Abstract
ObjectiveThe 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.MethodsConsecutive 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.ResultsThe 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.ConclusionThe 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.
Highlights
Manure emission from pig production accounts for 38.2% of the total quantity of manure issued from livestock production (46 million tons per year) in Korea [1]
N recovery in herbage and residual N in soil during four successive regrowth The N input into grassland swards increases the regrowth rate leading to higher herbage yield for a given harvest time by cutting or grazing [13,21] or more rapid attainment of a given regrowth yield [22]
The annual yield response to pig slurry N with a four-cut regime was very similar to that (13.4 kg DM/kg N applied) of cattle slurry in a three-cut regime [13], or less than that (15 kg DM/kg N applied) of the average of different cutting frequency [23]
Summary
Manure emission from pig production accounts for 38.2% of the total quantity of manure issued from livestock production (46 million tons per year) in Korea [1]. Pig slurry is the most important organic manure resource in Korea, estimated to be more than 80% of recycled animal manure [2]. The use of pig slurry as an alternative organic fertilizer is the most viable recycling option because pig farms usually have little or no arable surface for forage production in Korea. N losses after pig slurry application to soil are attributed to ammonia volatilization, nitrate leaching, denitrification, and/or microbial immobilization. At the time of application, pig slurry generally contains a large portion of total N as NH4+, which can be lost through volatilization as the largest pathway of pig slurry N loss [3,4]. Pig slurry NH4+ is rapidly nitrified in soil after www.ajas.info
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