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• High N input reduced fully filled spikelet percentage, fertilized spikelet weight, and grain plumpness. • The spikelets in the bottom part of the panicle were mainly responsible for poor grain filling under high N input. • High N rates at mid-tillering and panicle initiation reduced fertilized spikelet weight in the bottom part of the panicle. • The poor grain filling at high N input was not associated with increased spikelets per panicle. It is generally accepted that poor grain filling of rice plants under high nitrogen (N) input is due to increased competition for assimilates because high N rate usually results in large sink size with more spikelets per panicle. In this study, we examined grain filling parameters of spikelets in different panicle position under various N treatments to determine the effect of N rates on grain filling. A super rice cultivar with large panicle was grown under field conditions in Wuxue County, Hubei Province, central China in 2013 and 2014. Fully filled spikelet percentage measured at the crop level from 12 hills decreased by 10.9% when the total N rate increased from 0 to 250 kg ha−1, whereas spikelets per panicle remained almost constant across the N rates. At the individual panicle level, reduction in grain filling was evidenced by decreased fully filled spikelet percentage, fertilized spikelet weight, and grain plumpness, and increased partially filled spikelet percentage in the bottom part of the panicle as total N rates increased. Reduction in these grain filling parameters under high N input was relatively small in the middle part of the panicle and was not appeared in the top part of the panicle. Furthermore, high N rates at both mid-tillering and panicle initiation reduced fertilized spikelet weight in the bottom part of the panicle without an increase in spikelets per panicle. Our results suggest that the spikelets in the bottom part of the panicle were mainly responsible for poor grain filling under high N input and such high N-induced poor grain filling was not due to increased spikelets per panicle. [ABSTRACT FROM AUTHOR]

Numerous prior studies on improving crop managements in new commercial rice varieties focused on optimizing N rates and its splitting during the rice growth cycle. Studies concerning how multi-split topdressing fertilizer-N can affect rice growth, grain yield, and nitrogen use efficiencies (NUEs) are limited. A field experiment was conducted in an irrigated rice system using hybrid rice variety Yangliangyou-6 during 2012 and 2013 in Wuxue county, Hubei Province, China. Five treatments were investigated, including nitrogen omission plot (N0), and the other four typical crop management patterns in irrigated rice system in southern China: the conventional farmer’s practice (FP), modified farmer’s practices (MFP), super-high-yielding management (to obtain a high yield regardless labour or fertilizer input, SHY), and multi-split topdressing fertilizer-N (MST). Data from the two years revealed that the SHY produced the highest grain yields (10.27 and 9.63 t ha −1 ) in two of the four trials, while the MST achieved the highest grain yields (10.08 and 9.67 t ha −1 ) in the other two trials. The higher grain yields of the SHY and MST were ascribed to the greater N uptake, biomass accumulation, and total spikelet numbers per m 2 compared to the other treatments. The FP showed a lower N uptake, agronomic efficiency (AE), and recovery efficiency (RE) than those of the MFP, SHY, and MST. Compared with the FP, the MFP increased the planting density and delayed partial fertilizer-N at the panicle initiation stage, which resulted in greater N uptake and RE. However, the MST reduced N application but significantly increased N uptake, AE, and RE compared to that observed in the FP and MFP. Overall, these results indicate that the crop management for N application to achieve greater yield and higher NUEs in hybrid rice is primarily associated with fertilizer-N application splits, rather than N rates. Our findings demonstrate that the crop management based on the MST may obtain a higher grain yield and reduced N application comparing to other crop managements, which results in a greatest profit assuming it is adapted by the large-scaled farmers in South China. Therefore, the MST is recommended as one of alternative approaches to synchronously increase the grain yield, NUEs and production profit with a lower N application in the irrigated rice systems in the Yangtze River Basin in China. [ABSTRACT FROM AUTHOR]

The effects of sulfate radical oxidation pretreatment on the disintegration of waste activated sludge were investigated at different dosages of peroxymonosulfate (PMS). Indicators for estimating sludge disintegration were selected by analyzing concentrations of released substances and statistical analysis. Results indicated that COD and total phosphorus (TP) were unsuitable for estimating sludge disintegration by oxidants. Pearson correlation analysis indicated that total nitrogen (TN), total organic carbon (TOC), UV 254 and polysaccharides had strong correlation with each other, thus suitable for sludge disintegration estimation. Chemical analysis and 3D-EEM fluorescence spectra showed that at high dosage, sulfate radical oxidation was effective for sludge disintegration by inducing aromatic and tryptophan protein-like substances degradation. At PMS dosage of 12 mg (g SS) −1 , sludge disintegration degrees in TOC and TN were 24.8% and 29.9%, respectively. [ABSTRACT FROM AUTHOR]