Quantification of loss in oilseed rape yield caused by delayed sowing date in a Mediterranean environment

Abstract

Rapeseed acreage has been increasing fast in the last few decades and cultivated areas have expanded into lower latitudes because of the high value of its seed. This work evaluates the effect of date of sowing and nitrogen (N) fertilization on crop productivity and N use efficiency in a Mediterranean environment. The experiment was arranged in a split-plot design with the dates of sowing as the main-plots and N rates the sub-plots. Rapeseed recovered 128 to 212 kg N hm -2 before top-dress N application in late winter if sown before the last week of September. Seed yield was very dependent on the date of sowing, varying from 3.4 to 6.2 Mg hm -2 on the first sowing date in September to 0.3 to 1.0 Mg hm -2 on the last sowing date in November. The daily loss in seed production was 68.9 kg hm -2 (or 482.3 kg hm -2 per week) or 1.53 % (or 10.7 % per week). N rate significantly increased seed yield within each sowing date but did not allow latesowed plants to regain the productivity levels of those sown earlier. Apparent N recovery and agronomic N efficiency were particularly dependent on the growing conditions associated to different sowing dates. ARTICLE HISTORY

Early sowing increases nitrogen use efficiency of sunflower in wet clay soils

“…The highest total N uptake and N recovery in the earlier sowing possibly related to less losses of N due to favourable soil factors such as higher SWC and lower salinity while delayed sowing was associated with reduced soil water and increase soil salinity. The reduced N recovery and use efficiency in the delayed sowing might be due to the limited availability of N and lowering the potential of N uptake by the crops (Nematpour et al., 2019; Rodrigues et al., 2019). LCCI significantly increased with the increased rate of applied N but with the similar rate of applied N, LCCI was comparatively higher in the earlier sowing and steadily declined with the delayed of sowing which can be attributed to soil water deficit (Figure 3a,b).…”

“…The reduced N recovery and use efficiency in the delayed sowing might be due to the limited availability of N and lowering the potential of N uptake by the crops (Nematpour et al, 2019;Rodrigues et al, 2019). LCCI significantly increased with the increased rate of applied N but with the similar rate of applied N, LCCI was comparatively higher in the earlier sowing and steadily declined with the delayed of sowing which can be attributed to soil water deficit (Figure 3a,b).…”