中国生态农业学报(中英文)

Definition of agro-pastoral ecotone in North China based on irrigation corrections

GAO Huijun, LIU Jintong

2021, 29(4): 613-624. doi: 10.13930/j.cnki.cjea.200470

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Abstract:
The agro-pastoral ecotone in North China is a typical ecologically fragile zone. Scientific and reasonable definitions are important for the sustainable development of regions based on resource utilization. The water conditions are the most basic conditions to define the agro-pastoral ecotone in North China. Previous studies used precipitation as the water condition and did not consider the impact of irrigation. Based on the traditional method, this study incorporated irrigation corrections and used the corrected water condition, combined with the water variability and dryness indicators and with support of the fuzzy comprehensive evaluation method, to define the agro-pastoral ecotone in North China. Subsequently, this study also combined the administrative boundaries to divide the counties in the agro-pastoral ecotone. The results show that the agro-pastoral ecotone in North China presents a banded distribution in the northeast-southwest direction, with a total area of 659 000 km². There are 123 counties (cities, banners) in the agro-pastoral ecotone, with a total area of 660 800 km², distributed across nine provinces (autonomous regions) in North China. The number of counties is highest in the Inner Mongolia Autonomous Region, Shanxi Province, and Qinghai Province, and the total area of the counties is the largest in the Inner Mongolia Autonomous Region. The results of this study shift slightly northwest of the range designated by the Ministry of Agriculture and extend northeast and southwest, respectively, in scope. Three provinces, Heilongjiang, Jilin, and Qinghai, were added, while Liaoning Province was removed. There has been a decrease in the total number of counties. The total number of counties (cities, banners) in the agro-pastoral ecotone in Heilongjiang, Jilin, Inner Mongolia, and Qinghai increased, while the total number of counties (cities) in the agro-pastoral ecotone in Hebei, Shanxi, Shaanxi, Gansu, and Ningxia decreased. Some counties in the Inner Mongolia Hetao Irrigation District and Ningxia Hetao Irrigation District were included. Analysis of the hydrothermal conditions in the agro-pastoral ecotone show that the annual accumulated temperature in most areas is between 2000-3500 ℃, with high temperatures in the middle and low temperatures in the northeast and southwest. The water conditions (precipitation and irrigation) in most areas of the agro-pastoral ecotone are in the range of 300-450 mm, decreasing in the southeast-northwest direction. The content of topsoil organic carbon in most areas is between 0 and 1%, with low values in the middle and high values in the northeast and southwest. This study incorporates irrigation indicators into the definition index system of the agro-pastoral ecotone, which compensates for the shortcomings of the traditional climate definition method and is a scientific supplement to the definition of the agro-pastoral ecotone. The obtained county-scale agro-pastoral ecotone can provide a scientific reference to adjust the agricultural-pastoral structure for precise sustainable development of the agro-pastoral ecotone if combined with the hydrothermal conditions.

Farmer's participation consciousness and the influencing factors in the reclamation of saline-alkali land in Hetao Irrigation Region, Inner Mongolia

FU Tonggang, JIANG Guanyan, LIU Peng, GAO Hui, LIANG Hongzhu, HAN Lipu, LIU Jintong

2021, 29(4): 625-632. doi: 10.13930/j.cnki.cjea.200467

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Abstract:
Soil salinization becomes more and more serious in Hetao Irrigation Region in Inner Mongolia caused by the combined effect of climate and human activities. In such a case, lots have been done by the government. However, the participation consciousness of farmers, who play an important role in the improvement of soil salinity, is still unclear. In this study, participatory rural appraisal method was used to study the farm's cropping pattern, cropping methods, and knowledge on salinity land in Hetao Irrigation Region, Inner Mongolia. The relative perception intensity and multiple logistic regression methods were used to quantitatively analyze the farmer's participation consciousness and its influencing factors. The results showed that helianthus was the main crop which was planted by 98% of the interviewees. Besides helianthus, wheat and corn also were important crops, but these crops mainly planted in soil with less or no salinization. All the planting of helianthus was based on the flowing steps: mulching film, leaching salt and artificial seeding. Chemical fertilizer was still the main type of fertilizers rather than organic fertilizer. Flood irrigation always used to leach salt, which led to the raising of groundwater table, and in turn led to the salt accumulation in the surface soil in spring. In addition, long term application of chemical fertilizer with little organic fertilizer led to the degradation of soil structure. This indicated that the cropping and managing methods in Hetao Irrigation Region may go against the improvement of soil salinization. Fifty-four percent of the interviewees considered their land as severe soil salinization, and some of them had realized the mechanism of soil salinization. The average perception intensity of farmer on mechanism of soil salinization, the degree of salinization for their own land, and the willingness to increase cost to improving saline land were 2.82, 2.44 and 2.15, respectively. This suggested that farmers had a certain understanding of soil salinization. However, none of them had taken measure to improve their land. The maximum cost that the farmers could accept in improving soil salinity was about 750 RMB per hectare per year, which was very low compared to the cost of treatment project such as sub-drainage project. The multiple logistic regression analyses showed that the education degree was the main factor that influenced the farmer's participation sense at P < 0.05 in the influence of farmers' willing to improve saline alkali land, and P < 0.1 in the influence of farmers' understanding of saline alkali land. In addition, high cost and technical level were also important factors that had to be considered. Therefore, measures must be taken in the improving of salinity land in Hetao Irrigation Region. Firstly, the government should organize trainings on saline alkali land to farmers regularly. Secondly, interest free loans should be provided to farmers who implement the saline alkali land treatment project. Thirdly, enterprises and scientific research institutions should give fixed-point support to farmers from the implementation of the project to the later maintenance. That is to say, a mode that led by the government, cooperated by scientific research institutions, and participated by enterprises and farmers should be formed in the saline alkali land improvement in Hetao Irrigation region of Inner Mongolia. Such results can provide a scientific basis for relevant policies.

Development history, present situation, and the prospect of subsurface drainage technology in China

TAN Pan, WANG Shichao, FU Tonggang, LIU Jintong, HAN Lipu

2021, 29(4): 633-639. doi: 10.13930/j.cnki.cjea.200754

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Abstract:
Subsurface drainage technology is important for the improvement of saline-alkali land, the drainage of waterlogged areas, and the nutrient management in rice fields. In the first 20 years of this century, subsurface drainage technology developed rapidly; thus, a review of its development history and the present situation will provide a comprehensive understanding of this technology and highlight its future development. Data were obtained from the China National Knowledge Infrastructure (CNKI), Wanfang, Weipu, Baidu Academic, and Elsevier and the National Natural Science Foundation of China and Baidu Search. Statistical analysis was used to analyze the development trends, use changes, spatial distribution of application, application area, and service objects of subsurface drainage technology. The results showed that for the past 50 years, the development of China's subsurface drainage technology was divided into a preliminary exploration period (1976-1998), a gradual development period (1999-2008), and a vigorous development period (2009-2020). Jiangsu and Shandong Provinces were areas of intense research on subsurface drainage technology, and rice, wheat, corn, and cotton were the main service objects of subsurface drainage engineering in China. For saline-alkali land improvement, subsurface drainage techniques had developed rapidly, mainly for leaching soil salt. The integration of water and salt control technology and the ecological restoration of subsurface drainage represented an important direction for future development of subsurface drainage technology. With the renewal of subsurface drainage, new filter materials, and improvements to the intelligent laying efficiency of subsurface drainage construction machinery, the application of subsurface drainage technology will be more extensive.

Reclamation effect of freezing saline water irrigation in winter season on the heavy saline-alkali soil in Hetao Irrigation District

GUO Kai, LIU Xiaojing, FENG Xiaohui, JU Zhaoqiang, CHEN Huanyu, TIAN Yu, LI Jinsong, LI Weiliu, LI Jing

2021, 29(4): 640-648. doi: 10.13930/j.cnki.cjea.200465

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Abstract:
A three-year experiment of freezing saline water irrigation in winter season was conducted in a heavy saline-alkali area in Hetao Irrigation District. Two treatments, freezing saline water irrigation (FSWI) and no irrigation (CK), were implemented; the saline water irrigation amount was 180 mm with a salinity of 6.79-7.97 g·L^-1 in the FSWI treatment, and the planting crops were silage maize. This study aimed to analyze the effects of freezing saline water irrigation on the seasonal dynamics of soil water and salt and maize growth and to evaluate the reclamation effect of freezing saline water irrigation on the saline-alkali soil in Hetao Irrigation District. The results showed that, compared with CK, the FSWI treatment significantly changed the soil water, salt, and sodium adsorption ratio (SAR) dynamics in the spring. In the 0-20 cm soil layer of the FSWI treatment, till the seedling stage of maize, the mean soil water content (24.3%) were significantly higher than that under CK treatment (21.6%) in spring. The soil salt content and SAR level under FSWI treatment were significantly lower than those under CK treatment. Under FSWI treatment, the soil salt content was decreased from 33.86 g·kg^-1 before irrigation to < 5 g·kg^-1 during the seedling stage of maize, while under CK treatment, the soil salt content was kept at 34.2 g·kg^-1. The soil SAR level under FSWI treatment was decreased from 21.9 before irrigation to 9.86 during the seedling stage of maize, while it was 25 during the seedling stage under CK treatment. Plastic film mulching and subsequent rainfall in the summer maintained the higher soil water content (> 23.0%) and lower soil salinity (< 5 g·kg^-1) and lower SAR level (< 9) in the FSWI treatment. The trends for soil water, salt, and SAR in the 20-40 cm layer were similar to but not greater than those in the 0-20 cm layer. Under FSWI treatment, the emergence rate of maize was > 70%, and the biomass of maize was 9-12 t·hm^-2. Moreover, the soil salt content and SAR level in the same season decreased with increasing years of saline water irrigation. The lower soil water content, higher soil salt content, and SAR under CK treatment led to a lower emergence rate and maize biomass. Therefore, freezing saline water irrigation in winter season significantly changed the natural dynamics of soil water and salt; soil salinization decreased as salt leaching combined with a significant decrease in soil SAR and an increase in the soil water content by infiltration of meltwater which ensured normal planting and maize growth. This technology may support the reclamation of saline-alkali soil and forage grass plantation in the area.

The agronomic traits of dual-purpose sorghum and millet at the jointing stage in response to soil salinity gradients in the Hetao Irrigation District of Inner Mongolia

NI Shicun, LIANG Hongzhu, FU Tonggang, GAO Hui, HAN Lipu, LIU Jintong

2021, 29(4): 649-658. doi: 10.13930/j.cnki.cjea.210089

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Abstract:
The planting of grain-forage crops is important for the sustainable development of agriculture and animal husbandry in the Hetao Irrigation District of Inner Mongolia. In this study, two sorghum varieties ('F438' and '2562') and two millet varieties ('Zhangza 19' and 'Zhangza 13') were used as experimental materials to study the agronomic traits at the jointing stage in response to different soil salinity gradients in Wuyuan County, in Hetao Irrigation District, Inner Mongolia. Gradient analysis and correlation analysis were used to examine the relationships between the agronomic characteristics and soil electrical conductivity (EC). The results showed that the EC of soil planted millet was lower than that of soil planted sorghum at the jointing stage. With increased soil EC, the number of visible leaves of millet varieties and sorghum varieties decreased significantly, indicating that soil EC inhibited the both crops growth. A high level of soil EC significantly also inhibited the plant height and stem diameter of both crops. Furthermore, with increased soil EC, the chlorophyll content of the leaves of both crops decreased, but the chlorophyll content of sorghum was less affected by soil EC than that of millets. Correlation analysis showed that the stem diameter, plant height, leaf area, and leaves number of both crops were significantly negatively correlated with soil EC at the elongation stage. The millet variety 'Zhangza 19' had a higher tolerance to soil salinity and stronger potential adaptability for planting in saline-alkali land. This study provides a scientific basis for exploring the adaptive mechanisms of dual-purpose crops planted in saline-alkali land. This study also provides important theoretical guidance for the optimization of traditional agricultural planting patterns and the sustainable development of animal husbandry in the Hetao Irrigation District of Inner Mongolia.

Spatio-temporal distribution of net primary productivity and its driving factors in the Luanhe River Basin from 2000 to 2015

LIU Jing, TANG Feng, ZHANG Guijun, ZHANG Pengtao

2021, 29(4): 659-671. doi: 10.13930/j.cnki.cjea.200701

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Abstract:
Net primary productivity (NPP) is an important indicator of regional ecological quality and can reflect the growth status of vegetation. We selected the Luanhe River Basin as the study area, and used trend analysis, Hurst index, and residual trend analysis to examine the spatio-temporal distribution of NPP and investigated the effects of climate change, topographic factors, and human activities. This study analyzed NPP based on meteorological data, land use maps, and remote sensing data MOD17A3 from 2000 to 2015 and aimed to provide a basis for the ecological environmental governance of the river basin. The results showed that: 1) The average annual NPP was 455.04 g(C)·m^-2·a^-1, and the inter-annual variability showed overall growth from 2000 to 2015. Of the total basin area, 32.94% had a significant increase in NPP, whereas 6.98% had a significant decrease. The Hurst index analysis indicated that most NPP changes were in the same direction. 2) There were regional NPP differences in the Luanhe River Basin; the multi-year NPP average was lowest in the low hilly area, intermediate in the plain country, and highest in the middle mountain region. The maximum NPP was in Chengde and Lulong Counties in the Beijing-Tianjin-Hebei water conservation ecological function reserve, with characteristically superior natural environmental conditions. 3) The watershed NPP was positively correlated with the annual average precipitation and the annual average temperature, indicating that temperature was the main climatic factor affecting NPP in the Luanhe River Basin. The accumulation of vegetation NPP was affected by the combined effects of temperature and precipitation. Human activities affected the vegetation NPP by changing the land use intensity, ecological construction, and improving the environment, with positive and negative effects on NPP. Among the different terrain areas, the dominant factors affecting vegetation NPP varied. Overall, the prevailing reasons for NPP increases were climatic factors and human activities; only 1.74% of the regional climate and anthropogenic activities contributed to NPP reduction. The driving characteristics were similar in the low hilly area and the middle and high mountain areas. However, in the low-altitude plain areas, climatic factors or human activity alone led to more significant NPP reductions, accounting for 51.63% of the area. Taken together, this study showed that spatial distribution of NPP was determined by climatic and topographic characteristics, and climate change and human activities strongly affected vegetation NPP.

Effects of duckweed mulching on composition and diversity of weed communities in paddy fields

WANG Feng, LAI Yancen, TANG Zongxiang, ZHENG Minmin, SHI Jun, GU Maiyun, SHEN Jianying, CAO Linkui, SHA Zhimin

2021, 29(4): 672-682. doi: 10.13930/j.cnki.cjea.200581

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Abstract:
Weed control and biodiversity conservation are both required for sustainable agricultural production. As duckweeds are capable of colonizing open water surfaces in several days on account of their extremely rapid growth rate, introduction of duckweeds to paddy field is considered to inhibit weed growth as a result of shading. To acquire evidence for the utility of duckweed to control weeds and the impact on weed community composition in paddy fields, a field experiment was conducted for a rice-growing seasons. Using community ecology methods, we investigated dynamic changes of weed quantity and community diversity at 4 rice growth stages (tillering stage, booting stage, flowering stage, and maturing stage) and rice grain traits at maturing stage under three treatments: rice grown with Spirodela polyrrhiza mulching (SP), rice grown with Landoltia punctata mulching (LP), and rice grown without duckweed mulching (CK). (Landoltia punctata and Spirodela polyrrhiza were introduced into the respective plots with about 70% floodwater coverage on the day of rice transplantation.) The results showed that: ten species from seven families were recorded in weed surveys. Both duckweed species significantly suppressed weed emergence. SP and LP significantly reduced weed density by 60.3%-75.8% and 81.1%-90.4%, respectively, in the first two stages; and reduced weed biomass by more than 48.0% and 81.3%, respectively, throughout the rice-growing season. Both duckweed species changed the composition of weed communities. Cyperaceae weeds were predominant in the weed communities of the SP and LP treatments. Biomass proportions of Cyperaceae weeds were more than 62.9% and 60.2% in the weed communities of the SP and LP treatments, respectively; while the proportions of broadleaf weeds decreased significantly. Cyperaceae weeds Scirpus juncoides and Cyperus iria showed higher important values in the weed communities of the SP and LP treatments. In the weed communities of the CK, broadleaf weeds Monochoria vaginalis showed the highest important values. The Bray-Curtis similarity indice between weed communities of CK and duckweed mulching treatments was less than 0.25. Correspondingly, the weed communities of CK were separated from the weed communities of duckweed mulching treatments in UPGMA clustering. Duckweed mulching showed no negative impact on plant diversity and rice grain yields. In most rice growth stages, the Margalef index, Shannon-Wiener index, and Simpson index of weed communities under three treatments were not different significantly. Due to the mitigation of weed competition and the potential nutrients supplied by decomposition of duckweed, SP and LP significantly improved grain number per panicle by 33.7% and 15.8%, respectively, and panicle weight by 28.2% and 17.0%, respectively. Rice grain yield in the SP treatment significantly increased by 28.0%. In summary, duckweed mulching reduced weed density and biomass and altered weed community composition while maintained weed diversity in paddy fields, and Spirodela polyrrhiza mulching improved rice yield. The results demonstrated that duckweed introduction to paddy fields is an effective and eco-friendly weed management strategy which is conducive to biodiversity conservation and sustainable agricultural development.

Comprehensive footprint assessment of apple and citrus loss and waste

LI Tai, CHENG Guangyan, HUANG Jiazhang, FAN Xieyu, LU Shijun

2021, 29(4): 683-690. doi: 10.13930/j.cnki.cjea.200767

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Abstract:
In recent years, food waste has become a global research topic, and fruit loss and waste is an important component of food waste. From the place of origin to the table, fruit waste occurs during picking, post-harvest processing, storage, circulation, consumption, and other stages with varying degrees of loss. Therefore, it is necessary to study the loss and waste of the whole fruit industry in China and to analyze the impact of its resources on the environment. The purpose of this study is to provide data to reduce the loss and waste of fruit and improve the utilization efficiency of ecological resources. Using apples and citrus as examples, this study investigated all of the links in the whole fruit industry chain via questionnaires and field visits. The total amount of loss and waste was estimated, including the ecological, carbon, and water footprints using key parameters, such as greenhouse gas emissions and water waste. A field survey was conducted in the main fruit marketing area to investigate and analyze the loss and waste of fruit during production, post-harvest treatment, storage, circulation, and consumption. This included 209 workers in the entire industrial chain in the main producing area and 271 consumers in the main selling area. The results showed that the wastage rates of apples and citrus were 18.56% and 17.15%, respectively, among which the wastage rate of the circulation link was the highest, accounting for approximately one-third of the total wastage. The wastage for apples and citrus were 719.86×10⁴ t and 733.99×10⁴ t, respectively, for a total loss of 1453.85×10⁴ t. The ecological footprint of apple and citrus wastage was 13.33×10⁴ hm² and 13.76×10⁴ hm², respectively, and the total ecological footprint was 26.09×10⁴ hm². The carbon footprint was 92.37×10⁴ t (CO₂ eq) and 102.98×10⁴ t (CO₂ eq), respectively, and the total carbon footprint was 195.35×10⁴ t (CO₂ eq). The water footprint was 57.65×10⁸ m³ and 41.10×10⁸ m³, respectively, and the total water footprint was 98.75×10⁸ m³. During circulation, jolting, bumping, and squeezing could damage the fruit, resulting in loss; the highest in the entire supply chain. Bumps and squeezes during transportation were the main reasons for loss. Improper selection and temperature control by consumers during sales also caused fruit spoilage. The highest carbon emissions from production accounted for more than 90% of the carbon footprint, mainly due to the application of pesticides and fertilizers. To reduce fruit loss and waste and to improve the utilization efficiency of resources, some measures could be taken, such as improving the mechanization and standardization of fruit production levels and reducing the use of chemical fertilizers and pesticides. In the circulation process, operators must keep the environment clean and tidy. Moreover, an entirely cold-chain process should be advocated, and waste should be opposed during consumption.

Effects of green manure returning on soil microbial biomass carbon and mineralization of organic carbon in smash ridging paddy field

ZHENG Jiashun, HU Junming, WEI Xianghua, WEI Yanyan, SU Shiming, LI Tingting, XIA Xu, YU Yuefeng, ZHANG Junhui

2021, 29(4): 691-703. doi: 10.13930/j.cnki.cjea.200428

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Abstract:
Returning green manure is an important method for controlling soil adversity in modern intensive paddy fields. To evaluate the influence of smash ridging under green manure returning on soil microbial biomass carbon and carbon mineralization in paddy fields, annual field application tests of double-cropping rice were conducted with two tillage modes in early rice (smash ridging and conventional tillage), four fertilization treatments (no fertilizer, and under the same fertility conditions applying chemical fertilizer, single green manure with chemical fertilizer, and double green manure with chemical fertilizer), and chemical fertilizer application to late rice for no-tillage. The results showed that the content of soil microbial biomass carbon under single green manure returning to paddy fields can be up to two times higher than that of conventional tillage, which can effectively increase the utilization rate of soil carbon by microbes. An increase in the amount of green manure increased the soil organic carbon mineralization and mineralization potential in the smash ridging paddy field. Compared with chemical fertilizer application, the cumulative mineralization of soil organic carbon and mineralization potential of early and late rice increased by 1.6%-32.8% and 0.6%-16.6%, respectively, under single green manure returning, and 58.6%-70.9% and 29.6%-38.4%, respectively, under double green manure returning. Soil respiration intensity of late rice during no-tillage at the full heading and harvest stages was reduced by 33.4% and 38.7%, respectively, compared with conventional tillage; and reduced by 8.5%-31.4% compared with the other smash ridging treatments. The metabolic quotient in rice soil with smash ridging under single green manure returning decreased by 65.5% compared with conventional tillage. Compared with conventional tillage, smash ridging under double green manure returning and under chemical fertilizer increased by 20.3% and 159.2%, respectively; smash ridging under double green manure returning can effectively alleviate the increase in the soil metabolic quotient. There was a negative correlation between the content of microbial biomass carbon and the priming effect of organic carbon mineralization, with a correlation coefficient of 0.44 under green manure returing. There was a significant positive correlation between cumulative mineralization and the metabolic quotient, with a correlation coefficient of 0.59 under smash ridging. In conclusion, a combination of green manure returning and smash ridging can increase the content of soil microbial biomass carbon in paddy soil, reduces soil respiration intensity during the growth stages, and serves as an important technical measure for the regulation and control of soil stability and carbon fixation.

Effect of shading degree on the grain yield and photosynthetic characteristics of wheat at the grain filling stage in an almond-winter wheat intercropping system

XIE Hui, ZHANG Wen, HAN Shou'an, WANG Min, Alimujiang Aubrey, PAN Mingqi, Aiermaike Caikasimu, ZHANG Ping

2021, 29(4): 704-715. doi: 10.13930/j.cnki.cjea.200812

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Fruit tree-wheat intercropping is practiced in large parts of southern Xinjiang, a region where agroforestry intercropping is the main type of agricultural production. In the present study, a field experiment was conducted to investigate the effects of the shading degree from fruit tree canopies on the grain yield and photosynthetic characteristics of wheat at the grain filling stage. This study aimed to provide information for the selection of management standards and the optimization of the intercropping system in southern Xinjiang. In the experiment, 'Xindong 20' (Triticum aestivum L. var. Xindong 20), the main winter wheat cultivar in South Xinjiang, was used as the research object, and two treatments (heavy and light shading) were established by cutting the almond (Amygdalus communis L.) canopy of the almond-winter wheat intercropping system; delayed open-central canopy (DC) and a semicircle small-canopy (SC), respectively. Monocultured wheat was used as the control. The yield and yield components, photosynthetic pigments and soluble protein contents, light response curves, chlorophyll fluorescence induction of the flag leaves, and the canopy apparent photosynthetic rate of the intercropped wheat were investigated in three areas: near the canopy west of the almond trees, near the canopy east of the almond trees, and far from the canopy. The results indicated that the shading degree of the tree canopy was closely associated with the canopy size and the distance between the intercropping area and the tree. The daily mean values of photosynthetically active radiation (PAR) in the intercropping areas near and far from the almond canopy were 18.61% and 25.90% with DC, and 56.00% and 64.53% with SC of the natural light intensity during the wheat-filling period, respectively. The content of Chla+b and the Chla/b ratio in the wheat flag leaves were reduced in both shading treatments. When the daily mean strength of PAR was ≤56.00% of the natural light intensity, the soluble protein content in the wheat flag leaves was significantly reduced. When the daily average intensity of PAR was reduced to 25.90% and 18.61% of the natural light, the indices of optical system Ⅱ actual photosynthetic efficiency (ΦSPⅡ), photochemical quenching coefficient (qP), and maximum net photosynthetic rate (P_max) of the flag leaves, as well as the daily mean canopy photosynthetic rate (CAP) value, were significantly reduced. Under the light shading intercropping condition, when the daily mean intensity of PAR reached ≥ 64.53% of the natural light intensity, the CAP value exhibited an obvious increased (compensation phenomenon). In the almond-winter wheat intercropping system, the influence of a weak light environment caused by the tree canopy on wheat photosynthetic capacity and yield was closely related to the degree of shading. Heavy shading resulted in a significant decrease in single-leaf P_n and CAP and caused a significant decrease in yield. Under light shading conditions, the photosynthetic capacity of wheat flag leaves did not change, while CAP had a significant compensation phenomenon and no significant influence on grain yield.

Nutritional quality of japonica rice with good taste quality in an ecological rice-crab mode

MA Liang, LI Yuedong, TIAN Chunhui, ZHANG Yue, ZHANG Rui, DONG Liqiang, SUN Fuyu

2021, 29(4): 716-724. doi: 10.13930/j.cnki.cjea.200441

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Abstract:
In this study, we investigated the effects of an ecological rice-crab mode on the nutritional value of rice using two cropping patterns, ecological rice-crab (ERC) and rice monoculture (RM). Two japonica rice cultivars with good taste quality, 'Liaojing 433' and 'Wuyoudao No.4' (Daohuaxiang No.2), were selected as the study materials, and the rice contents of protein, amylose, and mineral elements, which are related to rice quality, were measured. Differences in the nutrition-related metabolites of ERC and RM were analyzed using non-targeted metabolomics. This study aimed to provide a theoretical basis for the application and popularization of the ecological rice-crab mode. The results showed that compared with RM, the protein content of brown rice of 'Liaojing 433' and 'Wuyoudao No.4' under the ERC mode significantly decreased by 6.75% and 10.11%, respectively, and Pb content decreased by 35.11% and 44.35%, respectively. The Fe content significantly increased by 1.03 and 3.99 times, respectively, and the Se content increased by 2.11 and 4.74 times, respectively. Two hundred and thirty-three metabolites were detected by gas chromatography-mass spectrometry (GC-MS). Significant differences in the metabolites were found between ERC and RM brown rice by partial least-squares discriminant analysis (PLS-DA). Compared with RM, the content of 4-aminobutyric acid in 'Liaojing 433' and 'Wuyoudao No.4' under the ERC mode increased significantly by 1.11 and 10.99 times, respectively; and the contents of antioxidant substances, such as alpha-tocopherol, beta-hydroxamic acid, and quinic acid, significantly increased by 0.62 and 1.22 times, 11.64 and 19.48 times, and 13.25 and 3.67 times, respectively. The hexitol content increased by 13.36 and 14.14 times, respectively, and the galactitol content increased by 2.13 and 1.87 times, respectively. Rice yield of 'Liaojing 433' under the ERC mode decreased by 286.0 kg·km^-2, whereas that of 'Wuyoudao No.4' under the ERC mode increased by 344.5 kg·km^-2. However, there were no significant differences in rice yield between ERC and RM. In conclusion, the ERC mode can increase the nutritional value of high-quality japonica rice without reducing its production.

Lodging characteristics after physiological maturity of spring maize sowed at different dates and its influencing factors

ZHANG Dongmei, YANG Ke, JIANG Chunxia, ZHANG Wei, HUANG Mingjing, LIU Huatao, YAN Liuying, LIU Enke, ZHAI Guangqian, WANG Juanling

2021, 29(4): 725-737. doi: 10.13930/j.cnki.cjea.200593

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Abstract:
In the middle-south of Shanxi Province, light and heat resources are abundant leading to a wide range of sowing date for spring maize. A suitable sowing date should achieve high yield and lodging resistance by adapting to the regional meteorological and production characteristics. Therefore sowing date adjustment is an important issue in the popularization and application of mechanical grain harvesting technology for spring maize in this region. A field experiment was conducted in Dongyang Experiment and Demonstration Base of Shanxi Academy of Agricultural Sciences in 2019, consisting of 2 maize cultivars ('JKY3306' and 'ZD88') and 5 sowing date (April 16, April 23, April 30, May 7 and May 30). 'JKY3306' is a screened out cultivar with high yield and suitable for high population and mechanical grain harvesting; while 'ZD88' is a local cultivar. The results showed that lodging rates after physiological maturity of 'JKY3306' at different sowing dates had no significant difference. And lodging rates at the last four sowing dates was always 0. However, the lodging rate after physiological maturity of 'ZD88' increased significantly with the delay of sowing date (P < 0.05). According to the fitting equation, the lodging rate of 'ZD88' sowed at April 30, May 7 and May 14 was respectively increased by 1.3, 2.4 and 3.2 percentage points for every 10 days during grain dehydration period. Through the analysis of influencing factors on lodging resistance, the length of the third and fourth internode, the coefficient of ear height and the gravity center height could be used as the negative effect indexes to evaluate the lodging resistance. And the dry weight per unit length of the fourth internode, the bending strength of the third internode and the wet weight per unit length of the third internode could be used as the positive effect indexes. With the delay of sowing date, the biological yield and economic yield of the two varieties increased significantly at first and then decreased. Spring maize sowed around April 30 can achieve high yield and lodging resistance in this region. Therefore, April 30 is a suitable sowing date to popularize mechanical grain harvesting technology in spring production.

Selection and realization of hybrid breeding progeny of Japonica rice in cold region based on pressure-state-response model

LIU Baohai, NIE Shoujun, GAO Shiwei, LIU Qing, LIU Yuqiang, CHANG Huilin, MA Cheng, TANG Ming, XUE Yinghui, BAI Rui

2021, 29(4): 738-750. doi: 10.13930/j.cnki.cjea.200776

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Abstract:
To improve the breeding of hybrid offspring, a stress-state-response (PSR) model was used to investigate the genetic, environmental, and selection factors affecting the progeny of japonica hybrid rice in cold regions. A conceptual model and evaluation system for the selection of progeny of japonica hybrid breeding in cold regions with 1 target, 3 criteria, and 18 indices was constructed, and the objective entropy weight and efficacy score were used to evaluate the comprehensive index. The results indicated that nine generations of hybrid offspring of 'Suijing 18' crossbreeding showed the highest weight of neck blast, followed by lodging level, and the lowest was seed setting rate. The indices of resistance to panicle blast, lodging level, and percentage of empty shell were the most important factors for selecting hybrid progenies in cold regions. In the PSR system evaluations, the order of influence was the response subsystem (0.6867) > the state subsystem (0.2651) > the pressure subsystem (0.0482). Meanwhile, the coefficient of variation of the index values ranged from 0 to 200.4%, which was beneficial for enhancing the breeding efficiency of progeny selection through a wide range of variation. The response, stress, and state subsystems were related. Dynamic changes in the environmental pressure conditions represented an important factor to promote changes in the response and state subsystems. The weight analysis of hybrid progeny showed that the order of influence of environmental pressure was neck blast > irrigation water temperature > planting density > fertilizer application. Compared with the current plant-type improvement theory and methods for hybrid offspring character selection, applying the PSR hybrid progeny selection theory and methods on rice breeding in cold regions effectively overcame the problems of multi-optimal trait aggregation, identification, and low selection efficiency due to the lack of breeding experience, qualitative and quantitative combinations, more emphasis on trait selection, and poor response decision making. Systematic, dynamic, and objective scientific planning, with accurate and efficient design, evaluation, and decision-making was realized by PSR, which was concise, practical, efficient, and operational. According to the ecological characteristics of rice farming in cold regions, the variety selection based on natural conditions in different regions differed. The state and response indices in the evaluation system should be adjusted when the theory and method presented here are used to select the hybrid offspring of rice. These principles and methods can also be used in soybean, corn, and other crops, all of which require further exploration. The results of this study provide a useful reference and technical basis for accelerating the breeding of new rice varieties with high quality, high yield, multi-resistance, and wide adaptability in cold regions.

Characteristic analysis of lodging rice and study of the multi-spectral remote sensing extraction method

LU Zhou, XU Feifei, LUO Ming, LIANG Shuang, ZHAO Chen, FENG Xianfeng

2021, 29(4): 751-761. doi: 10.13930/j.cnki.cjea.200553

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Abstract:
Crop lodging assessment is essential for evaluating yield damage and informing crop management decisions for sustainable agricultural production. Traditional evaluation methods and manual on-site measurements are time-consuming and labor- and capital-intensive. In this study, a remote sensing model to distinguish lodging rice was constructed based on spectral and textural features. To accurately extract the area of lodging rice from high-resolution remote sensing images, this study used Sentinel-2 multispectral images taken on September 27, 2019, to study the spectral and textural characteristics of lodging rice, in Tongjiang City, Heilongjiang Province. Analysis of the surface reflectance of normal rice and lodged rice, showed that reflectance of eight bands, including visible light, near-infrared, and shortwave infrared, increased after rice lodging; the reflectance of shortwave infrared, red light, and red edge 1 increased by more than 0.06. Except for the difference vegetation index (DVI), the typical vegetation indices of lodged rice, such as normalized difference vegetation index (NDVI), ratio vegetation index (RVI), enhanced vegetation index (EVI), and red edge position index (REP), decreased. There were significant differences between lodging rice and normal rice in the mean texture feature values of the red band, red edge 1, and shortwave infrared; the largest difference was for the mean texture value of the red band. Therefore, in this study, normalized difference vegetation index, land surface water index (LSWI), ratio vegetation index, difference vegetation index, and texture mean of the red band were used to construct the decision tree classification model. The results of remote sensing monitoring showed that rice lodging on the farm was decentralized. The area of rice disaster was larger in the west and south and smaller in the north. There was no lodging rice in the middle of the north and the east. Compared with the measured area, the area recognition errors of normal and lodged rice were 3.33% and 2.23%, respectively. When using random verification samples and model verification results for the confusion matrix analysis, the user accuracy and mapping accuracy of lodging rice were 92.0%, and the Kappa coefficient was 0.93. These results show that this method can be applied to remote sensing data from lodged rice in large areas and can provide a relevant basis for the investigation of rice lodging areas using high-resolution and multi-spectral remote sensing data.

Dynamic of ionic absorption and salt tolerance screening in wheat seedling under salt stress

DONG Hongtu, XIE Chaojie, HOU Peichen, LI Aixue, WANG Xiaodong

2021, 29(4): 762-770. doi: 10.13930/j.cnki.cjea.200664

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Abstract:
Salt tolerance evaluation is the basis of wheat introduction, screening, and breeding. Salt stress damages plants mainly through osmotic stress, ion toxicity, and other processes. In this study, salt-sensitive varieties 'Liaochun10' and 'Jing411', moderately salt-tolerant breeding material 3D232, and highly salt-tolerant varieties 'DK961' and 'Xuezao' of common wheat were used to analyze ion absorption, growth, and ion concentrations in seedlings under salt concentrations of 0 mmol·L^-1 (CK) and 250 mmol·L^-1 sodium chloride (NaCl). The ion flux and direction of potassium (K⁺), sodium (Na⁺), and chlorine (Cl^-) around the roots of five wheat lines with different salt tolerances were measured by applying dynamic ion detection techniques. The relationship between ion flux and wheat salt tolerance was established by studying the mechanism of wheat salt tolerance, which provided a scientific basis for the rapid selection of salt-tolerant varieties using dynamic ion detection technology. The main results were: 1) the detection of dynamic flux demonstrated that the circulation of K⁺ changed from influx to efflux in the salt-sensitive wheat varieties ('Liaochun10' and 'Jing411') under salt treatment, whereas in the medium salt-tolerant variety (3D232), the efflux of K⁺ decreased. For the salt-resistant varieties, K⁺ efflux changed to influx ('Xuezao') or maintained K⁺ influx ('DK961'). Na⁺ efflux increased after stress, and the velocity range changed from 23-47 pmol·cm^-2·s^-1 to 61-150 pmol·cm^-2·s^-1. Compared with Na⁺, the Cl^- efflux increased, and 'Liaochun10' showed the largest change; the efflux was 10 times higher than that under CK. Na⁺ and Cl^- efflux were not significantly correlated with salt tolerance. 2) Under salt stress, the root-seedling ratio of salt-sensitive wheat decreased, whereas that of salt-tolerant and mid-salt-tolerant wheat increased. The fresh weight of salt-sensitive wheat decreased significantly compared to CK, but the changes in salt-tolerant and mid-salt-tolerant wheat were not significant. 3) After salt stress, the content of K⁺ in the roots and shoots of salt-tolerant and mid-salt-tolerant wheat increased by 57%-88% and 18%-112%, respectively, whereas in salt-sensitive wheat, it decreased by 40%-44% and 24%-42%, respectively. However, the Na⁺ increase in the shoots of salt-tolerant wheat was less than that of salt-sensitive wheat, and more Na⁺ was blocked in the roots. Salt-tolerant wheat was better able to separate Na⁺. 4) Under salt stress, the K⁺ flux was highly correlated with changes in the root-seedling ratio and the rate change of fresh weight, with correlation coefficients of 0.972 and 0.832, respectively. In conclusion, under high salt environments, salt-tolerant lines have a stronger ability to protect K⁺, but K⁺ can also be protected by regional Na⁺ application and salt rejection mechanisms to enhance salt tolerance. The results of this study showed that K⁺ flux in the mature zone of wheat roots can be used as a biomarker for wheat salt tolerance screening after 24 h of 250 mmol·L^-1 NaCl stress.

2021 Vol. 29, No. 4