Effects of delay in reapplication of nitrogen fertilizer following cutting silage from a ryegrass sward

Abstract

Plots of a 2-year-old sward of Merlinda perennial ryegrass received a routine dressing of 100 kg N ha^' as compound fertilizer in March 1991, followed by further dressings of 100 kg N ha"' after cuts 1,2 and 3 in a simulated four-cut silage system, either the same day as cutting or with a delay of 3, 7, 10 or 14 d. Partial irrigation ensured that fertilizer could be taken up immediately. Annual total dry matter yield, the dry matter yield for the experimental cuts 2-4 and their apparent response to N showed no effect of delays of O-IO d in reapplication of fertilizer, but a significant {P < 0-01) reduction for 14 d delay. Significantly {P = 0-001) higher apparent recovery of N in the cut herbage was recorded where reapplication of fertilizer had been delayed by 7 or 10 d (93% and 91% respectively) in comparison with either smaller (0 delay, 78%; 3 d delay. 87%) or greater delay (14 d, 86%). It is suggested that lower recoveries at 0 and 3 d result from the sward's reduced NOj uptake following defoliation and that, while in practical situations the conditions may not be as rigorous as those imposed in this experiment, further experiments to determine the fate of N not recovered in the herbage are warranted, so defining management circumstances in which immediate reapplication of N might not be advisable.

Strategic timing of nitrogen fertilization to increase root biomass and nitrogen-use efficiency of Lolium perenne L.

“…In the latter study, irrigation after N application reduced the effect of rainfall events on N availability. The findings of Sheldrick et al (1994) are in agreement with the results of Ourry et al (1989) and Thornton et al (1993), who found that only a small amount of N is taken up from the soil during the first week of regrowth, implying that fertilizer N added within 7 days after harvest is susceptible to loss, reducing N-use efficiency. Without irrigation and with N applied under dry conditions, a rainfall event may kick-start N uptake in all treatments simultaneously, reducing treatment effects of delayed N application on N-use efficiency.…”

“…In contrast to our laboratory experiment and the field experiment by Sheldrick et al (1994), we did not irrigate our field plots after fertilizer application, as this is not common farming practice in the Netherlands. To take potential rainfall effects on N availability into account, daily rainfall data from the nearest weather station (5 to 10 km away) were collected from the Dutch Royal Meteorological Institute (KNMI, Bilthoven, the Netherlands).…”

“…The effect of a 3-day delay was not tested in Wolton's (1973) study, but their conclusion was that N fertilizer most effectively increased herbage yield when applied within 8 days after harvest. In another UK study, carried out at one location during one growing season with 42-day harvest cycles, Sheldrick et al (1994) found that a delay of up to 10 days had no significant (P > 0.05) effect on herbage yield. Nitrogenuse efficiency, however, was significantly higher after a 7-day delay compared to a 0-day, 3-day, or 14-day delay.…”

“…Research by Wolton (1973) on permanent grasslands in the UK showed that herbage yield was highest when N application was delayed for 1 day, as compared to 8 or 15 days. In another UK field study, Sheldrick et al (1994) found that a delay of more than 10 days had a significant (P < 0.01) negative effect on herbage yield. Nitrogenuse efficiency was significantly (P = 0.001) higher after a 7-day delay compared to a delay for 0, 3 or 14 days.…”

“…In practice, it is often recommended (Sheldrick et al 1994) that the time between harvest and fertilizer application should be minimized to immediately boost grass regrowth and maximize utilization of fertilizer N before the next harvest. However, various grass defoliation experiments have shown that during the first days of regrowth, most of the N comes from remobilized organic N (proteins) stored in the stubble and roots, and not from current root uptake of fertilizer N. For example, Ourry et al (1989) and Thornton et al (1993) found that the contribution of remobilized N to total N in new leaves of Lolium perenne L. was 70 % after one week and 40 to 45 % after two weeks of regrowth.…”