Fate of labeled urea-15N as basal and topdressing applications in an irrigated wheat–maize rotation system in North China Plain: I winter wheat

Abstract

A field micro-plot experiment for winter wheat was conducted in an irrigated winter wheat (Triticum aestivum)-summer maize (Zea mays L.) rotation system in Mazhuang, Xinji of Hebei province in the North China Plain, using the 15 N isotope method to determine the effects of N application (rates and timing), and irrigation frequency on urea-15 N fate, residual-N and N recovery efficiency (NRE) of wheat. The experiment was conducted under two irrigation treatments (I2 and I3, representing for two and three irrigations, respectively), at three N rates (150, 210, and 270, kg ha -1 ), divided between two 15 N-labeled applications of basal-15 N (90 kg ha -1 ) and topdress-15 N (60, 120, and 180, kg N ha -1 , respectively). The total N uptake by wheat (ranging from 186 to 238 kg ha -1 ) and the fertilizer-derived N (Ndff, about 34-55%) were measured. The Ndff from labeled basal-15 N and from labeled topdress-15 N were about 15-22% and 16-40%, respectively. The NRE (measured either as recovery in grain or as the total N recovery in the plant) was higher with I3 (39-41 or 47-49%) than with I2 (35-40 or 42-47%), showing maximum NRE in grain of about 40% both at N210 with I2 and at N150 with I3 treatment. The NRE by the first wheat crop (in grain or the total N recovery in plant) was higher with labeled topdress-15 N (39-48 or 45-56%) as compared to that with labeled basal-15 N (30-37 or 36-45%), while the unaccounted N losses were lower with labeled basal-15 N (14-22%) relative to labeled topdress-15 N (14-35%). Higher residual N in soils was found with labeled basal-15 N (41-51%), as compared to labeled topdress-15 N (18-35%). Residual N in the 0-to 150-cm soil depth ranged from 26 to 44% while the unaccounted N losses ranged from 14 to 30%. Recovery of residual N by the 2nd and 3rd crops in the rotation was 5-10% in the maize crop and a further 1.7-3.5% in the subsequent wheat crop. The accumulated N recovery and the unaccounted N losses in continuous wheat-maize-wheat rotations derived from labeled topdress-15 N were 54-64% and 16-37%, respectively while they were 47-53% and 16-28%, respectively from labeled basal-15 N. This study also suggested that an N rate of 210 kg ha -1

Dynamics of Fertilizer Nitrogen Applied to Sweet Sorghum (<i>Sorghum bicolor</i> (L.) Moench) in the Semi-Arid Tropics

“…3). In particular, 68% of basal applied N remained in the soil and this ratio exceeded that for topdressing of N. This result is well supported by Jia et al (2011), who reported that 37-51% of the basal applied N remained in the soil on harvest and the ratio exceeded that from topdressed N. Stevens et al (2005) reported that 20-55% of inorganic 15 N was converted into an immovable form, including organic and clay-fixed forms, during the maize growing season. Sugihara et al (2010) studied the effect of rainfall after the dry period on microbial biomass and N dynamics and revealed increasing microbial biomass and a drastic decline in inorganic N after rewetting by rainfall, which occurred within 50 hours of rainfall.…”

“…NREisotopic was reportedly higher in topdress-15 N than in basal-15 N for wheat (Triticum aestivum L.) (Jia et al 2011) and maize (Zea mays L.) (Yang et al 2011). In the present study, NREisotopic was markedly lower in basal N application than in topdressings (Fig.…”

“…These results match those of Adu-Gyamfi et al (1997) who reported a relatively lower effect of the applied N through basal application than by topdressing on sorghum yield. Jia et al (2011) and Yang et al (2011) reported that the distribution ratio of 15 N to grain was higher in topdressing than in basal applications for wheat and maize, respectively. Our study also found that the distribution ratio of absorbed 15 N to grain was higher in N than N applied at the other timings (Fig.…”

Fate of residual15N-labeled fertilizer in dryland farming systems on soils of contrasting fertility

“…Ju et al (2007) found that 29-50% of the applied N remained in soil after the first crop harvest, and less than 7.5% of the applied N was uptaken by the second crop in a winter wheat (Triticum aestivum L.) and summer maize (Zea mays L.) rotation system in North China Plain. Jia et al (2011) observed recovery of residual N by the second and third crops in a winter wheat-summer maize rotation under different N application rates and times, and irrigation frequency of 5-10% and 1.7-3.5%, respectively. Another study reported that crops used on average only 3% of the N surplus within 3 years under slurry and inorganic N fertilizer treatments near Kiel in northwest Germany (Sieling et al 2006).…”

“…Many nitrogen-15 ( that more than one third of the fertilizer N resides in soil after crop harvest (Glendining et al 1997;Macdonald et al 2002;Dang et al 2003;Ju et al 2007;Ju et al 2009;Jia et al 2011;Petersen et al 2012). The N fertilizer application rate in developed countries has decreased in recent years due to awareness of the problems of its over-use, and the implementation of different policies to alleviate the problems (Schröder and Neeteson 2008;Sutton et al 2011); however, due to more concern over food security, N fertilizer application in most developing countries is still increasing, especially in China and India (Pilbeam et al 2002;Chen et al 2011;Fan et al 2012).…”