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Asian-Australas J Anim Sci. 2017 Apr;30(4):514-522. doi: 10.5713/ajas.16.0520. Epub 2016 Sep 9.

Comparative nitrogen use efficiency of urea and pig slurry for regrowth yield and nutritive value in perennial ryegrass sward.

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Department of Animal Science, Institute of Agricultural Science and Technology, College of Agriculture & Life Science, Chonnam National University, Gwangju 61186, Korea.
National Institute of Animal Science, Rural Development Administration, Wanju 55365, Korea.



The study aimed to assess the N use efficiency (NUE) of pig slurry (in comparison with chemical fertilizer) for each regrowth yield and annual herbage production and their nutritive value.


Consecutive field experiments were separately performed using a single application with a full dose of N (200 kg N/ha) in 2014 and by four split applications in 2015 in different sites. The experiment consisted of three treatments: i) control plots that received no additional N, ii) chemical fertilizer-N as urea, and iii) pig-slurry-N with five replicates.


The effect of N fertilization on herbage yield, N recovery in herbage, residual inorganic N in soil, and crude protein were significantly positive. When comparing the NUE between the two N sources (urea and pig slurry), pig slurry was significantly less effective for the earlier two regrowth periods, as shown by lower regrowth dry matter (DM) yield, N amount recovered in herbage, and inorganic N availability in soil at the 1st and 2nd cut compared to those of urea-applied plots. However, the effect of split application of the two N sources was significantly positive at the last two regrowth periods (at the 3rd and 4th cut). The two N sources and/or split application had little or no influence on neutral detergent fiber (NDF) content, acid detergent fiber (ADF) content, and in vitro DM digestibility, whereas cutting date was a large source of variation for these variables, resulting in a significant increase in in vitro DM digestibility for the last two regrowth periods when an increase in NDF and ADF content occurred. Split application of N reduced the N loss via nitrate leaching by 36% on average for the two N sources compared to a single application.


The pig slurry-N was utilized as efficiently as urea-N for annual herbage yield, with a significant increase in NUE especially for the latter regrowth periods.


Lolium perenne; N Use Efficiency; Nitrate Leaching; Nutritive Value; Pig Slurry; Regrowth

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