Jürgen Heß

Residual nitrogen contribution from grain legumes to succeeding wheat and rape and related microbial process

The residual N contribution from faba bean (Vicia faba L.), pea (Pisum sativum L.) and white lupin (Lupinus albus L.) to microbial biomass and subsequent wheat (Triticum aestivum L.) and oilseed rape (Brassica napus L.) was studied in a greenhouse experiment. The grain legumes were 15N labelled in situ with a stem feeding method before incorporated into the soil, which enables the determination of N rhizodeposition. Wheat and rape were subsequently grown on the soil containing the grain legume residues (incl. 15N-labelled rhizodeposits) and were harvested either twice at flowering and at maturity or once at maturity, respectively. The average total N uptake of the subsequent crops was influenced by the legume used as precrop and was determined by the residue N input and the N2-fixation capacity of the legume species. The succeeding crops recovered 8.6–12.1% of the residue N at maturity. Similar patterns were found for the microbial biomass, which recovered 8.2–10.6% of the residue N. Wheat and rape recovered about the same amount of residue N. The absolute contribution of soil derived N to the subsequent crops was similar in all treatments and averaged 149 mg N pot−1 at maturity. At flowering 17–23% of the residue derived N was recovered in the subsequent wheat and in the microbial biomass; 70% of the residue N was recovered in the microbial biomass in the flowering stage and decreased to about 50% at maturity. In contrast, the recovery in wheat and rape constituted only 30% at flowering and increased to 50% at maturity in all treatments, indicating that the residual N uptake by the subsequent wheat was apparently supplied by mobilisation of residue N temporarily immobilised in the microbial biomass.

Suitability of Organic Potatoes for Industrial Processing: Effect of Agronomical Measures on Selected Quality Parameters at Harvest and after Storage

Three factorial field experiments were conducted in two consecutive years (2003 and 2004) on two sites in order to examine the impact of preceding crop, pre-sprouting, N and K fertilization and cultivar on quality attributes of organically grown potatoes destined for processing into French fries or crisps. Tuber dry matter (DM) concentration, glucose and fructose concentrations, as well as the colour of crisps and the quality score of French fries, were assessed at harvest and after a 4-month storage period. Results suggest that tubers from organic potato cropping may be expected to have sufficiently high tuber DM concentrations (>19%) for processing into French fries without impairing the texture of the fries when concentrations exceed 23%. DM concentrations of tubers for crips (cv. Marlen) fell short of the required minimum of 22% when a combined N and K fertilizer was applied. The tuber DM concentration was significantly lower following peas than following a legume-grass/clover ley or cereals (oats or winter wheat), but only in one of two seasons. Pre-sprouting increased tuber DM concentration considerably, especially in the growing season with a high incidence of Phytophthora infestans (+1.2% absolute increase). Tuber DM concentration was significantly higher after storage in two of three experiments (+0.4 and 0.5% absolute increase). Cultivars belonging to the very early and early maturity type showed the largest relative increase in reducing sugars concentrations due to storage, ranging between 300 and 1,100%. The medium-early cv. Agria and medium-late cv. Marena proved to be best suited for processing into French fries under conditions of organic farming, as only minor deviations from the highest quality standards were established at harvest (quality index at 4.3 and 4.1, respectively). A consistently high crisp quality was achieved by the medium-early cv. Marlen, with L-values of 70.8 and 66.7 at harvest and after storage, respectively. Overall, results show that the quality variables were mainly affected by cultivar, season, storage and their interaction. The effect of agronomical measures, such as fertilization, preceding crop and pre-sprouting of seed-tubers, was rather small and their effect on internal tuber quality and quality of fried products may hardly be predictable. The quality standards for tuber raw stock can be accomplished best when adequate cultivars are chosen.

Developing a Documentation System for Evaluating the Societal Impact of Science

The evaluation of research beyond scientific impact is increasingly required, but has not yet been widely applied. One reason is that data necessary for the evaluation of the societal impact of science are often not available in sufficient quantities or suitable form. This paper describes first results from a research project that develops improved documentation to serve evaluation beyond scientific impact. Firstly, we refer to the need to do this, and to the specific challenges for data assessment in this area. Secondly, we describe the concept for documenting achievements of research beyond scientific impact with a research information system that integrates the relevant parts of research proposals and reports. This enables data to be provided without causing additional effort for scientists, and makes them usable for scientists, research funding agencies and research institutions for different purposes, including evaluation. Compatibility of the system with interoperability standards (e.g. CERIF) is also taken into account. The concept is currently being developed and tested from the user perspectives of scientists, research funding agencies and evaluators.

Wirkung von reduzierter Bodenbearbeitung und Gründüngung im Ökologischen Landbau auf den Beikrautbesatz

Reduzierte Bodenbearbeitung und Grundungung haben das Potenzial, Anbausysteme im Okologischen Landbau weiter zu verbessern, wenn sie an die spezifischen Bedingungen des Okologischen Landbaus angepasst werden. Ein Ziel des europaischen Forschungsprojektes „TILMAN ORG“ (www.tilman-org.net) ist es, eine wirksamere Beikrautregulierung bei gleichzeitig erhohter Biodiversitat durch den verbesserten Einsatz von Grundungung innerhalb verschiedener Szenarien reduzierter Bodenbearbeitung zu entwickeln. Die Ergebnisse eines wiederholten einjahrigen Feldversuches auf der Domane Frankenhausen, dem Versuchsgut der Universitat Kassel, hinsichtlich der Wirkung unterschiedlicher legumer und nicht-legumer Grundungungsarten in vier verschiedenen Bodenbearbeitungssystemen auf den Beikrautbesatz stehen dabei im Vordergrund dieses Beitrages. Auf die Zwischenfruchte Sinapis alba, Trifolium resupinatum und Vicia sativa sowie einer Schwarzbrache als Kontrolle folgte die Hauptfrucht Hafer in vier verschiedenen Bodenbearbeitungssystemen: Pflug, Grubber (2012) bzw. Scheibenegge (2013), sowie Mulch- und Direktsaat. Der Deckungsgrad der Beikrauter war 2012 in den Pflugvarianten grundsatzlich niedrig verglichen mit den anderen Bodenbearbeitungsvarianten. 2012 mussten in den Mulch- und Direktsaatvarianten die Haferparzellen nach den Zwischenfruchten S. alba und T. resupinatum sowie nach der Schwarzbrache wegen zu hohen Beikrautdruckes aufgegeben werden. Im Vergleich dazu konnte V. sativa 2012 die Beikrauter wesentlich besser unterdrucken und fuhrte zu mit Pflug- und Grubbervarianten vergleichbaren Ertragen der Hauptfrucht Hafer auf einem Niveau von 55,3 dt ha-1 bis 59,1 dt ha-1. 2013 mussten alle Mulch- und Direktsaatvarianten aufgrund zu hohen Beikrautdruckes aufgegeben werden. Der Beikrautdruck auf den Scheibenegge - Varianten unterschied sich nicht signifikant von dem Beikrautdruck auf den Pflug – Varianten, es fuhrte aber nur die Zwischenfrucht V. sativa zu ahnlich hohen Ertragen in der Hauptfrucht Hafer wie in den Pflug - Varianten (V. sativa x Scheibenegge 56,2 dt ha-1, V. sativa x Pflug 53,9 dt ha-1). Auf den Pflug – Varianten herrschte insgesamt ein geringer Beikrautdruck. Beim Ertrag gab es keine signifikanten Unterschiede hinsichtlich der Grundungung.