数据进行基本计算处理, 用IBM SPSS 19 (IBM Institute Inc.USA)进行统计分析。采用单因素(One-way ANOVA)和LSD法对不同处理措施组合数据进行差异显著性检验(α =0.05)。用SigmaPlot 14 (Systat Software Inc.)作图。表中数据为平均值± 标准差。

2 结果与分析
2.1 不同处理对土壤有机质、有机碳、全氮含量及碳氮积累的影响

秸秆还田与不同耕作方式结合、不论添加腐解剂与否, 都显著地提高了0~30 cm 耕层土壤有机碳(SOC)和全氮(TN)的含量(P< 0.05)(表3)。全膜双垄膜下秸秆还田处理(FMRFSD和FMRFS)效应显著优于常规耕种加秸秆还田处理(CPS和CPSD)和全膜双垄耕种(FMRF)本身, 都与常规耕种(CP)差异显著(P< 0.05), 表现为FMRFSD> FMRFS> FMRF> CPSD> CPS> CP。测定结果表明, 与CP相比, 各处理使0~30 cm 耕层SOC和TN含量分别提高了0.34~0.98 g· kg-1和0.02~0.05 g· kg-1, 相应地增加了3.70%~10.70%和1.90%~6.87%。其中, FMRFSD和 FMRFS处理使耕层SOC和TN的含量比CP分别提高了0.87~0.98 g· kg-1和0.04~0.05 g· kg-1, 相应地增加了9.54%~10.70%和5.73%~6.87%; 比FMRF处理分别提高了0.18~0.28 g· kg-1和 0.01~0.02 g· kg-1, 相应地增加1.80%~2.95%和1.15%~2.29%; 比CPSD和CPS处理分别平均提高了0.45、0.03 g· kg-1, 相应地增加了4.69%和3.35%。

表3 不同处理组合对0~30 cm 耕层土壤有机碳和全氮的影响 Table 3 Effect of different treatments on soil organic carbon (SOC) and total nitrogen (TN) of 0-30 cm topsoil

秸秆还田与不同耕作方式结合, 显著提高了秸秆碳的耕层固存效率(CSE)促进了SOC和TN的根层积累(表3)。3年累计, 与CP比试验各处理0~30 cm土层固定了5.15%~41.17% 的秸秆碳, 以 FMRFSD和FMRFS处理最高, 达到40.38%~41.17%; FMRF和 CPSD处理次之, 18.21%~24.17%; CPs 处理最低, 5.15%(图1)。同时, 各处理也使0~30 cm土层SOC和TN的积累量分别提高了0.58~2.27 mg C· hm-2、0.0056~0.1199 mg N· hm-2和1.70%~6.47%、0.19%~3.59%, 相当于年均增加了0.19~0.79 mgC· hm-2和 0.0018~0.0400 mg N· hm-2, 也都以FMRFSD和FMRFS处理最高, FMRF, CPSD和CPS处理次之, CP处理最低(表3)。秸秆还田添加腐解剂与常规耕作和全膜双垄耕作结合, 都有效地提高了0~30 cm土层SOC和TN含量和积累量, 秸秆还田添加腐解剂与全膜双垄耕作结合更高效。

图1 2015-2017年0~30 cm土层秸秆碳平均固存效率Fig.1 Average straw carbon sequestration efficiency (CSE) in 0-30 cm soil profile during 2015-2017(Mean± SD, n=3)

2.2 不同处理对土壤全磷全钾和速效氮磷钾含量的影响

试验各处理显著地提高了TP、TK、AN、AP和AK的含量, 尤其是AP、AK和TK含量(表4), 但对不同营养元素含量的影响略有不同。FMRFSD处理有效地提高了TP含量, 与其他处理间差异显著(P< 0.05); FMRFSD和FMRFS处理更有利于提高AN的含量, 并与其他处理间差异显著(P< 0.05); 而FMRFSD、FMRFS和FMRF处理都有效地提高了AP和AK的含量, 与其他处理间差异显著(P< 0.05)。3年累计, 各处理使0~30 cm耕层TP、TK、AN、AP和AK含量, 比CP分别提高了0.01~0.05、1.23~3.05 g· kg-1和4.50~10.80、0.00~8.90、6.00~101.50 mg· kg-1, 相应地提高了1.39%~6.94%、6.16%~15.28%、4.27%~10.24%、0~56.69%、3.27%~55.34%。添加秸秆腐解剂处理(FMRFSD和CPSD)在与同一耕作措施结合时都是最优的, FMRFSD在所有处理中是最优的。表明, 秸秆还田添加腐解剂与全膜双垄土壤耕作结合, 更有效地提高了土壤速效磷、钾的含量。

表4 不同处理组合对0~30 cm耕层土壤全磷、全钾和有效氮、磷、钾含量的影响 Table 4 Effect of different treatments on the content of soil total phosphorus, potassium (TP, TK) and available nitrogen, phosphorus, potassium (AN, AP, AK) of 0-30 cm topsoil
2.3 不同处理对土壤容重和土壤pH的影响

各处理均显著地降低了0~30 cm土层土壤容重(BD), 表现为FMRFSD< FMRFS< FMRF< CPSD< CPS, 其中FMRFSD和FMRFS处理与CP处理相比都达到了显著水平(P< 0.05) (图2)。测定结果表明, 3年试验期间各处理的土壤BD比常规种植处理降低了2.3%~3.9%, 比试验前基础值降低了3.1%~4.7%。同时, 各处理也显著降低了土壤pH值(图3), 以FMRFSD处理降低最多, FMRFS和FMRF处理次之, CPSD、CPS和CP处理最低无显著差异(P> 0.05)。研究结果表明, 各处理使0~30 cm土层土壤pH值分别比CP和试验前降低了0.006~0.017和0.007~0.024, 相对降低了0.07%~0.21%和0.08%~0.29%。表明, 秸秆还田与不同耕作措施结合都降低了土壤BD和pH, 以添加腐解剂的处理最显著。

图2 不同处理对0~30 cm 土层土壤容重的影响Fig.2 Effect of different treatments on soil bulk density in 0-30 cm soil layer (Mean± SD, n=3)

图3 不同处理对0~30 cm 土层土壤pH的影响Fig.3 Effect of different treatments on soil pH in 0-30 cm soil layer (Mean± SD, n=3)

3 讨论
3.1 秸秆还田添加腐解剂对土壤有机碳(SOC)和全氮(TN)积累的影响

SOM含量与SOC和TN的积累量呈显著正相关关系[6, 7]。秸秆还田通过提高SOM含量, 添加新鲜碳源, 从而有效地促进了SOC和TN的积累[8, 9]。秸秆还田添加秸秆腐解剂[14, 28, 32], 特别是与增施氮肥结合[14, 29], 通过加速秸秆腐解进一步促进了SOC和TN的积累。本研究印证了以上研究结果, 并证明FMRFSD显著提高了还田秸秆碳的固存效率[6], 更高效地促进了SOC和TN的耕层积累。主要的原因是, 秸秆还田增加了土壤有机物质的投入, 在添加腐解剂[14, 28, 32]和优化了的土壤水热环境[31, 32, 34]作用下, 降低了秸秆C∶ N[27], 激发了微生物活性, 产生的增效作用有效地促进秸秆分解, 释放的秸秆碳和氮抵消了短期秸秆还田导致的土壤有机碳氮矿化和作物养分吸收导致的土壤碳氮含量降低的负面影响[35]。同时, 加速了的秸秆分解-腐殖化过程效率和现有土壤有机质矿化速率之间达到了一个新的高水平的平衡[31], 从而比对照提高了SOC和TN的含量。但也有在低氮投入情况下增加碳投入加速作物系统碳流失的报道[36]。

3.2 秸秆还田添加腐解剂对土壤化学性状的影响

作物秸秆含有丰富的C、N、P、K和微量元素, 是重要的有机肥源[36]。秸秆还田增加的土壤有机质有助于养分供应, 对提高土壤肥力发挥着关键作用[11, 37]。 本研究结果表明, FMRFSD有效地提高了土壤全N、P、K和速效N、P、K含量, 特别是显著地提高了土壤AP和AK的含量。主要归因于:一是秸秆还田增加了土壤中有机物质的输入量; 二是秸秆地膜双覆盖提高了土壤温度和土壤水分保有量[31], 输入的秸秆为微生物代谢活动提供了丰富的碳源而激发了其活性[38, 39, 40, 41], 二者协同增效促进了还田秸秆的分解与养分释放[34], 释放的养分部分转化为土壤养分[12, 13, 14], 部分抵消了作物快速生长养分吸收移除产生的土壤养分损失, 从而保持或提升了土壤N、P、K养分含量[30]; 三是膜下秸秆还田比地面秸秆覆盖有效地加快了秸秆分解, 玉米秸秆相对于小麦(Triticum aestivum)等其他作物秸秆分解快[2, 3, 13], 因而有较多的养分回归土壤, 与前人研究结果[13, 14, 15, 31, 34]基本一致。土壤磷含量的增加可增加作物根生物量及粗根的比重[42], 这对旱地作物汲取土壤深层养分和水分、抗旱增产具有重要意义。再者, 秸秆还田后增加了土壤中的有机质含量, 通过微生物的分解形成了腐殖酸, 胶结土壤颗粒成土壤团聚体, 使土壤孔隙度增大, 土壤容重变小, 更易于截留、吸附渗入土壤中的水分和释放出的营养元素离子, 而提高速效养分元素含量, 标志着土壤有机质活性的提高和土壤肥力状况的改善[25]。

3.3 秸秆还田添加腐解剂对土壤物理性状的影响

长期秸秆还田降低了土壤BD, 秸秆还田量与土壤BD呈负相关关系[5, 33]。本研究充分验证了这一结论, 并证明FMRFSD模式更有效地降低了研究区土壤BD, 主要归因于添加腐解剂促进了还田秸秆腐解, 产生更多的SOM, 进而改善土壤结构、增大孔隙度、降低土壤容重[25]。同时, 秸秆还田, 特别是接种腐解菌, 能有效促进有机质分解产生大量的铵而降低土壤pH[17], 归因于秸秆反硝化作用[11]。本研究结果表明, FMRFSD处理明显地降低了的土壤pH值, 证明了Liu等[17]的研究结果, 但有悖于Malhi等[11]的结果, 可能主要归因于覆盖沟垄耕作强的土壤水热状况改善作用、接种腐解剂和试验年限的差异。

秸秆还田是中国大部分地区土壤肥力管理的一个有效措施[10]。秸秆还田添加腐解剂显著提高SOM含量, SOM矿化形成植物可利用氮和其他养分的源和库[31]。增加有机质回归土壤维持着旱地土壤有机质水平[4, 34], 释放的养分补充平衡了土壤养分[4, 35], 从而改善土壤质量和肥力[28]。

4 结论

秸秆还田添加腐解剂与全膜双垄耕作结合, 通过膜秸双覆盖创造的良好水热环境与添加的微生物腐解剂结合, 形成的协同增效作用加速了还田秸秆的腐解, 产生的腐解产物抵消了土壤有机质矿化损失, 腐解释放的养分补充了作物生产对土壤养分的消耗; 而土壤水热及养分条件的改善, 又加速作物生长, 使更多的有机物(秸秆、落叶、根茬)回归土壤, 反过来又增加了土壤有机质、有机碳的积累。这种良性循环机制促进了SOC、土壤全量速效N、P、K含量显著提升, 尤其显著提升了旱地土壤磷、钾的含量。秸秆还田添加腐解剂与全膜双垄耕作结合还显著降低了土壤容重和土壤pH值, 改善了土壤结构和孔隙状况, 增加了土壤保水、蓄肥能力, 从而提高了土壤肥力水平。因此, 秸秆还田添加腐解剂与全膜双垄耕作结合是目前旱地农田有机质、碳库和土壤肥力最有效管理模式。而全膜双垄膜下秸秆还田添加腐解剂与适量增施氮肥结合, 进一步提升土壤碳库和肥力管理水平的研究还有待加强。

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