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An experiment was conducted using steers cannulated at the rumen, duodenum and ileum to study the effects of increasing the levels of barley and fishmeal in straw-based diets. Diets A, B, C and D contained ammonia-treated straw, barley and fishmeal in the ratios, 67:33:0, 66:23:11, 53:47:0 and 52:36:12 (by weight) and were offered in daily amounts of 3·9, 3·9, 4·8 and 4·8 kg dry matter. The effects of barley were attributable to increased intakes of digestible organic matter and consequently to increased flows of microbial matter to the duodenum. There were no modifications in the balance of energy to nitrogen-yielding nutrients available for absorption. Introducing fishmeal into diets improved digestibility of cellulose and xylose by up to 6.7 and 4.7 % respectively, and shifted digestion towards the large intestine. Second, it increased amino acid N supply to the small intestine which averaged 52·2, 63·2, 68·8 and 84·0 g/d with diets A, B, C and D. Some changes were also noted in the balance of amino acids absorbed. Consequently, the contribution of amino acids to metabolizable energy intake increased with the proportion of fishmeal in diets (0·17, 0·20, 0·18 and 0·21 for diets A, B, C and D).Growth rates measured in heifers amounted to 259, 431, 522 and 615 g/d for diets A, B, C and D. They appeared to be related to intestinal amino acid supply.

For centuries, farmers have been observing the relationship between plants and their environment to develop the best means of cultivation and to ensure good production to meet human needs. In the past, most people were more concerned with the surface layer of the soil and they attached little importance to the role of subsoil or subsurface layers in crop or forest production. In recent years, however, with increasing pressure on land resources, we have started to pay more attention to what lies beneath the surface layer and to its effect on plant growth. Subsoil layers are extremely important to crop production, pasture management, forest growth, soil conservation, and the construction of buildings, highways, and airport runways. For agriculture, excessive compaction of subsoil is believed to cause or be related to some reduction in the productivity of many soils because deeper layers have important effects on soil moisture regime and aeration capacity. These subsoil layers may also supply certain plant nutrients. Furthermore, fertility and permeability of the subsoil have a direct influence on erosion hazards when soils are used for crop production (Nowland 1976). Undesirable compaction levels may be due to naturally occurring or genetically derived edaphic conditions (Winters and Simonson 1951) or due to "induced pans" caused by the manipulation of primary soil particles and aggregates by traction and tillage implements, such as the compression of soil by vehicular traffic (Raney et al. 1955). The mechanics of induced pans and their effect on plant response have been well documented, mainly in USA (Gill and Vanden Berg 1968, Rosenberg 1964, Barnes et al. 1971). A recent series of articles (Voorhees 1977, Robertson and Erickson 1978) describes the problem in more popular language. This bulletin deals primarily with soil compaction problems, especially in Eastern Canada. However, where necessary and appropriate, more recent and relevant work from elsewhere is included.

For highly productive regions such as Germany, the increase of wheat grain yields observed throughout the 20th century is largely attributed to the progress in crop breeding and agronomic management. However, several studies indicate a strong variability of the genetic contribution across locations that further varies with experimental design and variety selection. It is therefore still unclear to which extent management conditions have promoted the realization of the breeding progress in Germany over the last 100+ years. We established a side-by-side cultivation experiment over two seasons (2014/2015 and 2015/2016) including 16 winter wheat varieties released in Germany between 1895 and 2007. The varieties were grown using 24 different long-term fertilization treatments established since 1904 (Dikopshof, Germany). Averaged over all cultivars and treatments mean yields of 6.88 t ha−1 and 5.15 t ha−1 were estimated in 2015 and 2016, respectively. A linear mixed effects analysis was performed to study the treatment-specific relation between grain yields and year of variety release. Results indicate a linear increase in grain yields ranging from 0.025 to 0.032 t ha−1 yr−1 (0.304 to 0.387% yr−1) in plots that were treated with combined synthetic-organic fertilizers without signs of a leveling-off. Yields from low or unfertilized plots do not show a significant progress in yield. Responsiveness of mean yields to fertilizer management increases with year of release and indicates small yield penalties under very low nutrient supply. Results highlight the need to consider the importance of long-term soil fertilization management for the realization of genetic gains and the value of long-term fertilization experiments to study interactions between genetic potential and management., Environmental Research Letters, 13 (10), ISSN:1748-9326, ISSN:1748-9318