Sowing

About: Sowing is a research topic. Over the lifetime, 33888 publications have been published within this topic receiving 273438 citations. The topic is also known as: seeding.

N2 fixation and its value to soil N increase in lupin, field pea and other legumes in south-eastern Australia

Abstract: N2 fixation and its potential contribution to increasing soil total N were estimated in field-grown crops of lupin and pea in 21 trials at 10 locations in New South Wales and Victoria, during 1984 to 1987. Chickpea, faba bean and annual medic were included at some sites. Across experiments there were differences in annual rainfall (267 to 646 mm), soil N (0.02 to 0.20%), soil pH (CaCl2,4.3 to 8.0) and sowing date (24 April to 16 June). Most experiments were conducted on acidic (pH < 4.8) red-earth, the others on grey-cracking clay or sandy soil, both of higher pH The differing sites, seasons, and sowing time contributed to variation in legume biomass (2.02 to 14.33 t/ha) and total N (45 to 297 kg N/ha), and the amount of N harvested with grain (8 to 153 kg N/ha), which were related.Lupin fixed an average of 65% of total crop N, and pea 61%, but there was considerable variation about these averages (20 to 97%). Significant differences in % N2 fixation between legumes within sites were few. The amount of N2 fixed averaged 98.5 kg N/ha by lupin and 80.5 kg N/ha by pea, varying 26 to 288 kg N/ha and 16 to 177 kg N/ha, respectively. Variation in proportional and total N2 fixation was associated with biomass, soil mineral N, and sowing date. N2 fixation increased with more biomass and declined with higher soil mineral N, and later sowing (lupin). Each additional tonne of dry matter increased fixed N by c. 20 kg N/ha. Differences in amounts of fixed N between legumes within sites were due primarily to biomass differences.N2fixed by lupin contributed an average of 38.2 kg N/ha to soil N, and by pea, 17.9 kg N/ha. The contribution was variable, -41 to 135 kg N/ha (lupin) and -32 to 96 kg N/ha (pea), and correlated with proportional and total N2 fixation. Positive increase to soil total N occurred when lupin fixed at least 50% of its crop N, and pea 65%. This occurred in most crops. Legumes frequently used less of the available soil N than cereals.

The effects of manure, genotype, seed priming, depth and date of sowing on the emergence and early growth of Sorghum bicolor (L.) Moench in semi-arid Botswana

Abstract: Surveys of research reports and farmers' opinions in semi-arid Botswana suggested that poor stand establishment of cereals was common and a major cause of low yields. Of 146 researcher-managed trials conducted since 1979, 40% failed to germinate, emerge or establish properly. Analysis of a subset of 84 trials for which more detailed data were available showed that the most common reason for failure was ‘soil too dry’ at, or just after, sowing. Therefore we tried to improve post-seeding conditions by agronomic means. Sorghum seeds were sown on nine planting opportunities during the 1990–1991 wet season, all after substantial rainstorms. Adding manure did not affect seedling emergence but enhanced growth over the first 25 days after sowing (DAS) when the soil did not dry out rapidly. Two varieties (Segaolane and 65D) differed significantly and consistently throughout the experiment, with Segaolane emerging more quickly and growing more vigorously. The effect of depth of sowing was inconsistent between sowings. Establishment was more successful if rain fell or if the soil dried out slowly after sowing. Consequently, both stand count and dry matter (plot −1 and plant −1 ) at 25 DAS were directly proportional to the rate at which seedlings emerged. Individual plant vigour in relation to rates of emergence was explained in terms of the interaction between sorghum morphology and rapid soil-drying. Successful establishment was achieved when the soil dried slowly or when seeds germinated and emerged quickly. Soaking seed in water immediately prior to sowing (seed-priming), as a way of speeding up germination, was explored in detail in controlled environments. The time taken for seeds to germinate at 30°C decreased as the soaking time increased from 0 to 10–12 h, a treatment in which a 50% saving in time could be achieved. Germination of seeds soaked for 16 h or more was found to continue even after soaking ceased, suggesting that they would be susceptible to damage in the event of any delays in sowing. Emergence from soil at 30°C was significantly hastened by 23% when seeds were pre-soaked for 6 h or longer. The rate of imbibition during soaking was found to be proportional to temperature. The practicality of seed-priming for improving establishment in the field is discussed.

A Comparison of Soil Microbial Community Structure, Protozoa and Nematodes in Field Plots of Conventional and Genetically Modified Maize Expressing the Bacillus thuringiens is CryIAb Toxin

Abstract: Field trials were established at three European sites (Denmark, Eastern France, South-West France) of genetically modified maize (Zea mays L.) expressing the CryIAb Bacillus thuringiensis toxin (Bt), the near-isogenic non-Bt cultivar, another conventional maize cultivar and grass. Soil from Denmark was sampled at sowing (May) and harvest (October) over two years (2002, 2003); from E France at harvest 2002, sowing and harvest 2003; and from SW France at sowing and harvest 2003. Samples were analysed for microbial community structure (2003 samples only) by community-level physiological-profiling (CLPP) and phospholipid fatty acid analysis (PLFA), and protozoa and nematodes in all samples. Individual differences within a site resulted from: greater nematode numbers under grass than maize on three occasions; different nematode populations under the conventional maize cultivars once; and two occasions when there was a reduced protozoan population under Bt maize compared to non-Bt maize. Microbial community structure within the sites only varied with grass compared to maize, with one occurrence of CLPP varying between maize cultivars (Bt versus a conventional cultivar). An overall comparison of Bt versus non-Bt maize across all three sites only revealed differences for nematodes, with a smaller population under the Bt maize. Nematode community structure was different at each site and the Bt effect was not confined to specific nematode taxa. The effect of the Bt maize was small and within the normal variation expected in these agricultural systems.