Background The contribution of long-term fertilization to soil organic carbon (SOC) storage has been of great concern. To assess the effects of long-term fertilization on SOC storage and stability in top and sub-soil layers, soil samples were collected from a 29-year field experimental station in a typical paddy soil in southern China. The SOC storage of whole soil and SOC fractions was quantified at three soil depths (0–20, 20–40, 40–60 cm) under four treatments: no fertilization (Control), a combination of nitrogen, phosphorus and potassium (NPK), double the rates of NPK (2NPK), NPK plus manure (NPKM). Results The increase of C input-total was significantly higher than that of SOC storage among different treatments ( p < 0.05), indicating that soil fixation of exogenous carbon is limited. Besides, the SOC accumulation and sequestration rates patterned as NPKM > 2NPK > NPK, and these rates were higher at 0–20 cm depth as compared to other depth intervals. Furthermore, for the whole profile, the SOC storage of active pool was higher in the Control (39.6 t C ha −1 ) than in other treatment (36.2 t C ha −1 , p < 0.05). Whereas, fertilization increased the SOC storage of passive pool, ranked as NPKM > 2NPK≈NPK > Control ( p < 0.05), indicating that fertilization, especially organic combined with inorganic fertilization, improved SOC stability. From the perspective of soil layers, the difference of SOC storage among treatments for passive pool was mainly resulted from the difference at surface soil, and for active pool were the deeper layers. Additionally, manure application increased the difference among soil layers. Conclusion This study concluded that non-fertilized treatment could improve the SOC storage of active pool especially in deep soil layers, while fertilization especially manure application could improve the SOC storage and stability in surface soil and increased the difference among soil layers. Graphical Abstract

Abstract Background The contribution of long-term fertilization to soil organic carbon (SOC) storage in arable soils is well acknowledged. The present study soil samples were collected from a 29 years long field trial in a red paddy soil of Jiangxi province, southern China to assess the effects of long-term fertilization on SOC storage and stability in top and sub-soil layers. The SOC storage of whole soil and SOC fractions were quantified at three soil depths (0–20, 20–40, 40–60 cm) under four treatments: no fertilization (Control), a combination of nitrogen, phosphorus and potassium (NPK), double the rates of NPK (2NPK), NPK plus manure (NPKM). Results The results showed that the effect of inorganic fertilizer application on SOC storage across the soil profile (0–60 cm) was negligible except for the 2NPK treatment. The larger SOC storage of the Non-labile C fraction was observed in the 2NPK (25.0 t C·ha− 1) and NPKM (23.8 t C·ha− 1) treatments compared to other treatments, and the NPKM treatment significantly (p < 0.05) accreted the SOC storage of less-labile C fraction by 46.7% averagely compared to other treatments. Besides, the SOC storage of passive pool (less-labile C + non-labile C) under NPKM was 30.7% higher than that in the Control. This was further supported by the higher proportion of passive than active pool indicating that fertilization, especially organic combined with inorganic fertilization, improved soil C stability. Additionally, the effect of different fertilization on SOC storage was mainly reflected in the surface soil, while very weak in the deeper soil as revealed by the stratification ratio and C sequestration rate. Conclusion Inorganic fertilizer combined with organic fertilizer have the ability to increase the storage and stability of SOC which further depend on annual C input and differences in soil depths. Taken together, in red paddy soil, the current fertilization had a significant effect on changing the dynamics of SOC in the topsoil, but a weak effect on the subsoil.

江西省作为我国重要的鱼米之乡,除了生产稻米之外,也适宜种植大豆等豆类作物.为有序指导江西省的豆类产业发展,分别从豆类资源、种植模式、品种和豆制品等方面对全省豆类产业的发展现状进行概述,系统分析了目前存在的主要问题并进行了因素分析.在此基础上,提出了加大政府引导和扶持力度、改善旱地基础设施、多途径扩大大豆面积和调整结构拓展大豆种植等对策,以期促进江西省豆类产业的振兴.

The storage of soil organic carbon (SOC) in cropland soils is an essential strategy that serves the dual purpose of enhancing soil fertility and mitigating climate change. However, how the stability of stored carbon is altered under long-term fertilization has not been well understood, especially in the double rice cropping system in Chinese paddy soils. In this study, we explored the SOC storage and consequent stability of SOC under long-term fertilization. The soil samples were fractionated chemically to isolate various fractions and constituent pools of SOC (i.e., very labile C/VLC, labile C/LC, less labile C/LLC, and non-labile C/NLC). The following treatments were tested: control (CK), recommended rate of inorganic fertilizer (NPK), double the amount of recommended rate of inorganic fertilizer (2NPK), and NPK combined with manure (NPKM). The results showed that, relative to the initial level, the application of NPKM significantly improved the SOC storage as compared to the control. The long-term NPKM increased the total SOC in the paddy soil and this increased SOC was mainly stored in LLC, as revealed by the highest increase (142%) over the control. Furthermore, the highest proportion of labile pool was associated with unfertilized CK, while the reverse was true for the recalcitrant pool, which was highest under NPKM. This supports the role of combining manure with NPK to improve the stability of SOC, further verified by the high recalcitrance index under NPKM (56.75% for 0–20 cm and 57.69% for 20–40 cm) as compared to the control.

覆盖还田是处理香根草(Vetiveria zizanioides L.)秸秆的有效途径之一,但是,关于香根草秸秆覆盖还田下红壤花生的化肥减施比例还缺乏研究.通过2018—2019年的田间试验,分析了无香根草秸秆覆盖和农民习惯施肥(CK)、香根草秸秆覆盖下化肥减施0％(T1)、10％(T2)、20％(T3)和50％(T4)处理下花生产量和土壤有机碳的变化规律,探讨了土壤有机碳与花生产量的量化关系,并进一步研究了外源投入碳氮比与花生产量及土壤有机碳的相关关系.结果表明:与CK相比,T1处理下花生产量在2018和2019年分别增加了15.41％和25.87％;T2和T3处理的花生产量与CK处理无显著差异,且香根草连续两年覆盖下,T4处理的花生产量也与CK处理相比无显著降低.与CK处理相比,香根草秸秆覆盖还田和化肥减施处理下土壤有机碳含量增加了4.27％—12.84％.同时,在香根草秸秆覆盖下,随着化肥减施比例的提高,土壤有机碳含量呈逐渐降低趋势.结合拟合方程的斜率发现,当土壤有机碳含量增加1 g·kg-1,2018和2019年花生产量增加934.62和903.31 kg·hm-2.提高外源投入的碳氮比显著降低花生产量和土壤有机碳含量,且双直线方程表明,外源投入碳氮比大于4.28时,花生产量和土壤有机碳的降幅明显高于外源投入碳氮比小于4.28.因此,在红壤的花生种植中,连续进行两年的香根草秸秆覆盖还田可以提高花生产量,且在化肥减施10％-50％条件下,花生产量与农民习惯处理无显著降低.然而,在增加外源有机碳的同时,也要综合考虑外源投入的碳氮比,以期保障花生高产和土壤有机碳提升.

Understanding the impact of biological activities on the soil phosphorus (P) distribution under long-term fertilizer application can facilitate better soil P fertility management. Therefore, the primary objectives of this study were to investigate the effect of long-term (since 1981) fertilizer application on the soil P fractions and microbial community and to evaluate correlations between the microbial community structure and P distribution. The following treatments were implemented in a long-term field trial: no fertilization (CK), inorganic N and K (NK), inorganic P and K (PK), inorganic N, P and K (NPK) and manure+NPK (MNPK) fertilization. The study showed that the soil pH, soil organic carbon and total and available N and P concentrations were considerably higher in the MNPK treatment than in the CK treatment. The soil microbial biomass C, N and P concentrations were also significantly higher in the MNPK treatment than in the CK treatment. Among fertilization treatments, the β-1,4-glucosidase, α-1,4-glucosidase, urease, acid phosphatase and phosphodiesterase activities were the highest in the MNPK treatment. Compared to inorganic fertilization, the MNPK treatment increased the labile soil P fractions and decreased the residual soil P concentration. Continuous fertilization significantly affected the soil microbial composition. The total phospholipid fatty acid (PLFA) concentrations in the NK, PK, NPK and MNPK treatments were 23.3, 43.1, 48.7 and 87.7% higher, respectively, than in the CK treatment. A significant correlation was observed between the microbial community and soil P fractions. Moreover, the aggregated boosted tree (ABT) model showed that among the various soil biochemical properties, the total PLFA concentration was the factor that most influenced the active P pool, accounting for 35.4% of the relative influence of all soil biochemical properties examined. These findings reveal that combined manure and inorganic fertilizer application is a better approach than applying inorganic fertilizer alone for sustaining long-term P fertility by mediating soil biological activity.

水田土壤反硝化势(soil denitrification potential,SDP)往往高于旱地土壤,但施肥对水田和旱地SDP的影响差异往往基于不同气候条件下的不同土壤类型获取,其准确性可能受外界条件干扰.以发育自同一母质的相邻水田和旱地长期试验为平台,比较不同施肥模式下水田和旱地SDP的变化及其与功能基因(narG、nirS、nirK和nosZ)丰度及nirS-型反硝化细菌群落组成之间关系的异同.结果表明,在水田中,与常规氮磷钾平衡施肥(NPK处理)相比,缺钾(NP处理)和缺氮(PK处理)的SDP分别提高33.01％和23.57％,而缺磷(NK处理)则降低35.76％,其中NP和NK处理的SDP变化与nirS基因丰度显著相关.这可能与施肥导致的土壤有效磷和氮/磷变化有关,而PK处理的SDP变化与nirS-型反硝化细菌Azospira sp.NC3H-14丰度的显著升高有关.在旱地中,与NPK处理相比,NP、NK和缺氮钾的P处理SDP分别提高13.94％、26.51％和25.41％,NK和P处理的SDP变化既与narG基因丰度显著增加相关,也与不同的nirS-型反硝化细菌丰度增加有关,其中NK处理与Azospira sp.NC3H-14和Ideonella sp.NC3L-43b丰度增加有关,P处理与Azospira sp.NC3H-14、Rhodanobacter sp.D206a和Rubrivivax gelatinosus丰度增加有关;而土壤无定形氧化铁含量的变化可能是影响narG基因丰度的主要因素.直接比较相同环境条件下的水田和旱地结果可以发现,水田中施肥导致的SDP变化主要与反硝化微生物群落组成变化有关,而旱地中则可能同时受制于功能基因和反硝化微生物群落组成的变化.

[目的]探究不同有机培肥条件下稻田土壤病毒多样性、群落结构特征及其差异,为揭示病毒与寄主协同进化关系,以及病毒微生态系统驱动生物地球碳循环过程提供理论基础.[方法]长期定位试验开始于1981年,试验设置6个处理,每处理3次重复,试验处理分别为:(1)CK,不施肥;(2)NPK,单施化肥;(3)M1,早稻施绿肥;(4)M2,早稻施绿肥+早稻施猪粪;(5)M3,早稻施绿肥+晚稻施猪粪;(6)M4,早稻施绿肥+晚稻秸秆还田.2020年晚稻收获后,采集耕层(0～20 cm)土壤,通过宏病毒组测序平台、土壤常规理化分析等方法测定土壤宏病毒组以及土壤养分含量.[结果]红壤区稻田土壤病毒分布于37个科,微小病毒科(Microviridae)是红壤区稻田土壤主要的病毒类群.M3处理中长尾病毒科(Siphoviridae)、肌病毒科(Myoviridae)和痘病毒科(Poxviridae)丰度显著高于其他处理(P<0.05,下同),M2处理中微小病毒科和矮化病毒科(Nanoviridae)丰度显著高于其他处理.通过稻田土壤病毒宏基因组基因注释,鉴定出143个独特碳水化合物的运输和代谢基因,46个开放阅读框属于13种病毒辅助碳水化合物活性酶(CAZyme),其中糖苷水解酶最丰富,约占61.7％,其次为糖基转移酶.土壤病毒物种丰富度可在一定程度反映土壤pH、Mg2+含量和水稻产量的高低,病毒群落结构受pH、Mg2+含量等其他因素驱动.[结论]微小病毒科是红壤区稻田土壤主要的病毒类群,施用猪粪可显著提高土壤病毒群落结构和物种组成,病毒群落结构受土壤pH和Mg2+含量的显著影响.通过稻田土壤病毒宏基因组基因注释,在病毒体中检测到丰富的碳水化合物活性酶基因,主要分别属于糖苷水解酶类和糖苷转移酶,病毒编码的辅助代谢基因或代谢基因会改变细菌代谢,间接促进农业土壤的生物地球碳化学循环.

Understanding the relationships among phosphorus (P), soil organic carbon (SOC) and aggregate stability is vital for improving soil fertility and P and C cycling in different land-use types. Here, we assessed the responses of SOC distribution in different aggregate fractions to P addition in two different land-use types categorized in either a P-limitation or non-P-limitation status based on the stoichiometric ratios of microbial enzymes. Four different long-term fertilization managements (no fertilizer [control, non-P limitation]; nitrogen and potassium [NK treatment, P limitation]; phosphorus [P treatment]; and nitrogen, phosphorus, and potassium [NPK treatment]) were established in upland and paddy soils to compare the effects of pre-assessed non-P- and P-limited soil conditions in combination with different fertilizer additions. A wet-sieving method was used to obtain four sizes (> 2-, 0.25–2-, 0.053–0.25- and < 0.053-mm) of soil aggregates. The concentrations of SOC and iron and aluminum (Fe/Al) oxides in the forms extractable by DCB (Fed/Ald), oxalate (Feo/Alo) and polyphosphate decahydrate (Fep/Alp) were measured. The results showed that compared to the non-P-limited control, the P treatment reduced soil mean weight diameter (MWD) by 13.1% in upland and 9.7% in paddy soils. The MWD of NPK treatment was significantly higher by 24% than that of the P-limited NK treatment in upland soil, while the difference between the same two fertilization treatments was not significant in paddy soil. Compared with that of the control, SOC concentration in each size was greater in the P-treated upland soil, while in the paddy soil, SOC concentration of the >2-mm size were lower in the P and NPK treatments than in the control and NK treatments, respectively. Phosphorus addition decreased Fep/Alp of each aggregate size in upland soil, while it increased Fep/Alp of each aggregate size in paddy soil. To better quantify the effects of P on SOC and aggregate stability, we used a partial least squares path model (PLS-PM). The results indicated that P addition had a direct negative effect on MWD (−0.797, P < 0.01) under the non-P limitation condition (control vs. P treatment). The addition of P in upland soil had a high positive effect on MWD (0.565, P < 0.05) under the P-limitation condition (NK vs. NPK treatments), but the effect was not significant in paddy soil (0.047, P > 0.05). Thus, strategies aiming to improve soil carbon cycling and aggregate stability by regulating phosphorus addition should consider land-use type and soil P-limitation status.

The supposition that cropping system might affect fertilization-induced changes in chemical composition of soil organic carbon (SOC) and microbial community composition has mostly derived from field experiments in different sites, which may have been disturbed by different climate conditions and parent materials. Here, two adjacent long-term field experiments were used, which contained similar four fertilization regimes of NPK, 2NPK, NPKOM, and an unamended control (Control), while contrasting annual cropping system of rice-rice and maize-maize, to investigate how fertilization-induced changes in SOC chemistry differ in paddy soil from upland soil, and whether they correlate with different bacterial taxa. The bacterial community composition of the paddy soil was mainly determined by NO3--N and total N, and that of the upland was mostly explained by SOC. The NPK, 2NPK, and NPKOM treatments from the paddy soil increased CCH3, decreased OCH, and reduced CH/CH2, while those from the upland soil decreased CH/CH2, increased OCH, and raised CH/CH2, respectively, indicating opposite shifts of OCH and alkyl C (i.e., CCH3 and CH/CH2) in each paired fertilizer treatment of the two soils. In the paddy soil, the CCH3 from the NPK treatment showed no association with any bacterial taxa, the OCH from the 2NPK showed a negative association with NO3-related species, and the CH/CH2 from the NPKOM showed a negative association with Pmteobacteria and Bacteroidetes. In the upland soil, the CH/CH2 from the NPK negatively associated with Thermogemmatisporales and Acidobacteriaceae subgroup 1, the OCH from the 2NPK positively associated with Thermogemmatisporales, and the CH/CH2 from the NPKOM positively associated with copiotrophic bacterial taxa. Our results provided direct evidence that cropping system mediated the shift direction of specific functional group under specific fertilization regimes, and implied that completely opposite shifts of OCH and alkyl C in each paired fertilizer treatment of the paddy soil and upland soil can likely be attributed to different fertilization-induced shifts in the microbial community composition resulting from soil N change in the paddy soil and soil C change in the upland soil.

[目的]紫云英(Astragalus sinicus L.)是双季稻冬闲期重要的绿肥作物,长期进行紫云英翻压还田可以实现土壤培肥和水稻增产的双重目标.但是,在众多的土壤理化指标中,有关紫云英不同翻压年限下驱动水稻产量变化的关键因子还不明确.[方法]本研究在紫云英传统种植区(江西省余江区),选择紫云英翻压时间为0、3、5、10和15年(G0、G3、G5、G10和G15)的稻田,分析了土壤团聚体、有机质、氮磷钾养分含量和土壤酸化特征,并进一步探讨了土壤理化指标与早稻产量的相关关系.[结果]G5、G10和G15处理下,>2 mm团聚体组分的比例显著高于G0 和G3 处理.紫云英翻压年限越长,土壤有机质?全氮磷和速效氮磷钾及缓效钾含量越高.与G0 处理相比,G10 和G15 处理下土壤pH 提高了0.83 和0.65 个单位,且G15 处理下土壤交换性酸/氢铝含量均显著低于G0 处理.比较相关系数,在所有指标中,>2 mm 团聚体组分的比例?土壤有机质?速效氮含量与籽粒产量的相关性较高(R2 均大于0.8,P<0.01).通径分析结果表明,紫云英翻压年限显著影响团聚体和有机质及养分指标,进而影响水稻产量.[结论]在双季稻区,长期紫云英翻压还田是实现土壤培肥和早稻增产的关键途径.紫云英翻压达到10 年以上时,稻田土壤酸化得到明显改善.翻压年限对土壤大团聚体组分的影响程度较高,而土壤有机质和速效氮含量则是调控水稻产量变化的关键因素.

[目的]提高土壤有机碳水平对提升农田生产力有重要意义.基于长期定位施肥试验,比较施肥影响下相同成土母质发育的红壤性稻田和旱地土壤的总有机碳(TOC)及其组分的积累差异,以深入理解红壤有机碳的固持及稳定机制.[方法]稻田和旱地长期施肥试验分别始于1981和1986年,包含CK(不施肥对照)、NPK(施氮磷钾化肥)和NPKM(有机无机肥配施)3个处理,在2017年晚稻和晚玉米收获后,采集两个试验上述处理的耕层(0—20 cm)土样,通过硫酸水解法分离土壤活性与惰性有机碳,测定并计算土壤中TOC及其组分的含量及储量,并利用Jenny模型拟合试验期间耕层土壤TOC含量的变化动态,估算土壤固碳潜力.[结果]与CK相比,长期施肥可提高稻田和旱地土壤各有机碳组分的含量,且NPKM处理的效果优于NPK处理.相比于稻田土壤,施肥对旱地土壤各有机碳组分含量的提升更加明显.NPK和NPKM处理下,旱地土壤活性有机碳组分Ⅰ、活性有机碳组分Ⅱ、惰性有机碳含量的增幅分别是稻田土壤的2.7、2.7、5.8倍和2.0、1.4和2.5倍.不论施肥与否,稻田土壤TOC的固存量和固存潜力均显著高于旱地土壤.施肥促进土壤固碳,在稻田和旱地土壤上,NPKM处理的TOC固存量分别是NPK处理的1.7和25.5倍,TOC固存潜力则分别是NPK处理的1.4和5.8倍.长期不同施肥均显著提高稻田和旱地土壤年均碳投入量,线性拟合方程表明,随碳投入量增加,土壤活性有机碳储量的累积对稻田、旱地土壤TOC储量累积的贡献率分别达64.7％、44.6％.不同处理间稻田与旱地土壤活性有机碳(包括活性有机碳组分Ⅰ与活性有机碳组分Ⅱ)含量的差异可解释其TOC含量差异的52.9％～60.0％.[结论]与施氮磷钾化肥相比,有机无机肥配施可更好的促进土壤固碳,且在旱地土壤上的促进作用比在稻田土壤上更为明显.与稻田土壤相比,旱地土壤各有机碳组分含量的变化对长期施肥的响应更敏感,且在施氮磷钾化肥条件下表现更为明显.红壤性稻田和旱地土壤TOC积累的主要贡献组分分别为活性有机碳和惰性有机碳.红壤植稻虽有利于有机碳固持,但红壤性稻田土壤的活性碳占比较高,可能易因不当管理而发生损失.

[目的]以40年红壤长期有机培肥试验为研究平台,探究长期施用紫云英、猪粪及秸秆还田对稻田土壤有机碳组分、土壤微生物量及水稻产量的影响.[方法]设置6个处理:不施肥处理(CK)、化肥处理(NPK)、早稻施绿肥紫云英处理(M1)、早稻施绿肥紫云英和早稻施猪粪处理(M2)、早稻施绿肥紫云英和晚稻施猪粪处理(M3)、早稻施绿肥紫云英和晚稻秸秆还田处理(M4).于2020年晚稻收获前采集耕作层(0～20 cm)土壤样品,测定土壤有机碳组分、微生物量碳氮等肥力指标.[结果](1)长期有机培肥处理提高了水稻产量,较不施肥处理CK相比,绿肥紫云英添加猪粪的M2、M3处理早稻产量,分别提高1.4、1.25倍,晚稻产量则分别提高0.59、0.65倍;绿肥紫云英添加猪粪的M2、M3处理早稻产量,较化肥NPK处理分别提升18.1％、10.6％,晚稻产量分别提升15.7％、20.0％.(2)长期有机培肥处理提高了各形态土壤有机碳组分含量,早稻绿肥紫云英+猪粪的M2处理较不施肥CK处理显著提高易氧化性有机碳、游离态颗粒有机碳、可溶性有机碳含量(P<0.05),且有机碳各组分含量均高于化肥NPK处理,其中游离态颗粒有机碳含量M2处理(0.97 g·kg-1)显著高于NPK处理(0.68 g·kg-1)(P<0.05);化肥NPK处理和有机培肥处理(M1、M2、M3、M4)土壤微生物量碳较不施肥CK处理相比提高了22.1％～58.9％,早稻绿肥紫云英+猪粪的M2处理土壤微生物量碳含量(231.2 mg·kg-1)最高且提升最为明显(P<0.05).(3)长期有机培肥提高了游离态颗粒有机碳和可溶性有机碳的分配比例,且早稻施绿肥紫云英+猪粪M2处理效果明显;易氧化性有机碳是红壤有机碳的主要存在形式;土壤有机碳与易氧化性有机碳、游离态颗粒有机碳及可溶性有机碳呈极显著正相关关系(P<0.01).(4)长期有机培肥提高了全氮、碱解氮等养分指标,产量与速效磷、有机碳、全氮、速效氮、可溶性有机碳极显著相关(P<0.01),与全磷、游离态颗粒有机碳、易氧化性有机碳显著相关(P<0.05).[结论]长期有机培肥通过提升红壤肥力水平,调增可溶性有机碳含量,促进水稻稳产增产,尤其是紫云英添加猪粪处理模式具有较好的应用潜力.

Fertilization-induced changes in soil properties from the paddy soil and upland soil may directly regulate bacterial community composition, which usually coincide with shifts in molecular composition of soil organic carbon (SOC) in the upland soil. However, systematical comparisons lack on how regulators vary with cropping systems under the same weather conditions and soil parent materials. Here, we simultaneously investigated the changes of soil physicochemical parameters and shifts in the bacterial community and SOC molecular composition in two adjacent rice and maize fields that have received five fertilization regimes for more than 30 years. The separation of the bacterial community composition among the treatments from the paddy soil was mainly determined by soil nitrate-N, and that from the upland soil was mainly determined by soil available P (AP) and pH. The SOC molecular composition from the paddy soil was separated by the treatments with N application or not, with those treatments with N application being enriched with CCH3 and aromatic C-C, and those without N application being enriched with aromatic C-H. These changed C functional groups showed close association with amorphous Fe2O3. For the upland soil, the SOC molecular composition was separated by the treatments with P application or not, with those treatments with P application being enriched with OCH, and those without P application being enriched with CH/CH2. These changed C functional groups had close association with AP and total P. Our results indicated inconsistent separation patterns and regulators of the bacterial community and SOC molecular composition among the treatments of the paddy soil and upland soil, and suggested that the relatively dominant role of the fertilization-induced changes in soil properties or other soil microbes that controlled the SOC molecular composition over the bacteria measured in the present study.

以江西进贤红壤性稻田和旱地长期试验为载体,运用模糊数学及统计学方法进行土壤物理质量综合评价及其演化研究.结果显示,土壤物理质量综合评价筛选指标13个:0.25～0.05 mm、0.05～0.01 mm、0.01～0.005 mm、物理性粘粒、0.25～0.05 mm微团聚体、0.05～0.01 mm微团聚体、<0.001 mm微团聚体、团聚度、>5 mm团聚体、1～0.5 mm团聚体、总团聚体、MWD和团聚体稳定率.土壤物理质量指数(SPI)各施肥处理间显著性差异在旱地达三级(a、b、c),在稻田达二级(A、B);稻田的SPI(0.533)高于旱地(0.519),但整体均较低(0.5～0.6).SPI值表明生产中应平衡施肥(处理NPKM、M和NPK).除CK、N外其它处理的SPI随时间略增,旱地的SPI整体增幅略高于稻田.

通过分析水稻生产现和肥料投入现状,指出影响江西省化肥利用率的主要原因:有机肥施用比例低,土壤基础地力下降,引起酸化、耕层浅薄等次生障碍;化肥施用量高,但氮磷钾比例不合理;施肥方式粗放;栽培管理模式滞后;农民运用新技术新模式的意识薄弱.针对这些影响因素,提出化肥减量增效与水稻高产稳产的建议:加快研究完善双季稻栽培模式下的有机肥周年管理模式;制定有机肥使用补贴政策,带动农民多用有机肥;扶持有机肥生产厂家,保障有机肥的供应量;通过加强宣传教育带动有机肥的科学应用;加强配施缓释肥、根际增氧及养分转化过程调控等新型化肥减量技术和产品的研究与示范应用;鼓励土地流转,以大户和规模经营带动减肥技术的广泛应用.

[目的]玉米(Zea mays L.)生产需要投入大量的钾素营养.研究长期大量投入钾素对玉米钾素吸收利用以及土壤钾素平衡的影响,旨在保障该地区双季玉米的高产高效和土壤钾库平衡.[方法]红壤钾肥长期定位试验位于江西省进贤县,始于1986年,种植制度为一年两季玉米.试验处理包括不施肥对照(CK),氮磷化肥处理(NP),氮磷钾化肥处理(NPK),2倍量的氮磷钾化肥处理(DNPK),氮磷钾化肥+有机肥处理(NPKM)和单施有机肥处理(OM).每季收获后,调查分析玉米产量和钾素含量,以及耕层土壤有效钾含量,计算玉米钾素吸收量、钾肥利用率、钾肥收获指数、钾肥农学效率和土壤钾素表观平衡;并以每10年为一个阶段,分析玉米产量、钾素吸收利用等指标及耕层土壤速效钾含量、钾素表观平衡等的变化规律.[结果]在试验的33年(1986—2018)间,NPK、DNPK、NPKM和OM处理的玉米年均产量和年均吸钾量均显著高于NP处理.在试验的第一个10年(1986—1995年)间,各钾肥处理间玉米产量和吸钾量无显著差异;而在第3个10年(2006—2015)和后3年(2016—2018年)间,NPKM处理的玉米年产量和年吸钾量分别比NPK处理提高了129.9％～246.7％和55.2％～62.1％.33年玉米的年均钾肥利用率以OM处理最高,而DNPK处理显著低于其他处理.在2006—2015和2016—2018年,NPKM处理的钾肥利用率显著高于DNPK处理,在2016—2018年间分别比NPK和DNPK处理显著增加了56.0％和119.2％.与NPK处理相比,1996—2005、2006—2015和2016—2018年间NPKM处理的年钾肥收获指数分别提高了61.6％、53.5％和35.8％,年钾肥农学效率分别增加了23.3％、227.8％和445.5％.除了1986—1995年间OM处理土壤钾素为亏缺外,其他施钾处理的土壤钾素均为盈余,NPKM处理的钾盈余量比NPK处理增加了53.2％～211.6％.钾素盈余量与耕层土壤速效钾含量显著相关(P<0.001),钾素盈余量每增加1 kg/hm2,2016—2018年间耕层土壤速效钾含量增加2.60 mg/kg,明显高于1996—2005和2006—2015年的1.40和1.18 mg/kg.[结论]除前10年的单施有机肥处理外,其他施用钾肥处理在试验期间土壤钾素均处于盈余状态,钾肥施用量和钾肥来源对玉米钾素的吸收量没有显著影响.试验20年之后,有机无机肥配施对玉米产量、吸钾量和钾肥利用率的提升优势逐渐凸显.同时,长期施用钾肥导致的钾素盈余量增加会进一步提升耕层土壤速效钾含量,且随着试验年限的延长,钾素盈余量对耕层土壤速效钾的提升作用逐渐增加.

清洁生产是以实现资源高效利用、物质循环利用、污染物阻断减毒等为目的的生产技术体系,是实现农业绿色可持续发展的重要途径.本文在综合有关清洁生产技术原理的基础上,结合近年来从事水稻清洁生产技术研究和应用的实际,分析了水稻清洁生产技术的背景意义,提出了双季稻清洁生产的概念、原理、控制路径和主要技术,并结合生产实践比较了水稻清洁生产技术的应用效果和前景.

在南方红壤区,研究长期施肥下土壤解钾菌的变化规律及其驱动因素,可为该地区土壤钾素资源管理和钾肥合理施用提供理论依据.基于红壤旱地长期定位施肥试验(始于1986年),选取不施肥(CK)、施氮磷肥(NP)、氮磷钾肥(NPK)和氮磷钾肥配施有机肥(NPKM)处理,分析玉米开花期根际土壤的解钾菌类型和解钾能力及其有机酸和激素含量,并结合玉米根系特性和根际土壤理化性质探讨影响红壤旱地解钾菌变化的关键因子.结果表明:与NPK处理相比,NPKM处理的根长、根表面积、根直径和根体积分别增加了112.3％、174.4％、32.43％和291.5％,根际土壤pH提高了0.67个单位,有机质、非交换性钾和交换性钾分别增加了29.50％、19.34％和53.89％.各施肥处理根际土壤中均存在解钾菌,CK和NP处理的解钾菌均为类芽孢杆菌属,NPK和NPKM处理则均为纤维菌属.与CK处理相比,NP、NPK和NPKM处理下根际土壤解钾菌的解钾效率分别增加了162.4％、139.0％和105.6％,其中NP处理解钾菌的解钾效率最高.偏最小二乘路径模型的结果显示,根系和施肥可同时调控解钾菌的解钾效率.冗余分析(RDA)进一步表明,根系长度和表面积与土壤解钾菌特性呈显著正相关关系(P<0.05).因此,红壤旱地长期不同施肥措施不仅直接影响玉米根系发育特征和根际土壤理化性质,还能显著改变土壤解钾菌群落及其解钾能力,其中根系长度和表面积是调控玉米根际土壤中解钾菌的关键因子.

Soil pH adjusted by the application of lime can improve soil potassium (K) availability to meet crop K uptake in acidic red soil. However, the response of aggregated K to pH changes is poorly understood. Objectives of this study was to quantify the relationships between aggregate K content and pH levels in soil with different fertilization patterns from a long-term field experiment Then, an incubation experiment of pH adjustment was conducted over 90 days at different pH levels where HCl and Ca(OH)(2) were added to nitrogen and phosphorus fertilizers (NP); NP and K fertilizers (NPK); and NPK with manure (NPKM) soils. Our results showed that double linear equations can fit the relationships between aggregate exchangeable K (EK) with pH levels. However, the slopes and other parameters of fitted equations varied among different fertilization soils. Linear equations indicated that increasing pH value could improve non-exchangeable K (NEK) contents of soil aggregates, especially in NP soil with lower initial pH. However, the proportions of EK and NEK stocks in soil aggregates were significantly changed by soil pH adjustment only in NPKM soil. Additionally, redundancy analysis and partial least squares path mode also suggested that soil pH only affected the NEK contents in soil aggregates, although fertilization had direct effects on the EK and NEK contents in soil aggregates. Therefore, this study demonstrated that the aggregate K distribution of adjusting pH varied among soils with different fertilization regimes, then, improved soil pH could maintain high EK and NEK content of soil aggregates in red soil.