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    农业生态环境-氮素合辑Agro-ecosystem & Environment—Nitrogen

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    Closing the nitrogen use efficiency gap and reducing the environmental impact of wheat-maize cropping on smallholder farms in the Guanzhong Plain, Northwest China
    LÜ Feng-lian, HOU Miao-miao, ZHANG Hong-tao, Asif Khan, Muhammad Ayaz, QIANGJIU Ciren, HU Chang-lu, YANG Xue-yun, SUN Ben-hua, ZHANG Shu-lan
    2019, 18 (1): 169-178.   DOI: 10.1016/S2095-3119(18)61948-3
    Abstract266)      PDF in ScienceDirect      
    A high crop yield with the minimum possible cost to the environment is generally desirable.  However, the complicated relationships among crop production, nitrogen (N) use efficiency and environmental impacts must be clearly assessed.  We conducted a series of on-farm N application rate experiments to establish the linkage between crop yield and N2O emissions in the Guanzhong Plain in Northwest China.  We also examined crop yield, partial factor productivity of applied N (PFPN) and reactive N (Nr) losses through a survey of 1 529 and 1 497 smallholder farms that grow wheat and maize, respectively, in the region.  The optimum N rates were 175 and 214 kg ha−1 for winter wheat and summer maize, respectively, thereby achieving the yields of 6 799 and 7 518 kg ha−1, correspondingly, with low N2O emissions based on on-farm N rate experiments.  Among the smallholder farms, the average N application rates were 215 and 294 kg ha−1 season−1, thus producing 6 490 and 6 220 kg ha−1 of wheat and maize, respectively.  The corresponding PFPN values for the two crops were 36.8 and 21.2 kg N kg−1, and the total N2O emissions were 1.50 and 3.88 kg ha−1, respectively.  High N balance, large Nr losses and elevated N2O emissions could be explained by the overdoses of N application and low grain yields under the current farming practice.  The crop yields, N application rates, PFPN and total N2O for wheat and maize were 18 and 24% higher, 42 and 37% less, 75 and 116% higher, and 42 and 47% less, correspondingly, in the high-yield and high-PFPN group than in the average smallholder farms.  In conclusion, closing the PFPN gap between the current average and the value for the high-yield and high-PFPN group would increase crop production and reduce Nr losses or the total N2O emissions for the investigated cropping system in Northwest China.
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    Strategies for timing nitrogen fertilization of pear trees based on the distribution, storage, and remobilization of 15N from seasonal application of (15N H4)2SO4
    JIANG Hai-bo, LI Hong-xu, ZHAO Ming-xin, MEI Xin-lan, KANG Ya-long, DONG Cai-xia, XU Yang-chun
    2020, 19 (5): 1340-1353.   DOI: 10.1016/S2095-3119(19)62758-9
    Abstract83)      PDF in ScienceDirect      
    In order to improve the management of nitrogen (N) fertilization in pear orchards, we investigated the effects of application timing on the distribution, storage, and remobilization of N in mature pear trees in a field experiment at Jingtai County, Gansu Province, China.  Nine trees were selected for the experiment and each received equal aliquots of 83.33 g N in the autumn, spring, and summer, with 15N-labeled (NH4)2SO4 used in one of the aliquots each season.  Results showed that the (15NH4)2SO4 applied in the autumn remained in the soil during the winter.  In the following spring this N was absorbed and rapidly remobilized into each organ, especially new organs (leaves, fruit and new shoots).  The 15N supplied in spring was rapidly transported to developing fruit between the young fruit and fruit enlargement stages.  15N from the summer application of fertilizer was mainly stored in the coarse roots over the winter, then was mobilized to support growth of new organs in spring.  In conclusion, for pear trees we recommend that the autumn application of N-fertilizer be soon after fruit harvest in order to increase N stores in fine roots.  Spring application should be between full bloom and the young fruit stages to meet the high N demands of developing fruit.  Summer application of fertilizer at the fruit enlargement stage does not contemporaneously affect the growth of pears, but increases the N stored in coarse roots, and in turn the amount available for remobilization in spring.
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    The effects of water and nitrogen on the roots and yield of upland and paddy rice
    ZHANG Ya-jie, XU Jing-nan, CHENG Ya-dan, WANG Chen, LIU Gao-sheng, YANG Jian-chang
    2020, 19 (5): 1363-1374.   DOI: 10.1016/S2095-3119(19)62811-X
    Abstract76)      PDF in ScienceDirect      
    It is of great significance to study the root characteristics of rice to improve water and nitrogen (N) use efficiency and reduce environmental pollution.  This study investigated whether root traits and architecture of rice influence grain yield, as well as water and N utilization efficiency.  An experiment was conducted using the upland rice cultivar Zhonghan 3 (a japonica cultivar) and paddy rice cultivar Huaidao 5 (also a japonica cultivar) using three N levels, namely, 2 g urea/pot (low amount, LN), 3 g urea/pot (normal amount, NN), and 4 g urea/pot (high amount, HN), and three soil water potentials (SWPs, namely, well-watered (0 kPa), mildly dried (–20 kPa) and severely dried (–40 kPa).  The results showed that with decreasing SWP, the percentage of upland rice roots increased in the 0–5 cm tillage layer, and decreased in the 5–10 and 10–20 cm tillage layers, whereas paddy rice roots showed the opposite trend.  With increasing amounts of N, the yield of upland and paddy rice increased, and the percentage of root volume ratios of the two rice cultivars in the 0–5 and 5–10 cm tillage layers increased, whereas that in the 10–20 cm tillage layer decreased.  The roots of upland rice are mainly distributed in the 10–20 cm tillage layer, whereas most paddy rice roots are in the 0–5 cm tillage layer.  These results indicate that the combination of −20 kPa SWP and NN in upland rice and 0 kPa SWP and LN in paddy rice promotes the growth of the root system during the middle and late stages, which in turn may decrease the requirements for water and N fertilizer and increase rice yield. 
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    Effects of nitrogen application rates and irrigation regimes on grain yield and water use efficiency of maize under alternate partial rootzone irrigation
    QI Dong-liang, HU Tian-tian, SONG Xue
    2020, 19 (11): 2792-2806.   DOI: 10.1016/S2095-3119(20)63205-1
    Abstract98)      PDF in ScienceDirect      
    Faced with the scarcity of water resources and irrational fertilizer use, it is critical to supply plants with water and fertilizer in a coordinated pattern to improve yield with high water use efficiency (WUE).  One such method, alternate partial root-zone irrigation (APRI), has been practiced worldwide, but there is limited information on the performance of different irrigation regimes and nitrogen (N) rates under APRI.  The objectives of this study were to investigate the effects of varying irrigation regimes and N rates on shoot growth, grain yield and WUE of maize (Zea mays L.) grown under APRI in the Hexi Corridor area of Northwest China in 2014 and 2015.  The three N rates were 100, 200 and 300 kg N ha–1, designated N1, N2 and N3, respectively.  The three irrigation regimes of 45–50%, 60–65% and 75–80% field capacity (FC) throughout the maize growing season, designated W1, W2 and W3, respectively, were applied in combination with each N rate.  The results showed that W2 and W3 significantly increased the plant height, stem diameter, crop growth rate, chlorophyll SPAD value, net photosynthetic rate (Pn), biomass, grain yield, ears per ha, kernels per cob, 1 000-kernel weight, harvest index, evapotranspiration and leaf area index (LAI) compared to W1 at each N rate.  The N2 and N3 treatments increased those parameters compared to N1 in each irrigation treatment.  Increasing the N rate from the N2 to N3 resulted in increased biomass and grain yield under W3 while it had no impact on those under the W1 and W2 treatments.  The W3N3 and W2N2 and W2N3 treatments achieved the greatest and the second-greatest biomass and grain yield, respectively.  Increasing the N rate significantly enhanced the maximum LAI (LAI at the silking stage ) and Pn under W3, suggesting that the interaction of irrigation and fertilizer N management can effectively improve leaf growth and development, and consequently provide high biomass and grain yield of maize.  The W2N2, W2N3 and W3N3 treatments attained the greatest WUE among all the treatments.  Thus, either 60–65% FC coupled with 200–300 kg N ha–1 or 75–80% FC coupled with 300 kg N ha–1 is proposed as a better pattern of irrigation and nitrogen application with positive regulative effects on grain yield and WUE of maize under APRI in the Hexi Corridor area of Northwest China and other regions with similar environments.  These results can provide a basis for in-depth understanding of the mechanisms of grain yield and WUE to supply levels of water and nitrogen.
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    Nitrogen release and re-adsorption dynamics on crop straw residue during straw decomposition in an Alfisol
    LI Ji-fu, ZHONG Fang-fang
    2021, 20 (1): 248-259.   DOI: 10.1016/S2095-3119(20)63238-5
    Abstract87)      PDF in ScienceDirect      
    Returning crop straw to the field not only improves the nitrogen (N) supplying capacity and N retention of soil but also decreases the amount of rural organic waste and prevents air pollution.  Therefore, understanding the mechanisms of the N release and re-adsorption dynamics on crop straw residue during straw decomposition in agricultural soil is important, and this understanding can help us strengthen N fertilizer management during the crop growth period.  An on-farm incubation experiment was conducted in the Jianghan Plain in Central China under flooded conditions using the nylon mesh bag method.  Results showed that the decomposition rate of crop straw was much faster at the beginning of the incubation stage, whereas it was steady during the later stage with no observed differences among the three types of crop straw.  After 120 d of incubation, the cumulative decomposition proportion of rice straw, wheat straw and rape straw was 72.9, 56.2, and 66.9%, respectively.  The proportion of N that released from the three crop straws was 52.0, 54.4 and 54.9%, respectively.  The zeta potentials and Brunauer, Emmett and Teller (BET) surface area of the rice, wheat and rape straw residues increased gradually as the decomposition period progressed.  The water adsorption capacity of the rice straw was significantly affected during the decomposition period.  The saturated water adsorption capacity of rice straw was the highest at 30 d of decomposition (4.17 g g–1) and then decreased slightly.  The saturated water adsorption of wheat and rape straws reached the lowest value at 30 d and then gradually increased and became stable.  All the results demonstrated that crop straw and straw residue can re-adsorb NH4+ ions from the surrounding solution.  The re-adsorption was affected by the decomposition period and concentration of exogenous NH4+ and was independent of the crop species via the combined efforts of physical and chemical adsorption, ion exchange and water retention on residue surfaces.  Future studies will focus on straw returning and N fertilizer application at different levels of moisture content of the soil reduce potential negative effects such as water-logging and excess N caused by the straw substrate.
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    Synergistic effect of Si and K in improving the growth, ion distribution and partitioning of Lolium perenne L. under saline-alkali stress
    FAN Yuan, SHEN Wu-yan, Pino VANESSA, CHENG Fang-qin
    2021, 20 (6): 1660-1673.   DOI: 10.1016/S2095-3119(20)63277-4
    Abstract88)      PDF in ScienceDirect      
    The application of Si or K has proven to be beneficial for the growth of plants under saline-alkali stress.  However, the synergistic effect of Si and K in improving the growth, ion distribution, and partitioning in Lolium perenne L. under saline-alkali stress remains unclear.  In this study, the growth characteristics and ion-selective absorption of ryegrass (Lolium perenne L.) exposed to different levels of saline-alkali stress were evaluated.  The growth parameters of ryegrass were significantly improved when Si was applied by itself or coupled with K under low saline-alkali stress.  Under a high saline-alkali level, only simultaneous application of Si and K could significantly improve the growth of ryegrass.  When Si and K were applied together, the K+/Na+ and Ca2+/Na+ ratios in root, stem, and leaf of ryegrass were maximally improved as compared to the individual treatments and control.  The K+ and Ca2+ concentrations in the vacuole, cell wall, and organelle of leaf were increased dramatically.  This improvement was due to the ability of applied ions to compete with Na+, allowing the plant to maintain osmotic potential and leaf water content.  The concentration of Na+ was significantly reduced when Si and K were applied and mainly concentrated in the soluble fraction and cell wall.  The Si concentration in ryegrass increased markedly by the combined application of Si and K, and most of it was accumulated in the cell wall and soluble fraction, which could help in chlorophyll synthesis, reduce membrane injury, and increase water absorption under saline-alkali stress.  This study emphasized the advantage of Si and/or K on the growth of plants under different saline-alkaline levels and provided a guide for the production of Si-K fertilizer and its application in saline-alkali soil. 
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    Nitrogen acquisition, fixation and transfer in maize/alfalfa intercrops are increased through root contact and morphological responses to interspecies competition
    SHAO Ze-qiang, ZHENG Cong-cong, Johannes A. POSTMA, LU Wen-long, GAO Qiang, GAO Ying-zhi, ZHANG Jin-jing
    2021, 20 (8): 2240-2254.   DOI: 10.1016/S2095-3119(20)63330-5
    Abstract104)      PDF in ScienceDirect      
    Nitrogen (N) fixation by legumes and nitrogen transfer to cereals have been considered as important pathways for overyielding and higher N use efficiency in cereal/legume intercropping systems.  However, the extent to which root morphology contributes to N fixation and transfer is unclear.  A two-factorial greenhouse experiment was conducted to quantify the N fixation, transfer and root morphology characteristics of the maize/alfalfa intercropping system in two consecutive years using the 15N-urea leaf labeling method, and combining two N levels with three root separation techniques.  N application could inhibit N fixation and transfer in a maize/alfalfa intercropping system.  Irrespective of the N application level, compared with plastic sheet separation (PSS), no separation (NS) and nylon mesh separation (NNS) significantly increased the total biomass (36%) and total N content (28%), while the N fixation rate also sharply increased by 75 to 134%, and the amount of N transferred with no root barrier was 1.24–1.42 times greater than that with a mesh barrier.  Redundancy analysis (RDA) showed that the crown root dry weight (CRDW) of maize and lateral root number (LRN) of alfalfa showed the strongest associations with N fixation and transfer.  Our results highlight the importance of root contact for the enhancement of N fixation and transfer via changes in root morphology in maize/alfalfa intercropping systems, and the overyielding system was achieved via increases in maize growth, at the cost of smaller decreases in alfalfa biomass production.
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    Fate of low-molecular-weight organic phosphorus compounds in the P-rich and P-poor paddy soils
    LI Bao-zhen, Anna GUNINA, Mostafa ZHRAN, Davey L. JONES, Paul W. HILL, HU Ya-jun, GE Ti-da, WU Jin-shui
    2021, 20 (9): 2526-2534.   DOI: 10.1016/S2095-3119(20)63310-X
    Abstract73)      PDF in ScienceDirect      
    Continuous application of organic fertilizers can cause accumulation of organic phosphorus (P) in soil, especially in the low-molecular-weight organic phosphorus (LMWOP) forms.  This organic P pool represents a potentially important source of P for both plants and microorganisms.  To understand the effect of long-term fertilization (30 years) (P-rich soil) vs. fallowing (P-poor soil) on the bioavailability and fate of LMWOP in subtropical paddy soils, we determined the sorption and mineralization of 14C-labeled adenosine, adenosine monophosphate (AMP), adenosine diphosphate (ADP), and adenosine triphosphate (ATP) in each soil.  The contents of carbon, nitrogen, and P in the P-rich soil were more than two times greater than those in the P-poor soil.  The mineralization rates of the LMWOP compounds were faster in the P-rich soil compared to the P-poor soil, and followed the order AMP>ADP>ATP.  Using sterilized soil, all forms of adenosine-P were strongly sorbed  to the solid phase and reached saturation in a short time, with the adsorbance increasing with the number of phosphate groups.  We concluded that the mineralization of LMWOP compounds was repressed slightly by sorption to the solid phase, but only in the short term.  Thus, LMWOP compounds serve as readily available sources of C for microorganisms, making P available for themselves as well as for the plants.  However, P accumulation and the progressive saturation of the P sorption sites in highly fertile soils may increase the potential risk of P runoff. 
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    Food safety inspection and the adoption of traceability in aquatic wholesale markets: A game-theoretic model and empirical evidence
    JIN Cang-yu, Retsef LEVI, LIANG Qiao, Nicholas RENEGAR, ZHOU Jie-hong
    2021, 20 (10): 2807-2819.   DOI: 10.1016/S2095-3119(21)63624-9
    Abstract96)      PDF in ScienceDirect      
    Supply chain traceability is key to reduce food safety risks, since it allows problems to be traced to their sources.  Moreover, it allows regulatory agencies to understand where risk is introduced into the supply chain, and offers a major disincentive for upstream agricultural businesses engaging in economically motivated adulteration.  This paper focuses on the aquatic supply chain in China, and seeks to understand the adoption of traceability both through an analytical model, and empirical analysis based on data collected through an extensive (largest ever) field survey of Chinese aquatic wholesale markets.  The field survey includes 76 managers and 753 vendors, covering all aquatic wholesale markets in Zhejiang and Hunan provinces.  The analytical and empirical results suggest that the adoption of traceability among wholesale market vendors is significantly associated with inspection intensity, their individual history of food safety problems, and their risk awareness.  The effect of inspection intensity on traceability adoption is stronger in markets which are privately owned than in markets with state/collective ownership.  The analysis offers insights into the current state of traceability in China.  More importantly, it suggests several hypothesized factors that might affect the adoption of traceability and could be leveraged by regulatory organizations to improve it.
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    Yield performance and optimal nitrogen and phosphorus application rates in wheat and faba bean intercropping
    XIAO Jing-xiu, ZHU Ying-an, BAI Wen-lian, LIU Zhen-yang, TANG Li, ZHENG Yi
    2021, 20 (11): 3012-3025.   DOI: 10.1016/S2095-3119(20)63489-X
    Abstract122)      PDF in ScienceDirect      
    Yield performance in cereal and legume intercropping is related to nutrient management, however, the yield response of companion crops to nitrogen (N) input is inconclusive and only limited efforts have focused on rationed phosphorous (P) fertilization.  In this study, two multi-year field experiments were implemented from 2014–2019 under identical conditions.  Two factors in a randomized complete block design were adopted in both experiments.  In field experiment 1, the two factors included three planting patterns (mono-cropped wheat (MW), mono-cropped faba bean (MF), and wheat and faba bean intercropping (W//F)) and four N application rates (N0, 0 kg N ha–1; N1, 90 and 45 kg N ha–1 for wheat and faba beans, respectively; N2, 180 and 90 kg N ha–1 for wheat and faba beans, respectively; and N3, 270 and 135 kg N ha–1 for wheat and faba beans, respectively).  In field experiment 2, the two factors included three P application rates (P0, 0 kg P2O5 ha–1; P1, 45 kg P2O5 ha–1; and P2, 90 kg P2O5 ha–1) and the same three planting patterns (MW, MF, and W//F).  The yield performances of inter- and mono-cropped wheat and faba beans under different N and P application rates were analyzed and the optimal N and P rates for intercropped wheat (IW) and MW were estimated.  The results revealed that intercropping favored wheat yield and was adverse to faba bean yield.  Wheat yield increased by 18–26%, but faba bean yield decreased by 5–21% in W//F compared to MW and MF, respectively.  The stimulated IW yield drove the yield advantage in W//F with an average land equivalent ratio (LER) of 1.12.  N and P fertilization benefited IW yield, but reduced intercropped faba bean (IF) yield.  Nevertheless, the partial LER of wheat (pLERwheat) decreased with increasing N application rates, and the partial LER of faba bean (pLERfaba bean) decreased with increasing P application rates.  Thus, LER decreased as N input increased and tended to decline as P rates increased.  IW maintained a similar yield as MW, even under reduced 40–50% N fertilizer and 30–40% P fertilizer conditions.  The estimated optimum N application rates for IW and MW were 150 and 168 kg ha–1, respectively, and 63 and 62 kg ha–1 for P2O5, respectively.  In conclusion, W//F exhibited yield advantages due to stimulated IW yield, but the intercropping yield benefit decreased as N and P inputs increased.  Thus, it was concluded that modulated N and P rates could maximize the economic and ecological functions of intercropping.  Based on the results, rates of 150 kg N ha–1 and 60 kg P2O5 ha–1 are recommended for IW production in southwestern China and places with similar conditions.
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    Distribution and accumulation of zinc and nitrogen in wheat grain pearling fractions in response to foliar zinc and soil nitrogen applications
    ZHANG Pan-pan, CHEN Yu-lu, WANG Chen-yang, MA Geng, LÜ Jun-jie, LIU Jing-bao, GUO Tian-cai
    2021, 20 (12): 3277-3288.   DOI: 10.1016/S2095-3119(20)63491-8
    Abstract108)      PDF in ScienceDirect      
    Increasing zinc (Zn) concentration in wheat grain is important to minimize human dietary Zn deficiency.  This study aimed to investigate the effect of foliar Zn and soil nitrogen (N) applications on the accumulation and distribution of N and Zn in grain pearling fractions, N remobilization, and the relationships between nutrient concentration in the vegetative tissues and grain or its fractions in two cropping years in the North China Plain.  The results showed a progressive decrease in N and Zn concentrations from the outer to the inner parts of grain, with most of the accumulation in the core endosperm.  Foliar Zn application significantly increased N concentration in the pericarp, and soil N application increased N concentration in each grain fraction.  Both treatments significantly increased core endosperm Zn concentration.  Foliar Zn had no effect on grain N and Zn distribution.  Soil N application made N concentrated in the aleurone, promoted Zn translocation to the core endosperm and also increased N remobilization and its efficiency from the shoot to the grain, but no improved contribution to grain was found.  N concentration in grain and its fractions were positively correlated with N in vegetative organs at anthesis and maturity, while positive correlations were obtained between N concentration in the pericarp and progressive central area of the endosperm and Zn concentration in the core endosperm.  Thus, foliar Zn and soil N applications effectively increased yield and N and Zn concentrations in the wheat grain, particularly in the endosperm, and could be promising strategies to address Zn deficiency.
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    Comparison of nitrogen losses by runoff from two different cultivating patterns in sloping farmland with yellow soil during maize growth in Southwest China 
    HE Shu-qin, MA Rui, WANG Na-na, WANG Shuang, LI Ting-xuan, ZHENG Zi-cheng
    2022, 21 (1): 222-234.   DOI: 10.1016/S2095-3119(20)63496-7
    Abstract97)      PDF in ScienceDirect      
    The loss of N in farmland is an important cause of agricultural non-point source pollution, which seriously impacts the aquatic environment.  A two-year (2017–2018) experiment was conducted to investigate the characteristics of runoff and N losses under different tillage practices.  Taking downslope ridge planting and cross ridge planting as the experimental treatments, the characteristics of surface runoff, interflow, and N losses in sloping farmlands with yellow soil were studied throughout the maize growth period.  As the rainfall increased, the surface runoff and interflow also increased.  The surface runoff and N losses in the surface runoff of downslope ridge planting were significantly higher than those of cross ridge planting.  The interflow volumes and N losses in the 0–20 and 20–40 cm soil layers of the cross ridge planting were significantly higher than those of the downslope ridge planting.  The total N (TN) losses from surface runoff accounted for 54.95–81.25% of the N losses from all pathways.  Therefore, we inferred that surface runoff is the main pathway of N losses.  Dissolved total N (DTN) was the main form of N loss under different tillage measures, as it accounted for 55.82–94.41% of the TN losses, and dissolved organic N accounted for 52.81–87.06% of the DTN losses.  Thus, we inferred that dissolved N is the main form of N loss.  Future research must focus on the prevention and control of the N losses during the maize seedling stage to reduce the environmental pollution caused by ammonium N through runoff.
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    Grain zinc and iron concentrations of Chinese wheat landraces and cultivars and their responses to foliar micronutrient applications
    JIANG Li-na, MA Jing-li, WANG Xiao-jie, LIU Gang-gang, ZHU Zhao-long, QI Chen-yang, ZHANG Ling-fang, LI Chun-xi, WANG Zhi-min, HAO Bao-zhen
    2022, 21 (2): 532-541.   DOI: 10.1016/S2095-3119(21)63614-6
    Abstract157)      PDF in ScienceDirect      
    Grain zinc (Zn) and iron (Fe) concentrations and their responses to foliar application of micronutrients in 28 Chinese wheat landraces and 63 cultivars were investigated in a two-year field experiment.  The average grain Zn and Fe concentrations were 41.8 mg kg–1 (29.0−63.3 mg kg–1) and 39.7 mg kg–1 (27.9−67.0 mg kg–1), respectively.  Compared with cultivars, landraces had greater grain Zn (11.0%) and Fe (4.8%) concentrations but lower harvest index (HI), grain weight per spike (GWS), grain number per spike (GNS) and thousand grain weight (TGW).  Both Zn and Fe concentrations were negatively and significantly correlated with HI, GWS, and GNS, while showed a poor association with TGW, suggesting that lower HI, GWS, and GNS, but not TGW, accounted for higher Zn and Fe concentrations for landraces than for cultivars.  Grain Zn concentrations of both cultivars and landraces significantly increased after foliar Zn spray and the increase was two-fold greater for landraces (12.6 mg kg–1) than for cultivars (6.4 mg kg–1).  Foliar Fe spray increased grain Fe concentrations of landraces (3.4 mg kg–1) and cultivars (1.2 mg kg–1), but these increases were not statistically significant.  This study showed that Chinese wheat landraces had higher grain Zn and Fe concentrations than cultivars, and greater increases occurred in grain Zn concentration than in grain Fe concentration in response to fertilization, suggesting that Chinese wheat landraces could serve as a potential genetic source for enhancing grain mineral levels in modern wheat cultivars.

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    Statistical analysis of nitrogen use efficiency in Northeast China using multiple linear regression and random forest
    LIU Ying-xia, Gerard B. M. HEUVELINK, Zhanguo BAI, HE Ping, JIANG Rong, HUANG Shao-hui, XU Xin-peng
    2022, 21 (12): 3637-3657.   DOI: 10.1016/j.jia.2022.08.054
    Abstract233)      PDF in ScienceDirect      

    Understanding the spatial-temporal dynamics of crop nitrogen (N) use efficiency (NUE) and the relationship with explanatory environmental variables can support land-use management and policymaking.  Nevertheless, the application of statistical models for evaluating the explanatory variables of space-time variation in crop NUE is still under-researched.  In this study, stepwise multiple linear regression (SMLR) and Random Forest (RF) were used to evaluate the spatial and temporal variation of NUE indicators (i.e., partial factor productivity of N (PFPN); partial nutrient balance of N (PNBN)) at county scale in Northeast China (Heilongjiang, Liaoning and Jilin provinces) from 1990 to 2015.  Explanatory variables included agricultural management practices, topography, climate, economy, soil and crop types.  Results revealed that the PFPN was higher in the northern parts and lower in the center of the Northeast China and PNBN increased from southern to northern parts during the 1990–2015 period.  The NUE indicators decreased with time in most counties during the study period.  The model efficiency coefficients of the SMLR and RF models were 0.44 and 0.84 for PFPN, and 0.67 and 0.89 for PNBN, respectively.  The RF model had higher relative importance of soil and climatic covariates and lower relative importance of crop covariates compared to the SMLR model.  The planting area index of vegetables and beans, soil clay content, saturated water content, enhanced vegetation index in November & December, soil bulk density, and annual minimum temperature were the main explanatory variables for both NUE indicators.  This is the first study to show the quantitative relative importance of explanatory variables for NUE at a county level in Northeast China using RF and SMLR.  This novel study gives reference measurements to improve crop NUE which is one of the most effective means of managing N for sustainable development, ensuring food security, alleviating environmental degradation and increasing farmer’s profitability.

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    Transfer characteristics of nitrogen fixed by leguminous green manure crops when intercropped with maize in northwestern China
    LIU Rui, ZHOU Guo-peng, CHANG Dan-na, GAO Song-juan, HAN Mei, ZHANG Jiu-dong, SUN Xiao-feng, CAO Wei-dong
    2022, 21 (4): 1177-1187.   DOI: 10.1016/S2095-3119(21)63674-2
    Abstract109)      PDF in ScienceDirect      
    To ascertain the possibility of cultivating maize using biological nitrogen fixation (BNF) by leguminous green manure crops in maize/leguminous green manure intercropping systems, BNF and nitrogen (N) transfer were studied in Xining and Wuwei, two typical northwestern Chinese cities.  The experimental treatments included monocultured maize, monocultured green manures (hairy vetch and common vetch), and their intercropping systems.  The proportions of N derived from the atmosphere (%Ndfa) in intercropping systems were not significantly different from that in monocultured green manure systems at either experimental site, except for that in hairy vetch (HV) in Xining.  The amount of N derived from the atmosphere (Ndfa) of common vetch (CV) significantly decreased from 1.16 and 1.10 g/pot in monoculture to 0.77 and 0.55 g/pot when intercropped with maize, in Xining and Wuwei, respectively, and the Ndfa of HV when intercropped significantly decreased from 1.02 to 0.48 g/pot in Xining.  In the intercropping systems in Xining and Wuwei, the amounts of N transferred (Ntransfer) from CV to maize were 21.54 and 26.81 mg/pot, accounting for 32.9 and 5.9% respectively of the N accumulation in maize, and the values of Ntransfer from HV to maize were 39.61 and 46.22 mg/pot, accounting for 37.0 and 23.3%, respectively, of the N accumulation in maize.  Path analysis showed that soil nutrient and green manure biomass were mainly related to Ndfa, and that δ15N had a primary relationship with Ntransfer.  We found that 5.9–37.0% of N accumulation in maize was transferred from green manures, and that the N transfer ability to maize of HV was higher than that of CV.  In conclusion, intercropping with leguminous green manures provided a feasible way for maize to effectively utilize biologically fixed N.
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    Increasing soil microbial biomass nitrogen in crop rotation systems by improving nitrogen resources under nitrogen application
    XING Ting-ting, CAI An-dong, LU Chang-ai, YE Hong-ling, WU Hong-liang, HUAI Sheng-chang, WANG Jin-yu, XU Ming-gang, LIN Qi-mei
    2022, 21 (5): 1488-1500.   DOI: 10.1016/S2095-3119(21)63673-0
    Abstract130)      PDF in ScienceDirect      
    Soil microbial biomass nitrogen (MBN) contains the largest proportion of biologically active nitrogen (N) in soil, and is considered as a crucial participant in soil N cycling.  Agronomic management practices such as crop rotation and mono-cropping systems, dramatically affect MBN in agroecosystems.  However, the influence of crop rotation and mono-cropping in agroecosystems on MBN remains unclear.  A meta-analysis based on 203 published studies was conducted to quantify the effect of crop rotation and mono-cropping systems on MBN under synthetic N fertilizer application.  The analysis showed that crop rotation significantly stimulated the response ratio (RR) of MBN to N fertilization and this parameter reached the highest levels in upland-fallow rotations.  Upland mono-cropping did not change the RR of MBN to N application, however, the RR of MBN to N application in paddy mono-cropping increased.  The difference between crop rotation and mono-cropping systems appeared to be due to the various cropping management scenarios, and the pattern, rate and duration of N addition.  Crop rotation systems led to a more positive effect on soil total N (TN) and a smaller reduction in soil pH than mono-cropping systems.  The RR of MBN to N application was positively correlated with the RR of mineral N only in crop rotation systems and with the RR of soil pH only in mono-cropping systems.  Combining the results of Random Forest (RF) model and structural equation model showed that the predominant driving factors of MBN changes in crop rotation systems were soil mineral N and TN, while in mono-cropping systems the main driving factor was soil pH.  Overall, our study indicates that crop rotation can be an effective way to enhance MBN by improving soil N resources, which promote the resistance of MBN to low pH induced by intensive synthetic N fertilizer application.

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    The Nutrient Expert decision support system improves nutrient use efficiency and environmental performance of radish in North China
    ZHANG Jia-jia, DING Wen-cheng, CUI Rong-zong, LI Ming-yue, Sami ULLAH, HE Ping
    2022, 21 (5): 1501-1512.   DOI: 10.1016/S2095-3119(21)63660-2
    Abstract98)      PDF in ScienceDirect      
    Excessive fertilization has led to nutrient use inefficiency and serious environmental consequences for radish cultivation in North China.  The Nutrient Expert (NE) system is a science-based, site-specific fertilization decision support system, but the updated NE system for radish has rarely been evaluated.  This study aims to validate the feasibility of NE for radish fertilization management from agronomic, economic, and environmental perspectives.  A total of 46 field experiments were conducted over four seasons from April 2018 to November 2019 across the major radish growing regions in North China.  The results indicated that NE significantly reduced N, P2O5, and K2O application rates by 98, 110, and 47 kg ha−1 relative to those in the farmers’ practice (FP), respectively, and reduced N and P2O5 inputs by 48 and 44 kg ha−1, respectively, while maintaining the same K2O rate as soil testing (ST).  Relative to FP and ST, NE significantly increased radish yield by 2.7 and 2.6 t ha−1 (4.2 and 4.0%) and net returns by 837 and 432 USD ha−1, respectively.  On average, NE significantly improved the agronomic efficiency (AE) of N, P, and K (relative to FP and ST) by 42.4 and 31.0, 67.4 kg kg−1 and 50.9, and 20.3 and 12.3 kg kg−1; enhanced the recovery efficiency (RE) of N, P, and K by 11.4 and 7.0, 14.1 and 7.5, and 11.3 and 6.3 percentage points; and increased the partial factor productivity (PFP) of N, P, and K by 162.9 and 96.8, 488.0 and 327.3, and 86.9 and 22.4 kg kg−1, respectively.  Furthermore, NE substantially reduced N and P2O5 surpluses by 105.1 and 115.1 kg ha−1, respectively, and decreased apparent N loss by 110.8 kg ha−1 compared to FP.  These results indicated that the NE system is an effective and feasible approach for improving NUE and promoting cleaner radish production in North China.

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