Chinese Journal of Agrometeorology

Characteristics Analysis on Carbon Reduction of Crop Production in Henan Province Based on the Statistical Yearbook Data

LI Jie, NIE Hong-min , XU Guo-zhen

2023, 44(09): 759-768. doi:10.3969/j.issn.1000-6362.2023.09.001

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Based on the statistical yearbook data of Henan province from 2000 to 2020, such as production input, cultivated land area, crop sown area and crop yield, the carbon emission at input end of crop production in Henan province was calculated to analyze the characteristics of carbon reduction in crop production, using the emission factor method that relied on five indexes of fertilizer, pesticide, agricultural film, diesel fuel and irrigation, which provide the theoretical basis for achieving green and low-carbon transformation of agricultural production in Henan province. The results show that, except for the irrigation area, the usage of various inputs in crop production in Henan province showed a trend of first increasing and then decreasing from 2000 to 2020. The total carbon emissions from various crop production inputs also showed a trend of first increasing and then decreasing. The highest point was reached in 2015, reaching 8.6732 million tons, and by 2020, the total carbon emissions had decreased by 10.27% compared to that of 2015. In the average carbon emissions over 21 years, fertilizer had the highest emissions, followed by agricultural plastic film, agricultural diesel, pesticides, and agricultural irrigation, accounting for 73.35%, 9.41%, 8.08%, 7.77% and 1.39% respectively. Therefore, fertilizer is the main source of carbon emissions. The carbon emission intensity of crop production inputs in Henan province showed a trend of first increasing and then decreasing from 2009 to 2020. In 2015, it reached the highest value of 1.0670t·ha⁻¹, but by 2020, the carbon emission intensity had decreased by 2.87% compared to that of 2015. The study found that carbon emissions from crop production inputs are significantly affected by policies. As the main source of carbon emissions in crop production, reducing emissions and increasing efficiency is still an important measure, followed by the rational use of agricultural plastic film. Strengthening policy guidance, controlling the use of fertilizers and pesticides, implementing actions to reduce fertilizer and pesticide use while increasing efficiency, promoting the demonstration and popularization of high-quality and efficient green pest control technologies, and regulating the use and recycling of agricultural plastic film are all effective ways to reduce carbon emissions from crop production in Henan province.

Effects of Combined Application of Controlled Release Urea on Spring Maize Production in Mountainous Area of Southern Ningxia

WANG Ke-jie, WANG Le, FENG Peng-bo, LU Yuan-ming, WANG Xiao-ping, LIU Ya-qian, KANG Jian-hong, LIANG Yi

2023, 44(09): 769-781. doi:10.3969/j.issn.1000-6362.2023.09.002

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The experimental purpose is through investigating the effects of combined application of urea on dry matter, nitrogen accumulation, transport and yield of maize, to provide a theoretical basis for mining a reasonable nitrogen fertilizer for high yield of maize. The field experiment was conducted in 2016 and 2018 with a single factor randomized block design. Five treatments were set in the southern mountainous area of Ningxia. CK has no nitrogen application during whole growth season of maize. T1 was applied with 150kg·ha⁻¹ conventional urea base and 75kg·ha⁻¹ conventional urea topdressing in large bell stage. T2 was based on 75kg·ha⁻¹ conventional urea and 75kg·ha⁻¹ controlled-release urea and 75kg·ha⁻¹conventional urea in large bell stage. T3 consists of 75kg·ha⁻¹ conventional urea based and 150kg·ha⁻¹ controlled-release urea based, T4 is a basal application of controlled release urea of 225kg·ha⁻¹. The results showed that the combined application of conventional urea and controlled-release urea could significantly increase the yield compared with CK. Under T3 treatment, the 2-year average yield was higher than that of single application of conventional or controlled-release urea, and reached the maximum in each treatment. Combined application increased the growth rate of leaf area index (LAI) and leaf area index (LAI) in early growth period, but slowed down the decline rate of LAI in late growth period. Compared with CK and T1, controlled release urea treatment significantly increased dry matter accumulation and grain nitrogen accumulation at mature stage. The dry matter transfer before anthesis was low in the treatment with controlled release urea, but it mainly increased the dry matter accumulation after anthesis and the contribution rate of dry matter accumulation after anthesis to the dry matter accumulation of grain, and it increased first and then decreased with the increase of controlled release urea content. Compared with single application of conventional urea, controlled release urea treatment increased nitrogen utilization rate(REN), nitrogen agronomic utilization rate(AEN), nitrogen partial productivity(PFPN) and fertilizer contribution rate(FCR), and T3 had the highest increase. Based on two years experiment results, applying controlled release urea to conventional urea at a ratio of 2:1 may save labor and increase maize yield.

Influence of Climate Change on the Buckwheat Growth Period and Yield in Semi-arid Region of the Loess Plateau

JIA Rui-ling, ZHAO Xiao-qin, LIU Jun-xiu, LIU Yan-ming, ZHANG Ming, FANG Yan-jie, MA Ning

2023, 44(09): 782-794. doi:10.3969/j.issn.1000-6362.2023.09.003

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This study investigated the influence of climate change on the buckwheat growth period and yield in semi-arid regions of the Loess Plateau based on observations buckwheat localization experiments and data of climate factors. The results showed that the temperatures decreased significantly, with a climatic tendency rate of −0.81℃·10y⁻¹(P<0.01), and the precipitation increased significantly, with a climatic tendency rate of 48.55mm·10y⁻¹(P<0.01), while the sunshine duration increased significantly, with a climatic tendency rate of 4.76h·10y⁻¹(P<0.01) in tartary buckwheat whole growth period during 2009−2019. The temperatures decreased significantly, with a climatic tendency rate of −0.82℃·10y⁻¹(P<0.01), and the precipitation increased significantly, with a climatic tendency rate of 33.33mm·10y⁻¹(P<0.01), while the sunshine duration decreased significantly, with a climatic tendency rate of −28.98h·10y⁻¹(P<0.01) in common buckwheat whole growth period. The growth days of common and tartary buckwheat were shortened, with climatic tendency rate of 0.53d·y⁻¹ and 0.84d·y⁻¹ (P<0.01), respectively. The length of vegetative growth period of both common and tartary buckwheat decreased with increasing temperature and sunshine hours, and increased with increasing precipitation. The length of reproductive growth periods increased with the increase of temperature and sunshine hours, and decreased with the increase of precipitation. The tartary buckwheat yieldhas increased. Yield was highly significantly negatively correlated (P<0.01) with both temperature and sunshine hours of tartary buckwheat whole growth period. Yield was significantly positively correlated (P<0.01) with precipitation of tartary buckwheat whole growth period. Temperature was a key factor to affect tartary buckwheat yield. The common buckwheat yield has decreased. Yield was significantly positively correlated (P<0.05) with temperature, precipitation and sunshine hours of common buckwheat whole growth period. Temperature and sunshine hours during the whole growth period were key factors affecting common buckwheat yield.

Evaluation on Cold Resistance of Buckwheat Germplasm during Germination Stage in Sichuan Province

ZHENG Wen, ZHU Ming-kun, FANG Zhong-yan, CHEN Yu-nan, DU Han-mei, WANG An-hu, ZHOU Yong-hong, WU Dan-dan

2023, 44(09): 795-804. doi:10.3969/j.issn.1000-6362.2023.09.004

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Buckwheat is the major food crop in high altitude areas such as Liangshan district, Sichuan province, China. In order to explore the cold resistance of buckwheat and screen excellent buckwheat germplasm resources adapted to Liangshan district, 5 common buckwheat (Fagopyrum esculentum Moench.) and 13 Tartary buckwheat [Fagopyrum tataricum (L.) Gaertn. ], the most extensive varieties and landrace, were used to evaluate the cold resistance during seed germination stage at 4℃(low temperature condition) and 22℃(control condition). Seven indices related to germination and growth were measured, including radicle length, germination rate and germination potential. Comprehensive cold resistance was reflected by subordinate function analysis, principal component analysis and cluster analysis. The results showed that under low temperature conditions, the seed germination of all buckwheat materials was delayed and the germination rate was retarded. Compared with Tartary buckwheat, seven germination and growth indexes of common buckwheat maintained a higher level, indicating that common buckwheat was more tolerant under low temperature environment. The comprehensive evaluation of the membership function results suggested that Jiuzhaigou common buckwheat had the strongest low temperature tolerance ability at the germination stage, followed by Pintian No.3, whereas Xiqiao No.6 was the most sensitive to low temperature.

Simulation of Winter Wheat Yields in Guanzhong Region Based on DSSAT Model and Its Influencing Factors

CHEN Jia-jun, SHI Xiao-liang, DING Hao, SHI Meng-qi

2023, 44(09): 805-819. doi:10.3969/j.issn.1000-6362.2023.09.005

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Based on the field experiments of two field experiment sites and the daily meteorological data of 11 meteorological stations evenly distributed in the winter wheat planting area of Guanzhong region in Shaanxi Province, the DSSAT model was used to determine the genetic parameters of winter wheat cultivars, and then the key phenological periods and yield of winter wheat at each station from 2001 to 2019 were simulated. The M−K test and the Sen trend analysis method were used to reveal the spatial and temporal evolution characteristics and laws from the station and regional scales. On this basis, the gray correlation method and multiple linear regression analysis method were used to explore the sensitive meteorological factors and their contribution rates affecting the simulated yield at each growth period. The results showed that: (1) the average RRMSE values of winter wheat flowering period, mature period and yield simulation results were 0.91%,0.98% and 7.87% in Yangling (Guanzhong Plain) field experiment site, and 2.39%,1.35% and 9.30% in Changwu (Weibei Dryland) field experiment site. In the regional phenological simulation, the RRMSE of winter wheat in the Guanzhong Plain and the Weibei Dryland were 3.2% and 3.0% at the flowering and mature periods, R² were 0.71 and 0.73, and the RRMSE of regional yield were 23.6% and 11.2%, respectively.(2) The sowing to flowering period and mature period of winter wheat in Wugong station showed a delayed trend, and the rates were 0.70d·10y⁻¹ and 0.22d·10y⁻¹, respectively, while the other stations showed an earlier trend. The advance trend of phenological period in Guanzhong Plain was higher than that in Weibei Dryland, and the advance trend from sowing to flowering period reaches 2.30d·10y⁻¹ and 1.20d·10y⁻¹ respectively, and the advance trend from sowing to maturity was 0.60d·10y⁻¹. The simulated yields showed a decreasing trend at Pucheng and Weicheng stations, while an increasing trend at other stations. The lowest and highest values of regional yield appeared in 2013 and 2017, respectively. (3) The increase of daily average temperature and daily minimum temperature in most stations would promote the increase of winter wheat yield in the pre-winter growth period. The increase of daily maximum temperature and total precipitation contributed greatly to the increase of yield in the overwintering period. The increase of daily maximum temperature at greening and heading period would lead to serious yield decrease of winter wheat, but the increase of daily relative humidity would promote the increase of yield. The increase of daily average temperature, daily minimum temperature and daily maximum temperature at most stations would lead to a decrease in winter wheat yield during the filling and mature period. Temperature was the main controlling factor affecting the yield of winter wheat in Guanzhong region, and its influence on yield varies greatly at different growth periods.

Analysis on Characteristics of Spring Tea Frost Damage in Different Risk Areas in Jiangsu Province

REN Yi-fang, WANG Pei-juan, QIAN Ban-dun, MA Yun-bo, SUN Qin-fei

2023, 44(09): 820-833. doi:10.3969/j.issn.1000-6362.2023.09.006

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Using global atmospheric reanalysis data ERA5 from 1981 to 2020, based on the meteorological indicators representing the degree of tea frost damage, the risk index (RI) during the spring frost monitoring period in Jiangsu province was constructed. The k-means clustering algorithm was selected to realize the spring tea frost risk zoning. Based on that, the Mann-Kendall method was applied to identify the climatic abrupt change points in each frost risk region, the impacts of climate change on the occurrence characteristics of spring tea frost in different risk areas were assessed by the daily and hourly scales, separately. The result showed that the frost risk of spring tea in Jiangsu province was characterized by "low in the southwest and high in the northeast". Light to moderate frost and extremely severe frost mainly occurred in low-risk area and high-risk area, with an average frequency of 11.91% and 15.4%, respectively. In the low-risk and high-risk areas, the average appearance times of the frost ending date showed an advance trend of 2.7d10y⁻¹ and 1.5d10y⁻¹, while RI value showed a decreasing trend of 0.024 and 0.015 per 10 years, respectively. Influenced by climate change, in terms of daily time scale, the occurrence frequency and volatility of spring tea frost at all levels during the monitoring period in low-risk and high-risk areas were significantly reduced, especially in the case of severe frost. The distribution patterns of occurrence frequency of spring tea frost at all levels changed from the type of multi peak to the type of single peak with descending trend, while still having different peak times, but mainly concentrated in the first ten days of February to the last ten days of March. From the hourly time scale, the occurrence frequency of spring tea frost at all levels basically presented a "sinusoidal" distribution pattern. After climate change, the high incidence period of mild frost was delayed for two to four hours, and that of moderate to severe frost was basically unchanged or delayed for one hour, and the high incidence period of moderate to severe frost and extra severe frost were concentrated at 5：00−7：00 and 6：00−8：00 respectively in the morning for each risk region. With the climate change, the spring tea frost in Jiangsu was characterized by "later, weaker, shorter and fewer", which still needed to be actively addressed.

Analysis on Change Characteristics of Drought Intensity during the Growth Period of Highland Barley in Tibet

SHI Ji-qing, DOU Yong-li, ZHANG Xin-ping, XI Feng, LUO Zhen, GAN Chen-long

2023, 44(09): 834-844. doi:10.3969/j.issn.1000-6362.2023.09.007

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Based on the daily meteorological data of 25 meteorological stations in the main highland barley planting areas in Tibet from 1981 to 2020, the daily meteorological drought comprehensive index (MCI) was calculated. The Mann-Kendall mutation test, Morlet wavelet analysis and R/S analysis were used to analyze the temporal and spatial distribution and trend change of drought intensity in each growth period of the region in the past 40 years, in order to provide a scientific basis for agricultural production safety and local disaster prevention and mitigation in Tibet. The results showed that: (1)the drought characteristics of Tibetan highland barley at different growth stages were different, and the drought intensity at the sow-tillering stage was not significantly increased, while the drought intensity at the whole growth stage was significantly decreased compared with that at the tiller-heading stage and the heading-maturity stage.（2）The drought intensity at the sow-tillering stage reached the lowest level in the 2000s, and the tiller-heading stage, head-maturity stage and the whole growth reached the highest level in the 1980s. The drought intensity of tiller-heading stage, head-maturity stage and the whole growth stage showed significant weakening mutations in 1989, 2001 and 1989, respectively. (3)The drought intensity at the sow-tillering stage was weakened as a whole, and the regional difference between tiller-heading stage was small, while the spatial difference between head-maturity stage was large. The drought intensity in the whole growth period showed a distribution feature of increasing from the central and southern marginal areas of the study area to the east and west. (4) The future drought intensity in the sow-tillering stage, the head-maturity stage and the whole growth stage has a trend of continuous drought on the scale of 15 years, 33 years and 33 years respectively, and the tiller-heading stage has a trend of continuous wet on the scale of 13 years.

Remote Sensing for the Planting Area of Major Grain Crops in Complex Terrain Regions by Integrating Multiple Spectral Indices with Topographic Features

FAN Li, WANG Yan, ZHU Hao, ZHANG Ji

2023, 44(09): 845-856. doi:10.3969/j.issn.1000-6362.2023.09.008

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Accurate monitoring of crop spatial distribution in topographically complex areas is of great significance for guiding agricultural management production and reasonable allocation of resources. However, scattered crop distribution and high spatial heterogeneity pose challenges for precise classification. The objective of this study was to explore a method for simultaneous precise identification of multiple crops with multi-temporal high-resolution satellite data under complex terrain conditions, thus further providing a theoretical and practical basis for crop identification in Chongqing city area and the complex low hills area in southwest China. The western Chongqing was selected as the study area. First, a multi-scale segmentation algorithm was adopted to construct homogeneous units from fields of the same feature type. This approach helped to achieve high accuracy classification by avoiding overly fragmented classification results based on pixel classification. Secondly, the multi-temporal Sentinel-2/MSI remote sensing images were used to explore the weathering patterns and characteristic parameters during the fertility period of major food crops. The spectral indices, such as NDVI, RVI and NDWI, were constructed to compare the differences in remote sensing spectral information of different crop types at various fertility periods based on ground sample points. Such information was then combined with the topographic features to determine the optimal combination for crop identification. Finally, an object-oriented decision tree logical classification rule set was established to extract major grain crop growing areas. The results showed that, (1) the multi-scale segmentation method was an effective approach that can make crop identification on a field basis. In addition, the vegetation edge segmentation was optimal at a segmentation scale of 30 and a compactness and shape factor of 0.5. (2) The target feature discrimination threshold was established by combining the spectral feature indices of NDWI in April, RVI in June, NDVI in August and NDVI in August with the topographic features such as altitude and slope. The overall accuracy of the classification reached 90.8%, being 85.7%, 83.3% and 80.7%, for paddy rice, maize, and sweet potato, respectively. This paper showed that the crop planting area identification method based on multiple spectral indices combined with topographic features can achieve high recognition accuracy and has practical significance.

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