Sortenbedingte Unterschiede der N-Effizienz und Beziehung zum Wurzelwachstums von Weizen (Triticum aestivum L.) unter den Bedingungen des Ökologischen Landbaus

N Uptake at EC 32, 62 and 92 was determined in 6 wheat varieties in field trials under conditions of conventional and organic farming over 3 years. Root growth potential was assessed in a separate trial under controlled conditions. Rank of varieties regarding N-uptake was dependent on yield level of the test environments and was mainly due to differences in uptake during grain filling. In one variety high N uptake potential coincided with high root growth in later growth stages

Einfluss des Ertragspotentials des Standorts und des Anbausystems auf den Züchtungserfolg bei Weizen in Deutschland

Baking quality is a major problem of wheat production in organic farming in Germany. The main reason is low protein content, but also different gluten characteristics. The aim of our investigations was to verify, whether selection of varieties with special adaptation to organic farming (or OF systems with particular low input) is advantageous. 66 Genotypes of winter wheat (registered German varieties, breeding lines, older varieties and varieties bred for organic farming) were compared in 5 environments over two years. Yield, protein content and quality parameters were assessed. Aptitude to LI- or HI- conditions was determined using intravarietal linear regression. While selection for special adaptation proved to be superior for yield and protein yield, this could not be confirmed for gluten characteristics

Screening alternativer Leguminosenarten auf ihre Eignung zur Gründüngung und zum Mischanbau im ökologischen Landbau

In diesem, auf zwei Jahre angelegtem Projekt wurden in 3 Feldversuchen 427 Akzessionen von insgesamt 56 Arten einjähriger Leguminosen auf ihre Eignung als Gründüngungspflanze, insbesondere als Bodenbedecker in speziellen Mischanbausystemen, sogenannte Lebendmulch-("Living Mulch") Systeme in Deutschland geprüft. Dabei handelte es sich zum größten Teil um Wildpopulationen und zum geringerem Teil um Zuchtsorten. Die Herkunftsgebiete liegen in erster Linie im Mittelmeerraum, da hier die biologische Diversität am höchsten ist. In Mittel- und Nordeuropa sind geeignete Arten nur sehr selten. Im Vordergrund der Evaluierungen standen neben der Akklimatisierbarkeit morphologische Eigenschaften (Habitus und Dichte ) die Dauer des Entwicklungszyklus, Biomassebildung und N-Aufnahme. Bei einem Teil der Arten lagen noch keine Erfahrungen im Anbau vor. Hier mußten daher außerdem Kriterien der generellen Anbaueignung, insbesondere die Möglichkeit der Produktion ausreichender Mengen von Saatgut erfaßt werden. Durch diese Evaluierung konnte die ursprünglich sehr große Anzahl möglicherweise geeigneter Arten soweit eingeschränkt werden, dass nun eine weitergehende Forschungs- und Züchtungarbeit möglich ist. Gleichzeitig wurden die ursprünglich sehr geringen Saatgutmengen soweit vermehrt, dass von den wichtigsten Arten genügend Saatgut für weitergehende Untersuchungen, bzw. züchterische Bearbeitung zur Verfügung steht

Annual clovers and medics in living mulch systems: Competition and effect on N supply and soil fertility

The potential of a large number of species of self-reseeding annual clovers and medics as continuous ground cover in living mulch systems with cereals in southern Germany and their effect on N supply and soil properties were assessed. Adapted legume species could be identified. The competition of the legumes on rye was limited but not on wheat. Positive effects on N supply and on indicators of soil fertility could be evidence

Evaluating spatial arrangement for durum wheat (Triticum durum Desf.) and subclover (Trifolium subterraneum L.) intercropping systems

Cover crops and mulches can be used for increasing sustainability in winter cereal cropping systems. We performed a 2-year field experiment in Central Italy with the aim of finding a suitable spatial arrangement for durum wheat (Triticum durum Desf.) and subclover (Trifolium subterraneum L.) as a living mulch system in order to provide a high cereal grain yield and a sufficient subclover reseeding following the wheat harvest. Experimental treatments consisted of: (i) five cropping patterns [wheat and subclover mixed in the same row, with rows 15 cm apart (same row); 2 rows of wheat and 1 row of subclover at a distance of 10 cm between rows (narrow rows); 2 rows of wheat and 1 row of subclover with a distance of 10 cm between the wheat rows and 17.5 cm between the wheat and subclover rows (wide rows); durum wheat sole crop and subclover sole crop, both in rows 15 cm apart]; (ii) two nitrogen fertilization levels (0 and 100 kg ha−1 of N); (iii) and two weed management levels (weed-free and weedy). The wheat grain yield was not reduced by the intercropped subclover in narrow rows, while it was around 14% lower in same row and wide rows compared to the one in the pure crop treatment. When intercropped with subclover, wheat was the competitively superior species and its competitive advantage was greater when it was closer to the legume and/or in presence of nitrogen fertilization. A strong negative relationship between wheat aggressivity and subclover seed production was observed. Following the wheat harvest, the legume reseeding was sufficient to regenerate a cover crop in the autumn of the second year regardless the spatial arrangement, even if the density of the subclover seedlings was almost twice in wide rows compared to the one in the same row. Although the intercropped systems were characterized by an increase in plant density compared to the sole crops (100% of wheat + 50% of subclover), the competitive ability of the wheat-subclover system against the weeds was higher than the wheat sole crop only in narrow rows where a significant reduction of both weed density and weed biomass was observed. When the subclover is used as living mulch in durum wheat, a moderate separation between the two species could be a suitable spatial arrangement for obtaining an adequate wheat grain yield, ensuring satisfactory subclover reseeding, controlling the weeds more effectively

Testability transformation - program transformation to improve testability

Testability transformation is a new form of program transformation in which the goal is not to preserve the standard semantics of the program, but to preserve test sets that are adequate with respect to some chosen test adequacy criterion. The goal is to improve the testing process by transforming a program to one that is more amenable to testing while remaining within the same equivalence class of programs defined by the adequacy criterion. The approach to testing and the adequacy criterion are parameters to the overall approach. The transformations required are typically neither more abstract nor are they more concrete than standard “meaning preserving transformations”. This leads to interesting theoretical questions. but also has interesting practical implications. This chapter provides an introduction to testability transformation and a brief survey of existing results

Wheat performance with subclover living mulch in different agro-environmental conditions depends on crop management

Intercropping has been proposed as a useful strategy for reducing external inputs in cereal-based cropping systems, while maintaining adequate crop yield. Intercropping of wheat and subclover, implemented as living mulch, is recommended, but there is limited experimental proof for its suitability in different environments. The main objective of this study was to provide an overview and evaluation of wheat-subclover intercropping under different agro-environmental conditions. Coordinated field experiments were conducted over a two-year period in six sites located in four agro-environmental zones [Atlantic North (Neu-Eichenberg, Germany), Continental (Freising, Germany – Tänikon, Switzerland), Mediterranean North (Viterbo, Italy), Mediterranean South (Sidi Alla Tazi and Sidi El Aidi, Morocco)]. Wheat–subclover intercropping was compared with a pure wheat. Additionally, other treatments adopted in specific sites were: soil tillage (conventional and minimum tillage); fertilization input (high and low level); cropping system (conventional and organic). The measurements recorded were: soil coverage, wheat and subclover phenological stages, wheat grain yield and yield components, subclover and weed biomass. The data of each site were analyzed separately and were also used for a meta-analysis to obtain an overview of how pedo-climatic conditions affect the interactions of subclover living mulch with wheat and weeds. Subclover biomass was the highest at Viterbo (228 g m−2 of DM) proving its adaptability to the climatic conditions of Mediterranean North characterized by mild temperature and abundant rainfall. Wheat-subclover intercropping reduced weed infestation (from 22 to 75% in Mediterranean South and North, respectively). Intercropping also resulted in grain yield losses compared to pure wheat in Mediterranean North and Continental (on average −16 and −14%, respectively), probably because of the competition between the intercropped species. In the agro-environmental zones where subclover growth was limited by cold temperatures (Atlantic North) or dry conditions (Mediterranean South), hardly any grain yield reduction of intercropped wheat was observed. Subclover biomass and wheat grain yield were also negatively correlated and yield reductions were generally due to a reduced number of fertile spikes. The yield gap between intercropped and pure wheat was reduced when: (i) there was a proper spatial arrangement of subclover and wheat; (ii) the amount of added mineral nitrogen fertilizer was reduced, while compost application did not influence the cropping systems. The use of subclover living mulch in wheat appears to be most suitable for low input systems. Future research should focus on the development of appropriate crop management practices for intercropping in order to avoid wheat yield loss