Heinrich Scherer

The influence of an interrupted K fertilisation on different K fractions of the soil, yield formation and K uptake by different crops was investigated in a long-term field experiment on Luvisol derived from loess. Irrespective of the previous K fertilisation, the interruption of K fertilisation resulted in a sharp decline of CAL extractable K. K concentration in the saturation extract as well as HCl extractable K were reduced while K fixation capacity increased within 10 years after omitting K. Omitting K fertilisation decreased yields of sugar beet and potatoes while cereals were not affected, although K uptake of all crops reacted to the differentiated K supply to a different extent.

It is postulated that stabilized ammonium fertilizers improve fertilizer-N utilization by crops, leading thus to higher yields with the same fertilizer rate, especially on sandy soils. However, it must be taken into consideration that in clayey soil at least a part of the NH<sub>4</sub><sup>+</sup> ions may be fixed by 2:1 clay minerals, thus delaying the effect of the N fertilizer. Because NH<sub>4</sub><sup>+</sup> and K<sup>+</sup> have similar size and valence properties and therefore compete for the same non-exchangeable sites of 2:1 clay minerals, we investigated the influence of time and K<sup>+</sup> application rate on both fixation and release of NH<sub>4</sub><sup>+</sup>. Fixation of NH<sub>4</sub><sup>+</sup> ions was higher when K<sup>+</sup> was applied after NH<sub>4</sub><sup>+</sup>, while the influence of the K...

To estimate the availability of nonexchangeable NHinf4sup+-N for soil microorganisms four incubation experiments were conducted under controlled conditions. The following results were obtained: Incorporating glucose as a source of readily oxidizable organic material favored the release of nonexchangeable NHinf4sup+-N. Mobilization of NHinf4sup+from the interlayers of the clay minerals was decreased by the application of K++, while Ca2+, which is supposed

The influence of flooding and cellulose addition on the fixation of NH4 + in different soil layers of two paddy soils from China (an entisol and an ultisol) was investigated. In both soils the content of total reducing substances (TRS) sharply increased during the first days after flooding and was highest in the anoxic layers. This increase, which was more

Nitrogen uptake from non-exchangeable NH4+ byLolium multiflorum and availability of fertilizer NH4+ and fertilizer NO3- were studied in pot experiments with three different soil types. The luvisol derived from loess released considerable amounts of non-exchangeable NH4+ when cropped. In this soil fertilizer NH4+ was only weakly fixed and was as available to the crop as fertilizer NO3-. The recovery of

... Extremely low availability of nonexchangeable NH,+ is reported for the native fixed NH4+ (Mohammed, 1979) while the availability of the recently fixed NH4+ is higher ... 34, 13-16, 1982Dulal, R. C. (1977): Fixed ammonium and carbon-nitrogen ratios of some Trinidad soils. ...

The objective of the investigation was to examine whether iron chlorosis in grape vine grown on calcareous soils was related to the Fe distribution in the leaf.Leaf samples collected from three different sites showed in most cases higher Fe contents in the chlorotic leaves as compared with healthy leaves. The solubility of leaf Fe in diluted HC1, however, was lower

Benzoxazolinone detoxification is similar in plants grown under sulfur deficiency conditions and in control plants grown with an optimal S supply. However, when S-deficient plants were treated with metolachlor before benzoxazolin-2(3H)-one (BOA) incubation, detoxification was reduced, as indicated by a lower accumulation of the detoxification products BOA-6-O-glucoside and glucoside carbamate and by a loss of BOA-6-OH glucosyltransfease activity. Root colonizing microorganisms and the endophytic fungus Fusarium verticillioides participated in benzoxazolinone detoxification by converting the compound to 2-acetamidophenol (AAP) or O-hydroxyphenyl malonamic acid (OHPMA), a process accompanied by the appearance of phenoxazinone. Maize roots, however, absorbed AAP and OHPMA only in traces. Absorbed traces of OHPMA stimulated maize radicle growth, and traces of AAP stimulated cress. Phenoxazinone inhibited the growth of cress radicles at concentrations higher than 500 microM, whereas maize radicles were hardly affected. F. verticillioides did not convert benzoxazolinone to any known microbial degradation product when the medium of maize seedlings was inoculated with the fungus under sterile condition. Plant-fungus interactions seem to be important in plant survival of allelopathic attacks. This study points to a complicated network of allelopathic interactions that are influenced by biotic and abiotic factors, including herbicides.

The aim of this work was to investigate the effects of long-term application of different organic fertilizers (sewage sludge, farmyard manure, compost) as compared to mineral fertilizer on the structure of the soil organic matter. Capillary electrophoresis was employed for the quantification of monosaccharides and phenolic compounds, whereas NMR and FT-IR were used for the overall characterization of the soils organic matter. Application of farmyard manure results in a higher content of organic matter derived from angiosperms, ...

In pot experiments with two typical paddy soils, we studied the significance of ammonium fixation under waterlogged conditions and the availability of this N fraction for wetland rice. Special attention was given to the influence of redox potential (Eh) on the fixation and release of NH+4, since the Eh has been shown to affect the charge conditions of certain expandable

Experiments were carried out with 10 soils with different clay contents and different clay composition to investigate the dynamics of non-exchangeable NH+4 and 1 M HCl extractable NH+4, respectively, in the vicinity of the roots. The experimental plant was rape (Brassica napus). In addition the influence of plant species on the mobilization of non-exchangeable NH+4 was investigated with ryegrass (Lolium

The effects of long-term application of different organic amendments, as compared to mineral fertilizer, on Zn, Cu and Pb content and leachability in a luvisol derived from loess were assessed. The organic fertilizers, applied since 1962, were compost (COM) - from green organic household waste, sewage sludge (SLU) - from municipal water treatment facilities, farmyard manure (FYM) and the doses applied since 1997 were 90tha(-1), 10tha(-1) and 9tha(-1), once in 3years, respectively. The kinetics of metals extraction with 0.05moldm(-3) EDTA at pH 6.0 has been studied. The two first-order reactions model was fitted to the kinetic data and allowed to distinguish two pools for each metal: a "labile" fraction (Q(1)), quickly extracted with a rate constant k(1), and a "moderately labile" fraction (Q(2)), more slowly extracted, with a rate constant k(2). Simultaneously, the pseudo-total metal contents in the soil samples were determined after digestion with aqua regia (3:1 HCl+HNO(3)). The obtained parameters Q(1), k(1), Q(2), k(2), for the kinetics of extraction of each metal in the three replicates of each fertilization mode, as well as the pseudo-total metal contents, were statistically analysed. COM and SLU application resulted in an increase of the total contents of Pb, Zn and Cu in soil. Further, the percentage of labile Zn and Pb also increased in consequence of the application of those amendments, particularly COM. The increase was more noticeable for Zn. FYM, despite not increasing the total content of Pb, Zn or Cu, did also have an effect on the leachability of Zn and Pb, increasing their labile fraction in soil. These results point to a potential risk of increasing metals mobility in soil, mainly Zn, associated to the use of organic amendments, particularly COM or SLU.

The influence of flooding and cellulose addition on the fixation of NH4 + in different soil layers of two paddy soils from China (an entisol and an ultisol) was investigated. In both soils the content of total reducing substances (TRS) sharply increased during the first days after flooding and was highest in the anoxic layers. This increase, which was more

To estimate the availability of nonexchangeable NHinf4sup+-N for soil microorganisms four incubation experiments were conducted under controlled conditions. The following results were obtained: Incorporating glucose as a source of readily oxidizable organic material favored the release of nonexchangeable NHinf4sup+-N. Mobilization of NHinf4sup+from the interlayers of the clay minerals was decreased by the application of K++, while Ca2+, which is supposed