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To investigate the effects of no-tillage and different amounts of stover mulch on soil microbial community composition and their residues, we set up a field experiment of different amounts of stover mulch under no-tillage on the long-term maize conservation tillage station located in the Mollisols area of Northeast China (built in 2007), including without stover mulch (NT0), 1/3 stover mulch (NT1/3), 2/3 stover mulch (NT2/3) and full stover mulch (NT3/3), and the conservation tillage (plowing without stover mulch, CT) as control. We analyzed phos¬pholipid fatty acid amino sugar biomarker and soil physicochemical properties at different soil layers (0-5 cm, 5- 10 cm, 10-20 cm). The results showed that compared to CT, no-tillage without stover mulch (NT0) did not affect soil organic carbon (SOC), total nitrogen (TN), dissolved organic carbon and nitrogen (DOC, DON), water con¬tent, microbial community and their residue. The main effects of no-tillage and stover mulch were found in the top- soil. Specifically, the NT1/3, NT2/3 and NT3/3 significantly increased SOC content by 27. 2%, 34.1% and 35.6%, respectively, phospholipid fatty acid content was significantly increased under NT2/3 and NT3/3 by 39.2% and 65.0%, respectively, and NT3/3 significantly increased the content of microbial residue-amino sugar by 47.2% in the depth of 0-5 cm compared with CT. The variations in soil properties and microbial community induced by no- tillage and different amounts stover mulch decreased with soil depth, with almost no difference in the 5-20 cm soil layer. SOC, TN, DOC, DON, and water content were the main factors influencing the composition of the microbial community and the accumulation of microbial residue. Microbial biomass was positively correlated with microbial residue, particularly fungal residue. In conclusion, all stover mulch treatments promoted SOC accumulation to dif¬ferent degrees. When there is sufficient stover, it is advisable to opt for no-tillage with full stover mulch, as it is most conducive to the increases of soil microbial biomass, microbial residue and SOC. In case when the amount of stover is inadequate, however, no-tillage with 2/3 stover mulch can still improve soil microbial biomass and SOC content. This study would provide practical guidance for stover management in conservation tillage and sustainable agricultural development in the Mollisols area of Northeast China. [ABSTRACT FROM AUTHOR]

Conservation tillage is an important management practice to guarantee soil fertility in degraded Mollisols. It is still unclear, however, whether the improvement and stability of crop yield under conservation tillage can be sustainable with increasing soil fertility and reducing fertilizer-N application. Based on a long-term tillage experi¬ment initiated in Lishu Conservation Tillage Research and Development Station by Chinese Academy of Sciences, we conducted a 15N tracing field micro-plot experiment to investigate the effects of reducing nitrogen application on maize yield and fertilizer-N transformation under long-term conservation tillage agroecosystem. There were four treat¬ments, including conventional ridge tillage (RT), no-tillage with 0% (NT0), 100% (NTS) maize straw mul¬ching, and 20% reduced fertilizer-N plus 100% maize stover mulching (RNTS). The results showed that after a complete cultivation round, the average percentages of fertilizer N recovery in soil residues, crop usage, and gaseous loss were 34%, 50%, and 16%, respectively. Compared with conventional ridge tillage, no-tillage with maize straw mulching (NTS and RNTS) significantly increased the use efficiency of fertilizer N in current season by 10% to 14%. From the perspective of N sourcing analysis, the average percentage of fertilizer N absorbed by crop parts (including seeds, straws, roots, and cobs) to the total N uptake reached nearly 40%, indicating that soil N pool was the main source of N for crop uptakes. In comparison with conventional ridge tillage, conservation tillage significantly increased total N storage in 0-40 cm by reducing soil disturbance and increasing organic inputs, and thus ensured the expansion and efficiency increment of soil N pool in degraded Mollisols. Compared with conven¬tional ridge tillage, NTS and RNTS treatments significantly increased the maize yield from 2016 to 2018. In all, by improving fertilizer nitrogen utilization efficiency and maintaining the continuous supply of soil nitrogen, long-term management of no-tillage with maize straw mulching could achieve a stable and increasing maize yield in three con-secutive growing seasons and simultaneously reduce environmental risks derived by fertilizer-N losses, even under the condition of 20% reduction of fertilizer-N application, and thus actualize the sustainable development of agricul¬ture in Mollisols of Northeast China. [ABSTRACT FROM AUTHOR]

Soil carbohydrates are the important component of soil organic matter, and play an important role in soil aggregation formation. Their hydrolysis methods involve sulfur acid (H2SO4), hydrochloric acid (HCl), and trifluoroacetic acid (TFA) hydrolysis, and their determination methods include colorimetry, gas-liquid chromatography (GLC) , high performance liquid chromatography (HPLC), and high performance anion-exchange chromatography with pulsed amperometric detection (HPAE-PAD). This paper summarized the methods of carbohydrates' hydrolysis, purification and detection, with focus on the derived methods of GLC, and briefly introduced the indication functions of carbohydrates in soil organic matter turnover.

Using encapsulation techniques to coat easily soluble fertilizers is an important way to improve fertilizer use efficiency while reduce environmental hazards. Based on a wide range of literature collection on coated fertilizer research, the theories, processes, and characters of nutrient controlled-release from coated fertilizer were discussed, and the factors affecting nutrient controlled-release and the mathematical simulations on it were reviewed. The main tendencies related to this research in China were also put forward.

In modern study of soil organic matter, many new quantificational indexes and relevant testing methods, e.g., DOC, WSOC, HWC, ROC, MBC, MBN, PMC, PMN, Glu, Gla, Man, Mur, delta 13C, and CPMI, came forth with deepening study. Because they are disorderly and unsystematic, it is necessary to clarify these indexes. This paper summarized their origin, concept, and testing method, which is of significance in the modern study of soil organic matter.

The effects of applying nitrogen fertilizer in ploughed furrow at different stages on dry matter production and yield of rice were studied in a field experiment in 1999. The results showed that applying N fertilizer at booting stage (BS) had better effects on dry weight (2.9 g.hill-1) of leaf, stem and whole plant than at panicle primordia formation stage (PPFS), tillering stage (TS) and regular N fertilization (RF). Meanwhile, the dry weight of leaf and sheath as well as the leaf area index (LAI, 8.9) could be maintained at a high level for a relative long time in BS treatment, compared with PPFS, TS and RF treatments. Similar phenomenon was observed in the growth velocity (0.73 g.d-1.hill-1) of stem and whole plant, and the dry weight (10434 kg.hm-2) of seed. The grain yield of rice followed the sequence of BS > or = PPFS > TS > or = RF. Thus, the optimum stage of applying N fertilizer in ploughed furrow was the booting stage.