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Heitkamp F.,University of Kassel | Raupp J.,Institute for Biodynamic Research | Ludwig B.,University of Kassel
Journal of Plant Nutrition and Soil Science | Year: 2011

The application of density fractionation is an established technique, but studies on short-term dynamics of labile soil fractions are scarce. Objectives were (1) to quantify the long-term and short-term dynamics of soil C and N in light fraction (LFOC, LFON, ρ ≤ 2.0 g cm-3) and microbial biomass C (Cmic) in a sandy Cambisol as affected by 28 y of different fertilization and (2) to determine the incorporation of C4-C into these labile fractions during one growing season of amaranth. The treatments were: straw incorporation plus application of mineral fertilizer (MSI) and application of farmyard manure (FYM) each at high (MSIH, FYMH, 140-150kg N ha-1 y-1) and low (MSIL, FYML, 50-60kg N ha-1 y-1) rates at four field replicates. For all three sampling dates in 2008 (March, May, and September), stocks of LFOC, LFON and Cmic decreased in the order FYMH > FYML > MSIH, MSIL. However, statistical significance varied markedly among the sampling dates, e.g., with LFOC being significantly different (p ≤ 0.05) in the order given above (sampling date in March), significantly different depending on the fertilizer type (May), or nonsignificant (September). The high proportion of LFOC on the stocks of soil organic C (45% to 55%) indicated the low capacity of soil-organic-matter stabilization on mineral surfaces in the sandy Cambisol. The incorporation of C4-C in the LFOC during one growing season of amaranth was small in all four treatments with C4-LFOC ranging from 2.1% to 3.0% of total LFOC in March 2009, and apparent turnover times of C3-derived LFOC ranged from 21 to 32 y for the sandy soils studied. Overall, our study indicates that stocks of LFOC and LFON in a sandy arable soil are temporarily too variable to obtain robust significant treatment effects of fertilizer type and rate at common agricultural practices within a season, despite the use of bulked six individual cores per plot, a common number of field replicates of four, and a length of treatments (28 y) in the order of the turnover time (21-32 y) of C3-derived LFOC. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Heitkamp F.,University of Kassel | Heitkamp F.,University of Gottingen | Raupp J.,Institute for Biodynamic Research | Ludwig B.,University of Kassel
Organic Agriculture | Year: 2011

One aim of organic and biodynamic agriculture is to improve soil fertility. Our objectives are to (1) explain previously reported differences in the soil organic matter levels between soils receiving farmyard manure (FYM) with or without biodynamic preparations (BD), (2) quantify the effect of three levels of FYM applications on microbial biomass and soil organic matter (SOM) pools with different stability, and (3) relate SOM pools to crop yields in a long-term experiment on a sandy soil at Darmstadt, Germany. Soils of the BD-FYM treatments had significantly higher Corg contents compared to soils of the FYM treatments. However, soil fractionation indicated that there was a greater storage of Corg in the intermediate and passive pools of the BD-FYM treatments, and the temporal course of Corg contents suggested a slow convergence of Corg stocks between FYM and BD-FYM with time. Thus, the observed differences between BD-FYM and FYM treatments were likely to have existed since the beginning of the experiment. Contents of labile C (70-114 g [kg Corg],-1 turnover time 462 days) and labile N (35-49 g [kg Nt]-1, turnover time of 153 days) were strongly related to the application rate and also to crop yields. Yield of potatoes, winter rye, and clover significantly increased in proportion to the application rate of FYM, while BD had no effect. Overall, the study showed that increasing rates of FYM increased C and N availability independent of the use of BD. Nevertheless, efficiency of C sequestration in a more stable form (intermediate pool) decreased with increasing rate. © 2011 Springer Science & Business Media BV. Source

Geisseler D.,University of Kassel | Linsler D.,University of Kassel | Piegholdt C.,University of Kassel | Andruschkewitsch R.,University of Kassel | And 2 more authors.
Journal of Plant Nutrition and Soil Science | Year: 2011

A major challenge in sustainable crop management is to ensure adequate P supply for crops, while minimizing losses of P that could negatively impact water quality. The objective of the present study was to investigate the effects of long-term applications of different levels of mineral fertilizers and farmyard manure on (1) the availability of P, (2) the relationship between soil C, N, and P, and (3) the distribution of inorganic and organic P in size fractions obtained by wet sieving. Soil samples were taken from the top 20cm of a long-term (29 y) fertilization trial on a sandy Cambisol near Darmstadt, SW Germany. Plant-available P, determined with the CAL method, was little affected by fertilization treatment (p < 0.05) and was low to optimal. The concentration of inorganic and organic P extracted with a NaOH-EDTA solution (P NaOH-EDTA) averaged about 350 mg (kg dry soil) -1, with 42% being in the organic form (P o). Manure application tended to increase soil C, N, and P o concentrations by 8%, 9%, and 5.6%, respectively. Across all treatments, the C N P o ratio was 100 9.5 2 and was not significantly affected by the fertilization treatments. Aggregate formation was weak due to the low clay and organic-matter content of the soil, and the fractions > 53 μm consisted predominantly of sand grains. The different fertilization treatments had little effect on the distribution of size fractions and their C, N, and P contents. In the fractions > 53 μm, P NaOH-EDTA ranged between 200 and 300 mgkg -1, while it reached 1260 mgkg -1 in the fraction < 53 μm. Less than one third of P NaOH-EDTA was present as P o in the fractions > 53 μm, while P o accounted for 70% of P NaOH-EDTA in the smallest fraction (< 53 μm). Therefore, 16% and 28% of P NaOH-EDTA and P o, respectively, were associated with the smallest fraction, even though this fraction accounted for < 5% of the soil mass. Therefore, runoff may cause higher P losses than the soil P content suggests in this sandy soil with a weak aggregate formation. Overall, the results indicate that manure and mineral fertilizer had similar effects on soil P fractions. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Sradnick A.,University of Kassel | Oltmanns M.,Institute for Biodynamic Research | Raupp J.,Agriculture science.org | Joergensen R.G.,University of Kassel
Geoderma | Year: 2014

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 1. m depth at a sandy site that exhibits highly heterogeneous pH conditions. In relation to maximum values in topsoil at 90-100. cm 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 0-25. cm to 24% at 50-100. cm. 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 50-100. cm depth. Manure fertilization promoted the formation of bacterial residues in the topsoil at 0-25. cm depth, but not in the subsoil. Below the topsoil, the fungal C to bacterial C ratio decreased from 2.6 at 0-25. cm depth to 2.1 at 50-100. cm depth. Below the topsoil, the ratio of fungal to bacterial residues continuously decreased with depth from 2.7 to 1.7 at 90-100. cm 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. © 2014 Elsevier B.V. Source

Heinze S.,University of Kassel | Raupp J.,Institute for Biodynamic Research | Joergensen R.G.,University of Kassel
Plant and Soil | Year: 2010

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. © Springer Science + Business Media B.V. 2009. Source

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