减量化肥配施紫云英对稻田土壤碳、氮的影响

以11 a(2008—2018年)长期定位试验为对象,研究了减施40%化肥下紫云英不同翻压量对双季稻产量及土壤活性有机碳、氮(DOC+MBC、DON+MBN)的影响,以探讨紫云英替代化肥的可行性和适宜翻压量。试验设置CK(不施紫云英和化肥)、GM_(22.5)(单施紫云英22.5 t·hm~(-2))、100%CF(常规施肥)和减施40%化肥(60%CF)条件下将紫云英翻压量设为15、22.5、30、37.5 t·hm~(-2)4个水平,共7个处理。于2018年晚稻收获后采集土壤样品,分析土壤微生物量碳、氮(MBC、MBN)和可溶性有机碳、氮(DOC、DON)。结果表明:与常规施肥相比,减施40%化肥下各紫云英不同翻压量处理早稻及全年两季稻谷产量持平或略有增加,且均随紫云英翻压量增多而提高。紫云英翻压量为15～30 t·hm~(-2)时,晚稻稻谷产量随紫云英翻压量的增多而提高,当紫云英翻压量多于30 t·hm~(-2)时,则呈下降趋势。除翻压紫云英15 t·hm~(-2)外,其他紫云英与化肥配施处理晚稻稻谷产量与常规施肥相比无显著差异;与常规施肥相比,紫云英与化肥配施均不同程度地提高了土壤MBC、MBN、DOC、DON含量。紫云英翻压量为15～22.5 t·hm~(-2)时,土壤MBC、MBN、DOC、DON均随紫云英翻压量增加而增加,当翻压量多于22.5 t·hm~(-2)时呈下降趋势;MBC/SOC和MBN/TN均随紫云英翻压量的增加呈先增加后降低的趋势,MBC/SOC在60%CF+GM_(22.5)处理最高,MBN/TN以60%CF+GM_(30)处理最高。DOC/SOC和DON/TN均在60%CF+GM_(15)处理最高;相关分析结果表明,土壤MBC、MBN、DOC、DON、DOC+MBC、DON+MBN与土壤有机碳(SOC)、全氮(TN)呈极显著正相关(P0.01)。土壤各活性有机碳、氮与早、晚稻及全年两季稻谷产量均呈极显著正相关(P0.01)。综合考虑双季稻的产量效应及土壤培肥效果,在本试验条件下或与该试验区域气候特点和种植制度类似的南方水稻主产区,在减少40%化肥条件下,紫云英翻压22.5～30 t·hm~(-2)较为适宜。     

紫云英利用后减施化肥对水稻产量和产值及土壤碳氮含量的影响

通过大田定位试验,研究连续5年紫云英利用后不同化肥施用量对水稻产量和稻谷经济效益及土壤碳、氮含量的影响。试验共设6个处理,处理CK:不施紫云英和化肥(对照);处理CF:不施紫云英,施100%化肥(N、P2O5、K2O施用量分别为150、75、120 kg/hm2);处理A1:紫云英(22 500 kg/hm2,下同)+100%化肥+100%磷肥;处理A2:紫云英+80%氮、钾肥+100%磷肥;处理A3:紫云英+60%氮、钾肥+100%磷肥;处理A4:紫云英+40%氮、钾肥+100%磷肥。结果表明:施肥可以显著提高水稻产量,紫云英利用后化肥的增产效果更为显著,与CF相比,处理A2的早稻产量提高了7.7%,处理A3的水稻产量基本持平;紫云英利用后适当减少化肥用量可以增加水稻产值,与CF相比,处理A1的水稻产值增加了5.92%,处理A2的水稻产值的增加效果次之,增加了4.08%;处理A4提高水稻土壤有机碳和全氮含量的效果明显优于处理CF,A2处理的土壤有机碳、全氮含量比CF显著降低。综合以上研究结果,认为翻压紫云英可以代替部分化肥,增加水稻产量,减少生产成本,提高养分利用效率。     

紫云英与化肥配施对水稻生长和土壤养分含量的影响

2009年在河南省信阳市农业科学研究所进行了紫云英(Astragaius sinicus L.)与化肥配施对水稻生长(Oryza sativa L.)和土壤养分含量影响试验。结果表明:紫云英和化肥配施可促进水稻生长,增加水稻产量,增加土壤有机质含量,提高土壤速效氮、磷、钾含量。其中,80%化肥的4个处理水稻的总产量为37205.63kg·hm-2,60%化肥的4个处理水稻的总产量为37395.01kg·hm-2。从紫云英翻压量来看,15000kg·hm-2的2个处理水稻总产量为19297.901kg·hm-2,22500kg·hm-2的2个处理水稻总产量为18956.25kg·hm-2,30000kg·hm-2的2个处理水稻总产量为17718.76kg·hm-2,37500kg·hm-2的2个处理水稻总产量为18628.13kg·hm-2。总的来看,化肥量60%和紫云英翻压量15000kg·hm-2、22500kg·hm-2配施比较适宜。     

Effects of Chinese Milk Vetch (Astragalus sinicus L.) Residue Incorporation on CH4 and N2O Emission from a Double-Rice Paddy Soil

Methane (CH₄) and nitrous oxide (N₂O) emissions from paddy soils have seldom been estimated when leguminous green manure is applied as a nitrogen source. In this paper, gas fluxes were measured by using a pot sampling device combined with a static chamber method to estimate the effects of Chinese milk vetch (Astragalus sinicus L., CMV) on CH₄ and N₂O emissions and their integrated global warming potentials (GWP) in a double-rice cropping system. Four treatments (no nitrogen fertilizer, NF; urea as chemical fertilizer, CF; CMV incorporation, MV; 50% CMV incorporation and 50% urea, MVCF) were established. CH₄ flux peaked on the 15th d after treatment application. Total season CH₄ emission was increased by MV and MVCF by 370 and 209%, 152 and 66%, when compared with NF and CF, respectively. Most of the increased CH₄ was emitted in the first two months after incorporation of CMV. N₂O emission from CF was 17- and 5.6-fold higher than that from MV and MVCF, respectively. Application of CMV restricted N₂O emission caused by the application of urea. Improved CMV residue management was needed to minify CH₄ emission induced by the input of organic material. Despite the highest GWP being found in MV, we recommend CMV, when applied as an N source in paddy fields, as a potential mitigation tool for greenhouse gas emissions.     

Substitution of chemical fertilizer by Chinese milk vetch improves the sustainability of yield and accumulation of soil organic carbon in a double-rice cropping system

The double-rice cropping system is a very important intensive cropping system for food security in China. There have been few studies of the sustainability of yield and accumulation of soil organic carbon(SOC) in the double-rice cropping system following a partial substitution of chemical fertilizer by Chinese milk vetch(Mv). We conducted a 10-year(2008–2017) field experiment in Nan County, South-Central China, to examine the double-rice productivity and SOC accumulation in a paddy soil in response to different fertilization levels and Mv application(22.5 Mg ha~(–1)). Fertilizer and Mv were applied both individually and in combination(sole chemical fertilizers, Mv plus 100, 80, 60, 40, and 0% of the recommended dose of chemical fertilizers, labeled as F100, MF100, MF80, MF60, MF40, and MF0, respectively). It was found that the grain yields of double-rice crop in treatments receiving Mv were reduced when the dose of chemical fertilizer was reduced, while the change in SOC stock displayed a double peak curve. The MF100 produced the highest double-rice yield and SOC stock, with the value higher by 13.5 and 26.8% than that in the F100. However, the grain yields increased in the MF80(by 8.4% compared to the F100), while the SOC stock only increased by 8.4%. Analogous to the change of grain yield, the sustainable yield index(SYI) of double rice were improved significantly in the MF100 and MF80 compared to the F100, while there was a slight increase in the MF60 and MF40. After a certain amount of Mv input(22.5 Mg ha~(–1)), the carbon sequestration rate was affected by the nutrient input due to the stimulation of microbial biomass. Compared with the MF0, the MF100 and MF40 resulted in a dramatically higher carbon sequestration rate(with the value higher by 71.6 and 70.1%),whereas the MF80 induced a lower carbon sequestration rate with the value lower by 70.1% compared to the MF0. Based on the above results we suggested that Mv could partially replace chemical fertilizers(e.g., 40–60%) to improve or maintain the productivity and sustainability of the double-rice cropping system in South-Central China.     

Management of rice straw with relay cropping of Chinese milk vetch improved double-rice cropping system production in southern China

Improved utilization of rice(Oryza sativa L.) straw and Chinese milk vetch(Astragalus sinicus L., vetch) has positive effects on rice production. So far, few studies have investigated the productivity of vetch under different residue management practices in double-rice cropping system. The effects of rice straw on the growth and nutrient accumulation of vetch across seven years(2011–2017) and the subsequent effects of rice straw and vetch on two succeeding rice crops in a vetch–rice–rice cropping system, with the vetch established by relay cropping, were examined. The seven-year double-rice experiment consisted of the following treatments:(1) 100% chemical fertilizer(F-F100);(2) only vetch without chemical fertilizer(M-Con);(3) 80% chemical fertilizer plus vetch plus a low-cutting height(low-retained stubble) with the removal of straw(M-F80);(4) 80% chemical fertilizer plus vetch plus a low-cutting height with the retention of straw(M-F80-LR);(5) 80% chemical fertilizer plus vetch plus a high-cutting height(high-retained stubble) with the retention of straw(M-F80-HR); and(6) no fertilizer(F-Con). The yields of the two rice crops after vetch were not affected by either the cutting height of stubble with retention of straw or by the management of straw(retention vs. removal) with low-cutting height of stubble. The yields of the two rice crops after vetch were significantly higher for M-F80-HR than for M-F80-LR, but the relative contributions of the high-cutting height and straw retention to the higher rice yield could not be determined in this study. The yield stability of the double-rice grain in M-F80-HR was also increased, as determined by a sustainable yield index. Significant increases in vetch biomass and nutrient uptake were observed in the fertilized treatments during the rice season compared with the unfertilized treatments. In M-F80-HR plots, improvements in the growing environment of the vetch by conserving soil water content were associated with the highest vetch biomass, nutrient uptake, and yield stability of vetch biomass. These increased nutrient inputs partially replaced the demand for chemical fertilizer and stimulated the rice yields. It can be concluded that retaining higher-cutting stubble residues with straw retention could be the best straw management practice for increasing the vetch biomass and nutrient use efficiency, thereby allowing utilization of high-cutting height with retention of straw and vetch to improve the stability of rice productivity in a double-rice cropping system.     

3种有机物料对土壤镉有效性及水稻镉吸收转运的影响

种植绿肥、秸秆还田和施用有机肥是稻田土壤有机质提升的主要途径,明确其对土壤镉（Cd）有效性及水稻吸收积累Cd的影响,对于我国南方Cd污染稻田的安全利用具有重要指导意义。采用田间小区试验,设置等量（2 250 kg·hm^-2,干质量）紫云英、油菜秆和有机肥施用处理,通过测定二乙烯三胺五乙酸提取态Cd （DTPA-Cd）、根表铁膜Cd含量和水稻各部位Cd含量,结合土壤理化指标和酶活性变化,对比分析3种有机物料对Cd在土壤-水稻系统迁移转运的影响并探讨其机理。结果表明： 3种有机物料提高了土壤溶解性有机碳（DOC）、有机质含量和水稻产量,增强了土壤过氧化氢酶和纤维素酶活性,在一定程度上增加了根表铁膜量及其Cd吸附量。与CK相比,紫云英、油菜秆和有机肥处理水稻根对Cd的吸收分别增加4.22%、16.99%和38.27%（P<0.05）,Cd由水稻根向稻谷的转运系数和叶向稻谷的转运系数均明显提高,水稻稻谷Cd含量分别显著增加32.67%、39.60%和54.46%（P<0.05）。在Cd污染土壤上施用有机物料虽能提升土壤肥力,但会促进水稻根系对Cd的吸收和向稻谷的转运。因此在南方Cd污染稻田应谨慎施用有机物料,防止由此导致的稻米Cd积累风险。     

氮磷钾肥对紫云英产量、养分累积及种植后土壤养分的影响

通过田间试验,研究了不同配比的NPK肥对紫云英生长、产量、养分累积及土壤养分的影响。研究结果表明:种植紫云英后土壤速效钾、碱解氮、有机质、pH值提高,土壤有效磷下降。施用P2O5在54 kg/hm2内时,紫云英产量随着施磷的增加而增加,并且在早春适当施少量的氮肥(施尿素30 kg/hm2),可以提高紫云英产量。施钾对紫云英产量影响不大,原因有待于进一步研究。     

紫云英翻压还田、后季水稻减量施肥试验

进行每667m^2紫云英鲜草1500kg还田、后季稻减量施用化肥试验,结果表明：在相同紫云英鲜草还田量条件下,减少20％的测土配方推荐施肥量处理的水稻产量最高、效益最好;紫云英鲜草还田后土壤有机质含量提升明显。     

紫云英还田减量施用化肥对水稻产量的影响

通过大田试验研究了翻压紫云英、不同化肥减量水平对水稻生长、产量的影响,结果表明：紫云英翻压后,若不配合施用化肥,后茬水稻产量、经济效益降低;在翻压紫云英、化肥减量40%～60%的条件下,后茬水稻产量、经济效益高于单施化肥处理,其中紫云英＋60%化肥处理水稻产量、经济效益最高,与纯化肥处理相比,水稻增产6.3%,经济效益...     

土壤活性氮动态变化及氮素可利用性对紫云英翻压量的响应

通过田间定位试验,研究了减量化肥紫云英不同翻压量下土壤活性氮的含量、动态变化及氮素可利用性,探讨了紫云英鲜草的适宜翻压量和土壤氮素利用效率,为双季稻合理施用氮肥提供理论依据。在稻-稻-紫云英轮作体系典型时期紫云英翻压前、早稻分蘖盛期、早稻成熟期、晚稻分蘖盛期、晚稻成熟期分别采集土壤样品,监测稻田土壤微生物量氮（MBN）、可溶性有机氮（DON）含量动态变化及氮素可利用性,并分析晚稻成熟期土壤铵态氮（NH₄⁺-N）和硝态氮（NO₃^--N）含量。结果表明：与对照（CK）处理相比,各施肥处理均提高了土壤全氮（TN）、NH₄⁺-N和NO₃^--N含量,增幅分别为10.4%~21.2%、10.3%~44.1%和14.7%~52.9%。在翻压紫云英15.0~22.5 t·hm^-2时,土壤TN、NH₄⁺-N和NO₃^--N含量均随紫云英还田量增多而提高,之后则随还田量的增多而降低。与常规施肥处理相比,化肥减施下紫云英各翻压量处理均提高了土壤MBN、DON及活性氮含量,增幅分别为7.0%~28.7%、8.5%~22.5%和5.8%~26.6%,且随紫云英翻压量的增加呈先增加后降低的变化趋势,MBN和活性氮含量均在翻压量22.5 t·hm^-2时最高,DON含量在翻压量30.0 t·hm^-2时最高。MBN/TN在翻压量22.5 t·hm^-2时最高,DON/TN在翻压量30.0 t·hm^-2时最高。各处理不同时期土壤MBN、DON含量及MBN/TN、DON/TN有明显波动,总体来看,土壤MBN含量及MBN/TN在早稻分蘖盛期明显降低,早稻成熟期有所回升,至晚稻成熟期又逐渐降低;土壤DON含量及DON/TN在早稻成熟期降至最低,至晚稻成熟期再次上升。研究表明,减施40%化肥条件下长期翻压紫云英不仅能增加土壤活性氮含量,同时有利于提高土壤氮素可利用性,紫云英翻压量22.5~30.0 t·hm^-2时效果最好。     

减量施肥下紫云英与稻草协同利用对双季稻产量和经济效益的影响

开展连续5年大田定位试验,研究减量施肥下不同紫云英与稻草利用处理对洞庭湖地区紫潮泥双季稻的产量、产量构成因素及经济效益的影响。结果表明,与单施化肥(F100)相比,不同紫云英、稻草利用处理均能促进水稻增产、稳产,其中紫云英与稻草协同利用的增产效果优于紫云英或稻草单独利用,协同利用处理中又以晚稻高茬稻草还田冬种紫云英(F80+HR+A)处理的效果更好。F80+HR+A处理的早、晚稻,5年平均产量较F100分别增产20.2%、11.9%,稻谷纯收益增加13.7%,边际成本报酬率为3.4元/元。早稻株高、每穗实粒数、千粒质量和晚稻株高、有效穗数、每穗实粒数的增加是水稻增产的主要原因。综上所述,晚稻留高茬还田冬种紫云英,不仅可以提高水稻产量,还可以获得较佳经济收益,减少化肥用量。     

Apparent variations in nitrogen runoff and its uptake in paddy rice under straw incorporation

Straw incorporation is a widespread practice to promote agricultural sustainability. However, the potential effects of straw incorporation with the prolonged time on nitrogen (N) runoff loss from paddy fields are not well studied. The current study addresses the knowledge gap by assessing the effects of straw incorporation on the processes influencing N runoff patterns and its impacts on crop yield, N uptake, total N (TN), and soil organic matter (SOM). We conducted field experiments with rice (Oryzasativa L.)–wheat (Triticumaestivum L.) rotation, rice–tobacco (Nicotianatabacum L.) rotation, and double-rice cropping in subtropical China from 2008 to 2012. Each rotation had three N treatments: zero N fertilization (CK), chemical N fertilization (CF), and chemical N fertilization combined with straw incorporation (CFS). The treatment effects were assessed on TN runoff loss, crop yield, N uptake, soil TN stock, and SOM. Results showed that TN runoff was reduced by substituting part of the chemical N fertilizer with straw N in the double rice rotation, while crop N uptake was significantly (P<0.05) decreased due to the lower bioavailability of straw N. In contrast, in both rice–wheat and rice–tobacco rotations, TN runoff in CFS was increased by 0.9–20.2% in the short term when straw N was applied in addition to chemical N, compared to CF. However, TN runoff was reduced by 2.3–19.3% after three years of straw incorporation, suggesting the long-term benefits of straw incorporation on TN loss reduction. Meanwhile, crop N uptake was increased by 0.8–37.3% in the CFS of both rotations. This study demonstrates the challenges in reducing N runoff loss while improving soil fertility by straw incorporation over the short term but highlights the potential of long-term straw incorporation to reduce N loss and improve soil productivity.     

多年紫云英-双季稻下不同施肥水平对两类水稻土有机质及可溶性有机质的影响

【目的】综合评价中国南方不同水稻土多年冬种紫云英配施化肥的培肥效应。【方法】在湖南紫潮泥、江西黄泥田双季稻区设置了连续7年的田间定位试验,比较冬闲(CK)、紫云英(MV)、紫云英+40%化肥(MV+40F)、紫云英+60%化肥(MV+60F)、紫云英+80%化肥(MV+80F)、紫云英+全量100%化肥(MV+100F)、单施全量100%化肥(100F)共7个处理的稻田土壤有机质(OM)、可溶性有机质(DOM)含量及其光谱学特性。【结果】湖南紫潮泥土壤OM和可溶性有机碳(DOC)含量、DOM的荧光吸光强度明显高于江西黄泥田,可溶性有机氮(DON)含量、DOM的紫外-可见吸收峰值则相反。土壤OM在两地均表现为MV处理显著高于其他多数处理(黄泥田MV+100F处理除外);同100F相比,MV+100F处理降低了湖南紫潮泥、但增加了江西黄泥田的土壤有机质;而绿肥种植体系下随着配施化肥量的增加,绿肥对两类土壤OM的贡献降低。种植绿肥配施80%—100%化肥,土壤DOC含量较100F高(黄泥田MV+100F除外),但单种绿肥(MV)以及绿肥配施40%—60%化肥对两地土壤DOC影响不尽一致。单种植绿肥能够降低两类土壤DOC/SOC,其中,在江西黄泥田上显著低于100F处理;两类土壤上种植翻压绿肥,随着配施化肥量的增加,土壤DOC/SOC随之增加(黄泥田MV+100F除外),表明配施化肥量越高其活化土壤碳库的作用越强。种植绿肥较100F能够有效降低土壤DON含量(黄泥田MV+100F处理除外),且在湖南紫潮泥上更为显著。紫外-可见光谱分析发现,绿肥及绿肥配施40%—60%化肥下,两类土壤DOM的紫外-可见吸收峰值较100F低,且E250/E365值随配施化肥量的增加而降低,表明随着配施化肥量的增加,土壤DOM分子量增大,分子结构越稳定。荧光光谱分析发现,两类土壤可溶性有机质均以类富里酸为主;与100F相比,单种绿肥(MV)以及绿肥配施化肥(黄泥田配施40%—60%化肥)能够增加土壤DOM的荧光强度,降低DOM的腐殖化指数(HIX)。【结论】种植紫云英能有效促进稻田土壤有机质积累,配施化肥降低紫云英对土壤有机质积累的贡献。绿肥配施化肥能够提高土壤碳库活性,并且增加可溶性有机质的分子量及腐殖化程度,进一步解释了配施化肥降低紫云英对土壤碳库贡献。     

延长烤田时间减少紫云英翻压稻田甲烷排放

为明确紫云英翻压还田模式对稻田甲烷（CH₄）排放的影响,同时通过延长烤田时间的优化水分管理措施减少该模式下CH₄的排放,开展了连续5 a的田间定位试验（2016—2020年）,设置4种处理：不施化肥+传统水分管理（分蘖末期排水烤田7 d,CK）、常规单施化肥+传统水分管理（CF）、紫云英翻压+氮肥减施+传统水分管理（MF）、紫云英翻压+氮肥减施+优化水分管理（在传统基础上提前并增加5 d烤田时间,MFW）。结果显示：5 a间MF处理下水稻生长期CH₄排放量为542~658 kg·hm^-2·a^-1,年均排放量相较CK和CF处理分别增加了156%~231%和133%~196%。与MF处理相比,MFW处理使2016、2017年和2019年的第一个CH₄排放高峰期（分蘖期）提前衰减,增加了2018年和2020年CH₄排放的衰减速率,年排放量显著下降了16.2%~28.5%（P<0.05）。与CF处理相比,MF处理下2018、2019、2020年的年产量分别显著增加了6.85%、10.25%和9.79%（P<0.05）,并且MF处理明显降低了产量变异系数并提高了产量可持续性指数。MF和MFW处理下水稻产量没有显著差异。研究表明,紫云英翻压还田具有增产稳产的积极作用,但同时增加了CH₄的排放,而优化后的水分管理措施在保障水稻产量的基础上能够有效减少紫云英翻压稻田CH₄的排放。     

氮钾减施下紫云英翻压量对双季稻产量及氮素利用的影响

采用11年(2008—2018年)绿肥定位试验,研究氮钾减施20%下紫云英不同翻压量(15 000、22 500、30 000、37 500 kg/hm2)对双季稻产量、氮素利用率及土壤氮素的影响。结果表明：与不施肥相比,施肥处理的早、晚稻产量显著增加,产量可持续指数提高,且减施氮钾20%翻压紫云英处理和单施化肥处理间的11年平均产量和产量可持续指数差异均无统计学意义;通过分析2018年的数据,与当地的常规施肥处理相比,减施氮钾20%翻压紫云英30 000 kg/hm2能显著提高早稻生物量、氮素积累量、化肥氮素吸收利用效率(回收利用效率、农学利用效率、偏生产力)和晚稻稻草生物量、稻谷氮素积累量、总投入氮素吸收利用效率(回收利用效率、农学利用效率、生理利用率、偏生产力);适量氮钾减施翻压紫云英可提高土壤全氮和碱解氮质量分数,有效提升土壤肥力。在本研究中,氮钾减施20%时翻压紫云英30 000 kg/hm2较适宜。     

翻压紫云英水稻土游离氨基酸动态及剖面分异

为探讨紫云英翻压后稻田土壤游离氨基酸（FAA）含量和组分的动态变化及其主控因素,阐明稻田土壤FAA的剖面迁移特性,本研究在等氮磷钾的条件下,以单施化肥（CK）为对照,研究了不同施用量紫云英（30 000 kg·hm^-2,CMV1; 45 000 kg·hm^-2,CMV2）翻压后对稻田土壤FAA含量和组成的影响以及其随生育期的波动情况,并阐明FAA在水稻土剖面中的分布特征。结果表明：紫云英翻压后,不同处理稻田土壤FAA含量均呈现出先降低后上升至扬花期达到峰值后再缓慢降低的变化趋势。翻压紫云英可提高土壤FAA含量,CMV1处理和CMV2处理FAA含量均值分别较CK处理显著提高了14.01%和21.75%。不同采样期、不同施肥处理稻田土壤FAA以中性氨基酸含量最高（93.39%~97.52%）,酸性氨基酸次之（2.19%~5.86%）,碱性氨基酸含量最低（0~1.47%）,且均以肌氨酸、甘氨酸、丙氨酸、缬氨酸、异亮氨酸、亮氨酸和苯丙氨酸为主,其合计占FAA总量的65.93%~82.65%。紫云英翻压后FAA具有向下迁移的趋势,主要迁移至20~40 cm土层。中性氨基酸尤其是丝氨酸、甘氨酸和苏氨酸具有较强的迁移性。氨基酸不同组分对土壤性质的响应具有一定差异,中性FAA与土壤pH、有机质、全氮、蛋白酶和细菌拷贝数显著相关,碱性FAA与蛋白酶和细菌拷贝数显著相关,而酸性FAA仅与细菌拷贝数显著相关。研究表明,稻田土壤FAA含量、组成及迁移与紫云英翻压量和水稻生育期密切相关,且对土壤性质的响应有所不同。     

Trends of Yield and Soil Fertility in a Long-Term Wheat-Maize System

The sustainability of the wheat-maize rotation is important to China＇s food security. Intensive cropping without recycling crop residues or other organic inputs results in the loss of soil organic matter （SOM） and nutrients, and is assumed to be non- sustainable. We evaluated the effects of nine different treatments on yields, nitrogen use efficiency, P and K balances, and soil fertility in a wheat-maize rotation system （1991-2010） on silt clay loam in Shaanxi, China. The treatments involved the application of recommended dose of nitrogen （N）, nitrogen and phosphorus （NP）, nitrogen and potassium （NK）, phosphorus and potassium （PK）, combined NPK, wheat or maize straw （S） with NPK （SNPK）, or dairy manure （M） with NPK （M1NPK and M2NPK）, along with an un-treated control treatment （CK）. The mean yields of wheat and maize ranged from 992 and 2 235 kg ha-1 under CK to 5 962 and 6 894 kg ha-1 under M2NPK treatment, respectively. Treatments in which either N or P was omitted （N, NK and PK） gave significantly lower crop yields than those in which both were applied. The crop yields obtained under NP, NPK and SNPK treatments were statistically identical, as were those obtained under SNPK and MNPK. However, M2NPK gave a significant higher wheat yield than NP, and MNPK gave significant higher maize yield than both NP and NPK. Wheat yields increased significantly （by 86 to 155 kg ha-1 yr-1） in treatments where NP was applied, but maize yields did not. In general, the nitrogen use efficiency of wheat was the highest under the NP and NPK treatments; for maize, it was the highest under MNPK treatment. The P balance was highly positive under MNPK treatment, increasing by 136 to 213 kg ha-1 annually. While the K balance was negative in most treatments, ranging from 31 to 217 kg ha^-1 yr^-1, levels of soil available K remained unchanged or increased over the 20 yr. SOM levels increased significantly in all treatments. Overall, the results indicated that combinations of organic manure and inorganic nitrogen, or retuming straw with NP is likely to improve soil fertility, increasing the yields achievable with wheat-maize system in a way which is environmentally and agronomically beneficial on the tested soil.     

稻田土壤氧化态有机碳组分变化及其与甲烷排放的关联性

稻田土壤有机碳是甲烷排放的关键底物之一,不同研究者由于采取的有机碳研究方法不同而得出稻田甲烷排放与土壤有机碳关系的结论不一。为明确影响稻田甲烷排放的土壤有机碳组分,设计了稻田施用不同外源有机碳(稻草还田、鸡粪和猪粪)的田间试验,对稻田甲烷排放和土壤有机碳组分的动态变化及其关联性进行监测和分析。结果表明,猪粪处理的甲烷排放与化肥处理无显著差异,而鸡粪和稻草2个处理的甲烷排放分别比化肥增加1.67倍(P<0.05),2.69倍(P<0.05);甲烷排放量与土壤易氧化有机碳含量显示相同顺序:稻草>鸡粪>猪粪>化肥;通径分析表明,土壤易氧化有机碳组分1(被33 mmol/L KMnO₄氧化的有机碳)与甲烷排放直接相关,其他有机碳组分仅通过组分1间接作用于水稻生育后期甲烷排放,且排放量较低。由此推断,易氧化有机碳组分1是甲烷排放的主要底物,通过有效措施降低肥源中易氧化态有机碳组分1是减排甲烷的关键技术之一。     

修复肥料和紫云英对水稻吸收积累镉的影响

为探讨修复肥料和紫云英对镉污染稻田的修复效果,在大田试验条件下,设置修复肥料和紫云英处理,并与应用较为广泛的石灰进行安全利用效果对比,研究对镉污染稻田水稻不同部位镉吸收转运、有效态镉含量、镉化学形态和酶活性等的影响。结果表明：修复肥料和紫云英联合施用可以使水稻产量较不添加土壤调理剂增产9.01%,施用修复肥料或紫云英也有一定增产效果;修复肥料和紫云英单施及二者联合施用均有效降低糙米镉含量,联合施用的降镉效果最好,达到了28.64%,石灰处理后糙米镉含量也均低于GB 2762—2017限量值;修复肥料和紫云英联合施用水稻根际和非根际土壤pH值分别提高0.20和0.32个单位,效果好于石灰处理（分别提高0.08个和0.23个单位）,修复肥料单施和与紫云英联合施用根际和非根际土壤有效态镉含量分别降低32.25%和40.54%,降镉效果接近石灰处理（27.87%和42.85%）;修复肥料和紫云英联合施用降低了土壤弱酸提取态和可还原态镉含量,提高了残渣态镉含量。此外,修复肥料和紫云英的联合及单独施用在一定程度上提高了土壤蔗糖酶、脲酶、蛋白酶和过氧化氢酶活性;紫云英和修复肥料单施和二者配施的投入产...