中国生态农业学报(中英文)

Regulation and mechanism of greenhouse gas emissions of circular agriculture ecosystem of planting and breeding in paddy

WANG Qiangsheng

2018, 26(5): 633-642. doi: 10.13930/j.cnki.cjea.171068

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Abstract:
Rice is an important food crop in China and contributes immensely to ensuring food security, the national economy and the people's livelihood. Paddy fields make a significant fraction of greenhouse gases (GHG) emissions sources, including methane (CH₄) and nitrous oxide (N₂O). Therefore, controlling GHG emissions from rice fields is critical in mitigating global greenhouse effects. In recent years, the combination of planting and breeding in paddy has developed rapidly in China. The mode not only keeps a steady yield, increasing efficiency and promoting green development, but also changes the characteristics of GHG emissions and global warming potential (GWP) in paddy fields. Several combinations of planting and breeding in paddy (including rice-duck, rice-crayfish, rice-fish, rice-crab and rice-turtle) add niche and extend the food chain in rice paddy ecosystems. GHG emissions and GWP of the combination of planting and breeding in paddy are affected by the continuous movement and feeding activities of breeding organisms in the ecosystem with an appropriate mitigation of GHG emission. In order to provide theoretical and technical bases for GHG emissions mitigation, rice benefits increment and a healthy development of the combination of planting and breeding in paddy, this paper summarizes the characteristics of CH₄ and N₂O emissions and the effects of fertilizer and irrigation management and also explores available methods and research prospects used to reduce GHG emissions.

Effects of sowing time on agronomic characteristics and yield of quinoa

REN Yongfeng, MEI Li, YANG Yadong, WANG Zhimin, ZHAO Peiyi, GAO Yu

2018, 26(5): 643-656. doi: 10.13930/j.cnki.cjea.170852

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Abstract:
Quinoa is rich in nutrient and has a wide range of adaptability to climatic conditions. In recent years, it was successfully introduced and planted in Inner Mongolia, and the planting area was increasing year after year. There is a little rainfall in the farming-pastoral zone, however, evaporation in the region is excessive and climatic conditions highly complicated in the northern foothills of Yinshan Mountains, which limit research on the introduction and biological characteristics of quinoa. To explore the effects of sowing time on the growth and climatic conditions of quinoa in the northern foothills of Yinshan Mountains, a field experiment was conducted for the period 2014-2016. On the base of the research results of 2014-2015, in 2016, 10 different sowing times were selected (S1-S10) and the treatments divided into three sowing stages-early sowing (S1-S3 for 18-28 April), conventional sowing (S4-S7 for 3-18 May) and late sowing (S8-S10 for 23 May to 2 June). The growth, physiological and yield characteristics of quinoa were compared in all the 10 treatments. The results showed that:1) accumulated temperature of ≥ 10℃ for the whole life cycle of quinoa was 2 112-2 214℃, and growth period of quinoa was 114-150 days. 2) Early sowing treatments (S1-S3) had a longer period of vegetative and reproductive growth stages than the conventional (greater by 7.8-14.4 d) and late sowing (greater by 9.0-17.8 d) treatments. 3) Dry matter accumulation and leaf area index in treatments S1-S5 were high, with those in treatment S2 significantly higher than in conventional and late sowing treatments. 4) There was midday depression in quinoa photosynthesis at flowering stage and treatment. S2 had a significantly higher ability in terms of photosynthetic performance. Photosynthetic rate, stomatal conductance and transpiration rate of treatment S2 were respectively 3.22-6.32 μmol(CO₂)·m^-2·s^-1, 0.01-0.26 mol(H₂O)·m^-2·s^-1 and 1.52-2.51 mmol(H₂O)·m^-2·s^-1 higher than those of other treatments. 5) The highest spike grain weight (151.78 g per plant) and yield (4 097.97 kg·hm^-2) were obtained in treatment S2, which were significantly higher than in the other treatments. Yield in treatment S2 was 2.87 times higher than in treatment S9. 6) In terms of quinoa growth and yield, accumulated temperature was a more critical factor than rainfall in the study area. Accumulated temperature affected yield mainly by regulating the number of spikes and single panicle weight from grain-filling stage to maturity stage of quinoa. Therefore, early sowing was beneficial for good biological morphologic development and it increased leaf area index. Accumulated temperature during grain-filling stage of quinoa was needed for high gain yield and economic coefficient. Our results suggested that the optimum sowing time of quinoa was from mid April to early May in the northern foothills of Yinshan Mountains. Sowing time was the most important factor in quinoa production. Accumulated temperature greatly affected growth and yield formation, which required a specific attention in order to avoid low temperature conditions at later growth stages of quinoa.

Effects of water and nitrogen coupling on strawberry yield and quality under partial root-zone irrigation

DONG Shaokang, GAO Fan, GUO Jiaxuan, SHEN Yuanyue, ZHANG Yutong, ZHENG Ran

2018, 26(5): 657-667. doi: 10.13930/j.cnki.cjea.170938

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Abstract:
The effect of water and nitrogen application on efficient utilization of water and fertilizer under partial root-zone irrigation has attracted the attention of scientists around the globe. In order to improve the quality and yield of strawberry along with the utilization efficiency of water and fertilizer, this study examined the effects of integrated water and nitrogen management on the yield and quality of strawberry under partial root-zone irrigation. The main objective of the study was to provide a scientific basis for highly efficient utilization of water and fertilizer of strawberry. In the experiment, two factors (water and nitrogen) were set up with three levels for each factor. The roots of strawberry were well distributed in two zones-wetting and drying zones (A/B). The relative water content of soil was 80%±5% in the wetting zone (A). For the drying zone (B), the relative water content was in three levels, which were 20%±5% (sever water stress, SS), 35%±5% (moderate water stress, MS) and 50%±5% (light water stress, LS). At the same time, nitrogen fertilizer was set at 3 levels, which were respectively 0.50 g(N)·kg^-1 (lower N, LN), 0.75 g(N)·kg^-1 (medium N, MN) and 1.00 g(N)·kg^-1 (high N, HN). The two (A and B) zones of control (CK) were 80%±5% of soil relative water content and medium nitrogen[0.75 g(N)·kg^-1] fertilize rate (i.e., the conventional production mode). Based on the test data, the growth, quality and yield of strawberry under different water and nitrogen conditions were analyzed and evaluated using Principal Component Analysis (CPA) and polynomial fitting. The main findings of the study were as follows. 1) Due to partial root-zone irrigation, water utilization significantly dropped while water use efficiency (WUE) improved during the growth period of strawberry. The rates of irrigation water under SS, MS and LS treatments were respectively 14.77 L, 16.62 L and 18.47 L per plant. Compared with the control treatment (which was 25 L·plant-1), irrigate rates for 3 treatments dropped respectively by 40.0%, 32.5% and 25.0%. Under MSMN treatment, WUE of strawberry was 13.55 g·L^-1, 47.1% higher than that under CK treatment; but the yield change was not significant. The yield of strawberry was the highest under LSMN treatment among all treatments, which increased 4.4% over that under CK treatment. 2) The contents of Vc, soluble sugar, organic acid and sugar acid ratio of strawberry fruits under MSMN treatment were respectively 63.32%, 12.48%, 3.90% and 8.31% higher than that under CK treatment. The effects of integrated water and nitrogen management on the yield, quality and WUE of strawberry indicated that the most suitable model of water and nitrogen management for the production of strawberry was 0.75 g(N)·kg^-1 nitrogen rate with relative soil water content of 80%±5% in the wet zone and 35%±5% in the dry zone (i.e., MSMN).

Effects of nitrogen application rate on nitrogen absorption and utilization in summer maize and soil NO₃^--N content under drip fertigation

GUO Li, SHI Jianshuo, WANG Liying, LI Ruonan, REN Yanli, ZHANG Yancai

2018, 26(5): 668-676. doi: 10.13930/j.cnki.cjea.170416

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Abstract:
Inappropriate management of fertilizers is common in high-yield summer maize cultivation regions in the piedmont plain of Taihang Mountain, Hebei Province. Fertilizers overuse results not only in serious waste, but also in agricultural non-point source pollution. This study focused on appropriate nitrogen application to support high yield of summer maize under water-fertilizer integration condition. Using 'Zhengdan-958' as the test maize cultivar, four nitrogen rates (N0:no fertilizer; N1:120 kg·hm^-2; N2:240 kg·hm^-2; N3:360 kg·hm^-2 of nitrogen) were set up in 2014-2015 summer maize cultivation seasons under drip fertigation condition. The effects of different nitrogen application rates on the uptake and utilization of nitrogen in summer maize and on nitrate nitrogen content in soil were determined. The results showed that while dry matter weight and yield of maize under N0 treatment significantly decreased, there were no significant differences among N1, N2 and N3 treatments. Nitrogen content and accumulation in maize under N1 treatment significantly increased compared with that under N0 treatment. In the range of N1-N3, nitrogen content and accumulation differed among different years, which increased with increasing nitrogen application rate. However, nitrogen accumulation rate decreased gradually with increasing in nitrogen application rate. Nitrogen harvest index was the highest under N2 treatment among all treatments. Nitrogen recovery efficiency, nitrogen agronomic efficiency, nitrogen productive efficiency and nitrogen use efficiency decreased significantly with increasing nitrogen application rate. In 2014, nitrate nitrogen content under all nitrogen treatments decreased gradually in the 0-100 cm soil layer. In 2015, nitrate nitrogen content in N2 and N3 treatments reached cumulative peak in the 80-100 cm soil layers. This was related to increasing nitrate nitrogen leaching in the soil, which reach down to the 100 cm soil layer when nitrogen rate exceeded 240 kg·hm^-2 during the two years of maize cultivation. Based on the relation between N application rate and yield fitted by one variable quadratic equation, the highest maize yield needed nitrogen application rate in the range of 199-209 kg·hm^-2 and economic nitrogen application rate in the range of 174-187 kg·hm^-2. Considering the ecological environment and economic benefits, the economic nitrogen application rate was the optimal mode for summer maize under drip irrigation condition.

Effect of early winter watering on growth and water use efficiency of winter wheat

YAN Cuiping, XIAO Junhong, ZHANG Jing, PEI Xuexia, DONG Fei, ZHANG Dingyi

2018, 26(5): 677-683. doi: 10.13930/j.cnki.cjea.170710

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Abstract:
Sowing winter wheat under smashed corn straw returning using rotary machine is the main mode of winter wheat cultivation in Southwest Shanxi Province. Winter watering can compact soil, accelerate corn straw rot and ensure safe wheat over-wintering. However, less study was reported on winter watering effect under condition of smashed corn straw incorporation using rotary machine. To explore optimal management of winter watering of winter wheat under this condition for development of strong seedling before winter, improve wheat growth, thereby increase grain water use efficiency and yield, an experiment was conducted in Yaodu District of Linfen City, Shanxi Province, China, to investigate winter watering time effects on winter wheat growth. Four watering time treatments were designed-November 10, November 25, December 10 (traditional watering time used as control) and December 25. No-winter watering was set for investigation of soil properties. Tiller and roots before wintering, photosynthetic characters, yield and water use efficiency of winter wheat under different treatments were investigated. The results showed that compared with treatment of non-winter watering, winter watering compacted soil and adjusted soil bulky density, which enhanced root closely touched to the soil and soil enzymes activities, thus enriched soil nutrition level and improved tillering and secondary root growth. The winter watering treatments compensated for winter wheat growth compared with control treatment. They increased stem and secondary root numbers before winter, and increased root dry weight per plant. Under early winter watering treatments, flag leave lifespan extended, chlorophyll content increased and photosynthesis enhanced. All these resulted in final head number increase by 1.66%-5.37%, 1000-kernel weight increased by 0.55%-3.03%. For sowing winter wheat under smashed corn straw returning using rotary machine, it was found that winter wheat yield under treatment of November 25 increased by 8.40% and water use efficiency increased by 5.76% (22.05 kg·mm^-1·hm^-2) at early tillering stage. In summary, under cultivation mode of smashed corn straw returning using rotary machine, proper early winter watering (in 25 November) was beneficial for formation of strong seedlings, high yield and water use efficiency of winter wheat.

Influence of cucumber-celery intercropping on growth and fusarium wilt of cucumber

QIN Lijin, CAO Jufeng, HAN Weiqiu, YUN Xingfu

2018, 26(5): 684-692. doi: 10.13930/j.cnki.cjea.170934

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Cucumber wilt is a soil disease that is very prevalent in the production and cultivation of cucumber. The disease is highly difficult to prevent and cure. A number of studies have shown that crops intercropping was one of the most effective methods of reducing the occurrence of plant soil disease. Also celery (Apium graveolens L.) has been proved to be a plant with high allelopathy. To explore application of allelopathic effect of celery for cucumber fusarium wilt control, we conducted an experiment of celery and cucumber (Cucumis sativus L.) intercropping. In the experiment, three planting patterns were set, which were cucumber-celery intercropping, celery monoculture and cucumber monoculture. The vegetative and reproductive growths of cucumber were investigated. The allelopathic effect of soil extracts of different planting patterns on cucumber fusarium wilt were analyzed through measurement of colony diameter of Fusaium oxysporum f. sp. cucumerinum cultivated on PDA medium. Meantime, the effect of allelopathy on cucumber wilt and the disease prevention of cucumber-celery intercropping in field was studied through field inoculation of F. oxysporum. The results showed that intercropping enhanced vegetative growth of cucumber, lowered node of the first female flower bud and increased the number of female flowers blooming within the node range from one to thirty, which laid a good foundation for high yield of cucumber. The colony diameter of F. oxysporum in PAD medium with soil extracts under cucumber-celery intercropping was smallest, which was significantly different from that under monoculture of celery or cucumber (P < 0.05). There was a certain degree of inhibiting effect of ethanol, acetone, and aqueous extracts of soils under cucumber-celery intercropping on cucumber wilt. Moreover, allelopathy-inhibiting effect was 38.11%-75.90% of soil extracts under cucumber-celery intercropping. For three extract agents, colony diameter of ethanol extract was smallest, which reached a very significant level when compared respectively with acetone and distilled water (P < 0.01). Soils of different planting patterns were used to plant cucumber, cucumber fusarium wilt was inoculated during the first true leaf stage. The results showed that in soil of cucumber-celery intercropping, disease index of cucumber wilt reduced with control efficiency reaching 57.03%-72.15%. Therefore, allelopathy-inhibiting effect of cucumber-celery intercropping on cucumber wilt was obvious, which provided theoretical basis for the prevention and control of cucumber soil-borne diseases through intercropping with celery.

Comprehensive analysis of oil sunflower traits in salinized coastal soils in Hebei Province

WANG Tingting, ZHANG Xiaodong, LU Xuelin, ZHANG Guoxin, DONG Meiying, WANG Xiuping

2018, 26(5): 693-702. doi: 10.13930/j.cnki.cjea.170736

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Abstract:
Because of soil salinization, economic benefits of agricultural lands are low in saline coastal soils. It is therefore important to improve agricultural productivity of saline coastal soils. Though oil sunflower (Helianthus annuus L.) has long been considered as economic oil crop with considerable tolerance to saline-alkaline soils, salinization-driven abiotic stress is a major natural environmental factor that adversely affects oil sunflower production and quality in saline coastal soils. To select salt tolerant oil sunflower variety with optimal traits, and provide reference for salt-tolerant germplasm resources and genetic breeding of oil sunflower, we conducted a controlled chamber test for evaluation of salt tolerance at seedling stage, and a field test for comprehensive assessment of agronomic traits of oil sunflower. In the chamber test, 9 oil sunflower accessions were cultivated in saline-alkali soil and loamy soil. The saline-alkali soil was coastal saline soil with 6 g·kg^-1 salt content adjusted by using weighting method. The loamy soil was a tillage layer of farmland with salt content of 1 g·kg^-1, used as the control. The emergence rate and index were analyzed every 3 days after sowing, and plant height, leaf area, biomass weight of oil sunflower seedlings were measured after 20 days of sowing. In the field experiment, 9 oil sunflower accessions were planted in coastal saline soil with > 4 g·kg^-1 salt content. Growth stage, growth and fruit traits were investigated. Salt tolerance of different oil sunflower accessions was evaluated using the fuzzy membership function. Correlation analysis, principal component analysis and cluster analysis were used to explore properties of accessions and select suitable accessions for coastal saline soil cultivation. The results showed that while the investigated indexes of seedlings of 9 oil sunflower accessions decreased under 6 g·kg^-1 salt content soil, change degrees of 9 oil sunflower accessions were different. The fuzzy membership function analysis of salt tolerance of 9 oil sunflower accessions showed that 'Binkui 1' and 'T562' were strongly tolerant to salt stress, 'Xianrui 1' was the most sensitive to salt stress. The field experiment results showed that one trait was correlated (or extremely correlated) with at least two other traits. Growth period was extremely negatively correlated with production factors, indicating that suffering severe saline environments longer induced lower oil sunflower yield. Cluster analysis of agronomic traits divided 9 oil sunflower accessions into 3 groups. Group Ⅰ included 5 accessions which were high in oil content with medium yield and late maturity. Group Ⅱ included 3 accessions which were early maturing with medium yield and low oil content. Group Ⅲ included 1 accession with high yield, medium maturity and medium oil content. Principal component analysis showed that the three eigenvalues of cumulative variance proportions was 69%, which were growth period, yield factors and quality factors. The comprehensive score of 'Binkui 1' was highest in 9 oil sunflower accessions. Combined with the results of salt tolerance at seedling stage, comprehensive analysis suggested that 'Binkui 1' and 'T562' were excellent varieties of oil sunflower for salt tolerance breeding and cultivation in saline coastal soils.

Diagnosis of nitrogen nutrient and recommended fertilization in summer corn using leaf digital images of cellphone camera

XIA Shasha, ZHANG Cong, LI Jiazhen, LI Hongjun, ZHANG Yuming, HU Chunsheng

2018, 26(5): 703-709. doi: 10.13930/j.cnki.cjea.180304

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Abstract:
To meet requirements of food supplies and the accompanying pollution problem on environment, precision fertilization is one of the most important technologies. Soil nutrient test and crop nutrition diagnosis are essential work for precision fertilization. With the current situation of the increasing agriculture scale management, it is urgent to develop fast, nondestructive and economic techniques for the nitrogen nutrition diagnosis of crops. Digital images technology has been widely applied in nutrition diagnosis of crops. In majority of such researches, digital cameras have already been successfully used. However, few researches were reported to use cellphone cameras to study nutrition diagnosis and precision fertilization of crops. Thinking of the advantages that cellphone cameras have, such as portability, universality and handleability, the application of cellphone cameras should be detailly studied in nutrition diagnosis. In this study, we used smart cellphones to photograph corn leaves at 6-leaf and 9-leaf stages. The color parameters of corn leaves images were extracted and processed. The differences in color parameters of leaves photographs during two growth stages and for four varieties of corn were evaluated. The correlations of parameters with traditional nitrogen nutrient indexes were determined. Appropriate color parameters were selected based on statistical analysis and nutrient diagnosis model established for the color parameters and nitrogen nutrition index. Then the model was fitted to establish indicator systems of diagnosis of nitrogen nutrient and recommendations for fertilization of corns. The results showed that correlations of color parameters and nitrogen nutrient indexes at 6-leaf stage were more significant than those at 9-leaf stage, suggesting that 6-leaf stage was suitable time for diagnosis of corn nitrogen nutrient using digital image processing technique. From the analysis of leaves photographs of four corn varieties, there was no statistically significant difference among the images. Furthermore, the consequences supported two color parameters, B/(R+G+B) and G/(R+G+B) as candidates for sensitive color parameters. These two color parameters both had strong correlations with leaf SPAD and vein nitrate concentration. Also based on multivariate analysis, B/(R+G+B) was the best and was selected as sensitive color parameter for diagnosis of corn nitrogen nutrient. The diagnosis model of vein nitrate concentration was 1.73×10¹⁰×[B/(R+G+B)]^9.43. Based on the equation, nitrogen application rates under different B/(R+G+B) values were calculated for certain yield targets of corn. The results were applied to nitrogen nutrient diagnosis and recommendation of fertilization of corn. In summary, it was possible and applicable to take photographs of corn leaves at 6-leaf stage with smart cellphone, extract B/(R+G+B) color parameter and use it to diagnose nitrogen nutrition status.

Comparative study of image segmentation algorithms for rice canopy

HUANG Qiaoyi, FAN Xiaolin, ZHANG Mu, HUANG Xu, LI Ping, FU Hongting, TANG Shuanhu

2018, 26(5): 710-718. doi: 10.13930/j.cnki.cjea.170998

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Abstract:
Digital image analysis of rice canopy has widely been used for monitoring rice growth, diagnosing rice nitrogen (N) content, controlling pests and predicting rice yield. But the accuracy, stability and reliability of digital image analysis of rice canopy has greatly relied on assumed segmentation precision of rice pixels. There is current a significant progress in auto-segmentation methods for plant images captured indoor or under controlled light conditions. However, it is still hard to segment images of rice canopy taken in outdoor environments with complex and changing illumination conditions. In this paper, we proposed a segmentation method for rice canopy images taken in outdoor environment that improves the accuracy and robustness of illumination of segmentation based on multi-color spaces and support vector machine (SVM) algorithm. The rice canopy images were taken using a digital camera (NikonD90, Nikon Inc., Tokyo, Japan) in August 11st to September 25th 2016 at the largest double-season rice production area in Pearl River Delta. The camera was mounted on a tripod at 1.5 m above rice canopy with straight downward looking posture. Three typical samples taken under different illumination conditions (which changed from sunny days to cloudy days and to overcast days) were treated as test images. The training data (including rice pixels and background pixels) for modeling the support vector machine classifier was randomly picked from the test images. The color features (r, g, b, L^*, a^*, b^*, H, S, V) defined in 3 ordinarily used color spaces (RGB, CIEL^*a^*b^* and HSV) of each pixel were calculated as training data. The SVM classifiers learned from the training data with the color features from RGB, CIEL^*a^*b^*, HSV and multi-color spaces (including RGB, CIEL^*a^*b^*, HSV) were defined as rgb-SVM, lab-SVM, hsv-SVM and Multi-SVM accordingly. The accuracy and robustness of the proposed methods were examined using the test images, which were next compared with ExG&Otsu (excess green index) performance. With the help of Photoshop image editing software, the ground-truth of the rice canopy images was labeled manually and treated as the reference for segmented error calculation, including false positive rate (the rate where segmentation algorithm falsely classed background pixels as rice pixels) and false negative rate (the rate that the segmented algorithm falsely classed the rice pixels as background pixels). The results showed that rgb-SVM algorithm performed better than ExG&Otsu algorithm. While segmentation errors of rgb-SVM algorithm for the images taken on overcast days and cloudy days were respectively 5.76% and 7.74%, that of rgb-SVM algorithm for the images taken on sunny days reached 16.99%. The accuracies of lab-SVM and hsv-SVM algorithms were unstable and high under-segmentation occurred under lab-SVM and hsv-SVM algorithms for images taken on cloudy days and sunny days. Multi-SVM algorithm had the best segmentation results, which were very close to ground-truth images. Specially, segmentation error of Multi-SVM algorithm for images taken on overcast days, cloudy days and sunny days were as low as 3.11%, 3.28% and 3.95%, respectively, which were lower than that for ExG&Otsu algorithm, especially for images taken on sunny days. The results showed that the accuracy of rice canopy extraction using Multi-SVM algorithm was significantly better than that using the other methods, particularly for images taken under high illumination conditions. The Multi-SVM algorithm based on multi-color spaces and support vector machine proposed in this paper accurately segmented and extracted rice pixels in rice canopy images. It was well-suited to the changing illumination in outdoor environment, thus providing valid data support for monitoring field rice growth under natural field conditions and automated rice farming.

Responses of leaf spectral characteristics of Atractylodes macrocephala Koidz. to drought stress

XU Linyu, LIU Shouzan, BAI Yan, ZHANG Rumin, DING Heng, WU Xueqian, ZHENG Bingsong

2018, 26(5): 719-727. doi: 10.13930/j.cnki.cjea.170704

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Abstract:
Atractylodes macrocephala Koidz. is a perennial herb belonging to Compositae family, which is fond of cool climate regions. Rhizome dried for over 2 years are used for a series of medicinal functions. It is a top medicinal herb in Zhejiang Province, China. At the early stage of rhizome enlargement, A. macrocephala has a certain tolerance to mild soil drought, but excessive drought can inhibit rhizome enlargement and accumulation of constituent chemicals. Increasing degree of drought stress could slow down growth, inhibit rhizome enlargement and limit yield. In order to provide reference for drought stress control and cultivation of drought-resistant varieties, biennial A. macrocephala were planted under different drought stress. Spectral reflectance of A. macrocephala leaves determined by UniSpec-SC spectrum analyzer and combined with photosynthetic pigment contents were used to explain the response of spectral characteristics under drought stress. The results showed that spectral reflectance increased in the visible region (400-750 nm) with increasing drought stress. This indicated that the absorption and utilization ability of light energy decreased under increased drought stress. However, spectral reflectance gradually stabilized in the near-infrared band 750-1 000 nm. The reflectance of all the leaves under drought stress was lower than that of the control at 1 000 nm. The difference in spectrum of 680-750 nm was significant, which was correlated with chlorophyll content in 700-750 nm. This band could be used to monitor whether A. macrocephala was affected by drought. The contents of photosynthetic pigments increased initially and then decreased with the increased drought stress. It indicated that a suitable degree of drought was good for growth. Most of the spectral parameters were significantly correlated with pigments contents (P < 0.05). Spectral parameters of mCRI, PSNDb, red-edge position (λ_red), red-edge amplitude (D_λred) and red-edge area (S_red) were significantly correlated with leaf pigments contents (P < 0.01), which could be used to diagnose drought indicators. In summary, differential spectrum of 680-750 nm could be used to detect drought impact on A. macrocephala. Red-edge parameters, carotenoid reflectance indexes and pigment specific normalized difference may be used as indicators to diagnose drought stress degree of A. macrocephala. This conclusion not only provided a reference for the study of high-spectrum plant research, but also provided theoretical basis and technical support for the application of spectrum diagnosis of A. macrocephala in drought stress analysis.

Distribution of soil particulate organic carbon fractions as affected by tillage practices in dry farmland of the Loess Plateau of central Gansu Province

WU Jun, CAI Liqun, ZHANG Renzhi, QI Peng, ZHANG Jun

2018, 26(5): 728-736. doi: 10.13930/j.cnki.cjea.180076

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As a vital indicator of soil quality, soil organic carbon and its fractions play an essential role in soil productive capacity and crop yield, while may be affected by soil tillage methods in dry farmland areas. Organic carbon is a key component of soil because it carries many functions in agro-ecosystem. A study was carried out to investigate the effects of different tillage and straw application patterns on the distribution of soil particulate organic carbon fractions under spring wheat-pea rotation by using the density fraction method[NaI:(1.70±0.02) g·cm^-3]. Four particulate fractions of soil total organic carbon (STOC), free particulate organic carbon (FPOC), occluded particulate organic carbon (OPOC), particulate organic carbon (POC) and mineral-associated organic carbon (MOC) were obtained. The study involved a 17-year local field experiment at the Rainfed Agricultural Experimental Station of Gansu Agricultural University, Dingxi, Gansu Province, China (35°28'N, 104°44'E). The experiment included four treatments, which were conventional tillage (T), no-tillage (NT), no-tillage with straw incorporation (NTS) and conventional tillage with straw mulching (TS) arranged in a complete randomized block design with three replications. The soil samples were taken at four different soil depths (0-5 cm, 5-10 cm, 10-20 cm and 20-40 cm) per plot. The results showed that the dominant fraction of STOC for each soil layer was POC (the ratio range was 54.02%-76.78%) in four treatments, and the main component of POC was OPOC, suggesting that the effect of physical protection was the crucial role for soil carbon sequestration and fixation in the area. The contents of STOC, FPOC, OPOC and POC were decreased with increasing soil layers, MOC content, however, was increased with increasing soil layers. FPOC/STOC, OPOC/STOC and POC/STOC were decreased with increasing soil layer, MOC/STOC was increased with increasing soil layers. In 0-40 cm soil depth, compared with treatment T, the mean values of STOC, FPOC, OPOC, POC and MOC in NT, TS and NTS treatments were greater, and NTS treatment exhibited the greatest effect. The same trend was represented for FPOC/STOC and POC/STOC. No tillage system represented significantly enhance effect on contents of FPOC, OPOC, POC and MOC in 0-20 cm soil depths, but the straw retention system showed significantly boosting effect on contents of STOC, FPOC, OPOC, POC and MOC in 0-40 cm soil depths, and F test values of straw retention were greater than that of tillage system, thereby the effects of straw retention were greater than that of tillage system. As a whole, NTS may be an ideal enhancer of farmland productivity in the semi-arid soil ecosystem through enhancing soil organic carbon pool which resulted in the maintenance of higher nutrient content, and subsequently helping in contributing sustainable agricultural development in the Loess Plateau of central Gansu Province.

Effects of combined nitrogen fertilization with biochemical inhibitors on leaching characteristics of soil potassium in yellow clay soils

ZHOU Xuan, WU Lianghuan, DONG Chunhua

2018, 26(5): 737-745. doi: 10.13930/j.cnki.cjea.170766

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Abstract:
Soil nutrient leaching in yellow clay soils, especially nitrogen (N) and potassium (K) leaching, is extremely serious in South China. This has resulted in not only waste of resources and potential environmental threat, but also in serious restriction on sustainable production of crops. In this study, the effects of urease inhibitor[N-(n-butyl) thiophosphoric triamide, NBPT], nitrification inhibitor[2-chloro-6-(trichloromethyl) pyridine, CP] and their combined application on leaching characteristics of K in yellow clay soils were investigated in an indoor soil column simulation with urea (U) and urea ammonium nitrate (UAN) application. The study aimed to improve the capability of soil K through rational application of biochemical inhibitors. In the leaching solution of different N fertilizers, higher average K⁺ concentration was obtained under UAN treatments (average in 103.0 mg·kg^-1) than under U treatments (average in 93.9 mg·kg^-1), with obvious differences among inhibitor treatments. At the end of incubation (72 days after incubation), UAN treatments increased K⁺ leaching average by 6.7% more than U treatments. K⁺ accumulation in leaching solution under U treatments was in the order of U > U+NBPT > U+NBPT+CP > U+CP > CK. Compared with U treatment, U+NBPT, U+CP and U+NBPT+CP treatments reduced K⁺ accumulation by 8.7%, 20.2% and 14.9%, respectively. K⁺ accumulation under UAN treatments was in the order of UAN > UAN+NBPT > UAN+NBPT+CP > UAN+CP > CK. Compared with UAN treatment, K⁺ accumulation in UAN+NBPT, UAN+CP and UAN+NBPT+CP treatments were reduced respectively by 6.0%, 13.8% and 9.2%. Additionally, leaching rate of K⁺ across different treatments was in the order of UAN > UAN+NBPT > U > UAN+NBPT+CP > UAN+CP > U+NBPT > U+NBPT+CP > U+CP. In the middle of incubation (36 days after incubation), soil available K content of fertilizer microsites under U and UAN treatments decreased significantly. The addition of CP effectively maintained high availability of K content in the topsoil. Compared with the addition of NBPT alone, combined application of NBPT and CP reduced NO₃^- leaching, increased K⁺ fixation on soil lattice and mitigated leaching risk of K⁺ for more than 72 days in yellow clay soils. Equation models were used to describe the relationship between K⁺ accumulation (y) and NO₃^- accumulation (x) in leaching solution. The linear equation (y=ax+b) and Elovich equation (y=alnx+b) fitted well, with a and b values for inhibitor treatments obviously different. In conclusion, the application of CP alone or in combination with NBPT in yellow clay soils effectively increased the adsorption of K⁺, minimized soil K⁺ leaching loss, mitigated the risk of nutrient leaching and improved fertilizer utilization rate.

Sensitivity analysis and optimization of parameters for Laio soil moisture dynamic stochastic model for ridge-furrow rainwater harvesting system

YIN Xinwei, LI Xiaoling, WANG Qi, ZHANG Yongmei

2018, 26(5): 746-758. doi: 10.13930/j.cnki.cjea.170737

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Abstract:
Sensitivity analysis of parameters, calibration and validation of eco-hydrological models are essential for model evaluation and application. It is important in model application to accurately estimate the values of model parameters and to further improve model prediction capacity. Based on eco-hydrological process, the Laio soil moisture dynamics stochastic model (Laio model) was used to describe daily water balance in active soil depth of ridge-furrow rainwater harvest system during growing season to analyze the effects of the interactions among plants, soil and environment under different climatic conditions on soil water balance and plant water conditions. The performance of the Laio model varied with climatic zone due to the heterogeneity of climate, vegetation and soil characteristics. In this study, in order to establish an effective system for parameter sensitivity analysis, calibration and validation of the Laio model in a ridge-furrow rainwater harvesting system in a semi-arid area, a field experiment with a randomized complete block design was conducted during the 2012 and 2013 oat growing seasons at Dingxi Arid Meteorology and Ecological Environment Experimental Station. The experiment was designed to investigate the parameter sensitivity and to determine the optimal mode of parameter optimization of the Laio model under various mulching materials (common plastic film, biodegradable film mulch and manually compacted soil) and various ridge-furrow ratios (60 cm:30 cm, 60 cm:45 cm and 60 cm:60 cm). The methods included multi-factor sensitivity analysis, simplex method (ISM), particle swarm optimization algorithm (PSO) and hybrid particle swarm optimization algorithm (HPSO). Also continuously monitored soil moisture, precipitation runoff and daily precipitation data for 2012-2013 were used to run the model. The results indicated that:(1) mean precipitation per rainfall event (α) and soil saturation degree at wilting point (s_w) were the most sensitive parameters for probabilistic density function of soil moisture[p(s)] in different experimental treatments. While the sensitivity of p(s) to α was more obvious under low soil moisture content, that to s_w was more obvious under high soil moisture content. (2) There were good agreements among the results of modelling using optimized parameters of the Laio model for the three optimization algorithms (ISM, PSO and HPSO) and the observation values, which were determined from the p(s) curve. This included curve peak value (CPV), curve peak position (PP), 95% confidence interval (CI95%) and consistency measure (CM). All of these indicated that the optimized parameters of the Laio model using the ISM, PSO and HPSO methods correctly estimated p(s) of ridge-furrow rainwater harvesting. (3) The HPSO method not only improved global optimization performance, but also quickened convergence and gave robust results with good quality. It was an effective optimization method for the Laio model calibration and validation. The study improved the efficiency of model parameter calibration, upgraded the accuracy of model simulation results and provided guidance for application of the Laio model in ridge-furrow rainwater harvesting research.

Setting up policy system for eco-agriculture in China

LUO Shiming

2018, 26(5): 759-770. doi: 10.13930/j.cnki.cjea.180210

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Abstract:
The setting up of policy system for eco-agriculture in China can be divided into two tasks with one on how to practice eco-agriculture by a recommended agricultural green action list, and another on how to recognize eco-agriculture with a certification system. Eco-agricultural certification mainly observes the final results of agriculture operation and judges whether they are complied with the principle of balancing with resources, friendly for nature, well protecting environment and producing safety food. On the other hand, the recommended agricultural green action list mainly concerns about a list of actions which can be chosen from, for the regulation and control of agroecosystem structure, function, input and output during the development of eco-agriculture. The setting up of policy system for eco-agriculture should follow the approaches of firm principles, simple indicators, adaptation for local situations, easy for operation, efficient to incentive, and convenient for verification. The detail design of eco-agriculture certification system including indicator system, verification method, information exposing system, credibility record system, incentive measures and certification process, are discussed. For the agriculture green action list, the categorization system, the action description, economic support measures and the operation procedure are introduced. The paper can provide a reference for the development of eco-agriculture in China.

Concept and protection of traditional knowledges in agricultural heritage system: A case study of Pu'er Traditional Tea Agrosystem

MA Nan, MIN Qingwen, YUAN Zheng

2018, 26(5): 771-779. doi: 10.13930/j.cnki.cjea.170781

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Abstract:
Agricultural heritage systems are strongly supported by traditional knowledge, which is the experience and wisdom that local residents have accumulated during their long-term adaptation to the natural environment. By acting as structural existence in agricultural heritage systems, traditional knowledge has existed in every aspect of the lives of local residents. Thus, it plays an important and necessary role in the conservation of agricultural heritage systems. In this study, we intended to define the concept of traditional knowledge from international laws and theories. According to specific characteristics of agricultural heritage, traditional knowledge is a pact of knowledge, innovation and practice that had been accumulated in long-term agricultural production and daily lives of residents in agricultural heritage systems. It is closely related to livelihood maintenance, resource management, biodiversity conservation, spiritual belief and many other aspects. It contains traditional knowledge of livelihood maintenance, biodiversity conservation, traditional skills, folklore as well as natural resource management. Furthermore, we defined each category of traditional knowledge separately, with examples, especially the Pu'er Traditional Tea Agrosystem. We analyzed the relationship between traditional knowledge and agricultural heritage system. There were 269 pieces of traditional knowledge in the system and the unique combinations of these pieces with natural, social and cultural conditions constituted a profound connotation of Pu'er Traditional Tea Agrosystem, making it a Globally Important Agricultural Heritage System (GIAHS) site. Besides, traditional knowledge had a positive impact on agricultural heritage systems in many aspects, including maintainability, enrichment of cultural values and protection of ecological environment. We also analyzed the existing problems with the protection of traditional knowledge. In Pu'er Traditional Tea Agrosystem, the physical carrier of traditional knowledge had been damaged and the transmission of traditional knowledge was now in a great crisis. Meanwhile, tourism and foreign cultures had a negative impact on traditional knowledge in agricultural heritage systems. The protection of it lacked effective measures. To conserve traditional knowledge in agricultural heritage systems, local residents were required to enhance awareness on the protection of traditional knowledge. Local government needed to integrate the protection of traditional knowledge into agricultural heritage systems conservation. There was also the need for increased investigation, collation and classification researches on traditional knowledge in agricultural heritage systems for effective protection that was in accordance with actual on-ground conditions. Inheritance of traditional knowledge needed strengthening so that the process of gradual loss of the knowledge systems could be slowed down. Existing institutions needed to be mobilized to protect traditional knowledge in agricultural heritage systems. Through these conservation actions, we could protect traditional knowledge and agricultural heritage systems while at the same time develop our own agricultural heritage systems for generations yet to come.

Disparity between willingness to pay/accept for corn straw counter-field technology: A case study of farmer survey in Xushui District of Baoding City

ZHOU Ying, ZHOU Qingbo, GAN Shouwen, ZU Junming, DU Yanqin

2018, 26(5): 780-790. doi: 10.13930/j.cnki.cjea.170802

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Abstract:
How to reveal the real willingness of stakeholders for eco-compensation of technological practices has not only been a difficult research issue in measuring technological externalities, but also a key question in improving the accuracy and effectiveness of agricultural compensation policy. A number of studies have used ecological services value of farmland ecosystems to estimate the value of technological externality. The accuracy of the assessment results have been questioned on the basis of lacking adequate consideration of equilibrium of the relationship between participant parties. In view of this, this study first clarified the relationship between the main parties, where farmers were practitioners of production technology and environmental protection and therefore the beneficiaries of technological advancement. Therefore, the measure of technological externalities fully respected the wishes and interests of farmers. The second objective of the study was to determine research methods used in assessing the willingness of farmers. The paper used Contingent Valuation Method (CVM), which is a general intention value assessment used to determine the willingness to pay (WTP) and the willingness to accept (WTA), to determine the adoption of straw-return technology across 502 respondents. Then it estimated the maximum WTP and minimum WTA values of the mechanical costs (including:straw pulverization and rotational tillage) based on multivariate log-linear model estimation method. Based on the findings of the study, the expectancy values of WTP and WTA were respectively 38.23 ￥ and 137.52 ￥ per household per year for shredding and spinning costs of straw-return to the field, with WTA/WTP ratio of 3.6. The paper further analyzed the differences between WTP and WTA based on multiple logarithmic regression models and noted that the influencing factors of WTP and WTA asymmetry were labor force, information source, irrigation cost, mechanical cost and harvest mode. In addition, mechanical cost had a significant positive effect on the differences between WTA and WTP, while all other factors had a negative correlation. It was noted that on the one hand of the process of promoting whole-process mechanization of maize production, the increase in mechanical cost partially neutralized the beneficial effects of subsidies on farmers in the country. As a result, farmers had a low enthusiasm to return straw to the soil. On the other hand, since most corn farmers used to adopt traditional mode of production (including low labor and irrigation inputs, use of artificial harvesting and lack of information sources), the WTP of farmers for straw counter-field was also low. In fact, farmer households were even looking forward more to the government to speedily implement a reasonable subsidy policy. Thus, subsides were to be used by policy-makers to induce further adoption and reduce premiums costs on production practices. Empirical studies have confirmed that compensation standard of straw mulching technology in the northern arid area of China was 87.88 ￥ per household per year, which was reasonable and effective. In summary, the government should pay more attention on three issues in decision-making:1) establishment of a fair and effective compensation policy mechanism for farmers to work together and share the fruits of technological advancement; 2) strengthening of research on the methodology of technical-value assessment and establishment of a technical-value assessment based system for CVM and econometric models; 3) improvement of monitoring mechanism of promotion of agricultural technology and setting up information resource sharing platforms.

2018 Vol. 26, No. 5