中国生态农业学报(中英文)

Crop production and agricultural water consumption in the Beijing-Tianjin-Hebei region: History and water-adapting routes

QI Yongqing, LUO Jianmei, GAO Ya, MIN Leilei, HAN Linna, SHEN Yanjun

2022, 30(5): 713-722. doi: 10.12357/cjea.20210726

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Abstract:
The amount of water resources in the Beijing-Tianjin-Hebei (BTH) region is less than 1% of China, but support approximately 8% of the national population produces 10% of gross domestic product (GDP). Water shortages and groundwater overexploitation are key constraints to the sustainable development of the BTH region. Agricultural water use dominates regional water withdrawal, accounting for 70% of all water use, and the irrigation of high-intensity cropping systems has caused notable groundwater depletion over the past several decades. In this study, the historical stage characteristics of agricultural production scale and irrigation expansion were analyzed based on statistical data. Before 1949, irrigated farmland was mainly located in the piedmont plain of the Taihang Mountains for high-value crop production, irrigation scale and water withdrawal were limited. After 1949, electromechanical irrigation wells gradually replaced traditional shallow wells, and irrigation became a conventional measure for crop production. Since the end of the 1970s, a well-irrigated system has covered the BTH region. Groundwater irrigation provided dominant support for stable agricultural production and sustained high yield. The wheat-maize double-cropping system was enhanced. Simultaneously, the production capacity of fruits and vegetables increased rapidly. The output of grain crops increased from 2.1362×10⁷ t to 3.9448×10⁷ t, an increase of 84.7%. Vegetable production increased from 1.0937×10⁷ t to 5.5084×10⁷ t, an increase of 403.6%. The fruit output increased from 1.440×10⁶ t to 1.5052×10⁷ t, with a 945.6% increase. High yields depended on adequate irrigation, and groundwater depletion occurred as a result of a trade-off between water and agricultural products in the BTH region. Over the last four decades, agricultural production in Beijing, Tianjin, and Hebei has diverged in terms of scale and structure. The crop planting areas of Beijing and Tianjin decreased by 85.0% and 38.7%, respectively. Beijing has almost abandoned grain crop production, but the agricultural production capacity of Hebei Province has further increased. In 2018, 93.8% of grains, 99.1% of oilseeds, 92.9% of cotton, 93.1% of vegetables, and 91.7% of fruits in the BTH region were contributed by Hebei Province. This pattern of differentiation intensified the importance of agricultural production in Hebei Province in the BTH region, which has reliably increased the pressure on agricultural production and water withdrawal in Hebei Province. Studies have explored cropping systems that are more sustainable for groundwater sustainability. Based on field experiments and crop models, it was confirmed that reducing planting intensity can help mitigate groundwater decline, and winter wheat has been reported to be the main contributor to groundwater consumption. The cropping system of three harvests over two years has been suggested as a better alternative cropping system for water savings than the current winter wheat-summer maize double cropping system, which could save more water each year with a slight grain yield loss. However, the interaction between grain production capacity and water consumption intensity on medium- and long-term time scales for different water-adapting rotations of crops remains unclear and insufficient. From a policy-making perspective, it is necessary to improve the comprehensive agricultural plan under the conditions of the BTH coordinated development strategy. To ensure regional food security and stable agriculture, the water-adapting transformation of agricultural production in the BTH region should be promoted in an orderly and efficient manner.

Climate change and its effect on winter wheat yield in the main winter wheat production areas of China

WANG Yan, ZHANG Xiaolong, SHI Jiali, SHEN Yanjun

2022, 30(5): 723-734. doi: 10.12357/cjea.20210702

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Abstract:
Climate change plays an important role in crop growth and grain yield. Therefore, there is an urgent need to understand the distribution characteristics and changing trends of climatic factors in the main crop production areas. Furthermore, analyzing the impact of meteorological factors at different crop growth stages is of great significance for maintaining food security and agricultural disaster prevention. In this study, the spatial distribution and variation trends of six critical meteorological factors during the winter wheat growing season in the main winter wheat production areas of China were investigated based on meteorological and phenological data from 69 meteorological and 77 agricultural stations located in the study area. The relationship between winter wheat yield fluctuation and meteorological factors was explored using a multiple regression model. The changing characteristics of meteorological factors in a typical low-yield year was evaluated to identify the key growth stage for winter wheat and the restrictive meteorological factors in the study area. The results showed the following: 1) From 1960 to 2019, the spatial distribution of meteorological factors in the main winter wheat production areas of China was uneven and the variation trends were different. The mean temperature (T_mean), effective precipitation (Pre), and cooling degree days (CDD, the accumulated temperature for daily minimum temperature below 0 ℃) were higher in the southern regions, including Jiangsu Province, Anhui Province, and Henan Province; whereas the sunshine duration (SD), daily temperature range (DTR), and heating degree days (HDD, the accumulated temperature for daily maximum temperature above 30 ℃) were higher in the northern regions, such as Hebei Province, Shandong Province, Beijing, and Tianjin. The T_mean and CDD showed significant increasing trends with average rates of 0.33 ℃∙(10a)⁻¹ and 43.42 ℃∙(10a)⁻¹, respectively; whereas the SD and DTR significantly decreased at rates of 42.30 h∙(10a)⁻¹ and 0.17 ℃∙(10a)⁻¹, and the Pre and HDD trends were spatially heterogenous. 2) The average annual winter wheat yield in different provinces and cities ranged from 3426 kg∙hm⁻² to 5910 kg∙hm⁻² with significantly increasing trends (P < 0.05), but the interannual fluctuation was large in most regions. The determination coefficient for the effect of meteorological factors on winter wheat yield ranged from 0.15 to 0.80, and the winter wheat yield in Shaanxi Province was most affected by climate change (P < 0.05). Over the whole growth period, the ranking of the meteorological factor’s contribution rate to yield was DTR > SD > Pre > CDD > T_mean > HDD. 3) In a typical low-yield year, the key winter wheat growth period was from heading to maturity, and the restrictive meteorological factors during this period were SD, DTR, and Pre. Therefore, future agricultural management and wheat breeding programs must consider the current distribution characteristics and trends of meteorological factors for improving the winter wheat productivity. More importantly, we should pay special attention to restrictive meteorological factors, such as Pre, SD, and DTR, during the critical growing stage of winter wheat from heading to maturity so that it can better cope with meteorological disasters.

Variation of evapotranspiration and its response to vegetation productivity in the North China Plain

WANG Linna, HAN Shumin, LI Huilong, YANG Yonghui

2022, 30(5): 735-746. doi: 10.12357/cjea.20210922

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Abstract:
The North China Plain is a main grain production area in China, where the shortage of water resources is the main factor restricting regional grain production and socioeconomic development. Clarifying the temporal and spatial variation of evapotranspiration (ET) and analyzing the main driving factors are critical for exploring regional water resource evolution and optimizing water resource management. Based on the PML_V2 (Penman-Monteith-Leuning Evapotranspiration V2) remote sensing ET product released in 2019 with a spatial resolution of 500 m and temporal resolution of 8-day, Theil-Sen Median slope estimation and Mann-Kendall trend analysis were used to evaluate the changing trend of ET; and the correlation coefficient method was used to analyze the relationship between ET and vegetation productivity. To evaluate the ET variation at the pixel scale, the significance of variation, and driving factors in four agricultural areas representing three agricultural area types were selected: Shijiazhuang and Baoding, Hengshui, and Dezhou, which represented the piedmont plain of Taihang Mountains, central low plain, and Yellow River irrigation area, respectively. The results showed that the annual average ET was 588.1 mm from 2001 to 2019 in the whole North China Plain, the interannual variability was characterized by a low-high-low dynamic trend, and the maximum (665.4 mm) and minimum (542.2 mm) ET occurred in 2015 and 2001, respectively. The ET trends during different crop growth seasons were significantly different. During the wheat growth season, the overall ET trend was declining, possibly resulting from the policies, such as wheat conversion to fallow, and limitation of groundwater pumping, which are being implemented to alleviate the groundwater funnel in North China. The overall ET trend was significantly upward in the corn growth season. Additionally, there were significant differences among the annual average ET for different land use types. The ET in 85.5% of the agricultural land areas showed an upward trend, of which 42.3% increased significantly and was mainly distributed in the Yellow River irrigation area. For the annual average ET in urban land, the areas with decreasing and increasing trends were 50.9% and 49.1%, respectively. Urbanization resulted in a significant decline in ET in the expanding areas of large cities, whereas an increasing trend was observed in the downtown regions of large cities, such as Beijing and Tianjin. Correlation analysis showed that areas with a positive correlation between ET and NDVI (normalized difference vegetation index) accounted for 76.54% of the North China Plain, and areas with a positive correlation between ET and GPP (gross primary production) accounted for 87.6% of the entire region. The stronger correlation between ET and GPP indicated the influence of higher crop productivity on ET in major grain-producing areas, which was also proven by the correlation between ET and vegetation productivity in the four typical agricultural areas. There were significant correlations between ET and GPP/NDVI in the Yellow River irrigation area represented by Dezhou. The only significant correlation between ET and GPP was observed for the central low plain, represented by Hengshui. Non-significant correlations between ET and GPP/NDVI were seen in the piedmont plain represented by Shijiazhuang and Baoding, possibly resulting from multiple ET driving factors, including vegetation productivity.

Changes in and influencing factors of crop coefficient of winter wheat during the past 40 years on the Taihang Piedmont Plain

LI Haotian, LI Lu, YAN Zongzheng, GAO Congshuai, HAN Linna, ZHANG Xiying

2022, 30(5): 747-760. doi: 10.13930/j.cnki.cjea.210342

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The crop coefficient (K_c) is defined as actual evapotranspiration (ET) under sufficient water supply divided by the reference crop ET (ET₀), which can be calculated using meteorological factors. The K_cis used as a basic parameter to calculate the crop water requirements. The accurate determination of K_c plays an important role in optimizing irrigation management. The K_c changes with crop growth and environmental conditions. The purpose of this study was to assess how K_c varied with crop production and weather conditions by using a long-term field experiment of field management measures of winter wheat. The actual ET of winter wheat under sufficient irrigation and ET₀ derived from daily meteorological parameters at Luancheng Agro-ecosystem Experimental Station of the Chinese Academy of Sciences from 1980 to 2020 were used to calculate the seasonal K_c. Additionally, the dominant factors affecting the K_c of winter wheat under the current production conditions were identified from experimental data of three recent years (2017–2020). The results showed that for winter wheat with sufficient water supply from 1980 to 2020, the average ET and ET₀ were 434.7 mm and 550.8 mm, respectively. The ET₀ was relatively stable, and the ET increased by 17.6%. The average K_c was 0.80 during the past four decades, with an average value of 0.76 in 1980–1990, 0.80 in 1991–2000, 0.81 in 2001–2010, and 0.84 in 2011–2020, indicating a continuously increasing trend. In the past four decades, the yield of winter wheat had increased by 42.4%, and K_c had increased by 11.6%. The increase in ET was the main reason for the increase in K_c. The ET during the past four decades increased with increasing crop production, and with a relatively stable ET₀, the K_c increased. Therefore, the K_c varied with changes in crop grain production, which was related to biomass production and canopy size. Under the current growing conditions, leaf area index and biomass were important factors that affected K_c. When the leaf area index reached a certain level, K_c was mainly affected by the atmospheric evaporation potential determined by the saturated water vapor pressure difference and atmospheric temperature. The K_c during the recent three years was 0.79 for 2017–2018, 0.86 for 2018–2019, and 0.79 for 2019–2020. The average ET was 442.3 mm during the three years, and the average K_c at different growing stages of winter wheat were 0.70 from sowing to winter dormancy, 0.42 during winter dormancy, 0.76 from recovery to jointing, 1.18 from jointing to heading, 1.39 during heading to grain-fill, and 0.96 during maturity. Thus, the water requirements for winter wheat after winter dormancy increased sharply and reached the highest values during the heading to earlier grain-filling stages. The results from this study indicate that K_c varies with changes in the crop growing conditions and should not be taken as a constant value. K_c developed during three recent seasons in this study could be used to determine the crop water requirements for irrigation scheduling under the current growing conditions.

Effects of long-term warming and nitrogen fertilization on soil respiration and temperature sensitivity in the North China Plain

HU Wenpei, ZHANG Chuang, HU Chunsheng, DONG Wenxu, WANG Yuying

2022, 30(5): 761-768. doi: 10.12357/cjea.20210237

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Under global warming and elevated nitrogen deposition, it becomes an urgent problem to find out how farmland soil respiration responds to climate warming and increasing nitrogen deposition in the North China Plain, one of the main grain-producing areas in China. In this study, the soil respiration rate and temperature sensitivity were measured using a static chamber gas chromatography method from 2018 to 2020. The soil respiration rate and temperature sensitivity were determined by field heating and nitrogen application for 11 years. Three treatments: infrared warming (W) (with an annual average increase of 1.5 °C according to our previous results), nitrogen fertilization (N) (240 kg(N)∙hm⁻²∙a⁻¹ urea), and combined warming and nitrogen fertilization (WN) were used in this study. An untreated control treatment (CK) was also included. The results showed that the W and WN treatments increased soil temperature at 5 cm depth by approximately 2 °C on average and decreased soil water content by 2.4% from 2018 to 2020. The average soil respiration rate (329.06 mg∙m⁻²∙h⁻¹) in the growing season from March to June was significantly higher than that in the dormancy season from November to March (25.21 mg∙m⁻²∙h⁻¹) (P < 0.05). From 2018 to 2020, the W and WN treatments increased the soil respiration rate by 16.8% and 19.3%, compared with CK, respectively (P < 0.05). The N treatment had no significant effect on the soil respiration rate. During the same period, the temperature sensitivity (Q₁₀) of soil respiration in the W and WN treatments was lower than that in the N and CK treatments, that was in the order of WN (1.65) < W (1.70) < N (1.78) < CK (1.80). The Q₁₀ of soil respiration showed obvious seasonal variations, with an average high of 2.93 in the winter dormancy season and an average low of 1.81 in the summer growing season. This study showed that the temperature sensitivity of the soil respiration was decreased as temperature increased, and that Q₁₀ showed significant seasonal differences. This information will help improve the accuracy of future carbon estimation models.

Classification of agricultural critical zones in the North China Plain

MA Wanjun, MIN Leilei, QI Yongqing, LIU Meiying, WU Lin, SHEN Yanjun

2022, 30(5): 769-778. doi: 10.12357/cjea.20220042

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The Earth’s critical zone is an area where water and solutes, as well as energy, gases, solids, and organisms, are exchanged among the atmosphere, hydrosphere, biosphere, lithosphere, and pedosphere, creating a life-sustaining environment for human society. In the vertical direction, the Earth’s critical zone goes up to the plant canopy and down through soil layers, unsaturated vadose zones, and saturated aquifers. Laterally, the Earth’s critical zones include not only weathered loose strata but also lakes, rivers, shallow marine environments, and vegetation. Earth’s critical zone studies mostly focus on the interaction between air, water, organisms, soil, surface rocks, and soil, integrating aboveground and belowground, time and space, and living and abiotic factors. This provides a basis for a comprehensive analysis of the evolution of complex terrestrial ecosystems and interdisciplinary research. The critical zones of the Earth are classified according to the differences in land use, among which the agricultural critical zone is the most strongly affected by human activities. However, most studies only consider surface function elements, without considering the important elements in the vadose zone and aquifers. The North China Plain (NCP) is a highly productive region where groundwater overexploitation and pollution are the major concerns. The crop-soil-aquifer critical zone perspective can provide new ideas for groundwater protection. Classification of the agricultural critical zone is the early basis for the study of regional groundwater volume/quality evolution and spatial differences. However, there has been little research on the classification of critical agricultural zones in the NCP. The classification of the agricultural critical zones in the NCP refers to the scheme for a comprehensive natural zone to a certain extent. By analyzing the hydrogeological conditions of the area and other information, combined with regional characteristics, the new classification followed the principles of comprehensiveness and dominant factors were developed with a three-level classification scheme for agricultural critical zones in the NCP by comprehensively considering the quaternary geology and geomorphology, shallow groundwater salinity, groundwater table depth, and agricultural land use factors. Taking the NCP as an example, agricultural critical zone zoning and mapping were carried out using the superposition method to superimpose and merge the classification elements, and an agricultural zone classification scheme was proposed. Finally, the results of this study divided the agricultural critical zone in the North China Plain into three first-level units, 13 second-level units, and 38 third-level units. This study has important reference significance for promoting the development of Earth critical zones, systematically understanding agricultural activities and their impacts on critical zone processes, and conducting research on the integrated management of regional groundwater and natural resources based on protection.

Research progress on the wheat powdery mildew resistance gene Pm2

JIN Yuli, GU Tiantian, LIU Hong, AN Diaoguo

2022, 30(5): 779-786. doi: 10.13930/j.cnki.cjea.210279

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Wheat (Triticum aestivum L.) is an important crop in China, high and stable yields are crucial for ensuring food security. Powdery mildew caused by Blumeria graminis f. sp. tritici. (Bgt) is a devastating disease of wheat. Chemical and agricultural control methods are used to prevent powdery mildew, but utilizing host resistance may represent a more economical, environmentally friendly, and effective method to control the epidemic of powdery mildew. The powdery mildew resistance gene Pm2, located on the short arm of chromosome 5D, encodes a CC-NBS-LRR protein and is one of the most widely used Pm genes in wheat powdery mildew resistance breeding because of its excellent resistance and desirable agronomic traits. In this review, the recent progress in Pm2 research and utilization in wheat breeding is systematically summarized in terms of the following aspects: identification and characterization of Pm2, exploration and utilization of the alleles at the Pm2 locus, gene cloning, development of functional markers, haplotype analysis, AvrPm2 gene cloning, and the applications in wheat breeding programs. It has been proposed that: 1) the differences in the resistance of different Pm2 alleles may be caused by diverse genetic backgrounds, other regulatory factors in the disease resistance pathway, or the highly heterozygous state of Bgt isolates. 2) The powdery mildew resistance gene Pm2 should be reasonably distributed and utilized in disease resistance breeding to prolong the service life of disease resistance genes and increase durability. 3) Essential methods to control the epidemic of powdery mildew should include mining and utilizing novel resistance genes and allelic variations and strengthening the innovation of new wheat germplasms. This review aimed to provide a theoretical basis for further work on the resistance mechanism of Pm2 and to accelerate its application in wheat powdery mildew resistance breeding.

Research progress and prospects of foxtail millet salt tolerance

LIU Wenwen, QIAO Yunzhou, YANG Hong, LI Yongpeng, QIAO Wenjun, DONG Baodi, LIU Mengyu

2022, 30(5): 787-798. doi: 10.12357/cjea.20210424

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With the adjustment of the agricultural planting structure, foxtail millet — a drought-resistant and barren-tolerant crop, has attracted increasing attention in arid and saline-alkali areas. Systematic and deep understanding of the salt tolerance as well as physiological and ecological response characteristics of foxtail millet under salt stress has important guiding significance for maximizing the excellent properties of foxtail millet, increasing its yield in saline-alkali areas, and improving farmers’ income. This paper reviewed the research progress worldwide in detail from three aspects, namely, the screening index and evaluation of foxtail millet salt tolerance, the change law of plant growth and development and physiological-ecological response under salt stress, and the discovery of foxtail millet salt tolerance genes. At present, a single indicator of salt tolerance in foxtail millet is used, which mainly depends on the germination rate during germination. Other physiological and ecological indicators have not been fully considered. Because of the differences in foxtail millet varieties and soil salinity, there are differences in aboveground and underground agronomic characteristics, photosynthetic characteristics, enzymes related to scavenging reactive oxygen species, and the hormone response law of foxtail millet plants. Therefore, it is difficult to establish comprehensive evaluation indexes. The expression and function of foxtail millet salt tolerance genes are related to environmental conditions such as high salt, drought, and abscisic acid. The salt tolerance of foxtail millet was improved by synthesizing specific proteins to enhance the antioxidant system, protect cells from damage, and improve the ability to resist osmotic stress. Based on the results, we recommend that the establishment of quantitative standards and platforms for the comprehensive evaluation and selection of foxtail millet salt tolerance, the in-depth research on the regulation mechanism of foxtail millet salt tolerance, and further research and development of foxtail millet salt tolerance cultivation technology systems are important future research directions.

Review of research development associated with the application of saline water irrigation to vegetables

CHEN Pei, WANG Jintao, DONG Xinliang, TIAN Liu, ZHANG Xuejia, LIU Xiaojing, SUN Hongyong

2022, 30(5): 799-808. doi: 10.12357/cjea.20210850

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Freshwater resources are scarce and unevenly distributed in China. The exploitation of saline water resources is of great significance to the success of water security strategies. Currently, there are researches focusing on overcoming the difficulties associated with saline-water utilization. The sowing area and yield of vegetables are the highest in the world, but vegetables are economic crops with relatively large water consumptions. The main problem faced by freshwater shortage regions is how to safely use saline water resources, broaden the supply source of vegetable irrigation water, and ensure vegetable production. Therefore, this paper reviews the mechanisms and technologies associated with the application and future development of saline water irrigation in vegetable planting from the aspects of the utilization potential of saline water resources; application status of saline water irrigation; and effects of saline water irrigation on vegetable growth, yield, and quality to provide water resources that guarantee the high-quality green development of agriculture. The results showed that using 2.4−11.83 dS∙m⁻¹ saline water irrigation reduced vegetable yields by 6.21%−63.05% but improved vegetable quality by 6.25%−74.07%. Using suitable saline water irrigation regulation technologies and optimizing irrigation strategies can improve the utilization efficiency of saline water irrigation and play an important role in the sustainable development of agriculture in the future.

Adaptability evaluation of soil moisture products in the Hebei Plain

SHI Jiali, ZHANG Xiaolong, MIN Leilei, ZHANG Jing, WANG Yan, SHEN Yanjun

2022, 30(5): 809-819. doi: 10.12357/cjea.20210697

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The Hebei Plain, located in the central part of the North China Plain, is an important grain production area in China and one of the most productive areas worldwide for winter wheat and summer corn. Soil water is foundation of material transportation and energy transmission; and participates in the carbon-water cycle and energy exchange between the land surface and atmosphere. It is also a direct water source and key element of crop growth, which has an important impact on agricultural production, weather forecasting, and drought prediction. Although multisource soil moisture products have been extensively developed and widely utilized, a comprehensive evaluation of the applicability of these products in the Hebei Plain is lacking. Evaluating the applicability of soil moisture products and using them to understand the soil moisture dynamics of the Hebei Plain are of great significance for agricultural production, moisture monitoring, and irrigation decision-making. To compare and analyze the specific performance of the soil moisture products of SMOS, SMAP, FY3B, ERA-Land, GLDAS, and GLEAM in typical farmland in the Hebei Plain, in-situ soil moisture data of surface soil moisture from Wangdu, Bazhou, Weixian, and Luancheng stations in the Hebei Plain from January 2018 to October 2019 were analyzed by considering correlation coefficients, biases, root mean square errors, and unbiased root mean square errors (ubRMSE). Overall, except the data of FY3B in summer, all soil moisture products underestimated the actual soil water contents of different stations in the Hebei Plain. The average correlation coefficient of each soil moisture product during the study period was ranked as GLEAM > FY3B > ERA-Land > GLDAS > SMAP > SMOS, and the average ubRMSE was ranked as GLEAM < GLDAS < SMAP < ERA-Land < SMOS < FY3B. The specific performance of each soil moisture product showed that 1) based on assimilated multi-source data, the accuracies of GLDAS, GLEAM, and ERA-Land were better than those of SMOS and SMAP, with high correlation coefficients and low ubRMSE. The inversion data of GLDAS, GLEAM, and ERA-Land were relatively close to the in-situ data when the water content was high in summer. 2) Many missing data and large fluctuation ranges were found in the FY3B product, but FY3B had a good relationship with the in-situ data with an average correlation coefficient of 0.43 m³∙m⁻³. The soil water content was generally overestimated in summer and underestimated in the other seasons. The correlation coefficient of FY3B in summer was low, but the opposite was true in autumn. 3) Overall, the data accuracy of SMAP was higher than that of SMOS. The correlation coefficient between SMAP and in-situ data was higher in summer, but the ubRMSE was higher at the same time; however, they had opposite values in autumn. SMAP could capture dynamic changes in soil moisture when the soil moisture content is high. The data accuracy was better when the measured soil water content was between 0.30 m³∙m⁻³ and 0.40 m³∙m⁻³. 4) Owing to radio frequency interference and other reasons, SMOS greatly underestimated the soil moisture content and performed the worst at each station. The average correlation coefficient of each station was only 0.20 m³∙m⁻³, and the biases were all greater than 0.10 m³∙m⁻³.

Temperature effects of straw mulching on the agronomic and physiological characteristics of winter wheat

CHEN Suying, NIU Junfang, ZHANG Xiying, SHAO Liwei, YAO Zhengang, LI Jianbo

2022, 30(5): 820-830. doi: 10.12357/cjea.20220120

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Straw mulching is a popular water-saving technology that is widely used in dry farming areas. However, the negative effects of straw mulching on soil temperature should be avoided when it is used on crops grown in cool seasons. Field experiments were conducted to investigate the temperature effects of straw mulching on the physiological and agronomic properties of winter wheat and to find solutions to reduce the negative effects of straw mulching on winter wheat production. An experiment consisting of four treatments was set up at the Luancheng Agro-Ecosystem Experimental Station, Chinese Academy of Sciences in 2019–2020, which were no mulching (CK), low-rate straw mulching (2450 kg∙hm⁻², LM), medium-rate straw mulching (3675 kg∙hm⁻², MM), and high-rate straw mulching (7350 kg∙hm⁻², HM). The physiological characteristics (endogenous hormones, concentration of stem bleeding ions) and agronomic traits (NDVI, RVI [ratio vegetation index], dry matter accumulation, root length density, and winter wheat yield) were monitored. The results showed that straw mulching increased the soil temperature during winter dormancy and decreased the soil temperature in spring when winter wheat entered the recovery stage. The warming effects of mulching did not affect winter wheat growth during the winter dormancy period because the crop was inactive. When winter wheat entered the recovery stage after winter dormancy, the effects of straw mulching on soil temperature inhibited the growth and development of winter wheat. At the recovery stage, the stem auxin (IAA) contents in the LM, MM, and HM treatments were 1.7, 2.5, and 2.7 times that of CK, respectively. The higher IAA content inhibited the growth of winter wheat. The ratio of IAA to zeatin riboside (ZR) increased in the stems of mulched plants, which inhibited tiller growth. Agronomic characteristics, such as root length, NDVI, RVI, plant density, and aboveground biomass of winter wheat at the recovery stage, were all significantly lower than those of CK. At the jointing stage, when the effects of straw mulching on soil temperature were weaker, the IAA content in wheat stems in mulching treatments significantly decreased and was even lower than that of CK treatment. The IAA/ZR ratio also rapidly decreased, and its difference from that of the CK also decreased. The ion concentrations in the stem sap in mulching treatments were higher than those in CK, indicating that the physiological properties of winter wheat under straw mulching were strengthened; however, the increased growth could not compensate for growth loss during the long recovery stage. The values for the agronomic characteristics under straw mulching were lower than those under CK at the jointing stage. The growth of winter wheat under straw mulching was delayed by 2 days at heading and anthesis. The yield of winter wheat under the straw mulching treatments was lower than that under CK. The results showed that the decrease in soil temperature at the recovery stage caused by straw mulching delayed the growth of winter wheat and was the main reason for the decrease in winter wheat production. The effects of straw mulching on soil temperature and the physiological and agronomic properties increased with the increased straw amount. Therefore, breaking the straw layer to reduce the negative effects of straw mulch on soil temperature during the recovery stage would be an effective measure to promote the positive effects of straw mulching on winter wheat.

Yield- and efficiency-increasing effect of new tillage-fertilization-sowing method on wheat in the North China Plain

XU Ping, YANG Xianjie, FENG Zuolong, SUN Yanling, YANG Zhen, ZHANG Xiqun, DENG Xuebin, SHI Jiayi, ZHANG Zhengbin

2022, 30(5): 831-841. doi: 10.12357/cjea.20210851

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Abstract:
The North China Plain is the main production area of summer corn-winter wheat in China; however, the long-term large area management of no-tillage sowing corn and rotating tillage sowing wheat leads to shallow tillage layers and poor yield and efficiency. The North China Plain is also an area with serious groundwater overexploitation and a key area for the development of modern water-saving agriculture. To break the hardpan, improve water and nutrients use efficiencies, reduce the frequency of farming operations and production costs, we conducted an experiment on a comprehensive technology of tillage-fertilization-seeding of corn and wheat. A split-plot design was used in this study. In the main plot, two treatments were set up: 1) no-tillage seeding of corn in the front stubble and 2) deep tillage-delamination fertilization and sowing of corn. In the main plot of no-tillage corn seeding, two sub-zones were set up: artificial fertilization-rotary tillage and drill sowing of wheat (T1) and artificial fertilization-rotary tillage-deep loosening and drill sowing of wheat (T2). In the main plot of the treatment with deep tillage-delamination fertilization and sowing of corn, two sub-zones were set up: artificial fertilization-rotary tillage-strip seeding of wheat (T3) and rotary tillage-deep loosening-delamination fertilization-wide uniform seeding of wheat (T4). At the tillering, jointing, flowering, and maturing stages, wheat growth, dry matter accumulation, and yield traits were investigated and compared, and the water use efficiency and partial factor nitrogen productivity of wheat, annual total yield of corn and wheat, and output/input ratio were analyzed. The results showed that the T4 treatment significantly reduced soil bulk density in the 0–40 cm layer, increased soil moisture content in the deep layer, optimized nutrient distribution in soil layer, and increased plant height, tillers number, dry matter weight of shoot and root in the 0−40 cm layer, thus increasing spike number per unit area and grain number per spike, leading to water saving and high yield. The grain yield was in the order of T4 (8333.75 kg∙hm⁻²) > T3 (8222.63 kg∙hm⁻²) > T2 (7778.17 kg∙hm⁻²) > T1 (7000.35 kg∙hm⁻²); T4, T3 and T2 treatments significantly increased production by 19.05%, 17.46% and 11.1% compared with T1 treatment, respectively. Water use efficiency and partial factor nitrogen productivity were improved. In T4 treatment, the total annual grain yield reached 19 469.7 kg∙hm⁻², which was higher than the tonnage of a grain field (15000 kg∙hm⁻²), and the output/input ratio reached 3.76. Thus, T4 was a water-saving, green, quality improving, yield increasing, and efficiency enhancing tillage model for maize and wheat in the North China Plain. Accelerating the demonstration and popularization of the technique of “deep tillage-delamination fertilization and sowing of corn, and rotary tillage-deep loosening-delamination fertilization and wide uniform seeding of wheat” in the North China Plain is thus suggested.

Effects of warming and fertilization on soil organic carbon and total nitrogen contents, and δ¹³C and δ¹⁵N in farmland

LI Jiazhen, DONG Wenxu, CHEN Tuo, HU Chunsheng

2022, 30(5): 842-850. doi: 10.12357/cjea.20220071

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Abstract:
Farmland soil is an essential terrestrial carbon and nitrogen pool that is highly sensitive to climate change. However, the response of soil carbon and nitrogen cycles to climate change remains unclear. Understanding the effect of warming on soil organic carbon is particularly important to achieving the goal of carbon peak and carbon neutralization in the context of global warming. Here, the infrared heaters were used to simulate warming and the soil temperature (5 cm depth) increased by approximately 2 °C. The soil organic carbon, total nitrogen, δ¹³C, and δ¹⁵N contents were measured to assess the effects of warming, nitrogen addition, and irrigation on the soil carbon and nitrogen cycle. The experiment consisted of four treatments: no nitrogen addition and no warming (N0T0), no nitrogen addition and warming (N0T1), nitrogen addition and no warming (N1T0), and nitrogen addition and warming (N1T1). The results showed that warming decreased the soil organic carbon content before irrigation. There were significant differences between the N1T1 and no warming (N0T0 and N1T0) treatments at 0–10 cm depth (P<0.05), and between N1T1 and the other three treatments at 10−20 cm depth (P<0.05). Warming tended to decrease soil organic carbon content after irrigation. However, the difference was not statistically significant. Warming enhanced soil δ¹³C in the nitrogen addition treatments (P<0.05) and decreased soil total nitrogen content, but the differences were only significant at the 10−20 cm depth before irrigation and at the 0–10 cm depth after irrigation (P<0.05). Soil δ¹⁵N was enhanced in the warming treatment. However, the defferences were only significant between the N0T0 and warming (N0T1 and N1T1) treatments at 0−10 cm depth before irrigation (P<0.05), between N0T1 and N1T0 at 0−10 cm depth (P<0.05), and between N1T0 and the warming (N0T1 and N1T1) treatments at 10−20 cm after irrigation (P<0.05). The soil organic carbon and total nitrogen contents decreased with increasing soil depth, while δ¹³C and δ¹⁵N increased with increasing soil depth. However, only the changes in total nitrogen and δ¹⁵N were significant. Irrigation had no significant effects on soil organic carbon, total nitrogen, δ¹³C, and δ¹⁵N. The 5-year continuous warming and nitrogen addition experiments suggest that future climate warming may accelerate the decomposition of soil organic carbon and total nitrogen, resulting in a greater loss of the light fraction carbon. Irrigation did not significantly alter the soil organic carbon and total nitrogen contents and the δ¹³C, and δ¹⁵N values in the short term; however, its long-term effects need to be further explored. In addition, future research should focus on the effect of multi-factor interactions on soil carbon and nitrogen cycles.

Runoff conditions in the Fuping Basin under an ensemble of climate change scenarios

ROMAINE Ingabire, CAO Bo, CAO Jiansheng, ZHANG Xiaolong, LIU Xia, SHEN Yanjun

2022, 30(5): 851-863. doi: 10.12357/cjea.20210725

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Abstract:
Changes in runoff are of great significance for water resources management, especially under the changing climate. In the Fuping Basin, one of the basins in the upper reaches of the Daqinghe Basin, the water resources are facing changes which show great importance of further studies on runoff conditions in the future in this basin. Hence, in this paper, MIKE11-NAM model was applied to simulate daily runoff (2008−2017) and future runoff conditions under a changing climate in the near future (2025−2054) in the Fuping Basin. After bias correction, an ensemble of four regional climate models (RCMs) was used to develop future climate data under three shared socio-economic pathways (SSP1-2.6, SSP2-4.5, and SSP5-8.5) scenarios. The obtained results showed a good performance of the MIKE11-NAM model in simulating daily runoff. R² and Nash-Sutcliffe efficiency coefficient (NSE) were 0.82 and 0.81 for calibration, 0.87 and 0.87 for validation, respectively. Although uncertainties remain, the correlation between observed and simulated RCM data was improved after bias correction for all models. Precipitation and temperature were projected to increase under all scenarios compared to the baseline period (1985−2014). Annual temperature and precipitation will increase by 2.45 ℃ and 124 mm under the SSP5-8.5 and SSP2-4.5 scenarios, respectively. However, precipitation is expected to mainly increase in summer while temperature will increase in all the seasons. The projected annual runoff will increase under SSP2-4.5 while decreasing under SSP1-2.6 and SSP5-8.5 scenarios. Seasonally, the future runoff will decrease during spring and summer under all the scenarios. Generally, the changes in runoff conditions will be more obvious in the future. Our findings can be important for integrated water resources management and planning in this region.

Applicability of the random forest model in quantifying the attribution of runoff changes

WANG Yixuan, LIU Xia, SHEN Yanjun

2022, 30(5): 864-874. doi: 10.12357/cjea.20210652

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Abstract:
Climate change and human activity have a significant impact on runoff in basins. As an important ecological barrier,the upper Yongding River Basin of has undergone significant changes in the ecological environment over the past 50 years, and the problem of water shortage has become increasingly prominent. It is necessary to restore the water ecology and analyze the influence of climate and human activities on runoff dynamics. Therefore, this study established a comparative approach between the random forest and Soil and Water Assessment Tool (SWAT) models in the Yanghe River Basin, which is greatly affected by human activities in the upper Yongding River Basin. The main conclusions were as follows: 1) in terms of the runoff simulation effect, the SWAT model was reliable for revealing the runoff dynamics in the Dongyanghe River Basin, Nanyanghe River Basin, and Yanghe River Basin. The R² values of the simulated and observed runoff in the three basins were above 0.65 in both the calibration and verification periods, and the Nash coefficients (NSE) were also above 0.65 in the three basins. However, the random forest model outperformed the SWAT model in terms of NSE and R² in the three basins, and its NSE and R² values were mostly above 0.80. 2) In quantifying the attribution of runoff changes, the results based on the SWAT model showed that the contribution rates of climate change to runoff decline in the three basins were generally between 5.0% and 15.7%, and those of human activities were 84.3%–95.0% in the three basins. The results based on the random forest model were similar to the attribution results of runoff decline based on the SWAT model; the contribution rates of climate change and human activities to runoff decline in the three basins were generally 2.4%–11.5% and 88.5%–97.6% in the three basins. This is consistent with the research results of other experts and scholars that human activities are the main cause of runoff decline in the Yanghe River Basin. Random forest can be applied in runoff simulation in the Yanghe River Basin, and the simulated model results can be used in water resource management. In this study, the SWAT model and random forest were combined to reveal the impacts of climate change and human activities on the changes in runoff in the Yanghe River Basin. Additionally, the applicability of the random forest model in the Yanghe River Basin was evaluated, which demonstrated the possibility of integrating the random forest model in hydrological modeling in further research. However, random forest is a black-box model in theory and lacks consideration of hydrological processes. Although this study preliminarily explored the method and it has been proven to be applicable in runoff simulation, the uncertainty of this method in runoff simulation or runoff evolution needs to be further explored.

2022 Vol. 30, No. 5