Rudolf Schulz

Selection of cultivars to reduce the concentration of cadmium and thallium in food and fodder plants

Pot and field experiments were carried out from 1994 to 1997 to investigate Cd and Tl uptake by various genotypes of maize, spring rape and kale on soils contaminated with i) Cd by the addition of river sediments (aqua regia-extractable Cd: 24 mg kg—1 soil) and ii) with Tl by deposits from a cement plant (HNO3-extractable Tl:1.4 mg kg—1 soil). In field experiments on the Cd-contaminated soil, Cd concentrations in shoots and kernels of fifty maize inbred lines differed by a factor of about twenty (from < 1 to 15 mg Cd kg—1 DM in shoots and from 0.02 to 0.5 mg Cd kg—1 DM in kernels). After crossing inbred lines having high and low Cd concentration, Cd concentration of the resulting hybrids decreased, mainly as a result of a higher dry matter production (a dilution effect). In pot and field experiments on the Tl-contaminated soil, the selected cultivars of spring rape showed only small differences in Tl uptake, whereas Tl concentration in shoots of the kale cultivars differed more than twenty-fold (in the pot experiment from < 1 to 24 mg Tl kg—1 DM and in the field experiment from 0.5 to 11.7 mg Tl kg—1 shoot DM). Two groups of cultivars with low and high Tl concentrations could be distinguished. A nutrient solution experiment with radioactively labeled Tl showed that higher Tl concentration of kale in comparison to white cabbage can be attributed mainly to a higher uptake rate in kale (about 30-fold) with subsequent root-to-shoot translocation. The results show that, depending on plant species, selection and growing of cultivars with low heavy metal uptake on contaminated soils can substantially contribute to reduce the concentration of Cd and Tl in food and fodder plants. Einfluss der Sortenwahl auf die Belastung von Nahrungs- und Futterpflanzen mit Cadmium und Thallium Der Einfluss der Sortenwahl auf die Cd-Aufnahme von Mais und die Tl-Aufnahme von Sommerraps und Grunkohl wurde von 1994 bis 1997 in Gefas- und Feldversuchen mit schwermetallbelasteten Boden untersucht. Die Cd-Belastung des einen Bodens (“Cd-Boden„: Konigswasser-extrahierbarer Cd-Gehalt: 24 mg Cd kg—1 Boden) resultierte aus der Aufbringung von Flussedimenten (Neckarbaggerschlamm aus dem Heilbronner Hafenbecken), die Tl-Belastung des anderen Bodens (“Tl-Boden„: HNO3-extrahierbarer Tl-Gehalt: 1,4 mg Tl kg—1 Boden) aus Erzbergbau und Emissionen eines Zementwerkes in Leimen. Bei dem auf dem Cd-belasteten Boden angebauten Mais unterschieden sich die Cd-Gehalte im Spros und in den Kornern von 50 Inzuchtlinien um bis zu einem Faktor von 20 (< 1 to 15 mg Cd kg—1 TS Spros bzw. 0,02—0,5 mg Cd kg—1 TS Korner). Durch Kreuzung ausgewahlter Linien konnte der Cd-Gehalt im Spros der Hybriden vermindert werden, hauptsachlich als Folge der starkeren Trockenmassebildung und der damit verbundenen Verdunnung der Schwermetallgehalte. Sowohl in Feld- als auch in Gefasversuchen mit dem Tl-belasteten Boden zeigten die Sommerrapssorten nur geringe Unterschiede in den Tl-Gehalten, wahrend sich die Tl-Gehalte der Grunkohlsorten um mehr als das Zwanzigfache unterschieden (Gefasversuch: < 1—24 mg Tl kg—1 TS; Feldversuch: 0,5—12 mg Tl kg—1 TS). Hierbei konnten zwei Gruppen von Grunkohlsorten unterschieden werden: eine Gruppe mit sehr geringen Tl-Gehalten und eine Gruppe mit hohen Tl-Gehalten. Vermutlich handelt es sich um eine abstammungsbedingte Differenzierung der Tl-Aufnahmekapazitat. In einem Nahrlosungsversuch mit radioaktiv markiertem Tl zeigte sich, das die im Vergleich zu Weiskohl wesentlich hoheren Tl-Gehalte von Grunkohl hauptsachlich auf eine bis zu 30fach hohere Aufnahmerate zuruckzufuhren ist. Die Ergebnisse zeigen, das sich die Belastung von Nahrungs- und Futterpflanzen mit Schwermetallen bei bestimmten Pflanzenarten durch die Auswahl von Sorten mit geringer Cd- bzw. Tl-Aufnahme erheblich reduzieren last.

Substrate inputs, nutrient flows and nitrogen loss of two centralized biogas plants in southern Germany.

In Germany, centralized biogas digestion plants (BGP) have been recently constructed. BGPs purchase the substrates from surrounding farmers and, in return, farmers receive the effluents. Substrate inputs, nutrient inputs and outputs were studied for two BGPs with effluent liquid–solid separation. Additionally, the path of the nitrogen (N) during manure handling was assessed. Silage maize (65–75% of the dry matter (DM) inputs) and grass (ca. 20% of the DM inputs) were the main inputs in both BGPs. During manure handling, it is estimated that 20–25% of the N in the effluents was lost via gaseous N emissions. From an environmental point of view the two main challenges are to reduce these gaseous N losses, and to provide N via the effluents mainly for spring manure application, and less so for autumn application. In solid effluents, gaseous N losses during storage are the main potential N loss pathway, whereas for liquid effluents gaseous N losses during and after field spreading are of great relevance. Current management indicated that approximately 50% of the N in the effluents was available for spring application and approximately 30% in autumn due to cleanout of stores before winter. Calculations show that the use of substrates with high DM content during autumn and winter would reduce the demand for storage capacity, thus reducing the demand for store’s cleanout in autumn. This leads to effluents with higher nutrient concentration that are very suitable for application to spring sown crops. Furthermore, some substrates like cereal grains and grass lead to effluents higher in N, whereas silage maize and other substrates lead to effluents low in N. An adapted substrate management would allow more N for spring application. The cycles of P and K are closed, enabling a complete replenishment of the P and K outputs.

Speciation analysis of nickel in soil solutions and availability to oat plants

Soil solutions were collected for speciation analysis of nickel from a pot experiment with oats. Oat plants (Avena sativa L.) were grown on 3 soils differing in total amount and origin of nickel (Ni) (Luvisol, LS with 28 mg kg-1; sludge amended Luvisol, LS+SS with 32 mg kg-1; Cambisol, CS with 95 mg kg-1). Results were compared with those for soil solutions obtained from corresponding unplanted pots. Separation methods were used for characterization of size and charge distribution and stability of the Ni species. In addition, short-term experiments were performed on the uptake rates of Ni by oat plants from the different soil solutions as well as from nutrient solutions with increasing concentrations of a synthetic chelator.The Ni concentrations in the soil solutions of unplanted soils increased in the order: LS5000 g mol-1) was the predominant form, whereas in the other soils the low-molecular-size cationic and chelated Ni species (500–1000 g mol-1) dominated in the soil solution. In the short-term uptake studies, the uptake rates of Ni from the solutions decreased in the order: nutrient solution > soil solutions, and in the latter in the order: LS>LS+SS>CS, which was inversely related to the concentrations of dissolved organic carbon in the soil solutions.The results demonstrate that Ni availability to plants is not only affected by total concentration of Ni in the soil solution and the rate of replenishment from the solid phase, but also by Ni species, which can differ considerably between soil types.

Effects of setup of centralized biogas plants on crop acreage and balances of nutrients and soil humus

An increasing number of biogas plants (BGPs) based on digestion of dedicated energy crops have been implemented in Germany. The objectives of this study were to assess the changes in (1) the acreage of different crops (silage maize, cereals, etc.) related to the setup of the BGP, (2) nutrient flows and budgets (N, P, K) due to the implementation of the BGPs, and (3) to assess the effluent N in the overall crop N supply. Data from 14 farmers before the setup of the BGPs were compared with data after implementation. Due to the setup of the BGPs, the acreage of silage maize greatly increased and there were significant negative effects on the weighted soil humus budgets, no effects on the weighted mean N and P budgets, and a negative trend regarding the K budgets. Results concerning the N release from organic manuring to maize crops showed that one third of the farmers considerably over-fertilize maize, indicating an underestimation of short- and long-term N supply of manure N. The implementation of centralized BGPs established very intensive nutrient cycles and, in the long-term higher risks of nutrient losses and environmental pollution are expected. One very effective measure to compensate for negative effects on the soil humus budgets and nitrate leaching is an enlargement of cover cropping, which will also offer economic revenue by providing aboveground biomass for digestion. If the amounts of effluents returned to a single farm or field are not adapted to the nutrient composition of the substrates delivered to the BGP, large nutrient imbalances can result. An effective measure to get a better allocation of the available nutrients is a solid-liquid separation of the effluents, enabling a more targeted allocation of the nutrients.

Short-term Nitrogen Availability from Lupine Seed Meal as an Organic Fertilizer is Affected by Seed Quality at Low Temperatures

ABSTRACT A high and short-term supply of nitrogen (N) is required in organic vegetable production, especially during early spring under temperate conditions. Lupine seed meal, which can be on-farm produced, has the potential to fulfill this requirement if used as an organic fertilizer. However, no detailed information is available regarding seed meal quality effects on N mineralization potential at low temperatures. Lupine seed meals from five blue lupines (Lupinus angustifolius L.), two yellow lupines (Lupinus luteus L.) and two white lupines (Lupinus albus L.) were tested in the incubation experiment at a lower (5°C) and an increased temperature (18°C) to evaluate the effect of seed meal composition on short-term N mineralization. The results showed that 50–70% of organic fertilizer N was released as mineral N after 7 days of incubation at 18°C. At 5°C, the same level of mineral N was detected in soils on day 28. N mineralization was strongly correlated with N content of the seed meal (R2 = 0.85, p ≤ = 0.05) and negatively correlated with cellulose content (R2 = 0.54, p = 0.05) at 5°C. Lignin and polyphenols had no effect on N mineralization due to their low content in lupine seed meal. The results also indicated that soil-borne organic N was mobilized by microorganisms during the biological degradation of the fertilizers, but did not cause corresponding mineral N release from soil-borne organic matter.

Nitrogen turnover of legume seed meals as affected by seed meal texture and quality at different temperatures

The aim was to investigate how legume seed meal texture and corresponding quality affects N turnover at different temperatures. Therefore, the effect of size fractionation ‘fine’ and ‘coarse’ of seed meals of yellow lupin (Lupinus luteus L.), blue lupin (Lupinus angustifolius L.) and faba bean (Vicia faba L.) on net N mineralization and turnover was investigated in an incubation experiment at 5°C, 12°C and 20°C. The differences in N release from the two particle size fractions could not be detected at 12 and 20°C incubation temperature. Moreover, net N mineralization at 5°C was higher during incubation of the coarse particle size fractions than during incubation of the fine fraction. In contrast to the common understanding of temperature dependence of microbial processes, the overall influence of incubation temperature on net N mineralization was less expressed. The formation of microbial biomass was highest at 5°C. The subsequent decrease of soil microbial biomass was only partly reflected by net N mineralization suggesting the formation of microbial residues as a preliminary N sink. The control of the N release from legume seed meals seems to be dominated by the N-immobilizing effects of polyphenols at lower temperatures and of C-rich polymers (hemicelluloses) at higher temperatures.

The effect of bio-compost application on crop yield and nitrogen dynamic in the soil

Since 1997 bio-compost with and without optimised mineral N fertilisation is applied to maize, winter wheat and summer barley (crop rotation) in a randomised field experiment on a Luvisol in south-west Germany. The aim of this experiment is to evaluate the effect of bio-compost application on crop yield and N-net mineralisation in soil. In the bio-compost application treatment (100 kg total N ha−1 a−1, that is about 7.5 t DM) with optimised mineral N fertilisation yield of summer barley (1999) and maize (2000) was higher than in the optimised mineral N treatment without bio-compost application. Similar results were obtained with the higher bio-compost application rate (400 kg total N ha−1 a−1, that is about 30 t DM) without additional mineral N fertilisation. The yield increase can be attributed to an improvement of soil structure in the Luvisol. During the vegetation period of summer barley net-N-mineralisation on the field plots of the bio-compost treatments with additional mineral N fertilisation was lower than in plots without additional mineral N application. The higher Nmin values after harvest (Sept. 1999) in bio-compost treatments with additional mineral N-fertilisation can be partially attributed to the remineralisation of immobilised N at the end of the growth period.

Mineralization of legume seed meals as organic fertilizers affected by their quality at low temperatures

In organic vegetable production, mineral nitrogen (N) availability is one of the main problems at low temperature in early spring. The aim of this study was to investigate the turnover in soil of legume seed meals from faba bean, soyabean and blue lupine as potential organic fertilizers at 5, 12 and 20°C in a 6-week soil incubation experiment. These legume seed meals showed a rapid net mineral N (Nmin) release of >30% of added N after 1 week of incubation and up to 36–44% after 6 weeks at all temperatures. The net Nmin releases were negatively correlated with initial C:N ratios of the amendments at 12 and 20°C but not as clearly at 5°C. For lupine and faba bean, but not for soyabean, the net Nmin releases were strongly correlated with the initial N content of the added seed meals. At 5 and 12°C after 1 week, net Nmin releases were positively correlated with the sum of hemicellulose and cellulose (R2 = 0.92, R2 = 0.96, at 5 and 12°C, respectively). These results indicated that there was an interaction of both quality and temperature affecting legume seed meal fertilizer mineralization. All tested seed meals showed a negative temperature response of soil microbial biomass carbon and nitrogen accumulation during the incubation period. However, 20–40% of the added organic N was decomposed and possibly transferred into microbial residues, showing an important temporary sink of the seed meal fertilizer-derived N, or yet other unidentified temporarily protected N fraction sinks.

Sequential extraction of Cu and Zn from soil amended with bio-compost for 12 years: risk of leaching

A long-term field experiment was set up on a Luvisol with various fertiliser treatments including bio-compost. The effect of compost application on total (aqua regia extractable) Cu and Zn contents in soil layers were investigated. After 12 years compost application, organic fractions considered as bioavailable and less accessible inorganic Cu and Zn fractions had altered compared to the treatments without compost application. In comparison to the topsoil, the subsoil aqua regia extractable Cu and Zn were higher in the mineral fertilisation treatment (topsoil: 18.46 mg Cu kg−1, 62.89 mg Zn kg−1; sub-soil: 19.89 mg Cu kg−1, 66.88 mg Zn kg−1), but lower in the compost treatment (topsoil: 22.58 mg Cu kg−1, 70.80 mg Zn kg−1; subsoil: 21.03 mg Cu kg−1, 68.68 mg Zn kg−1). In compost, Cu was mainly found in less accessible inorganic fractions and a smaller proportion in the organic fraction. In contrast, the organic fraction was most dominant for Zn followed by the less accessible inorganic fractions. Only a non-drastic accumulation of Cu and Zn in soil was detected. Cu and Zn fractionations in composts had the same trend of the corresponding fractions in the soil.

Effect of different cultivation techniques of Brassicaceae on thallium phytoremediation and Tl-binding forms in the soil

A pot experiment was conducted with five continuous cultivations of candytuft (Iberis intermedia Guers) to determine the effect of repeated cultivation of a Brassica-ceae on the uptake of thallium (Tl) and the changes of the Tl binding forms in the soil. In addition, the possible techniques to overcome the yield reduction due to replant disease as a consequence of continuous cultivation of a Brassicaceae were examined. Candytuft was used in the pot experiment with three different treatments: i) continuous cultivation of candytuft with NH4NO3 as N fertilizer ii)intercropping between repeated cultivations of candytuft with NH4NO3 as N fertilizer iii)CaCN2 as N fertilizer or soil sterilisation with CH3Br and NH4NO3 as N fertilizer. The dry matter production of candytuft between the different cultivation periods varied mainly due to the variation in growth conditions in the greenhouse (irradiance, temperature). Yield was slightly increased by intercropping and fallow in comparison to the continuous treatment, but distinctly increased after soil sterilisation with CaCN2 and CH3Br. The uptake of Tl was generally decreased in all treatments with the duration of the experiment. The comparison of the depleted amount of Tl in the different binding forms and the amount of Tl which was taken up by the plants showed, that the total amount of thallium in the soil was depleted up to 35 % after five repeated cultivations.