New winter oilseed rape varieties – seed quality and morphological traits depending on sowing date and rate

Many studies have focused on research about impact of time and density of sowing on the agronomic characteristics of different crops. However, the number of studies investigating such a response on the qualitative composition of different types of winter oilseed rape varieties is still limited. The aim of the research was to determine the effect of sowing date and density on yield, protein and oil content and quality of winter oilseed rape varieties: open-pollinated, a typical hybrid of traditional type of growth and a new semi-dwarf hybrid, which biology and yielding have not been thoroughly established. This experiment was conducted applying four sowing dates (August 14, August 25, September 4, September 15), three winter oilseed rape cultivars (PR45D03 -semi-dwarf hybrid, PR46W31 – hybrid, Californium – open-pollinated) and four sowing rates (30, 40, 50, 60 seeds/m²). Among the compared sowing dates, August 25 proved to be optimal for yielding of the tested winter oilseed rape cultivars. Semi-dwarf variety contained less protein and glucosinolate in seeds, but more oil in comparison to other studied varieties (hybrid and open-pollinated). The yields did not differ significantly within a density of 40, 50, 60 seeds/m², so it is important result, especially for the agricultural practice.     

Effects of ‘on-farm seed priming’ on consecutive daily sowing occasions on the emergence and growth of maize in semi-arid Zimbabwe

On-farm seed priming (seed soaking) has been reported to improve crop establishment, growth and yield. However, the physiological processes leading to these benefits are not well understood. In this paper, we report how priming affected emergence and growth of maize in semi-arid Zimbabwe. In both the 1999/2000 and 2000/2001 growing seasons, primed and non-primed maize was sown on eight consecutive days into an initially moist seedbed, and soil moisture, crop emergence and growth were monitored. Plants that emerged on the same day from primed and non-primed seeds were tagged, so that any effect of priming on crop growth could be tested independently of the effect of priming on timing of emergence. In the 1999/2000 season, priming increased final emergence in all eight sowing occasions, leading to a 14% increase in crop stand. In the 2000/2001 season, priming increased final emergence in six sowing occasions but decreased it in the other two, so that the overall effect of priming was not significant. Priming decreased mean time to 50% emergence by 12 h in the 1999/2000 season and by 24 h in the 2000/2001 season. The differences in the effect of priming between sowing occasions were interpreted in terms of the soil physical conditions. There was little effect of priming on growth, time to flowering and maturity, or yield of plants that had emerged on the same day from primed or non-primed seed. It was concluded that priming benefits result from improved crop stand and from advancement of germination and emergence.     

High perennial ryegrass seeding rates reduce plant size and survival during the first year after sowing: does this have implications for pasture sward persistence?

Failure of perennial ryegrass swards to persist is a key issue on dairy farms in many areas of the world. This study describes an experiment conducted to test the hypothesis that high ryegrass seeding rates (>18 kg seed ha^?1) reduce plant size and physical survival during the first year after sowing, with negative implications for population persistence. Four cultivars representing four functional types of perennial ryegrass were sown at five seeding rates (equivalent to 6, 12, 18, 24 and 30 kg seed ha^?1) with white clover in three dairying regions of New Zealand. Plant establishment rates, size and survival were measured for the first 13 months after sowing. Herbage accumulation, botanical composition and perennial ryegrass tiller density were also monitored. Increasing seeding rate reduced plant survival in the seven weeks after sowing, reflecting likely differences in germination and very early mortality of small seedlings. Thereafter, plant survival was relatively high and consistent across seeding rates at two sites but was consistently greater in the 6 kg ha^?1 treatment compared with the 24 and 30 kg ha^?1 treatments at one site. Higher seeding rates also increased ryegrass tiller density and the contribution of ryegrass towards total herbage biomass but reduced the contribution of white clover. Very few cultivar × seeding rate interactions were detected for any of the measured variables. Many of the seeding rate effects dissipated by the end of the first year after sowing, indicating that high seeding rates did not predispose swards to poor persistence in the longer term, irrespective of ryegrass functional type.