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P-recycling from biogas residue may play a future key role for sustainable P supply in organic farming. However, in particular transportation costs of residue need to be reduced e.g. by pretreatment. One approach is carbonization by pyrolysis or hydrothermal carbonization (HTC). In a pot trial with maize on a P-deficient, acidic sandy loam P uptake after application of two chars from pyrolysis (400 and 700 °C) and HTC (6 and 8 h dwell time) all made of the same residue was compared to P uptake after application of the raw residue and water soluble KH2PO4 respectively. P uptake was the same for KH2PO4, raw residue and both HTC treatments, but was significant lower in treatments with pyrolytic chars. Neither dwell time nor temperature had an effect. However, whereas pyrolysis raised P concentration, in HTC chars it was the same as in the raw residue. Also P was extracted from soil of pots without plants at beginning, half and end of the trial using H2O, CAT, CAL and Na-formate respectively. For CAT, CAL and Na-formate significant correlations between P uptake by maize and extractable P at all dates exist, whereas for H2O this was only true for extractable P at the end of the trial.

Generally, purple-flowered peas are considered to be less susceptible to soil-borne diseases and pests than white-flowered peas. Besides, forage peas usually produce more aboveground biomass and less grain yields in comparison to grain peas. Tolerance to soil-borne diseases, above- and belowground biomass and grain yields of two white-flowered (forage and grain pea, respectively) and one purple-flowered (forage pea) pea were examined in a field experiment in Bavaria, Germany. Purple-flowered peas had neither obvious higher tolerance to soil-borne diseases nor more biomass yield compared to white-flowered peas. Furthermore, the grain yields in this experiment were extremely low and there was no significant difference between the two types. A possible cause could be the unsuitable weather conditions, which caused an increased disease pressure and resulted in low grain and biomass yields. Hence, it can be assumed purple-flowered peas are generally not less susceptible to soil-borne pests than white-flowered peas.

One consequence of the BSE-crisis is, that animal residue derived N-fertilisers used in organic horticulture are to be replaced. As an alternative plant derived N-fertilisers have been investigated. In an incubation experiment these fertilisers mineralised 40 to 60 % of the total N applied. Net N-mineralisation in the incubation experiment as well as plant N-utilisation in a pot experiment were closely related to the N-content of the fertilisers. Fertilisers increased the N-uptake of plants in any soil. Neither texture nor the content of Corg explained the observed differences in fertiliser use efficiency .