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.

Fertilizer Nitrogen Efficiency in Durum Wheat under Rainfed Mediterranean Conditions: Effect of Split Application

Abstract: Efficient N fertilizer management is critical for the economic production of wheat and the long-term protection of environmental quality. A 3-yr field experiment on a rainfed Vertisol was designed to study the effects of N fertilizer timing on the efficiency of N in durum wheat (Triticum turgidum L. var. durum Desf.). A single rate of 150 kg N ha -1 was used with different fractions being applied at planting, tillering, and stem elongation. A 15 N experiment was also conducted within the main experiment area, with microplots, to quantify N uptake from fertilizer and soil. Mean wheat recovery of N fertilizer ranged from 12.7% when applied at sowing to 41.6% when applied as a topdressing at the beginning of stem elongation. The mean annual contribution of soil residual N and mineralization was 167 kg N ha -1 , representing a considerable proportion of total wheat N uptake-ranging from 80.4% when N fertilizer was applied in the fall to 56.3% when it was applied at stem elongation. This would account for the poor and inconsistent response of grain yield and N efficiency indices, and for the importance of soil N in Vertisols for predicting wheat N fertilizer requirements, due to the carryover effect. It is recommended that N fertilizer be applied mainly as a topdressing in durum wheat, between tillering and stem elongation, to enhance crop N use efficiency (NUE) and reduce losses through leaching and runoff.

Intercepted Solar Radiation during Seed Filling Determines Sunflower Weight per Seed and Oil Concentration

Abstract: A reduction in intercepted photosynthetically active radiation (PAR) during a short period of seed filling could affect weight per seed and oil concentration in sunflower (Helianthus annuus L.) depending when the reduction occurs. The main objectives of this work were (i) to determine the period of time during which intercepted PAR most influences final weight per seed and oil concentration, and (ii) to establish and validate relationships between intercepted PAR during such a period and oil yield components. Intercepted PAR was modified by shading (0, 50, or 80%) field grown crops during different periods of seed filling. Data from published and unpublished field experiments, in which intercepted PAR per plant was changed during the entire seed filling period by shading, thinning to reduce plant population, or both, were also used. All experiments were performed under adequate water and nutrient conditions. A reduction in intercepted PAR during 7 to 10 d of seed filling affected weight per seed and oil concentration. The developmental interval during which final weight per seed and oil concentration were best accounted for by accumulated intercepted PAR (r 2 > 0.805) began at 250°C d and ended at 450°C days after flowering (DAF). The established relationships were validated with independent data. The relationships obtained in this work help to explain the effects of environment and crop management (sowing date, location, year) on oil yield variation.

Cheatgrass facilitates spillover of a seed bank pathogen onto native grass species

Abstract: Summary 1. Pathogen spillover occurs when disease levels for a given population are driven by transmission from a reservoir species that carries a high pathogen load. Pathogen spillover is widely documented in crop systems, but has been little studied in natural plant communities. 2. The abundant seed production of weedy species may create a scenario where spillover of a generalist seed pathogen onto less abundant seeds of native hosts is possible. The invasive annual weed cheatgrass (Bromus tectorum) is a potential reservoir species for Pyrenophora semeniperda, a multiple-host fungal seed pathogen that naturally occurs in the semi-arid western United States. 3. To investigate potential community-level consequences of spillover by this pathogen in plant communities invaded by cheatgrass, we first used artificial inoculation studies to determine the relative susceptibility of seeds of cheatgrass and five co-occurring native grasses to P. semeniperda. Secondly, we quantified the pathogen reservoir (density of pathogen-killed seeds) in the spring seed bank for cheatgrass monoculture, cheatgrass-invaded native grass, and uninvaded native grass patches. Thirdly, potential pathogen spillover onto co-occurring native grasses was quantified by planting native grass seeds into field-collected seed-zone samples from each vegetation patch type and scoring subsequent seed mortality. 4. All species tested were susceptible to infection by P. semeniperda, but their vulnerability to seed death varied as a function of germination time and degree of susceptibility. 5. Seed bank samples from cheatgrass-dominated patches contained seed densities over four times higher than samples from uninvaded native grass patches, and P. semeniperda-killed seeds were also present at much higher densities, indicating that cheatgrass can function as a reservoir for P. semeniperda. Native seeds planted into seed-zone samples from cheatgrass-dominated patches were more likely to be killed by P. semeniperda than those planted into samples from uninvaded native patches. Seed mortality also varied across years, sites and host species. 6. Synthesis. Pathogen spillover onto native seeds is likely to operate within seed banks of semi-arid communities invaded by cheatgrass, and perhaps other weeds, and may have broad consequences for community structure. Our findings also demonstrate the ecological significance of multiple-host pathosystems that operate at the seed stage.

Nodulation studies on chickpea (Cicer arietinum)

Abstract: Glasshouse and field experiments were conducted with chickpea (Cicer arietinum) rhizobia to determine the inoculation requirements of this highly Rhizobium-specific legume. There did not appear to be any host-strain specificity within the species. There was a strong nodulation response to inoculation with four strains (unaffected by time of sowing) even at a level of inoculant application below normal. In some field experiments, nodulation responses were not reflected in improved foliage dry matter production or seed yield. However, the correlations between degree of nodulation and plant growth and seed yield were significant. There was a distinct advantage in using solid inoculant applied in the row with the seed instead of conventional seed inoculation when fungicide-treated chickpea was being sown. Two strains, CB1189 and CC1192, were considered suitable for inoculants.