中国生态农业学报(中英文)

Space-time evolution of China's agricultural ammonia emission and emission reduction potential

DENG Mingjun, LUO Wenbing

2018, 26(9): 1257-1268. doi: 10.13930/j.cnki.cjea.180016

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Abstract:
The causes of haze in China are more complicated than those in developed countries. Artificial ammonia (NH₃) pollution is an important factor driving the continuous increase in PM_2.5 index in China, but so widely ignored by the entire society. Existing research shows that artificial NH₃ emission come mainly from agriculture. Thus, agricultural NH₃ emission reduction is the most economic and effective method of haze governance. Therefore, research on agricultural NH₃ emission reduction potential has significant practical significance for the governance of haze in China. Based on the related data (statistical yearbook and research results), referred to as "Technical Guidelines for Preparation of Atmospheric Ammonia Emission Inventory (for Trial Implementation)", we built an analytical model of agricultural NH₃ emission reduction potential, calculated and analyzed temporal evolution of China's agricultural NH₃ emission for the period from 2004 to 2013 and the reduction potential of agricultural NH₃ emission for the period from 2020 to 2030 using emission factor method and scenario analysis. The results showed that:1) total agricultural NH₃ emission was 11.939 2 million tons in 2013, up 18.59% compared to 2004. 2) The provinces and cities where total amount of agricultural NH₃ emission was 0.6 million t·a^-1 or more in 2004 were Henan, Shandong, Hebei and Inner Mongolia provinces. By 2013, this had expanded to six provinces-Henan, Inner Mongolia, Hebei, Shandong, Xinjiang and Sichuan. 3) Under business-as-usual (BAU) scenario, China's agricultural NH₃ emissions in 2020, 2025 and 2030 increased by 15.26%, 23.60% and 30.23%, respectively, over that in 2013. 4) Under abatement scenario, China's agricultural NH₃ emissions in 2020, 2025 and 2030 reduced by 3.194 million tons, 5.013 million tons and 6.604 million tons, respectively, compared with BAU scenario, which were respectively 11.49%, 18.39%, and 25.08% lower than the 2013 levels. 5) For the future, the key to China's agricultural NH₃ emission reduction depended on the quantity and consumption structure of China's household consumption of livestock and poultry products. Next, it depended on the changes in feed nutrient levels in China's livestock and poultry farming. 6) The key potential agricultural NH₃ emission reduction provinces were Henan, Shandong, Hebei, Inner Mongolia and Sichuan. Thus for future control of China's agricultural NH₃ emissions under BAU scenario, the implementation of China's agricultural NH₃ emissions reduction must be done by vigorously cutting down emissions in key areas and accelerating the transformation of consumer behavior in livestock and poultry products.

Spatial dynamics of agricultural carbon emissions in China and the related driving factors

HE Yanqiu, CHEN Rou, WU Haoyue, XU Jie, SONG Yi

2018, 26(9): 1269-1282. doi: 10.13930/j.cnki.cjea.171097

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Abstract:
The reduction of carbon emission in agricultural lands is not only important in sustainable agriculture, but also inevitable for China to achieve an overall emission reduction targets and carbon emission control. It is also of great significance to conduct research into the spatial distribution and the driving factors of carbon emissions in agricultural lands in China. Studies that have focused on regional distributions of carbon emissions in agricultural lands adopted different measurement methods and used inconsistent driving indicators, therefore had reached different conclusions in different researches. Moreover, in order to compensate for the deficiency with static analysis methods in dealing with dynamic effects, we combined dynamic grey correlation method with regression model. It not only analyzed the non-linear impacts of carbon emission in agricultural lands and the influencing factors, but also analyzed the dynamic impacts of carbon emission in agricultural lands and the influencing factors. Based on the preceding researches, our study started by analyzing the spatial distribution of carbon emissions in agricultural lands in China, including total amount of carbon emission, carbon emission intensity, carbon emission structure and carbon emission level in agricultural lands. It then discussed in detail the causes of the spatial patterns of inter-provincial carbon emissions in agricultural lands and quantitative relationship between the influencing factors and spatial distribution. The study was a critical source of reference on zonal carbon emission reduction that could be useful in formulating carbon emission policies in China. The main conclusions of this paper were as follows:inter-provincial differences in carbon emission intensities in agricultural lands had increased with time. There was no significant reduction in structural differences in carbon emission among provinces or cities. The polarization of carbon emission level in agricultural lands was ever more severe. The level of carbon emissions in agricultural lands fell in the central region, but increased in the west. In contrast, farmland utilization and mechanization of agricultural production were more important factors driving carbon emission in agricultural lands. Some achievements were made in reducing ruminant emissions, with a widening gap among provinces or cities due to differences in agro-economic level, agricultural mechanization, agricultural structure and agro-human capital. The differences in inter-provincial carbon emissions of agricultural lands increased. Agriculture and animal husbandry, farmland utilization and mechanization of agricultural production technology were the leading factors driving the improvement in carbon emission in agricultural lands in most of the provinces and cities with more attention on agricultural development. In these regions, the development of superior industries, ruminant feeding and agricultural production techniques (human capital) were the dominant factors reducing carbon emissions. Finally, we forwarded three recommendations:First, there was need to focus on long-term carbon emission reduction in farmlands. Specifically, major grain-producing areas were to strengthen innovation of emission reduction technology and push forward with progress in emission reduction projects. Second, there was need for further attention on promoting technology of emission reduction in feeding ruminants and in exploring agricultural development models that combined farming with breeding, especially in pastoral areas. Third, there was need to fully exert the role of agro-economic structure in reducing carbon emission. The eastern, central and western regions were to adjust industrial structure in accordance with the level of development.

Greenhouse gases emission under different cropping systems in the Jianghan Plain based on DNDC model

ZOU Fengliang, CAO Cougui, MA Jianyong, LI Chengfang, CAI Mingli, WANG Jinping, SUN Zichuan, JIANG Yang

2018, 26(9): 1291-1301. doi: 10.13930/j.cnki.cjea.180634

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Abstract:
Increased greenhouse gases emission contributes to global warming. Paddy field is considered to be one of the main sources of greenhouse gas CH₄ and N₂O emissions. The rice planting area in the Jianghan Plain is about 8×10⁵ hm², accounting for about 40% of the total rice planting area in Hubei Province. Studies on characteristics of greenhouse gases emission in the Jianghan Plain are important for evaluation and reduction of regional greenhouse gases emission. So far, several models, such as DNDC model, have been used for simulating the greenhouse gases emission, which in conjunction with ArcGIS may be used for simulating the regional greenhouse gas emission. In this study, we used DNDC model to simulate the greenhouse gases emission in the Jianghan Plain. The field experiment was carried out for investigating the characteristics of CH₄ and N₂O emissions under rice-wheat (RW), rice-rape (RR) and rice-fallow (RF) cropping systems. Meteorologic, soil, crop and field management data were obtained for DNDC-stimulating CH₄ and N₂O emissions under different cropping systems in the Jianghan Plain. The results of field experiment showed that the CH₄ fluxes were from -2.80 mg·m^-2·h^-1 to 55.64 mg·m^-2·h^-1, and the N₂O fluxes were from 0 to 1.90 mg·m^-2·h^-1 in the Jianghan Plain. CH₄ emission was mainly concentrated in rice season, and the peaks occurred at rice heading and tillering stages. N₂O emission in rice season was higher than in non-rice season. And the peaks occurred after wheat or rape sowing in non-rice season and during field drying period in rice season. CH₄ emission under RW and RR systems were significantly higher than that under RF system, while N₂O emission was significantly higher under RF system than under RW and RR systems. The DNDC model stimulating results were verified by comparing the observed values with the stimulated values. The R² and RAE between the observed and the stimulated values under different cropping systems were form 0.85 to 0.98 and from 8.29% to 16.42%, respectively. The high R² and the low RAE suggested that the stimulated values of CH₄ and N₂O emissions with DNDC model were in good agreement with the observed values. According to the simulation results, the annual emissions of CH₄ and N₂O were 0.292 9 Tg C and 0.009 2 Tg N in the Jianghan Plain from 2010 to 2016, respectively. For different crop systems, CH₄ and N₂O emissions were presented as RW > RR > RF and RW > RF > RR, respectively, and the global warming potential (GWP) was RW > RR > RF. The CH₄ and N₂O emissions were also different for different regions. The annual average CH₄ emission from 2010 to 2016 was in the order of Jianli > Jingmen > Gong'an > Tianmen > Xiantao > Honghu > Songzi > Hanchuan > Qianjiang > Shishou > Jingzhou > Jiangling > Chibi > Jiayu. And the annual average N₂O emission from 2010 to 2016 was in the order of Jianli > Jingmen > Gong'an > Honghu > Xiantao > Tianmen > Hanchuan > Qianjiang > Songzi > Jingzhou > Jiangling > Chibi > Shishou > Jiayu. The results of our study indicated that the DNDC model could preferably stimulate the greenhouse gases emissions in the Jianghan Plain. And RR and RF could reduce CH₄ and N₂O emissions compared with RW.

Spatio-temporal patterns of typical agro-meteorological disasters in China in the past 30 years

SANG Jing, HAO Lu

2018, 26(9): 1302-1314. doi: 10.13930/j.cnki.cjea.170697

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Abstract:
Even though China, like any other country, is vulnerable to the adverse effects of climate change, agriculture is a vital industry in the country. In the context of global warming and frequent extreme weather and climate events, agricultural production in China has been affected by the increasingly severe meteorological disasters. It is very important to study the spatio-temporal patterns of agro-meteorological disasters in China in order to mitigate disaster risks and reduce disaster losses. In this paper, the spatial and temporal changes and the typical patterns of main meteorological disasters (i.e., drought, flood, low-temperature and hailstorm disasters) affecting agriculture in China from 1978 to 2013 were analyzed using Empirical Orthogonal Function (EOF) method. The results showed that drought (starting in 2000), hailstorm (beginning in 2001) and low temperature (starting in 2008) all decreased in trend. However, there was no obvious trend in flooding. The EOFs of drought that caused 10% and 30% yield losses were similar, and the losses in the North were obviously higher than those in the South. The EOFs of flood that caused 10% and 30% yield loss were quite different. Flood area with 30% yield loss was mainly distributed in the Yangtze River Basin and the Northeast. However, flood area with 10% yield loss was widely distributed throughout the country. The low temperature disaster in the northern area was more severe than in the southern area. Hailstorm in the western area and the northern area was much serious. Droughts and floods did not affect the northeastern plain throughout the year, but caused serious yield losses. Low temperature disaster persistently affected most areas of China, but with little serious losses. Hailstorm caused persistent and serious losses. Combined with statistical and EOFs analyses, we found that the spatial and temporal patterns and the dynamics of the four disasters with 10% and 30% yield loss were not consistent in disaster degree, affected areas and disaster duration.

Comparative study on two evaluating methods of ecosystem services at city-scale

LIU Shiliang, ZHAO Shuang, CHENG Fangyan, HOU Xiaoyun, JIA Kejing, QI Fan, YANG Feng

2018, 26(9): 1315-1323. doi: 10.13930/j.cnki.cjea.171159

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Abstract:
The red line of ecological protection is significance in controlling the intensity of human activity and in maintaining ecological security and sustainability. China has already carried out a demarcation work of red line for ecological protection at national scale and is now nearing completion at provincial scale. Also the demarcation of red line for ecological protection at municipal scale is underway. However, in the process of delineating the red line for ecological protection, problems such as difficulty in classification, diversification of indicators, determination of scale and selection of evaluation methods have been encountered. The evaluation of ecosystem services is one important step in delineating red lines. Ecosystem service refers to any benefit that mankind can obtain from the ecosystem and it is the basis of human survival and modern civilization. Human neglect of ecosystem services and their importance has caused serious damage to critical natural ecosystems. Therefore, it is necessary to carry out an evaluation of ecosystem services. To standardize the evaluation of ecosystem services in China, the Technical Guidelines for the delineation of red lines for ecological protection issued by the Ministry of Ecology and Environment recommended the NPP quantitative index method and the model evaluation method to evaluate ecosystem services. As China has wide geographical extent with complex topographic features and natural conditions, it is important to evaluate the suitability of the two methods for application in demarcating red lines for ecological service evaluation. Based on MODIS remote sensing images, the evaluation of ecosystem services in Hebi City was carried out using the NPP quantitative index method and compared with the model evaluation method. The purpose of the paper was to select a more suitable evaluation method for the area and to provide theoretical basis for the demarcation of red line for ecological protection smaller-scale. In this study, we compared the results of the ecosystem service evaluation derived from the two different methods. The results showed that there was a significant difference between the NPP quantitative index method and the model evaluation method at prefectural city scale. In order to judge which method was more accurate, we compared the results of the two evaluation methods in terms of spatial distribution of the forest park. The model evaluation method was more consistent for high evaluation area of ecosystem services (soil and water conservation functions and biodiversity protection function) and the area with better ecological protection (area overlapping ratios of 19% and 85%, respectively) in Hebi City. The evaluation result of the NPP quantitative index method was not consistent with the protection status. The reason why the NPP quantitative index method was inaccurate was that the selected parameters and calculation formulas were not suitable for the study area. Therefore, the model evaluation method was more accurate for evaluating ecosystem services in the study area, compared with the NPP quantitative index method at prefectural city scale. Appropriate method should be selected according to actual local conditions in order to accurately evaluate ecosystem services in future studies. The comparative analysis in this study provided a reference point for evaluating ecosystem services and delineating red lines for ecological protection.

Spatio-temporal evolution and agglomeration characteristics of agricultural production carbon sink in Henan Province

CAO Zhihong, QIN Shuai, HAO Jinmin

2018, 26(9): 1283-1290. doi: 10.13930/j.cnki.cjea.171141

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Abstract:
There are carbon emission and carbon absorption in agricultural production. Research on carbon sinks in agricultural production lacks clear system boundary, less medium scale researches and uniformity and integrity in accounting. To solve the above problems, this study analyzed the evolution trend and agglomeration characteristics using the Gene's coefficient and Lorenz curve methods through determining carbon sinks in agricultural production in Henan Province. The main results showed that agricultural production systems in Henan Province generally had carbon sink characteristic, and its carbon sequestration had been increased from 2000 to 2015. Carbon sinks in agricultural production in Henan Province amounted to 3.24×10⁷ tons in 2015, which was 22.53% of carbon emission driven by energy consumption in the province. Therefore, agricultural production had a positive ecological effect on decreasing greenhouse gas. There was gradual increase in the carbon sink due to agricultural production for the period from 2000 to 2015 as carbon absorption increased much faster than carbon emission with increasing agricultural modernization and agricultural production capacity. As far as structure was concerned, agricultural production was the main aspect of the natural function of carbon emission in Henan Province, was 70.15% of total carbon emission in agricultural production in 2015. Carbon emission via artificial agricultural input increased relatively faster than the natural function of carbon emission, which was the main reason for the increase in carbon emission via agricultural production in the province. The annual growth rates of carbon emission due to artificial agricultural input were respectively 0.85% and 3.27% in 2000 and 2015, which was 3.85 times that of the natural factors of carbon emission. The spatial distribution of carbon sink due to agriculture production in Henan Province showed universality, relative stability and significant agglomeration, with significant differences between the north and south and then east and west. The values of carbon sinks for agricultural production in the eastern and northern regions were relatively high, while those for southern and western regions were relatively low.

Effects of integrated rice-crayfish farming system on community structure and diversity of nirK denitrification microbe in paddy soils

ZHU Jie, LIU Hai, WU Bangkui, YUAN Feng, LIU Zhangyong, JIN Tao

2018, 26(9): 1324-1332. doi: 10.13930/j.cnki.cjea.171165

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Abstract:
Integrated rice-crayfish farming system is a symbiotic ecological model applicable in paddy field cultivation that is based on the combination of rice planting and clawed crayfish breeding in waterlogged conditions. In spite of so many efforts, the effects of integrated rice-crayfish farming system on denitrifying micro-organism diversity and community structure have remained unclear. In this study, we analyzed soil samples from both consecutive treatment of integrated rice-crayfish farming system (CR) in 2014-2016 and traditional paddy field (MR) treatment in order to investigate the effects of integrated rice-crayfish farming system on microbial diversity and community structure of nirK denitrification in paddy soils.. This was done by extracting soil nirK gene from rice field at heading stage using specific primers and Illumina Miseq high-throughput sequencing technology. The results showed that CR significantly increased the contents of nitrate nitrogen, total nitrogen and total carbon in paddy soils at heading stage, but had no significant effect on the ratio of carbon to nitrogen, contents of available nitrogen and ammonium nitrogen in soil. Compared with MR, CR significantly increased nirK gene abundance in soil, but did not significantly change its diversity. CR treatment changed the composition of nirK gene micro-organisms in the levels of order, family, genus and species. Compared with MR, CR reduced all taxonomic groups. The analysis of relative abundance of order showed no significant difference between CR and MR treatments. CR treatment changed species order, but did not change the relative abundance of common orders. RDA analysis showed that CR significantly changed community structure of nirK gene in soil. Nitrate nitrogen content was the main factor affecting the community structure of nirK denitrifying bacteria. It was obvious that rice-crayfish farming system had no significant effect on microbial diversity, but significantly increased microbial abundance index. In addition, it changed nirK denitrifying microbial community structure in terms of order, family, genus and species.

Effects of heterogous expression of Hvsusiba2 rice on methane mitigation and related micro-organism abundance in paddy fields

SU Jun, SHAN Zhen, CHEN Zaijie

2018, 26(9): 1333-1342. doi: 10.13930/j.cnki.cjea.180109

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Abstract:
A field experiment was conducted to explore the effects of genetically modified rice with Hvsusiba2 gene on paddy field methane mitigation. Hvsusiba2 gene is a transcription factor that acts on the upstream of starch synthesis pathway and is recognized as a key regulator for barley starch accumulation and assimilation distribution. Previous studies have shown that japonica rice (Oryza sativa L. subsp. japonica) integrated with Hvsusiba2 gene significantly reduces methane emission in paddy fields and increases content of seed starch. To further understand gene effects on cutting down of methane emissions under different rice genetic conditions, we introduced Hvsusiba2 into indica rice (O. sativa L. subsp. indica) and then investigated methane emissions from Hvsusiba2 rice field as well as the population size of bacteria associated with methane emissions in paddy fields during the growing season from April to September 2016. The results showed that the range of methane mitigation for the whole season was 54.7%-3.8%, compared with the control (wild rice). The highest mitigation rate was during booting period, reaching 54.7%. Total methane emissions of the two lines of Hvsusiba2 rice were respectively 5 060.16 mg·m^-2 and 5 250.60 mg·m^-2, while that under wild rice was 7 249.68 mg·m^-2 for the period from the first measurement to harvest. Methane reduction rates of the two lines were 30.30% and 27.58%, respectively. The abundance of 6 orders or families of methanogens and 2 groups of methanotrophs in Hvsusiba2 rice fields showed significant (P < 0.05, P < 0.01) decreases almost throughout the entire growing season when Hvsusiba2 rice was compared with wild rice. In addition, total bacteria populations during rice tillering, heading and flowering periods were significantly (P < 0.05, P < 0.01) lower in Hvsusiba2 rice than in wild rice. Population size of 6 methanogens were in the order of:Methanosaetaceae (Mst) > Archaea (ARC) > methanogens (MET) > Methanomicrobiales (MMb) > Methanosarcinaceae (Msc) > Methanobacteriales (MBT). Among these, Methanosaetaceae had the largest community, followed by Archaea. Of the 2 groups of methanotrophs, the abundance of MBAC was much larger than that of TYPE Ⅱ. After comparison of our experimental data with other studies, we concluded that Hvsusiba2 rice mechanism for reducing methane emission more likely regulated carbohydrate flow to ground parts of the plant, reduced assimilates transported to soil and lowered methane-related bacteria abundance, which ultimately reduced methane emissions.

Evaluation of heat resistance of hybrid rice restorer lines and combinations

GUO Xiaoyi, XIONG Hong, ZHANG Lin, JIANG Peng, ZHU Yongchuan, ZHOU Xingbing, LIU Mao, XU Fuxian

2018, 26(9): 1343-1354. doi: 10.13930/j.cnki.cjea.180004

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Abstract:
In order to reduce the impact of high temperature stress on rice, it is a priority importance in research to explore resistance of rice varieties to high temperature. Reference to industry standard evaluation index for high temperature issued by the Ministry of Agriculture, high temperature resistance characteristics of newly bred restorer lines and commonly used restorer line 'Chenghui727' were identified in production at the highest temperature of 38℃ and normal temperature treatment in artificially-controlled climatic conditions. Combinations of the restorer lines and varieties were divided into five grades. The heat resistance of different parents and hybrid rice combinations was also analyzed at artificially controlled high temperature and room temperature during flowering period. The results showed that:1) One extremely heat resistant restorer line R4093, 9 heat resistant restorer lines (including high fertility restorer lines such as R1015, R107, etc.), 4 extremely heat resistant varieties (combinations) and 25 heat resistant varieties (combinations), 5 extremely heat-sensitive restorer lines, 12 heat-sensitive varieties (combination) and 6 extremely heat-sensitive varieties (combination) were screened and identified. Among these, seed setting rate of high temperature resistant control N22, restoration line R103, R132 and R642, hybrid rice varieties (combination) 'Chuanyou5727', 'Yixiang2115', 'FanyuanA×R642', 'Zhong64xiangA×Huangzhan', 'Chuannongyouhuazhan', 'Rong18A×R1015', 'Yuxiang6203' and 'Chuanyou5727' were more than 70% in this experiment. Although identified as intermediate materials, these lines (varieties) had high potential for high temperature resistance, as further discussed on the production layout of rice varieties. It was concluded that high temperature resistance grade Ⅰ and grade Ⅱ were better and could be arranged in high temperature prone areas, light high temperature areas and high temperature free zones. Grade Ⅲ was an intermediate type that could be arranged in light high temperature areas and high temperature free zones. The grade Ⅳ and Ⅴ were heat sensitive and extremely heat sensitive. These lines could be arranged in a high temperature free zone to avoid high temperature damage to rice. 2) It was also found that the varieties (combinations) with high temperature resistant father (mother) were not always high temperature resistant, while those with high temperature sensitive father (mother) were not always high temperature sensitive. It was also related to the heat resistance and combining ability of the parents. The combination of parents with good heat resistance and good combining ability was mostly heat resistant, and the combination of the parents with poor heat resistance and poor combining ability was mostly heat sensitive. The results showed that the restorer lines R105, R642, R104 and R727 had better high temperature combining ability, but the combining ability of the restorer lines R107 and R1015 was relatively poor. The high temperature combining abilities of male sterile line Gan73A and Neixiang6A were better, while the high temperature combining abilities of FanyuanA, 606A, 608A and Zhong64xiangA were poor. The combination ability of conventional high quality rice variety 'Gold10' was better. Therefore, in order to breed more heat resistant hybrid rice combinations, screening parents with high heat resistant combining ability was critical.

Effects of subsoiling depth on topsoil properties, crop yield and water use efficiency in Lime Concretion Black soil

CHENG Sixian, LIU Weiling, JIN Yingjie, ZHOU Yanan, ZHOU Jinlong, ZHAO Yali, LI Chaohai

2018, 26(9): 1355-1365. doi: 10.13930/j.cnki.cjea.171149

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Lime Concretion Black soil is widely distributed in the south of the Huang-Huai-Hai Plain with area of 3.7 million hm², which is one of the main middle-to-low-yielding soil types in the region. Currently, the long-term continuous farming system is made possible by using small-sized 4-wheel tractors. However, owing to the years of over exploitation and improper mechanical plough, the effective depth of topsoil has gradually decreased and the plow pan thickened. The problem of shallow, solid and little topsoil in the plough layer has limited the ability of storage and release of fertilizer and continuous increase in crop yield in the Lime Concretion Black soils. Subsoiling is one of the main technologies in conservation tillage and the area with sub-soling in China has exceeded 10 million hm². Studies have shown that subsoiling can improve soil properties in plough layer by reducing soil bulk density and penetration resistance, increasing soil porosity, hydraulic conductivity and infiltration rate, and creating more favorable soil environment for root growth and crop production than rotary tillage. However, most studies have been carried out only on the 30 cm depth of subsoiling and little research has been focused on the effects of different depths of subsoiling on soil characteristics, root growth, crop yield and water use efficiency under wheat-maize cropping system in Lime Concretion Black soils. The objective of this study was to determine the effects of the depth of subsoiling on topsoil properties, crop yield and water use efficiency and to build the basis for establishing suitable depth of subsoiling in Lime Concretion Black soils. To that end, a multi-year experiment with four depths of subsoiling[30 cm (SS30), 40 cm (SS40), 50 cm (SS50) and 60 cm (SS60)] and rotary tillage (RT) as the control was carried out to study the effects of different depths of subsoiling on soil penetration resistance, soil three-phase (R) value, root growth, crop yield and water use efficiency. The results showed that increasing depth of subsoiling significantly reduced soil compaction, created more suitable soil three-phase (R) value and thus promoted crop root growth. In the four depths of subsoiling, decrease in soil penetration resistance and soil three-phase (R) value were the highest under SS60 treatment, root weight of winter wheat was the highest under SS40 treatment and root weight of summer maize the highest under SS50. Subsoiling not only increased crop yield, but also increased water use efficiency. Annual crop yield was the highest under SS30 treatment, 12.2% higher than that under RT. There was no significant difference in annual crop yield between SS30 and SS40 treatments. Annual water use efficiency was the highest under SS50 treatment, which was 12.7% higher than that under RT. Also there was no significant difference in annual crop yield among SS30, SS40 and SS50 treatments. Annual water use efficiency was respectively 9.1% and 8.8% higher under SS30 and SS40 treatments than that under RT. Therefore, subsoiling at the 30-40 cm depth was a suitable depth in Lime Concretion Black soils.

Effect of planting density on yield and quality of later-sown winter wheat along Huaihe River

SHAO Qingqin, YAN Suhui, ZHANG Congyu, REN Lantian, XU Feng, LI Wenyang

2018, 26(9): 1366-1377. doi: 10.13930/j.cnki.cjea.180374

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Abstract:
The area under later-sown winter wheat has since been increasing. To determine suitable planting density of later-sown winter wheat along the Huaihe River, we designed a split-plot field experiment including three later sowing dates (November 5, November 15 and November 25) and three planting densities (3×10⁶, 4.5×10⁶, and 6×10⁶ plants·hm^-2) for the 2013-2015 growing seasons. The yield and quality of winter wheat were investigated. The results showed that delay in sowing winter wheat shortened the growth stage of winter wheat, mainly affecting the length of vegetative period before jointing, but with little effect on the overall growth process. With delayed sowing date, dry matter accumulation at anthesis and maturity decreased, and translocation of dry matter in vegetative organs before anthesis along with the contribution of dry matter after anthesis decreased. At the same time, the contribution rate of dry matter after anthesis increased significantly. However, spike number, grain number per spike and thousand-grain weight all decreased, which caused significant reduction in yield. Moreover, protein, wet gluten contents and zeleny increased with delay of sowing date. Sowing date had more effect on dry matter accumulation and translocation in tiller stem spikes than on main stem spikes. Compared with November 5 sowing date, the November 25 sowing date decreased dry matter accumulation at anthesis, vegetative organ dry matter accumulation at maturity, grain dry weight, translocation of dry matter and its' contribution to grain of vegetative organs assimilate before anthesis respectively by 13.37%, 9.96%, 9.04%, 25.37% and 17.07% for main stem spikes; and respectively by 55.71%, 54.34%, 51.80%, 59.70% and 22.70% for tiller stem spikes. For the same sowing date, dry matter accumulation at anthesis and maturity increased with increasing planting density. Then translocation of dry matter in vegetative organ before anthesis decreased with increasing planting density. These conditions increased dry matter contribution to the related processes after anthesis. Also with increasing planting density, spike number increased, grain number per spike decreased, protein and wet gluten contents increased, but zeleny decreased. Compared with main stem spikes, planting density had more effect on dry matter accumulation and translocation of tiller stem spikes. Then compared with planting density of 3×10⁶ plants·hm^-2, 6×10⁶ plants·hm^-2 decreased grain weight per spike, grain number per spike and thousand-grain weight respectively by 17.90%, 13.60% and 4.76% in main stem spikes, and by 20.17%, 14.46% and 6.23% in tiller stem spikes. In conclusion, the rational increase in planting density increased yield and improved quality of later-sown winter wheat. Finally, our results showed that the best planting densities of later-sown winter wheat were 4.5×10⁶ and 6×10⁶ plants·hm^-2 for sowing dates of November 15 and November 25, respectively.

Effects of nitrogen fertilizer management on nitrogen absorption, utilization and soil inorganic nitrogen content under film mulch drip irrigation of maize

HOU Yunpeng, KONG Lili, LI Qian, YIN Caixia, QIN Yubo, YU Lei, WANG Lichun, WANG Meng

2018, 26(9): 1378-1387. doi: 10.13930/j.cnki.cjea.180104

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Abstract:
For reasonable application of nitrogen fertilizer under film mulch and drip irrigation in the semi-arid region of Jilin Province, a field experiment was conducted to investigate the effects of different nitrogen doses on spring maize yield, nitrogen utilization efficiency, nitrogen accumulation characteristics, soil inorganic nitrogen content and nitrogen balance during the growth period. The drip-irrigated film mulch experiment was conducted in 2016-2017 for N1 (100% basal fertilizer), N2 (50% basal fertilizer + 50% jointing fertilizer), N3 (30% basal fertilizer + 50% jointing fertilizer + 10% belling fertilizer + 10% flowering fertilizer) and N4 (20% basal fertilizer + 30% jointing fertilizer + 20% belling fertilizer + 20% flowering fertilizer + 10% filling fertilizer) nitrogen inputs. The results showed that grain yield under N2, N3 and N4 treatments were all significantly higher than that under N1 treatment. The highest maize yield was obtained under N4 treatment, increasing by 22.44% (2016) and 35.31% (2017) over that under N1 treatment. Absorption utilization efficiency, agronomic efficiency and partial factor productivity of nitrogen under N2, N3 and N4 treatments were all significantly higher than those under N1 treatment, respectively increasing in the ranges of 52.02%-83.21%, 63.69%-120.78%, 11.85%-22.46% (in 2016) and 92.44%-129.38%, 127.23%-203.09%, 22.10%-34.01% (in 2017). The highest increase was under N4 treatment. Nitrogen accumulation increased significantly with increasing nitrogen fertilizer application from jointing stage to mature stage, with the highest value under N4 treatment after flowering stage. Compared with N1 treatment, soil inorganic nitrogen content improved at the 0-20 cm soil layer under N2, N3 and N4 treatments after flowering stage, but dropped at the 40-100 cm soil layer at maturity stage. Nitrogen loss significantly reduced under N2, N3 and N4 treatments compared with that under N1 treatment, and it was lowest under N4 treatment in terms of nitrogen balance of the soil-crop system. In conclusion, optimum management strategy was obtained for 20% nitrogen base fertilizer, 30% dose at jointing stage, 20% at belling stage, 20% at flowering stage and 10% at filling stage. This gave a total nitrogen fertilizer application of 210 kg·hm^-2 under the experimental field conditions.

Moisture control reduces soil salt effect on summer maize

LIANG Shuoshuo, FANG Qin, YAN Zongzheng, LU Yang, SHAO Liwei

2018, 26(9): 1388-1397. doi: 10.13930/j.cnki.cjea.180095

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Abstract:
Winter wheat-summer maize double cropping system is the main planting pattern in the Low Plain around Bohai Sea of China, where fresh water is in serious shortage but with sufficient brackish water resources. Rational utilization of salt water resources is great significance for food safety in the area. However, brackish water irrigation of winter wheat caused salt accumulation in the upper soil which affected summer maize seedling emergence. Regulated water management was an effective and feasible way of reducing the negative effects of salinity, which was also beneficial for salt water irrigation in the double cropping system. In this study, a combination of pot and field experiments was conducted. The pot experiment consisting of 3 soil salinities[0.8 g·kg^-1(low salt content), 2.3 g·kg^-1(medium salt content) and 3.5 g·kg^-1(high salt content)] and 4 (for low salt content, ) or 8 (for medium and high salt water content) water contents (55%-85% of field capacity) were used to test the response of maize seedling emergence to soil water and salt contents. In the field experiment, salt water with different salinities[0 (CK), 3 g·L^-1 (SWT1), 4 g·L^-1 (SWT2) and 5 g·L^-1(SWT3)] was used to irrigate winter wheat at jointing stage to determine the effect of salt accumulation due to salt water irrigation and desalinization by irrigation/precipitation on maize growth and grain yield. The pot experiment results showed that 60% of field capacity supported normal seedling emergence under low soil salinity (0.8 g·kg^-1). In high soil salinity (3.5 g·kg^-1), seedling emergence was prolonged and the rate of emergence reduced. The effect of soil salinity on seedling emergence became serious with decreasing soil moisture content. Under high salinity conditions, high level of soil moisture alleviated the adverse effects of soil salinity on maize seedling emergence. Field experiment (in 2015 and 2016) results showed that with increasing salt concentration of irrigation water, soil salt content in the 0-20 cm soil layer increased significantly at winter wheat harvest period, with soil salt contents of 1.0 g·kg^-1(CK), 1.3 g·kg^-1 (SWT1), 1.6 g·kg^-1(SWT2) and 2.0 g·kg^-1 (SWT3). After summer maize sowing, an irrigation of 75 mm fresh water kept water content in the plough layer at 70% field capacity, and reduced soil salt content to 1.0 g·kg^-1, which was not significantly affected the growth and yield of summer maize. Yields of summer maize were 9 510.4 kg·hm^-2 (CK), 9 913.6 kg·hm^-2 (SWT1), 9 910.6 kg·hm^-2 (SWT2) and 9 986.0 kg·hm^-2(SWT3) in 2015, and 9 621.8 kg·hm^-2 (CK), 9 455.3 kg·hm^-2 (SWT1), 9 460.2 kg·hm^-2 (SWT2) and 9 221.4 kg·hm^-2(SWT1) in 2016 under salt water irrigation of winter wheat at jointing stage. Considering the temporal distribution of precipitation and the salt leaching of sufficient summer rainfall in the same season of summer maize growth, the effect of soil salt accumulation in winter wheat season on summer maize growth was avoidable. Therefore, irrigation of salt water with less than 5 g·L^-1 salinity at winter wheat jointing stage was safe for the succeeding crop, summer maize. The resonable water managements at key growth stages of winter wheat and summer maize simultaneously stabilized crops annual yield and water-salt balance under brackish water irrigation.

Substitution rate of organic fertilizer under long-term fertilization in black soils

GONG Haiqing, FU Haimei, XU Minggang, GAO Hongjian, ZHU Ping, GAO Hongjun

2018, 26(9): 1398-1406. doi: 10.13930/j.cnki.cjea.180146

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Abstract:
This study explored the relationship between the substitution rate of organic fertilizer (SROF) and soil fertility under long-term fertilizer application in black soils and thereby laid the basis of theoretical guidance for optimal fertilization in black soils. A 32-year dataset on black soil fertilization from Gongzhuling in Jilin Province experimental site was analyzed to determine the changes in SROF under different rates of organic fertilizer application based on crop removal of nitrogen (N) and soil N supply-demand balance. Results showed that crop yield increased gradually with increasing application years of organic fertilizer, which was slightly higher than for NPK fertilization after 32 years. A significant positive correlation existed between SROF and fertilization years as driven by crop removal of N (P < 0.01). Furthermore, SROF reached 100% and was stable after 29 years of high quantity manure (M2) application, higher than that of the application of conventional manure quality (M1). The correlation coefficients (R²) between SROFs of conventional and high quantity manure (M1 and M2) applications between based on crop N absorption (R_N) and soil N supply-demand balance (R_N') were 0.78 and 0.84 (P < 0.01), respectively. The corresponding root mean square errors (RMSE) were 10.4% and 14.6%, validating the method of calculation of SROF based on soil N supply-demand balance. The results suggested that SROF under high crop yield could be used as a fertility index under current intensive fertilization. Longer applications of organic fertilizers led to higher soil fertility and crop productivity and a gradual increase in SROF.

Irrigation water efficiency based on stochastic production frontier and influencing factors:An empirical study of wheat in Guanzhong Region, Shaanxi

LIU Weizhe, CHANG Ming, WANG Xiqin

2018, 26(9): 1407-1414. doi: 10.13930/j.cnki.cjea.180365

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Abstract:
Water resources are scarce in China, with a per capita water resource of 2 300-2 500 m³ which is only 1/4 of the world's average. Because of water shortages, there has been continuous conflict between various water consuming sectors. This has made it necessary to conduct studies on the efficiency of agricultural irrigation water for sustainable development. Although irrigation water efficiency has been studied in China, such research driven by micro-data is largely lacking for Northwest China. In this paper, a stochastic frontier analysis (SFA) model based on Cobb-Douglas production function was used to measure technical efficiency of wheat farmers and irrigation efficiency in Guanzhong Region, Shaanxi. Then the Tobit model was used to determine the influencing factors of irrigation efficiency. A total of 12 variables were selected, which reflected the personal, family, irrigation and cultivated land characteristics of farmers in the region. The results showed that technical efficiency of wheat farmers in Guanzhong Region was relatively high, with a range of 0.7-1.0 and a mean of 0.87. Irrigation efficiency was 0-0.5 and the mean was 0.31, which was far below technological efficiency. Analysis of the influencing factors of irrigation efficiency showed that farmers' education level, family economic status, irrigation channel condition, water shortage degree and irrigation water-saving degree had significant positive impact on irrigation efficiency. Then off-farm employment and non-farm income had a negative impact on irrigation efficiency. Age of farmers, irrigation water price, planting scale and subdivision of cultivated land had no obvious correlation with irrigation efficiency. Thus the study not only revealed the current conditions of wheat irrigation efficiency in Guanzhong Region, but also put forward critical suggestions on agricultural water resources management through the study of the influencing factors. The study also provided a reference base for improving irrigation water efficiency in Guanzhong Region in Shaanxi Province.

Land classification and spatio-temporal changes of wheat and corn in the middle reaches oasis of Heihe using multi-satellite data

CHEN Rui, ZHAO Chao, LIU Xingran, GUO Ying, SHEN Yanjun

2018, 26(9): 1415-1422. doi: 10.13930/j.cnki.cjea.180088

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Abstract:
Study on land use/cover and crop planting structure in agricultural regions is critical for analyzing changes in agricultural production activities and the ecological environment. The middle reaches oasis of Heihe is one of the most important oases in Northwest China and it is also the main commodity grain production base in Gansu Province. The use of surface water in Heihe is huge and has resulted in excessive utilization of surface water in the middle reaches of Heihe. The shortage of water resources has led to the deterioration of ecological environment in the oasis area in the middle reaches of Heihe, which has in turn caused significant damage to the development of Heihe oasis and agriculture. In order to accurately study the temporal and spatial changes of the oases in the middle reaches of Heihe, this study used MODIS satellite data to analyze the time-space variation characteristics of oases in the middle reaches of Heihe for the period from 2001 to 2015. Based on the Landsat/TM of 2001-2016, land use classification for the oasis area was obtained using the support vector machine classification. Then based on the HJ1A/CCD data for 2011-2016, a fine classification of crop planting structure was obtained from the HANTS filtered NDVI time series curve. The reason for the difference in satellite data selection was due to the failure in data quality and the late launch of the satellites. The land use classification method had high accuracy, with classification result accuracy higher than 88.46% and kappa coefficient of 0.81. The classification accuracy of wheat and maize compared with field verification points was higher than 90.8%. The results showed that 1) the area of the oasis in the middle reaches of Heihe generally increased. With the exception of 2014 and 2015 when the area of oasis slightly reduced, it increased from 2 701 km² in 2001 to 2 936 km² in 2015. 2) For 2001-2016, the area of bare land reduced by 436.7 km², that of cultivated land increased by 91.3 km², then of grassland and woodland increased by 289.6 km² and water body remained unchanged. 3) For 2011-2016, the planted area of wheat and corn decreased. Wheat total area decreased by 195.77 km² and that of corn decreased by 144.37 km². The results provided the basis and reference for adjustment of the local agricultural structure and crop yield estimation, and water resources and oasis ecology protection. The innovation point of the paper was that the area of oasis calculated based on area calculation formula for vegetation coverage. This correctly reflected the trend of change in the middle reaches of Heihe in the over 15-year period. It provided a new method for the calculation of oasis area, which greatly improved the accuracy of calculation when using low resolution (over 250 m) satellite data.

2018 Vol. 26, No. 9