The use of biodegradable film as an alternative to polyethylene film is still controversial. Thus, a split-plot field trial was performed with planting patterns [traditional planting (FNM), and ridge-furrow planting with polyethylene and biodegradable films mulching (RPM, RBM)] coupled with nitrogen application levels [0 kg ha-1 (N0), 180 kg ha-1 (N180)] to explore the substitution of RBM for RPM in maize production. Compared with FNM, RBM and RPM increased the soil moisture storage by 11.6% and 11.5%, respectively, and soil mineral N concentration by 23.0% and 16.0% (under N180), but they reduced evapotranspiration by 3.9-11.7% and 7.9-36.4%, NH3 volatilization by 38.3% and 35.3%, and N2O emissions by 69.4% and 82.3% (2019 season). Moreover, compared with FNM, RBM and RPM increased the leaf area index by 16.8% and 19.4%, and aboveground dry matter by 10.8% and 16.5%, respectively. However, both mulching and N fertilization reduced the soil organic matter after 3 years of production. Path analysis revealed the differences in the influencing pathways of yield and the utilization of water and nitrogen. Consequently, compared with FNM, RBM and RPM under N180 improved the maize yield by 6.2% and 8.4%, and water use efficiency by 17.3% and 44.4%, respectively, but regardless of fertilization, they increased N harvest index by 9.2% and 10.8% and N use efficiency (2019 season) by 6.5% and 4.0%. These results demonstrated that the biodegradable film mulching was a viable replacement for polyethylene film mulching in maize production on the Loess Plateau in terms of soil fertility, plant growth, yield, and utilization of water and nitrogen.

Ridge-furrow film mulching has been widely used as a water-saving and yield-increasing planting pattern in arid and semiarid regions. Planting density is also a vitally important factor influencing crop yield, and the optimal planting density will vary in different environments (such as ridge-furrow film mulching). How the combination of film mulching and planting density will affect the growth, physiology, yield, and water and radiation use efficiencies of winter oilseed rape is not clear yet. Therefore, a three-year field experiment was conducted from 2017 to 2020 to explore the responses of leaf chlorophyll (Chl) content, net photosynthetic rate (Pn), leaf area index (LAI), aboveground dry matter (ADM), root growth and distribution, yield, evapotranspiration (ET), water use efficiency (WUE), and radiation use efficiency (RUE) of winter oilseed rape to different film mulching patterns (F, ridge-furrow planting with plastic film mulching over the ridges; N, flat planting without mulching) and planting densities (LD, 100,000 plants ha-1; MD, 150,000 plants ha-1; HD, 200,000 plants ha-1). The results showed that the F treatments led to significantly greater leaf Chl contents, Pn, LAI, and ADM, and a stronger root system than treatments without film mulching throughout the whole winter rapeseed growing seasons. Winter oilseed rape in the MD treatments had better physiological (leaf Chl contents and Pn) and growth (LAI, ADM, taproot, and lateral root) conditions than in LD and HD at the late growth period after stem-elongation. Grain yield in FMD was the greatest, and it was significantly greater by 34.8-46.0%, 6.7-9.6%, 87.8-108.3%, 38.7-50.3%, and 50.2-61.8% compared to those of FLD, FHD, NLD, NMD, and NHD, respectively. Furthermore, the ET in FMD was equivalent to FLD and FHD, but was markedly lower by 12.2-18.4%, 14.5-20.3%, and 14.6-20.4% than in NLD, NMD, and NHD. Finally, the WUE and RUE in FMD were significantly improved by 88.5-94.0% and 29.0-41.8% compared to NHD (the local conventional planting pattern and planting density for winter rapeseed). In summary, FMD is a favorable cultivation management strategy to save water, increase yield and improve resource utilization efficiencies in winter oilseed rape in Northwest China.

The biodegradable film, as an ideal substitute for plastic film, has broad application prospects. However, it is uncertain in maize actual evapotranspiration (ETac) components, yield, and water use efficiency (WUE) of biodegradable and plastic films during the different rainfall seasons. Therefore, a 4-year field trial with three mulching patterns (FNM: flat planting with non-mulching, RPM: ridge-furrow with plastic film mulching, and RBM: ridge-furrow with biodegradable film mulching) and two N-fertilization levels (0 and 180 kg N ha–1) was conducted. The results showed that the machine-learning models could accurately estimate maize ETac and its partitioning, and the random forest and artificial neural networks models had the highest accuracy and the least input variables after optimization. Compared to FNM, RBM and RPM increased Et by 10.8 mm, 14.0 mm in the dry season, 9.1 mm, 11.2 mm in the normal season, and 4.0 mm, 7.5 mm in the wet season, respectively, but decreased Es by 75.8 mm, 82.7 mm in the dry season, 48.6 mm, 56.7 mm in the normal season, 67.1 mm, and 74.9 mm in the wet season, respectively. Therefore, RBM and RPM decreased ETac by 65.0 mm, 68.8 mm in the dry season, 39.5 mm, 45.6 mm in the normal season, and 53.1 mm, 67.5 mm in the wet season, respectively, compared to FNM. Nitrogen application had a similar effect on Es and Et but only increased ETac by 13.3 mm in the dry season, 2 mm in the normal season, and 4.3 mm in the wet season, respectively, compared to N0. Furthermore, RBM and RPM under different nitrogen-fertilizations increased maize yield by 4.0 %, 3.6 % in the dry season, 3.0 %, 3.3 % in the normal season, and 5.3 %, 5.9 % in the wet season, respectively, also increased maize WUE by 23.3 %, 24.1 % in the dry season, 12.9 %, 15.0 % in the normal season, and 21.1 %, 23.4 % in the wet season, respectively, compared to FNM. This study proved that RPM could be replaced by RBM under 180 kg N ha–1 in the different rainfall seasons in terms of reducing ETac, increasing maize yield, and improving WUE. The optimized machine learning models in this study also provided a low-cost method for computing regional maize ETac.

Film mulching has been extensively used to improve agricultural production in arid regions of China. However, without sufficient mulch film recovery, large amounts of residual film accumulated in the farmland, which would affect crop yield and water use efficiency (WUE). In order to comprehensively analyze the effects of residual film on crop yield and WUE, and clarify its influencing mechanism, present study adopted a meta-analysis to systematically evaluate the impacts of residual film on soil physicochemical properties, crop root growth, yield, and WUE. The results showed that residual film significantly increased soil bulk density and the soil moisture content in 0-20 cm soil layer, but decreased soil porosity, soil organic matter, soil total nitrogen content, and soil moisture content in >20 cm soil layer, especially when residual film amount was >400 kg ha-1. Residual film significantly reduced crop root dry weight, root length, root diameter, root volume and root surface area. Generally, crop yield and WUE decreased with the increase of residual film amount; and crop yield was reduced by about 14.00 % when the residual film amount increased by 1000 kg ha-1. In average, crop yield and WUE under film residual condition were significantly decreased by 13.46 % and 9.21 %, respectively. The negative effects of residual film on root growth, yield and WUE were greater for cash crops (cotton, tomato and potato) than for cereal crops (wheat, maize). The structural equation model indicated that residual film generated indirect negative effects on crop yield and WUE by directly affecting soil physicochemical properties and crop root growth, with the standard path coefficients of -0.302 and - 0.217, respectively. The results would provide a theoretical basis for reducing residual film pollution on farmland and promoting the green and sustainable development of agriculture.

High temperature is known to reduce crop yield, while increased nitrogen (N) application will increase crop grain and protein yields to a certain extent. However, there are few studies on the effects of different N application treatments on crop yield and protein under climate warming in different wheat-maize rotation cultivation sites. Therefore, by utilizing the APSIM model, we investigated crop yield, yield components, grain N contents, and biomass N content across 71 key sites of wheat-maize rotation cultivation systems in China. Four N treatments of 0, 90, 180 and 270 kg N ha-1 (N0, N90, N180 and N270) were applied before sowing in both wheat and maize seasons. The APSIM model was calibrated and validated using data of yield and grain N content. We predicted regional differences in crop yield and grain N content under a warming 2 degrees C scenario. There were regional differences in the effects of increased N application treatments and warming 2 degrees C on wheat and maize yields, yield components and grain N contents. Increased N application improved maize 1000-grain weight and wheat grain number, and consequently affected crop yield and grain N content but reduced N translocation from plants to grains (NHI), especially in areas with more precipitation in wheat season and higher temperature in maize season. Warming shortened the duration of the reproductive growth period in maize by 6.2-9.5 d but lengthened it in wheat by 9.1-16.5 d. Furthermore, warming reduced maize yield mainly by decreasing maize 1000-grain weight and improved wheat yield mainly by increasing 1000-grain weight. Warming improved wheat grain N content and NHI under different N application treatments, especially in Shandong, Guanzhong, and Henan regions (0.86-1.98 kg ha-1 and 0.01-0.27, respectively). However, warming reduced maize yield, grain N content and NHI by 4.1 %-10.9 %, 1.5 %-6.8 % and 0.7 %-6.1 %, respectively, under different N application treatments except in Guanzhong. Additionally, increasing N application rate could alleviate the negative effects of warming on maize yield and grain protein production. In 2050-2067 maintaining historical plantation area, the regional total maize protein supply population was projected to reduce by 962.17 and 388.95 million people under N application of N180 and N270 kg N ha-1, respectively, compared with 2000-2017. The findings would provide scientific basis for N management strategies in wheat-maize rotation planting areas of China under climate warming.

Ridge-furrow film mulching (RFFM) and nitrogen (N) fertilization have been widely used in semi-arid regions, it is particularly important to clarify the mechanism of crop physiological indicators in response to RFFM. A twoyear (2018 and 2019) field experiment was conducted on summer maize under RFFM (including biodegradable film mulching (B) and plastic film mulching (P)) at N fertilizer application rate of 0 (N0), 90 (N1), 180 (N2) and 270 (N3) kg N ha-1. The aims of this research were to 1) explore the effects of different film mulching and N application rates under RFFM on photosynthesis, water utilization, and yield; 2) identify key factors and their contribution to yield. The results showed that RFFM and nitrogen application significantly improved net photosynthesis rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), intrinsic water use efficiency (WUEi) (grain-filling stage), the maximum quantum yield of PSII photochemistry (Fv/Fm), energy transformation potential activities of PSII (Fv/Fo), the effective quantum yield of PSII photochemistry (& phi;PSII), photochemical quenching of variable chlorophyll fluorescence (qP), non-photochemical chlorophyll fluorescence quenching (NPQ), chlorophyll ab (Chl ab), evapotranspiration (ET) and yield, but decreased chlorophyll a/b (Chl a/b) and soil water storage (SWS). The maximum Pn, Tr, Gs, WUEi, Fv/Fm. Fv/Fo, & phi;PSII, qP, and Chl ab (anthesis stage) all appeared in N2. At the same N application rate, the positive effects on photosynthetic and chlorophyll fluorescence (ChlF) of the plastic film were better than biodegradable film, especially in water use efficiency (WUE). Nitrogen deficiency had significantly negative effects on various parameters (Photosynthetic parameters, ChlF, Chl ab, grain yield), while nitrogen application (N > N1) had strong positive effects. Photosynthetic parameters, Fv/Fm, Fv/Fo, NPQ, Chl ab, ET, and WUE had strong positive effects on yield. The grain yield of the plastic film were slightly better (5.03% on average) than biodegradable film, but from the perspective of sustainable development, we recommend that biodegradable film and N2 should be used in the semi-arid regions of China.

针对晚播对夏玉米生长发育造成的不利影响,采用垄覆膜沟不覆盖(LN)、垄覆膜沟覆秸秆(LJ)和垄沟全覆膜(LM)3种垄沟种植方式,以常规播期平作不覆盖(CK1)和晚播平作不覆盖(CK2)为对照,分析了不同垄沟种植方式对晚播夏玉米农田土壤水分、土壤温度及玉米生长和产量的影响,对比不同垄沟覆盖种植方式对晚播玉米生长的补偿效应.结果表明:垄沟种植显著提升了夏玉米0～25 cm土层土壤温度,促进了晚播夏玉米生长;生育期内多雨导致各处理0～200 cm土层土壤含水率一直在18％(75％田间持水率)或更高水平,覆膜对土壤水分的影响不明显;垄沟种植夏玉米整体生长状态在8月中下旬(抽雄～灌浆阶段)与CK1处理达到相同水平;地上部干物质量在成熟期达到或超过CK1处理水平;低温多雨导致晚播夏玉米生育期延长了8～9 d;垄沟种植处理倒伏率较低,最高值仅为3％,平作处理倒伏严重,CK1和CK2处理倒伏率分别达73.1％和20.1％;CK2处理全生育期各项生长及产量指标均较低,LJ处理前期生长状态差,后期贪长,最终相对CK1处理减产7.9％;LN处理产量9783.8 kg?hm-2,与CK1处理持平,LM处理达到最高产量11101.7 kg?hm-2,相对CK1处理增产12.2％.综合考虑土壤水热、夏玉米生长、产量等各方面因素,多雨条件下垄沟全覆膜方式对晚播玉米生长达到了最好的补偿效果.

Soil preparation and mulching practices in combination with slow-release urea application are important measures for agricultural yield enhancement. However, slow-release urea may cause a yield reduction due to insufficient fertility in early crop growth. We considered whether the ridge-furrow plastic-mulching (RFP) system using different mulch colors could offset this disadvantage. An experiment was conducted using a randomized split-plot design with three soil preparation and mulching practices as the main-plot treatments in combination with three different urea applications as sub-plot treatments. The three soil preparation and mulching practices were flat cropping without mulch (F), the RFP system with white plastic mulch over the ridge (W), and the RFP system with black plastic mulch over the ridge (B); the three urea applications were no urea (N0), slow-release urea (NS), and ordinary urea (NU). The results showed that compared to F, the RFP system (especially B) could increase the use of precipitation and reduce soil water depletion, which ultimately increased the water productivity (WP) of winter wheat. In addition, the nitrogen use efficiency of NS was further improved under the RFP system, while there was essentially no difference between the two different urea types under F. In summary, B could take full advantage of NS to coordinate the relationship between effective spikes per unit area, grains per spike, and 1000-grain weight, maximizing the WP, nitrogen use efficiency, and grain yield. Between 2016 and 2019, the WP and grain yield of B-NS increased by 79.2–107.0% and 75.7–87.0%, respectively, compared to the lowest value (F-N0). The nitrogen agronomic efficiency (NAE), nitrogen physiological efficiency (NPE), nitrogen recovery efficiency (NRE), and nitrogen partial factor productivity (NPFP) of B-NS increased by 116.1–123.3%, 28.5–34.8%, 66.1–71.9%, and 44.1–53.2%, respectively, compared with the lowest value (F-NU).

为揭示缓释肥配施对夏玉米灌浆过程的影响规律,在相同施氮量(180 kg/hm2)下设置缓释肥(C)与尿素(N)配施比为1:0(C1N0)、3:1(C3N1)、1:1(C1N1)、1:3(C1N3)、0:1(C0N1),以不施氮肥(CK)为对照处理,共6个处理,研究缓释肥配施对夏玉米灌浆过程、光合性能、干物质积累及产量的影响.结果表明缓释肥配施可延长叶片功能期,保证夏玉米后期仍有较高的净光合速率及叶绿素含量,干物质积累及灌浆能力.缓释肥配施可促进籽粒灌浆的早启动,缩短达到最大灌浆速率时间,提高达到最大灌浆速率时的百粒重,延长灌浆活跃期,提高快增期、缓增期的持续时间及灌浆速率,进而提高百粒重.缓释肥配施条件下夏玉米产量提高的决定性产量构成因素是百粒重及行粒数,产量随缓释肥配施比例的提高呈先增加再降低趋势,配施比为3:1(C:N)时产量最高,较C1N0、C0N1处理分别提高16.08％、26.56％.综合分析,配施比3:1(C:N)在夏玉米种植中应用效果最优.

Plastic film mulching has been extensively used to improve yield and water use efficiency (WUE) of main crops in arid and semi-arid regions of northwest China. However, the plastic film residue has given rise to many problems, such as environmental pollution, land deterioration and yield reduction. Biodegradable film might be a good substitute for plastic film in agriculture production. Whether biodegradable film is suitable for peanut, one of the most important oil crops in the world? Which biodegradable film mulching pattern is beneficial to save water and increase production of peanut? A two-year field experiment was conducted to identify an appropriate biodegradable film mulching pattern for peanut at a typical rain-fed semi-arid site on the Loess Plateau. The peanut variety ‘Luhua 12’ was sown in four planting patterns: 1) flat planting without biodegradable film mulching (FNM), 2) flat planting with biodegradable film full mulching (FBM), 3) ridge-furrow planting with biodegradable film full mulching (RBM), 4) alternating wide-low and narrow-high ridges with biodegradable film full mulching (ARBM). The results indicated that biodegradable film mulching significantly improved soil hydrothermal environment, increased leaf area index and shoot biomass, promoted leaf chlorophyll content and photosynthetic rate, and finally enhanced production and WUE of peanut in comparison to FNM. Among the three biodegradable film mulching patterns, the average yield and WUE of peanut in ARFB were 17.2% and 24.2% significantly greater than FBM, and were 8.7% and 13.6% significantly greater than RBM, across the two seasons. In addition, ARFB consumed 4.8%-6.9% and 3.9%-4.4% less water, and increased 2218-4948 yuan ka−1 and 1591-2333 yuan ka−1 more income than FBM and RBM, respectively. Present study clearly demonstrated that ARFB is a prospective agricultural management to save water, increase production and WUE of peanut, and simultaneously to reduce plastic pollution in rain-fed semi-arid regions of northwest China.

Ridge-furrow with plastic film mulching and nitrogen fertilization has been shown to improve soil conditions and plant growth, but it is still unclear how the above-mentioned agronomic practices regulate carbon assimilating (source) and carbon reservoir (sink) to increase winter wheat yield and water use. A field trial was conducted with planting patterns (flat planting with non-mulching (FP) and ridge-furrow with plastic film mulch (RP)) as main plots and N rates (0, 90, 180, and 270 kg N ha(-1), marked as N0, N1, N2, and N3, respectively) as sub-plots. The results showed that RP significantly increased soil water storage (SWS), soil temperature (except that at the milk and dough stages of the 2019-2020 season), net content of soil mineral N, and consumption of soil mineral N by 3.8%-13.5%, 1.4-5 celcius, 7.2%-197.9%, and 15.1%-595.7%, respectively, but significantly decreased evapotranspiration during the growth stages (ETi), total ET (ETTotal) of 2019-2020, and WUE by 9.90%, 7.28%, and 11.52%, respectively, compared with FP. Nitrogen application significantly decreased SWS and soil temperature by 9.3%-22.9% and 5.1%-21.1%, but increased net content of soil mineral N, consumption of soil mineral N, ETi, ETTotal, and WUE by 45.9%-512.4%, 15.0%-22.0%, 6.0%-50.3%, 8.98%-25.32%, and 38.50-145.75%, respectively, compared with N0. Soil water storage at the anthesis, milk, and dough stages and soil temperature at the milk stage mainly increased the source and establishment of the initial reservoir, while the soil mineral N mainly optimized the source-sink balance in the middle and late period. However, leaf area and dry matter at anthesis, chlorophyll content at 18 days post-anthesis, and grain number, especially spike number, played decisive roles in increasing yield, while leaf area and dry matter at the milk stage, grain volume at 30 days post-anthesis, and especially the post-anthesis contribution rate for dry matter accumulation in grains, were the main limiting factors. Therefore, ridge-furrow with plastic film mulching combined with 180 kg N ha(-1) could balance the source-sink, but it is necessary to study the ratio of ridge-furrow and sowing rate to achieve a high yield and WUE.

为了精准指导农田灌溉,合理优化渠系输配水,提高水资源的利用率、灌区的管理水平和总效益,对灌区用水计划的编制方法展开了理论研究.将用水计划的编制过程概括为实时灌溉预报和渠系配水两部分,分别进行归纳整理和分析.在对国内灌区用水计划的编制方式进行了解的基础上,着重介绍了利用土壤水分平衡方程进行实时灌溉预报的方法,总结各参数预测值和计算修正值的获取方法,分析对比各方法的适用范围,提炼普遍灌区实时灌溉预报中适用的方法.为了优化田间渠系配水次序和配水量,以保证作物得到及时有效灌溉,归纳总结了国内灌区常用的渠系配水模型,论述了常见的目标函数及相关约束的选取原则,并指出其局限性和可能的发展趋势.研究结果可为各灌区进行实时灌溉预报和建立优化配水模型提供借鉴与参考.

Drip irrigation technology combined with film mulching has expanded rapidly in arid and semi-arid areas. Without sufficient mulch film recovery, large amounts of plastic film remain in the field, changing the original water infiltration movement, which is not well understood. In this study, structural equation modeling was used to study the impact of residual plastic film (RPF) and emitter flow rate (FR) on the migration time of wetting front (MTWF), soil infiltration aspect ratio (AR) and accumulative infiltration (AI) under different initial moisture content (IMC) and dry bulk density (DBD). The results showed that RPF prevented the downward movement of water, which led to increased MTWF, AI and AR. However, RPF had no direct effect on the AI and infiltration AR, and the effects that it did have on these factors were indirectly influenced by the MTWF. When the RPF content was greater than 480 kg/hm2 (with a mulching history of 26 years), the infiltration AR was greater than 1.0. Additionally, there was a parabolic relationship between the emitter FR and the MTWF. When the FR was 0.7 L/h, the MTWF reached its minimum value. Overall, this study explored the process of water movement under drip irrigation infiltration of RPF farmland and provided a theoretical basis for the design of drip irrigation systems for RPF farmland.

针对陕西关中小麦肥料利用效率不高的问题,在陕西省杨凌示范区开展了缓释氮肥与尿素的配施试验,设置了不施氮肥(N0)、100％尿素(N1)和4个不同缓释氮肥配施处理(N2(100％)、N3(25％)、N4(50％)、N5(75％)),以不施肥CK为对照;分析缓释氮肥与尿素配施对冬小麦干物质累积及氮素吸收量、土壤硝态氮含量和分布、产量及水氮利用效率的影响.结果表明:与N1、N2处理相比,缓释氮肥和尿素配施不仅能显著增加冬小麦干物质累积量(4.69％ ～11.40％)、氮素吸收量(5.92％ ～24.08％)及产量(6.00％ ～22.41％),还能增加土壤表层(0～40 cm)的硝态氮累积量(2.09％ ～45.51％),减少其淋失到深层土壤,提升氮肥利用效率.N5处理下冬小麦的氮肥偏生产力(42.46 kg/kg)、氮肥农学利用率(15.46 kg/kg)和氮肥表观利用率(47.79％)均最大,成熟期N5处理的干物质累积量较N1和N2处理分别提高了11.40％和9.20％,地上部氮素累积量分别提高了24.08％和11.49％,产量分别提高了22.41％和11.00％.收获时N5处理0～40 cm土层中硝态氮的累积量最大,比其它施肥处理提高了1.30％ ～19.52％.综上所述,75％缓释氮肥+25％尿素处理(N5)是本研究中冬小麦高产高效的最优施肥方案.

The biodegradable film is an alternative to polyethylene film due to polyethylene residue pollution, but whether the biodegradable film can replace polyethylene film in terms of root growth, utilization of water and nitrogen, yield, and reducing N application remains unclear. Therefore, two-year field trials, involved two films (biode-gradable film and polyethylene film) as the main plots and four nitrogen levels (0 (N0), 90 (N1), 180 (N2), and 270 (N3) kg N ha(-1)) as the subplots, were conducted. The results showed that compared with N0, N application significantly increased root length density (0-20 cm layer), root surface area density (0-10 cm layer), root weight (0-10 cm layer), and root/shoot ratio by 41.6%, 38.8%, 89.8%, and 33.0% on average for biodegradable film and by 40.3%, 33.9%, 61.5%, and 23.3% for polyethylene film, respectively. However, N application only signifi-cantly increased the root-bleeding sap per unit area (RBS) by 20.1% for biodegradable film compared to N0. Furthermore, N-fertilization significantly increased shoot dry matter, evapotranspiration (ET), water use effi-ciency (WUE), nitrogen use efficiency (NUE) (except for N3), and yield by an average of 31.8%, 9.5%, 33.2%, 7.9%, and 46.1% (biodegradable film), 24.8%, 11.6%, 34.4%, 7.5%, and 50.3% (polyethylene film), respectively, compared with N0. Compared with polyethylene film, root length densities, root surface area densities, root weights in the 0-10 cm layer, and WUE were significantly lower, but RBS (except for N0), ET, and NUE were significantly higher under biodegradable film. Path analysis showed that both improving root length density and root weight were conducive to increasing dry matter accumulation, WUE, and yield for two films. The optimum N rate was also found at 173.2 kg ha(-1) for biodegradable film and 182.1 kg ha(-1) for polyethylene film, which could increase NUE. Therefore, ridge-furrow with biodegradable film mulching combined with 173.2 kg N ha(-1) could achieve the goal of replacing polyethylene film in terms of high yield, efficient utilization of nitrogen, and reducing N application.

With the extensive use of plastic film, a large number of residual film accumulated in the farmland, bringing a huge negative impact on agricultural production. Studying the effect of residual film on roots is helpful to understand the damage mechanism of residual film on crop growth. Thus, a two-year field experiment was conducted with 0 (M0), 90 (M90), 180 (M180), 360 (M360), and 720 (M720) kg ha-1 residual film, and sine and logistic functions were used to simulate root growth and vertical distribution of maize. Results showed that root length decreased with residual film increasing and was more sensitive to residual film at tasseling, filling and maturity stages than at seedling and jointing stages. The results of the sine function fitting the total root length showed that the potential maximum root length was decreased and the rooting time was delayed, and the root growth time was shortened with the amount of residual film increasing. M90 had no significant effect on root length but residual film equal to or greater than 180 kg ha-1 had significant negative effects on root length. M180, M360 and M720 significantly reduced the actual total root length by 13.7%, 23.8% and 33.3%, and reduced the potential root length by 9.4%, 17.1% and 21.8%. M360 and M720 significantly shortened the growth time by 3.8% and 6.6%. The logistic function fit the vertical root distribution well. Residual film decreased the root length in deep soil and gathered roots in the soil layer near the depth of d50 at which 50% of the root length was accumulated. Residual film decreased the soil depth where 50% and 95% root length were accumulated and increased the proportion of root length in 0-30 cm soil layer. This adverse effect increased with residual film amount increasing. The dry matter of stems, leaves and ears decreased with residual film increasing. M90 reduced the above-ground dry matter insignificantly and the other treatments with residual film had significant effects. At the maturity stage, the above-ground dry matter in M90, M180, M360 and M720 was reduced by 2.4%, 14.2%, 22.2% and 29.4%, compared with M0. Residual film decreased evapotranspiration (ET), grain yield and water use efficiency (WUE) significantly except M90. ET, yield and WUE were reduced by 1.7%, 3.0% and 1.1% in M90, and 2.5%, 17.1% and 16.1% in M180, and 6.2%, 27.1% and 23.4% in M360, and 8.5%, 34.7% and 30.8% in M720, respectively. In summary, the residual film beyond 180 kg ha-1 had a significant negative effect on summer maize. This information will be useful to better understand and respond to residual film pollution and ensure safe agricultural production.

Film mulching and nitrogen fertilization are two effective practices to promote maize production in northwest China, but their impacts on environment in terms of greenhouse gas emission remain unclear. Two-year field trials were conducted to 1) explore the effect of the film mulching pattern and N fertilization rate on maize production, gaseous N emission, and utilization of N and water; 2) find an optimal mulching pattern and N fertilization rate to achieve green development. Trial I included flat planting with non-mulching (NM), ridge furrow with plastic film mulch (PM), ridge-furrow with biodegradable film mulch (BM), and flat planting with full plastic film mulching (FM). Trial II involved BM with N-fertilization rates (0, 90, 180, and 270 kg N ha(-1)), denoted as BMN0, BMN1, BMN2, and BMN3, respectively. The results showed that film mulching significantly decreased the daily flux and cumulative flux of gaseous N by an average of 32.02%, 35.17% (NH3), 78.70%, 75.83% (N2O), respectively, as compared with NM. Film mulching also significantly increased the amount of soil residual mineral N after harvest, plant N uptake, and soil water storage but decreased evapotranspiration by an average of 8.31%, 9.42%, 17.45%, and 25.34%, respectively, as compared with NM. In addition, grain yield, water use efficiency (WUE), N uptake efficiency (UPE) (except for BM), N harvest index (NHI), N use efficiency (NUE), and partial productivity of N (PNP) were significantly higher in the mulching treatments, and yield-scaled NH3 emission (YSN) was significantly lower in PM and BM, as compared with NM. Compared with FM, soil residual mineral N after harvest, plant N uptake, grain yield, WUE, NUE, and PNP were significantly lower but NHI was significantly higher in PM and BM. The daily flux and cumulative flux of N2O emission and the amount of soil residual NO3--N after harvest were significantly lower but plant N uptake was significantly higher in PM than in BM. Collectively, BM was the best mulching treatment in this study. With increase of N-fertilization rate, the daily flux and cumulative flux of NH3 volatilization, the peak period, and the cumulative flux of N2O emission, the grain yield, WUE, NUE (except for N3), and YSN were significantly increased but NHI, PNP, and UPE were significantly decreased. The optimum N-fertilization rate under BM was found at 173 kg ha(-1), which could achieve the goal of high yield, efficient utilization of water and nitrogen, and environmental friendliness.

针对陕西关中地区夏玉米农田存在施氮量过多、氮肥利用效率过低的问题,设置常规施氮N1(300 kg,/hm2)、100％缓释氮肥N2(300 kg/hm2)、65％缓释氮肥N3(195 kg/hm2)、30％缓释氮肥N4 (90 kg/hm2)、不施氮N0共5个施氮水平,磷肥和钾肥均按统一标准施用,以不施肥CK为对照,于2018年和2019年在陕西杨凌地区进行了田间试验,研究不同缓释氮肥减施量对夏玉米地上部干物质累积、氮素累积吸收量、土壤硝态氮分布及累积、产量和氮肥利用效率等指标的影响.结果 表明:施加氮肥可以显著提高夏玉米地上部干物质累积量、氮素吸收量和产量,与当地常规施氮N1处理相比,N2处理和N3处理的地上部干物质累积量及氮素累积吸收量、氮素吸收效率、氮肥偏生产力、产量等指标均有显著增加;两年试验,N2处理与N3处理的地上部干物质累积量、氮素累积吸收量、产量无显著差异,但N3处理的氮肥偏生产力较N2两年分别提高54.61％和56.25％,氮肥农学利用率分别提高35.24％和61.48％,营养器官氮素转运率分别提高17.34％和18.10％;缓释氮肥减施可以显著降低0～ 200 cm土层的硝态氮残留量,并且可以提高0～40 cm土层硝态氮占比,0～ 40 cm土层硝态氮占比最大的为N3处理,较其他施氮处理提高6.82％ ～118.60％.在既能满足较高产量又能满足较高氮肥利用效率、较低氮素流失的情况下,缓释氮肥纯氮施用量195 kg/hm2是该地区较优的施肥方式.

Ridge-furrow film mulching (RF) is an effective planting pattern to harvest rainwater, reduce evaporation, increase root-zone soil moisture and improve crop yield in arid regions of northwest China. Compared to flat planting without film mulching (FP), RF significantly enhances the yield and water and nitrogen (N) use efficiencies of winter wheat under the same irrigation and N inputs. However, whether RF can boost or maintain yield, water use efficiency (WUE) and N use efficiency (NUE) of winter wheat with less irrigation and N supply remains unclear. Moreover, the irrigation-saving and N reduction potential for RF under different climatic (wet, normal and drought) years is unknown. From 2013-2016, field experiments with treatments of different planting patterns (RF and FP), irrigation (0, 90 and 180 mm; represented as I0, I1 and I2, respectively) and N (0, 140 and 210 kg ha-1; represented as N0, N1 and N2, respectively) application amounts were conducted to analyze the growth and physiological characteristics, yield, WUE and NUE of winter wheat. The results showed that the leaf area index, aboveground dry matter, leaf chlorophyll content and net photosynthetic rate were greatest for RFI2N2 (RF with 180 mm irrigation and 210 kg N ha-1) during the whole winter-wheat growing seasons. Eventually, RFI2N2 obtained 9.3-74.1 %, 19.5-81.1 % and 23.8-92.2 % significantly greater yield than other treatments in wet and cool, normal rainfall and temperature, and drought and heat years, respectively. Relative to FPI2N2 (FP with 180 mm irrigation and 210 kg N ha-1, and FPI2N2 is local conventional agricultural management for winter wheat), the irrigation and N reduction potential for RF differed for the three levels of annual rainfall. Treatment RFI0N1 (RF with no irrigation and 140 kg N ha-1) in wet and cool, and normal rainfall and temperature years, and RFI1N1 (RF with 90 mm irrigation and 140 kg N ha-1) in drought and heat years, had almost equal winter wheat yield, and achieved significantly greater WUE and NUE than FPI2N2. In addition, in wet and cool, and normal rainfall and temperature years, RFI1N1 had 14.6-17.7 %, 5.0-10.0 % and 16.2-30.5 % significantly greater yield, WUE and NUE than RFI0N1. Therefore, RFI1N1 could be considered as a favorable management for sustainable intensification of winter wheat production in northwest China, especially in drought and heat years and in areas where water resources are relatively abundant.

近年来,区块链凭借其不可篡改性、唯一性、智能合约和去中心自组织等特点,得到了各行各业的广泛关注.随着国内学者对区块链研究的逐步深入,区块链技术在我国教育领域的应用也得到进一步扩展,越来越受到业内的关注.但是,由于当前区块链技术在教育领域的应用尚处于摸索阶段,所以具体的实践情况尚不甚明了.为此,采取文献分析法对区块链技术在我国教育领域的应用情况进行了梳理.从总体上看,区块链在我国的发展正逐步从理论研究转向实践探索,并不断走向具体化和精细化.根据参与方的属性不同,区块链可以分为公有链、私有链和联盟链;根据链与链之间的关系,又可分为主链和侧链;根据链中记录的内容,可以分为实物链和代币链.此外,还有许可链、交叉链等.区块链技术在我国教育领域的应用主要集中在教育资源管理领域、教育(教学)信息管理领域、教育基础平台建设领域等3个方面,在实践中所面临的问题包括:数据产权归属界限不明晰;匿名技术尚不成熟,隐私保护存在风险;链上存储可扩展性需求日益迫切,海量数据存储遭遇"瓶颈";技术安全性面临威胁;应用动力不足,开发有难度.为了进一步加快区块链技术在教育领域的落地,提出区块链技术的发展应重点关注推动重构未来教育新形态、助力打造智"链"校园、促进教育(教学)管理模式的改革等.