Optimizing crop yields while minimizing environmental impact through deep placement of nitrogen fertilizer

Nitrogen(N)serves as an essential nutrient for yield formation across diverse crop types.However,agricultural production encounters numerous challenges,notably high N fertilizer rates coupled with low N use efficiency and serious environmental pollution.Deep placement of nitrogen fertilizer(DPNF)is an agronomic measure that shows promise in addressing these issues.This review aims to offer a comprehensive understanding of DPNF,beginning with a succinct overview of its development and methodologies for implementation.Subsequently,the optimal fertilization depth and influencing factors for different crops are analyzed and discussed.Additionally,it investigates the regulation and mechanism underlying the DPNF on crop development,yield,N use efficiency and greenhouse gas emissions.Finally,the review delineates the limitations and challenges of this technology and provides suggestions for its improvement and application.This review provides valuable insight and reference for the promotion and adoption of DPNF in agricultural practice.

Effect of side deep placement of nitrogen on yield and nitrogen use efficiency of single season late japonica rice

Side deep placement of nitrogen plays an important role in improving rice yield and nitrogen use efficiency.Few studies have examined the effects of reducing the times of nitrogen(RTN)application and reducing the nitrogen rate(RNR)of application on rice yield and nitrogen use efficiency under side deep placement of nitrogen in paddy fields.Therefore,a field experiment of RNT and RNR treatments was conducted with nine fertilization modes during the 2018–2019 rice growing seasons in a rice–wheat cropping system of the lower reaches of the Yangtze River,China.Rice yield and nitrogen use efficiency were investigated under side deep placement of nitrogen.We found that under the same nitrogen application rate,the yield of RTN3 increased by 9.64 and 10.18%in rice varieties NJ9108 and NJ5718,respectively,compared with the farmers’fertilizer practices(FFP).The nitrogen accumulation of RTN3 was the highest at heading stage,at 11.30 t ha^(–1)across 2018 and 2019.Under the same nitrogen application rate,the N agronomic use efficiency(NAE),N physiological efficiency(NPE)and N recovery efficiency(NRE)of RTN3 were 8.1–21.28%,8.51–41.76%and 0.28–14.52%higher than those of the other fertilization modes,respectively.RNR led to decreases in SPAD value,leaf area index(LAI),dry matter accumulation,nitrogen accumulation,and nitrogen use efficiency.These results suggest that RTN3 increased rice yield and nitrogen use efficiency under the side deep placement of nitrogen,and RNR1 could achieve the goals of saving cost and increasing resource use efficiency.Two fertilization modes RTN3 and RNR1 both could achieve the dual goals of increasing grain yield and resource use efficiency and thus are worth further application and investigation.

Nitrogen Deep Placement Combined with Straw Mulch Cultivation Enhances Physiological Traits,Grain Yield and Nitrogen Use Efficiency in Mechanical Pot-Seedling Transplanting Rice

To assess the effects of straw return coupled with deep nitrogen(N)fertilization on grain yield and N use efficiency(NUE)in mechanical pot-seedling transplanting(MPST)rice,the seedlings of two rice cultivars,i.e.,Yuxiangyouzhan and Wufengyou 615 transplanted by MPST were applied with N fertilizer at 150 kg/hm2 and straw return at 6 t/hm2 in early seasons of 2019 and 2020.The experiment comprised of following treatments:CK(no fertilizer and no straw return),MDS(deep N fertilization and straw return),MBS(broadcasting fertilizer and straw return),MD(deep N fertilization without straw return),MB(broadcasting fertilizer without straw return).Results depicted that the MDS treatment significantly increased the rice yield by 41.69%-72.22%due to total above-ground biomass,leaf area index and photosynthesis increased by 54.70%-55.80%,38.52%-52.17%and 17.89%-28.40%,respectively,compared to the MB treatment.In addition,the MDS treatment enhanced the total N accumulation by 37.74%-43.69%,N recovery efficiency by 141.45%-164.65%,N agronomic efficiency by 121.76%-134.19%,nitrate reductase by 46.46%-60.86%and glutamine synthetase by 23.56%-31.02%,compared to the MB treatment.The average grain yield and NUE in both years for Yuxiangyouzhan were higher in the MDS treatment than in the MD treatment.Hence,deep N fertilization combined with straw return can be an innovative technique with improved grain yield and NUE in MPST in South China.

Assembly and co-occurrence patterns of rare and abundant bacterial sub-communities in rice rhizosphere soil under short-term nitrogen deep placement

Nitrogen(N)deep placement has been found to reduce N leaching and increase N use efficiency in paddy fields.However,relatively little is known how bacterial consortia,especially abundant and rare taxa,respond to N deep placement,which is critical for understanding the biodiversity and function of agricultural ecosystem.In this study,lllumina sequencing and ecological models were conducted to examine the diversity patterns and underlying assembly mechanisms of abundant and rare taxa in rice rhizosphere soil under different N fertilization regimes at four rice growth stages in paddy fields.The results showed that abundant and rare bacteria had distinct distribution patterns in rhizosphere samples.Abundant bacteria showed ubiquitous distribution;while rare taxa exhibited uneven distribution across all samples.Stochastic processes dominated community assembly of both abundant and rare bacteria,with dispersal limitation playing a more vital role in abundant bacteria,and undominated processes playing a more important role in rare bacteria.The N deep placement was associated with a greater influence of dispersal limitation than the broadcast N fertilizer(BN)and no N fertilizer(NN)treatments in abundant and rare taxa of rhizosphere soil;while greater contributions from homogenizing dispersal were observed for BN and NN in rare taxa.Network analysis indicated that abundant taxa with closer relationships were usually more likely to occupy the central position of the network than rare taxa.Nevertheless,most of the keystone species were rare taxa and might have played essential roles in maintaining the network stability.Overall,these findings highlighted that the ecological mechanisms and co-occurrence patterns of abundant and rare bacteria in rhizosphere soil under N deep placement.

Mitigating N2O and NO Emissions from Direct-Seeded Rice with Nitrification Inhibitor and Urea Deep Placement

Soil-emitted nitrous oxide(N2O) and nitric oxide(NO) in crop production are harmful nitrogen(N) emissions that may contribute both directly and indirectly to global warming. Application of nitrification inhibitors, such as dicyandiamide(DCD), and urea deep placement(UDP), are considered effective approaches to reduce these emissions. This study investigated the effects of DCD and UDP, compared to urea and potassium nitrate, on emissions, nitrogen use efficiency and grain yields under direct-seeded rice. High-frequency measurements of N2O and NO emissions were conducted using the automated closed chamber method throughout the crop-growing season and during the ratoon crop. Both UDP and DCD were effective in reducing N2O emissions by 95% and 73%, respectively. The highest emission factor(1.53% of applied N) was observed in urea, while the lowest was in UDP(0.08%). Emission peaks were mainly associated with fertilization events and appeared within one to two weeks of fertilization. Those emission peaks contributed to 65%–98% of the total seasonal emissions. Residual effects of fertilizer treatments on the N2O emissions from the ratoon crop were not significant;however, the urea treatment contributed 2%, whereas UDP contributed to 44% of the total annual emissions. On the other hand, cumulative NO emissions were not significant in either the rice or ratoon crops. UDP and DCD increased grain yields by 16%–19% and N recovery efficiency by 30%–40% over urea. The results suggested that the use of DCD and UDP could mitigate N2O emissions and increase grain yields and nitrogen use efficiency under direct-seeded rice condition.

Soil Nitrogen Distribution and Plant Nitrogen Utilization in Direct-Seeded Rice in Response to Deep Placement of Basal Fertilizer-Nitrogen

Deep placement of controlled-release fertilizer increases nitrogen (N) use efficiency in rice planting but is expensive. Few studies on direct-seeded rice have examined the effects of deep placement of conventional fertilizer. With prilled urea serving as N fertilizer, a two-year field experiment with two N rates (120 and 195 kg/hm2) and four basal N application treatments (B50, all fertilizer was broadcast with 50% as basal N;D50, D70 and D100 corresponded to 50%, 70% and 100% of N deeply placed as basal N, respectively) were conducted in direct-seeded rice in 2013 and 2014. Soil N distribution and plant N uptake were analyzed. The results showed that deep placement of basal N significantly increased total N concentrations in soil. Significantly greater soil N concentrations were observed in D100 compared with B50 at 0, 6 and 12 cm (lateral distance) from the fertilizer application point both at mid-tillering and heading stages. D100 presented the highest values of dry matter and N accumulation from seeding to mid-tillering stages, but it presented the lowest values from heading to maturity stages and the lowest grain yield for no sufficient N supply at the reproductive stage. The grain yield of D50 was the highest, however, no significant difference was observed in grain yield, N agronomic efficiency or N recovery efficiency between D70 and D50, or between D70 and B50, while D70 was more labor saving than D50 for only one topdressing was applied in D70 compared with twice in other treatments. The above results indicated that 70% of fertilizer-N deeply placed as a basal fertilizer and 30% of fertilizer-N topdressed as a panicle fertilizer constituted an ideal approach for direct-seeded rice. This recommendation was further verified through on-farm demonstration experiments in 2015, in which D70 produced in similar grain yields as B50 did.

Effects of Fertilizer Placement and Nitrogen Forms on Soil Nitrogen Diffusion and Migration of Red-Yellow Soil in China

A better understanding of nitrogen (N) diffusion and transformation in soils could reveal the capacity of the biological inorganic N and improve the efficiency of N fertilizers. A field micro-plot experiment was carried out to study the effects of fertilization methods (mixed uniformly with 12 cm top soil, placed in holes at a 12-cm depth, or placed in furrows at a 12-cm depth) and forms of N fertilizers (urea and ammonium phosphate) on the dynamics of soil N’s vertical diffusion and horizontal migration in red-yellow soil. The soil inorganic N ( NH4+-N and NH3--N) content following point deep placement was greater than that from mixed or furrow applications. Under point placement, the migration of soil inorganic N in urea and ammonium phosphate treatments occurred in the 6 - 15 cm layer at a horizontal distance of 0 - 9 cm. However, the nutrient preservation capability of the soil receiving ammonium phosphate was greater than that receiving urea under point deep placement. Thus, point deep placement had a tendency to increase the inorganic N in the soil and reduce inorganic N loss, which probably occurred due to the reduced soil volume with which the N fertilizer was mixed. According to crop growth and fertilizer requirements, the optimized fertilizer placement and N species resulted in a continuously high nutrient supply to crops for 90 d. However, the effects of point deep placement on increasing the N-use efficiency and reducing N loss have to be evaluated under natural field conditions.

经导管取栓联合置管溶栓治疗下肢深静脉血栓的临床疗效

目的 探讨经导管取栓联合置管溶栓治疗下肢深静脉血栓形成(LDVT)的临床疗效。方法 收集2019年3月至2023年2月安庆市第一人民医院收治的76例LDVT患者的临床资料,按照治疗方法的不同将其分为药物组(n=38,采用保守药物治疗)与介入组(n=38,采用经导管取栓联合置管溶栓治疗)。比较两组患者临床指标,治疗前、治疗后7d健患侧大腿围差值、小腿围差值及凝血功能指标,评估临床疗效与血栓清除效果,统计两组患者治疗后并发症发生情况。结果 介入组患者治疗时间、症状改善时间、住院时间均短于药物组患者,差异均有统计意义(P﹤0.05)。治疗后,两组患者健患侧大腿围差值、小腿围差值均小于本组治疗前,且介入组患者均小于药物组患者,差异均有统计学意义(P﹤0.05)。治疗后,两组患者凝血酶原时间(PT)、活化部分凝血活酶时间(APTT)均较本组治疗前延长,纤维蛋白原(FIB)、D-二聚体(D-D)水平均较本组治疗前下降,且介入组患者PT、APTT均长于药物组患者,FIB、D-D水平均低于药物组患者,差异均有统计学意义(P﹤0.05)。介入组患者血栓清除效果、临床疗效均优于药物组患者,差异均有统计学意义(P﹤0.05)。两组患者治疗后并发症发生率比较,差异无统计学意义(P﹥0.05)。结论 经导管取栓联合置管溶栓治疗LDVT可获得更为理想的临床疗效与血清清除效果,并可缩短溶栓时间,提高治疗安全性。

侧深施肥对水稻产量及养分吸收的影响

肥料深施是提高粮食产量和氮素利用率的关键要素。鉴于当前临海地区化肥种类繁多、施肥方式多样,通过田间试验,研究不同肥料与不同施肥方式相结合对水稻产量及土壤肥力的影响。结果表明,惠多利复合肥深施(HS)和惠多利复合肥减量深施(HSJ)对水稻增产效果明显;茂施缓释肥一次性深施(MSY)显著增加了稻谷含氮量。因此,水稻产量及养分吸收受肥料类型和施肥方式的影响较大。茂施缓释肥减量深施(MSJ)提升pH值的同时也显著提升了土壤有机质、全氮、有效磷、速效钾含量。综上所述,HS和HSJ施肥处理的株高和穗长增效显著且显著提升水稻产量,建议在后续生产中进行推广。

基于深度蒙特卡洛树搜索的拱坝仓面排序研究

合理的仓面排序方案对于加快工程进度和优化资源配置有着重要影响。然而,现有仓面排序方法将这一序贯决策问题简化,多数采用多属性决策方法,存在仅对大坝实时施工状态进行分析以及未考虑未来仓面浇筑方案对当前排序策略影响的问题;部分采用多目标优化方法进行仓面排序多目标优化问题分析,但主要是采用静态权重,存在忽略了仓面排序策略随环境动态变化的不足。针对以上问题,本文提出基于深度蒙特卡洛树搜索的拱坝仓面排序方法。首先,分析仓面排序问题的约束条件和目标函数,建立仓面排序强化学习模型;其次,针对仓面排序强化学习模型具有复杂且庞大的离散状态空间,为提高搜索效率,提出融合深度学习的蒙特卡洛树搜索方法,分别利用深度神经网络进行先验动作概率分布预测和策略函数评估;最后,以乌东德拱坝工程为例进行研究,结果表明本文方法可以有效地分析拱坝仓面排序问题,且相比于粒子群方法、证据理论方法,本文方法分析的施工工期可分别提前6天、14天,平均机械利用率分别提高1.19%、1.35%。本研究为拱坝仓面排序分析与优化提供了新思路。

基于视觉强化学习的数字芯片全局布局方法

在数字芯片后端设计中,全局布局需要同时兼顾线长与合法化,是一个组合优化问题。传统的退火算法或者遗传算法耗时且容易陷入局部最优,目前强化学习的解决方案也很少利用布局的整体视觉信息。为此,提出一种融合视觉信息的强化学习方法实现端到端的全局布局。在全局布局中,将电路网表信息映射为多个图像级特征,采用卷积神经网络(convolutional neural network,CNN)和图卷积网络(graph convolutional network,GCN)将图像特征和网表信息相融合,设计了一整套策略网络和价值网络,实现对全局布局的全面分析和优化。在ISPD2005基准电路上进行实验,结果证明设计的网络收敛速度加快7倍左右,布局线长减少10%~32%,重叠率为0%,可为数字芯片全局布局任务提供高效合理的方案。

考虑储能调控优化的配电网分布式电源选址定容

稳定配电网潮流分布、明确分布式电源的接入位置和容量是含分布式电源配电网优化运行的重要问题。提出一种基于深度强化学习算法的储能调控优化模型,实现分布式电源配置与用电负荷需求关系的匹配,从而稳定高渗透率下配电网的潮流分布。以线路损耗与电压波动性为损失函数,提出基于多目标遗传算法的分布式电源选址定容决策模型。在IEEE 14节点系统进行测试,结果表明该算法能够有效选择分布式电源的最佳接入位置和容量,在保证电压幅值不产生过大波动的同时,进一步降低了整体网络的线路损耗。

狭小空间大管径超长溜管浇筑超大底板施工技术分析

为提升狭小空间下深基坑超大底板的施工质量,文中依托某超高层建筑项目施工实践,对该项目超长溜管单侧浇筑方案及施工技术进行分析,并评估大体积混凝土温控效果。结果表明,溜管浇筑工艺的最快浇筑速度达到了650 m^(3)/h,是常规汽车泵浇筑速度的8倍,节省造价58万元,具有较好的社会效益和经济效益;所有条件下的温度监测数据均满足设计要求,表明蓄水保温法对混凝土的温度控制具有良好的应用效果。

SYJ-2型液肥变量施肥机设计与试验

变量施肥技术是精准农业的重要组成部分,依据农业生产要求设计了与轮式拖拉机配套的SYJ-2型三点悬挂式液肥变量施肥机。以单片机作为核心处理器,以电磁比例调节阀为执行部件,设计编写了液肥变量控制系统以及与硬件配套的上位机软件,用于采集数据与发送命令;关键部件内腔式旋转扎穴机构采用5个全等椭圆齿轮传动,液肥在内腔流动,在减少外部连接软管的同时,防止了管路缠绕;液肥分配器的功能是适时开启和关闭,实现液肥的不连续射出,进而完成穴施作业;同时对内腔式旋转扎穴机构和液肥分配器进行了结构设计。田间试验结果表明,施肥深度为地表12-15 cm,施肥精度为99.1%,满足液态变量施肥作业要求。

不同施肥方式对春玉米产量、效益及氮素吸收和利用的影响

通过田间试验研究了农民习惯施肥、氮肥减量及减量后移、氮肥一次性深施对春玉米产量、效益、花后干物质和氮素积累与转移情况及氮的吸收和利用的影响。结果表明,与习惯施肥处理(氮用量N 280 kg/hm2,口肥和拔节期追肥比例为1∶4,N280/2,)相比,氮肥减量后移处理(氮用量N 240 kg/hm2,口肥、拔节期和大喇叭口期追肥比例为1∶2∶2,N240/3)增产3.91%,增收592元/hm2;氮肥一次性深施处理(氮用量N 240 kg/hm2,播种时一次深施在15 cm处,N240/1)增产11.48%,增收2032元/hm2;氮肥减量后移处理(N240/3)和氮肥一次性深施处理(N240/1)的经济系数、后期干物质和氮的转移量、转移效率及对子粒的贡献率显著提高,氮肥利用率(NUE)、氮肥农学利用率(ANUE)、氮素吸收效率(NUPE)和氮肥偏生产力(PFP)、氮收获指数(NH I)也显著提高。氮肥减量后移处理(N240/3)花后干物质和氮的积累量及占总量的比例最高;氮肥一次性深施处理(N240/1)花后干物质和氮积累量较高,但所占比例较低;习惯施肥处理(N 280/2)干物质和氮积累量较低,但所占比例较高。由于关于一次性施肥存在较多争议,因此尚不能认为氮肥一次性深施方式可以替代农民习惯施肥;而氮肥减量后移处理既获得了较高的产量,也提高了氮效率,是一种科学的施肥方式。

N肥深施深度对小麦吸收利用N的影响

本文应用15N示踪技术，在川中紫色土上进行了聚全的表层施肥（施肥深度1-2cm）、中层施肥（深施25cm）、底层施肥（深施45cm）和平作表层施肥不同处理小麦吸N特性等的研究。结果表明：N肥利用率是“平＋表施”＞“聚＋底施”＞“聚＋中施”＞“聚＋表施”，处理间N肥利用率最高是23．78％，小麦一生有38.7-44.1％的N来自肥料。小麦拔节以前无论是聚土还是平作，其表层施肥地上部分NDFF值极显著地大于中层和底层施肥；“平＋表施”、“聚＋底施”、“聚＋中施”比“聚＋表施”显著地增加了小麦产量。

深部液流转向与调驱技术现状与对策

目前水驱仍是高含水、高采出程度即"双高"油田的主要开采方式。分析了近年来深部液流转向与调驱的技术进展及存在的问题,认为有必要强化针对深部液流转向与调驱的油藏基础理论研究,攻关水流优势通道分布定量描述技术,实现对高含水后期存在水流优势通道油藏渗流规律的合理描述。另一方面,从工艺、材料等诸方面着力解决堵剂的"有效深部放置"问题。此外,加快试验应用在线注入设备,满足深部液流转向与调驱技术规模化、同步化的需要。

玉米秸秆深还剂量对土壤水分的影响

针对目前秸秆浅旋和直接翻压还田存在的问题,设计了秸秆机械化集中深还田试验,为探讨秸秆集中还田后不同时期的土壤水分分布状况,对不同部位的土壤水分进行了周年监测,结果显示:秸秆集中的部位与玉米播种部位隔开适宜的距离,秸秆还田形成的大孔隙将不会影响玉米的正常生长,秸秆还田的第一年,秸秆处于强吸水阶段,秸秆集中部位的土壤含水量随秸秆剂量的加大而降低、秸秆深还第二年,秸秆仍处于吸水状态,其趋势与第一年类似,但降低的幅度比第一年小;随着秸秆腐解,土壤与秸秆之间的含水量趋近于平衡,其蓄水与供水功能逐渐显现。秸秆深还后土壤水分运动始终处于饱和状态,因此应根据土壤与秸秆的水分状况实施机械化深还,以使秸秆与土壤的水分尽快融合,真正达到保水保肥的目的。

施肥方式对土壤水肥分布特征影响

通过室内土柱试验研究,分析了灌溉施肥与不同深度的土壤施肥处理对土壤水力特性及水肥分布的影响。结果表明,土壤施肥处理不同程度地降低了土壤入渗性能,且施肥层越浅对土壤的减渗作用越大。各处理的土壤水分经过24h再分布过程后无显著差异。在灌溉施肥条件下,土壤中的硝态氮分布较均匀,而磷和钾滞留在土壤表层。对于土壤施肥情况,在灌溉结束后硝态氮被淋洗到湿润峰以上10cm附近,P和K的浓度峰值发生在施肥层附近。施肥深度决定了灌溉结束后浓度峰值出现的位置,施肥层越深,养分浓度的峰值出现的位置越深。

水稻基肥尿素干施与湿施对氮素损失及水稻氮素吸收的影响

运用大型原状土柱在田间条件下比较了水稻基肥干耕施(干施)与湿耙施(湿施)对氮素损失与水稻氮素吸收的影响,试验设尿素干施、湿施与对照3个处理,同步测定了施肥后小区的氨挥发、淋洗以及水稻的吸氮量。结果表明:(1)干施法氨挥发显著低于湿施法,模拟试验分别为40.1与68.8 kg hm-2,占施氮量的13.4%与22.9%,2004年的大田试验分别为19.2与26.2 kg hm-2,占施氮量的7.7%与10.4%;(2)而干施法的总氮(TN)淋洗量显著大于湿施法,分别为14.3与4.6 kg hm-2,占施氮量的4.8%与1.5%,氮的淋洗以NO3--N为主,占总量的73.7%～97.3%,两者的NH4+-N淋洗量差别很小;(3)与湿施法相比,干施法净减少氮肥损失19.0 kg hm-2,水稻吸氮量增加15.1 kg hm-2,氮肥利用率提高了5个百分点,产量略有提高,而土壤含氮量没有显著变化。因此,水稻基肥尿素干深施法是一项值得推广的施肥方法。