Combined application of chemical fertilizer with green manure increased the stabilization of organic carbon in the organo-mineral complexes of paddy soil.

The influence of the combined application of chemical fertilizer with green manure on the stabilization of organic carbon (C) was explored in the organo-mineral complexes of paddy soil. The organo-mineral complexes were isolated from paddy soil treated with no fertilizer, chemical fertilizer alone, and chemical fertilizer combined with increasing amounts of Chinese milk vetch (CMV). The stability (reflected by mineralizable carbon proportion), the content and chemical composition of organic C, the Fe/Al oxides and their associated organic C in the organo-mineral complexes were investigated. The application of chemical fertilizer in combination with CMV significantly improved the stability of organic C in the organo-mineral complexes. The combined application of chemical fertilizer with CMV slightly decreased the proportion of O-alkyl C (easily decomposed) yet somewhat increased the proportions of carbonyl C and aromatic C (difficultly decomposed) and aromaticity index in the organo-mineral complexes. The treatments of chemical fertilizer combined with CMV showed more Fe oxides and Fe/Al-associated organic C and higher proportion of Fe/Al-associated organic C in the total organic C of the organo-mineral complexes. The mineralizable carbon proportion displayed significantly negative correlations with carbonyl C and Fe/Al oxide-associated organic C in the organo-mineral complexes. The Fe/Al oxides were likely to be preferentially bound with the aromatic C and carbonyl C in the organo-mineral complexes. Overall, the combined application of chemical fertilizer with CMV facilitated the association of difficultly decomposed carbon and Fe/Al oxides, which significantly improved the stabilization of organic C in the organo-mineral complexes of paddy soil.

[Comprehensive effects of combined application of organic and inorganic fertilizer on yield, greenhouse gas emissions, and soil nutrient in double-cropping rice systems]. / æœ‰æœºæ— æœºè‚¥é æ–½å¯¹åŒå­£ç¨»è½®ä½œç³»ç»Ÿäº§é‡ã€æ¸©å®¤æ°”ä½“æŽ’æ”¾å’ŒåœŸå£¤å »åˆ†çš„ç»¼åˆæ•ˆåº”.

We carried out a 3-year field experiment with three treatments: 1) no fertilizer application (CK), 2) chemical fertilizer application (F), and 3) combined organic and chemical fertilizer (FM) in which the total nitrogen inputs were equal with F (organic fertilizer applied in the early rice season). We evaluated the variations of crop yield, CH4 and N2O emission, and soil nutrient. The results showed that fertilizer application could increase rice yield in both early and late rice seasons. Compared with F treatment, FM treatment increased rice yield by 5.6% and 7.2% for early and late rice, respectively. The enhancement of yield was positively correlated with years. Compared with F treatment, CH4 emission in early rice season, late rice season and whole year in the field in FM treatment was increased by 8.2%, 4.8% and 6.7%, respectively, while the N2O emission was deceased by 31.4%, 5.0% and 18.8%, respectively. Organic fertilizer application reduced the greenhouse gas intensity (GHGI) by 6.8% and 8.5%, but there was no significant differences in global warming potential (GWP) across treatments in 2018 and 2019. Compared with F treatment, the content of organic matter, total nitrogen, available phosphorus and available potassium were increased by 9.7%, 4.1%, 30.9% and 2.5%, respectively. Overall, our results suggested FM application in early rice season is an effective measure to increase crop yield, improve soil nutrient, and reduce GHGI.

[Current status of fertilizer application and utilization efficiency of winter wheat in Anhui Province, China]. / 安徽省冬小麦施肥现状与肥料利用效率.

Winter wheat is an important crop in Anhui Province. Rational use of fertilizers is crucial for the achievement of successful yield. It is urgently needed to reveal the status of fertilizer application and existing problems in winter wheat planting in Anhui for better fertilization. We conducted a survey on 1591 farmers in the main winter wheat producing areas of Anhui Province. The contents of survey included fertilizer type, fertilizer dosage, fertilization method, planting area and yield level. Based on the survey results, we analyzed the current fertilization status of winter wheat growing areas in Anhui Province. Referred to the average wheat yield and fertilizer usage in Anhui, the relationship between wheat yield and fertilizers, including nitrogen (N), phosphorus (P2O5) and potassium (K2O), was evaluated by Cate-Nelson method (cross-over method) to explore the ways to increase yield and fertilizer utilization efficiency of winter wheat. The results showed that the average yield of winter wheat in Anhui Province was 5185 kg·hm-2, and the average application rates of N, P2O and K2O fertilizers were 206, 80 and 78 kg·hm-2, respectively. Compared with wheat following rice, the N, P2O and K2O fertilization rates of dry stubble wheat was higher by 14, 16 and 3 kg·hm-2, respectively. Overall, the average amount of chemical fertilizer in winter wheat cultivation in Anhui Province was rational, but there were still some problems in fertilization methods, nutrient management and fertilizer types. The results of Cate-Nelson method showed that 23.8%, 21.2% and 25.7% (for N, P2O5 and K2O fertilizers respectively) of winter wheat were below the average level that achieved high yield, reaching highest partial productivity of N, P2O5 and K2O fertilizers. There were 26.3%, 19.3% and 22.5% (for N, P2O5 and K2O fertilizers respectively) of winter wheat were below the average use level which did not achieve high yield. There were 26.2%, 29.6% and 25.0% (for N, P2O5 and K2O fertilizers respectively) of winter wheat realized high yield, but the fertilization rate was high and the partial productivity of N, P2O and K2O fertilizers was relatively low. Our results suggest that the yield and efficiency of winter wheat in Anhui Pro-vince should be improved. The percentage of mechanical fertilization in winter wheat was 62.7% for base fertilizer and 10.0% for topdressing fertilizer, respectively. Though nitrogen fertilizer was applied at different stages, the proportion of base fertilizer that accounted for 69.0% of the total should be decreased appropriately. It's a problem that farmers preferred to use chemical fertilizers but not organic substitution.

Particulate Organic Matter Affects Soil Nitrogen Mineralization under Two Crop Rotation Systems.

Changes in the quantity and/or quality of soil labile organic matter between and after different types of cultivation system could play a dominant role in soil nitrogen (N) mineralization. The quantity and quality of particulate organic matter (POM) and potentially mineralizable-N (PMN) contents were measured in soils from 16 paired rice-rapeseed (RR)/cotton-rapeseed (CR) rotations sites in Hubei province, central China. Then four paired soils encompassing low (10th percentile), intermediate (25th and 75th percentiles), and high (90th percentile) levels of soil PMN were selected to further study the effects of POM on soil N mineralization by quantifying the net N mineralization in original soils and soils from which POM was removed. Both soil POM carbon (POM-C) and N (POM-N) contents were 45.8% and 55.8% higher under the RR rotation compared to the CR rotation, respectively. The PMN contents were highly correlated with the POM contents. The PMN and microbial biomass N (MBN) contents concurrently and significantly decreased when POM was removed. The reduction rate of PMN was positively correlated with changes in MBN after the removal of POM. The reduction rates of PMN and MBN after POM removal are lower under RR rotations (38.0% and 16.3%, respectively) than CR rotations (45.6% and 19.5%, respectively). Furthermore, infrared spectroscopy indicated that compounds with low-bioavailability accumulated (e.g., aromatic recalcitrant materials) in the soil POM fraction under the RR rotation but not under the CR rotation. The results of the present study demonstrated that POM plays a vital role in soil N mineralization under different rotation systems. The discrepancy between POM content and composition resulting from different crop rotation systems caused differences in N mineralization in soils.