中国生态农业学报(中英文)

Characteristics of soil seed bank for Solanum rostratum Dunal. and its response to control with replaceable plants

ZHANG Ruihai, SONG Zhen, ZHANG Guoliang, WANG Zhonghui, FU Weidong, YIN Shuhong, ZHAI Hongkai, XI Kunpeng

2019, 27(3): 337-347. doi: 10.13930/j.cnki.cjea.180697

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Abstract:
Soil seed bank is important in the restoration and succession of vegetation in degraded ecosystems. In order to determine the characteristics of soil seed bank of the alien invasive plant Solanum rostratum Dunal. and to evaluate the effects of replacement control of S. rostratum, soil seed bank of S. rostratum in two typical habitats (riverside and farmland margin) were studied and its' vertical distribution and seasonal dynamics analyzed. In addition, a study on replacement control of S. rostratum was conducted using varieties of perennial forages of Gramineae and Leguminosea. 1) Based on the results, 23 plants species were identified, and Gramineae and Compositae were the most dominant families. The total reserve of S. rostratum seed banks in the riverside and farmland margin were respectively 347 seeds·m^-2 and 2 600 seeds·m^-2, which accounted for 2.46% and 35.16% of the whole seed bank. S. rostratum was the dominant family in farmland but another invasive plant (Cenchrus spinifex Cav.) was the main species in riverside; reaching 5 187 seeds·m^-2 and accounting for 36.70% of the seed reserve. 2) S. rostratum seeds were mainly stored in the 0-2 cm soil layer in riverside region, accounting for 64.3% and decreasing with increasing soil depth. There was no significant difference in the three soil layers of farmland margin in terms of S. rostratum seed reserve (P>0.05), which accounted for 32.7% (0-2 cm), 38.2% (2-5 cm) and 29.1% (5-10 cm) of the total seed bank. However, it was need to pay attention to potential hazards of seeds in the middle and lower layers (2-10 cm). 3) For the three times of samplings, S. rostratum seeds mainly were collected in April reached 273 seeds·m^-2 and 1 970 seeds·m^-2 in riverside and farmland margin, significantly fewer in June and August. 4) In the second year of the controlled replacement, the coverage of forage gradually increased, the resources and niches were seized by the forage, and the growth of S. rostratum significantly inhibited. The density, biomass and soil seed reserve of S. rostratum were controlled at a low level, significant lower than CK (P < 0.05). Astragalus adsurgens Pall., Festuca arundinacea Schreb., Agropyron cristatum (L.) Gaertn., combined with Leymus chinensis (Trin.) Tzvel. had the best control effect on S. rostratum. At the same time, it showed obvious economic benefits, which produced forage grass of 20 396.1 kg·hm^-2 (fresh weight) and 7 710.6 kg·hm^-2 (dry weight). 5) Soil seed reserves of S. rostratum was positively correlation with density (P < 0.01) and biomass (P < 0.05) of S. rostratum, while forage yield was negatively correlation with soil seed reserve, density and biomass of S. rostratum. However, this was not significant (P>0.05). Nevertheless, rainfall significantly affected soil seed reserve of S. rostratum (P < 0.05), which was described by the power function model y=2.619x^0.001 (R²=0.822, F=18.486, P=0.013). Therefore, plant replacement combined with physical and chemical methods can be used to establish integrated system to control S. rostratum growth in habitats such as grassland, farmland margin and wasteland.

Continual effect and mechanism of banana-sugarcane plantation on control of Fusarium wilt (Ⅱ)

LIN Weipeng, ZENG Lisha, LYU Shun, WU Chaorong, WANG Fang, ZHOU Jiankun, LIU Wenqing, CAI Kunzheng, DU Caixian, XIA Ling

2019, 27(3): 348-357. doi: 10.13930/j.cnki.cjea.180362

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Abstract:
Banana wilt caused by Fusarium oxysporum f. sp. cubense is one of the most widespread and destructive plant diseases in the world. To date, the efficient prevention and control of F. oxysporum in banana have not been found. Recently, banana-sugarcane rotation plantation (recorded in the Chinese ancient book Guangdong New Sight) has been noted to have the potential to control the disease. Furthermore, preliminary filed studies showed that the incidence of banana wilt disease reduced from 49.15% to 1.79% after two years of planting sugarcane in continuous cropped banana fields. In this study, the control effect and mechanism of banana-sugarcane rotation was investigated. Banana wilt disease incidence under various years (one, two and three years) of banana replanting after two years of sugarcane rotation were investigated. The number of soil culturable micro-organisms was measured and soil microbial community structure analyzed by high-throughput DNA sequencing technique. The results showed that banana wilt disease incidence was only 1.79% in first replanted banana field after two years of sugarcane rotation. Then it was respectively 21.93%, 25.80% and 28.81% in the second, third and fourth years of banana replantation; less than that under continuous cropping of banana fields (49.15%). The number of F. oxysporum and Actinomycetes significantly increased with increasing banana replantation years. Sequence analysis showed that Acidobacteria (32.86%), Proteobacteria (28.85%) and Chloroflexi (12.33%) constituted the dominant phyla in the banana-sugarcane rotation system. The relative abundance of bacteria of Acidobacteriales apparently increased with increasing banana replantation years and had a significant positive correlation with the incidence of banana wilt. Meanwhile, the bacteria number of Pseudomonadales, Planctomycetales, Sphaerobacterales, Lactobacillales and Solirubrobacterales apparently decreased and were significantly negatively correlated with the incidence of banana fusarium wilt. In conclusion, the control effect was still good in terms of replanting banana in less than four years after two years of sugarcane rotation. The best cultivation system was shorter rotation time, longer duration disease inhibition and higher economic efficiency, compared with other banana rotation patterns. The results showed that the inhibition of Acidobacteriales and the promotion of Pseudomonadales, Planctomycetales and Solirubrobacterales were the most important mechanisms to reduce the incidence of banana fusarium wilt under banana-sugarcane rotation systems.

Effect of long-term no-tillage with stubble on soil fertility and diversity of prokaryotic microbiome in dryland wheat soils on the Loess Plateau, China

ZHANG Guiyun, LYU Beibei, ZHANG Liping, LIU Zhen, FAN Qiaolan, WEI Mingfeng, YAO Zhong, YUAN Jiawei, CHAI Yuejin

2019, 27(3): 358-368. doi: 10.13930/j.cnki.cjea.180604

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In dryland regions, conservation tillage has the advantages of reducing soil erosion, maintaining soil structure, improving soil physical and chemical properties, and promoting microbial reproduction, compared with traditional farming methods. Up to now, the effect of long-term conservation tillage on soil prokaryotic microbial community has not been adequately reported for the China's Loess Plateau region. To understand the effects of long-term conservation tillage on soil prokaryotic microbial community diversity and soil fertility in dryland wheat fields on the Loess Plateau, the Illumina Hiseq 2500 high-throughput sequencing and physicochemical test methods were used to analyze the effects of different tillage measures on soil physical and chemical properties and the diversity of soil prokaryotic microbial community in the wheat fields in Linfen City, Shanxi Province. Tillage measures adopted in the study area for 26 years included no-tillage with stubble (NTS), no-tillage with stubble after subsoiling (SNTS) and traditional tillage (TT1). The results showed that:1) while soil contents of total nitrogen, available nitrogen, available phosphorus, available potassium, and soil water storage capacity and water content under NTS and SNTS treatments were significantly higher than those under TT1, soil pH under NTS and SNTS was lower than that under TT1. NTS and SNTS treatments reduced soil bulk density in the 0-10 cm soil layer, but increased it in 10-20 cm soil layer compared with TT1 treatment. Meanwhile, SNTS treatment significantly increased soil organic matter content. 2) The results of the Illumina Hiseq high-throughput 16S rRNA gene sequencing in area Ⅴ4 indicated that:SNTS treatment significantly reduced the relative abundance of Chloroflexi, compared with TT1 treatment. NTS treatment significantly reduced the relative abundance of Verrucomicrobia and Chloroflexi, compared with SNTS treatment. NTS treatment significantly increased the diversity of soil prokaryote community, but not significantly changed the abundance of prokaryote community. SNTS treatment not significantly changed the diversity and richness of prokaryote community. Biomarkers under NTS treatment were higher than under other treatments. The relative abundance of other prokaryotes at the phylum division was not significantly different among three treatments. 3) UPGMA analysis showed that prokaryote community structures of NTS and SNTS were significantly different from those of TT1, and the differences between NTS and SNTS were small. 4) CCA analysis showed that soil pH, contents of organic matter, available nitrogen, available phosphorus and available potassium were important for changes in genetic diversity of soil prokaryote communities. Although NTS and SNTS treatments could change soil prokaryotic microbiome structure greatly, there was still structural similarity among the soil prokaryotic microbiomes among three treatments. To sum up, long-term conservation tillage had obvious positive effects on soil microbial diversity, richness and soil fertility in dryland wheat fields on the Loess Plateau.

Correlation analysis of main environmental factors and phenolic acids in continuous tobacco cropping soils using Mantel Test

BAI Yuxiang, YANG Chengcui, SHI Puyou, JIA Meng, YANG Huanwen, XU Zhaoli, WANG Ge

2019, 27(3): 369-379. doi: 10.13930/j.cnki.cjea.180703

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Flue-cured tobacco is a crop sensitive to continuous cropping. Continuous cropping over the long-term has seriously affected growth and production quality of flue-cured tobacco by affecting the soil environment. Phenolic acids can cause growth disorders under continuous cropping. Although the interaction between phenolic acids and other environmental factors after entering the soil environment has not much been investigated, it is clear that phenolic acids occur in soils under continuous tobacco cropping. The action process and the role in limiting continuous cropping are critical for successful tobacco cultivation. An experiment was conducted to determine the relationship between phenolic acids and soil environmental factors in the soil by analyzing the correlation between various environmental factors and phenolic acids in soil. The purpose was to identify the environmental factors affecting the concentration of phenolic acids in soils under continuous cropping systems. Soils of four tobacco fields with different durations of continuous cropping (4 a, 6 a, 8 a, 14 a and 16 a) were sampled. The changes in phenolic acids, physical and chemical properties, enzyme activities and bacterial diversities in soils under different continuous cropping years of tobacco were investigaed. The correlation between phenolic acids and soil environmental factors was analyzed using the Mantel Test. The results showed that long-term continuous cropping of tobacco resulted in an increase in soil phenolic acids content. Higher pH of soil under tobacco continuous cropping resulted in low soil organic matter content, but increased available potassium. The activities of catalase, urease acid phosphatase, and invertase first increased and then later decreased. When continuous cropping for less than 6 years, bacterial community structure changed little. However, bacterial community structure changed significantly after 8 years of continuous cropping. In general, continuous cropping changed bacterial community structure and reduced community diversity. Mantel Test analysis showed that phenolic acid content was significantly correlated with enzymes activities and physical and chemical properties of soil. Bacterial abundance had the highest correlation with soil physical and chemical properties. There were differences in correlation between different phenolic acids and soil environmental factors. P-hydroxybenzoic acid and phoronic acid had the highest correlation with physical and chemical properties of soil, enzyme activity and bacterial abundance in soils. Therefore, phenolic acids in soils under continuous tobacco cropping obviously accumulated over time with deteriorated soil environment. The accumulation of phenolic acids was affected by soil physical, chemical and biological properties of soil. P-hydroxybenzoic acid and tartaric acid were two kind phenolic acids most affected.

Impact of agricultural mechanization level on farmers' cropping index in Hubei Province

PENG Jiquan, WU Haitao, SONG Jiahao, LI Mengding

2019, 27(3): 380-390. doi: 10.13930/j.cnki.cjea.180624

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Increased multi-cropping index in cultivated lands is critical for food security strategies and issues concerning in agriculture, countryside and peasant communities in China. Presently, many studies exist on multiple cropping index. However, most of these studies are based on national statistics, with fewer studies on peasant household conditions. Multiple cropping of cultivated lands is the production activities of individual rural households. Therefore, the use of macro-statistical data had failed to adequately capture inherent heterogeneities in peasant conditions in different regions. Furthermore, it has limited research analysis to only the factors that affect multiple cropping index at macro scale. This has made it difficult to accurately analyze the driving factors at micro scale. Here, we used survey data from 1 682 peasant households in Hubei Province to investigate the impact of the level of agricultural mechanization on multiple cropping index at microscopic scale. To further avoid the possibility of endogeneity and sample selection bias in the model, we used IVTobit and IVProbit regression models to explore the impact of the level of agricultural mechanization on multiple-cropping index and the differences in various types of crops. The results showed that:1) ordinary least square (OLS)-estimation result without consideration for sample selection bias and endogeneity and processed result were quite different. This indicated that the original OLS regression model significantly underestimated the effect of the level of agricultural mechanization on peasant household conditions. Regression coefficients pointed out that the level of agricultural mechanization had significant positive impact on multiple cropping index. For every 1% increase in the level of agricultural mechanization, multiple cropping index increased by 1.393%. This confirmed the hypothesis that agricultural mechanization effectively reduced the time of agricultural production, ensured seasonality of multiple crops, maximized utilization of land and increased the degree of cultivation. In addition, education and age of household head, proportion of non-agricultural income, transferred land and temperature change had dramatic negative effect on multiple cropping index of cultivated lands. Family size, number of crop varieties and type of area had significant positive effect on peasant household conditions. 2) Based on the analysis of the action mechanism of multiple cropping index of cultivated lands, there was significant difference in the impact of the level of agricultural mechanization on multiple cropping index and willingness of different types of crops. The level of agricultural mechanization affected cropping index of cash crops more than grain crops. Compared with peasants who grew food crops, those who grew cash crops were more willing to plant more with increasing level of agricultural mechanization. This was mainly because economic effects of cash crops were higher and peasants were more likely to multiply cash crops them than grain crops. The latter not only had strong seasonality, but also was not plantable in off-season periods, while the former had short growth cycle with operable production process. In summary, we argued that improvement of the level of agricultural mechanization by peasants played an active role in multiple cropping index in cultivated lands, especially for increasing cropping index of cash crops. In order to further improve the degree of cultivating land and to ensure domestic food security in peasant communities, government should vigorously promote the use of agricultural mechanization, strengthen policy support for peasants who cultivate grains in plains and reform grain storage systems.

Development of strategies for joint allocation of cultivated land and ecological land in Tianjin based on system dynamics

HAN Chengji, ZHANG Xuehua, HUA Yongsheng

2019, 27(3): 391-404. doi: 10.13930/j.cnki.cjea.180661

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Tianjin was prioritized as a functional development region in China, but its cultivated land is seriously polluted and exhausted. This study adopted complex systems modeling to develop a land allocation strategy that allows food production to be secured and land recuperated in Tianjin, where is an optimum development area in the National Main Functional Areas Planning with seriously polluted cultivated land and scarcely reserved land resources. Upon analyzing the subsystems of population, economy, and cultivated land and ecological land, a restoration model, named Tianjin System Dynamics (TSD), was developed to optimize joint allocation of cultivated land and ecological land. Validity test showed that the model had a good stability and the prediction error was < 5%. The model was then used to simulate land allocation between cultivated land and ecological land from 2016 to 2025 for Tianjin under the following strategies:inertial, in-provincial allocation, and inter-provincial allocation of cultivated land resources. The analysis showed that, with the current practice, damaged cultivated land could still be repaired, but only by 2025. Cultivated land could then still be maintained above the red line minimum, and the land ecology could still be preserved. However, food production might not be secured, as the productivity of cultivated land would be pressed to drop to the threshold. The in-provincial allocation of cultivated land resources would alleviate the pressure on cultivated land while still maintaining production above the threshold, but the ecological security of the land would be impaired, the output pressure of cultivated land still be higher than the warning threshold. In contrast, the scenario of the inter-provincial allocation of cultivated land resources could minimize land pressure to below the warning value, and improve land ecological security as a result of its flexibility. The TSD model developed optimized allocation between cultivated land and ecological land for Tianjin, and could be used for land restoration planning for other regions that are lacking in land reserve.

The role of reactive oxygen in regulating early nodulation of legumes

WANG Jin, CHEN Ping, DU Qing, ZHANG Xiaona, ZHOU Ying, REN Jianrui, WANG Tian, YONG Taiwen

2019, 27(3): 405-412. doi: 10.13930/j.cnki.cjea.180839

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Research on the production and function of reactive oxygen species (ROS) formed during early nodulation in legumes was reviewed. The ROS are highly reactive oxygen derivatives, including superoxide anion (·O₂^-), hydroxyl radical (·OH), hydroperoxyl radical (·HO₂), and hydrogen peroxide (H₂O₂). These radicals were produced during aerobic metabolism and when plants were under biotic and abiotic stresses. While toxic, these compounds serve as signalers that can trigger metabolism regulations to combat adverse environments. The ROS are produced during nodulation in legumes, induced by the nod factor (NF), to participate in infection formation, contributing to cell wall reconstruction, cross-linking of matrix glycoprotein (MGP), and actin microfilament nucleation and branching. Symbiotic production of ROS is primarily through cytoplasmic membrane NADPH respiratory burst oxidase homologue (RBOHs). Overexpression of Rboh stimulates rhizobia infection and nodule formation, resulting in increased number of symbiotic microsomes and nitrogen fixation efficiencies. Conversely, inhibition of Rboh decreases the production of ROS and down-regulates the expression of related RIPs, NIN, and ENOD2. The ROS regulate nodulation also in conjunction with Ca²⁺ through spatial and temporal alterations. In conclusion, ROS in legumes are a group of signaler molecules that function to regulate nodulation through genes expression.

Influence of climate warming and rainfall reduction on semi-arid wheat production

ZHANG Kai, WANG Runyuan, WANG Heling, ZHAO Hong, ZHAO Funian, YANG Fulin, CHEN Fei, QI Yue, LEI Jun

2019, 27(3): 413-421. doi: 10.13930/j.cnki.cjea.190031

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Infrared simulations were conducted in semi-arid Dingxi, Gansu, Northwest China to investigate the influence of climate changes that result in increased temperatures and reduced rainfalls on spring wheat production. Spring wheat was grown in one of the following six simulations formed in a factorial arrangement of three ambient temperature changes (+0℃, +1.0℃ and +2.0℃) and two rainfalls[normal (W₀) and 30% below average (W₃₀)]:0-W₀, 0-W₃₀, 1-W₀, 1-W₃₀, 2-W₀, and 2-W₃₀. Wheat yield, biomass, panicle characteristics, plant height, leaf area, chlorophyll, and net photosynthetic rate in each simulation were obtained. Decreased rainfall reduced wheat grain yield by 24.41%, 12.93%, and 27.38%, and wheat biological yield by 19.25%, 10.31%, and 22.11%, for +0℃, +1.0℃, and +2.0℃, respectively. The decreases suggested that the impact of climate warming was especially unfavorable for the economical return of wheat production. Wheat grown with decreased rainfall was lower in panicle length and weight, total spikelet number, number of grains per panicle, weight of grains per panicle, and 1000-grain weight, and higher in sterile spikelet number and spikelet sterility rate. Wheat net photosynthetic rate, leaf area, and chlorophyll content were reduced as the ambient temperature was increased and rainfall decreased. Spring wheat growth and production were severely affected when the ambient temperature increased 1℃ to 2℃ and rainfall dropped 30% in semi-arid China, suggesting that it is important to develop adaptation cropping to climate changes.

Soil nitrogen storage and recovery efficiency in double paddy fields under reduced nitrogen dose and increased crop density

XIAO Xiaoping, LI Chao, TANG Haiming, TANG Wenguang, CHENG Kaikai, GUO Lijun, WANG Ke, PAN Xiaochen

2019, 27(3): 422-430. doi: 10.13930/j.cnki.cjea.180829

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Rice production technology is transforming to natural resources-saving and environment-friendly techniques, such as straw incorporation, reduced nitrogen (N) application. Simultaneously, machine transplanted rice with high plant density has been rapidly developed with continuous reduction in rural labor and rising labor costs. Therefore, it is important to investigate N sink and use efficiency under straw incorporation, reduced N application and increased plant density for natural resources-saving and environment-friendly rice production. Five cultivation modes of machine-transplanted double-cropping rice were set up under straw incorporation in this study. The cultivation modes included zero-N and conventional density (T1), conventional N dose and density (T2), conventional N dose and increased density (T3), reduced N dose and conventional density (T4) and reduced N dose and increased density (T5). Soil N storage capacity and recovery efficiency in double cropping rice fields were analyzed under five treatments. The results showed that compared with T2 treatment, the amount of basic fertilizers of T5 treatment dropped by 20% in total N and density increased by 27.3% for both early and late rice. Total N content and storage capacity of the 0-10 cm and 10-20 cm layers of T5 were not significantly different from those of T2, but available N content of T5 decreased by 15.6% in the 0-10 cm soil layer and by 8.8% in the 10-20 cm soil layer, compared with T2. Total storage of available N was decreased by 10.7% in the 0-20 cm soil layer. Compared with T2 treatment, T5 treatment significantly reduced surplus soil N, with loss amount and loss rate of N fertilizer significantly dropping respectively by 51.7% and 15.5%. Agronomic efficiency of N in early and late rice under T5 treatment increased respectively by 33.6% and 23.0%, compared with T2 treatment. Uptake efficiency of N increased respectively by 5.9% and 6.3% and physiological efficiency of N increased by 16.3% and 3.7%, compared with T2 treatment. The results indicated that total N storage capacity of soils with reduced N and increased density under rice straw return did not significantly reduce, but alkali N storage capacity reduced significantly in the short-term. However, it had the potential to significantly reduce N loss and increase N utilization in double cropping paddy fields.

Effects of straw incorporation on crop yield and dissolved organic carbon concentration at rice growing season in rice-wheat rotation cropping system

ZHENG Jicheng, ZHANG Gang, WANG Dejian, WANG Can, CAO Zhiqiang, WANG Jun

2019, 27(3): 431-440. doi: 10.13930/j.cnki.cjea.180698

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In recent years, straw incorporation as an important way of straw utilization and culture fertility has been applied widely to achieve sustainable development of agriculture. However, straw incorporation also creates some novel problems. One of the most important of these is a large amount of crop straw returned to the field affecting the growth of rice and wheat at seeding stage. Even though lots studies reported that straw incorporation increased crop yield, there were also many reports that had a negative effect on crop yield. Another problem is that straw decomposition in rice field can produce lots of dissolved organic carbon (DOC), which has a close relationship with water eutrophication. Many studies reported the effect of straw incorporation on DOC concentration of paddy field at harvest time or on the dynamic of DOC concentration in soil incubation experiment. But little is known about effect of straw incorporation on the dynamic of DOC in rice growing season with different rate of straw returned and soil types. A two-year pot experiment was conducted to investigate the effects of straw incorporation on the yield of wheat & rice and DOC concentration in soil solution in rice growing season in two types of soil, loamy soil (L) and clay soil (C). According to the level of straw incorporated into soil, each soil type consisted of three treatments:1) 0% straw returned from previous crop to soil (S0); 2) 50% straw returned from previous crop to soil (S1); 3) 100% straw returned from previous crop to soil (S2). Compared with no straw treatment, straw incorporation significant increased rice yield in most of treatments in both soil types (1.6%-11.9%), and the yield increases of S2 treatment were higher than those of S1 treatment (no significant in first year but yes in second year). However, straw incorporation had different effects on wheat yield for two soils:in loamy soil, wheat yield increased in straw incorporation treatments in both years but only significantly in first year (7.2%-10.6%), and there was no significant difference between S1 and S2 treatments; in clay soil, wheat yield decreased significantly in straw incorporation treatments in both years (5.0%-9.3%), and the yield decrease of S2 treatment were higher than that of S1 treatment (no significant in first year but yes in second year). As to the DOC concentration in soil solution in rice growing season, compared with treatment of no straw returned, DOC concentration of S2 and S1 treatments significantly increased by 141.7% and 61.9%, respectively, and DOC of loamy soil was 89.6% higher than that of clay soil on average in the early rice growing stage, but all straw treatments and soils would decrease quickly once intermittent flooding. In conclusion, straw incorporation had a positive effect on rice yield for both loamy and clay soil, but a negative effect on wheat yield for clay soil, and also increased DOC concentration significantly. The intermittent flooding could rapidly reduce the concentration of DOC in paddy soil.

Effects of partial substitution of organic nitrogen for inorganic nitrogen in fertilization on salinity and nitrogen utilization in salinized coastal soil

ZHU Hai, YANG Jinsong, YAO Rongjiang, GAO Shan, CAO Yifan, SUN Yunpeng

2019, 27(3): 441-450. doi: 10.13930/j.cnki.cjea.180689

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Salinization reduces soil N utilization and must be controlled. The objective of this study was to evaluate the effect of application of organic and inorganic fertilizers in various combinations on soil salt content and N utilization. A series of field experiments were conducted in newly reclaimed and salinized farmland in Dongtai, Jiangsu. Maize 'Changjiangyu 8' was grown in soils receiving no fertilization (CK) or applied with one of the following combinations of fertilizers:OM1 (manure only), OM3/4 (1/4 chemical fertilizer and 3/4 manure), OM1/2 (1/2 chemical fertilizer and 1/2 manure), OM1/4 (3/4 chemical fertilizer and 1/4 manure), and OM0 (chemical fertilizer only). All combinations provided 225 kg·hm^-2 N. Soil samples were collected before sowing, during the growing stage of maize, and after maize was harvested. Samples were analyzed for salt content, pH, moisture, and inorganic N. Harvested maize plants were analyzed for N. Crop N uptake and soil N balance and use efficiency were computed. Application of manure increased soil porosity and reduced soil density and surface salt. As a result, the electric conductivity of the soil decreased, and the decrease appeared to be proportional to the rate of manure application. Soil pH was not affected. Application of manure increased soil moisture and organic matter content, and the increase was in proportion to the rate of manure application. Application of OM1/4 resulted in the highest corn N uptake, N content, and yield among all treatments. The combination was also highest in N harvest index, N recovery, N agronomy efficiency, and N partial productivity. While balance analysis showed loss of N from the soil for all treatments due to leaching, runoff, and volatilization, the loss was lowest for OM1/4. Application of combined 3/4 chemical fertilizer and 1/4 manure to provide 225 kg·hm^-2 N reduced soil salinity and resulted in the highest corn production and N efficiency. Meanwhile, it also had significant influence on the improvement of soil water holding capacity, soil structure and organic matter content.

Effect of high temperature stress at early grain-filling stage on plant morphology and grain yield of different heat-resistant varieties of wheat

FENG Bo, LI Shengdong, LI Huawei, WANG Zongshuai, ZHANG Bin, WANG Fahong, KONG Ling'an

2019, 27(3): 451-461. doi: 10.13930/j.cnki.cjea.180578

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As one of the major crops in China, wheat has direct relationship with living standard and national food security. Wheat suffers high temperature stress often at late growth period which negatively impacted wheat yield and quality. Under the steadily increasing global temperature, the frequency of high temperature stress in wheat has increased. There are many indicators used for heat resistance screening and evaluation of wheat, including chlorophyll fluorescence, cell membrane, canopy temperature, thermal index, etc, in previous researches. However, most researches were limited to laboratory analysis, and neglected yield investigation. Considering wheat as a group crop, the chlorophyll content of population canopy and NDVI were used for wheat heat-resistance evaluation in this study. The grain-filling characteristics and yield outputs were also investigated. The study aimed at providing reliable methods of breeding, and theoretical basis for cultivation of high-yielding and stress-resistant wheat varieties. In this study, the effect of high temperature stress for 3 days at early grain-filling stage on morphology and grain yield of different heat-resistant wheat varieties (lines), including heat-resistant varieties (lines) of JM22 and 056852, and heat-sensitive varieties (lines) of XM26 and GC8901, were investigated through erecting artificial greenhouse to increase on-field temperature. The highest temperature during the 3-day high temperature stress was 43.13℃ and the average temperatures in every day were respectively 10.48℃, 9.71℃ and 9.84℃ higher than that of the control. Different heat-resistance varieties (lines) varied in response of plant and grain morphologies to high temperature stress. NDVI and canopy chlorophyll content of four varieties (lines) decreased after high temperature stress. These changes of JM22 and 056852 were not significant, while NDVI values and chlorophyll contents of XM26, GC8901 significantly decreased by 9.66%, 12.10%, and 6.26%, 10.73%, respectively. High temperature stress accelerated the senescence process of wheat. The grain-filling duration were significantly shortened by 1.4 d, 0.8 d, 2.4 d and 3.0 d for JM22, 056852, XM26 and GC8901, respectively. High temperature stress significantly decreased 1000-kernel weight and grain yield of wheat. The yield reductions of heat-sensitive varieties (lines) of XM26 and GC8901 were 11.43% and 10.05%, those of heat-resistant varieties (lines) of JM22 and 056852 were 6.41% and 6.93%, respectively. In conclusion, high temperature stress at early grain-filling stage accelerated canopy chlorophyll degradation, shortened grain-filling duration, reduced grain yield of wheat. JM22 showed better heat resistant ability and yield performance. 056852 had better heat resistance ability but normal yield performance. XM26 and GC8901 were worse both in heat resistance and in grain yield.

Evaluation of factors affecting rape (swede type) yield using the projection pursuit model

TIAN Xiaoqin, LI Zhuo, LI Haojie, CHAI Jing, ZHANG Jinfang, CHEN Honglin, LIU Yonghong

2019, 27(3): 462-473. doi: 10.13930/j.cnki.cjea.181012

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Abstract:
The relative contributions of factors that affect rapeseed production were determined. A field experiment was conducted in Jianyang, Sichuan using 12 early-maturing and 38 late-maturing newly recombinant rapeseed varieties. Contributions were evaluated using the projection pursuit model based on real code deaccelerating genetic algorithm. The evaluation was compared with gray correlation analysis and principal component analysis. Effective pods in main inflorescence, effective branching position, and second effective branch number were the major contributors for early-maturing varieties, accounting for 36.79%, 24.02%, and 11.33% of the yield variation, respectively. For late-maturing varieties, seeds per silique, 1000-grain weight, and effective branching position were the most influential factors, accounting for 29.81%, 17.52%, and 14.75% of the yield variation, respectively. Interestingly, effective branching position was a significant contributor for both early- and late-maturing varieties. In addition, yield appeared to be influenced mostly by the number of effective branches and the number of effective pods, both formed during early growing stages, for early-maturing rape plants, and by seeds per silique and 1000-grain weight, formed during late growing stages, for late-maturing varieties. Predicted yields by the projection pursuit model were consistent with observed yields. Rapeseed yield was affected mostly by branching and pod formation for early-maturing varieties and by seed development for late-maturing varieties, and the yield potential was accurately predicted by the projection pursuit model.

Prediction of the evapotranspiration rate of jujube using lysimeters for drip irrigation

GUO Dandan, MA Yingjie, MA Liang

2019, 27(3): 474-483. doi: 10.13930/j.cnki.cjea.180529

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Abstract:
Measuring field evapotranspiration can provide important information needed for estimating soil moisture and crop water stress and premature drying out, and such information is essential for irrigation formulation. Evapotranspiration can be measured using large lysimeters that have the advantage of confining soil boundaries, flexible measuring intervals, and high precision. Most of studies of evapotranspiration have been done for annual crops such as wheat and maize, and the present study was conducted to measure evapotranspiration of jujubes. Jujube trees of four years were transplanted into lysimeters and evapotranspiration was measured at 30-min intervals for complete growth season. The correlation between evapotranspiration rate and leaf area index, meteorological factors, and surface soil moisture content was analyzed based on water balance and the PM formula. The daily evapotranspiration of jujube was unimodal, taking place mainly in the daytime; the contribution of was small and stable. Evapotranspiration peaked at flowering stage, reaching 4.42 mm·d^-1, and then declined gradually. The total evapotranspiration during growth season was 640.83 mm, a large proportion of which occurred during flowering and fruit development stages that accounted for 38.61% and 32.72%, respectively. The observation suggested that there is a need for flowering and fruit stages to be emphasized in irrigation of jujube trees. Hourly and daily evapotranspiration rates of jujube were different in their affecting factors. The wind speed (V) affected hourly evapotranspiration only. The most sensitive factor for evapotranspiration was canopy net radiation (R_n), followed by air temperature (T), wind speed (V), leaf area index (LAI), and surface soil moisture content (W), as summarized in the following empirical equations for hourly and daily evapotranspiration, respectively:ET₁(h)=0.153 + 0.004T+ 0.012V+0.176R_n+0.002W+ 0.067LAI, and ET₂(d)=-3.325 + 0.081T+0.163R_n + 0.069W+2.089LAI. Because canopy net radiation had the largest and most significant impact (the partial correlation coefficient was 0.562^** and 0.468^** for the hourly and daily equation, respectively), the regression was simplified as ET₁(h)=0.232 6R_n + 0.018, R²=0.719 6, and ET₂(d)=0.321 2R_n-0.141 8, R²=0.719 6. These equations were tested to be accurate and could be used to estimate the evapotranspiration rate of jujube for developing drip irrigation in arid areas when input data were complete or partially complete.

Source identification of nitrate contamination of groundwater in Yellow River Irrigation Districts using stable isotopes and Bayesian model

ZHANG Yan, ZHANG Qiuying, LI Fadong, ZHANG Xin, BI Zhilei, ZHANG Qiang

2019, 27(3): 484-493. doi: 10.13930/j.cnki.cjea.180887

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Abstract:
Nitrate (NO₃^-) pollution in groundwater has become a serious environmental problem across the world. It is very important to determine the sources of nitrogen contamination in order to prevent and control NO₃^- pollution in groundwater. This is because the intake of polluted water can increase health risk of methemoglobinemia and cancer in both aquatic lives and humans. There has been an increasing trend in NO₃^- pollution in groundwater in the Lower Yellow River Irrigation Districts. Once groundwater is polluted by NO₃^-, recovery efforts can be very daunting. The effective control and management of NO₃^- pollution require accurate identification of the actual sources of pollution. In this paper, the sources of NO₃^- in groundwater in the Lower Yellow River Irrigation District (Panzhuang Irrigation District) were identified using stable isotopes (δ¹⁵N and δ¹⁸O) and the Bayesian model. The results showed that the range of NO₃^- concentrations in groundwater in the study area was 0.1-197.0 mg·L^-1, with a mean of 34.2 mg·L^-1. About 10% of the groundwater samples had NO₃^- concentration in excess of the maximal standard of nitrate level in drinking water in China (90 mg·L^-1). Samples were divided into three depths, including 0-30 m (shallow layer), 30-60 m (middle layer) and >60 m (deep layer). The average NO₃^- concentrations in shallow groundwater layer, middle layer and deep layer were 25.9 mg·L^-1, 39.7 mg·L^-1 and 20.1 mg·L^-1, respectively. There were high NO₃^- concentrations in groundwater across Ningjin County, Wucheng County, Pingyuan County and Yucheng City. The composition of δ¹⁵N was in the range of 0.72‰-23.93‰, with an average of 11.62‰. That of δ¹⁸O was 0.49‰-22.50‰, with an average of 8.46‰. The values of δ¹⁵N and δ¹⁸O indicated that NO₃^- in groundwater in the study area mainly originated from chemical fertilizers, manure and sewage. The contributions of the four sources of NO₃^- (precipitation, chemical fertilizer, soil, manure and sewage) were quantified and estimated using the Bayesian model. The results showed that manure and sewage contributed the most to the overall NO₃^- level, with a mean NO₃^- contribution ratio of 56.2%. Chemical fertilizer was the second contributor, with a mean NO₃^- contribution ratio of 19.3%. The mean NO₃^- contribution ratio of precipitation and soil was 6.2% and 12.3%, respectively. After identification of NO₃^- pollution levels and sources, measures were required to reduce NO₃^- pollution in groundwater. Based on this study, the necessary measures included the construction of sewage pipeline and improving the utilization rate of chemical fertilizers in order to reduce NO₃^- pollution and improve water quality.

Temporal and spatial changes in pig manure load in agricultural lands in China

YU Wenmeng, SUN Xiaoxia, SU Shipeng

2019, 27(3): 494-506. doi: 10.13930/j.cnki.cjea.180709

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Abstract:
Crop-livestock and poultry farming cycle is an important way of solving agricultural non-point source pollution, promoting chemical fertilizers reduction and enhancing sustainable development of agriculture. Rational utilization of manure in agricultural lands is the basis of regional crop-livestock and poultry farming cycle. In order to control the pollution of breeding pigs through crop and pig farming cycle, we used the emission coefficient method to calculate the load intensity and carrying capacity of pig manure in agricultural lands in 31 provinces (municipalities) in China for the period 2007-2016. The spatial statistical model in ArcGIS was used to analyze temporal and spatial patterns of the evolution of pig manure load intensity in farmlands during the investigated decade. Then the multivariate linear regression model was used to explore the main driving factors of temporal and spatial differences in load intensity of pig manure in farmlands. The results showed that the load intensity of pig manure in China's agricultural lands in 2007-2016 was low, which was 4.148 t·hm^-2 averagely with obvious inter-provincial variations. The load intensity generally increased first and decreased then. There were five evolution patterns of pig manure load intensity in farmlands in 31 provinces. They were continuous upward trend in Qinghai and Tibet; down-up-up trend in Xinjiang; continuous downward trend in 4 province of Ningxia, Sichuan, Guizhou and Hebei; up-up-down trend in 12 provinces including Shanghai; up-down-down trend in 6 provinces including Chongqing; and down-up-down trend in 6 provinces including Inner Mongolia. The load intensity of pig manure in farmland showed significant spatial autocorrelation on the whole, which initially decreased and then increased during the decade. The hotpot regions of load intensity of pig manure apparently shifted to the north and west from the east and south. The multivariate linear regression analyses showed that urban-rural income ratio, crop area per capita and proportion of sections with excellent water quality had negative effects, while profit rate in the last year, annual pork consumption per capita, population density, river network density had positive effects on pig manure load intensity in farmland. These factors affected load intensity mainly through market rules, supply-demand relationship, environmental carrying capacity, livestock and poultry farming regulations and government policies. Finally, policy recommendations were put forward based on the results, such as formulating regional plans and negative list policies based on provincial shift of load intensity hotspots and carrying capacity of pig manure in farmlands, establishing cycle-coupling industries of crop farming and livestock/poultry in a certain area.

2019 Vol. 27, No. 3