不同惰性有机碳物料对土壤镉赋存形态和生物有效性的影响

通过温室盆栽试验和土壤培养试验,研究镉污染土壤和模拟镉污染土壤中加入草炭、活性碳和风化煤3种物料对土壤镉赋存形态和生物有效性的影响,探讨其作为重金属镉污染土壤修复剂的可行性。研究结果表明：3种有机碳物料均降低了土壤pH值,镉污染土壤加入不同惰性有机碳修复剂后,土壤中醋酸铵提取态Cd含量和DTPA提取态Cd含量变化不明显。在模拟Cd污染土壤上则不同,加入不同惰性有机碳修复剂后土壤中醋酸铵提取态Cd含量和DTPA提取态Cd含量均明显降低,降低幅度以风化煤最高,且随加入时间延长降低幅度增加。土壤中加入风化煤和草炭可显著增加土壤中轻组有机质含量,风化煤对土壤中镉有较强富集作用。两种土壤镉赋存形态均为酸提取态〉可还原态〉可氧化态,镉污染土壤加入有机物料后酸提取态镉含量无显著性变化,可还原态镉草炭和活性碳处理显著降低,草炭处理可氧化态镉也显著降低,模拟镉污染土壤加入有机物料后,酸提取态镉风化煤处理显著性降低,可还原态镉活性碳处理显著提高,可氧化态镉无显著性变化。在镉污染土壤上,3种有机碳物料对玉米生长没有显著影响,但增加了玉米体内镉含量;风化煤处理显著降低了白菜生物量,增加了白菜体内镉含量。模拟镉污染土壤上3种有机碳物料对白菜和玉米的生长和体内镉含量均没有显著影响。     

有机物料对土壤有机磷组分及其矿化进程的影响

通过300天室内恒温(30℃)好气培养实验,研究了不同C/N有机物料(水稻秸秆、玉米秸秆、牛粪、猪粪)掺入土壤后,土壤有机P及各组分含量和有机P的矿化特征。结果表明:有机物料的添加,不同程度地增加了土壤有机P含量;添加有机物料处理,有机P矿化率高于对照处理,且在培养的前30天迅速矿化。掺入有机物料处理土壤有机P各组分含量均有所增加;对照处理有机P各组分的矿化进程都比较平稳,而添加物料处理的活性和中等活性有机P则呈增加或波动状态,中稳和高稳性有机P在腐解初期出现迅速矿化。有机物料的添加,可以促进有机P各组分间的转化,提高土壤P素的有效性。     

不同有机物料对连作大豆土壤养分含量及生物性状的影响

选取畜禽粪便、天然有机物料、有机肥类有机物料3大类共9种有机物料进行大田试验,设正茬和连作2种种植方式,主要研究不同类型有机物料对土壤养分和生物性状变化特征的影响。结果表明:有机物料的施入对提高土壤养分含量和改善土壤生物性状作用效果明显。正茬土壤pH为5.70~6.00,连作土壤pH为5.50~5.90,施用有机物料小区均高于CK处理。畜禽粪便类有机物料,对提高大豆土壤速效钾含量效果显著,对正茬和连作土壤分别平均提高12.73%和17.09%;猪粪对正茬土壤呼吸提高11.30%;鸡粪对连作土壤中微生物量氮提高13.85%。天然有机物料,对提高土壤中碱解氮作用明显,正茬和连作分别平均提高6.31%和3.30%。有机肥类有机物料,对大豆土壤中速效磷含量正茬和连作土壤分别提高2.13%和2.27%,有机质含量分别提高1.98%和4.20%;鸡粪型有机肥对正茬土壤微生物量碳提高3.45%。所有有机物料处理整体效果均好于CK处理,这表明有机物料的施入具有提高大豆土壤养分含量,改善土壤养分性状的作用。     

不同有机物料对苏打碱化土有机碳库和化学性质的影响

以内蒙古河套灌区苏打碱化土为研究对象开展田间试验,设置常规施肥(CK)、生物炭+常规施肥(BC)、牛粪+常规施肥(CD)、玉米秸秆+常规施肥(SW)和羊粪+常规施肥(GM)5个处理,研究不同有机物料添加对碱化土壤有机碳(SOC)库和化学性质的影响。分别于2019年和2020年收获季采集0—30 cm耕层土壤,分析不同有机物料添加下SOC及其活性碳组分和主要盐碱指标的变化特征及其相关关系。结果表明:与CK相比,2019年和2020年各有机物料添加处理下SOC平均增幅分别为22.7%和17.2%,土壤有机碳储量(SOCs)平均增幅分别为22.9%和18.2%;4种有机物料均提高了碱化土壤活性有机碳组分含量,其中,CD和GM处理下各活性碳组分含量增幅较其他处理更高;2019年各有机物料添加处理下碳库管理指数(CPMI)较CK提高53.8%~108.3%,2020年提高71.3%~144.1%(P＜0.05),CD和GM对CPMI的提升作用更明显。土壤化学性质方面,2020年各有机物添加处理下pH均显著下降,BC和CD处理下碱化度(ESP)分别显著下降36.9%和29.3%,CD处理下蔗糖酶活性提高36.7%(P＜0.05)。主成分分析(PCA)表明,影响苏打碱化土SOC含量变化的主要因素为活性有机碳组分和ESP。牛粪和羊粪施用对苏打碱化土有机碳库质量提升作用较好,生物炭施用对盐碱化指标改良效果最明显。     

硫酸铝和有机物料对盐碱土有机碳组成及复合体的影响

通过进行实验室室内培养试验,以盐碱土为研究对象,添加不同梯度有机物料(10,20,30,40,50,60 t/hm²)和同一硫酸铝添加量(0.2 t/hm²),研究硫酸铝和有机物料对盐碱土有机碳组成及复合体的影响。结果表明：施用硫酸铝和有机物料能够显著提高有机碳含量及活性有机碳含量。在施用硫酸铝且有机物料施用量为30 t/hm²时,微生物碳增长趋势开始减缓,土壤微生物商值到达峰值,Kos值与其他处理相比最低;硫酸铝和有机物料的施用可以促进土壤中粒级由小向大聚集,同时使各粒级复合体内有机碳含量增加,在有机物料施用量为30 t/hm²时,可以明显看出土壤结构变化。即在施用硫酸铝且有机物料施用量为30 t/hm²时,既能够有效提高盐碱土土壤肥力,又能改善土壤结构,能够经济合理地改良培肥盐碱地。     

土壤有机磷形态的生物有效性研究

通过对土壤有机磷形态测定及其与土壤有效磷、小麦幼苗吸磷量、黑麦幼苗吸磷量、幼苗试验土壤有机磷矿化量的相关分析,研究了土壤有机磷形态的生物有效性。结果表明:反映土壤供磷状况及植物磷素营养状况的一些相关指标,如有效磷、黑麦草幼苗吸磷量与有机磷组分无明显直线相关关系,不能说明土壤有机磷形态的有效性。而幼苗试验土壤有机磷的矿化量、小麦幼苗吸磷量可以从一个侧面反映土壤有机磷形态的有效性。总的趋势是活性有机磷和中等活性有机磷表现出较高的有效性,高稳性有机磷有效性最低。     

有机物料对土壤的外源铜和镉形态变化的不同影响

采用盆栽和连续提取法研究稻草和紫云英对土壤外源铜和镉形态分布的不同影响。研究结果表明，添加稻草和紫云英可促进潮土中外源铜逐步向生物有效性较低的紫有机质结合态铜和无定形铁结合态铜转化，降低铜的生物有效性，但添加有机物料对潮土中外源镉形态的影响完全不同，添加稻草和紫云英，在分蘖期可减少潮土交换态镉、提高紧有机质结合态和氧化锰结合态镉，但这种作用并不稳定。随着时间的推移，氧化锰和紧有机质吸附的镉将随着活性锰的还原和紧有机质的分解被释放出来，并向交换态镉转化，提高镉的生物有效性。铜和镉离子与土壤的固相不同的结合能力导致稳草和紫去英对潮土中外源铜、镉形态的再分配过程的影响不同。     

有机物料中有机磷矿化进程的研究

采用室内恒温好气培养试验,研究不同C/N有机物料腐解过程中有机磷的矿化特征与进程。结果表明:新鲜粪肥类有机物料中磷以无机磷(P i)为主,秸秆类有机物料中磷以有机磷(Po)为主,有机物料中有机磷在培养的前30天矿化最快,之后趋于平缓,培养结束时,供试有机物料中磷均以无机磷为主,约占全磷的70~90%;不同有机物料有机磷的残留率在腐解前期差别很大,后期趋于一致,有机磷的矿化要先于有机氮;有机物料中磷的矿化速率大小与C/PO及有机磷含量的大小存在显著的相关关系。     

长期外源有机物料添加对川中丘陵区农田土壤养分和有机碳组分的影响

有机肥和秸秆等有机物料添加是调控土壤肥力的重要手段，可促进农田土壤有机碳的数量和质量发生变化。研究选取盐亭紫色土农业生态试验站长期（16a）6种不同施肥处理试验小区，探究两种形式的外源有机物料（猪粪堆肥和秸秆还田）添加对土壤有机碳及总氮、总磷、硝态氮和速效磷养分含量的影响，并基于固态13C核磁共振波谱技术(13C-NMR)分析其对土壤有机碳化学组分的影响。研究发现，添加有机物料可显著增加0~30 cm土壤有机碳和各养分含量；猪粪堆肥施用对土壤总磷、速效磷和硝态氮含量的影响大于秸秆还田。结果还表明两种有机物料添加改变了耕层土壤有机碳化学组成及其稳定性，有机物料添加增加了0~10 cm表层土壤有机碳中烷氧基碳和羧基碳的比例，降低了烷基碳的比例，同时降低了10~20 cm土层羧基碳比例，增加了烷基碳比例。本研究可为区域旱耕地有机碳库稳定性及其碳汇功能评估提供科学依据。     

湖南稻田土壤有机磷组分的施磷效应、季节变化及生物有效性研究

为探明施用磷肥对湖南稻田土壤有机磷组分的影响、有机磷组分的季节变化及其有效性,以湖南省5种不同母质发育的稻田土壤为供试土壤,通过盆栽试验,研究了稻田土壤有机磷组分的施磷效应、在植稻期间的动态变化及其生物有效性。结果表明,施用磷肥可以使土壤中活性有机磷得到较大的增加,而对活性有机磷、中稳性有机磷和高稳性有机磷影响较小。在施磷和不施磷条件下,土壤有机磷的变化主要是中活性有机磷,而其余3种形态有机磷在水稻生长期间几乎保持不变。不管土壤是否施用磷肥,土壤有效磷与有机磷总量总是呈极显著相关,说明土壤有机磷的确是植物可以利用的有效磷源;在早稻生长期间土壤各形态有机磷的生物有效性的大小顺序为:中活性有机磷中稳性有机磷高稳性有机磷活性有机磷;在晚稻生长期间土壤各形态有机磷的生物有效性一般随水稻生育期不同而不同。     

An assessment of various pools of organic phosphorus distributed in soil aggregates as affected by long-term P fertilization regimes

The phosphorus (P) forms in long-term fertilization determine the fate and transport of P in soil. However, the fate of various pools of organic P of added P in the long-term measured with sequential chemical fractionation is not well-understood. Four soil physical aggregates (>250, 125–250, 63–125 and <63 μm) from 0- to 20-cm depth after 35 years of long-term fertilization treatments including control (CK), nitrogen and phosphorus fertilizer (NP) and NP combined with farmyard manure (NPM) under continuous winter wheat were separated using settling tube apparatus. Results showed that the application of long-term P fertilization had no apparent effects on promoting the mass proportion of soil aggregates except for >250 μm, where the NP and NPM treatments significantly increased the mass proportion by 60% and 70% over CK, respectively. Compared with CK, P fertilizer (NP and NPM) treatments significantly increased organic P (Po) contents in each size aggregate. In particular, mean labile Po increased by 35% and 246%, moderately labile Po by 125% and 161%, nonlabile Po by 105% and 170% and total Po (TPo) by 101% and 178%, respectively, under NP and NPM treatments, respectively. There was a significant correlation between soil organic carbon (SOC) and Po fractions. SOC was exponentially positively correlated with labile Po but linearly positively correlated with moderately labile Po, nonlabile Po and TPo fractions among soil aggregates. A reduced C:Po ratio (<100) in soil aggregates among treatment indicates a large amount of available P accumulated in soils, and soil P loss risk in the study site is still high. Our results show that the Po pool measured by sequential chemical fractionation may represent an important, yet often overlooked, source of P in agriculture ecosystems. According to the result, long-term mineral P fertilizer combined with organic amendments better sustains soil structural stability in large aggregates, contributing more Po availability in the moderately labile P followed by labile P in soil aggregates.     

Nitrogen and/or phosphorus fertilization effects on organic carbon and mineral contents in the rhizosphere of field grown sorghum

The effects of nitrogen (N) and/or phosphorus (P) fertilizers on the nutritional status in the rhizosphere were studied by monitoring throughout the growth period the concentrations of organic carbon (C), inorganic N, NaHCO₃ extractable P, exchangeable K, Ca, and Mg in sorghum (Sorghum bicolor L. Moench) down in an Alfisol field, and of all these elements except for extractable P, and exchangeable Ca in a Vertisol field in semi-arid tropical India. These concentrations were compared between the rhizosphere soil and bulk soil of sorghum grown in both fields.

Organic C content of the rhizosphere soil increased with plant age and was significantly higher than that in the bulk soil throughout the growth of sorghum, but it was not affected by the rates of N or P fertilizer. Inorganic N concentration in the rhizosphere soil was significantly higher than that in the bulk soil until maturity in sorghum. The content of available P in the rhizosphere soil was significantly higher than in the bulk soil after the middle of the growth stage. Its average concentration in the rhizosphere soil across growth stages was significantly higher than in the bulk soil, which contradicts the observation in many reports that there is a depletion of P in the rhizosphere soil. The concentration of three exchangeable cations, K, Ca, and Mg, showed different patterns in the rhizosphere and the bulk soils. The concentration of K was almost constantly higher in the rhizosphere soil than in the bulk soil, Ca concentration was not different between the two soils, and Mg concentration was significantly higher in the bulk soil than in the rhizosphere soil. The reasons for these discrepancies cannot be explained at present. The concentrations of these cations were not affected by the rate of N or P fertilizer except for Mg at a later growth stage. The differences between rhizosphere and bulk soils in Alfisol were similar to those in Yertisol with respect to the concentration of organic C, inorganic N, and exchangeable K and Mg.     

Assessing soil P fractions changes with long-term phosphorus fertilization related to crop yield of soybean and maize

Long-term P Fertiliser application increases soil phosphorus (P) labile fractions, which can be associated with crop P uptake and grain yield and are useful to improve fertilizer recommendations. Research aims were to evaluate in long-term experiments with different P Fertiliser application in a Mollisol and a Vertisol: (a) the changes of soil P fractions and (b) the relationship between soil P fractions with long-term P Fertiliser application, with accumulated apparent P budget, grain P, total P uptake, soybean (Glycine max L.Merr.) and maize (Zea mays L.) grain yield. Soil P fractions were measured after 1 and 9 year since the beginning of the long-term experiments. Experiments included an initial Fertiliser application rate of 200 kg P ha⁻¹ and annual P Fertiliser application rate of 36 kg P ha⁻¹. Bray1-P, total, organic, and inorganic P in fine (<53 μm) and coarse (>53 μm) (CF) soil fractions, and in NaHCO₃ extract were measured. Initial P Fertiliser application increased inorganic and total P fractions. However, Bray1-P, total P in NaHCO₃ extract and in the CF were the fractions that most increased with continuous long-term P Fertiliser application in both sites. In the Mollisol, maize grain yield was unrelated to long-term P Fertiliser application. In the Vertisol, total P in NaHCO₃ extract, and total and organic P in the CF were more closely related to soybean grain yield than Bray1-P. We proposed soil P indices of labile inorganic and organic P that showed close relationships with soybean grain yield and may be useful to improve the diagnosis of P soil fertility.     

磷素吸附特性演变及其与土壤磷素形态、土壤有机碳含量的关系

在黄土旱塬区长期试验(1985-1997年)中,选取对照(不施肥,CK)、磷肥(P2O5.60.kg/hm2,P)、氮肥(N.120kg／hm2,N)、氮磷(N,120.kg／hm2,P2O5,60.kg/hm2,NP)、氮磷有机肥(N.120.kg/hm2,P2O560.kg/hm2,有机肥75.t／hm2,NPM),种植方式为冬小麦连作的5种有代表性的施肥处理,研究了石灰性土壤磷素吸附特性的演变及其与土壤磷素形态、土壤有机碳(SOC)含量的关系。结果表明,P素的最大吸附量(Qm),1997年对照(CK)、N处理比1985年分别提高了18％和14％;而P、NP和NPM处理分别降低了26％、13％和24％。吸附能常数(k值)随时间延长,对照和N处理相对稳定,P和NP处理呈升高趋势,而NPM处理有降低趋势。土壤磷素吸附饱和度(DPS)和零净吸附磷浓度(EPC0)对照和N处理随时间延长呈降低趋势,P、NP和NPM处理呈升高趋势。Qm与Ca8-P、Al-P存在极显著相关关系(P0.001),与Ca2-P、Pe-P存在显著相关关系(P0.05)。Ca2-P、有机磷含量变化与土壤DPS的相关性达到显著水平(P0.05)。EPC0只与有机磷间存在显著的相关关系(P0.05)。Qm、DPS和EPC0变化与SOC存在显著或极显著的线性相关关系(P0.001)。     

外源腐殖酸对棕壤有机磷组分的影响

采用Bowman和Cole提出的有机磷分组方法,对施入外源腐殖酸条件下,不同时期棕壤有机磷的组成变化进行测定。结果表明,施入外源腐殖酸,在培养的各个时期,有机磷各组分所占比例的基本格局没有改变,依然是中等活性有机磷>中等稳定性有机磷>高稳性有机磷>活性有机磷。施入外源腐殖酸后,在培养的30 d,活性有机磷均下降;在培养的60 d和90 d,施入高量腐殖酸的土壤,活性有机磷升高。施入外源腐殖酸,在培养的各个时期均可明显增加中等活性有机磷的含量,特别是在施入高量腐殖酸时增加的最多;同时还可降低中等稳定性有机磷的含量,在施入高量腐殖酸时降低的最多。     

外源腐殖酸对棕壤有机磷组分的影响

采用Bowman和Cole提出的有机磷分组方法，对施人外源腐殖酸条件下，不同时期棕壤有机磷的组成变化进行测定。结果表明，施入外源腐殖酸，在培养的各个时期，有机磷各组分所占比例的基本格局没有改变，依然是中等活性有机磷〉中等稳定性有机磷〉高稳性有机磷〉活性有机磷。施入外源腐殖酸后，在培养的30d，活性有机磷均下降；在培养的60d和90d，施入高量腐殖酸的土壤，活性有机磷升高。施入外源腐殖酸，在培养的各个时期均可明显增加中等活性有机磷的含量，特别是在施入高量腐殖酸时增加的最多；同时还可降低中等稳定性有机磷的含量，在施入高量腐殖酸时降低的最多。     

Assessing the bioavailability of dissolved organic phosphorus in pasture and cultivated soils treated with different rates of nitrogen fertiliser

A proportion of dissolved organic phosphorus (DOP) in soil leachates is readily available for uptake by aquatic organisms and, therefore, can represent a hazard to surface water quality. A study was conducted to characterise DOP in water extracts and soil P fractions of lysimeter soils (pasture before and after, and cultivated soil after leaching to simulate a wet winter-autumn) from a field trial. Data on DOP in drainage waters from the field trial were also generated. In water extracts, used as a surrogate for soil solution and drainage water, 70-90% of the total dissolved P (TDP) concentration was made up of DOP, of which 40% was hydrolysable by phosphatase enzymes. Proportions of hydrolysable DOP to TDP in drainage waters of the field trial were less than in water extracts due to enhanced DRP loss via dung inputs, but still large at 35% of DOP. Analysis of lysimeter soils by sequential fractionation indicated that several organic P fractions changed with land use and due to leaching. Further investigation using NaOH-EDTA extracts and ³¹P nuclear magnetic resonance spectroscopy indicated that the greatest changes were a decrease in the concentrations of orthophosphate diester P and an increase in orthophosphate monoester P. This was attributed to mineralization by cultivation and plant roots and also to the leaching of mobile diester P. This study suggests that in such soils with a dynamic soil organic P pool, the concentration of readily bioavailable P in soil solution and drainage waters and the potential to impair surface water quality cannot be determined from the DRP concentration alone.     

Phosphorus bioavailability of biochars produced by thermo‐chemical conversion

Recycling of P is a common strategy in efficient use of P. The aims of our investigation were to study the P extractability of biochars produced by low temperature conversion and to determine the effect of soda application on low‐temperature conversion of organic compounds and the bioavailability of P to rye grass (Lolium perenne L., cv. Grazer). In this study canola cake, dried distillers grains with solubles, and meat‐and‐bone meal were converted to biochars with thermo‐chemical conversion at 400°C. The P availability was measured in terms of solubility in water, 2% citric, and 2% formic acid, and in a pot experiment with rye grass (Lolium perenne L.) which was cut three times. Application of 8% (w/w) soda to the process of thermo‐chemical conversion of canola cake, dried distillers grains with soluble and meat‐and‐bone meal resulted in an increase of water‐, 2% citric‐, and 2% formic‐acid‐extractable P in the biochars. In contrast to the application of soda, addition of 12% wood ash (w/w) to the conversion of dried distillers grains with solubles resulted in a lower increase of water‐soluble P in the corresponding biochar compared to processing biochar without additives. Addition of biochar P (100 mg P [kg soil]^–1) to a Luvisol resulted in an increase of CAL‐extractable soil P. The P uptake of rye grass from biochars produced with the addition of soda was as effective as basic slag and MgNH₄ phosphate fertilizers and even better than rock phosphate.     

Long-term organic phosphorus mineralization in Spodosols under forests and its relation to carbon and nitrogen mineralization

In forest soils where a large fraction of total phosphorus (P) is in organic forms, soil micro-organisms play a major role in the P cycle and plant availability since they mediate organic P transformations. However, the correct assessment of organic P mineralization is usually a challenging task because mineralized P is rapidly sorbed and most mineralization fluxes are very weak. The objectives of the present work were to quantify in five forest Spodosols at soil depths of 0-15 cm net mineralization of total organic P and the resulting increase in plant available inorganic P and to verify whether net or gross P mineralization could be estimated using the C or N mineralization rates. Net mineralization of total organic P was derived from the net changes in microbial P and gross mineralization of P in dead soil organic matter. We studied very low P-sorbing soils enabling us to use lower extractants to assess the change in total inorganic P as a result of gross mineralization of P in dead soil organic matter. In addition, to enable detection of gross mineralization of P in dead soil organic matter, a long-term incubation (517 days) experiment was carried out. At the beginning of the experiment, total P contents of the soils were very low (19-51 μg g⁻¹) and were essentially present as organic P (17-44 μg g⁻¹, 85-91%) or microbial P (6-14 μg g⁻¹; 24-39%). Conversely, the initial contents of inorganic P were low (2-7 μg g⁻¹; 9-15%). The net changes in the pool size of microbial P during the 517 days of incubation (4-8 μg g⁻¹) and the amounts of P resulting from gross mineralization of dead soil organic matter (0.001-0.018 μg g⁻¹ day⁻¹; 0.4-9.5 μg g⁻¹ for the entire incubation period) were considerable compared to the initial amounts of organic P and also when compared to the initial diffusive iP fraction (<0.3 μg g⁻¹). Diffusive iP corresponds to the phosphate ions that can be transferred from the solid constituents to the soil solution under a gradient of concentration. Net mineralization of organic P induced an important increase in iP in soil solution (0.6-10 μg g⁻¹; 600-5000% increase) and lower increases in diffusive iP fractions (0.3-5 μg g⁻¹; 300-2000% increase), soil solid constituents having an extremely low reactivity relative to iP. Therefore, soil micro-organisms and organic P transformations play a major role in the bioavailability of P in these forest soils. In our study, the dead soil organic matter was defined as a recalcitrant organic fraction. Probably because gross mineralization of P from this recalcitrant organic fraction was mainly driven by the micro-organisms’ needs for energy, the rates of gross mineralization of C, N and P in the recalcitrant organic fraction were similar. Indirect estimation of gross mineralization of P in dead soil organic matter using the gross C mineralization rate seems thus an alternative method for the studied soils. However, additional studies are needed to verify this alternative method in other soils. No relationships were found between microbial P release and microbial C and N releases.     

Content of organic carbon and total nitrogen inStagnic Albeluvisols depending on fertilization

Abstract

The content of soil organic carbon (SOC) and total nitrogen (N_tot) was studied in a long-term field experiment with a three-field crop rotation (potato – spring wheat – spring barley) set up on arable sandy loam Stagnic Albeluvisol at Eerika, Tartu, Estonia. The studied factors were: (A) organic fertilizers with three treatments: (i) without organic fertilizer, (ii) farmyard manure (60 t ha^?1) used in every third year, and (iii) different organic (alternative) fertilizers (beet leaves + straw; pure beet leaves; slurry + straw; cereal straw) and (B) mineral nitrogen fertilizer with the rates: N-0; N-40; N-80; N-120 and N-160 kg ha^?1. The study years were 1993, 1996 and 1999. The average content of SOC (1.03%) was significantly influenced by the use of organic fertilizers. Only N_tot (mean value 0.110%) was influenced also by fertilization with mineral nitrogen. The C/N ratio (mean value 9.5) reflected changes in the content of SOC and N_tot