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Soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), and total potassium (TK) are important indicators for evaluating soil fertility. Exploring the content and spatial distribution of these indicators is of great significance for optimizing cropland management measures and developing sustainable agriculture. Yunnan Province is one of the most important agricultural regions in southwestern China, characterized by large variations in the topography and an uneven distribution of soil fertility. In this study, the data of 8571 topsoil (0–20 cm) samples selected from Yunnan Province and a portion of related spatial data were used to carry out electronic mapping of the spatial distribution of soil sand content, clay content, silt content, SOC, TN, TP, TK content, and C:N ratio at 1 km resolution using the Random Forest (RF) model. The results indicated that the average measured contents of SOC, TN, TP, TK, and C:N ratio in the topsoil of Yunnan Province were 18.78 ± 0.09 g/kg, 1.78 ± 0.01 g/kg, 0.98 ± 0.01 g/kg, 13.89 ± 0.08 g/kg, and 10.56 ± 0.02, respectively. The spatial analysis showed that higher SOC was mainly distributed in northern and eastern Yunnan, and the spatial distribution pattern of TN and TP was similar to that of SOC. While higher TK was mainly distributed in southwestern Yunnan Province. There was a significant positive correlation between SOC and TN and TP contents with correlation coefficients of 0.889 and 0.463, however, there was a significant negative correlation between SOC and TK content with correlation coefficients of −0.060. It was also indicated that elevation, temperature, precipitation, clay content, sand content, and silt content were the most important factors affecting SOC, TN, TP, and TK content. The present study provided an understanding of soil nutrients characteristics and their affecting factors, which is helpful to optimize agricultural management practices and develop sustainable agriculture according to soil fertility. [ABSTRACT FROM AUTHOR]

Background and aims: Greenhouse vegetable production is commonly associated with substantial nitrous oxide (N2O) emissions, low nitrogen (N)and irrigation water use efficiency (NUE and IWUE) due to excess N input and frequent flooding irrigation, so it is crucial to develop irrigation and fertilization strategies to alleviate N2O emissions while ensuring vegetable productivity. Methods: An experiment spanning three crop rotations of cucumber and celery in a greenhouse was conducted in North China Plain (NCP). It included four treatments, i.e., no N fertilizer (CK), farmers' conventional fertilization (FP), conventional fertilization rate with drip fertigation (FPD), and reduced N fertilizer rate with drip fertigation (RFPD). Results: The mean annual area-scaled, yield-scaled N2O emissions and direct N2O emission factors (EFd) of FP were 36 kg N ha−1, 175 g N t−1 and 1.3%, respectively. FPD significantly reduced N2O emissions by over 25% (both in area- and yield-scaled), enhanced IWUE by 37%, and had no significant negative effects on vegetable yield or NUE. RFPD also significantly mitigated both area- and yield-scaled N2O emissions by about 45%, improved IWUE by 40% and NUE by 25%, while maintaining vegetable yield. Quadratic curves were fitted to the boundary points of ln-transformed N2O emissions against soil temperature and water-filled pore space (WFPS), with the maximum N2O losses occurring at 19.5 ℃ or 68%. N2O emissions responded to IWUE and NUEs following an exponential (R2 = 0.71, P < 0.001) and a linear-plateau model (R2 = 0.67, P < 0.001), respectively. Conclusions: Drip irrigation with reduced N fertilizer rate is a suitable agronomic practice to simultaneously mitigate N2O emissions and improve both IWUE and NUE while maintaining vegetable yield from typical greenhouse cucumber-celery fields in NCP. [ABSTRACT FROM AUTHOR]

In order to establish a classification method for flue-cured tobacco leaves grown in Henan Province and to meet the requirement of "Golden Leaf" brand cigarettes, a quality gradient experiment of typical flue-cured tobacco samples from Xuchang in central Henan and Sanmenxia in west Henan was conducted to screen the key classification indexes of tobacco leaves. The work established an industrial leaf classification system, which was applied and verified. The results showed that: 1)The quality characteristics of tobacco leaves from Xuchang and Sanmenxia differed, and the leaves from different stalk positions presented different quality trends. 2) Oiliness, softness and leaf structure were the common appearance characteristics affecting the sensory quality of flue-cured tobacco in Henan, among which oiliness or softness contributed to 24.4%-61.9% of the variation of total sensory quality score. Color and body were the individual appearance characteristics affecting the sensory quality of the flue-cured tobacco from Xuchang, while that for Sanmenxai leaves was glossiness. 3) The ratio of reducing sugar to total sugar was the key chemical component index affecting the quality characteristics of tobacco leaves from Xuchang and Sanmenxia, which determined 23.9%-68.5% of the variation of oiliness and softness scores of Xuchang leaves, and contributed to 39.1%-50.5% of Sanmenxia leaves together with carbohydrate content. This leaf classification system linked the above appearance indexes of flue-cured tobacco with the scientific classification of different sensory quality. [ABSTRACT FROM AUTHOR]

Quantifying soil organic carbon (SOC) dynamics is critical for monitoring agricultural sustainability and mitigating global climate change. A study was done to investigate the SOC changes between 2003 and 2016 by DeNitrification-DeComposition (DNDC) model in an intensively cultivated region of eastern China, using a detailed high-resolution soil database, which contained 4875 sites (0–20 cm depth) with the sampling density of one sample per km2 in 2003. Results showed the DNDC model had good performance for simulating the SOC dynamics in the study area. Spatial analysis showed that 71% of the study area gained C, whilst 29% maintained their C balance with no C loss in all areas. Results suggested that the current management practice facilitated soil C sequestration in this region although soil type also played an important role. SOC density (SOCD) in lime concretion black soil was significantly higher than those in other soils. The averaged global warming potential ranged from 3865.8 to 7110.8 kg CO2 equivalent ha−1 yr−1 from 2003 to 2016 with CH4 contributing the largest proportion, which might be associated with the high input of fertilizer. Spatially high-resolution estimates of SOC using DNDC can support dual agricultural and carbon management in this region. [ABSTRACT FROM AUTHOR]

In order to clarify the main meteorological risk factors and their spatial and temporal distributions for flue-cured tobacco growing in Guizhou Province, daily average temperature, maximum temperature and rainfall data of 64 counties (districts or cities) in Guizhou Province from 2008 to 2017 were gathered. The main meteorological risk factors of flue-cured tobacco at different growth stages in different counties and districts were evaluated using cluster analysis method to classify the meteorological risk factors. The results showed that the main meteorological risks were low temperature from the shoot restoring stage to the root extending stage (average daily temperature ≤13 c from late-April to mid-May), high temperature at the mature stage (the highest daily temperature ≥35 c from mid-July to late-August), low temperature at the late mature stage (average daily temperature ≤20 C from early-August to early-September) and heavy rain (daily rainfall ≥50 mm). The risk of low temperature from the shoot restoring to the root extending stage as well as the late mature stage mainly occurred in western Guizhou, including Weining and Dafang in Bijie, Shuicheng in Liupanshui, and Pu'an in Qianxinan. Among them, Weining in Bijie had the highest risk of low temperature whose average number of low temperature days in the early period (from late April to mid-May) was 12 days and was as high as 40 days in the latter period (from early August to early September). The risk of high temperature at the mature stage mainly occurred in Tongren and Qiandongnan. Among them, the risk of high temperature for Yanhe in Tongren was the highest. Within the growth stages of flue-cured tobacco, the rainfall was abundant, but the inter-annual differences were large. The rainfall in the southwest and the eastern regions was significantly higher than that in the central region. The central region only experienced drought in a few years with the longest consecutive rain-free period of 10-15 days. Heavy rains occurred in Anshun and its surrounding counties. The annual average number of rainstorm days was about 4 days, and the average annual rainstorm rainfall was greater than 300 mm. Songtao in Tongren faced dual risks of heavy rain and high temperature at the mature stage. [ABSTRACT FROM AUTHOR]