Improvement in nitrogen availability, nitrogen uptake and growth of aerobic rice following soil acidification

A yield decline and increase in soil pH under continuous cropping of aerobic rice have been reported in previous studies. However, the underlying mechanisms governing the poor growth and low yield of aerobic rice following an increase in soil pH are unknown. The objective of the present study was to determine the effect of soil acidification on the soil nutrient availability, plant nutrition and growth of aerobic rice grown in continuously cropped aerobic soil. Two pot experiments were conducted using soil from a field where aerobic rice had been grown for 13 consecutive seasons. Soil was acidified by adding 50–300 mL of 0.05 mol L^–1 sulfuric acid to 3.0 kg of air-dried soil to achieve a range of soil pH levels. Rice was grown aerobically with N rates of 0–1.2 g per pot using urea or ammonium sulfate. Soil chemical properties were measured as were leaf nutrient concentrations, plant growth parameters, and the above-ground N uptake. A 5.5-fold and 1.5-fold increase in soil ammonium and nitrate were observed, respectively, after adding sulfuric acid. Plant growth and N uptake improved significantly with soil acidification, regardless of N rates or N sources, and were associated with an improvement in plant N nutrition. The application of N had greater positive effects on plant growth and N uptake than soil acidification. The growth response to soil acidification reduced as the rate of N application increased. These results suggest that the yield decline of continuous aerobic rice is probably associated with a reduction in soil N availability and plant N uptake as a result of a gradual increase in soil pH.     

土壤增氧方式对其氮素转化和水稻氮素利用及产量的影响

以3种不同生态型水稻品种中浙优1号(水稻)、IR45765-3B(深水稻)和中旱221(旱稻)为材料,比较研究了不同增氧方式(T1-增施过氧化钙、T2-微纳气泡水增氧灌溉、T3-表土湿润灌溉和CK-淹水对照)下稻田土壤氮素转化和水稻氮素吸收利用特性。结果表明:1)增氧处理明显改善土壤氧化还原状况,3种增氧方式下土壤氧化还原电位均高于CK。稻田增氧促进土壤氮素硝化,在分蘖期和齐穗期T1、T2和T3的土壤硝化强度和脲酶活性均显著高于CK,反硝化强度显著低于CK。2)不同增氧处理对水稻氮素吸收的影响不同,在拔节期、齐穗期和完熟期3品种的植株氮素积累量均表现为T1、T2显著高于CK,而T3显著低于CK;在完熟期,T1处理下中浙优1号、IR45765-3B和中旱221植株氮素积累量分别较CK增加了21.2%、13.2%和17.0%,而T2处理下3品种的植株氮素积累量分别较CK增加了14.3%、6.9%和9.1%。3)与CK相比,T1和T2显著提高水稻籽粒产量和收获指数,氮素籽粒生产效率与CK无显著差异,而T3显著增加水稻氮素干物质生产效率和氮素籽粒生产效率。可见,施用过氧化钙和微纳气泡水增氧灌溉能有效改善稻田土壤氧化还原状况,不仅显著提高水稻产量,而且显著增强稻田氮的硝化而减少氮素损失,从而提高水稻氮素积累量和氮素收获指数。     

Land-use effects on soil carbon and nitrogen in a typical plateau lakeshore wetland of China

Wetland soils (WS) can store a significant amount of soil organic carbon (SOC) and total nitrogen (TN). Surface soils (0–20 cm) were sampled in WS, 20-yr-old conventionally tilled soils (CTS20), 2-yr-old abandoned tilled soils (ATS2), and 6-yr-old abandoned tilled soils (ATS6) to estimate changes in SOC and TN contents due to cultivation and abandonment. Our results showed that SOC and TN contents were significantly higher in WS than those in CTS20, ATS2, and ATS6. As a result of 20-yr cultivation, SOC and TN contents decreased from 43.75 to 24.06 g kg^?1 and from 4.96 to 2.32 g kg^?1, respectively. However, after the abandonment of cultivated wetlands, SOC and TN contents showed a slow increase but the change was not significant among CTS20 and ATS2. The findings of this study suggest that SOC and TN contents in top 20 cm soils of wetlands can be reduced significantly by cultivation, but they are restored slowly after abandonment.     

稻田沟渠-湿地系统的碳氮稳定同位素组成特征

由于稳定同位素在特定污染源中具有特定的组成,在污染物质迁移转化过程中作为示踪剂而广泛应用。针对目前农业面源污染较为严重的现状,该文利用碳氮稳定同位素研究了灌区内外源物输入对稻田沟渠-湿地系统的贡献。结果表明,水中颗粒性有机物(particulate organic matter,POM)由于受到光照、营养物质不同导致POM在各采样点组成不同,δ13C变化范围较大,均值为-27.8‰,与大型水生植物和浮游植物接近,此类植物可能是POM的主要来源。水中δ13CDIC(dissolved inorganic carbon,DIC)与浮游植物呈线性相关,浮游动物δ13C与浮游植物存在一定相关性,而浮游植物与POM之间不存在显著性差异,说明研究区内浮游动物对內源有机碳的利用主要是取食浮游植物低持斜聿愠粱?δ13C值变化范围在-27.2‰～-21.8‰之间,明显高于水体POM含量,说明表层沉积物存在比颗粒有机物更富集碳的藻类与陆源碎屑等物质。各采样点颗粒有机物δ15N值的范围3.1‰～4.2‰,平均值为3.6‰,其中湿地δ15N高于其他采样点。沉积物δ15N平均值为-0.6‰,与大气中N2较为接近。     

水氮管理对黑土稻作土壤碳氮磷化学计量特征的影响

为阐明不同水氮管理模式对黑土稻作产量和土壤碳氮磷化学计量特征的影响。设置3种灌溉模式（常规淹灌、浅湿灌溉、控制灌溉）和4种氮肥梯度（0、85、110、135 kg/hm2）,探究水稻产量、土壤碳氮磷含量、化学计量比及层化率对不同水氮管理模式的响应规律。结果表明：控制灌溉模式下,水稻通过形成足量大穗提高库容,小幅增加结实率,从而显著提高产量（p<0.05）。稻田土壤有机碳（SOC）、土壤总氮（STN）、土壤总磷 (STP) 含量随土层深度增加而降低,施氮处理可显著提升SOC、STN含量并降低STP含量（p<0.05）。常规淹灌模式增加SOC、STN含量,控制灌溉模式增加STP含量。土壤C/N随施氮量增加而降低,土壤C/P、N/P随施氮量增加而升高,施氮能提升不同土层平均C/N层化率,降低C/P、N/P层化率。相比常规淹灌,控制灌溉模式能提升不同土层SOC、STP含量层化率,在一定程度上说明控制灌溉配施适宜氮肥可以改善土壤质量,综合考虑CN2为最优水氮管理方式。     

施用预处理稻秆的土壤供氮特征及对冬小麦氮吸收的影响

采用盆栽试验方法,研究了经过预处理的水稻秸秆(预处理稻秆)施入土壤后对土壤的供氮特征及小麦氮营养的影响。研究结果表明,稻秆经过预处理后,纤维素、半纤维素以及二氧化硅比原始稻秆都有所降低,而可溶性物质增加;施用时配施无机氮肥,小麦全生育期内土壤微生物量N和矿质态N平均分别比对照(纯土壤)提高232.3%和66.0%,小麦干物重和吸收总氮量分别比对照高56.3%和124.3%,并优于未经处理的原始秸秆及单施尿素处理。可见处理秸秆配施尿素能够显著改善土壤的供氮状况,促进小麦对氮素的吸收,增加小麦产量,提高化学肥料氮的利用率。     

Effects of organic matter addition on phosphorus availability to flooded and nonflooded rice in a P‐deficient tropical soil: a greenhouse study

Addition of organic matter (OM) to flooded soils stimulates reductive dissolution of Fe(III) minerals, thereby mobilizing associated phosphate (P). Hence, OM management has the potential to overcome P deficiency. This study assessed if OM applications increases soil or mineral fertilizer P availability to rice under anaerobic (flooded) condition and if that effect is different relative to that in aerobic (nonflooded) soils. Rice was grown in P‐deficient soil treated with combinations of addition of mineral P (0, 26 mg P/kg), OM (0, ~9 g OM/kg as rice straw + cattle manure) and water treatments (flooded vs nonflooded) in a factorial pot experiment. The OM was either freshly added just before flooding or incubated moist in soil for 6 months prior to flooding; blanket N and K was added in all treatments. Fresh addition of OM promoted reductive dissolution of Fe(III) minerals in flooded soils, whereas no such effect was found when OM had been incubated for 6 months before flooding. Yield and shoot P uptake largely increased with mineral P addition in all soils, whereas OM addition increased yield and P uptake only in flooded soils following fresh OM addition. The combination of mineral P and OM gave the largest yield and P uptake. Addition of OM just prior to soil flooding increased P uptake but was insufficient to overcome P deficiency in the absence of mineral P. Larger applications of OM are unlikely to be more successful in flooded soils due to side effects, such as Fe toxicity.     

Influences of organic debris and rice root on the nitrogen fixation in the submerged soil

Abstract

A series of experiments has been conducted on the N2 fixation in the paddy soils by the authors (1–4). The amount of organic substrates for microorganisms and the degree of reduction of the soil are found to be two major factors affecting the N₂-fixing activity of the heterotrophic microorganisms in the submerged soil. Organic debris, rice root and their neighboring soils are identified to be the important micro-sites for the heterotrophic N₂ fixers. The organic debris and the rice root are considered to play dual roles by supplying the organic substances; (1) increase of the population of the heterotrophic N₂ fixers—the amount of nitrogenase, (2) preparation of the reduced conditions favorable for the nitrogenase activity.

However, it is not yet clearly known which of these two roles of the organic substrates is more essential to the N₂-fixing activity in the paddy soil. In addition, it is expected that there must be some differences between the organic debris and rice root in their contribution to the N₂ fixation in the paddy soil.

An experiment was carried out to clarify these problems. Moist soil sample was collected from the plough layer of the paddy field at Central Agric. Exp. Sta. in Konosu City, Saitama Pref., passed through a 5 mm sieve and placed in pots (3 kg moist soil/pot). Ammonium sulfate, calcium superphosphate, and potassium chloride at the rate of 0.4-0.4-0.4 (N-P₂O₅-K₂0) g/pot were incorporated into the soil 7 days before transplanting. Split application of ammonium sulfate at the rates of 0.2 and 0.4 g N/pot were also incorporated at 30 and 41 days after transplanting respectively. These pots were divided into three series; planted (P-series), non-planted (N-series), and non-planted and applied with organic manure (O-series). In case of O-series, 60 g of fairly rotted organic manure was applied to each pot. Each pot of P-series was planted with two 4O-day-old seedlings of rice plant at 7 days after submergence. The Nseries was regarded as a control. Each series was not replicated in this preliminary experiment.     

Alleviating soil sickness caused by aerobic monocropping: Responses of aerobic rice to various nitrogen sources

Yield decline resulting from continuous cropping of aerobic rice is a constraint to the widespread adoption of aerobic rice technology. Shifts in water management from flooded to aerobic conditions are known to influence the availability and form of N present in the soil and might require a different approach to N management in aerobic rice. The present study was conducted to determine the effects of different N sources on the plant growth and grain yield of aerobic rice. Four pot experiments were conducted in which rice was aerobically grown in soil that was taken from fields where aerobic rice has been cultivated for 11 consecutive seasons and an adjacent field where flooded rice has been grown continuously. Nitrogen was applied as ammonium sulfate, urea, ammonium chloride, ammonium nitrate and potassium nitrate at four N rates of 0.3, 0.6, 0.9 and 1.2 g N pot⁻¹. Two unfertilized controls consisting of soil that was either untreated or oven heated at 120°C for 12 h were also included. Plants were sampled during the vegetative stage or at maturity to measure plant growth, N uptake, grain yield and the yield components. Growth of aerobic rice in aerobic soil was generally better with the application of ammonium-N than nitrate-N. Potassium nitrate decreased plant growth and caused plant death at the high N rate. Ammonium sulfate was more effective in improving the vegetative plant growth, N nutrition and grain yield of aerobic rice than urea at the high N rates. The application of ammonium sulfate achieved the same and even better plant growth than the soil oven-heating treatment. These results suggest that there is a possibility of reversing the yield decline observed in the continuous aerobic rice system by using the right source of N fertilizer at the optimal rate.     

水生植物堆肥替代部分氮肥提高水稻产量与稻田土壤肥力

为评价太湖流域水生植物堆肥对水稻产量及稻田土壤肥力效应,在太湖流域典型稻田连续进行4a的田间定位试验,比较在等氮条件下不同比例的水生植物有机堆肥替代处理(有机氮替代率分别为0、20％、40％、60％、80％和100％)引起的水稻籽粒产量、产量构成因子、氮磷钾吸收量以及土壤碳氮含量和pH值变化.结果表明:与单施尿素相比,水生植物有机堆肥与尿素配施利于水稻产量的提高,并随着有机肥替代率增加,水稻产量呈先增后降;当有机肥替代率达40％和60％时产量最高.单施有机肥和单施尿素处理水稻籽粒产量相当.单施有机肥显著降低了有效穗数,有机肥和尿素配合施用则可减轻甚至消除这一效应;有机肥替代率在40％和60％时,有效穗数、穗粒数和结实率均较高.随着有机肥施用量增加,水稻秸秆氮浓度降低,籽粒氮浓度无影响;水稻磷浓度和吸收量均无显著差异;有机肥与尿素配施均显著提高了秸秆钾吸收量,有机肥替代率在80％时可显著提高籽粒钾吸收量.表层土壤全氮和有机碳含量及土壤pH值均与有机肥替代率呈显著正相关关系.有机肥-尿素配施处理下土壤全氮和有机碳均较4a前显著提高.有机肥替代率为80％和100％,土壤pH值较试验前土壤分别显著升高.由此可见,水生植物有机肥与尿素配施可以提高太湖稻作区水稻产量,增加土壤有机质含量和减缓土壤酸化程度,可作为太湖稻作区一项环保型施肥技术.     

Charcoal in Amazonian paddy soil—Nutrient availability,rice growth and methane emissions

We investigated the effects of charcoal under flooded (anoxic) rice cultivation at low and high fertilizer levels during 2 y in the Maranhão lowlands, eastern periphery of Amazonia. Two applications (at onset of first and second year) of 15 Mg ha^–1 of fine (< 2 mm) charcoal derived from the endocarp of the babassu (Attalea speciosa Mart.) palm nut had little influence on soil fertility, rice growth, yield, and nutritional status. Exception to this were negative impacts of charcoal on first‐year N availability, with lower sub‐superficial soil NH$ _4^+ $ availability paired with lower rice tissue N and a responsiveness of grain yields to (mainly N‐) fertilization following charcoal application. This N‐limitation effect was, however, limited to the first year and—though statistically significant—without agronomic relevance. The most consistent charcoal effect on flooded‐soil fertility was the strong increase in K availability in the second year, at low and to a lesser extent at intermediate, but not at high fertilizer level. Low K concentrations of our charcoal exclude the possibility of direct K inputs via charcoal, suggesting other indirect mechanisms for K availability increases. Methane fluxes in the second year were significantly reduced (–43.8%) by charcoal application, charcoal‐induced reductions were stronger under high‐ (–47.3%) than under low‐fertilizer regime (–26.0%). Thus, charcoal could be a valuable tool for reducing methane emissions associated with intensely fertilized flooded rice, without significantly affecting grain yields.     

Characteristics of microbial biomass and soil organic matter in newly reclaimed wetland rice soils

Microbial biomass C, N, total organic C, N and mineralizable N were measured in newly reclaimed wetland sandy loam rice soil with a very low nutrient status. Microbial biomass C increased 5.4–10.4 times due to application of barnyard manure, but decreased drastically to 24–27% during rice cultivation. Organic C and N contents also decreased during cultivation, but to a lesser extent to 59–76%. At the tillering stage of the rice plant, microbial biomass N was highly correlated with mineralizable N (r=0.986).     

秸秆还田及氮肥调控对不同肥力白浆土氮素及水稻产量影响

三江平原是黑龙江省水稻主要种植区,白浆土是主要种稻土壤,在白浆土上开展秸秆还田试验研究,明确白浆土秸秆还田效果,根据土壤肥力水平调控氮素为秸秆还田提出因地制宜的土壤、施肥等管理技术提供参考。该文以白浆土为供试土壤,比较研究不同肥力白浆土上连续秸秆还田及调控氮素对水稻产量及土壤养分变化的影响。结果得出:高肥力土壤连续秸秆还田适合减氮,减氮10%连续3年水稻不减产,增产幅度为0.1%～6.94%,减氮20%以上产量降低,秸秆连续还田增加氮素水稻产量第1年与正常施肥比增产4.47%,第2年水稻产量比对照减产4.02%～31.86%,调氮降低幅度大;中、低肥力土壤秸秆还田水稻产量第1年比对照分别增加1.48%,4.52%,第2年调氮增产幅度会下降;秸秆还田使土壤有机质、氮素含量提高,在高肥力土壤上氮素过高使水稻前期分蘖量增多,水稻有效穗数降低,产量降低,减氮后可以避免土壤氮素过剩,水稻产量提高;中、低肥力土壤秸秆还田有利于增加土壤肥力水平,适当增加氮素可使水稻产量提高。     

优化氮肥用量和基追比例提高红壤性水稻土肥力和双季稻氮素的农学效应

【目的】 优化氮肥用量和基追比例是实现氮肥减施和提高肥料利用率的重要途径。本研究在南方典型双季稻种植区进行定位试验,通过对土壤肥力与氮素农学效益进行综合评价,以期提出适合当地土壤和水稻种植条件的氮肥减施模式。 【方法】 以南方典型红壤区双季稻种植体系为研究对象,于 2014～2015 连续进行了 4 季大田定位试验,设处理:1) 不施氮肥 (T1);2) 当地农民习惯施氮 (T2),早稻、晚稻各施 N 165 和 195 kg/hm2,基肥∶蘖肥∶穗肥比分别为 60∶40∶0、40∶30∶30;3) 在 T2 处理基础上减施氮肥 20% (T3),即早稻施 N 135 kg/hm2,晚稻施 N 165 kg/hm2,基肥∶蘖肥∶穗肥比均为 40∶30∶30,并以 20% 有机氮代替普通化肥氮。分析了成熟期水稻产量和植物样氮素含量,测定了 0—20 cm土壤微生物量碳、氮含量,土壤 pH、有机质、全氮、速效钾和有效磷等理化指标,计算了累计氮肥利用率和氮肥农学效率,分别利用内梅罗指数法和灰色关联度法综合评价了土壤肥力效应以及各施肥模式的综合效益。 【结果】 1) 各处理土壤综合肥力指数 (IFI) 值由高到低为 T3 > T2 > T1;与 T2 处理相比,优化氮肥用量和基追比例的 T3 处理 IFI 值提高 2.34%,土壤微生物量碳含量提高了 4.37%～25.39%,土壤微生物量氮含量提高了 17.85%～29.24% (P < 0.05)。2) 与 T2 处理相比,2014–2015 年 T3 处理累计氮肥农学效率显著提高了 29.66% (P < 0.05),累计氮肥表观利用率显著提高了 28.82% (P < 0.05);2014 年各处理水稻总产量无显著差异,2015 年水稻总产量 T3 处理比 T2 处理提高了 5.26%,两年水稻总产量,T3 处理提高了 2.38%。3) 对土壤养分指标、土壤微生物指标和氮素农学效率指标进行关联度分析,2014～2015 年 T3 处理关联度最大,分别为 0.9999 和 1.0000,在土壤肥力和氮肥农学效应综合评价中最优,表明优化氮肥用量和基追比例能够实现氮肥减施以及肥料利用率的提高。 【结论】 在当地农民习惯施氮的基础上减施 20% 化肥氮,以有机氮替代,并适当提高化肥氮在抽穗期的比例,能够保证土壤综合肥力的可持续性、氮素养分持续高效利用和水稻持续稳产。      

两类温带森林下土壤氮的有效性指标比较

To evaluate the validity of different indices in estimating soil readily mineralizable N, soil microbial biomass （Nmic）, soil active N （SAN）, soluble organic N （SON）, net N mineralization rate （NNR） and gross N mineralization rate （GNR） in mineral soils （0-10 cm） from six forest stands located in central Germany were determined and compared with two sampling times： April and November. Additionally, soil density fractionation was conducted for incubated soils （with addition of ^15NH4-N and glucose, 40 days） to observe the sink of added ^15N in different soil fractions. The study showed that Nmic and NNR in most stands differed significantly （P 〈 0.05） between the two sampling times, but not GNR, SAN and SON. In November, no close relationships were found between GNR and other N indices, or between Nrnic, SON, and SAN and forest type. However, in April, GNR was significantly correlated （P 〈 0.05） with Nmic, SAN, and NNR along with Nmlc under beech being significantly higher （P 〈 0.05） than under conifers. Furthermore, density fractionation revealed that the light fraction （LF, 0.063-2 mm, 〉 1.7 gcm^-3） was not correlated with the other N indices. In contrast, results from the incubation study proved that more 15N was incorporated into the heavy fraction （HF 〈 0.063 ram, 〉 1.7 g cm^-3） than into LF, indicaing that more labile N existed in HF than in LF. These findings suggested that attention should be paid to the differences existing in N status between agricultural and forest soils.     

不同地力水平下超级稻高产高效适宜施氮量及其机理的研究

在江苏淮北稻区,稻麦两熟制条件下,选取有代表性的超级稻品种徐稻3号（中熟中粳）为供试材料,系统研究了麦茬田高、中、低3种地力水平上不同施氮量对超级稻产量及氮素吸收利用的影响,并探讨了不同地力水平上超级稻高产高效的机理。结果表明：1）同一施氮水平下,高地力土壤上水稻产量显著高于中地力,中地力显著高于低地力,两年3种地力水平上的最高产量对应的最适施氮量分别为259.9和261.7 kg/hm^2、290.1和290.8kg/hm^2、346.8和344.1 kg/hm^2;2）氮肥表观利用率与施氮量之间存在显著或极显著的二次曲线关系,两年的最高氮肥表观利用率对应的施氮量分别为高地力274.1和263.0 kg/hm^2、中地力295.4和291.3 kg/hm^2、低地力332.6和337.7 kg/hm^2,不同地力水平及施氮量条件下,氮素收获指数、氮素稻谷生产效率及氮素生理利用率差异显著,均随施氮量增加而降低,不同地力水平之间表现为高地力〈中地力〈低地力的趋势;3）不同地力水平上通过调节施氮量可以获得较高总颖花量,产量构成因素能够协调发展,随着生育期进程的推进,不同地力水平上随施氮量增加,水稻群体氮素积累量呈上升趋势,氮素转移率与贡献率降低,而抽穗到成熟阶段的氮素吸收速率表现出先升后降的趋势,以上各项指标均表现出高地力〉中地力〉低地力的水平。通过对不同地力条件下施氮量与产量及氮素吸收利用关系的研究,认为不同地力土壤实现氮肥高产高效目标,高地力土壤应适时控氮肥,以调整产量构成因素协同发展同时提高氮素利用率;中、低地力应加强培肥地力并增施氮肥,增大群体总颖花量及植株的氮素累积量;该地区高、中、低3种地力水平麦茬田上氮肥高产高效对应的合理施氮量分别为264.7（259.9～274.1）kg/hm^2、290.8（290.1～295.4）kg/hm^2、344.1（332.6～346.8）kg/hm^2。     

长期绿肥与氮肥减量配施对水稻产量和土壤养分含量的影响

为探明湘南双季稻区绿肥还田下的氮肥适宜施用量,设计了始于2008年冬季开展的长期田间定位试验(2009-2017),研究绿肥与氮肥减量配施对双季稻的产量、氮肥农学效率、氮肥偏生产力以及2017年稻田耕层土壤养分含量的影响。共设计6个施肥处理:不施氮肥空白对照、仅紫云英、习惯施肥、紫云英与100%无机氮配施、紫云英与80%无机氮配施、紫云英与60%无机氮配施。结果表明:与习惯施氮量相比,绿肥结合习惯施肥以及绿肥与化肥氮减量20%～40%配施均能保持甚至提高2009-2017年稻谷周年产量,显著提高早、晚稻氮肥偏生产力和氮肥农学效率。绿肥与化肥氮减40%时,产量变异系数最低和产量可持续指数最高。试验9 a后,与2008年相比,稻田土壤有机质和全氮含量呈上升趋势。与习惯施肥相比,绿肥与化肥氮减量20%～40%能维持土壤磷素与钾素的供给。综合考虑,紫云英还田下,化肥氮减施40%仍能获得高产稳产,且氮肥利用率最高,产量稳定性最好,并可缓慢提高土壤肥力,是湘南双季稻种植区较好的施肥模式。     

土壤磷素形态及其生物有效性研究进展

土壤磷素形态及其生物有效性的研究对解决农业生产中所引起的经济、环境和资源问题有很重要的作用。结合国内外已有成果和最新研究进展,从土壤的形态、磷的分组以及测定方法,土壤各形态磷的生物有效性等几个方面综述了国内外土壤磷的研究现状,并提出了目前在土壤磷研究中存在的一些问题以及今后研究的热点。     

华北平原春玉米种植体系中土壤无机氮的时空变化与盈亏

在华北平原北部高肥力土壤条件下,研究了不同氮肥管理模式（包括不施氮、推荐施氮和经验施氮）对春玉米物质生产、土壤无机氮时空动态、氮素盈亏和平衡的影响。结果表明：1）推荐施氮和经验施氮未能显著提高春玉米产量,但显著提高了总吸氮量,而氮素收获指数与总吸氮量呈相反趋势。2）春玉米生长季内,土壤铵态氮含量始终处于较低水平,土壤中无机氮形态以硝态氮为主;全生育期内的土壤硝态氮含量,经验施氮均明显高于其它施氮措施,推荐施氮居中,不施氮最低。3）受土壤肥力和天气的影响,春玉米生长期间土壤硝态氮会发生大幅度的垂直运移,潜在淋洗量很大。4）不施氮处理中土壤矿化量占总吸氮量的75％,其中绝大部分矿化集中于春玉米生育后期,土壤Nmin残留量比播前起始值下降了21．4％;经验施氮中施氮量过大造成大量的损失,表观损失率高达42．6％,残留率为48．60k;而推荐施氮处理不仅能够保持产量和土壤供氮能力的稳定,更减少了氮素损失的可能。     

翻压等量紫云英条件下不同化肥用量对土壤养分有效性及水稻产量的影响

在翻压等量紫云英条件下,研究了不同化肥用量对土壤养分有效性及水稻产量的影响.结果表明,早稻田翻压紫云英22500 kg/hm2后配施化肥,与施用100％化肥(MF100)相比,施用60％～80％化肥,土壤中碱解N、速效钾含量均有增加,增幅为10％～59％;施用40％化肥,土壤中有效磷含量显著增加25％ ～ 80％.翻压...