深耕配合施用有机肥提高15—30cm土层小麦根长密度

【目的】耕作方式与有机物料影响小麦根系生长和产量,比较不同耕作方式和施用不同有机物料条件下小麦根系生长的特征,为建立合理的耕作方式与有机物料配合方案提供理论依据和技术支撑。【方法】田间定位试验位于安徽舒城,始于2016年。于2019年10月—2020年5月,选取其中旋耕+秸秆还田(RS)、深耕+秸秆还田(DS)、旋耕+有机肥(RM)、深耕+有机肥(DM)4个处理小区,监测小麦根系生长特征;小麦收获后测量土壤紧实度,并采集0—15和15—30 cm土样,分析土壤理化性质;每年小麦成熟期调查小麦产量。【结果】与旋耕相比,深耕处理显著降低了15—30 cm土层中土壤紧实度,平均降低幅度为18.02%,且增加了小麦根长密度,平均增加幅度为10.23%。深耕配合有机肥处理(DM)15—30 cm土层土壤有机质、全氮、有效磷含量最高,较其他处理的提升幅度分别为10.42%~16.56%、8.18%~45.12%、21.53%~29.13%;小麦根长密度提升幅度最大,小麦整个生育期平均较其他处理提升了10.88%~22.91%,其中在0—15、15—30、30—45 cm土层中的平均提升幅度分别为8.69%~18.67%、12.29%~27.99%、12.62%~30.61%。偏最小二乘法路径模型(PLSPM)分析表明,耕作方式主要是通过降低土壤紧实度,增施有机物料主要是通过提高土壤养分含量,来促进小麦根系生长,且在15—30 cm土层中土壤养分和紧实度对小麦根长密度的影响程度强于0—15 cm土层。【结论】深耕结合有机肥更有利于降低土壤紧实度、提高土壤养分含量、促进小麦根系生长,尤其在15—30 cm土层,小麦根长密度显著增加,这有利于深土层根系的增加,进而实现小麦的高产稳产。

连续三年减施氮肥对潮土玉米生长及根际土壤氮素供应的影响

[目的]我国北方农业生产中氮肥过量施用现象较普遍,冬小麦夏玉米轮作体系是当地主要种植方式。研究轮作体系氮肥减施对玉米产量、氮肥利用率、根系形态及根际中无机氮特征的影响,为集约化农业生产体系中氮肥合理施用提供支持。[方法]选择河北衡水潮土试验点冬小麦夏玉米轮作体系,连续开展了三年田间试验,小麦收获后免耕播种夏玉米。冬小麦季设置 N 0、180、225、300 kg/hm^2 四个氮肥用量处理,其夏玉米季相应氮肥用量依次设置为 N 0、144、180 和 240 kg/hm^2,为不施氮肥、减施 40%、减施 25%和习惯施氮量处理。分别在玉米生育期的苗期、大喇叭口期、灌浆期及收获期在处理小区随机选植株 5 株,测定玉米籽粒产量、地上部氮含量、氮累积量及根际土壤中无机氮等指标,利用 WinRHIZO 根系分析系统分析获取根长、直径等数据。[结果]与 N240 处理相比,N144、N180 处理连续三年的玉米籽粒产量、地上部含氮量与氮累积量、根系长度与直径、根际土壤硝态氮与铵态氮含量均未受到明显影响,而氮肥利用率显著提高,农田氮素表观损失降低。三季 N0、N144 和 N180 处理的夏玉米籽粒产量、非根际土壤硝态氮和铵态氮含量出现下降。除2008 年大喇叭口期之外,三季玉米所有生育时期中,施用氮肥处理的夏玉米根际土壤硝态氮含量明显低于非根际土壤。2008 年玉米抽雄期,根际土壤中铵态氮含量显著高于非根际土壤,而在收获期,根际土壤铵态氮含量比非根际土壤明显降低。同一生育期,氮肥减施未明显降低根际土壤铵态氮含量。2008 和 2009 年两季玉米籽粒产量均与大喇叭口期以后地上部氮累积量呈显著正相关,而 2010 年只与苗期和成熟期显著相关。2009 年玉米根际硝态氮含量均与玉米产量呈正相关,生育后期呈极显著正相关关系,而除大喇叭口期非根际土壤硝态氮含量与玉米籽粒产量不相关外,其他生育期的非根际土壤硝态氮含量均与籽粒产量显著相关。[结论]在华北小麦玉米轮作种植体系下,在土壤肥力水平较高地区,连续三年减氮 25%甚至 40%,未显著改变夏玉米根系形态及根际无机氮供应水平,氮肥利用率显著提高,但非根际无机氮供应水平和籽粒产量有下降趋势。因此,在河北高肥力地区小麦玉米轮作下短期减少氮肥用量可行,持续减施还需进一步研究。

长期施肥下我国灌淤土粮食产量和土壤养分的变化

【目的】灌淤土是我国西北地区重要的粮食和经济作物土壤。了解灌淤土上作物产量的变化,及其对长期施肥的响应,以及灌淤土生产力的变化与其氮磷钾含量的关系,为西北地区作物增产和灌淤土培肥与可持续利用提供理论依据。【方法】1988到2004年间,在宁夏银川市、吴忠市、石嘴山市和新疆和田市典型灌淤土区域陆续建立了7个国家耕地质量监测点。2016年,利用时间趋势分析法,探讨了作物产量随时间的变化趋势,分析了长期不施肥和常规施肥条件下,玉米、小麦和水稻产量、产量变异系数、可持续性指数、增产率及地力贡献指数的变化特征,并进一步探讨了增产率与土壤养分的关系。【结果】灌淤土上小麦产量随时间呈现递增的趋势,在2004年达到最高(7.58 t/hm^2),之后保持稳定,2016年约为初始年产量的3倍;玉米产量随时间一直呈递增趋势,2016年平均产量为9.8 t/hm^2,约为初始年的两倍;水稻产量近年来变化不大。与不施肥相比,常规施肥下小麦、玉米(28年间)和水稻(8年间)分别平均增产3.43倍、3.20倍和1.21倍,产量可持续性指数分别提高了18.8%、148%和13.9%。监测以来,小麦和玉米农田的地力贡献指数略有下降,但变化不显著。水田的地力贡献指数以每年0.0125的速率增加。28年间,常规施肥使土壤全氮含量从0.4 g/kg提高到1.1 g/kg,有效磷和速效钾含量变化不大。小麦与玉米的增产率与土壤全氮含量呈显著直线正相关关系,小麦、玉米和水稻的平均氮肥农学效率分别为9.8、16.8和27.4 kg/kg。【结论】灌淤土上常规施肥(主要是氮肥)有效提高了玉米、小麦和水稻的产量。土壤全氮含量呈增加趋势,有效磷和有效钾含量基本平稳。土壤肥力对玉米和小麦产量的贡献呈下降趋势,对水稻产量的贡献高且平稳。因此,灌淤土应在合理施用氮肥的同时,注重采取提升地力,实现作物的高产和高效。

增施有机肥改善黑土物理特性与促进玉米根系生长的效果

为改善东北黑土区粘重耕层的土壤物理特性,通过玉米秸秆还田基础上增施有机肥试验,拟明确增施有机肥对黑土物理特性和根系生长的提升效果。利用2015~2018年吉林省公主岭市和黑龙江省克山县黑土区的定位试验,测定了玉米抽雄期3种秸秆还田处理及其增施有机肥(旋耕秸秆还田+有机肥RSM、深翻秸秆还田+有机肥DSM、深松秸秆还田+有机肥SSM)处理的土壤物理指标;并采用微根管法原位测定了根系生长指标,计算出增施有机肥后各土壤物理特性与根系生长指标的变化量。结果表明,相比秸秆还田处理,增施有机肥降低了土壤容重、土壤紧实度,提升了土壤含水量,同时根长密度、根尖数密度和根平均直径均显著增加,其中根长密度和根尖数密度各土层平均增加了0.18 cm/cm^2和34.9×10-3个/cm^2。不同秸秆还田方式增施有机肥后对黑土物理特性和根系生长的改善效果不同,其中0~15 cm土层RSM处理改善效果最明显,15~45 cm土层SSM和DSM处理改善效果最明显。有机肥和秸秆还田方式互作对黑土物理特性和促进根系生长指标具有显著的正向互作效应。上述结果表明,深松秸秆还田和深翻秸秆还田基础上增施有机肥模式更有利于改善黑土物理特性和促进根系生长,是改善东北黑土区粘重耕层的技术选择。

The efficiency of long-term straw return to sequester organic carbon in Northeast China＇s cropland

Black soil is one of the most precious soil resources on earth because it has abundant carbon stocks and a relatively high production capacity. However, decreasing organic matter after land reclamation, and the effects of long-term inputs of organic carbon have made it less fertile black soil in Northeast China. Straw return could be an effective method for improving soil organic carbon（SOC） sequestration in black soils. The objective of this study was to evaluate whether straw return effectively increases SOC sequestration. Long-term field experiments were conducted at three sites in Northeast China with varying latitudes and SOC densities. Study plots were subjected to three treatments： no fertilization（CK）; inorganic fertilization（NPK）; and NPK plus straw return（NPKS）. The results showed that the SOC stocks resulting from NPKS treatment were 4.0 and 5.7% higher than those from NPK treatment at two sites, but straw return did not significantly affect the SOC stocks at the third site. Furthermore, at higher SOC densities, the NPKS treatment resulted in significantly higher soil carbon sequestration rates（CSR） than the NPK treatment. The equilibrium value of the CSR for the NPKS treatment equated to cultivation times of 17, 11, and 8 years at the different sites. Straw return did not significantly increase the SOC stocks in regions with low SOC densities, but did enhance the C pool in regions with high SOC densities. These results show that there is strong regional variation in the effects of straw return on the SOC stocks in black soil in Northeast China. Additional cultivations and fertilization practices should be used when straw return is considered as an approach for the long-term improvement of the soil organic carbon pool.

Increasing soil microbial biomass nitrogen in crop rotation systems by improving nitrogen resources under nitrogen application

Soil microbial biomass nitrogen(MBN)contains the largest proportion of biologically active nitrogen(N)in soil,and is considered as a crucial participant in soil N cycling.Agronomic management practices such as crop rotation and monocropping systems,dramatically affect MBN in agroecosystems.However,the influence of crop rotation and monocropping in agroecosystems on MBN remains unclear.A meta-analysis based on 203 published studies was conducted to quantify the effect of crop rotation and mono-cropping systems on MBN under synthetic N fertilizer application.The analysis showed that crop rotation significantly stimulated the response ratio(RR)of MBN to N fertilization and this parameter reached the highest levels in upland-fallow rotations.Upland mono-cropping did not change the RR of MBN to N application,however,the RR of MBN to N application in paddy mono-cropping increased.The difference between crop rotation and mono-cropping systems appeared to be due to the various cropping management scenarios,and the pattern,rate and duration of N addition.Crop rotation systems led to a more positive effect on soil total N(TN)and a smaller reduction in soil pH than mono-cropping systems.The RR of MBN to N application was positively correlated with the RR of mineral N only in crop rotation systems and with the RR of soil pH only in mono-cropping systems.Combining the results of Random Forest(RF)model and structural equation model showed that the predominant driving factors of MBN changes in crop rotation systems were soil mineral N and TN,while in mono-cropping systems the main driving factor was soil pH.Overall,our study indicates that crop rotation can be an effective way to enhance MBN by improving soil N resources,which promote the resistance of MBN to low pH induced by intensive synthetic N fertilizer application.

Assessment of the contribution percentage of inherent soil productivity of cultivated land in China

The contribution percentage of inherent soil productivity(CPISP)refers to the ratio of crop yields under no-fertilization versus under conventional fertilization with the same field management.CPISP is a comprehensive measure of soil fertility.This study used 1086 on-farm trials(from 1984-2013)and 27 long-term field experiments(from 1979-2013)to quantify changes in CPISP.Here,we present CPISP3 values,which reflect the CPISP states during the first three years after site establishment,for a series of sites at different locations in China collected in 1984-1990(the 1980s),1996-2000(the 1990s),and 2004-2013(the 2000s).The results showed that the average CPISP3 value for three crops(wheat,rice,and maize)was 53.8%.Historically,the CPISP3 in the 1990s(57.5%)was much higher than those in the 1980s(50.3%),and the 2000s(52.0%)(P≤0.05).Long-term no-fertilization caused CPISP levels to gradually decline and then stabilize;for example,in a mono-cropping system with irrigation,the CPISP values in Northwest and Northeast China declined by 4.5 and 4.0%,respectively,each year for the first ten years,but subsequently,the CPISP values stabilized.In contrast,the CPISP for upland crops in double-cropping systems continued to decrease at a rate of 1.1%per year.The CPISP for upland-paddy cropping decreased very slowly(0.07%per year),whereas the CPISP for paddy cropping decreased sharply(3.1%per year,on average)for the first two years and then remained steady during the following years.Therefore,upland crops in double-cropping systems consume the most inherent soil productivity,whereas paddy fields are favourable for maintaining a high level of CPISP.Overall,our results demonstrate a need to further improve China’s CPISP3 values to meet growing productivity demands.

Forage Species Suitability Mapping for China Using Topographic, Climatic and Soils Spatial Data and Quantitative Plant Tolerances

Selecting plants adapted to the climatic and soil conditions of specific locations is essential for environmental protection and economic sustainability of agricultural and pastoral systems. This is particularly true for countries like China with a diversity of climates and soils and intended uses. Currently, proper species selection is difficult due to the absence of computer-based selection tools. Climate and soil GIS layers, matched with a matrix of plant characteristics through rules describing species tolerances would greatly improve the selection process. Better matching will reduce environmental hazards and economic risks associated with sub-optimal plant selection and performance. GIS-based climate and soil maps have been developed for China. A matrix of quantitative species tolerances has been developed for example forage species and used in combination with an internet map server that allows customized map creation. A web-based decision support system has been developed to provide current information and links to original data sources, supplementary materials, and selection strategies.

Integrated management of crop residue and nutrient enhances new carbon formation by regulating microbial taxa and enzymes

Although returning crop residue to fields is a recommended measure for improving soil carbon(C)stocks in agroecosystems,the response of newly formed soil C(NFC)to the integrated supply of residue and nutrients and the microbial mechanisms involved in NFC are not fully understood.Therefore,an 84-day incubation experiment was conducted to ascertain the microbial mechanisms that underpin the NFC response to inputs of residue and nitrogen(N),phosphorus(P),and sulfur(S)in two black(Phaeozem)soils from experimental plots at Gongzhuling,Jilin Province and Hailun,Heilongjiang Province,China.The results showed that adding residue alone accelerated microbial nutrient mining,which was supported by decreases of 8^(-1)6%in the ratios of C:N and C:P enzyme activities,relative to soils with nutrient inputs.The NFC amounts increased from 1156 to 1722 mg kg^(−1) in Gongzhuling soil and from 725 to 1067 mg kg^(−1) in Hailun soil as the levels of nutrient supplementation increased.Boosted regression tree analysis suggested thatβ-glucosidase(BG),acid phosphatase(AP),microbial biomass C(MBC),and Acidobacteria accounted for 27.8,18.5,14.7,and 8.1%,respectively,of the NFC in Gongzhuling soil and for 25.9,29.5,10.1,and 13.9%,respectively,of the NFC in Hailun soil.Path analysis determined that Acidobacteria positively influenced NFC both directly and indirectly by regulating BG,AP,and MBC,in which MBC acquisition was regulated more by AP.The amount of NFC was lower in Hailun soil than in Gongzhuling soil and was directly affected by AP,indicating the importance of soil properties such as SOC and pH in determining NFC.Overall,our results reveal the response of NFC to supplementation by N,P,and S,which depends on Acidobacteria and Proteobacteria,and their investment in BG and AP in residue-amended soil.