Verbleib des 15N nach einmaliger Verabreichung von markiertem Düngerstickstoff im Dauerversuch Ewiger Roggenbau Halle

Fate of ¹⁵N after one single application of labelled N fertilizer in the long-term experiment Eternal Rye Cropping Halle To elucidate the fate of N in the long-term field experiment with continuous rye cropping in Halle, Germany (Haplic Phaeozem derived from sandy loess; mean annual precipitation: 466 mm) micro plots (9 m²) were established within the NPK main plot in 1993 and 1994 and the routine N dose (60 kg N ha^—1 a^—1) was once applied as ¹⁵N labelled fertilizer. In the subsequent four years each micro plot was analyzed for the ¹⁵N withdrawn with grain and straw and that remaining in the soil after harvest. Parallel to this, micro plots on the unfertilized main plot received a single dose of 5 kg ha^—1 of high-label ¹⁵N in order to achieve labelling of the annual N input from the air (˜40 kg ha^—1 a^—1) and to follow its fate. — In the NPK treatment about one third of the labelled fertilizer N applied (= *N) was taken up by the rye in the first year, while nearly half of it remained in the soil (0—100 cm), and 10—15% was not recovered (most likely lost via leaching). During the following three years the amount of *N remaining in the soil decreased from 32.7 kg ha^—1 to 21.5 kg ha^—1. However, less than half of the remobilized *N had been taken up by the crop. On the unfertilized plot the uptake of *N was lower at the end of the experiment compared to the NPK plot, while the loss exceeded the comparative figure correspondingly.     

Untersuchungen zur Charakterisierung des pflanzenverfügbaren Phosphats in Thüringer Carbonatböden

Investigations on the characterization of plant available phosphate in Thuringian calcareous soils Phosphate availability in Thuringian calcareous soils and its characterization by CAL‒, NaHCO₃-, H₂O- and CaCl₂-soil tests was investigated in laboratory and pot experiments. Soil CaCO₃ contents > 10% increase the pH value of CAL solution and thus decrease phosphate extractability. The increase of pH also causes an inadequate assessment of plant available phosphate by H₂O- and CaCl₂-soil tests. The CAL soluble P content of the soil corrected by the pH value of the extraction solution was most suitable for the forecast of P uptake of corn in a pot trial. From both parameters P availability indices for calcareous soils can be calculated which are comparable with those in soils containing < 5% CaCO₃. The equation, which still has to be verified in field experiments, reads as CAL-P_corrected = CAL-P_measured · (1 + 0.83·〈pH-value_{CAL solution} — 4.1〉).     

Comparing forms and solutions of the single root soil water extraction model

Different forms and solutions of the single root model (SRM) arise from: assumed functional relationships between the radius of the SRM soil cylinder and the rooting density (L_r); averaging modes of hydraulic conductivity (K); steady-state or steady-rate flow assumption; and methods of evaluating the root geometry factor (B). SRM forms and solutions, in particular B approximations, were evaluated by analytical comparison and by performance, when incorporated into a water uptake simulation model for oats. The approximation of B as a constant, or as an exponential function of rooting density (B′), had only a small temporary effect on soil water extraction rates and potentials at the soil—root interface. A combination of B′ with exponential rooting profile estimation is proposed as an optimal SRM form for water uptake analysis. It is shown (in appendices) that: (1) assuming SRM steady-state flow to originate on average from the volumetric middle of the SRM soil cylinder is nearly equivalent to the assumption of a steady-rate flow; and (2) utilizing a geometric mean K for the SRM soil cylinder may cause soil water extraction rates to be underestimated.     

Sulphur amino acid content and nutritive value of pea and cauliflower crude protein as influenced by Sulphur deficiency

Cystine concentrations (g/16g N) in plant tissue declined more under S deficiency conditions than methionine. In N-balance trials with rats the negative effect of S deficiency on S amino acid composition of peas and cauliflower resulted in a corresponding decrease of the biological value of the protein.     

Formation of 5-methyl-4-hydroxy-3[2H]-furanone in cytosolic extracts obtained from Zygosaccharomyces rouxii

Formation of the flavor compound and precursor 4-hydroxy-5-methyl-3[2H]-furanone (HMF, norfuraneol) was demonstrated in cytosolic protein extracts obtained from Zygosaccharomyces rouxii after incubation with a number of carbohydrate phosphates. 4-Hydroxy-5-methyl-3[2H]-furanone was produced from d-fructose-1,6-diphosphate, d-fructose-6-phosphate, d-glucose-6-phosphate, 6-phosphogluconate, d-ribose-5-phosphate, and d-ribulose-1,5-diphosphate. Enzyme assays revealed d-fructose-1,6-diphosphatase, phosphohexose isomerase, d-glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase activity in the cytosolic extracts. Model studies showed the spontaneous formation of HMF from d-ribulose-5-phosphate. It is assumed that d-ribulose-5-phosphate is generated in cytosolic extracts by the action of the investigated enzymes from the carbohydrate phosphates and is then chemically transformed to HMF. The hypothesis was proven by the production of HMF in solutions containing commercially available enzymes and [6-(13)C]-d-glucose-6-phosphate.