Effects of liming and fertilization on soil solution chemistry in North German forest ecosystems

The effect of aboveground liming and fertilization as well as ploughing and liming of forest soils on soil solution chemistry was studied in various experimental plots of the German Solling area. Due to low solubility of limestone, aboveground liming had only moderate effects on soil pH and base saturation of CEC. Calcium and Mg concentration increased and Ca/Al and Mg/Al ratios of the soil solution improved. Despite extreme doses of lime, nitrate leaching did not increase in the case of a beech plot. Elevated nitrate leaching was found in the case of a spruce and a beech plot previously fertilized with N. Nitrate concentrations are far from drinking water thresholds in the case of beech. Nitrate levels of soil solution of the unfertilized spruce plot are in the range of 3 to 8 mg L⁻¹. Liming did increase these values slightly in the first years, and nitrate levels reached those of the untreated plot in the following years. Ploughing connected with high liming doses obviously led to inhomogeneous distribution of lime. No significant deacidification of seepage water at a depth of 100 cm occurred because of leaching of sulfate from the industrial lime used. This was followed by Al-leaching. Nitrate levels slightly exceeded drinking water standards throughout the first winter period after the measure. The development of young trees was significantly improved.     

Effects of lining and fertilization on soil solution chemistry in North German Forest Ecosystems

The effect of aboveground liming and fertilization as well as ploughing and liming of forest soils on soil solution chemistry was studied in various experimental plots of the German Solling area. Due to low solubility of limestone, aboveground liming had only moderate effects on soil pH and base saturation of CEC. Calcium and Mg concentration increased and Ca/Al and Mg/Al ratios of the soil solution improved. Despite extreme doses of lime, nitrate leaching did not increase in the case of a beech plot. Elevated nitrate leaching was found in the case of a spruce and a beech plot previously fertilized with N. Nitrate concentrations are far from drinking water thresholds in the case of beech. Nitrate levels of soil solution of the unfertilized spruce plot are in the range of 3 to 8 mg L^–1. Liming did increase these values slightly in the first years, and nitrate levels reached those of the untreated plot in the following years. Ploughing connected with high liming doses obviously led to inhomogeneous distribution of lime. No significant deacidification of seepage water at a depth of 100 cm occurred because of leaching of sulfate from the industrial lime used. This was followed by Alleaching. Nitrate levels slightly exceeded drinking water standards throughout the first winter period after the measure. The development of young trees was significantly improved.     

Ion Equilibrium in the Soil Solution in Long-term Fertilization Experiment on Sandy Soil

In the conditions of long-term experiment carried out in the experimental field of Warsaw Agricultural University - SGGW at _ yczyn, ion concentration in the soil solution were examined as well as the relationships shaped between ions in the soil solution due to long-term diversified mineral and organic fertilization. Soil solution was obtained by the vacuum method and the concentration of particular ions in the soil solution was determined by the ICP method. Mineral and organic fertilization and liming significantly affected chemical composition of the soil solution and the relationships between particular ions in the soil solution. The lowest concentration of ions in the soil solution was observed in the control plots (not fertilized). Mineral and organic fertilization as well as liming caused the increase of ion concentration in the soil solution. In the plots with mineral fertilization alone K + and NH + 4 ions predominated in the cation structure in the soil solution. In the case of liming the share of Ca 2+ ions increased. Independently from the system of fertilization used, CI m and HCO m 3 ions predominated in the anion structure. The application of organic fertilization affected to the highest degree the concentration of aluminium ion in the soil solution significantly limiting the share of this ion in the cation structure.     

Biological and chemical properties of arable soils affected by long-term organic and inorganic fertilizer applications

 Using soils from field plots in four different arable crop experiments that have received combinations of manure, lime and inorganic N, P and K for up to 20 years, the effects of these fertilizers on soil chemical properties and estimates of soil microbial community size and activity were studied. The soil pH was increased or unaffected by the addition of organic manure plus inorganic fertilizers applied in conjunction with lime, but decreased in the absence of liming. The soil C and N contents were greater for all fertilized treatments compared to the control, yet in all cases the soil samples from fertilized plots had smaller C:N ratios than soil from the unfertilized plots. The soil concentrations of all the other inorganic nutrients measured were greater following fertilizer applications compared with the unfertilized plots, and this effect was most marked for P and K in soils from plots that had received the largest amounts of these nutrients as fertilizers. Both biomass C determined by chloroform fumigation and glucose-induced respiration tended to increase as a result of manure and inorganic fertilizer applications, although soils which received the largest additions of inorganic fertilizers in the absence of lime contained less biomass C than those to which lime had been added. Dehydrogenase activity was lower in soils that had received the largest amounts of fertilizers, and was further decreased in the absence of lime. This suggests that dehydrogenase activity was highly sensitive to the inhibitory effects associated with large fertilizer additions. Potential denitrification and anaerobic respiration determined in one soil were increased by fertilizer application but, as with both the microbial biomass and dehydrogenase activity, there were significant reductions in both N₂O and CO₂ production in soils which received the largest additions of inorganic fertilizers in the absence of lime. In contrast, the size of the denitrifying component of the soil microbial community, as indicated by denitrifying enzyme activity, was unaffected by the absence of lime at the largest rate of inorganic fertilizer applications. The results indicated differences in the composition or function of microbial communities in the soils in response to long-term organic and inorganic fertilization, especially when the soils were not limited. Received: 10 March 1998     

Flow and deformation behavior at the microscale of soils from several long‐term potassium fertilization trials in Germany

The effect of K fertilization on microstructural soil stability is rarely analyzed until now although the ambiguous impact on bulk soil structure was reported quite often, e.g., with regard to higher erodibility on the one hand and higher water storage on the other. Soil material from different long‐term fertilization trials in Germany was examined rheologically by means of an amplitude sweep test where the samples were subjected to oscillating shearing with increasing deflection. The resulting shear stress was recorded, and the maximum stress denoted the maximum shear strength of the sample. Results showed an ambiguous influence of K which depends strongly on the soil properties. On the one hand, an increased ion concentration in the soil solution leads to increasing attractive forces as defined by the DLVO theory and therefore higher shear resistance. With increasing desiccation, K⁺ like other salts can precipitate at the contact areas between particles and lead to cementation. On the other hand, K⁺ as a monovalent ion impedes covalent and ionic bonding between clay minerals which holds true for most of the examined soil types while only sandy soils showed an increase in soil strength due to K fertilization. Potassium depletion further resulted in increased interaction of fertilization with other impact factors, e.g., climate and soil properties. Thus, the destabilizing effect of K⁺ was more pronounced under liming as without liming. Subsequent modeling with selected soil parameters confirmed the high influence of matric potential. The modeling also revealed the interactions with other soil parameters, e.g., pH, oxides, texture, exchangeable cations as well as lack or surplus of K in relation to recommended K content. In conclusion, microstructural stability of soil depends on several soil parameters and requires the inclusion of many chemical and physical soil properties.     

Phosphoraustrag aus Niedermoorböden - Ergebnisse eines Lysimeterversuches ohne Pflanzenbewuchs

Leaching of phosphorus out of fen soils - Results from pot trials without growing plants In contrast to acid bog peat soils, fen soils with high content of iron, calcium und partially lime may fix phosphates in the same way as mineral soils. In model experiments without growing plants the quantity of leached phosphorus is determined. 0,4–0,5 kg P/ha are leached out of a slightly acid fen soil (pH 5,5) with 550 mm percolated water. The phosphate fertilizers (300 kg P/ha) Tripelphosphat, Novaphos, Hyperphos and Thomasphosphat have no influence on the amount of leached phosphorus. The phosphate is fixed in the depth of 0–10 cm, into which the fertilizers were mixed. However, from a very strongly acid fen soil (pH 3,0; limed in 0–10 cm to pH 4,5) with 1000 mm percolated water 25,8 kg P/ha are leached. The fertilization with Tripelphosphat and Novaphos increases the amount of leached phosphorus whereas the water insoluble phosphate fertilizers (Thomasphosphat and Hyperphos) have no influence. In a fen soil with high content of iron water soluble phosphate will be sorbed and fixed very rapidly, therefore only low parts of the water soluble phosphate fertilizers can be extracted with lactate solution (DL), in comparison to the water insoluble phosphates.     

Combined N,P, K fertilization and liming maximises crop productivity of acid loams in Lithuania

Crop response to fertilization and liming was investigated in field and pot trials on sandy loam Dystric Albeluvisols (pH 4.2–4.3). Treatments in the field trial were: 1, no fertilizer; 2, PK; 3, NK; 4, NP; 5, NPK; 6, lime; 7, lime+PK; 8, lime+NK; 9, lime+NP; 10, lime+NPK. In the pot trial, they were: 1, no fertilizer; 2, N; 3, P; 4, K; 5, NP; 6, NK; 7, PK; and 8, NPK applied to unlimed and limed soils. All treatments were in four replicates. Crops sensitive to soil acidity (winter wheat, fodder beet, spring barley and clover-timothy ley) and the less acid-sensitive winter rye, potatoes, oats and lupins and oats mixture were sown in the field trial. In the pot trial, the acid-sensitive spring barley and red clover, and the less acid-sensitive oats and lupin-oats served as the test crops. Combined application of fertilizers (NPK) increased yields of crops sensitive to soil acidity in plots receiving lime by 23%, and those of crops less sensitive to soil acidity by 18% in comparison to crops grown on unlimed soils. The results of pot experiments corroborated the field results. When N was applied alone, crop yields were always higher than those recorded for P or K treatments on both the unlimed and limed treatments. N application proved to be a prerequisite for high crop yields in the soils investigated. Thus, the efficiency of P and K fertilizers increased in the order NK<NP<NPK, with the effects being accentuated more in the limed than in the unlimed treatments. The results demonstrated the importance of multi-nutrient (NPK) fertilization in combination with liming for enhancement of high crop productivity in the unlimed soil investigated. N applied alone in combination with liming produced relatively good yields; hence, where resources are limited for the purchase of P and K fertilizers, applying N and lime can be a viable option in the short term.     

Effects of lime applications to parts of an upland catchment on soil properties and the chemistry of drainage waters

The liming of soils in the lower part of an upland catchment was found to have a major effect on both soil properties and the chemistry of drainage waters. Exchangeable Al was closely correlated with soil pH and showed a very steep rise from 2.6-4.8 meq 1⁻¹ over the pH range 5.5-4.5. As streams flowed from unimproved through improved land there was an increase in pH and the concentration of all major anions and basic cations. The greatest increase was in Ca (approximately 3.5-fold). The concentrations of all dissolved Al species decreased, with inorganic monomeric Al falling to near zero. Leachates were examined from soils representative of the most acidic and the least acidic. Calcium concentrations differed by almost tenfold. Aluminium was present in leachates from the limed soil, but most was unreactive and none was inorganic monomeric. Most of the Al leached from the acid soil was monomeric.
A model of soil acidification is proposed in which soil Ca is depleted at a rate of 8% of the exchangeable Ca per annum. The model predicts that liming a soil to neutrality would be likely to influence drainage water chemistry for 30-40 years and that the most acidic soils of the catchment show no net loss of Ca to drainage.     

Phosphorus Availability in Low-P and Acidic Soils as Affected by Liming and P Addition

Acidic soils typically suffer from high phosphorus (P) retention, a problem that can be dealt with using greater P fertilization, soil liming, or both. The aim of this work was to examine which of these practices bears the more beneficial result for Lolium perenne L. growth. In a pot experiment, five acidic soils were treated as follows: L0P0 (unamended control), L1P0 (liming only), L0P1 (P addition only), and L1P1 (both liming and P addition). We found that P amendment alone was sufficient to increase plant P levels when the initial soil P concentrations were low. Liming without P addition increased plant P satisfactorily only in the high-P soil. We conclude that P addition alone is a better practice than liming alone for improved plant growth conditions in acidic, low-P soils, unless there is relatively high P content in soil, in which case liming alone may be sufficient to increase P availability.     

Effects of Liming and Fertilization (N,PK) on Chemistry and Nitrogen Turnover in Acidic Forest Soils in SW Sweden

SW Sweden has very acidic forest soils because of deposition ofair-borne pollutants. Large-scale liming and fertilization have been proposed as countermeasures against a possible future development of forest decline. To test the effects of suggested treatments, liming (3 or 6 t ha¹) and fertilization with easily soluble PK (25 or 50 kg P, 80 or 160 kg K ha¹) or N(20 kg N ha¹ annually in the form of NH₄ NO₃) were applied in different combinations in four experiments in 30–60 yr-old Picea abies forests in SW Sweden. Four yearsafter the initial application of the fertilizers, samples were taken from the O-horizon and the two uppermost 5 cm thick layersof the mineral soil. Their pH(H₂O) and easily extractable Ca, Mg, K, P and inorganic N contents were analyzed. Samples werealso incubated to estimate net N mineralization and potential nitrification rates. Liming increased the pH by 0.6–1 unit in the O-horizon, and by 0.1 unit in the mineral soil. The Ca + Mg content increased by 15–25 kmol_c ha¹ (4–8 foldincrease) in the O-horizon of the limed plots, while an increaseof 5 kmol_c ha¹ (two-fold increase) was observed in theuppermost 5 cm of the mineral soil. Liming did not affect extractable P, K or inorganic N contents. Net N mineralization and potential nitrification rates in the O-horizon were enhanced 1.5- and 6-fold, respectively, by liming, but it had no apparenteffect in the mineral soil. N fertilization caused a slight increase (1.5 kg ha¹) in the content of inorganic N, buthad no effects on the other variables measured. The amount ofextractable P was raised by 16 kg ha¹ in plots given the high P dose (50 kg ha¹), but no other effects of PK fertilization were detected.     

Changes in Soil Iron Fractions and Availability in the Loess Belt of Northern China After 28 Years of Continuous Cultivation and Fertilization

Iron(Fe) deficiency in calcareous soils of the Loess Plateau of China is a wide spread issue and primarily affects agricultural production due to the relatively higher soil pH and carbonate content. Understanding the relationships between Fe distribution in soil fractions, Fe availability, and their responses to cropping and fertilization could provide essential information for assessing Fe availability in soils and managing soils to improve Fe availability. A long-term field experiment was established in 1984 in a split-plot design using cropping systems as main plots and fertilizer treatments as subplots on a farmland in the Loess Plateau. The cropping systems included fallow, continuous wheat cropping, continuous alfalfa cropping, continuous maize cropping, and a rotation system that included a legume. Various fertilization treatments using chemical and/or manure fertilizers were included in each cropping system. Soil samples were collected from 0–10 and 20–40 cm depths in 2012. Long-term planting of crops significantly increased the concentrations of available Fe in the soils. The largest increase was observed in the continuous alfalfa cropping system. Long-term cropping significantly increased the concentrations of Fe associated with carbonates and organic matter, but decreased the concentration of Fe associated with minerals in the soils. The effect of fertilization on the distribution of Fe in the soil fractions varied with cropping system and soil depth. The fertilization treatment with manure generally increased the concentrations of Fe associated with the soil fractions.Long-term cropping and fertilization in the highland farmland significantly affected the availability of Fe and the distribution of Fe fractions in the soil.     

Zeitschrift für Pflanzenernährung und Bodenkunde: Schwermetallgehalt von Wurzel und Sproßorganen der Rebe (Vitis vinifera L.) nach Düngung mit Müll-Klärschlammkompost

Heavy metal content of roots and shoots of vines (Vitis vinifera L.) after fertilization with garbage-sewage-sludge-compost The enrichment of Zn, Cu, Pb, Cd, Co, Ni and Cr from garbage-sewage-sludge-compost in vineyard soils, vines and must was studied in field-and pot-experiments. The following results were obtained: 1. In a field experiment, in which garbage-sewage-sludge-compost was applied, a marked soil enrichment of Zn, Cu, Pb, Cd and Cr was found. It was most evident at the 0–20 cm depth but also obvious at the 40–60 cm depth thus indicating downward migration. The soil was not enriched with Co and Ni. The heavy metal content of leaves, berries and must of riesling vines did not increase on the plots treated with garbage-sewage-sludge-compost. 2. In a pot trial, using an acid and an alkaline soil each mixed with garbage-sewage-sludge-compost, it was observed that only the uptake of Zn and Cu increased into the leaves, tendrils and wood of the riesling cuttings. In relation to the content of the substrate, the heavy metals were detected in the roots percentually in the following order: Cu, Cd > Zn > > Pb, Co, Ni, Cr The root contents were mostly substantially higher than those of the shoot. The migration from root to shoot decreased in the following percentual order: Zn > Cu > Cd, Pb 3. The heavy metal content decreased considerably from the roots to the upper plant organs. This was reflected in low concentrations of heavy metals in the vine must.     

Decomposition rates and feeding activities of soil fauna in deciduous forest soils in relation to soil chemical parameters following liming and fertilization

 This study investigated the influence of liming and P/K fertilization on the feeding activities of soil fauna and leaf litter decomposition rates in deciduous forest soils. The parameters examined were correlated to soil chemical characteristics. In 1994, we established a field experiment with six plots in an oak-beech forest and added different amounts of dolomite, partly combined with P/K fertilization. Two years thereafter a bait-lamina test was used to examine the feeding activity of soil fauna and a minicontainer test to study beech-leaf decomposition. In 1996, the feeding activity in the Ah horizon was lower in the plots left untreated in 1994 than in the plots which had been fertilized in 1994. The highest feeding activity was found in the treatment with 6 t dolomite ha^–1 plus P/K. In all plots, the feeding activity decreased with increasing soil depth. The decomposition rates varied from 0.49% to 0.78% week^–1 in the period April–October 1996. In 1996, the plots treated with 6 t dolomite ha^–1 had the highest decomposition rates and differed significantly from those treated with 9 t or 15 t dolomite ha^–1. No significant differences were found between the untreated plots and those treated with 9 t or 15 t dolomite ha^–1. These results were confirmed by those obtained in 1997. The C/N ratio of litter also decreased, mostly in the treatment with 6 t dolomite ha^–1. Feeding activities in the Ah horizon correlated positively with pH and concentrations of mobile Ca, Mg, K, and negatively with concentrations of mobile Al and heavy metals. We concluded that an increased supply of mobile nutrients and a decrease in mobile Al and heavy metals in these forest soils, as well as a balanced ratio between macro- and micronutrients, led to increased biological activity. Received: 26 June 1998     

Nitrogen fertilization and liming increased CO2 and N2O emissions from tropical ferralsols,but not from a vertisol

The application of nitrogen (N) fertilizers and liming (CaCO₃) to improve soil quality and crop productivity are regarded as effective and important agricultural practices. However, they may increase greenhouse gas (GHG) emissions. There is limited information on the GHG emissions of tropical soils, specifically when liming is combined with N fertilization. We therefore conducted a full factorial laboratory incubation experiment to investigate how N fertilizer (0 kg N ha⁻¹, 12.5 kg N ha⁻¹ and 50 kg N ha⁻¹) and liming (target pH = 6.5) affect GHG emissions and soil N availability. We focussed on three common acidic soils (two ferralsols and one vertisol) from Lake Victoria (Kenya). After 8 weeks, the most significant increase in cumulative carbon dioxide (CO₂) and nitrous oxide (N₂O) fluxes compared with the unfertilized control was found for the two ferralsols in the N + lime treatment, with five to six times higher CO₂ fluxes than the control. The δ¹³C signature of soil-emitted CO₂ revealed that for the ferralsols, liming (i.e. the addition of CaCO₃) was the dominant source of CO₂, followed by urea (N fertilization), whereas no significant effect of liming or of N fertilization on CO₂ flux was found for the vertisol. In addition, the N₂O fluxes were most significantly increased by the high N + lime treatment in the two ferralsols, with four times and 13 times greater N₂O flux than that of the control. No treatment effects on N₂O fluxes were observed for the vertisol. Liming in combination with N fertilization significantly increased the final nitrate content by 14.5%–39% compared with N fertilization alone in all treatment combinations and soils. We conclude that consideration should be given to the GHG budgets of agricultural ferralsols since liming is associated with high liming-induced CO₂ and N₂O emissions. Therefore, nature-based and sustainable sources should be explored as an alternative to liming in order to manage the pH and the associated fertility of acidic tropical soils.     

Orthophosphate and organic phosphate in the soil solution of four sandy soils in relation to pH‐evidence for humic‐FE‐(AL‐) phosphate complexes

Abstract

Soil from the Ap‐horizon of four acid sandy soils differing mainly in Corg content was adjusted to pH values between 3 and 7.5 with NaOH and HCl respectively and incubated for two weeks. Afterwards, displaced soil solution was obtained and analyzed.

The concentrations of Fe, Al, and P showed a broad minimum in the pH range from 4 to 6. The concentration of these elements strongly increased with the increase of pH to 7.5. Acidification below pH values of 4 led to a slight increase.

Separation of dissolved organic carbon by ultrafiltration before the photometric orthophosphate determination decreased measured concentrations in comparison to direct determination in two of the four soils. This decrease was more pronounced for soil solutions with higher concentrations of organic carbon. The effect of acid hydrolysis of organic phosphorus during orthophosphate determination can be explained by existence of humic‐Fe‐(Al phosphate complexes in the soil solution. These complexes can account for more than 50% of the total organic P in solution.     

Effects of liming on carbon and nitrogen mineralization in coniferous forests

A temporary decline in tree growth has often been observed after liming in coniferous forests poor in N but seldom in forests rich in N. To test the hypothesis that the decline was caused by decreases in N supply, C and N mineralization were estimated in incubated soil: (1) after liming in the laboratory, and (2) after earlier liming in the field. Liming increased the C mineralization rate in needle litter, nor humus and 0 to 5 cm mineral soil for a period of 40 to 100 days at 15°C. After that period, liming had no effect on the CO₂ evolution rate in materials poor in N (C:N ratios 30 to 62) but increased the CO₂ evolution rate in materials rich in N (C:N ratios 24 to 28). When liming induced nitrification, the CO₂ evolution rate was reduced. Liming resulted in lower net N mineralization rate in needle litter and mor humus. The reduction was more pronounced when NH₄ ⁺ was the only inorganic form than when NO₃ ^? was the predominant form. The reason is probably that chemical fixation of NH₃ and amino compounds increases with increasing pH. Because of the fixation, the incubation technique most likely underestimated the mineralized N available to the roots. Taking this underestimation into consideration, liming initially reduced the N release in the litter layer. In the other soil layers, liming increased the N release in soils rich in N and had only small effects in soils poor in N. For the total N supply to the roots in the litter, humus and 0 to 5 cm mineral soil layers, liming caused a slight reduction in soils poor in N and a slight increase in soils rich in N. Data on tree growth corresponded with these results.The hypotheses that tree growth depressions can be caused by reduced N supply after liming and that tree growth increases can be caused by increased N supply after liming thus seem reasonable.     

Biological P cycling is influenced by the form of P fertilizer in an Oxisol

Phosphate rock (PR) is an alternative fertilizer to increase the P content of P-deficient weathered soils. We evaluated the effects of fertilizer form on indicators of biological cycling of P using an on-farm trial on a Rhodic Kandiudox in western Kenya. Treatment plots were sampled after 13 cropping seasons of P applications as Minjingu phosphate rock (PR) or as triple super phosphate (?TSP) (50 kg P ha^?1 season^?1), as well as a P-unfertilized control (0 kg P ha^?1 season^?1). Soils (0–15 and 15–30 cm) were analyzed for microbial biomass P (P_mic), activities of acid phosphomonoesterase, alkaline phosphomonoesterase, and phosphodiesterase, and sequentially extractable P fractions. P additions as Minjingu PR yielded 299% greater P_mic than TSP at 0–15-cm depth despite similar labile P concentrations in the two P fertilization treatments and stimulated activities of acid phosphomonoesterase (+39%). When added in the soluble form of TSP, a greater percentage of total soil P was present in mineral-bound forms (+33% Fe- and Al-associated P). Higher soil pH under Minjingu PR (pH 5.35) versus TSP (pH 5.02) and the P-unfertilized treatment (pH 4.69) at 0–15-cm depth reflected a liming effect of Minjingu PR. The form of P fertilizer can influence biological P cycling in weathered soils, potentially improving P availability under Minjingu PR relative to TSP via enhanced microbial biomass P and enzymatic drivers of P cycling.     

Umwandlung von Al-Chloriten durch Kalkung

Transformation of Al-Chlorites by liming In a laboratory liming trial the pH values of acid soils (pH variation 3,6–5,4) were increased to pH > 7.2 under nearly natural conditions (pF2). Within 12–26 weeks, Al-release from the interlattice space of the Al-Chlorites was induced. The alteration in clay mineral composition by liming was revealed by a weakly significant decrease in Al-Chlorit contents, a highly significant decrease in Al-Chlorit/Vermiculite mixed layers and by a significant increase in vermiculite contents. These findings were supported by a highly significant increase in the effective K-buffering capacity (BCKe) after liming. There was also a slight increase in potassium fixation and potential CEC, whereas the mobile potassium (ARo) decreased. In the B_t-horizons, which are rich in fine clay with presumably less intercalation of hydroxo-Al-polymers, liming has a much greater effect than in all A-horizons. In some of these horizons with Al-Chlorites of high stability, no mineral transformation could be determined by X-ray.     

长期不同施肥下太湖地区黄泥土肥力的变化

对太湖地区典型水稻土———黄泥土进行了12年的长期定位不同施肥试验,并保持化肥的施用水平与本地区常规施用量相当。对12年来的肥力变化与不同施肥小区的肥力差异的分析研究表明,长期单施化肥下土壤耕层中养分都有所下降,且表层土壤养分的下降量不及亚表层土壤,年际间生产力不稳定。化肥配施有机肥(秸秆还田或猪粪),可长期保持土壤中的养分,稳定提高作物生产力;有机无机配合施肥下12年间全碳和全氮分别增加1.1g/kg和3.0g/kg,而全磷提高了0.3g/kg以上。同时也表明,表层土壤全氮的增加明显地促进了有机碳的固定。     

Einfluß der Kaliumdüngung auf die Verfügbarkeit des Kaliums in K-fixierenden Böden im Verlaufe der Vegetationszeit

Effect of potassium fertilization on K-availability in potassium fixing soils over the vegetative period The effect of potassium fertilization on the K-availability over the course of the vegetative period was tested on nine potassium fixing soils over two years. The availability of potassium fertilized at the beginning of vegetative period falls (on a soil with 50% clay) to half of the original amount within one month. The availability decreases especially during the time without vegetation. Only after fertilization with 1200 kg K₂O/ha are substantial amounts of potassium available for the plants until the end of the vegetative period (determined by electroultrafiltration). An annual application of 300 kg K₂O/ha only slightly increased the CAL-K and exchangeable K in comparison with the unfertilized plots, although the plants showed marked yield responses. A significant improvement in potassium supply was not obtained with less than 600 kg K₂O/ha. The potassium wet fixation values are relatively constant on the plots without or with low K-fertilization: after high potassium application they show considerable fluctuation. The fixation potential is considerably reduced with an annual application of 1800 kg K₂O/ha, but is not completely removed. Potassium can be removed by repeated extraction with a dilute CaCl₂-solution but the rate at which it is released into the soil solution is too slow compared to the needs of rapidly growing crop plants. The rise in the level of available potassium by fertilization is reverse to the clay content. There was considerable variation between the different available potassium forms over the vegetative period on the highly fertilized plots; consequently a soil test made annually can only give a rough idea of the K-level in potassium fixing soils.