We investigated the Collembola community at an arable field where mineral and organic fertilizers have been applied at low and high rates for 27 years. As food resources for Collembola, the soil ...microbial community was analyzed using phospholipid fatty acids (PLFAs). A special focus was put on AM fungi, which were estimated by the marker 16:1ω5 in PLFA (viable hyphae) and neutral lipid fatty acid (NLFA – storage fat in spores) fractions. Additionally, whole cellular lipids in crop plant tissues and manure were assessed. Greater Collembola species richness occurred in plots where mineral fertilizer was added. In contrast, soil microbial biomass including AM fungal hyphae increased with addition of organic fertilizer, while the amount of AM fungal spores and biomass of saprotrophic fungi were not affected by fertilizer type. The lipid pattern in wheat roots was altered by fertilizer type, application rate and their interaction, indicating different rhizosphere communities. In sum, the availability and composition of food resources for Collembola changed considerably due to farm management practice. The major diet of three dominant Collembola species,
Isotoma viridis,
Willemia anophthalma and
Polyacanthella schäffer was determined by lipid profiling. Multivariate analysis demonstrated species specific lipid patterns, suggesting greater importance of species than management practice on the diet choice. Nevertheless, feeding strategy was affected by fertilizer type and availability of resources, as trophic biomarker fatty acids indicated feeding on wheat roots (and to some extent saprotrophic fungi) with mineral and a shift to soil organic matter (litter, detritus) with organic fertilization. Although AM fungi dominated the soil fungal community, the AMF marker 16:1ω5 was not detected in Collembola lipids, indicating that these were not consumed. The very low amount of saprotrophic fungi in the soil and the fact that Collembola as major fungal grazers did not feed on AM fungi indicates that the fungal energy channel in the investigated arable field is of little importance to the faunal food web.
This study investigates an arable field soil with long-term (27 and 28 years) mineral (NPK) and organic (cattle manure, cattle manure with biodynamic preparations) fertilizer amendments at low, ...medium and high amounts. Arbuscular mycorrhizal (AM) fungi host plant wheat was cultivated in the first vegetation period and non-host amaranth in the second. Phospholipid fatty acids (PLFA) were used to assess soil microbial biomass and community structure. AM fungi were quantified using the marker fatty acid 16:1ω5, with its occurrence in soil PLFAs representing hyphae and in neutral lipid fatty acid (NLFA) spores. Soil microbial biomass was enhanced by the addition of manure and at higher amounts for both fertilizers. AM fungal hyphae and spore biomass responded positively to manure application. The soil microbial community under both crops was dominated by bacteria. The ratio of fungal to bacterial (f/b) PLFAs increased with higher fertilizer amounts but decreased in amaranth plots with the application of manure. Meanwhile the ratio of Gram+/Gram− bacteria indicating environmental conditions (e.g. pH, temperature) was higher in amaranth plots with the addition of manure as compared to wheat plots. Soil PLFA revealed distinct effect of crop type displayed by changes in the occurrence of saturated fatty acids and biomarkers for Gram-negative bacteria and saprotrophic fungi. The latter additionally accounted for the dissimilarity between fertilizer treatments. In sum, the soil PLFA pattern distinctively separated wheat from amaranth plots at 0–5
cm soil depth, indicating a stronger effect of crop rotation and crop identity on soil microorganisms than long-term fertilizer practice.
The main objective of the second Darmstadt trial was to investigate the effects of vegetal fertilizers on soil properties and crop yield in comparison with farmyard manure. The experiment consisted ...of seven treatments: (i) inorganic fertilizers, (ii) vegetal organic fertilizers, (iii) vegetal organic fertilizers equivalent to biodynamic preparations, (iv) cattle farmyard manure, (v) cattle farmyard manure with addition of biodynamic preparations, (vi) high level of cattle farmyard manure, and (vii) high level of cattle farmyard manure with biodynamic preparations. The soil properties analyzed were pH, soil organic C, N, P, and S, soil microbial biomass C, N, and P, basal respiration and fungal ergosterol. The application of vegetal fertilizers had slightly negative effects on soil organic C, no effects on crop yield (potato, winter rye) and microbial biomass, but positive effects on ergosterol in comparison with farmyard manure. The increase in ergosterol was caused by straw return in the vegetal, but also in the inorganic fertilizer treatments. The biodynamic preparations did not affect the contents of soil organic C and total N. The low effectiveness of vegetal fertiliser in maintaining soil organic C levels is of particular importance for organic cropping systems and should be examined further under different site conditions.
In the Darmstadt long-term fertilization trial, the application of composted cattle farmyard manure without (CM) and with (CMBD) biodynamic preparations was compared to mineral fertilization with ...straw return (MIN). The present study was conducted to investigate the effects of spatial variability, especially of soil pH in these three treatments, on soil organic matter and soil microbial biomass (C, N, P, S), activity (basal CO₂ production and O₂ consumption), and fungal colonization (ergosterol). Soil pH was significantly lower in the MIN treatments than in the organic fertilizer treatments. In the MIN treatments, the contents of soil organic C and total N were also significantly lower (13% and 16%, respectively) than those of the organic fertilizer treatments. In addition, the total S content increased significantly in the order MIN < CM < CMBD. The microbial biomass C content was significantly lower (9%) in the MIN treatments than in the organic fertilizer treatments. Microbial biomass N and biomass P followed microbial biomass C, with a mean C/N ratio of 7.9 and a mean C/P ratio of 23. Neither the microbial biomass C to soil organic C ratio, the metabolic quotient qCO₂, nor the respiratory quotient (mol CO₂/mol O₂) revealed any clear differences between the MIN and organic fertilizer treatments. The mean microbial biomass S content was 50% and the mean ergosterol content was 40% higher in the MIN treatments compared to the organic fertilizer treatments. The increased presence of saprotrophic fungi in the MIN treatments was indicated by significantly increased ratios of ergosterol-to-microbial biomass C and the microbial biomass C/S ratio. Our results showed that complex interactions between the effects of fertilizer treatments and natural heterogeneity of soil pH existed for the majority of microbial biomass and activity indices.
► Cattle manure (± biodynamic preparations) was compared with mineral fertilization. ► MicroResp™ was used for community level physiological profiling. ► Discrimination of treatments was mainly ...caused by carbohydrates and amino acids. ► Functional diversity was reduced in the mineral fertilizer treatments.
The effects of cattle without and with biodynamic preparations on functional diversity of the soil microbial community were investigated in comparison with mineral fertilization (+ straw incorporation) at low and high application rates to a sandy soil of the long-term fertilization trial in Darmstadt, Germany. The multi-SIR method was used for investigating the respiratory response to 17 individual substrates in surface arable soils (0–5cm). Multivariate analysis made it possible to significantly separate mineral fertilizer and manure treatments, mainly on the basis of carbohydrates and amino acids. Correlation analysis of the extracted discriminant function showed that the changes in the catabolic profiles of soil microorganisms between the mineral fertilizer and manure treatments were partly caused by differences in soil pH and soil organic C content. The functional diversity of soil microorganisms caused by differences in the community level physiological profile decreased as a result of long-term mineral fertilization with straw incorporation in comparison with farmyard manure application.
•Application of biodynamic preparations did not cause any positive effects.•Farmyard manure increased bacterial PLFA and muramic acid in soil.•Manure increased the contribution of AMF biomarker PLFA ...16:1ω5 to fungal tissue.•Straw incorporation and lower pH increased the ergosterol to microbial biomass C ratio.•Straw incorporation also increased the fungal PLFA 18:2ω6,9 to total PLFA ratio.
Cattle farmyard manure application is an important tool for maintaining soil fertility in organic agriculture, especially in biodynamic systems. The first objective was to investigate whether application of biodynamic preparations (CMBD treatment) causes positive effects additional to those of composted cattle farmyard manure fertilization (CM treatment). The second objective was to investigate the response of microbial cell-wall and cell-membrane biomarkers to the CM and CMBD treatments in comparison with inorganic fertilization plus straw return (MIN treatment). The third objective was to re-assess conversion values from the phospho-lipid fatty acid (PLFA) 16:1ω5 to arbuscular mycorrhizal fungal (AMF) biomass as well as those from ergosterol and the PLFA 18:2ω6,9 to saprotrophic fungal biomass. Application of biodynamic preparations did not cause any positive effects additional to those of composted farmyard manure fertilization. In the CM and CMBD treatments, bacterial PLFA content was 33% higher than in the MIN treatment, whereas bacterial muramic acid (MurN) content was 55% higher. The AMF indicator PLFA 16:1ω5 as well as neutral lipid fatty acid (NLFA) 16:1ω5 were both increased by roughly 80%, as the NLFA/PLFA ratio of 16:1ω5 varied only in a small range around 3.8. This indicates negligible interference from bacteria, suggesting that PLFA 16:1ω5 is a suitable marker for AMF biomass in soil. The indicators for saprotrophic fungi, the ergosterol content and the contribution of 18:2ω6,9 to total PLFA (mol%) were 40 and 60% higher, respectively, in the CM and CMBD than in the MIN treatments. In contrast, fungal GlcN was not affected by the fertilizer treatments. An increased ergosterol/fungal GlcN ratio indicates a shift in fungal community from AMF towards saprotrophic fungi in arable soils.
Long-term organic fertilization may control the accumulation of organic matter in subsoil. The objective of this study was to evaluate the effects of long-term farmyard manure application in ...comparison with mineral fertilization on the accumulation of amino sugars as indices for microbial residues down to 1m depth at a sandy site that exhibits highly heterogeneous pH conditions. In relation to maximum values in topsoil at 90–100cm depth, the SOC content decreased to roughly 24% and the total N content to 16% of the maximum values, leading to an increased soil C/N ratio from 11 to values around 16 in all treatments. The relative contribution of microbial residue C to SOC decreased with depth from 68% at 0–25cm to 24% at 50–100cm. In the subsoil, the stocks of microbial residue C were increased by manure in comparison with mineral fertilization, but not the stocks of SOC. This suggests that manure-induced priming effects increase the microbial turnover at 50–100cm depth. Manure fertilization promoted the formation of bacterial residues in the topsoil at 0–25cm depth, but not in the subsoil. Below the topsoil, the fungal C to bacterial C ratio decreased from 2.6 at 0–25cm depth to 2.1 at 50–100cm depth. Below the topsoil, the ratio of fungal to bacterial residues continuously decreased with depth from 2.7 to 1.7 at 90–100cm depth, without fertilizer effects. Possible reasons for this decrease, such as effects of pH on the subsoil microbial community, a higher sensitivity of fungi to the absence of fresh organic matter or to an unfavourable composition of the subsoil atmosphere, need further investigations.
•Organic fertilization increased stocks of microbial residue C in the subsoil.•A shift in the microbial residual structure occurred with depth.•The contribution of microbial residue C to SOC generally declined with depth.•In contrast, the soil C/N ratio increased with depth.
Type and rate of fertilizers influence the level of soil organic carbon (Corg) and total nitrogen (Nt) markedly, but the effect on partitioning of C and N into different pools is open to question. ...Objectives were to investigate the impact of fertilizer type and rate on labile, intermediate and passive C and N pools in a sandy Cambisol at Darmstadt, Germany, after 27 years of different fertilization treatments. The six treatments were: straw incorporation plus application of mineral fertilizer (MSI) and application of farmyard manure (FYM) each at high (140-150 kg N ha⁻¹ year⁻¹), medium (100 kg N ha⁻¹ year⁻¹) and low (50-60 kg N ha⁻¹ year⁻¹) rates. Soil microbial biomass C (Cmic) and N (Nmic) and C and net N mineralization (266 days incubation at 10°C and 50% waterfilled pore space) were determined. Soils (0-25 cm) of MSI treatments had significantly (p <= 0.05) lower Cmic stocks (308-361 kg ha⁻¹) than soils of FYM treatments (404-520 kg ha⁻¹). Differences in Nmic stocks were less pronounced. After 266 days, mineralized C (1130-1820 kg ha⁻¹) and N (90-125 kg ha⁻¹) had significantly increased with fertilizer rate. The application of an exponential two-pool model showed that very labile pools (turnover times: 17 and 9 days for C and N, respectively) were small (1.3-1.8% of Corg and 0.5-1.0% of Nt) and not influenced by type or rate of fertilizer. Stocks of the modeled labile C and N pools (turnover times: 462 and 153 days for C and N, respectively) were not influenced by the type of fertilizer but depended significantly on the application rate and ranged from 7 to 13% of Corg and from 4 to 5% of Nt. In contrast, the size of the calculated intermediate C pool was greater for the FYM treatments, and depended significantly on the interaction of fertilizer type and rate. The intermediate N pool was unaffected by fertilizer type or rate. Passive C and N pools, as experimentally revealed by oxidation with disodium peroxodisulfate (Na₂S₂O₈), were independent of the treatments. Overall, labile and intermediate pools were affected differently by the fertilizer type and the application rate.
Long-term application effects of cattle farmyard manure (CM) without and with biodynamic preparations (CMBD) on basal respiration, 0.5 M K
2
SO
4
extractable C and the relationships of microbial ...biomass C (MBC) estimates by chloroform fumigation extraction (CFE) and substrate-induced respiration (SIR) were evaluated down to 1 m depth. The contents of total N, K
2
SO
4
extractable C and MBC-CFE declined with depth from 0–25 to 90–100 cm by −82, −47 and 86%, respectively. The contents of these three soil properties were always 17% lower in the mineral fertilization (MIN) treatment than in the CM and CMBD treatments. However, these differences were not always significant. The MBC-SIR/CFE ratio varied around 1 and did not show a significant depth gradient, due to the strong layer-to-layer variation within each treatment, although this ratio was generally 25% lower in the subsoil than in the topsoil. The metabolic quotient
q
CO
2
, i.e. the ratio of basal respiration to MBC, was positively affected by the MBC-SIR/CFE ratio, soil pH and K
2
SO
4
extractable C and negatively by total N. Long-term application of farmyard manure, especially in the CMBD treatment, resulted in a subsoil microbial community with a more efficient use of SOC and glucose.
