覆盖作物的种植现状及其对下茬作物生长和土壤环境影响的研究进展

覆盖作物指的是在农业生产间隙种植,使土壤在时间或空间上减少或避免裸露的一种作物。其能使农田土壤免受风蚀、水蚀和人为扰动的影响,被认为是一种新型的保护性耕作方式。本文简要介绍了农田覆盖作物的种植管理情况,包括种植品种、耕作模式和绿肥作物的灭生还田方式等,可为推广覆盖作物在农田休闲期的高效大面积种植提供参考。基于国内外研究综述了绿肥种植对经济作物、土壤质量、杂草抑制、温室气体排放和土壤微生物等的影响及研究进展,阐明了覆盖作物对农田生态系统的诸多益处。尽管覆盖作物存在局限性,例如短期收益不明显、管理措施不当会造成作物减产等,但其在改善土壤质量、实现农业可持续发展方面仍然具有重要的应用价值。     

黄土高原土壤侵蚀作物覆盖因子计算

土地利用方式以及不同农作物对土壤流失有明显的影响,定量评价不同作物在土壤流失中的作用（作物覆盖因子）是土地利用和水土保持规划的重要依据。研究的目的在于计算黄土高原主要农作物不同生长阶段的土壤流失强度与裸露地的比率,为计算土壤侵蚀作物覆盖因子应用。通过对甘肃天水和陕西安塞水土保持试验资料的分析,计算了7种主要作物6个农作期的土壤流失比率表,并对黄土高原7种作物覆盖因子进行了计算,其值在0.23-0.74之间,按此方法计算的作物覆盖因子值与观测多年平均土壤流失比率基本一致。但该方法的优势在于可以根据土壤流失比率表和不同的降雨侵蚀力分布曲线计算不同地区的C值,而不需对每个地区都进行小区观测。     

冬季覆盖作物秸秆还田对双季稻田根际土壤微生物群落功能多样性的影响

微生物群落功能多样性是土壤质量变化重要的指标,不同作物类型的秸秆还田措施对土壤微生物群落功能多样性具有明显的影响。以位于双季稻主产区不同冬季覆盖作物-双季稻种植模式大田定位试验田为研究对象,以冬闲-双季稻种植模式为对照(CK),应用Biolog-GN技术开展黑麦草-双季稻(Ry)、紫云英-双季稻(Mv)、油菜-双季稻(Ra)和马铃薯-双季稻(Po)种植模式条件下不同冬季覆盖作物秸秆还田后对双季稻田根际土壤微生物功能多样性影响的研究。研究结果表明,早稻和晚稻成熟期,与CK处理相比,冬季覆盖作物秸秆还田处理增加了稻田土壤碳源平均颜色变化率(AWCD),以Po处理AWCD均为最高,均显著高于Ry和CK处理。不同冬季覆盖作物秸秆还田处理土壤微生物代谢多样性指数表现出明显的差异,早稻成熟期,Po处理的Richness、Shannon和McIntosh指数均为最高,其次为Ry、Mv和Ra处理,CK处理最低;晚稻成熟期,各处理的Richness、Shannon和McIntosh指数大小顺序均表现为PoRaMvRyCK。土壤微生物碳源利用的主成分分析结果表明,各冬季覆盖作物秸秆还田处理根际土壤微生物利用的主要碳源为氨基酸类和糖类物质,不同处理间碳源利用类型有差异。冬季覆盖作物秸秆还田措施有利于提高双季稻田根际土壤微生物对碳源的利用能力、物种丰富度和均匀度。     

不同耕作方式对内蒙古旱作农田土壤侵蚀的影响

研究黄河流域内蒙古黄土高原丘陵区农田土壤侵蚀状况,对本区域生态农业建设具有重要的意义。试验于2006年在内蒙古呼和浩特市清水河县进行,设免耕(NT)、免耕覆盖(NS)和传统耕作(CT)3种耕作处理方式,种植作物为胡麻和燕麦,观测了全年降雨量和地表水径流量及土壤流失量。结果表明:免耕覆盖及免耕能显著减少降雨对土壤的侵蚀,与传统耕作相比,免耕覆盖处理的燕麦地地表水径流量和土壤的流失量分别减少21.9%和88.3%;3种耕作方式的土壤侵蚀量均受到坡度的影响,并随着坡度的增大而增大,相同环境条件下,不同作物存在一定差异;通过对3种耕作方式下,胡麻和燕麦田土壤侵蚀量与降雨量的关系符合幂函数,且拟合优度良好,均>0.9。     

东北三江平原覆盖作物种植效果

以土壤紧实度、冬前生物量、根系性状、植株氮累积量等为指标对供试12种覆盖作物(豆科:紫花苜蓿、光叶苕子、毛叶苕子、红三叶、白三叶、箭筈豌豆;非豆科:苏丹草、青萝卜、Nitro radish、甘蓝型油菜、羽衣甘蓝、菊苣)在东北三江平原地区的种植效果及应用潜力进行综合评价。结果表明: 12种覆盖作物在试验播期均能正常生长,不同覆盖作物与对照相比均有利于降低土壤紧实度,其中青萝卜、Nitro radish和苏丹草土壤紧实度下降最显著,分别较对照下降了47.1%、43.4%和33.4%;覆盖作物群体冬前鲜生物量为3.38～13.98 kg·m^-2,干生物量为0.78～2.43 kg·m^-2,非豆科覆盖作物的生物量显著高于豆科覆盖作物;覆盖作物的群体根系体积以萝卜、油菜、菊苣较大,尤其Nitro radish的根体积高达4018.5 cm³·m^-2,苏丹草的根系横向延展范围最宽;豆科覆盖作物的灰分含量显著低于非豆科覆盖作物,能提供更多易分解的有机物质;覆盖作物总氮积累量为18.72～53.09 g·m^-2,其中,羽衣甘蓝和菊苣的氮积累量最高,且生物量相对较大,有利于氮的积累和固定。在三江平原地区根据主栽作物的类型与冠层结构,选择豆科的三叶草、苕子、紫花苜蓿和非豆科的萝卜、羽衣甘蓝、苏丹草作为覆盖作物进行行间或行内混播的种植方式,可以在调控土壤结构的同时促进养分循环,有利于三江平原黑土地力的提升。     

地膜覆盖棉花、玉米、大豆生育盛期的降温效应

1999～2001年的试验结果表明地膜覆盖在夏季作物旺盛生长期(棉花：开花-吐絮、玉米：抽雄穗-乳熟、大豆：开花-结荚)3种覆盖作物的叶面积均比对照作物大,其叶面积系数分别为：棉花：3．9／3．1、玉米：3．3／2．7、大豆：4．0／3．2。进入作物群体中的光照度(I)主要与叶面积系数(F)有关,而叶面积系数又直接影响消光系数(k)的大小。农田覆盖地膜后,其在作物生育前期的增温保湿作用,使其作物生育速度加快,到作物旺盛生长期因其枝叶茂盛,叶面积系数增大,消光系数减小,白天冠层上部叶片截留的太阳总辐射多,致使最终进入作物群体中下部的光能减少。白天覆盖地虽然蒸发量减少,但因其作物枝叶茂盛,蒸腾量则增大,农田消耗于蒸散(LEc)的能量增多,导致加热土壤(B项)的能量减少。覆盖作物地的土壤温度较对照地低,其中又以白天地面最高温度降温最为明显．棉花、玉米、大豆等3种作物降温幅度分别为3．1C、2．7C和2．5C。地膜覆盖在作物旺盛生长期的降温效应,可减轻夏季高温对作物的危害,夏季白天当温度超过光合作用适宜温度(20～25C)以上时,呼吸作用消耗的有机物质增加,作物生长缓慢,而覆盖作物地因其温度较对照地低,光合强度大,生长活力增强,因而使作物能够增产。     

北方旱作区沟垄二元覆盖技术研究进展

北方旱作区降水稀少,水分不足是限制作物生长的主要因素,沟垄二元覆盖技术可进一步提高降水的利用效率和作物生产水平,在国内外已备受关注.为深刻理解中国北方旱作区沟垄二元覆盖技术模式及研究进展,本文就沟垄二元覆盖技术的概念、研究现状、配套农机具、技术模式及其土壤生态与作物效应进行了综述;在总结现有研究的基础上,归纳了典型旱作区沟垄二元覆盖技术模式的类型、作业操作及应用效果;科学评价不同沟垄二元覆盖技术下土壤与作物的生态效应;指出了目前沟垄二元覆盖技术研究中所存在的问题,并提出相应的建议.综合国内外沟垄集雨栽培技术的研究进展,提出沟垄二元覆盖模式及技术体系今后的重点研究方向:1)建立适合北方不同旱作类型区及不同作物的垄沟比;2)重视土壤水分与温度、肥力等其他因子耦合性研究;3)探索最佳环保型覆盖材料;4)加强沟垄二元覆盖模式及体系的技术评价、技术推广与配套机具设计等方面的研究.     

施用保水剂和稻草覆盖对作物和土壤的效应

在江苏淮北东海县季节性干旱严重的岭沙土上,开展了施用保水剂和稻草覆盖对保持土壤水分和作物产量的效应的比较试验,保水剂和稻草的用量各分4级,分别为1,2,3,6g.kg^-1土和1500,3000,4500,6000kg/hm^-2,结果表明,两者均可促进小麦生长,提高当季及后茬作物产量,覆盖稻草和施用保水剂分别比对照增产小麦12．5％和10％,其作用机制在于两者均能减少土壤水分蒸发,提高土壤持水能力,增加有效水供应,并对土壤容重,温度及养分状况有一定的改善作用。     

西南喀斯特区坡耕地秸秆覆盖对土壤生态化学计量特征及产量的影响

土壤养分亏缺是限制作物生长的关键因素,同时也是制约作物产量的重要影响因子。为提高西南喀斯特区坡耕地土壤肥力和作物产量,于2018—2019年连续两年在贵州省黔西县开展了野外原位径流小区观测试验。通过该试验探讨不同秸秆覆盖率下土壤碳(C)、氮(N)、磷(P)、钾(K)含量及其生态化学计量特征,揭示不同秸秆覆盖率下土壤养分状况及土壤改良效果。共设6个秸秆覆盖梯度,玉米单作+秸秆覆盖(SM₀—SM₅,0,1111、2222、3889、5556,6944 kg/hm~2),其中SM₀为对照组(CK)。结果表明：(1)秸秆覆盖不同程度增加了土壤有机碳(SOC)、全氮(TN)及全磷(TP)含量,总体上随覆盖量的增加而增加,尤其是覆盖量较多的情况下(SM₄,SM₅),均显著高于对照(P<0.05),但两者之间差异不显著(P> 0.05),而全钾(TK)则随着覆盖量的增加而减少。(2)在高秸秆覆盖条件下(SM₄,SM₅),除了N∶P外,两...     

地表覆草和覆膜对西北旱地土壤有机碳氮和生物活性的影响

研究地表覆盖对土壤有机碳氮和生物活性的影响,对改进旱地作物栽培,提升土壤肥力和提高作物产量具有重要意义。采取5a田间定位试验的土壤进行室内培养试验,研究不同地表覆盖土壤轻质有机碳、轻质有机氮及微生物活性的变化。结果发现,经过61d培养之后,覆草、覆膜和常规土壤矿质态氮含量分别减少4.0,2.5,3.9 mg/kg,有机碳矿化累积量分别为125,100,101 mg/kg。覆草土壤微生物量碳含量及土壤代谢熵在培养过程中均高于覆膜。培养前后,覆草土壤的轻质有机碳氮均明显高于覆膜,覆膜和常规没有差异。培养结束后,覆草土壤轻质有机碳氮含量分别减少36%和47%,覆膜土壤分别减少26%和45%,常规土壤分别减少31%和44%。覆草土壤轻质有机碳氮含量的减少值明显高于覆膜和常规。覆草能增加土壤有机碳氮的易矿化组分,提高土壤有机质的生物有效性,覆膜则会降低土壤有机质的生物有效性。     

不同冬季覆盖作物对双季稻田土壤有机碳的影响

以冬闲-双季稻种植模式为对照(CK),分析了黑麦草-双季稻(Ry)、紫云英-双季稻(Mv)、马铃薯-双季稻(Po)和油菜-双季稻(Ra)5种不同种植模式下冬季覆盖作物秸秆还田后对0～5、5～10、10～20 cm土壤有机碳、活性有机碳、碳库管理指数和有机碳储量的影响.结果表明:与CK处理相比,黑麦草、紫云英、马铃薯和油菜秸秆还田处理均提高了稻田0～5、5～10、10～20 cm土壤总有机碳和活性有机碳含量,其中Po处理最高.冬季覆盖作物秸秆还田均提高了稻田不同层次土壤的碳库活度、碳库活度指数、碳库指数和土壤碳库管理指数,其大小顺序均表现为Po>Mv>Ry>Ra>CK.不同冬季覆盖作物秸秆还田处理与CK处理相比均有利于提高稻田不同层次土壤有机碳储量,其中以紫云英秸秆还田的效果最好,黑麦草和马铃薯次之;各处理稻田土壤有机碳储量均随土壤深度的增加而递增.     

Energy cover crops for biogas production increase soil organic carbon stocks: A modeling approach

Energy cover crops for biogas production through anaerobic digestion (AD) are inserted between two primary crops. They replace either bare soil or nonharvested cover crops, and their management is usually intensified to produce more biomass. They allow the production of renewable energy as well as digestate, used as an organic fertilizer, without directly competing with food production. Because of the increased biomass production and export and of the return of a digested biomass to the soil, the impact of energy cover crops on soil organic carbon (SOC) is questioned. The objective of this paper was to study the difference in SOC stocks induced by the introduction of energy cover crops for AD coupled with the application of the resulting amount of digestate. We used the AD model Sys-Metha combined with the soil C model AMG to simulate SOC stocks for 13 case studies in France, with scenarios comparing different intercrop management practices, with or without cover crops, harvested or not. Our results indicated that the higher biomass production of energy cover crops (from 6.7 to 11.1 t DM ha⁻¹) in comparison with nonharvested cover crops (2 t DM ha⁻¹) or bare soil led to higher humified C input (belowground input and digestate), despite the high C fraction exported in AD. This resulted in an increase in SOC stocks in comparison with nonharvested cover crops or bare soil (from 0.01 to 0.12 t C ha⁻¹ year⁻¹ over 30 years). The uncertainties in the model parameters did not modify these results. However, in the case of equal biomass production between energy cover crops and nonharvested cover crops, SOC stocks would be lower with energy cover crops.     

A UK survey of the use and management of cover crops

There is a growing trend in the use of cover crops in the United Kingdom, and whilst research shows there are many soil and environmental benefits, little is known about the farmer's perspective of cover cropping. A survey was designed and distributed to ask farmers about their use and management of cover crops. The online survey received 117 usable responses between January and March 2017, following distribution through social media in the United Kingdom. The survey highlighted that 66% of respondents used cover crops following harvest in 2016. Respondents observed benefits to soil structure, soil erosion control and water infiltration in addition to reductions in the use of chemical fertilisers, herbicide and fuel use. Of those not using cover crops, 90% would consider their use in the future if additional information on their use and benefits were known in a UK context. Changes to the 2016 Basic Payment Scheme guidelines for cover crops would have been welcomed by 71% of respondents using cover crops.     

The effect of cover plants management on soil invertebrate fauna in vineyard in Northern Italy

Cover crops are largely used in vineyard management to improve ecological services such as pest and weed control, soil protection from erosion and soil water balance. Few data are available about the effects of cover crops on soil fauna and, in particular, on important generalist predators such as Carabidae and Araneae. We compare the effects of five different cover crops treatments: Sweet Alyssum, Phacelia, Buckwheat, Faba bean and a mixture of Vetch and Oat. A three years experimental trial was developed in Northern Italy. Soil fauna was investigated using pitfall traps. Cover crops seriously affected soil fauna of most taxa. Higher abundance of predators, in particular Carabidae and Staphylinidae, was present in treatments with legumes (Faba bean and Vetch and Oat) while soil Araneae seemed not to be affected. No vineyard pests seemed to be positively affected by cover crops. We confirm the importance of cover crops in increasing soil predator abundance and consequently improving pest control.     

Effect of winter cover crops on soil nitrogen availability,corn yield,and nitrate leaching

Biculture of nonlegumes and legumes could serve as cover crops for increasing main crop yield, while reducing NO3 leaching. This study, conducted from 1994 to 1999, determined the effect of monocultured cereal rye (Secale cereale L.), annual ryegrass (Lolium multiflorum), and hairy vetch (Vicia villosa), and bicultured rye/vetch and ryegrass/vetch on N availability in soil, corn (Zea mays L.) yield, and NO3-N leaching in a silt loam soil. The field had been in corn and cover crop rotation since 1987. In addition to the cover crop treatments, there were four N fertilizer rates (0, 67, 134, and 201 kg N ha(-1), referred to as N0, N1, N2, and N3, respectively) applied to corn. The experiment was a randomized split-block design with three replications for each treatment. Lysimeters were installed in 1987 at 0.75 m below the soil surface for leachate collection for the N 0, N 2, and N 3 treatments. The result showed that vetch monoculture had the most influence on soil N availability and corn yield, followed by the bicultures. Rye or ryegrass monoculture had either no effect or an adverse effect on corn yield and soil N availability. Leachate NO3-N concentration was highest where vetch cover crop was planted regardless of N rates, which suggests that N mineralization of vetch N continued well into the fall and winter. Leachate NO3-N concentration increased with increasing N fertilizer rates and exceeded the U.S. Environmental Protection Agency's drinking water standard of 10 mg N l(-1) even at recommended N rate for corn in this region (coastal Pacific Northwest). In comparisons of the average NO3-N concentration during the period of high N leaching, monocultured rye and ryegrass or bicultured rye/vetch and ryegrass/vetch very effectively decreased N leaching in 1998 with dry fall weather. The amount of N available for leaching (determined based on the presidedress nitrate test, the amount of N fertilizer applied, and N uptake) correlated well with average NO3-N during the high N leaching period for vetch cover crop treatment and for the control without the cover crops. The correlation, however, failed for other cover crops largely because of variable effectiveness of the cover crops in reducing NO3 leaching during the 5 years of this study. Further research is needed to determine if relay cover crops planted into standing summer crops is a more appropriate approach than fall seeding in this region to gain sufficient growth of the cover crop by fall. Testing with other main crops that have earlier harvest dates than corn is also needed to further validate the effectiveness of the bicultures to increase soil N availability while protecting the water quality.     

Seven-Year Impact of Cover Crops on Soil Health When Corn Residue Is Removed

Removing plant residue from soil has been shown to have an adverse effect on soil health; however, the addition of cover crops may help mitigate these impacts. This study was conducted to assess the effect of incorporating cover crops on soil health with varying removal rates of corn (Zea mays L.) residues. Corn was grown in rotation with soybean (Glycine max) in a randomized, split-block design with three different corn residue removal levels (37, 55, and 98% of total above-ground C) as whole plot treatments and the presence or absence of cover crops as the split plot treatment. Soil samples were collected from both crop phases following 7 years of cover crop treatment and subjected to a suite of soil health measurements. In the soybean phase immediately following corn residue removal, there were significant (P?=?0.025) increases in the erodible fraction (EF) of soil aggregates and reductions in the stable, larger aggregate fractions. Cover crops mitigated these changes in aggregate distributions in the highest residue removal treatment. Residue removal resulted in a significant decrease in fPOM (P?=?0.03) while the addition of cover crops increased fPOM levels during the soybean phase (P?=?0.002). Residue removal significantly (P?=?0.017) decreased soil microbial enzyme activities while cover crops restored activities in the highest residue removal treatment (P?=?0.037). We also found higher fungal:bacterial ratios with cover cropping compared to no cover crops. We conclude that cover cropping continued over multiple years can partially mitigate negative effects of crop residue removal on soil health thus limiting soil erosion and maintaining nutrient cycling activities in the vulnerable period following residue removal.     

Stem aqueous extracts of accumulator Bidens tripartita L. strongly promoted Solanum nigrum L. Cd hyperaccumulation from soil

Plant and Soil - Cover crops may restore soil functions lost with single summer crop sequences enhancing soil organic carbon and nitrogen (SOC and SON) stocks. We investigated the effect of cover...     

Assessing long-term impacts of cover crops on soil organic carbon in the central US Midwestern agroecosystems

Cover crops have been reported as one of the most effective practices to increase soil organic carbon (SOC) for agroecosystems. Impacts of cover crops on SOC change vary depending on soil properties, climate, and management practices, but it remains unclear how these control factors affect SOC benefits from cover crops, as well as which management practices can maximize SOC benefits. To address these questions, we used an advanced process-based agroecosystem model, ecosys, to assess the impacts of winter cover cropping on SOC accumulation under different environmental and management conditions. We aimed to answer the following questions: (1) To what extent do cover crops benefit SOC accumulation, and how do SOC benefits from cover crops vary with different factors (i.e., initial soil properties, cover crop types, climate during the cover crop growth period, and cover crop planting and terminating time)? (2) How can we enhance SOC benefits from cover crops under different cover crop management options? Specifically, we first calibrated and validated the ecosys model at two long-term field experiment sites with SOC measurements in Illinois. We then applied the ecosys model to six cover crop field experiment sites spanning across Illinois to assess the impacts of different factors on SOC accumulation. Our modeling results revealed the following findings: (1) Growing cover crops can bring SOC benefits by 0.33 ± 0.06 MgC ha⁻¹ year⁻¹ in six cover crop field experiment sites across Illinois, and the SOC benefits are species specific to legume and non-legume cover crops. (2) Initial SOC stocks and clay contents had overall small influences on SOC benefits from cover crops. During the cover crop growth period (i.e., winter and spring in the US Midwest), high temperature increased SOC benefits from cover crops, while the impacts from larger precipitation on SOC benefits varied field by field. (3) The SOC benefits from cover crops can be maximized by optimizing cover crop management practices (e.g., selecting cover crop types and controlling cover crop growth period) for the US Midwestern maize–soybean rotation system. Finally, we discussed the economic and policy implications of adopting cover crops in the US Midwest, including that current economic incentives to grow cover crops may not be sufficient to cover costs. This study systematically assessed cover crop impacts for SOC change in the US Midwest context, while also demonstrating that the ecosys model, with rigorous validation using field experiment data, can be an effective tool to guide the adaptive management of cover crops and quantify SOC benefits from cover crops. The study thus provides practical tools and insights for practitioners and policy-makers to design cover crop related government agricultural policies and incentive programs for farmers and agri-food related industries.