不同调理剂施用对富磷土壤磷素吸收及其形态变化影响

针对集约化设施土壤中磷素过度累积,本文开展盆栽试验,探究不同类型土壤调理剂施用对糯玉米干物质积累、磷素吸收及土壤磷素形态变化的影响。结果表明,生物质炭70%+明矾30% 处理玉米的长势最好,其盆干生物量最高为44.6 g/plant,显著高于对照处理19.57%。土壤总磷和水溶性磷含量在施用调理剂后与种植前相比均有不同程度的降低。在土壤无机磷组分变化方面,明矾100% 与生物质炭100% 处理均提高了缓效性磷源的含量,生物质炭70%+明矾30% 处理显著提高了速效性磷源含量。生物质炭70%+明矾30%、生物质炭30%+腐植酸30%+明矾30% 处理可以有效抑制土壤碱性磷酸酶的活性,同时抑制土壤有机磷素的矿化。综合来看,生物质炭70%+明矾30% 处理在释放土壤潜在性磷源、提高土壤速效性磷源、促进作物磷素吸收、提高作物干物质量积累等方面的综合表现较好。     

Barley growth in response to potassium fertilization of soil with long term application of sewage sludge

Application of sludges to agricultural land depressed plant growth despite its beneficial effects on crop production. Hence it remained to be determined whether sludge application induced any adverse effect on crop nutrition or growth. Thus the growth response of barley on an Andosol to which two kinds of sewage sludge compost had been applied for 17 y was tested in pot experiments with and without application of chemical K fertilizer. The addition of K in the sewage sludge composts resulted in the improvement of plant growth, high dry matter production and increase of total K content both in plant and soil compared to the materials without K application. It was assumed that long term application of sewage sludge requires chemical fertilizer amendment for crop production.     

Interactions of gamma‐irradiated sewage,nitrogen and phosphorus for Sorghum on a calcareous soil

Abstract

The interaction of gamma‐irradiated sewage sludge, nitrogen and phosphorus fertilizers on dry matter production, phosphorus concentration and phosphorus uptake of sorghum was examined. Three crops of sorghum were grown in the greenhouse in 19 1 plastic buckets. The phosphorus and sludge treatments were applied at the initiation of the experiment only. Nitrogen was applied to the corresponding nitrogen treatment pots before each of the three croppings.

There was a significant nitrogen x sewage interaction for dry matter production, phosphorus concentration and phosphorus uptake in each harvest. There was a significant phosphorus sewage sludge interaction in the first harvest for phosphorus uptake. All other possible interactions were not statistically significant. The 67 metric ton/ha sludge rate produced nearly the same yield as the nitrogen treatment. In the first harvest, sludge significantly increased plant phosphorus uptake from the fertilizer phosphorus. The phosphorus uptake in sorghum from 472 and 944 kg P/ha from the sludge treatments was comparable to that from 1299 and 2598 kg P/ha from triple superphosphate.     

The effect of thiosulfate on phosphorus availability and uptake by plants

A growth chamber experiment was conducted to examine the effect that banding urea or a thiosulfate source with monoammonium phosphate had upon fertilizer phosphorus uptake and dry matter yield of barley and rapeseed. For barley, fertilizer phosphorus uptake and dry matter yield were significantly increased when a thiosulfate source was banded with monoammonium phosphate, but not when urea was banded with monoammonium phosphate. Fertilizer phosphorus uptake and dry matter yield of rapeseed were not significantly affected by banding either a thiosulfate source or urea with monoammonium phosphate.     

Effect of Arbuscular Mycorrhizal Fungi and Phosphate-Solubilizing Bacteria Consortia Associated with Phospho-Compost on Phosphorus Solubilization and Growth of Tomato Seedlings (Solanum lycopersicum L.)

ABSTRACT

The exploitation of phosphate mines generates an important quantity of phosphate sludge that remains accumulated and not valorized. In this context, composting with organic matter and rhizospheric microorganisms offers an interesting alternative and that is more sustainable for agriculture. This work aims to investigate the synergetic effect of arbuscular mycorrhizal fungi (AMF), phosphate-solubilizing bacteria (PSB) and phospho-compost (PC), produced from phosphate-laundered sludge and organic wastes, and their combination on plant growth, phosphorus solubilization and phosphatase activities (alkaline and acid). Inoculated mycorrhizae and bacteria strains used in this study were selected from plant rhizosphere grown on phosphate-laundered sludge. Significant (p < .05) increases in plant growth was observed when inoculated with both consortia and PC (PC+ PSB+ AMF) similar to those recorded in plants amended with chemical fertilizer. Tripartite inoculated tomato had a significantly (p < .05) higher shoot height; shoot and root dry weight, root colonization and available P content, than the control. Co-inoculation with PC and AMF greatly increased alkaline phosphatase activity and the rate of mycorrhizal intensity. We conclude that PC and endophytic AMF and PSB consortia contribute to a tripartite inoculation in tomato seedlings and are coordinately involved in plant growth and phosphorus solubilization. These results open up promising prospects for using formulate phospho-compost enriched with phosphorus-solubilizing microorganisms (PSM) in crop cultivation as biofertilizers to solve problems of phosphate-laundered sludge accumulation.     

Effects of Alum-treated Waste Water Sludge on Barley Growth

Alum sludge derived from a municipal wastewater plant was used as a soil amendment in a greenhouse study with barley (Hordeum vulgare) as the test crop. Treatment variables included the soil pH (4.5, 5.1 and 6.5), the amount of Al in the sludge (control = 30 mg Al_T/g; alum sludges = 38 and 52 mg Al_T/g), and the sludge application rate (100 and 270 kg N_T/ha). Soil amendment with the two alum sludges reduced soil pH, increased Al³⁺ activity in the soil solution, and reduced barley growth over the 6-week experiment. Barley growth decreased as the Al³⁺ activity in the sludged soil solution increased, but for a given Al³⁺ the phytotoxicity of Al was markedly pH dependent. For example, at a pH of 5.0 ± 0.1 an Al³⁺ activity of 0.5 μM was sufficient to inhibit plant growth by about 50% this IC₅₀ value increased five-fold to about 2.5 μM when the soil pH was 4.5 ± 0.1. This decrease in the toxicity of Al50 with acidification was explained in terms of a competitive interaction between the H⁺-ion and Al³⁺ at the root surface. Stepwise multiple regression allowed the prediction of aerial leaf biomass from soil pH and sludge application rate.     

膜下滴灌水肥耦合促进番茄养分吸收及生长

研究膜下滴灌不同水肥调控措施对日光温室番茄生长、产量、养分吸收利用的影响,为温室番茄水肥科学管理提供依据。设灌水(W)和施肥(F:N-P2O5-K2O)2因素,以常规沟灌施肥(W1:100%ET0,F1:240-120-150kg/hm2,ET0为参考作物蒸发蒸腾量)为对照(Control,CK),3个滴灌水量(W1:100%ET0、W2:75%ET0、W3:50%ET0)和3个施肥水平(F1:240-120-150 kg/hm2、F2:180-90-112.5 kg/hm2、F3:120-60-75 kg/hm2)。结果表明,滴灌施肥(W1F1)比CK处理的干物质量、产量和肥料偏生产力(PFP,partial factor productivity of fertilizer)分别增加60.0%、46.9%和47.0%,氮、磷和钾吸收量是CK的1.82~2.41、1.56~2.03和1.36~1.90倍。滴灌施肥下,W1F2干物质量最大(9 258.3 kg/hm2),W1和W2较W3增产19.0%和6.5%,F1和F2较F3增产18.3%和12.9%。生育期内,植株氮、磷和钾吸收量均随灌水量和施肥量的增加而增大(第二果膨大期,F2处理磷和钾吸收量最大除外),灌水量越大,养分利用效率(NUE,nutrient use efficiency)越小,吸收效率(UPE,nutrient uptake efficiency)和PFP越大,施肥量越大,NUE、UPE及PFP均减小。综合分析,滴灌施肥增产效果明显,W1F2(100%ET0,N-P2O5-K2O为180-90-112.5 kg/hm2)处理干物质量最大,有较大的增产潜力,UPE和PFP较高,是适宜的灌水施肥组合。     

秸秆等氮量替代化肥对土壤水分和玉米干物质积累的影响

为了探究秸秆等氮量替代化肥的可行性及其对土壤水分和玉米干物质积累的影响,进行连续6年的大田试验,2020年是施肥第5年,2021年是施肥第6年,保持225 kg/hm²的等氮量,设置5个施肥处理：CK(单施化肥,100%化肥氮)、S25(25%秸秆氮+75%化肥氮)、S50(50%秸秆氮+50%化肥氮)、S75(75%秸秆氮+25%化肥氮)、S100(100%秸秆氮),研究秸秆等氮量替代化肥对土壤贮水量、水分利用效率、土壤耗水量、土壤养分和玉米干物质积累量的影响。结果表明：(1)2020年试验中,在播种前和灌浆期,0—80 cm土层土壤贮水量为S50>S25>CK>S100>S75;在大喇叭口期和抽雄期为S50>S25>CK>S75>S100;在成熟期为S50>CK>S25>S100>S75;在2021年试验中,大喇叭口期,0—80 cm土层土壤贮水量为S25>S50>S100>CK>S75;在抽雄期,0—80 cm土层土壤贮水量为S25>S50>CK>...     

HIGH FERTILIZER RATES INCREASE SUSCEPTIBILITY OF TEA TO WATER STRESS

A study to determine the association of fertilizer with soil water deficit in tea [Camellia sinensis (L.) O. Kuntze] was conducted in a rain-out shelter using potted plants, in which five rates of fertilizer (0, 75, 150, 225 and 300 kg Nitrogen ha^?1) and six levels of soil water content (38, 34, 30, 26, 22 and 18% v/v) were applied in a complete randomized design and replicated three times. The soil water treatment was maintained for a period of 12 weeks during which shoot growth, plant water relations, and dry matter partitioning in tea were determined. A parallel field experiment with the above fertilizer rates was conducted at three sites in which shoot density and shoot weight were determined during the dry season. Fertilizer improved leaf-to-root and leaf-to-total mass ratios (P < 0.001), reduced shoot growth, shoot water potential and specific leaf area (P < 0.001). The fertilizer exacerbated drought effect on tea through disproportionate assimilate partitioning which consequently weakened the ability of tea to tolerate water stress. Results suggest an indirect contribution of fertilizer supply to drought susceptibility in tea.     

施肥对冬小麦的水分调亏灌溉效应的影响

为了研究冬小麦在不同施肥条件下的调亏灌溉效应,通过小区试验设置了不施肥(F0)、单施复合肥(F1)和复合肥+有机肥配施(F2)三种施肥处理,并在返青-拔节期对冬小麦进行了适当的水分亏缺处理。结果表明,与F0和F1处理相比,F2处理的小麦,在水分亏缺期间光合速率没有受到显著影响,但复水后光合速率表现超补偿效应。到花期时,F2处理的调亏灌溉下小麦的叶面积、株高、每茎干质量和成穗数与未调亏灌溉时没有显著差别。抽穗后,在充分供水条件下,返青-拔节期水分亏缺对F2处理小麦的产量没有显著影响,但对F0和F1处理小麦的产量有显著负效应;在自然干旱条件下,水分亏缺对F2处理小麦的产量有显著的正效应。F2处理下,小麦的稳产性显著高于F0和F1处理。可见,在3种施肥处理条件下,复合肥与有机肥配施处理时冬小麦的调亏灌溉效应最好。     

Response of early corn growth to fertilizer phosphorus rates and placement methods

Previous research showed that applying fertilizer phosphorus (P) to the soil in concentrated subsurface bands increased P availability to crops compared to a surface application. Early growth responses of corn (Zea mays L.) plants were measured after 28 days of growth in pots in a greenhouse for single band, two single bands, injection, and surface fertilizer P placement methods. Fertilizer P was applied at the rates of 0, 12, and 24 mg P/kg soil for each method for three different soils. Shoot dry matter weight and nitrogen (N) and P uptake increased for all placement methods regardless of initial soil test P level. However, growth parameters were greater for the banded and injection methods. Response parameters were minimally influenced by the surface P application, but some fertilizer P from the surface application leached through small desiccation cracks after daily additions of water. This probably increased P availability slightly. Shoot dry matter production efficiency and shoot N/P ratio were higher for the surface P placement method and for the unfertilized P treatments. Overall growth responses to fertilizer P rates were less effective in soils with higher initial soil test P levels.     

The coupling effect of water and fertilizer on the growth of tea plants [Camellia sinensis (L.) O. Kuntz]

Water and fertilizer are the two main factors promoting the rapid growth of tea plants (Camellia sinensis). Using two-year-old rooted cutting of Wuniuzao (Camellia sinensis) as experimental materials, “311-B” D-saturation optimization design was carried out using 5, 4, and 4 levels of irrigation regimes, fertilizer nitrogen, and fertilizer phosphorus, with six replications. The raw date obtained was used of quadratic regression fitting for the plant height, new-tip length and dry matter weight. The coupling effects of these three factors [nitrogen (N0, water, and phosphorus (P)] on dry matter weight were significant. The effect order of single factor on dry matter weight was N>water>P, while the interactive effect order on the dry matter weight was N and water>P and water>N and P. An optimal combination with 0.485 g·pot^?1 N, 0.274 g·pot^?1 P, and once every 4-5 days of watering was proposed for the highest tea dry matter yield.     

三种不同聚合度组成的聚磷酸铵对玉米苗期生长的影响

【目的】了解不同聚合度组成的聚磷酸铵(APP)作种肥对玉米苗期生长的影响。【方法】以磷酸一铵(简称MAP)作对照,比较了3种APP [(简称APP1,低中聚成分为主)、APP2 (中高聚成分为主)、APP3 (低中高聚成分均匀分布)]及APP与MAP配施(APP∶MAP=1∶1,P_2O_5质量比)在砖红壤上作玉米种肥的效果。试验设置了CK (不施磷肥)、MAP、APP1、APP2、APP3、APP1∶MAP、APP2∶MAP和APP3∶MAP共8个处理。播种40 d后,收取玉米苗期植株,采集土壤样品,分别测定玉米植株株高、茎粗、地上和地下部干重、土壤全磷及有效磷含量、植株磷吸收量和磷利用率等指标。【结果】不同聚合度组成APP对玉米苗期生长具有显著影响。单独施用APP时,以APP3的肥效最好,MAP和APP1居中,APP2最差。APP3可以稳定供磷,玉米株高、干重、磷吸收量均最高,表明聚合度组成均匀分布的APP作种肥效果最佳。与单独施用APP相比,APP配施MAP后,显著提高玉米生物产量和磷吸收量,其中以APP3配施MAP效果最好,与MAP相比,APP3∶MAP处理的干物质量和磷利用率分别提高了21.3%、81.6%。【结论】APP作为种肥施用时,聚合度组成会显著影响肥效,以聚合度组成分布均匀的APP效果最佳。此外,配施MAP对中高聚APP的肥效有显著的促进作用。     

干热河谷土壤酶活性和车轴草生长对氮磷添加的响应

为了探讨干热河谷地区不同土地利用类型下土壤酶活性和植物生长对氮磷添加的响应以及二者之间的联系,采集了元谋干热河谷6种不同土地利用类型土壤,包括灌丛、草地、森林、新开垦农田(新农)、常年耕作农田(常农)、侵蚀裸地(裸地),并利用盆栽探索了土壤酶活性和车轴草(Trifolium repens L.)生长对氮(N)、磷(P)、氮磷(N+P)处理的响应特征。结果表明:(1)植物生物量受土地利用类型和处理双重因素影响,两者的交互作用对植物生物量具有显著作用。(2)除农田土壤(新农和常农)外,其他土地利用类型的土壤上植物生长受到养分添加的显著影响,其中添加P处理的生物量显著高于对照; 而N+P处理又显著高于单一的P添加; 而新农和常农不同养分处理间植物生物量差异不显著。(3)土壤酶活性受土地利用类型显著影响,但是不同养分添加处理之间土壤酶活性差异不显著; 土壤酶活性与植物生物量无显著相关性。综上,干热河谷土壤中植物生长的限制养分主要为磷,然而土壤酶活性则不受氮磷养分的限制,其活性主要与土地利用类型有关。     

Paper Mill Sludge Composting and Compost Utilization

Economically viable and environmentally acceptable methods to recycle organic wastes are needed by the pulp and paper industry. We assessed the potential for composting the Virginia Fibre Corporation's (VFC) combined primary and secondary dewatered paper mill sludge (PMS) and evaluated the suitability of the finished product as a potting soil substitute. Composting treatments were: 1) PMS with no supplemental N (control), 2) PMS + 15 kg N/Mg PMS (dry weight), and 3) PMS + 30 kg N/Mg PMS (dry weight). Composting was conducted for 129 days and treatment effects were evaluated by windrow temperature trends. A container plant growth study employing various particle size fractions and proportions of the control PMS compost and a commercial potting medium (Promix^tm) was conducted in a greenhouse to assess the capability of the compost to support growth of radish (Raphanus sativus L.), snap bean (Phaseolus vulgaris L.), marigold (Tagetes erecta L.), and green pepper (Capsicum sp.). Windrow temperatures were lower with no supplemental N than with the N additions during the initial three weeks and were higher with increasing N rate during the last month of composting, which indicated that the unamended sludge may have been N-limited for maximum biological activity. Reduced temperatures in the high N treatments during the midpoint of the composting process may have been induced by ammonia toxicity. However, cured compost chemical properties and stability were not influenced by treatment and were indicative of good quality compost. The lower amount of plant-available water and greater amounts of plant-available nutrients supplied by the compost than the commercial potting medium resulted in less dry matter produced by all plants except green pepper, whose higher nutrient needs were supplied better by the compost than the commercial potting medium alone. Therefore, the paper mill sludge compost may best be used as an organic fertilizer, soil amendment, or supplemental nutrient source for potting media, rather than as a potting medium alone.     

硅磷配施对低磷土壤春玉米干物质积累、 分配及产量的影响

以玉米品种‘正红2号’和‘正红115’为材料,通过2014年和2015年的田间小区定位试验,研究低磷土壤条件下,硅磷肥配施对玉米拔节期和吐丝期的净光合速率、蒸腾速率和叶面积指数,拔节期、吐丝期、灌浆期和成熟期干物质积累和分配,产量及产量构成因素的影响,探讨施硅及硅磷配施的增产效果。结果显示,与对照(不施磷肥和硅肥)相比,施磷、施硅和硅磷配施处理均可提高玉米拔节期和吐丝期的叶面积指数和净光合速率,增加拔节期、吐丝期、灌浆期和成熟期各生育阶段的干物质积累量,降低灌浆期和成熟期叶片的干物质分配比例和灌浆期茎鞘的干物质分配比例,提高籽粒干物质分配比例和收获指数,降低秃尖长度,增加穗长,最终提高穗粒数、千粒重和籽粒产量;其中施用磷肥增加或降低上述指标的效应明显大于施用硅肥,硅磷配施增加或降低上述指标的效应又明显大于单施磷肥或单施硅肥,硅和磷表现出明显的协同作用和配合效应。2014年和2015年玉米籽粒产量均与拔节期、吐丝期、灌浆期和成熟期干物质积累量呈显著正相关;与单施磷肥相比,硅磷配施处理分别增产1 288.57 kg·hm~(-2)(2014年)和1 313.61 kg·hm~(-2)(2015年),且2015年的增幅明显大于2014年,硅、磷表现出稳定的增产效应。综上所述,在四川丘陵低磷土壤条件下,合理进行硅磷肥配施,既能提高玉米生育前期物质生产能力和干物质积累量,又能改善生育后期干物质在玉米各器官中的分配,促进籽粒灌浆结实,最终提高籽粒产量。     

Vermicompost from municipal sewage sludge affects growth and mineral nutrition of winter rye (Secale cereale) plants

The aim of the study was to investigate sewage sludge vermicompost application effects on growth and mineral nutrition of winter rye (Secale cereale L.) plants as compared to two initial levels of mineral nutrient availability, pure sand and sand enriched with inorganic nutrients at the optimal level. Addition of sewage sludge vermicompost significantly inhibited rye seed germination at 20 to 50% sand substitution independently on mineral nutrient supplement. Growth inhibition was evident at early stages of plant development. However, at the later stages, sewage sludge vermicompost acted both as mineral fertilizer and plant growth-promoting agent. Significant stimulation of mineral uptake was seen only at high rates of vermicompost substitution (40 and 50%) already causing decrease in shoot dry matter accumulation. Vermicompost substitution resulted in a significant increase of leaf chlorophyll content. Beneficial effect of sewage sludge vermicompost in conditions of optimal mineral supply can result mainly from plant growth-promoting activity.     

施磷水平和接种AMF与解磷细菌对苜蓿产量及磷素利用效率的影响

为探讨不同施磷水平下接种丛枝菌根真菌（Arbuscular Mycorrhizae Fungi,AMF）与解磷细菌对苜蓿干物质产量及其磷素利用效率的影响,筛选出苜蓿最佳的施肥模式,为紫花苜蓿高效生产及高效复合型菌肥的研制提供理论依据。该研究试验采用双因素随机区组设计,AMF选用摩西管柄囊霉,解磷细菌选用巨大芽孢杆菌,设置4个施菌水平：分别为接种摩西管柄囊霉（Fm,J1）、巨大芽孢杆菌（Bm,J2）、混合菌种（Fm×Bm,J3）和未接菌处理对照组（J0）。施磷（P2O5）设置4个水平P0~P3分别为：0、50、100和150 mg/kg,菌磷互作共16个处理。结果表明：1）相同施菌条件下,苜蓿各茬次干物质产量、总干物质产量和植株磷含量均随施磷量的增加呈先增加后降低的趋势。除J2条件下,J2P1处理下的苜蓿总干物质产量达到最大值外,其他施菌条件下,苜蓿的总干物质产量均在P2处理达到最大,且施磷处理显著大于未施磷处理（P<0.05）。苜蓿的磷肥偏生产力及磷肥农学效率均随施磷量的增加呈逐渐降低的趋势,而土壤全磷含量和速效磷含量均随着施磷量的增多呈增加的趋势。2）相同施磷处理下,单接种菌处理和混合接种处理下苜蓿的干物质产量、植株磷含量、磷素利用效率、土壤全磷以及速效磷含量均显著大于不接菌处理（P<0.05）,其中总干物质产量、土壤全磷和速效磷含量均在J3处理达到最大值。根际土壤速效磷含量与干物质产量拟合的相关系数最大,拟合效果最好。土壤全磷、速效磷含量均与总干物质产量呈显著正相关。因此,当施磷量为100 mg/kg,混合接种AMF与解磷细菌能够显著增加苜蓿土壤磷素有效性,提高磷素利用效率,进而增加苜蓿的干物质产量。     

Low-cost and environmental-friendly Triticum aestivum-derived biochar for improving plant growth and soil fertility

ABSTRACT

Biochar and biochar–fertilizer concoction is imperative to subjugate reduced plant growth and soil fertility depletion which is a constraint for sustainable agriculture. The aspiration of the current research was to determine the plant growth response to wheat straw-derived biochar annexation in soils from two regions: Rawalpindi (semi-arid) and Thar (arid). Wheat straw (Triticum aestivum) was pyrolyzed at 300°C in a low-cost biochar retort kiln at different concentration rates (0%, 1%, 3%, and 7% by mass). Growth trend of Sorghum bicolor was observed in these soils for 40 days in a greenhouse. Fertilizer (NPK) (8.58% N, 4.39% P, and 3.48% K) was added to soil on the third day of seed germination. Soil physicochemical analysis, plant growth, and dry matter yield evaluation after the treatment signified the concomitant increase in dry matter yield along with enhanced soil fertility and plant growth.     

Phosphordüngewirkung eisenhaltiger Klärschlämme

<?show $38#Bo;>Phosphorus fertilization effect of sewage sludges treated with iron compounds The result of waste water treatment with iron salts are sewage sludges with higher P but also Fe contents. The effect of such sludges on P availability in soils is not clear and was, therefore, compared with CaHPO₄ as a P mineral fertilizer. In experiments (Mitscherlich pots, 6 kg soil) two sandy soils (pH 4.3 and 4.9), two luvisols ( pH 6.3 and 7.2), a loess (13 % CaCO₃), and quartz sand all differing in their P status were treated with two sewage sludges which differed in their molar Fe:P ratios (sludge Gö: 1:0.3, sludge Sh: 1:1.2). For sludge Gö the P elimination had been carried out with FeSO₄ and the sludge was stabilized with FeCl₃ + Ca(OH)₂ (filter press). For sludge Sh P was eliminated by FeCl₃ in the aerobic basin. The first crop was maize (total shoot dry matter), the second red clover. In case of sludge Sh both crops took up in comparison to CaHPO₄ the same amount of P from all substrates with the exception of quartz sand. The effect of sludge Gö was quite different: from the neutral luvisol soils maize was able to take up only 64—82 % P and red clover 77—82 % P only as compared to CaHPO₄. On the sandy soils maize and red clover grew after sludge Gö as good or better than after CaHPO₄ application and P uptake was quite similar (83—106 %). This result was concomitant to an increase of pH values (from 4.3 to 4.9, 4.9 to 5.6, respectively). The negative efficiency of P uptake in heavy soils after application of sludge Gö resulted from an increase of P sorption and decrease of orthophosphate concentration in soil solution. This sludge contains a high proportion of iron hydroxides/oxides with free sorption sites for P. In future P elimination from waste water should be done without iron salts. At least during the process of conditioning no Fe salts should be used.<?show $6#>