Response of soil Olsen-P to P budget under different long-term fertilization treatments in a fluvo-aquic soil

The concentration of soil Olsen-P is rapidly increasing in many parts of China, where P budget(P input minus P output) is the main factor influencing soil Olsen-P. Understanding the relationship between soil Olsen-P and P budget is useful in estimating soil Olsen-P content and conducting P management strategies. To address this, a long-term experiment(1991–2011) was performed on a fluvo-aquic soil in Beijing, China, where seven fertilization treatments were used to study the response of soil Olsen-P to P budget. The results showed that the relationship between the decrease in soil Olsen-P and P deficit could be simulated by a simple linear model. In treatments without P fertilization(CK, N, and NK), soil Olsen-P decreased by 2.4, 1.9, and 1.4 mg kg^(–1) for every 100 kg ha^(–1) of P deficit, respectively. Under conditions of P addition, the relationship between the increase in soil Olsen-P and P surplus could be divided into two stages. When P surplus was lower than the range of 729–884 kg ha^(–1), soil Olsen-P fluctuated over the course of the experimental period with chemical fertilizers(NP and NPK), and increased by 5.0 and 2.0 mg kg^(–1), respectively, when treated with chemical fertilizers combined with manure(NPKM and 1.5 NPKM) for every 100 kg ha^(–1) of P surplus. When P surplus was higher than the range of 729–884 kg ha^(–1), soil Olsen-P increased by 49.0 and 37.0 mg kg^(–1) in NPKM and 1.5 NPKM treatments, respectively, for every 100 kg ha^(–1) P surplus. The relationship between the increase in soil Olsen-P and P surplus could be simulated by two-segment linear models. The cumulative P budget at the turning point was defined as the "storage threshold" of a fluvo-aquic soil in Beijing, and the storage thresholds under NPKM and 1.5 NPKM were 729 and 884 kg ha^(–1)P for more adsorption sites. According to the critical soil P values(CPVs) and the relationship between soil Olsen-P and P budget, the quantity of P fertilizers for winter wheat could be increased and that of summer maize could be decreased based on the results of treatments in chemical fertilization. Additionally, when chemical fertilizers are combined with manures(NPKM and 1.5 NPKM), it could take approximately 9–11 years for soil Olsen-P to decrease to the critical soil P values of crops grown in the absence of P fertilizer.

Long-term organic and inorganic fertilizations enhanced basic soil productivity in a fluvo-aquic soil

The improvement of soil productivity depends on a rational input of water and nutrients, optimal field management, and the increase of basic soil productivity（BSP）. In this study, BSP is defined as the productive capacity of a farmland soil with its own physical and chemical properties for a specific crop season under local field management. Based on 19-yr data of the long-term agronomic experiments（1989–2008） on a fluvo-aquic soil in Zhengzhou, Henan Province, China, the decision support system for agrotechnology transfer（DSSAT ver. 4.0） crop growth model was used to simulate yields by BSP of winter wheat（Triticum aestivium L.） and summer maize（Zea mays L.） to examine the relationship between BSP and soil organic carbon（SOC） under long-term fertilization. Five treatments were included：（1） no fertilization（control）,（2） nitrogen, phosphorus and potassium fertilizers（NPK）,（3） NPK plus manure（NPKM）,（4） 1.5 times of NPKM（1.5NPKM）, and（5） NPK plus straw（NPKS）. After 19 yr of treatments, the SOC stock increased 16.7, 44.2, 69.9, and 25.2% under the NPK, NPKM, 1.5NPKM, and NPKS, respectively, compared to the initial value. Among various nutrient factors affecting contribution percentage of BSP to winter wheat and summer maize, SOC was a major affecting factor for BSP in the fluvo-aquic soil. There were significant positive correlations between SOC stock and yields by BSP of winter wheat and summer maize（P〈0.01）, and yields by BSP of winter wheat and summer maize increased 154 and 132 kg ha^（–1） when SOC stock increased 1 t C ha^（–1）. Thus, increased SOC accumulation is a crucial way for increasing BSP in fluvo-aquic soil. The manure or straw combined application with chemical fertilizers significantly enhanced BSP compared to the application of chemical fertilizers alone.

Acid and Alkali Buffer Capacity of Typical Fluvor-Aquic Soil in Huang-Huai-Hai Plain

Soil acid and alkali buffer capacity, as a major indicator for evaluating its vulnerability and resistibility to acidification and alkalization, is an important factor affecting the sustainable agriculture, through knowledge on which soil acidification process can be predicted and modified. In this study, titration curve method was adopted to investigate the pH buffer capacity （pHBC） of fluvor-aquic soil, and separate titration curves were established by adding incremental amounts of either standardized hydrochloric acid （HC1） （0.12 mol L^-1） or sodium hydroxide （NaOH） （0.10 mol L^-1） to soil suspended in deionized water （soil：solution = 1：5）. Soil pH was measured after 7 d resuspension and isothermal equilibrium （T = 25℃）. Linear regressions were fitted to the linear portion of each titration curve and the slopes of these lines were derived as the soil pHBC. The results showed that significant correlations between the amounts of adding acid or alkali and each pH change were presented, and titration curve method was feasible for measurement of pHBC on typical fluvor-aquic soil in Huang-Huai-Hai Plain, and the coefficients of determination were higher than the similar researches on acid soil （R^2 = 0.96）. The slope-derived pHBC of acid and alkali were 158.71 and 25.02 mmol kg^-1, respectively. According to the classification of soil buffer systems, the soil tested belongs to the calcium carbonate buffer system, carbonates contribute the most to pHBC, and the contribution of soil organic matter relatively less than it.

K^+ Adsorption Kinetics of Fluvo-Aquic and Cinnamon Soil Under Different Temperature

The K+ adsorption kinetics of fluvo-aquic soil and cinnamon soil under different temperatureswere studied. The results showed: 1) The first order equations were the most suitable forfitting the adsorption under various temperature levels with constant K+ concentration indisplacing fluid. With temperature increasing, the fitness of Elovich equation increased,while those of power equation and parabolic diffusion equation decreased; 2)the apparentadsorption rate constant ka and the product of ka multiplied by the apparent equilibriumadsorption qincreased when temperature increased, while the apparent equilibrium adsorptionqreduced; 3)temperature influenced hardly the reaction order, the order of concentrationand adsorpton site were always 1 under various temperatures, if they were taken intoaccount simultaneously, the adsorption should be a two-order reaction process; 4)theGibbs free energy change △G of potassium adsorption were negative, ranged from -4444.56to -2450.63Jmol-1,and increased with temperature increasing, while enthalpy change △H,entropy change △S, apparent adsorption activation Ea, adsorption activation energy E1and desorption activation energy E2 were temperature-independent; 5)the adsorption wasspontaneous process with heat releasing and entropy dropping, fluvo-aquic soil releasedmore heat than cinnamon soil.

Vertical variation and storage of nitrogen in an aquic brown soil under different land uses

The vertical variation and storage of nitrogen in the depth of 0-150 cm of an aquic brown soil were studied under 14 years of four land use patterns, i.e., paddy field, maize field, fallow field and woodland in Shenyang Experimental Station of Ecology, Chinese Academy of Sciences in November of 2003. The results showed that different land uses had different profile distributions of soil total nitrogen (STN), alkali N, ammonium (NH4+-N) and nitrate (NO3--N). The sequence of STN storage was woodland >maize field > fallow field > paddy field, while that of NO3--N content was maize field > paddy field > woodland > fallow field, suggesting the different root biomass and biological N cycling under various land uses. The STN storage in the depth of 0-100 cm of woodland averaged to 11.41 thm-1, being 1.65 and 1.25 times as much as that in paddy and maize fields, respec-tively, while there was no significant difference between maize and fallow fields. The comparatively higher amount of NO3--N in maize and paddy fields may be due to nitrogen fertilization and anthropogenic disturbance. Soil alkali N was significantly related with STN, and the correlation could be expressed by a linear regression model under each land use (R20.929, p<0.001). Such a correlation was slightly closer in nature (woodland and fallow field) than in agro ecosystems (paddy and maize fields). Heavy N fertilization induced an excess of crop need, and led to a comparatively higher amount of soil NO3--N in cultivated fields than in fallow field and woodland. It is suggested that agroforestry practices have the potential to make a significant contribution to both crop production and environment protection.

Vertical distribution of plant nematodes in an aquic brown soil under different land uses

The vertical distribution of the dominant genera of plant nematodes at the depth of 0–150 cm of an aquic brown soil were studied for four land use patterns, i.e., paddy field, maize field, fallow field and woodland in the Shenyang Experimental Station of Ecology, Chi- nese Academy of Sciences in November of 2003. The results showed that the numbers of some dominant genera under different land uses decreased with the increase of soil depth. Helicotylenchus was most dominant genus under each land use type. Genera of Filenchus, Psilen- chus and Tylenchus in paddy field occurred at the depth of 0–20 cm; while Paratylenchus in fallow field and woodland, as well as Praty- lenchus in maize field presented in the deeper soil layers (0–80 cm). Significant correlations between the numbers of dominant genera of plant nematodes and soil chemical properties were found in this study. The number of Helicotylenchus under different land uses was posi- tively correlated with C/N ratio, total C, total N, total P, alkai-N, and Olsen-P. The numbers of Filenchus and Paratylenchus in paddy field, Pratylenchus in maize field and Paratylenchus in fallow field were negatively correlated with soil pH, and positively correlated with total C, total N and alkai-N. This study results showed that it is essential to sample at a certain depth according to the vertical distribution informa- tion of different genera of plant nematodes in adequately assessing the population size of plant nematodes.

Profile Distribution and Storage of Soil Organic Carbon in an Aquic BrownSoil as Affected by Land Use

Many attempts have been made to estimate the soil organic carbon (SOC) storage under different land uses, especiallyfrom the conversion of forest land or grassland into cultivated field, but limited reports were found on the estimation ofthis storage after cultivated field converted into woodland or grassland, especially in small scales. This study is aimed toinvestigate the dynamics of SOC concentration, its storage and carbon /nitrogen (C/N) ratio in an aquic brown soil at theShenyang Experimental Station of Ecology, Chinese Academy of Sciences under four land use patterns over 14 years. Thefour land use patterns were paddy field (PF), maize field (MF), fallow field (FF) and woodland (WL). In each pedon at 0-150cm depth, soil samples were collected from ten layers. The results showed that the profile distribution of SOC was differentunder different land uses, indicating the effect of land use on SOC. Soil organic carbon was significantly related with soiltotal N, and the correlation was slightly closer in nature ecosystems (with R2=0.990 and P<0.001 in both WL and FF, n=30)than in agroecosystems (with R2=0.976 and P<0.001 in PF, and R2=0.980 and P<0.001 in MF, n=30). The C/N ratio in theprofiles decreased generally with depth under the four land use patterns, and was comparatively higher in WL and lowerin PF. The C/N ratio of the FF was closer to that in the same soil depths of MF than to that of PF. Within 100 cm depth, theannual sequestration of SOC was 4.25, 2.87, and 4.48 t ha-1 more in WL than in PF, MF and FF, the annual SOC increasingrate being 6.15, 3.26, and 5.09 % higher, respectively. As a result, the SOC storage was significantly greater in WL than inany of the other three land use patterns, P=0.001, 0.008, and 0.008 as compared with PF, MF, and FF, respectively, whilethere was no significant difference among the other three land uses. It is suggested that woodland has the potential tomake a significant contribution to C storage and environmental quality.

Effect of climate change on the trends of evaporation of phreatic water from bare soil in Huaibei Plain, China

When the soil condition and depth to water table stay constant, climate condition will then be the only determinant of evaporation intensity of phreatic water from bare soil. Based on a series of long-term quality-controlled data collected at the Wudaogou Hydrological Experiment Station in the Huaibei Plain, Anhui, China, the variation trends of the evaporation rate of phreatic water from bare soil were studied through the Mann-Kendall trend test and the linear regression trend test, followed by the study on the responses of evaporation to climate change. Results indicated that in the Huaibei Plain during 1991-2008, evaporation of phreatic water from bare soil tended to increase at a rate of 5% on monthly scale in March, June and July while in other months the increase was minor. On the seasonal basis, the evaporation saw significant increase in spring and summer. In addition, annual evaporation tended to grow evidently over time. When air temperature rises by 1 °C, the annual evaporation rate increases by 7.24–14.21%, while when the vapor pressure deficit rises by 10%, it changes from-0.09 to 5.40%. The study also provides references for further understanding of the trends and responses of regional evapotranspiration to climate change.

Effects of Long-term Located Fertilization on the Physico-chemical Property of Soil Humus

A systematic study concerning the effects of a long-term stationary fertilization on content and property of soil humus in fluvo-aquic soil sampled from Malan Farm, Xinji City, Hebei, and arid red soil and paddy red soil sampled from the Institute of Red Soil, Jinxian County, Jiangxi was conducted. The results showed that long-term fertilization had effects not only on the content and composition of soil humus, but also on the physico-chemical property of humus. With applying organic manure or combined application of organic manure and chemical fertilizer, E4 and E6 values of humic acid decreased in fluvo-aquic soil and arid red soil, but increased in paddy red soil. In paddy red soil, E4 and E6 values of humic acid increased also with a single application of chemical fertilizer, but E4 and E6 values had less change of humic acid in fluvo-aquic soil and arid red soil. The effects on the visible spectroscopic property of f ulvic acid were different from that of humic acid. Long-term application of organic manure or combined application of organic manure and chemical fertilizer could increase E4 and E6 values of f ulvic acid in three types of soil. Single application of chemical fertilizer had less effect on the E4 and E6. Long-term fertilization could also influence the ultraviolet spectroscopic property of humus. With a single application of organic manure or combined application of organic manure and chemical fertilizer, the ultraviolet absorbance of humic acid and f ulvic acid increased in the three types of soil. But this effect was obvious only in short wave length, and the effect could decrease if the wave length increased. With a single application of chemical fertilizer the ultraviolet absorbance of fulvic acid could increase, but it of humic acid increased only in fluvo-aquic soil. Long-term application of organic manure or combined application of organic manure and chemical fertilizer could increase the content of total acidic groups, carboxy groups and phenolic hydroxy groups of humic acid and fuvic acid in the three types of soil. Single application of chemical fertilizer had less effect on the content of total acidic groups, carboxy groups and phenolic hydroxy groups of humic acid and fuvic acid in the three types of soil.

潮土磷库组成及累积磷的消耗转化特征

【目的】长期施用磷肥致使潮土中累积了大量的磷,为精确管控和合理利用累积磷素,我们研究了小麦–玉米连续种植下,停止使用磷肥后磷库的组成和消耗转化特征。【方法】本研究依托位于河南新乡的“国家潮土肥力与肥料效益长期定位试验基地”进行,连续26年施用不同量磷肥,处理间土壤磷积累量差异很大。利用单个处理或两个处理耕层土壤混合的方法,制备Olsen-P含量分别为6.7、14.3、27.6、55.4、72.3 mg/kg的土壤(分别记为L1、L2、L3、L4、L5),用于进行微区耗竭试验,种植制度为冬小麦–夏玉米轮作。在耗竭试验的5年间,测定了土壤全磷、Olsen-P和各磷库组分含量。【结果】潮土磷库中无机磷占比超过90%,L5处理土壤中的有效磷库组分Resin-P、NaHCO_(3)-Pt、NaOH-Pt含量分别为L1的5.0、3.5、2.8倍。L1处理(缺磷土壤)的有效磷组分在全磷中的比例仅为10.4%,而难利用磷组分(C.HCl-Pt, Residual-P)的比例高达24.0%;L5处理(高磷土壤)有效磷组分比例高达20.6%,难利用组分比例低至14.3%。缓效磷组分(D.HCl-Pi)在全磷中的比例基本维持在66%。有效磷水平高于农学阈值(L2处理)之后,Resin-P组分才开始增加,增加量占有效磷库增加量的17.3%~22.6%。磷库耗竭过程中,有效磷库是作物吸收的第一磷库,且以Resin-P、NaHCO_(3)-Pi、NaOH-Pi的先后顺序被利用。Resin-P、NaHCO_(3)-Pi、NaOH-Pi每消耗1 mg/kg,Olsen-P分别减少1.3、0.7和1.0 mg/kg。有效磷库组分与缓效磷库、难利用磷库组分可以互相转化。5年耗竭过程中,L1处理有18.0 mg/kg难利用磷转化为D.HCl-Pi,L2、L3处理分别有22.3和7.2 mg/kg D.HCl-Pi转化为有效态磷,提升了土壤累积磷素的生物有效性;而L4、L5处理分别有29.9和43.1 mg/kg有效态磷组分转化为D.HCl-Pi,降低了土壤累积磷的生物有效性。【结论】随着土壤Olsen-P水平的提高,有效磷库组分Resin-P、NaHCO_(3)-Pt、NaOH-Pt占比增加,难利用磷库占比减少,而缓效磷库占比高且稳定。有效态Resin-P在Olsen-P超过农学阈值后才开始累积。作物吸收可促进缺磷土壤难利用磷库组分转化为缓效磷库组分,中磷土壤缓效磷库组分转化为有效磷库组分,最终土壤累积磷素均被活化利用;而高磷土壤中30%以上的有效磷库组分被转化为缓效磷库组分,作物奢侈吸磷量显著增加,造成一定的磷肥养分浪费。中磷土壤是维持磷资源高效利用和作物高产的最佳磷库组成状态。

聚磷酸铵磷肥对玉米苗期磷素吸收利用和潮土无机磷组分含量的影响

聚磷酸铵磷肥具有缓释性,在石灰性土壤中能够长效供磷,但是释放缓慢易导致作物苗期供磷不足进而影响最终产量,探讨玉米苗期聚磷酸铵磷肥合理施用量及其对潮土无机磷组分含量的影响,为合理施用聚磷酸铵磷肥提供科学依据。采用盆栽试验,设置6个聚磷酸铵磷肥水平,P_(2)O_(5)0、30、60、90、120和150 mg/kg(分别用P0、P30、P60、P90、P120、P150表示),测定玉米的生物学指标和玉米磷素吸收利用状况,同时测定土壤有效磷和无机磷组分含量。结果表明,相较于P0水平,聚磷酸铵磷肥能显著提高玉米的株高、茎粗、地上部和根系干重,株高、茎粗和地上部干重均表现出0~90 mg/kg增幅大、90~150 mg/kg增幅小的趋势,P150水平的株高、茎粗、茎和叶生物量比P0水平分别提高了71.0%、68.8%、334.5%和201.6%。P90水平的玉米茎、根磷含量和磷肥利用效率均为最低值,但磷肥利用效率与P120和P150水平无显著性差异;非根际土壤有效磷含量随施磷量的增加呈极显著的线性关系,每1 mg/kg聚磷酸铵施用量相当于增加了0.0894 mg/kg的非根际土壤有效磷,施磷70 d后根际和非根际土壤有效磷含量依然在13.23 mg/kg以上;土壤无机磷总量随聚磷酸铵磷肥施用量的增加呈上升趋势,相较于P0水平,Ca_(2)-P、Al-P含量出现了显著性变化,O-P含量与比例各施磷水平间无显著性差异,P150水平Ca_(10)-P含量显著高于P90及其以下各处理,相较于P0水平,其Ca_(10)-P累积量增加了101.70 mg/kg。基于本研究结果,聚磷酸铵磷肥可以在根际和非根际石灰性潮土上维持较高的土壤有效磷含量,P_(2)O_(5)60 mg/kg水平以下玉米生物量累积不足,P_(2)O_(5)120 mg/kg水平以上增加了土壤Ca_(10)-P的含量与比例,P_(2)O_(5)90 mg/kg是潮土上玉米苗期较为适宜的聚磷酸铵磷肥用量。

中轻度重金属污染农田土壤的时空特征及改良

为研究农田土壤重金属与速效养分的时空特征以及氮磷增效剂对农田土壤重金属的影响,本试验以受中、轻度污染的酸性棕壤和典型潮土为研究对象,采用田间试验、盆栽试验与室内分析相结合的方法进行研究。结果表明:农田土壤中Cd、Cu、Pb、Zn 4种重金属元素含量在0~20 cm土层显著高于深层土壤;棕壤0~20 cm土层Cd含量超标204%,潮土0~20 cm土层Cd、Zn含量分别超标104%、419%;农田土壤0~20 cm土层重金属有效态含量占比高于深层土壤,棕壤中重金属有效态含量占比高于潮土。棕壤0~20 cm土层全氮、碱解氮、铵态氮、硝态氮、有效磷和速效钾含量均显著高于深层土壤,且随土壤深度增加呈逐渐减小趋势,而潮土中仅全氮、碱解氮和有效磷含量显著高于深层土壤;农田土壤速效养分随时间波动变化,其中硝态氮和铵态氮波动幅度最大,最大变异系数分别为44.1%和47.3%。受污染农田土壤的小麦植株体内Cd、Pb、Cu主要积累在叶片,Zn主要积累在籽粒;不同重金属元素从小麦茎、叶向籽粒的迁移程度差异较大,其中Cd迁移率最小,Zn迁移率最大。氮磷增效剂能显著减少棕壤中重金属有效态含量,底肥+氢醌+双氰胺+生物炭处理的有效态Cd、Cu、Pb、Zn含量较对照(仅加底肥,不加氮磷增效剂)处理分别显著降低24.7%、19.5%、23.7%、18.1%,而在潮土中施用效果不明显。研究表明,农田土壤重金属与土壤养分之间存在一定的相关性,且在土壤垂直分布上大体一致,土壤类型是氮磷增效剂对重金属有效态产生不同影响的重要因素。

长期不同秸秆还田措施对土壤供磷能力的影响

研究潮土区冬小麦-夏玉米轮作体系下长期不同秸秆还田措施对土壤磷素吸附解吸特性的影响,以期为提高该地区土壤供磷能力提供理论依据。依托山东禹城长期定位试验(始于2007年),研究了秸秆不还田(CK)、小麦秸秆单季还田(W)、玉米秸秆单季还田(M)和小麦玉米秸秆双季还田(D)4个处理对土壤有效磷含量和土壤磷吸附解吸特性的影响。结果发现,与CK相比,3种秸秆还田均显著提高了土壤有效磷含量,W、M和D处理有效磷含量分别增加了47.5%、15.4%和12.2%,而土壤交换性钙含量分别降低了49.1%、30.5%和31.7%。不同秸秆还田措施均对潮土磷吸附特征产生了影响:与CK相比,秸秆还田处理均能显著降低土壤对磷的吸附,W、M和D处理土壤磷平均吸附量分别下降了10.7%、7.5%和5.1%;单季秸秆还田处理W的土壤最大吸磷量(Q_(m))显著低于CK处理,但M和D处理土壤Q_(m)与CK没有显著差异;秸秆还田处理的磷吸附饱和度(DPS)均有所增加,但仅单季秸秆还田处理(W和M处理)的磷吸附饱和度显著高于CK。3种秸秆还田处理均显著提高了土壤磷解吸能力,各处理土壤磷解吸率表现为W>D≈M>CK,而秸秆还田处理均显著降低了土壤磷解吸滞后系数(HI),规律表现为CK>D≈M>W。相关性分析结果显示,土壤交换性钙含量与土壤磷吸附解吸能力显著相关。以上结果说明,在石灰性潮土中,单季和双季秸秆还田均能减少土壤对磷的吸附及增加其对磷的解吸能力,从而提升土壤供磷能力,且小麦单季秸秆还田效果优于其他两个秸秆还田处理。降低土壤中交换性钙对磷的固定可能是秸秆还田提高土壤磷有效性的重要途径。

长期秸秆深翻还田及养分管理对潮土有机碳矿化影响

为了明确耕作方式与养分管理对华北潮土土壤有机碳矿化的影响。基于连续15 a(2007—2022年)耕作与养分管理模式长期定位试验开展研究,长期定位试验分为农民习惯耕作管理模式(秸秆不还田+浅旋耕RP-S,rotate plow without straw return)和高产耕作管理模式(秸秆还田+深翻耕DP+S,deep plow with straw return)2个主处理,以及对照施肥(CK)、农民习惯施肥(CON)和优化施肥(OPT)3个副处理,共计6个处理。于2022年10月,采集表层(0~20 cm)土壤样品,分析土壤有机碳及活性碳组分含量与土壤碳库管理指数,并采用室内培养法,测定土壤有机碳矿化速率,利用一级动力学方程拟合土壤有机碳潜在可矿化量和碳半周期,应用结构方程模型揭示长期不同耕作模式与养分管理措施下,土壤有机碳的周转规律。多年试验数据得出,在RP-S条件下,C/N(SOC and TN ratio)总体呈逐渐下降趋势,在DP+S条件下,C/N总体呈先降后增趋势。秸秆还田+深翻耕处理显著提高了土壤活性有机碳组分含量(P<0.05),且碳库管理指数(CPMI,carbon pool management index)提升显著(P<0.05)。与农民习惯施肥相比,优化施肥可以显著提高土壤有机碳含量12.35%。在DP+S条件下,优化施肥显著提高了土壤易氧化有机碳(ROC,readily oxiedozable carbon)与CPMI。各处理土壤有机碳矿化速率均在1 d达到最大,而后1~10 d迅速下降,10 d后缓慢下降直至稳定,有机碳矿化速率随时间呈对数函数型变化,不同处理土壤有机碳矿化速率均符合一级动力学模型。秸秆还田+深翻耕显著提高了累积矿化率(潜在可矿化量与土壤有机碳的比值)23.59%,而优化施肥可以显著降低累积矿化率22.12%。土壤有机碳矿化累积量(C_(t))与土壤有机碳(SOC,soil organic carbon)、土壤活性碳组分和土壤碳库管理指数均呈极显著正相关关系(P<0.01),与土壤潜在可矿化有机碳量(C_(0))呈显著正相关关系(P<0.05),结构方程模型表明,耕作管理、微生物碳(MBC,microbial biomass carbon)和ROC是影响土壤有机碳周转能力和固碳能力的直接因素,耕作与施肥管理可通过对土壤有机碳及活性碳组分的影响,间接影响土壤有机碳周转能力,进而影响土壤固碳能力。长期秸秆深翻耕还田结合优化施肥有利于提高土壤固碳能力,促进农田资源的增碳及可持续利用。

轮耕促进豫北潮土区小麦根系生长和产量增加

【目的】基于耕作定位试验,探索适宜豫北潮土地区的耕作模式。【方法】试验基于始于2016年的耕作定位试验,试验3年一个轮耕周期,选择5个典型处理:(1)连续旋耕(RT-RT-RT);(2)深耕-旋耕-旋耕(DT-RT-RT);(3)深耕-旋耕-浅旋耕(DT-RT-SRT);(4)深耕-条旋耕-浅旋耕(DT-SRT-SRT);(5)深耕-浅旋耕-旋耕(DT-SRT-RT),于2021年测定并分析不同轮耕模式下小麦各生育时期根系性状、光合特性、小麦养分含量、产量,以及土壤孔隙性、土壤团聚体分布。【结果】相较于RT-RT-RT,其他轮耕模式均促进了小麦根系生长,其中以DT-SRT-RT处理的效果最为显著。在拔节期各根系性状增幅最高,其中总根长(RL)提高了80.8%,根表面积(SA)提高了54.1%,根体积(RV)增大了51.5%,根直径(RD)增大了21.9%。随着生育时期推进,各根系性状增幅逐渐下降,其中RL增幅为39.0%—28.8%,SA为21.7%—10.8%,RV为12.4%—17.8%,RD为17.5%—24.5%。与RT-RT-RT处理相比,轮耕处理的小麦光合特性均有所改善,净光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)以DT-SRT-RT处理较为明显,在拔节期涨幅分别为25.7%、41.5%和20.5%;在开花期分别提高了55.4%、21.7%和17.4%,但在灌浆期只有Pn和Gs分别提高了9.7%和13.6%,而Tr则降低了6.7%。与RT-RT-RT处理相比,不同轮耕处理不同程度上提高小麦各器官内全量养分含量,其中DT-SRT-RT处理叶、茎和根中氮含量分别提高了66.2%,80.1%和61.1%;叶和茎中的磷含量提高了31.2%和38.4%;根系钾含量提高达50.0%。相较于RT-RT-RT,DT-SRT-RT处理显著提高了20—30 cm土层土壤孔隙度,最高提高了27.1%;轮耕处理显著降低了0—30 cm土壤容重。轮耕处理有助于提高>0.25 mm土壤大团聚体的占比,其中DT-SRT-SRT处理显著提高了0—20 cm土层>0.25 mm大团聚体的占比;但轮耕处理降低了<0.053 mm黏粉粒的占比。此外,不同轮耕模式的小麦根冠比、穗数、穗粒数、千粒重和产量均高于RT-RT-RT处理,其中DT-SRT-RT处理根冠比增加了55.6%,穗数提高了45.3%,产量提高了20.7%。由相关性分析可得知,根长、净光合速率、气孔导度和产量均呈正相关关系。【结论】在豫北潮土小麦玉米轮作区,轮耕模式改善了土壤孔隙性及小麦根系构型,提高了小麦光合速率、植株全量养分含量和产量,其中以深耕-浅旋耕-旋耕效果最佳。

干旱扰动下长期不同施肥潮土微生物群落稳定性研究

土壤微生物群落稳定性是土壤健康的重要组成部分和评价指标,揭示长期不同施肥的农田土壤微生物群落稳定性有助于指导田间施肥管理,保障农田生态系统的土壤健康和可持续发展。依托中国科学院封丘农业生态实验站长期定位试验,通过对三种不同施肥处理的潮土进行干旱扰动和复水回复的培养试验,从多种微生物群落响应指标(脱氢酶活性、细菌群落alpha多样性、关键物种丰度、微生物群落结构和分子生态网络拓扑属性)分别量化和比较了不同施肥处理的微生物群落稳定性(抵抗力和回复力)。结果表明,与不施肥处理(CK)和平衡施用化肥处理(NPK)相比,有机无机肥配施处理(OM)能够显著增加微生物群落稳定性,表现在OM的微生物群落响应指标在干旱-复水过程中的变化最小,抵抗力与回复力均优于CK和NPK。复水后不同施肥处理的细菌群落alpha多样性、关键物种丰度和网络拓扑参数能够回复到初始水平,而群落结构和脱氢酶活性不能完全回复,说明细菌群落alpha多样性的回复快于群落结构和功能。表明有机无机肥配施能显著提高微生物群落稳定性,是保障农田生态系统土壤健康和可持续发展的优良管理措施。

商品有机肥对砂质潮土理化性状、冬小麦产量及养分积累的影响

为探明适宜砂质潮土地力提升和作物增产的商品有机肥,于2021—2022年在河南省新乡县开展冬小麦田间试验,以单施化肥为对照,研究不同商品有机肥(含炭有机无机复混肥、含菌复合肥、含菌有机肥、含炭有机肥、腐植酸有机肥)对砂质潮土理化性状、冬小麦产量及养分吸收利用的影响。结果表明,商品有机肥施用可实现冬小麦显著增产24.6%~49.7%,其中施用含炭有机无机复混肥和含炭有机肥分别增产49.7%、43.8%。施用含炭有机无机复混肥地上部氮、磷、钾积累量分别显著提高44.6%、43.1%、54.4%,施用含炭有机肥分别显著提高24.8%、33.5%、45.5%。施用商品有机肥可降低0~10 cm土壤容重,同时含炭有机无机复混肥、含菌复合肥、含炭有机肥、腐植酸有机肥分别显著提高砂质潮土有机碳和速效钾含量33.1%~44.8%、10.8%~16.7%。此外,含炭有机无机复混肥和含炭有机肥施用还能提高>0.25 mm土壤团聚体占比,显著提高土壤α-葡糖苷酶、β-纤维二糖苷酶、β-木糖苷酶、亮氨酸氨基肽酶、磷酸酯酶活性。以上表明,含炭有机无机复混肥和含炭有机肥通过降低0~10 cm土壤容重,促进土壤大团聚体形成,提高有机碳、速效钾含量及土壤胞外酶活性,实现冬小麦产量及养分积累量的提高,是适用于砂质潮土的商品有机肥。

沼液替代氮肥对轻度盐化潮土土壤性质和玉米产量的影响

为研究沼液替代氮肥对轻度盐化潮土的土壤性质和作物产量的影响,在山东省滨州市阳信县轻度盐化潮土上开展了玉米田间试验,试验共设置4个处理,分别为常规施肥(XG)及沼液替代常规施肥氮肥的50%(T50)、70%(T70)和100%(T100)。结果表明,与常规施肥比较,沼液替代氮肥处理土壤碱解氮、速效钾和有机质含量显著提高,分别增加了32.30%~34.29%、27.37%~72.25%和14.96%~21.09%,其中T100处理更有利于提升土壤有机质含量,T50处理对土壤有效磷和速效钾的提高效果最好;T50和T70处理显著增加了土壤铁、铜、锌等微量元素含量;T50处理并不能显著增加土壤汞、镉、铬、铅等重金属含量和土壤电导率;沼液替代氮肥显著提高土壤碱性磷酸酶和蔗糖酶活性,分别提高7.18%~32.59%和17.38%~19.85%;沼液替代氮肥处理显著提高微生物丰富度;相较于XG处理,T50、T70和T100处理显著提升了玉米的产量,分别提高了19.01%、16.84%和18.69%。综合分析,沼液替代不同比例氮肥能够显著改善土壤性质和提高玉米产量,在常规施肥的基础上施用50%沼液替代氮肥效果最好。研究结果可为沼液在轻度盐化潮土上的应用提供理论参考。

长期定位施用化肥对非石灰性潮土有机碳及腐殖质组分的影响

土壤有机碳和腐殖质组分受土壤自身质量、施肥管理措施等因素的影响,为明确长期化肥施用对不同土层土壤有机碳(SOC)和土壤腐殖质组分含量的调控效果,在山东莱阳43 a(2021年)长期定位施肥试验,选择低量氮肥(N1)、高量氮肥(N2)、高量氮肥配施磷肥(NP)、高量氮肥配施钾肥(NK)、高氮配施磷钾肥(NPK)和不施肥对照(CK)6个处理。结果表明,与CK相比,N1能够显著提高0~5 cm的SOC含量,其增幅为22.84%,单施氮肥处理能够显著提高5~10 cm的SOC含量,N1、N2的增幅分别为20.94%,28.60%,N1能够显著提高10~20 cm的SOC含量,增幅为17.05%,而其他处理无显著变化。化肥施用能够改变土壤腐殖质组分含量,与CK相比,N1可以显著提高10~20 cm和20~30 cm土层胡敏酸(HA)的含量,增幅分别为22.86%,40.49%,而0~10 cm土层无显著变化;NP可以显著提高0~5 cm,5~10 cm土层富里酸(FA)含量,增幅分别为89.44%和124.63%,NK可以显著提高10~20 cm土层FA的含量,增幅为100.22%,NPK可以显著提高20~30 cm土层FA的含量,增幅为107.48%;N1可以显著提高0~5 cm土层胡敏素(Hu)的含量,增幅为69.34%,N2可以显著提高5~10 cm土层Hu的含量,增幅为66.18%,N1可以显著提高10~20 cm土层Hu的含量,增幅为79.50%,而20~30 cm土层无显著变化。综上表明,在本试验条件下,长期施用化肥可以有效提高非石灰性潮土的土壤有机碳的固定、改变土壤腐殖质组分,且不同的施肥策略影响存在较大差异,其中单施氮肥处理的固碳量效果较好。

沼渣沼液混施对潮土团聚体结合有机碳的影响

为实现畜禽粪污资源化利用和土壤肥力提升提供数据支撑,沼渣沼液混施对黄淮海平原潮土团聚体结合有机碳的影响成为重要研究课题.根据等碳量原则,设置不同沼渣沼液混施比例(100%沼渣,90%沼渣+10%沼液,80%沼渣+20%沼液,70%沼渣+30%沼液和60%沼渣+40%沼液)及对照不施肥处理进行6个月的盆栽试验,测定土壤团聚体组成及结合有机碳变化.结果表明:不同沼渣沼液混施比例对水稳性团聚体粒径组成和结合有机碳含量产生显著影响.相较于对照,各混施处理大团聚体质量组成比例(WR0.25)均有不同程度的提高,其中90%沼渣与10%沼液混施处理占比最大,为57.40%.此外,团聚体结合总有机碳含量随沼渣配施比例的增加呈现先增加后降低的趋势,其中80%沼渣与20%沼液混施处理下达到最高值,为16.5 g/kg.各配施处理均提高>0.25 mm粒径大团聚体结合有机碳的贡献率.因此,可通过80%~90%沼渣与10%~20%沼液混施促进潮土水稳性大团聚体的形成,提高团聚体稳定性和结合有机碳含量,从而达到改善土壤结构,促进土壤有机碳固持的目的.