中国生态农业学报(中英文)

Impact of rice field management on the spider community characteristics in Taihu Lake Basin

MAN Jiyong, YUAN Kai, CHEN Baoxiong, WANG Zirui, LIU Yunhui

2021, 29(9): 1467-1479. doi: 10.13930/j.cnki.cjea.210081

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Abstract:
Spiders are important natural enemies that provide a key biological control service in rice planting systems. In recent decades, agricultural intensification has caused a series of environmental problems, including the loss of biodiversity and the decline of associated ecosystem services. Therefore, it is necessary to explore if the spider diversity can be improved by adjusting the rice farming practices to enhance the biological control services to allow more sustainable agricultural production. Recent studies on rice field spiders have compared the spider diversity between organic and conventional farming systems. However, studies on spider diversity in green rice fields are rare. The Taihu Lake Basin is an important rice production area in China, but it has also suffered from serious non-point pollution in recent years. Thus, it is important to develop a sustainable rice production approach and conserve the biodiversity and associated ecosystem services for regional sustainability. In this study, we sampled spiders with a suction sampler to assess the impact of different farming practices, including organic, green, and conventional farming practices, on the diversity, composition, and dynamics of spiders in rice fields. The results indicated that 1) there were significant differences in the spider diversity among different farming systems. Species richness, abundance, and the Simpson diversity index of spiders in organic rice fields were significantly higher than those in the other two treatments. 2) There were no significant differences in spider body size and the ballooning capacity among different farming practices. 3) The composition of spider communities in organic rice fields was distinct from that in conventional rice fields, whereas green rice fields had a similar spider composition as that of conventional and organic rice fields. 4) Organic and green rice fields were dominated by web-building spiders, whereas conventional rice fields were dominated by hunting spiders. 5) Organic rice fields had many indicator species, such as Bianor incitatus, Chrysso octomaculata, and Clubiona corrugata, while the spider communities in green and conventional rice fields were dominated by generalist and common species and lacked endemic species. 6) The spider community diversity in rice fields changed with rice growth. The species richness and Simpson diversity indexes of the spider communities were greater in organic rice fields than those in conventional and green rice fields across all rice-growing seasons, except during the early tillering and elongation stages. In summary, compared with conventional and green farming systems, organic farming system sustains greater spider diversity and distinct spider compositions with more web-building and indicator species. The spider diversity under green farming system, on the other hand, did not differ from that under conventional rice practices. To improve spider diversity and the associated biological control services in rice fields, the transformation of conventional rice production to organic production and reduced chemical reagents input should be encouraged, which is also important for the ecological restoration of the Taihu Lake Basin.

Assessment of the annual greenhouse gases emissions under different rice-based cropping systems in Hubei Province based on the denitrification-decomposition (DNDC) model

WU Mengqin, LI Chengfang, SHENG Feng, FENG Junheng, HU Quanyi, CHEN Yukun, ZHOU Haozhi, LIU Tianqi

2021, 29(9): 1480-1492. doi: 10.13930/j.cnki.cjea.210099

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Abstract:
This study explored the impacts of different management measures on the annual emissions of methane (CH₄) and nitrous oxide (N₂O) from the main rice-based cropping systems in Hubei Province using the denitrification-decomposition (DNDC) model and observed emission data to estimate the annual greenhouse gas emissions via a geographic information system (ArcGIS). In 2019, rice–wheat (RW) and rice–ratoon rice (RO) cropping systems were implemented in Zaoyang City of Northwest Hubei, RO and rice–oilseed rape (RR) cropping systems were implemented in Wuxue City of Southeast Hubei, and RW, RO, and RR cropping systems were implemented in Qianjiang City of the Jianghan Plain. There were two cultivation modes for each rice-based system: conventional cultivation and optimized cultivation. The optimized mode included deep application of nitrogen fertilizer, water-saving irrigation, and straw returning to the field. The annual fluxes of CH₄ and N₂O were measured using the static closed chamber method. The field validation results showed that the normalized root mean square error between the observed and simulated values of CH₄ and N₂O emissions ranged from 19.3% to 24.2% under different rice-based cropping systems with different management practices, and the degree of model fitting was acceptable. According to the simulation results of the DNDC model, the global warming potential (GWP) for the rice growing regions in Hubei Province followed the order of Jianghan Plain > Southeast Hubei > Northwest Hubei, and the annual cumulative emissions of CH₄, N₂O, and GWP under different rice-based cropping systems in different regions was in the order of RW > RO > RR. The cultivation modes significantly affected the CH₄ and N₂O emissions. Compared with conventional cultivation, optimized cultivation lowered the CH₄ emissions per unit area by 9.5%–18.0%, 7.3%–18.4%, and 18.2%–22.4% under RW, RO, and RR, respectively. The N₂O emissions lowered by 4.2%–14.2%, 6.9%–24.7%, and 8.8%–18.1%, respectively. Moreover, compared with conventional cultivation, optimized cultivation decreased the annual cumulative CH₄ emissions by 11.8%, 14.4%, and 16.3% in Northwest Hubei, Southeast Hubei, and the Jianghan Plain, respectively, and decreased the annual cumulative N₂O emissions by 82.4%, 77.5%, and 83.0%, respectively. Under optimized cultivation, the GWP for Northwest Hubei was in the order of Xiangyang > Shiyan > Shennongjia, that for Southeast Hubei was in the order Huanggang > Xianning > Wuhan > Huangshi > Ezhou, and that for the Jianghan Plain was in the order Jingzhou > Jingmen > Xiaogan > Suizhou > Tianmen > Xiantao > Qianjiang. Our results show that the DNDC model can suitably simulate the greenhouse gas emissions of different rice-based cropping systems in Hubei Province. An optimized cultivation mode is needed to mitigate greenhouse gas emissions during rice production in Hubei Province.

Effects of rotational pattern and fertilization application on soybean yield under straws returning of preceding crop

ZHANG Guowei, WANG Xiaojing, YANG Changqin, SHU Hongmei, LIU Ruixian

2021, 29(9): 1493-1501. doi: 10.13930/j.cnki.cjea.210084

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Field experiments were conducted from 2018 to 2020 at the Soybean Experimental Station of the Jiangsu Academy of Agricultural Sciences in Nanjing, Jiangsu Province. A split-plot design was used to study the effects of straw returning and fertilizer application on the nutrient utilization and yield of soybeans under different rotation patterns. The main plot factor was different rotation patterns with straw returning of preceding crop of soybean (wheat–soybean, garlic–soybean, leaf mustard–soybean, and winter fallow–soybean), while the sub-plot factor was fertilizer application (no fertilizer and nitrogen [N], phosphorus [P], and potassium [K] compound fertilizer [15∶15∶15] at 225 kg∙hm⁻²). The results showed that rotation pattern and fertilization application significantly affected the soybean yield and yield components under crop straw returning of preceding crop, and the two factors had significant interactive effects on the yield, yield components, plant morphological index, biomass, nitrogen accumulation and distribution, and disease rate of soybean, as well as soil total nitrogen, available nitrogen contents. Compared with the winter fallow–soybean planting pattern, the other three rotation patterns decreased soil bulk density and available nitrogen content but increased soil organic matter and total nitrogen contents. Plant height, stem diameter, height of the bottom pod, branch number per plant, total biomass, grain biomass, total nitrogen accumulation, and grain nitrogen accumulation were the highest under garlic–soybean and leaf mustard–soybean rotation patterns, which were beneficial for yield. The final yield increased by 4.40%–10.30% and 5.66%–7.09% under fertilization treatments and by 4.88%–8.23% and 2.19%–8.78% under no fertilization treatments compared to the winter fallow–soybean planting pattern, respectively. The wheat–soybean rotation pattern inhibited soybean plant growth, and the total biomass, grain biomass, total nitrogen accumulation, and grain nitrogen accumulation were the lowest. The harvest index of biomass and nitrogen and the nitrogen production efficiency were the highest, but the yield was the lowest in this case, decreasing by 2.80–7.30% in the fertilizer treatments and by 7.45%–11.18% in the no fertilizer treatment compared to the winter fallow–soybean planting pattern. Wheat straw returning increased the diseased plant rate, whereas the leaf mustard–soybean and garlic–soybean rotations decreased the rate of diseased plants. Compound fertilizer application promoted plant growth, reduced the rate of diseased plants, improved soil total nitrogen and available nitrogen contents, soybean biomass and nitrogen accumulation, and harvest density. Although harvest index and nitrogen use efficiency of soybean were low, the yield significantly increased. Compared with the no fertilizer application treatment, fertilizer application increased the soybean yields of the garlic–soybean, leaf mustard–soybean, and wheat–soybean rotations by 9.21%–13.01%, 7.97%–14.02%, and 15.00%–15.91%, respectively. Therefore, the garlic–soybean and leaf mustard–soybean rotation modes should be popularized. Under a wheat–soybean rotation pattern, high yield is achieved when wheat straw is returned to the field. In the wheat–soybean rotation, fertilizers must be applied after wheat straw is returned to the field to achieve high yield.

Effects of the irrigation quota and drip irrigation pipes spacing on growth and development of summer maize with subsurface drip irrigation

YAO Jiawei, QI Yongqing, LI Huaihui, SHEN Yanjun

2021, 29(9): 1502-1511. doi: 10.13930/j.cnki.cjea.210058

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Water and soil resources in the North China Plain are mismatched. Traditional flood irrigation methods in this area have low water resource utilization and lead to serious water loss, which has caused a rapid decrease in groundwater levels. This study aims to improve the efficiency of irrigation water use in this area, determine the influence of subsurface drip irrigation on the field-scale water balance, and explore the effects of different irrigation amounts and drip irrigation zone spacing on the growth and water consumption of summer maize under subsurface drip irrigation conditions. Field experiments with two irrigation quotas (62 and 35 mm) and three drip irrigation pipes spacings (60, 80, and 100 cm) were conducted with the conventional flood irrigation as the control in farmlands in the North China Plain to analyze their effects on the growth and development, yield and irrigation water use efficiency of summer maize, and the soil profile moisture distribution, evapotranspiration, evaporation. Soil evaporation under subsurface drip irrigation was measured and compared using a microlysimeter. The results showed that irrigation water from subsurface drip irrigation mainly stayed in the 20–60 cm soil layer, and the wetted body presented a “small up and large down” form. The higher the irrigation amount, the larger the wetted body range, and the larger the soil volumetric water content. Compared to flood irrigation, the soil moisture contents of the 0–20 cm and 60–100 cm soil layers from subsurface drip irrigation were relatively low, and a dry soil layer formed at about 0–10 cm layer, which reduced soil evaporation. Maize plant height, leaf area index, and dry matter accumulation increased with increasing amounts of subsurface drip irrigation. Under flood irrigation, the maize plant height increased faster, and the accumulation rate of the maximum dry matter was higher compared to subsurface drip irrigation. Low amounts of subsurface drip irrigation delayed maize growth. When the irrigation amount was reduced by 22%, maize yield under subsurface drip irrigation did not differ from maize yield under traditional flood irrigation. Compared to flood irrigation, subsurface drip irrigation reduced soil evaporation by 30%, evapotranspiration by 8%, the E/ET value from 0.34 to 0.27; and increased the irrigation water use efficiency by 20%, the harvest index by 10%. The different drip irrigation zone spacing treatments had no effect on the growth and water consumption of maize. For high maize growth and yield, efficient irrigation water use, and cost-effective investments in drip irrigation equipment, the optimal irrigation quota was 62 mm with a drip irrigation zone spacing of 100 cm.

Optimal nitrogen application rate for winter wheat under multi-objective constraints in the North China Plain

DAI Na, SHI Wenjiao, SHI Xiaoli

2021, 29(9): 1512-1523. doi: 10.13930/j.cnki.cjea.210107

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Abstract:
The oversupply of nitrogen fertilizers has caused serious environmental problems, such as water pollution, destruction of soil structure, and global warming. Thus, the optimal nitrogen application rate of winter wheat should consider the environmental impacts. Many attempts have been made to evaluate the optimal winter wheat nitrogen application rate using different indicators, such as yield, nitrogen use efficiency, and nitrogen uptake. However, previous studies have only focused on economic benefits and did not consider the ecological benefits. Furthermore, the optimal nitrogen application rates have been evaluated with individual indicators; a systematic approach that integrates these indicators has not yet been presented. To better understand the optimal nitrogen application rate for winter wheat under multi-objective constraints in the North China Plain, this study used the daily meteorological data, observation data of the phenology, and the yield of winter wheat at nine stations (Tangshan, Huanghua, Luancheng, Huimin, Nangong, Ganyu, Shangqiu, Zhumadian, and Shouxian) from 1981 to 2017, to simulate five indicators of the economic and environmental benefits of the winter wheat (yield, nitrogen partial factor productivity, nitrogen uptake, the balance between yield increase and nitrogen saving, and environmental-economic benefits) by using the crop estimation through resource and environment synthesis (CERES)-Wheat model. The relationship between each indicator and the nitrogen application rate was investigated to determine the optimal nitrogen application rates under different constraints. Finally, the comprehensive optimal nitrogen application rate was determined according to the economic and ecological benefits. The results indicated that the optimal nitrogen application rates varied across stations and objective constraints. The average value of the optimal nitrogen application rate for the nine stations from high to low were that constrained by nitrogen uptake (363 kg∙hm⁻²), yield (257 kg∙hm⁻²), environment-economic benefits (190 kg∙hm⁻²), the balance between yield increase and nitrogen saving (173 kg∙hm⁻²) and nitrogen partial factor productivity (30 kg∙hm⁻²). The optimal nitrogen application rates under the constraints of the balance between yield increase and nitrogen-saving and environmental-economic benefits were 173 kg∙hm⁻² and 190 kg∙hm⁻², respectively. This indicates a reduction by approximately 20%−30% of the nitrogen application rates for constraints related to yield maximization, and reductions by 47% and 42% compared to the actual nitrogen application rates of farmers in the North China Plain. Thus, the environmental damage caused by nitrogen fertilizers can be minimized under these constraints. Meanwhile, approximately 90% of the wheat yield can be obtained with these optimal nitrogen application rates, and economic and ecological benefits can be simultaneously guaranteed. To secure grain production and minimize environmental impacts, the optimal nitrogen application rates under the constraints of the balance between yield increase and nitrogen-saving and environmental-economic benefits can be regarded as the regional reference for winter wheat planting in the North China Plain. The regional reference of the optimal nitrogen application rates for winter wheat varied with zones, it was 150 kg∙hm⁻² in the piedmont plains of Taihang Mountain and Yanshan Mountain, and 170 kg∙hm⁻² in the Nanyang Basin. For the winter wheat in the Shandong Peninsula and the plains around Bohai Sea, the optimal nitrogen application rate was higher (200 kg∙hm⁻²), and in the Haihe Plain, the optimal nitrogen application rate was 225 kg∙hm⁻².

Changes of maize lodging resistance after physiological maturity and its influencing factors in Sichuan

CHEN Xiang, LI Xiaolong, DU Xia, LIU Jiayuan, LIU Qianqian, YUAN Jichao, KONG Fanlei

2021, 29(9): 1524-1532. doi: 10.13930/j.cnki.cjea.210044

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Densification planting and delayed harvesting are important measures for the promotion and development of mechanized grain harvesting technology of maize, but they also reduce the lodging resistance of stalks and increase the risk of lodging. The appearance of maize lodging not only increases the difficulty of mechanical harvesting and reduces the speed of mechanical harvesting, but also increases the loss of ear caused by lodging and reduces the yield of mechanical grain harvest. Therefore, the purpose of this experiment was to explore the changing law of the lodging resistance ability of maize stalks after physiological maturity under different densities and to provide a scientific basis for the development of maize dense planting and high-yielding mechanical grain harvest technology. This experiment used ‘Zhenghong 6’ as the material and set 6 density treatments: 3.0×10⁴ plants∙hm⁻² (B1), 4.5×10⁴ plants∙hm⁻² (B2), 6.0×10⁴ plants∙hm⁻² (B3), 7.5×10⁴ plants∙hm⁻² (B4), 9.0×10⁴ plants∙hm⁻² (B5), and 10.5×10⁴ plants∙hm⁻² (B6). In the physiological maturity period (August 6, A1), 11 d after physiological maturity (August 17, A2), 22 d after physiological maturity (August 28, A3), and 35 d after physiological maturity (September 10, A4), 5 plants in each plot were sampled and the changing laws of stalk strength, internode morphology, internode dry matter, moisture content, etc. were determined. The results showed that the internode stalk strength of maize decreased after physiological maturity, but the decreasing range gradually reduced with time. After physiological maturity, the dry weight per unit length and water content of stalk decreased, while the internode length-to-diameter ratio increased slightly. Stalk strength and it’s change with time were significantly different among different densities after physiological maturation. In the density range of 4.5×10⁴ plants∙hm⁻² to 10.5×10⁴ plants∙hm⁻², the decreased amplitude of stalk strength showed a decreasing trend with the increase of density, and that of stalk strength of low density was greater than that of high density. The increase in planting density resulted in a significant decrease in stalk dry weight per unit length and a significant increase in the internode length-to-diameter ratio. The results showed that the decrease of stalk dry weight per unit length after physiological maturity was the main reason for the decrease of stalk strength. The increase of planting density significantly reduced the stalk strength, and with the extension of standing time, the stalk strength further decreased. The stalk strength of different densities decreased differently, and the decrease rate of low density was greater, but the stalk strength of high density was still lower than that of low density treatment all the time. Therefore, properly dense planting and harvest at the right time can reduce the risk of lodging caused by the decline of the standing capacity of culms after physiological maturity of maize.

Response of fine roots of apple to plastic film mulching in the dry tableland of eastern Gansu

SUN Wentai, MA Ming, DONG Tie, NIU Junqiang, YIN Xiaoning, LIU Xinglu

2021, 29(9): 1533-1545. doi: 10.13930/j.cnki.cjea.210071

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This study investigated the annual growth dynamics of apple tree roots in the dry plateau of Longdong and the temporal and spatial differences in the number, morphology, branching characteristics of the roots, and soil physical and chemical properties in vertical soil layers under film mulching and soil moisture conservation measures. Eighteenth-year-old apple trees (‘ Nagano Fuji No.2’) were assessed three times in the rooting peak times of apple tree: from spring sprouting to vigorous growth of new shoots (Ⅰ), shoots stopped growing (Ⅱ), and from fruit harvest to defoliation (Ⅲ). Using the soil profile and stratified sampling method, different treatments (conventional tillage [CK], film-mulching for two years [2Y], film-mulching for four years [4Y], and film-mulching for six years [6Y]) were investigated to analyze the spatial distribution of biomass, root length, surface area, specific root length, and the specific branch (branch number/dry matter weigh) of roots. Regression analysis was used to assess the fine root growth strategy for apple trees with plastic film mulching. The results showed that the rooting peak Ⅲ was the most important stage of the annual growth cycle of apple roots. The fine roots biomass at rooting peak Ⅲ under each treatment was 73.55%–84.85% of the total biomass at the three rooting peaks. The number of fine root branches at rooting peak Ⅰ in the surface soil (0–20 cm) was 130.67%, 100.53%, 156.63%, and 238.63% of that at rooting peak Ⅲ, which effectively improved the utilization of the soil resources in situ. At rooting peak Ⅲ, CK promoted the distribution of fine root length and root surface area in the surface soil, which were 275.64% and 248.96% of those at rooting peak Ⅰ, respectively. The number of branches and specific branches were only 76.53% and 14.68% of those at rooting peak Ⅰ, which expanded the effective nutrient space and reduced the internal competition of the root system. The soil water content in the short-term mulching (2Y) treatment in each soil layer were 112.39% (0−20 cm), 118.04% (20−40 cm), 124.06% (40−60 cm), 133.59% (60−80 cm), and 114.49% (80−100 cm) of CK; and the fine root biomass was 116.72%, 232.35%, and 112.09% of CK at the three rooting peak times. Compared with CK, the specific root length of the surface fine roots increased by 47.1% and 62.92% at rooting peaks Ⅰ and Ⅲ, and the root surface area increased by 67.21% and 56.88% in 2Y treatment. The number of fine root branches in the deep soil (80–100 cm) increased by 282.22% and 7.27%, respectively, compared with CK. The 2Y treatment promoted fine root morphological trait expression at the surface soil and branch structure establishment in the deep soil. Fine roots were evenly distributed in the 0–100 cm vertical soil layer and 0–120 cm horizontally from tree. Compared with CK, the 6Y treatment increased the number of fine root branches and specific branches by 6.11% and 34.6%, respectively, in the early growth stage, but by 58.1% and 19.56% in the late growth stage. These results demonstrate the characteristics of complex branches in the early growth stage and simplified branches in the late growth stage significantly inhibit the growth of fine roots at rooting peak Ⅲ. The fine root length, root surface area, and specific root length in the deep soil were 35.19%, 40.43%, and 82.67% of those of CK, respectively, in 6Y treatment. Fine root growth was affected by the phenological period and the turnover of tree nutrients; the “conservatively obtaining resources” growth strategy was applied in the early growth stage, and the “rapidly obtaining resources” growth strategy was adopted in the late growth stage. Short-term film mulching (2Y) can improve the physical and chemical properties of the soil and promote fine root extension. Damage from long-term plastic film mulching (6Y) to the subsurface soil (20–40 cm) prevented the fine roots from settling down and they became concentrated in the surface layer.

Nitrate storage and leaching in the critical zone of farmland in the North China Plain

CHEN Xiaoru, LI Xiaoxin, HU Chunsheng, LEI Yuping, NI Rui, MA Lin

2021, 29(9): 1546-1557. doi: 10.13930/j.cnki.cjea.210087

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Abstract:
After the reform and opening in 1978, China’s nitrogen (N) fertilizer input increased sharply, increasing grain yield, but also causing serious soil nitrate accumulation and leaching problems that threaten groundwater security. This study aimed to explore the effects of N fertilizer input on nitrate storage in the vadose zone of farmlands (grain and vegetable fields) in the North China Plain (NCP) and to quantify the total amount of nitrate leaching from the 2–50 m underground aquifer of the NCP. We collected soil profiles from areas with different groundwater table depths (2–50 m) of the NCP farmlands and measured the nitrate content in different soil layers. Concurrently, data on N fertilizer input and changes in the farmlands of different provinces and counties of the NCP were collected from literatures and relevant websites for 42 years (1978–2019). Nitrate storage in the vadose zone was calculated using a geographic information system (GIS). The ratio of nitrate storage to nitrogen fertilizer input (NR) in the vadose zone was proposed from the perspective of regional blocks. The NR value of grain and vegetable fields in the NCP ranged from 0.14 to 0.39 and from 0.15 to 0.41, respectively. This provided scientific data and a theoretical basis for reducing the leaching loss of nitrate from the vadose zone to the aquifer. The relationship (NR value) between N fertilizer input and nitrate storage in the vadose zone at different groundwater table depths reflects the degree of influence of N fertilization on the amount of residual nitrate in the vadose zone. Moreover, under the same N fertilizer conditions, the leaching loss of nitrate from the NCP farmlands was estimated at groundwater table depths of 2–50 m. The results showed that high fertilizer application in the NCP farmlands led to large amounts of nitrate leaching into the vadose zone-aquifer system. The total nitrate leaching from grain and vegetable fields under 2 m of groundwater was 6.7565 and 1.9956 million tons, respectively, accounting for 13% and 14% of the total N fertilizer input from grain and vegetable fields in 42 years (1978–2019). Under ideal conditions (depth of vadose zone >10 m, the same farmland area and soil texture), higher N fertilizer input was associated with greater total nitrate storage in the vadose zone. Nitrate storage per unit area of farmland (grain and vegetable fields) in the NCP increased with increasing depth of the vadose zone at areas with 2–50 m of groundwater depth. This study also indicated that a thick vadose zone played an important role in nitrate nitrogen interception. In the 2, 3, 6, 10, 16, 25, 40, and 50 m vadose zones, grain field nitrate storage accounted for 14%, 18%, 26%, 30%, 33%, 35%, 38%, and 39% of the total N fertilizer input over 42 years (1978–2019), respectively. Vegetable field nitrate storage at the same depths of the vadose zone accounted for 15%, 20%, 28%, 32%, 34%, 36%, 40%, and 41% of the total N fertilizer input over 42 years (1978–2019), respectively. This study suggests that the relevant departments and agricultural workers should consider the depth of the vadose zone to comprehensively evaluate nitrate nitrogen accumulation and groundwater safety issues from a regional perspective.

Effects of tillage and straw returning method on the distribution of carbon and nitrogen in soil aggregates

ZHANG Yuming, HU Chunsheng, CHEN Suying, WANG Yuying, LI Xiaoxin, DONG Wenxu, LIU Xiuping, PEI Lin, ZHANG Hui

2021, 29(9): 1558-1570. doi: 10.13930/j.cnki.cjea.200791

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The North China Plain is a major grain production area in China, and wheat-maize rotation is the main cropping pattern in this region. Long-term straw returning and shallow rotary tillage have caused soil quality problems, such as a shallow plow soil layer, thickening of the plow bottom, and nutrient accumulation at the soil surface. These problems restrict a sustainable and stable grain yield. This study examined the effects of different agricultural management practices of tillage measures and methods of straw returning of physical protection on the soil aggregate composition and stability, the distribution of organic carbon and nitrogen in the aggregates at the Luancheng Agricultural Ecosystem Experimental Station, Chinese Academy of Sciences. A tillage and straw counters-field positioning experiment was conducted from 2016 with five treatments: no-straw and rotary tillage (as control 1, RT), straw mulching and rotary tillage (as control 2, SR), straw mulching and deep ploughing (SP), straw incorporated into 0−40 cm soil layer of 40 wild no-wheat planting belt (SID), and straw buried into 30−40 cm soil layer (SBD). The three latter treatments represented different straw returning methods. The results showed that changing rotary tillage to deep tillage under straw returning significantly increased the content of large macroaggregates (>0.25 mm). Different straw returning methods led to significantly different changes in water stability of the large (>2 mm) and small (0.25–2 mm) macroaggregates. Straw returning to the deep soil layer increased the content of large water-stable macroaggregates in soil layers below 10 cm (>2 mm), whereas increased the content of small water-stable macroaggregates (0.25–2 mm) in the surface layer. The changes in the water stability of large and small macroaggregates were impacted by the straw returning method. Straw returning to deep soil layer significantly increased the stability in the subsurface layer (20–40 cm) and decreased the structural fragmentation rate of soil aggregates. Deep straw returning effectively integrated the 0–40 cm soil layer, eliminated the surface accumulation of nutrients, and significantly increased the soil organic carbon and nitrogen contents in the subsurface layer and the contribution of large macroaggregates to soil organic carbon and nitrogen. The contribution of organic carbon and nitrogen of the macroaggregates (>2 mm) in the 20–40 cm soil layer was 42.2%–44.0% and 32.8%–49.9%, respectively, which increased by 48.7%–54.9% and 32.8%–101.8%, respectively, compared to straw-free rotary tillage. In summary, the straw returning to deep soil layer improved soil structure of tillage layer, promoted integration of soil layers and emilimated nutrient accumulation in soil surface layer.

Effect of fertilizer application on soil carbon loss in purple soil

SHEN Jiao, WANG Xiaoguo, MA Han

2021, 29(9): 1571-1581. doi: 10.13930/j.cnki.cjea.210123

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Studies on organic carbon gas exchange and runoff loss in farmland soil are relatively isolated, and the synergy between the two pathways is poorly understood. In this study, simultaneous tests of organic carbon gas exchange and soil–water interface migration process of purple soil under different fertilization treatments were conducted using a runoff plot that allowed interflow observation. The experimental treatments included no fertilizer (CK), chemical fertilizer (nitrogen, phosphorus, and potassium; NPK), pig manure plus synthetic NPK fertilizer (OMNPK), and the incorporation of crop residues plus synthetic NPK fertilizer (RSDNPK). The results showed that 1) the soil respiration rate and carbon dioxide (CO₂) emission flux under different fertilization treatments were RSDNPK > OMNPK > NPK > CK, indicating that the application of chemical fertilizer, organic fertilizer, and straw returning increased the soil respiration rate of purple soil. The CO₂ emission flux of RSDNPK was 4155.87 kg(C)∙hm⁻², significantly higher than those of the other fertilization treatments. 2) The soil organic carbon runoff loss flux was in the order of RSDNPK > OMNPK > CK > NPK, and there were differences in the runoff loss pathways under different fertilization treatments. RSDNPK reduced sediment erosion and significantly increased the flux of dissolved organic carbon (DOC) loss in the interflow, reaching 8.29 kg(C)∙hm⁻². The DOC loss flux of the interflow accounted for 49.82%–92.11% of the total runoff carbon loss flux under different fertilization treatments, indicating that interflow was the main pathway of soil organic carbon loss in purple soil. 3) The total fluxes of soil organic carbon loss under RSDNPK were significantly higher than those under other fertilization treatments, which was not significantly different between OMNPK and NPK. The proportion of CO₂ emission fluxes to the total fluxes was more than 99% in each fertilization treatment, indicating that gaseous loss was the main mechanism of organic carbon loss in purple soil. 4) We calculated the carbon loss flux per unit yield for each fertilization treatment and combined the economic benefits with the ecological environmental load. The results showed that the carbon loss flux per unit yield in CK was significantly higher than that in other fertilization treatments. The soil organic carbon content of the OMNPK treatment was 5.86 g∙kg⁻¹, greater than that of NPK, indicating that organic fertilizer application is beneficial to the accumulation of soil organic carbon. OMNPK should thus be prioritized in the purple soil area.

Effects of wheat straw and nitrogen fertilizer application on the soil microbial biomass carbon and nitrogen in the rhizosphere of rice

LUO Jialin, ZHAO Yahui, YU Jianguang, WANG Ning, XUE Lihong, YANG Linzhang

2021, 29(9): 1582-1591. doi: 10.13930/j.cnki.cjea.201019

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Abstract:
Soil microbial biomass carbon and nitrogen (SMBC and SMBN, respectively) are key factors that characterize soil fertility and its’ change. The rhizosphere is a hotspot of microbial interactions in rice fields. Rhizosphere microbiota are important for rhizosphere ecology and are the impetus of soil organic matter and nutrient transformation. This study investigated bulk and rhizosphere SMBC and SMBN in paddy soils in response to wheat straw addition and different amounts of nitrogen fertilizer application in the typical rice and wheat rotation areas of the middle and lower reaches of the Yangtze River. There were four treatments (in triplicate): no straw or nitrogen fertilizer (CK), straw addition (SN0), straw and low nitrogen fertilizer addition (SN1), and straw and high nitrogen fertilizer addition (SN2). The results showed that, compared to CK, the SMBC contents in the SN0 rhizosphere and bulk of high sandy soil increased by 40.3% and 48.1%, respectively, while those in yellow mud soil increased by 95.7% and 75.4%, respectively. The SMBN contents in the rhizosphere of high sandy soil did not change significantly, but decreased by 19.9% in bulk soil. The SMBN contents in the rhizosphere and bulk of SN0-treated yellow mud soil decreased by 19.5% and 49.0%, respectively. Low nitrogen fertilizer application significantly increased the SMBC content in the rhizosphere of sandy soil and the bulk of yellow mud soil and increased the SMBN content in the rhizosphere and bulk of both soils. With increased nitrogen fertilizer application, SMBC and SMBN contents in the rhizosphere and bulk of both soils significantly increased. Compared with SN0, the SMBC content in the rhizosphere of SN1 in sandy soil increased by 5.1%, that in bulk decreased by 12.9%, and that in the bulk of yellow mud soil increased by 11.1%. There was no significant change in SMBC content in the rhizosphere of yellow mud soil. SN1 treatment led to an increase in the SMBN contents of the rhizosphere and bulk of sandy soil by 17.3% and 9.8%, respectively, and an increase in the SMBN contents of the rhizosphere and bulk of yellow mud by 36.1% and 68.9%, respectively. SN2 treatment led to an increase in the SMBC content in the sandy soil rhizosphere and bulk by 8.6% and 39.3%, respectively, and by 34.58% and 3.05% in yellow mud, respectively, over those of SN0. For the SN2 treatment, sandy soil rhizosphere and bulk SMBN increased by 27.0% and 13.5%, respectively, and they increased by 25.6% and 232.9%, respectively, in yellow mud soil, compared with SN0. These comprehensive analyses show that nitrogen fertilizer addition can increase the SMBC and SMBN contents in bulk and rhizosphere soils, thereby improving soil nutrient availability. Straw returning with nitrogen fertilizer greatly improves soil fertility and promotes crop growth in the rice-wheat rotation areas of the middle and lower reaches of the Yangtze River.

Effects of tobacco stalk biochar-based fertilizer on the organic carbon fractions and microbial community structure of adlay soil

HU Kun, ZHANG Hongxue, GUO Liming, WU Fengying, ZHOU Biqing, XING Shihe, MAO Yanling

2021, 29(9): 1592-1603. doi: 10.13930/j.cnki.cjea.210127

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Abstract:
Long-term continuous cropping of adlay ( Coix lacryma-jobi L.) and the indiscriminate application of chemical fertilizers have led to soil fertility declines and acidification. To explore the effects of tobacco stalk biochar-based fertilizer on the soil organic carbon (SOC) fractions and microbial community structure and abundance, tobacco stalk biochar-based fertilizer was used in a field experiment with four treatments: no fertilizer, conventional fertilizer, low tobacco stalk biochar-based fertilizer, and high tobacco stalk biochar-based fertilizer. Changes in the activities of four enzymes related to soil carbon cycling and microbial activity were evaluated, and the relationships between the soil pH, SOC fractions, soil enzymes, and soil bacterial abundance were analyzed. The results showed that: 1) The application of tobacco stalk carbon-based fertilizer significantly increased the soil pH and the contents of SOC, dissolved organic carbon (DOC), particulate organic carbon (POC), and microbial biomass carbon (MBC) (P<0.05). The MBC was most affected, increasing by 41.09%−76.04% compared to conventional fertilizer application. 2) The application of tobacco stalk biochar-based fertilizer significantly increased the activities of soil amylase and dehydrogenase (P<0.05). Compared to conventional chemical fertilizers, amylase and dehydrogenase activities increased by 44.28% and 57.54%, respectively, whereas the soil invertase activity was unaffected when tobacco stalk biochar-based fertilizer was applied. 3) The application of tobacco stalk biochar-based fertilizer increased the Chao1 and Shannon indexes, abundance and diversity of the soil bacterial communities. 4) The application of tobacco stalk biochar-based fertilizer affected the composition and structure of the soil bacterial community, increased the relative abundance of Actinomycetes and Bacteroides, and reduced the relative abundance of Proteobacteria and Chloroflexus. It also significantly increased the abundance of Nitrospira, Bryobacter, and other bacterial genera, and significantly reduced the abundance of Aciditerrimonas and Crenothrix. 5) Redundancy anaylsis showed that soil pH, carbon fraction, soil enzymes activities, and soil bacterial community abundance were correlated each other after the application of tobacco stalk biochar-based fertilizer; soil pH, SOC, POC, DOC, MBC were significantly positively correlated with the activities of various soil enzymes (P<0.05), but were significantly negatively correlated with Proteobacteria (P<0.05). In summary, tobacco stalk biochar-based fertilizer increased the soil pH, SOC fractions, soil enzymes activities, and soil bacterial abundance, which improved the soil bacterial community structure and the adlay planting soil and optimized the soil ecology. This study provides a reference for the resource utilization of tobacco stalk and improvements in soil fertility.

Influence of intercropping Sedum plumbizincicola with Capsicum annum on the migration and availability of soil cadmium

WANG Gaofei, ZHOU Peng, WANG Yongping, WANG Yan, LIN Shan, XING Dan

2021, 29(9): 1604-1614. doi: 10.13930/j.cnki.cjea.210038

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Abstract:
A field experiment was conducted in Xinpu New District, Zunyi City, Guizhou Province, in 2019 to explore the effects of different Sedum plumbizincicola intercropping patterns on the migration and availability of cadmium (Cd) in the soil around the roots of Capsicum annum. Five planting patterns were established: monoculture S. plumbizincicola, monoculture C. annum, stripe intercropping of C. annum with S. plumbizincicola (JZ1), cross intercropping of C. annum with S. plumbizincicola (JZ2), and mixed intercropping of C. annum with S. plumbizincicola (JZ3). Soil samples were collected around the C. annum roots at harvest, and the Cd content, soil pH, organic matter content, and contents of total and available nitrogen (N), phosphorus (P), potassium (K), and content of glomalin (GRSP) were measured and analyzed. The results showed that, compared to C. annum monoculture, the contents of acid-soluble Cd and reducible Cd in the soil around the C. annum roots effectively decreased by 39.6% and 23.9% in the cross intercropping system with S. plumbizincicola, and 41.5% and 29.0% in mixed intercropping system with S. plumbizincicola, respectively. The risks of soil Cd migration and availability were also reduced. Stripe intercropping C. annum with S. plumbizincicola had no effect on Cd mobility and availability in the soil around the C. annum root system. The Cd migration of the crossing intercropping and mixed intercropping systems decreased by 25.8% and 34.2%, respectively, and the Cd availability decreased by 11.6% and 26.9%, respectively. The stripe, cross and mixed intercropping systems did not affect the contents of Cd in oxidizable and residual states, but significantly increased the content of easily extracted GRSP in the soil by 24.5%, 39.9%, and 40.6%, respectively. Cross intercropping C. annum with S. plumbizincicola and mixed intercropping treatments also significantly increased the total soil GRSP content by 51.7% and 86.7%, respectively. Redundancy analysis showed that the importance of the soil environmental factors on soil Cd migration and availability followed the order: total extracted GRSP > available potassium > pH > easily extractable GRSP > total potassium > total phosphorus > total nitrogen > alkaline hydrolyzed nitrogen > available phosphorus > organic matter. The extractable GRSP and available potassium from the soil were the key regulatory factors affecting soil Cd migration and availability. In summary, intercropping with S. plumbizincicola significantly reduced the risks of Cd migration and availability in the soil around the C. annum roots, and the effects of cross and mixed intercropping were better than that of stripe intercropping. These results provide a theoretical basis for better usage of farmland with low to medium levels of Cd.

Effects of winter crops on the earthworm yield and earthworm cast in paddy fields

LI Chao, ZHAO Yang, GUO Lijun, CHENG Kaikai, TANG Haiming, HUANG Min, TANG Wenguang, WEN Li, WANG Ke, CUI Ting, XIAO Xiaoping

2021, 29(9): 1615-1624. doi: 10.13930/j.cnki.cjea.200821

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Abstract:
There is a large market demand for earthworms; thus, earthworm breeding will increase in the future. However, artificial earthworm breeding faces many problems, such as large labor input, high breeding costs, and difficulty in large-scale breeding. Increased earthworm production by planting winter crops may be an effective way to solve these problems. This study incorporated a field investigation and rainfall and accumulated temperature data from 2017 to 2020 to investigate the effects of different winter crops, including fallow (T1), milk vetch (T2), and rapeseed (T3), on the yield and cast of Pheretima guillelmi to provide theoretical and technical support for earthworm production in paddy fields. The results showed that the coefficient of variation (CV) of earthworm yield in different years was positively correlated with the CV of winter crops yield (P<0.01). Continuous rainfall from October to December and low temperatures from December to February from 2018 to 2019 led to a significant decrease in the yields of winter crops and earthworms. The soil organic matter content (average value under three yield levels) was in the order of rapeseed > milk vetch > fallow, and the earthworm yield and earthworm manure yield were significantly positively correlated with the soil organic matter content (P<0.05) and with winter crop yield. The earthworm individuals number per m² of fallow, milk vetch, and rapeseed was 8.4−12.8, 11.2−30.8, and 20.4−49.1, respectively, the average earthworm individuals number per m² was 10.8, 20.7 and 36.3, respectively. The earthworm yield was 290−428 kg·hm⁻², 368−1054 kg·hm⁻², and 763−1845 kg·hm⁻², respectively, and the average earthworm yield were 373 kg·hm⁻², 695 kg·hm^−2, and 1364 kg·hm⁻², respectively. The earthworm cast yield was 1921−3126 kg·hm⁻², 3023−10 116 kg·hm⁻², and 6034−18 958 kg·hm⁻², respectively, and with the averages of 2652 kg·hm⁻², 6438 kg·hm⁻², and 12 545 kg·hm⁻², respectively. The averages were in the order of rapeseed > milk vetch > fallow. The ratio of cast weight to fresh earthworm weight increased with increasing winter crop yield, with an average value of 8.8; the average values for fallow, milk vetch, and rapeseed were 7.1, 9.1, and 9.0, respectively. Variation in earthworm yield and earthworm cast yield between different yield levels of rapeseed was less than that of milk vetch, indicating that rapeseed was beneficial for higher yield stability for earthworms and earthworm casts. In summary, the yield of earthworms and casts was greatly disturbed by rainfall and accumulated temperature, and the high-yield fields of winter crops had high soil organic matter content, which was conducive to increasing the yields of earthworms and earthworm casts and increasing their stability. Planting rapeseed also had a beneficial effect.

Analysis of the mediation effect of urbanization on non-point source pollution from the planting industry

LUO Haiping, HE Zhiwen, HU Xueying

2021, 29(9): 1625-1635. doi: 10.13930/j.cnki.cjea.210033

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Abstract:
In the light of continued urbanization, it is important to analyze the effect of urbanization on fertilizer non-point source pollution in China to alleviate ecological pressure and promote green and high-quality agriculture development. This study used the unit survey and assessment method to measure the total emissions and emission intensity of fertilizer non-point source pollution in 31 provinces (cities, autonomous regions) in China from 2008 to 2018. The mediation effect model was used to analyze the influence of urbanization on fertilizer non-point source pollution. Compared with existing studies, this study has two aims. The first is to analyze the influence of urbanization on fertilizer non-point source pollution via the mediation effect, and to clarify the mechanism of how urbanization affects fertilizer non-point source pollution. The second is to analyze the spatial heterogeneity in the impact of urbanization on the fertilizer non-point source pollution in grain function areas, e.g., differences in the mechanisms of various mediation factors in different grain function areas. Our empirical results showed that: 1) from 2008 to 2018, fertilizer non-point source pollution in China had an inverted “U” pattern, first increasing and then decreasing, with 2015 as the inflection point. The total amount and intensity of emissions fell to the lowest levels at the end of the study period, 5.16 million t and 37.65 kg·hm⁻², respectively. 2) On a national level, urbanization had a mediating effect on fertilizer non-point source pollution owing to technological progress, labor migration, and farmland endowment. The mediation effect of farmland endowment had the highest absolute value (0.0092), and the mediation effects of labor and technological progress were increasing to 0.0040 and 0.0033, respectively. 3) There was significant spatial heterogeneity in the influence of urbanization on fertilizer non-point source pollution. For technological progress, the absolute value of the mediation effect in the major grain-consuming areas was the highest (0.0160), followed by that in the major grain-producing areas (0.0118), whereas the grain-balance areas did not have a significant mediation effect. For labor, there was only a significant mediation effect in the major grain-production areas (0.0538). For farmland endowment, the absolute value of the mediation effect in the major grain-consuming areas was the highest (0.0126), followed by that in the grain-balance areas (0.0095), and the major grain-producing areas had the lowest absolute value (0.0055). The direction of the mediation effect in grain-balance areas was opposite to that in other regions. Therefore, it was important to protect arable land in the major grain-consuming areas and to form a cross-regional collaboration system of “occupation-compensation balance”. In the major grain-producing areas, high-quality labor should be actively guided to return to the agricultural sector. In the grain-balance areas, green agricultural technology and management modes should be introduced.

Mechanism of green production decision-making under the improved theory of planned behavior framework for new agrarian business entities

ZHAO Xiaoying, ZHENG Jun, ZHANG Mingyue, LI Huahua

2021, 29(9): 1636-1648. doi: 10.13930/j.cnki.cjea.210215

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Abstract:
Increasing demand for green agricultural products means that the traditional smallholder farm industry cannot meet customers’ requirements, which has encouraged new agrarian business entities to engage in green production. This study used micro survey data from 293 vegetable family farms in Shandong Province to construct a model and empirically test the decision-making mechanism of green production for new agrarian business entities. Based on the theory of planned behavior (TPB), this study added the decision-making process of “environment → cognition” to the TPB to investigate the premise that the “external environment is consistent and stable,” and constructed a decision-making framework mechanism of “external environment → internal cognition → behavioral intention → behavior implementation”. We tested the decision-making framework using structural equation modeling (SEM) and a multi-group analysis method. The conclusions were as follows: 1) from the perspective of the mechanism of action, the external environment (market incentive and government regulation) impacted behavior implementation through the mediating role of internal cognition (behavior attitude and control cognition) and behavioral intention. The relevant hypotheses were significant, and the decision-making model had a good explanatory power for the pre-, during-, and post-green production behavior implementation of vegetable family farms. 2) The influence effects of market incentive, government regulation, behavior attitude, control cognition, and behavior intention were 0.393, 0.177, 0.260, 0.423, and 0.296, respectively. Between the external environmental factors, market incentive was more important than government regulation; while between the internal cognitive factors, control cognition was more important than behavior attitude. Overall, market incentives and control cognition had the greatest effects, followed by behavior and attitude. There were two important decision-making paths: market incentive → control cognition → behavior implementation and market incentive → behavior attitude → behavior implementation. 3) As per factor loading, the load coefficients of industrial cooperation and consumption demand, ecological compensation and technical training, economic value cognition, and behavioral obstacle cognition were the key factors of market incentive, government regulation, behavior attitude, and control cognition, which were important factors in forming the internal cognition of the external environment. Combined with the effects of the potential variables, more attention should be given to the influence of industrial cooperation, consumer demand, behavior obstacle cognition, and economic value cognition on the implementation of green production behavior. 4) The green production decision-making mechanism of family farms with different scales and number of generations of farmers differed. The behavioral intention of small farms did not have a significant impact on behavior implementation, and the behavior attitude of the older generation and small farms did not have a significant effect on behavioral intention. The behavior attitude of large farms did not have a significant effect on behavior implementation, and government regulations did not have a significant effect on behavior and attitude of small farms. Therefore, we should strengthen policy guidance and support for cultivating the market environment, reducing endowment constraints, enhancing economic performance, and rationalizing the decision-making mechanisms to promote green transformation for different types of family farms.

2021 Vol. 29, No. 9