INTERCROPPING: FEED MORE PEOPLE AND BUILD MORE SUSTAINABLE AGROECOSYSTEMS

• Intercropping is a useful practice when agricultural sustainability is emphasized.• We integrate biodiversity-ecosystem functioning and intercropping.• Intercropping optimizes ecosystem services such as stabilizing yield and reducing use of chemicals.• Intercropping benefits are attributed partly to complementarity and selection effects.• Application of ecological principles is key to sustainable agricultural development.Intercropping is a traditional farming system that increases crop diversity to strengthen agroecosystem functions while decreasing chemical inputs and minimizing negative environmental effects of crop production. Intercropping is currently considerable interest because of its importance in sustainable agriculture. Here, we synthesize the factors that make intercropping a sustainable means of food production by integrating biodiversity of natural ecosystems and crop diversity. In addition to well-known yield increases, intercropping can also increase yield stability over the long term and increase systemic resistance to plant diseases, pests and other unfavorable factors (e.g. nutrient deficiencies). The efficient use of resources can save mineral fertilizer inputs, reduce environmental pollution risks and greenhouse gas emissions caused by agriculture, thus mitigating global climate change. Intercropping potentially increases above- and below-ground biodiversity of various taxa at field scale, consequently it enhances ecosystem services. Complementarity and selection effects allow a better understanding the mechanisms behind enhanced ecosystem functioning. The development of mechanization is essential for large-scale application of intercropping. Agroecosystem multifunctionality and soil health should be priority topics in future research on intercropping.     

不同配置对辽西玉米‖花生间作系统氮素吸收利用的影响

【目的】通过研究不同配置条件下玉米‖花生间作系统地上部氮含量和吸收量,结合间作系统花生结瘤固氮和土壤有效氮分布,明确不同配置下玉米‖花生间作体系对氮素的吸收利用特征,为玉米‖花生间作氮高效利用模式的区域筛选提供依据。【方法】本试验于2015—2016年在国家农业环境阜新观测实验站进行,设置玉米单作（M）、花生单作（P）、2行玉米4行花生间作（M2P4）和4行玉米4行花生间作（M4P4）模式,玉米单作及每种间作模式下设3种不同玉米种植密度（6、9和12株/m²）,共10个处理,分析不同配置（行比和密度）玉米‖花生间作系统氮素吸收利用特征和优势。【结果】与单作相比,间作玉米和花生植株氮浓度变化并不明显,受作物占地比例影响,间作模式下玉米和花生的产量、氮产量均低于相应单作,且氮产量与间作生物产量表现相一致。玉米‖花生间作可以显著提高系统氮的吸收利用（氮吸收当量比NER>1）,且主要归因于玉米的养分吸收优势（pNER_m为0.63—0.80）。随着玉米行比和密度的增加NER也随之增大,其中M4P4模式（NER 1.06—1.22）的氮吸收要显著高于M2P4模式（NER 1.0—1.06）。在玉米‖花生间作系统中,玉米比花生更有竞争力（A_mp>0）,且竞争吸收氮养分能力也更强（CR_mp>1）,M4P4行比以及玉米增密有助于增强玉米对氮营养的竞争,增加系统氮养分吸收优势（△NU>0）以及间作养分对产量的贡献（C）。与玉米间作可促进花生结瘤固氮,M4P4行比配置下花生根瘤数量、单株根瘤重量和单个瘤重均高于M2P4配置,且以中、低密度处理为优。间作系统中土壤有效氮含量（N_min）表现为花生条带土壤N_min高于玉米条带,且单作花生土壤N_min高于间作花生,而单作玉米土壤N_min低于间作玉米。【结论】玉米‖花生间作可显著提高系统氮的吸收利用,其中玉米对系统氮吸收的贡献较大,适度增加玉米行比和密度有助于增加系统氮素吸收当量比、增强玉米对氮营养的竞争以及间作养分对产量的贡献。综合分析认为,本研究中M4P4-6和M4P4-8为玉米‖花生间作较佳配置,玉米花生种间互作对间作系统干物质量和花生生物固氮的促进,以及玉米在吸收氮养分上的强竞争能力是玉米‖花生间作具有氮素吸收利用优势的重要原因。     

EVALUATING QUINOA LODGING RISK AND YIELD UNDER DIFFERENT IRRIGATION THRESHOLDS,NITROGEN RATES AND PLANTING DENSITIES IN NORTH-WESTERN CHINA

● A moderate irrigation threshold of −25 kPa gave the greatest actual yield. ● Nitrogen rates of 80−160 kg·ha⁻¹ reduced lodging risk without yield decrease. ● Planting density of 30 plants·m⁻² provided both high yield and lodging resistance. ● A lower-stem lodging index was best for prediction of quinoa lodging risk. Lodging is a major yield-limiting factor of quinoa production. In 2018 and 2019, the orthogonal field experiments were conducted to investigate the responses of quinoa lodging risk and yield to irrigation threshold (soil matric potential of −15, −25 and −55 kPa), nitrogen rate (80, 160 and 240 kg·ha⁻¹) and planting density (20, 30 and 40 plants m⁻²). Results showed that high irrigation thresholds and nitrogen rates significantly (P < 0.05) increased plant height and fresh weight per plant, and high planting densities reduced stem diameter and strength, all of those led to significantly ( P < 0.05) high lodging risks. The −15 and −55 kPa treatments gave the lowest actual yield ( P < 0.05) in 2018 and 2019, respectively. Higher lodging rate with a nitrogen rate of 240 kg·ha⁻¹ resulted in a lower actual yield than 80 and 160 kg·ha⁻¹ in both years. Planting density of 30 plants m⁻² gave a significantly (P < 0.05) greater estimated yield than 20 plants m⁻² and had a lower lodging rate than 40 plants m⁻², resulting in the maximum actual yield among planting densities. In conclusion, a moderate irrigation threshold of −25 kPa, a nitrogen rate of 80−160 kg·ha⁻¹ and an intermediate planting density of 30 plants m⁻² were determined to be best for quinoa cultivation in North-western China. In addition, the lower-stem lodging index (quarter plant height) could evaluate lodging risk more accurately than middle-stem (half plant height) or upper-stem (three quarters plant height) lodging indexes.     

PLANT DENSITY,IRRIGATION AND NITROGEN MANAGEMENT: THREE MAJOR PRACTICES IN CLOSING YIELD GAPS FOR AGRICULTURAL SUSTAINABILITY IN NORTH-WEST CHINA

• A relative yield of 70% was obtained under both border and drip irrigation.• Drip irrigation saved water and lowered yield variability compared to border irrigation.• Drip irrigation led to accumulation of soil nitrogen and phosphorus in the root zone.• Relative yield may increase 8% to 10% by optimizing field management.• Plant density, irrigation and nitrogen are major factors closing yield gap in NW China.Agriculture faces the dual challenges of food security and environmental sustainability. Here, we investigate current maize production at the field scale, analyze the yield gaps and impacting factors, and recommend measures for sustainably closing yield gaps. An experiment was conducted on a 3.9-ha maize seed production field in arid north-western China, managed with border and drip irrigation, respectively, in 2015 and 2016. The relative yield reached 70% in both years. However, drip irrigation saved 227 mm irrigation water during a drier growing season compared with traditional border irrigation, accounting for 44% of the maize evapotranspiration (ET). Yield variability under drip irrigation was 12.1%, lower than the 18.8% under border irrigation. Boundary line analysis indicates that a relative yield increase of 8% to 10% might be obtained by optimizing the yield-limiting factors. Plant density and soil available water content and available nitrogen were the three major factors involved. In conclusion, closing yield gaps with agricultural sustainability may be realized by optimizing agronomic, irrigation and fertilizer management, using water-saving irrigation methods and using site-specific management.     

COMPARING PERFORMANCE OF CROP SPECIES MIXTURES AND PURE STANDS

•The literature on intercropping comprises thousands of papers. •Evidence synthesis is needed to develop general conclusions. •Quantitative evidence synthesis requires meaningful comparative performance metrics. •The background, meaning, and limitations of some performance metrics is explained. •Future challenges are identified. Intercropping is the planned cultivation of species mixtures on agricultural land. Intercropping has many attributes that make it attractive for developing a more sustainable agriculture, such as high yield, high resource use efficiency, lower input requirements, natural suppression of pests, pathogens and weeds, and building a soil with more organic carbon and nitrogen. Information is needed which species combinations perform best under different circumstances and which management is suitable to bring out the best from intercropping in a given production situation. The literature is replete with case studies on intercropping from across the globe, but evidence synthesis is needed to make this information accessible. Meta-analysis requires a careful choice of metric that is appropriate for answering the question at hand, and which lends itself for a robust meta-analysis. This paper reviews some metrics that may be used in the quantitative synthesis of literature data on intercropping.     

CHARACTERISTICS OF HERBIVORY/WOUND-ELICITED ELECTRICAL SIGNAL TRANSDUCTION IN TOMATO

• Herbivory and mechanical wounding elicited electrical signals.• Petiole wounding elicited stronger electrical signals than did leaflet wounding.• Leaflet wounding elicited electrical signals and JA signaling within a compound leaf.• GLR3.3 and GLR3.5 mediated leaflet-to-leaflet electrical signal transduction.• JA synthesis and Helicoverpa armigera resistance were reduced in glr3.3/3.5 plants.Electrical signals commonly occur in plants in response to various environmental changes and have a dominant function in plant acclimation. The transduction of wound-elicited electrical signals in the model plant species Arabidopsis has been characterized but the characteristics of electrical signal transduction in response to herbivory or wounding in crop species remain unknown. Here, the features of electrical signals elicited by insect herbivory and wounding in tomato were investigated. Unlike those in Arabidopsis, wounding tomato leaves did not cause leaf-to-leaf electrical signal transduction. In contrast, electrical signals elicited in response to petiole wounding were stronger and more strongly transduced. Leaflet wounding also activated electrical signal transduction and jasmonic acid (JA) signaling within the whole compound leaf. It was also demonstrated that tomato glutamate receptor-like 3.3 (GLR3.3) and GLR3.5 mediated leaflet-to-leaflet electrical signal transduction. Herbivory-induced JA accumulation and Helicoverpa armigera resistance were reduced in glr3.3/3.5 plants. This work reveals the nature of electrical signal transduction in tomato and emphasizes the key roles of GLR3.3 and GLR3.5 in electrical signal transduction and JA signaling activation.     

EXPLORING THE RECYCLING OF MANURE FROM URBAN LIVESTOCK FARMS: A CASE STUDY IN ETHIOPIA

• Livestock manure was the main organic waste in urban and peri-urban areas.• Manure production will increase by a factor of 3–10 between 2015–2050.• Only 13%–38% of excreted N by livestock will be recycled in croplands.• Intensification of urban livestock production greatly increased N surpluses.• Reducing population growth and increasing livestock productivity needed.Urban population growth is driving the expansion of urban and peri-urban agriculture (UPA) in developing countries. UPA is providing nutritious food to residents but the manures produced by UPA livestock farms and other wastes are not properly recycled. This paper explores the effects of four scenarios: (1) a reference scenario (business as usual), (2) increased urbanization, (3) UPA intensification, and (4) improved technology, on food-protein self-sufficiency, manure nitrogen (N) recycling and balances for four different zones in a small city (Jimma) in Ethiopia during the period 2015-2050. An N mass flow model with data from farm surveys, field experiments and literature was used. A field experiment was conducted and N use efficiency and N fertilizer replacement values differed among the five types of composts derived from urban livestock manures and kitchen wastes. The N use efficiency and N fertilizer replacement values were used in the N mass flow model.Livestock manures were the main organic wastes in urban areas, although only 20 to 40% of animal-sourced food consumed was produced in UPA, and only 14 to 19% of protein intake by residents was animal-based. Scenarios indicate that manure production in UPA will increase 3 to 10 times between 2015 and 2050, depending on urbanization and UPA intensification. Only 13 to 38% of manure N will be recycled in croplands. Farm-gate N balances of UPA livestock farms will increase to>1 t·ha⁻¹ in 2050. Doubling livestock productivity and feed protein conversion to animal-sourced food will roughly halve manure N production.Costs of waste recycling were high and indicate the need for government incentives. Results of these senarios are wake-up calls for all stakeholders and indicate alternative pathways.     

辽西半干旱区玉米与花生间作对土地生产力和水分利用效率的影响

【目的】通过对不同行比玉米与花生间作模式中作物产量、土地生产能力及水分利用效率的比较分析,探讨间作模式提高土地生产能力和水分利用效率的机理,提出适合于辽西旱作农业区的玉米与花生间作模式。【方法】试验于2015—2016年在农业部阜新农业环境与保育科学观测试验站进行,设置2行玉米4行花生间作(2M:4P)、4行玉米4行花生间作(4M:4P)和玉米单作(S-M)、花生单作(S-P)4种种植模式,通过研究间作复合系统产量、土地当量比、土壤水分分布和水分当量比等指标来分析玉米花生间作对土地生产力和水分利用效率的影响。【结果】受玉米行比设置和资源竞争影响,玉米与花生间作中玉米和花生的产量较相对应单作产量有不同程度降低;在系统整体收益衡量下,2M:4P和4M:4P间作模式的土地当量比(LER)为1.10—1.24、1.12—1.16,表明间作具有优化利用土地的功能,同时,间作系统中花生的偏土地当量比(LER_P)达到0.41—0.57,显示出豆科作物花生弱化了与禾本科作物玉米搭配间作的劣势;间作复合系统土壤含水量呈单作花生间作花生间作玉米单作玉米的分布特征,表明间作玉米可能会吸收花生条带的土壤水分,降低高耗水作物玉米对自身条带土壤水分的过度消耗来改善间作玉米土壤水分利用环境;2M:4P间作模式的水分当量比(WER)为1.12—1.23,4M:4P间作模式的WER为1.16—1.17,两间作模式的WER均大于1,显著提高了农田水分利用效率。【结论】玉米与花生间作能够改善辽西旱作农业区作物土壤水分利用环境,提高农田土地和水分生产力。2M:4P间作模式在降雨较少年份(2015年)具有一定的土地生产力和水分利用效率优势,而4M:4P间作模式在辽西降雨较多年份(2016年)具有一定的土地生产力和水分利用效率优势,并且4M:4P间作模式在2015—2016年不同降雨变化干扰下的年际差异较小,具有稳产增产的抗气候变化干扰能力。综合分析认为,4M:4P间作模式更适合于辽西旱作农业区。     

ENABLING CROP DIVERSIFICATION TO SUPPORT TRANSITIONS TOWARD MORE SUSTAINABLE EUROPEAN AGRIFOOD SYSTEMS

• Crop diversification is a dynamic pathway towards sustainable agrifood systems.• Technological and institutional barriers restrict uptake of crop diversification.• More coordination and cooperation among agrifood system stakeholders is required.• The European Crop Diversification Cluster calls for multiactor networks.European cropping systems are often characterized by short rotations or even monocropping, leading to environmental issues such as soil degradation, water eutrophication, and air pollution including greenhouse gas emissions, that contribute to climate change and biodiversity loss. The use of diversification practices (i.e., intercropping, multiple cropping including cover cropping and rotation extension), may help enhance agrobiodiversity and deliver ecosystem services while developing new value chains. Despite its benefits, crop diversification is hindered by various technical, organizational, and institutional barriers along value chains (input industries, farms, trading and processing industries, retailers, and consumers) and within sociotechnical systems (policy, research, education, regulation and advisory). Six EU-funded research projects have joined forces to boost crop diversification by creating the European Crop Diversification Cluster (CDC). This Cluster aggregates research, innovation, commercial and citizen-focused partnerships to identify and remove barriers across the agrifood system and thus enables the uptake of diversification measures by all European value-chain stakeholders. The CDC will produce a typology of barriers, develop tools to accompany actors in their transition, harmonize the use of multicriteria assessment indicators, prepare policy recommendations and pave the way for a long-term network on crop diversification.     

Maize/peanut intercropping increases photosynthetic characteristics, ~(13)C-photosynthate distribution,and grain yield of summer maize

Intercropping is used widely by smallholder farmers in developing countries to increase land productivity and profitability. We conducted a maize/peanut intercropping experiment in the 2015 and 2016 growing seasons in Shandong, China. Treatments included sole maize(SM), sole peanut(SP), and an intercrop consisting of four rows of maize and six rows of peanut(IM and IP). The results showed that the intercropping system had yield advantages based on the land equivalent ratio(LER) values of 1.15 and 1.16 in the two years, respectively. Averaged over the two years, the yield of maize in the intercropping was increased by 61.05% compared to that in SM, while the pod yield of peanut was decreased by 31.80% compared to SP. Maize was the superior competitor when intercropped with peanut, and its productivity dominated the yield of the intercropping system in our study. The increased yield was due to a higher kernel number per ear(KNE). Intercropping increased the light transmission ratio(LTR) of the ear layer in the maize canopy, the active photosynthetic duration(APD), and the harvest index(HI) compared to SM. In addition, intercropping promoted the ratio of dry matter accumulation after silking and the distribution of ~(13) C-photosynthates to grain compared to SM. In conclusion, maize/peanut intercropping demonstrated the potential to improve the light condition of maize, achieving enhanced photosynthetic characteristics that improved female spike differentiation, reduced barrenness, and increased KNE. Moreover, dry matter accumulation and ~(13) C-photosynthates distribution to grain of intercropped maize were improved, and a higher grain yield was ultimately obtained.     

HEMIPTERAN-TRANSMITTED PLANT VIRUSES: RESEARCH PROGRESS AND CONTROL STRATEGIES

• Research findings on the insect-virus interaction• Influences of immunity, feeding and microorganisms on virus transmission• Latest applications for virus control strategiesAbout 80% of plant viruses are transmitted by specific insect vectors, especially hemipterans with piercing-sucking mouthparts. Many virus-transmitting insects are also important crop pests that cause considerable losses in crop production. This review summarizes the latest research findings on the interactions between plant viruses and insect vectors and analyzes the key factors affecting insect transmission of plant viruses from the perspectives of insect immunity, insect feeding, and insect symbiotic microorganisms. Additionally, by referring to the latest applications for blocking the transmission of animal viruses, potential control strategies to prevent the transmission of insect-vectored plant viruses using RNAi technology, gene editing technology, and CRISPR/Cas9+ gene-driven technology are discussed.     

YIELD AND FRUIT QUALITY OF ALMOND,PEACH AND PLUM UNDER REGULATED DEFICIT IRRIGATION

• Regulated deficit irrigation was assessed in almond, peach and plum over 3 years.• Fruit-growth slowdown stages are appropriate periods to apply deficit irrigation.• Peach yields were unaffected under a regulated deficit irrigation of 75% ET_C.• Regulated deficit irrigation of 50% ET_C maintained yields of almond and plum.• Fruit quality improved under regulated deficit irrigation.The effects of regulated deficit irrigation (RDI) on the performance of almond cv. Tuono, peach cv. JH-Hall and plum cv. Stanley were assessed on the Saiss Plain (NW, Morocco) over three consecutive growing seasons (2011–2013). Irrigation treatments consisted of a control, irrigation applied to fully satisfy crop water requirements (100% ET_C), and two RDI treatments, irrigation applied to 75% ET_C (RDI-75) and 50% ET_C (RDI-50). These three treatments were applied during fruit-growth slowdown periods corresponding to Stages II and III in almond and Stage II in peach and plum. Yield and fruit quality traits were determined. The effect of RDI differed between species. Yield and fruit size were reduced significantly only in peach under RDI-50. Fruit quality improved in this species in the first year of the experiment, with an increase of sugar/acid ratio and polyphenol content. Plum quality also improved but the effects were significant only in the second and third years. Similar results were recorded in almond kernel, but their epidermal grooves were deeper under RDI-50, and this may have affected their commercial value. It is concluded that water can be saved during the fruit-growth slowdown period by up to 25% in peach and 50% in almond and plum with improvements in fruit quality without affecting total yield.     

DESIGNING DIVERSIFIED CROPPING SYSTEMS IN CHINA: THEORY,APPROACHES AND IMPLEMENTATION

•Agricultural green transformation of China requires restructuring of cropping systems.•Ecosystem services enhanced by crop diversification is key to sustainable agriculture.•Crop diversification improve ecosystem services at field, farm and landscape scales.•Cropping system design should meet regional characteristics and socio-economic demand.Intensive agriculture in China over recent decades has successfully realized food security but at the expense of negative environmental impacts. Achieving green transformation of agriculture in China requires fundamental restructuring of cropping systems. This paper presents a theoretical framework of theory, approaches and implementation of crop diversification schemes in China. Initially, crop diversification schemes require identifying multiple objectives by simultaneously considering natural resources, limiting factors/constraints, and social and economic demands of different stakeholders. Then, it is necessary to optimize existing and/or design novel cropping systems based upon farming practices and ecological principles, and to strengthen targeted ecosystem services to achieve the identified objectives. Next, the resulting diversified cropping systems need to be evaluated and examined by employing experimental and modeling approaches. Finally, a strategic plan, as presented in this paper, is needed for implementing an optimized crop diversification in China based upon regional characteristics with the concurrent objectives of safe, nutritious food production and environmental protection. The North China Plain is used as an example to illustrate the strategic plan to optimize and design diversified cropping systems. The implementation of crop diversification in China will set an example for other countries undergoing agricultural transition, and contribute to global sustainable development.     

INTENSIFICATION OF GRASSLAND-BASED DAIRY PRODUCTION AND ITS IMPACTS ON LAND,NITROGEN AND PHOSPHORUS USE EFFICIENCIES

• Monitoring data of>5000 dairy farms collected and examined in uniform manner. • Environmental performances of farms influenced by government regulations. • N and P surpluses at farm level remained about constant with intensity level. • N and P use efficiencies at farm, herd and soil increased with intensity level. • Accounting for externalization of off-farm feed production affects NUE and PUE. • Ammonia emissions per kg milk decreased with the level of intensification. Many grassland-based dairy farms are intensifying production, i.e., produce more milk per ha of land in response to the increasing demand for milk (by about 2% per year) in a globalized market. However, intensive dairy farming has been implicated for its resources use, ammonia and greenhouse gas emissions, and eutrophication impacts. This paper addresses the question of how the intensity of dairy production relates to N and P surpluses and use efficiencies on farms subjected to agri-environmental regulations. Detailed monitoring data were analyzed from 2858 grassland-based dairy farms in The Netherlands for the year 2015. The farms produced on average 925 Mg·yr⁻¹ milk. Milk production per ha ranged from<10 to>30 Mg·ha⁻¹·yr⁻¹. Purchased feed and manure export strongly increased with the level of intensification. Surpluses of N and P at farm level remained constant and ammonia emissions per kg milk decreased with the level of intensification. In conclusion, N and P surpluses did not differ much among dairy farms greatly differing in intensity due to legal N and P application limits and obligatory export of manure surpluses to other farms. Further, N and P use efficiencies also did not differ among dairy farms differing in intensity provided the externalization of feed production was accounted for. This paper provides lessons for proper monitoring and control of N and P cycling in dairy farming.     

RESPONSE OF WHEAT COMPOSITE CROSS POPULATIONS TO DISEASE AND CLIMATE VARIATION OVER 13 GENERATIONS

• Agronomic performance of wheat populations comparable to modern cultivars.• Performance of populations depends on parental cultivar selection.• Agronomic advantage of populations under particular environmental stresses.• Heterogeneous populations better suited to low-input conditions.Since the F₅ (2005), three winter wheat composite cross populations (CCPs) based on germplasm specifically suitable for low-input conditions were subjected to natural selection under organic and conventional management. In the F₆, each CCP was divided into two parallel populations (12 CCPs in total) and maintained continuously until 2018. Commonly used modern cultivars with different disease susceptibilities were grown alongside to assess the agronomic performance of the CCPs. The organically managed CCPs were comparable in yield and foliar disease resistance to two continuously used reference cultivars, Achat and Capo. In contrast, under conventional management the cv. Capo outyielded the CCPs (Achat was not tested), highlighting the importance of parental cultivar choice for specific management systems. The CCPs were found to be moderately resistant to brown rust and even to the newly emerged stripe rust races prevalent in Europe since 2011. Differences between the CCPs were mainly due to parental genetic background and were significant in the first five generations, but were no longer so in the last five generations. In addition, these differences tended to vary depending on the experimental year and the environmental stresses present. In conclusion, the CCPs despite being derived from older cultivars are able to compete with more recently released reference cultivars under organic farming practices and represent a dynamic germplasm resource.     

INTERFERENCE BY NON-HOST PLANT ROOTS AND ROOT EXUDATES IN THE INFECTION PROCESSES OF PHYTOPHTHORA NICOTIANAE

• The roots of non-host plant interfere infection of Phytophthora nicotianae.• Vanillin and other compounds play key roles in antimicrobial activity of fennel roots.• ROS accumulation is the potentially mechanism involved in inhibition of antimicrobial compounds on P. nicotianae.Crop rotations are widely used because they can significantly reduce the incidence of pests and diseases. The interactions between non-host roots and pathogens may be key in the inhibition of soilborne pathogens in crop rotations. Interactions between fennel (Foeniculum vulgare) roots/root exudates and Phytophthora nicotianae were investigated because of the known allelopathy between fennel and tobacco (Nicotiana tabacum). The effects of the key compounds in the fennel rhizosphere on the mycelial growth and zoospore behavior of P. nicotianae were assessed. The roots of fennel attracted P. nicotianae zoospores and inhibited their motility and the germination of cystospores, with some cystospores rupturing. 4-ethylacetophenone, vanillin and N-formylpiperidine were consistently identified in the fennel rhizosphere and were found to interfere with the infection of P. nicotianae, especially vanillin. Hyphae treated with these compounds produced more abnormal branches and accumulated reactive oxygen species. These interspecific interactions between non-host roots and pathogens were found to be an important factor in the inhibition by fennel of infection by P. nicotianae.     

APPLE SUMO E3 LIGASE MDSIZ1 NEGATIVELY REGULATES DROUGHT TOLERANCE

•MdSIZ1 RNAi transgenic apple trees are drought tolerance than wild type—GL-3.•MdSIZ1 RNAi plants get enhanced ability to keep water and scavenge ROS under drought conditions.•MdSIZ1 may participate in apple drought tolerance by affecting ABA biosynthesis.Drought stress typically causes heavy losses in apple production and uncovering the mechanisms by which apple tolerates drought stress is important in apple breeding. MdSIZ1 is a SUMO (small ubiquitin-like modifier) E3 ligase that promotes SUMO binding to substrate proteins. Here, we demonstrate that MdSIZ1 in apple has a negative relationship with drought tolerance. MdSIZ1 RNAi transgenic apple trees had a higher survival rate after drought stress. During drought stress they had higher leaf water potential, reduced ion leakage, lower H₂O₂ and malondialdehyde contents, and higher catalase activity. In addition, MdSIZ1 RNAi transgenic plants had a higher net photosynthetic rate during the latter period of drought stress. Finally, the transgenic apple trees also altered expression levels of some microRNAs in response to drought stress. Taken together, these results indicate that apple MdSIZ1 negatively regulates drought stress by enhancing leaf water-holding capacity and antioxidant enzyme activity.     

CONCENTRATIONS AND FLUXES OF DISSOLVED NUTRIENTS IN THE YANGTZE RIVER: LONG-TERM TRENDS AND ECOLOGICAL IMPACTS

• Historic trends in nutrient loading and flux in the Yangtze River were analyzed• Decreasing trends in the concentrations and fluxes of DSi were found• Significant increasing trends in DIN and DIP concentrations were observed• The frequency of and area covered by red tide outbreaks substantially increased• Atmospheric deposition become a vital factor influencing DIN loadings and fluxesIntensifying human activity in the Yangtze River basin has substantially increased nutrient concentrations in the Yangtze River Estuary, leading to degradation of the coastal environment. Analysis of nutrient determinations published over the past 50 years reveals a gradual decreasing trend in the concentrations and fluxes of dissolved silicate (DSi). However, both dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphate (DIP) concentrations have increased significantly since the 1970s. The frequency of and area covered by red tide outbreaks have increased greatly during this period, mainly due to changes in nutrient supply ratios [i.e., N/P (DIN/DIP), N/Si (DIN/DSi), P/Si (DIP/DSi)]. A strong correlation was found between the riverine DIN fluxes and the estimated DIN inputs from the major N sources, particularly fertilizers and atmospheric deposition. The data provide a comprehensive assessment of nutrients in the Yangtze River basin and their ecological impacts and indicate a potentially significant influence of atmospheric deposition on DIN loadings and fluxes.     

TOWARD SUSTAINABLE MAIZE PRODUCTION FOR SMALLHOLDERS THROUGH OPTIMIZED STRATEGIES IN NORTH CHINA

● County-level sustainability assessment of maize production is presented. ● County-level improvement potential exhibits a large spatial heterogeneity. ● Promoting technical innovations can facilitate China’s agricultural transition. Agricultural production by smallholders is crucial for ensuring food provision in China. However, smallholders face a series of challenges on their farms including high-to-excess resource inputs, low use efficiency, as well as negative environmental impacts, which may be unfavorable for sustainable agriculture production. This study developed a county-level sustainability assessment of maize production in Hebei, China, by applying multiple data sources in combination with emergy, carbon footprint, nitrogen footprint and cost-benefit analyses. Scenario analysis was applied to explore the localized implementation strategies to achieve the sustainable farming system. The results show that the average emergy sustainability index (ESI) of maize at 2.31 is relatively low. The average greenhouse gas (GHG) emissions and reactive nitrogen (Nr) losses are 0.15 g·kcal⁻¹ CO₂-eq and 3.75 mg·kcal⁻¹ N, respectively. The average cost and net income are 12,700 and 4340 CNY·ha⁻¹, respectively. These results indicate a great potential to improve the environmental-economic sustainability of the maize production system of smallholders. In addition, the environmental and economic indicators calculated from the maize production show a substantial spatial heterogeneity among counties, indicating a requirement for different optimization strategies to improve the environment-economy sustainability at a finer scale. Based on the multiple scenario analysis, optimal strategies targeting each county are proposed. By adopting the optimal strategies, the average ESI and net income could increase by 32% and 83%, respectively, and the average GHG emissions and Nr losses reduce by 33% and 35%, respectively. These findings provide an important reference for adopting different strategies to achieve environment-economy sustainability for smallholders production systems with diverse landscapes in North China and propose a transition pathway toward achieving agriculture sustainability for smallholders worldwide.     

NEW ZEALAND DAIRY FARM SYSTEMS AND KEY ENVIRONMENTAL EFFECTS

• NZ dairy farming systems are based on year-round grazing of perennial pasture (ryegrass/white clover). • Milk production per hectare has increased by about 29% with increased use of externally-sourced feeds over the last two decades. • Externally-sourced feeds with a low protein concentration can potentially reduce N₂O emissions and N leaching per unit of production. • Systems analysis is important for evaluating mitigations to minimize trade-offs between environmental impacts. This paper provides an overview of the range of dairy pasture grazing systems used in New Zealand (NZ), the changes with increased inputs over time and associated key environmental effects including nitrogen (N) leaching and greenhouse gas (GHG) emissions. NZ dairy farming systems are based on year-round grazing and seasonal milk production on perennial ryegrass/clover pasture where cows are rotationally grazed in paddocks. There was an increase in stocking rate on NZ dairy farms from 2.62 cows ha⁻¹ in 2000/2001 to 2.84 cows ha⁻¹ in 2015/2016. During the same period annual milk solids production increased from 315 to 378 kg·yr⁻¹ per cow. This performance has coincided with an increase in N fertilizer use (by ~ 30%) and a twofold increase in externally-sourced feeds. Externally-sourced feeds with a low protein concentration (e.g., maize silage) can increase the efficiency of N utilization and potentially reduce N losses per unit of production. Off-paddock facilities (such as standoff or feed pads) are often used to restrict grazing during very wet winter conditions. A systems analysis of contrasting dairy farms in Waikato (largest NZ dairying region) indicates that the increased input would result in an increase in per-cow milk production but little change in efficiency of milk production from a total land use perspective. This analysis also shows that the increased inputs caused an 11% decrease in N footprint (i.e., N emissions per unit of milk production) and a 2% increase in C footprint (i.e., greenhouse gas (GHG) emissions per unit of milk production).