The relationship between the fate of nitrogen (N) fertilizer and the N application rate in paddy fields in Northeast China is unclear, as is the fate of residual N.  To clarify these issues, paddy field and ¹⁵N microplot experiments were carried out in 2017 and 2018, with N applications at five levels: 0, 75, 105, 135 and 165 kg N ha^–1 (N0, N75, N105, N135 and N165, respectively).  ¹⁵N-labeled urea was applied to the microplots in 2017, and the same amount of unlabeled urea was applied in 2018.  Ammonia (NH₃) volatilization, leaching, surface runoff, rice yield, the N contents and ¹⁵N abundances of both plants and soil were analyzed.  The results indicated a linear platform model for rice yield and the application rate of N fertilizer, and the optimal rate was 135 kg N ha^–1.  N uptake increased with an increasing N rate, and the recovery efficiency of applied N (RE_N) values of the difference subtraction method were 45.23 and 56.98% on average in 2017 and 2018, respectively.  The RE_N was the highest at the N rate of 135 kg ha^–1 in 2017 and it was insignificantly affected by the N application rate in 2018, while the agronomic efficiency of applied N (AE_N) and physiological efficiency of applied N (PE_N) decreased significantly when excessive N was applied.  N loss through NH₃ volatilization, leaching and surface runoff was low in the paddy fields in Northeast China.  NH₃ volatilization accounted for 0.81 and 2.99% of the total N application in 2017 and 2018, respectively.  On average, the leaching and surface runoff rates were 4.45% and less than 1.05%, respectively, but the apparent denitrification loss was approximately 42.63%.  The residual N fertilizer in the soil layer (0–40 cm) was 18.37–31.81 kg N ha^–1 in 2017, and the residual rate was 19.28–24.50%.  Residual ¹⁵N from fertilizer in the soil increased significantly with increasing N fertilizer, which was mainly concentrated in the 0–10 cm soil layer, accounting for 58.45–83.54% of the total residual N, and decreased with increasing depth.  While the ratio of residual N in the 0–10 cm soil layer to that in the 0–40 cm soil layer was decreased with increasing N application.  Furthermore, of the residual N, approximately 5.4% was taken up on average in the following season and 50.2% was lost, but 44.4% remained in the soil.  Hence, the amount of applied N fertilizer should be reduced appropriately due to the high residual N in paddy fields in Northeast China.  The appropriate N fertilizer rate in the northern fields in China was determined to be 105–135 kg N ha^–1 in order to achieve a balance between rice yield and high N fertilizer uptake.

Genotype imputation has become an indispensable part of genomic data analysis.  In recent years, imputation based on a multi-breed reference population has received more attention, but the relevant studies are scarce in pigs.  In this study, we used the Illumina PorcineSNP50 Bead Chip to investigate the variations of imputation accuracy with various influencing factors and compared the imputation performance of four commonly used imputation software programs.  The results indicated that imputation accuracy increased as either the validation population marker density, reference population sample size, or minor allele frequency (MAF) increased.  However, the imputation accuracy would have a certain extent of decrease when the pig reference population was a mixed group of multiple breeds or lines.  Considering both imputation accuracy and running time, Beagle 4.1 and FImpute are excellent choices among the four software packages tested.  This work visually presents the impacts of these influencing factors on imputation and provides a reference for formulating reasonable imputation strategies in actual pig breeding.

Ten populations of Radopholus similis from different ornamental hosts were tested for their parasitism and pathogenicity to water spinach (Ipomoea aquatic), malabar spinach (Basella rubra), and squash (Cucurbita moschata) in pots. The results showed all three plants were new hosts of R. similis. Growth parameters of plants inoculated with nematodes were significantly lower than those of healthy control plants. All R. similis populations were pathogenic to the three plants, but pathogenicity differed among populations from different hosts. The same R. similis populations also showed different pathogenic effects in the three different plants. RadN5 population from Anthurium andraeanum had the highest pathogenicity to the three studied plants. RadN1 from A. andraeanum had the lowest pathogenicity to squash and RadN7 from Chrysalidocarpus lutesens had the lowest pathogenicity to water spinach and malabar spinach. R. similis is usually associated with root tissues, but here we report that it could be found to move and feed in the stem bases of all three studied plants. Sequence and phylogenetic analyses of DNA markers of the 18S rRNA, 28S rRNA, ITS rRNA, and mitochondrial DNA gene sequences of ten R. similis populations revealed significant genetic diversity. RadN5 and RadN6 populations from anthurium showed a close genetic relationship and could be distinguished from other populations by PCR-RFLP. At the same time, RadN5 and RadN6 populations were the most pathogenic to three studied plants. These results confirm the existence of large biological variability and molecular diversity among R. similis populations from the same or different hosts, and these characteristics are related to pathogenic variability.

A plot experiment including four treatments, CK (N 105 kg ha-1 as urea, including a basal N application of 35 kg ha-1 and a topdressing N 70 kg ha-1 at turned green stage) and optimized N management (OPT1, OPT2 and OPT3, applied two-thirds, one-third and two-fifths N at jointing stage, respectively, total N 60 kg ha-1), was conducted to evaluate the effects of nitrogen management on growth and N uptake of winter wheat (Triticum aestivum), Dongnong 1, which is the first highly cold tolerant winter wheat in China. Index of population quality, N uptake and yield were determined. The ear-bearing tiller rate was increased by above 12%, and the leaf area index, biomass and N uptake were significantly decreased (P<0.05) at jointing stage. OPT treatments increased the grain to leaf area ratio at heading stage, the dry matter weight and N uptake after heading by 14.3-27.9%, 11.6-28.7% and 118.1-161.8 %, respectively. The yield of the OPT treatments was increased by 14.2-37.5% compared with CK, and there was a significant difference (P<0.05) between CK and OPT1 treatments. Harvest index and N partial factor productivity (PFP, kg grain yield per kg N applied) was clearly enhanced from 0.4 and 35.6 kg, respectively for CK to an average of 0.48 (P<0.05) and 77.6 kg (P<0.05) in the OPT treatments. These results indicated that the optimized N management increased the harvest index, yield and N use efficiency by decreasing the N application rate and postponing N application time, improved wheat population quality, controlled excessive growth in the vegetative stages and increased dry matter and N accumulation rates after heading.