Abstract. Precision planting has been proven to be an effective method for seeding row crops with uniform seed spacing, which favors crop yields. However, most precision planters were developed for low field operating speeds. In this study, a mechanical seed-metering device was developed with double-setting seed pickers, which allows high-quality planting at high field operating speeds. A discrete element model (DEM) was used to examine the effects of the design parameters on the metering performance, as indicated by the quality index (Iq), miss index (Imiss), and multiples index (Imult). Based on the model results, a seed-metering device was fabricated with the optimal design parameters and tested in laboratory conditions for model validation. Results showed that the critical parameters for the seed picker design were the lengths of the first and second setting plates (L1 and L2, respectively) and the seed cell and seed holder angles (a and ß, respectively). The Iq was generally high and the Imiss and Imult were generally low over the ranges of L1 from 15.5 to 17.5 mm, L2 from 4.6 to 5.5 mm, a from 57.5° to 65.0°, and ß from 50.0° to 70.0°. The most influential factors were ß and L2 and their interactions. The best performance, represented by the highest Iq, occurred at L2 = 5.18 mm and ß = 61.9°, where the Iq was 99.59%. The model results agreed well with the test results, as demonstrated by the low relative error (2.5%). Keywords: DEM, Modeling, Precision metering, Quality index, Seed, Travel speed.

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In this study, the long-term effects of different salinities on the performance, sludge morphology and shifts in microbial communities were studied in a simultaneous anammox and denitrification (SAD) process at a C/N ratio of 0.5. Stable nitrogen removal efficiencies of 86.96 and 84.58% and nitrogen removal rates of 0.95 and 0.93 kg (m 3 d) −1 could be achieved under low (25 mmol l −1 ) and moderate (50 mmol l −1 ) salinity, respectively. However, the performance collapsed when the system was exposed to high salinity (100 mmol l −1 ). The content of extracellular polymeric substances increased as salinity increased, which resulted in larger sizes of granular sludge under low and moderate salinities. Nevertheless, high salinity shock disintegrated granular sludge, thereby decreasing the average granule size. The Illumina-Miseq sequencing results revealed that Candidatus Jettenia was the sole salinity-tolerant AnAOB genus during the entire operation, whereas the main denitrification bacterial genera shifted from Denitrisoma under low salinity to Denitrisoma , Thauera and Ignavibacterium under high salinity. The results of this study provide a comprehensive and practical evaluation of the SAD process for organic nitrogen-rich saline wastewater treatment.

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