模拟降雨对工程建设区裸露坡地产流产沙及氮素流失的影响

为揭示不同降雨强度下工程建设区裸露坡地土壤侵蚀过程和氮素流失特征,采用人工模拟降雨的方法,研究不同降雨强度(1,1.5,2mm/min)和处理(裸地、坡面覆盖纱网)对工程裸露坡地产流产沙及氮素流失的影响。结果表明:(1)径流强度、径流含沙量、土壤剥蚀率都与降雨强度呈正相关关系,土壤入渗率与降雨强度呈现负相关关系。(2)累积泥沙量与累积径流量在裸地处理中呈现线性函数关系,在纱网处理中呈现幂函数关系。(3)地表径流中氮素流失浓度随降雨历时呈现"下降—稳定"趋势,氮素流失量随降雨强度的增加而增大,其中NO_3~-—N流失量占总氮比重高于NH_4~+—N。(4)土壤坡面覆盖纱网后能有效控制水土流失量和氮素流失量,其中径流量和NO_3~-—N流失量在小雨强处降低效果显著,分别降低了60.21%和56.74%;TN流失量和NH_4~+—N流失量在小、中雨强处降低效果较好,均达到59.26%以上;侵蚀泥沙量在小、中、大雨强处均降低了79%以上。说明土壤坡面覆盖纱网这一措施对降低工程建设区裸露坡地土壤侵蚀量和氮素流失量具有效果显著,可以作为工程建设区水土流失防止措施。     

Hole fertilization in the root zone facilitates maize yield and nitrogen utilization by mitigating potential N loss and improving mineral N accumulation

Reducing environmental impacts and improving N utilization are critical to ensuring food security in China.  Although root-zone fertilization has been considered an effective strategy to improve nitrogen use efficiency (NUE), the effect of controlled-release urea (CRU) applied in conjunction with normal urea in this mode is unclear.  Therefore, a 3-year field experiment was conducted using a no-N-added as a control and two fertilization modes (FF, furrow fertilization by manual trenching, i.e., farmer fertilizer practice; HF: root-zone hole fertilization by point broadcast manually) at 210 kg N ha^–1 (controlled-release:normal fertilizer=5:5), along with a 1-year in-situ microplot experiment.  Maize yield, NUE and N loss were investigated under different fertilization modes.  The results showed that compared with FF, HF improved the average yield and N recovery efficiency by 8.5 and 22.3% over three years, respectively.  HF had a greater potential for application than FF treatment, which led to increases in dry matter accumulation, total N uptake, SPAD value and LAI.  In addition, HF remarkably enhanced the accumulation of ¹⁵N derived from fertilizer by 17.2% compared with FF, which in turn reduced the potential loss of ¹⁵N by 43.8%.  HF increased the accumulation of N in the tillage layer of soils at harvest for potential use in the subsequent season relative to FF.  Hence, HF could match the N requirement of summer maize, sustain yield, improve NUE and reduce environmental N loss simultaneously.  Overall, root-zone hole fertilization with blended CRU and normal urea can represent an effective and promising practice to achieve environmental integrity and food security on the North China Plain, which deserves further application and investigation.     

包膜尿素与普通尿素配施对稻田氨挥发的影响

为有效减少平原河网双季稻种植区农田氮素（N）损失并提高N肥利用率，采用聚氨酯包膜尿素与普通尿素掺混一次性施肥技术，探究控释掺混肥对早稻季氨挥发损失及N肥利用率的影响。连续两年（2018—2019年）在湖南益阳开展田间试验，设置不施N肥（CK）、常规施肥（CF）、聚氨酯包膜尿素（PuCU）、聚氨酯包膜尿素与普通尿素以6∶4比例配比（0.6PuCU+0.4CF）共4个处理，采用半密闭通气法监测水稻生育期间氨挥发特征。结果表明： CF和0.6PuCU+0.4CF处理稻田氨挥发主要发生在移栽后10 d内，峰值出现于第2~3天和第10天；而PuCU处理整个早稻生长季氨挥发通量缓慢，略高于CK处理。早稻全生育期CF处理氨挥发损失量（率）最高，达39.48 kg·hm^-2（22.22%），N肥吸收利用率（NRE）和N肥农学利用率（NAE）分别为29.19%和13.82 kg·kg^-1；PuCU和0.6PuCU+0.4CF处理氨挥发损失量（率）分别为12.01 kg·hm^-2（3.91%）和20.70 kg·hm^-2（9.70%），NRE分别为60.22%和71.36%，NAE分别为18.99 kg·kg^-1和20.34 kg·kg^-1。其中，0.6PuCU+0.4CF和PuCU处理早稻季总计氨挥发损失量较CF处理分别降低47.57%和69.56%，而NRE分别提高163.08%和116.29%，NAE分别提高69.85%和55.97%。Elovich方程能较好地拟合稻田氨挥发累积量随时间的变化趋势，各处理相关系数均达到极显著水平。相关分析表明，早稻季氨挥发通量与田面水NH₄⁺-N浓度及pH呈显著正相关。研究表明，聚氨酯包膜尿素一次性基施能有效避免施肥后NH₄⁺-N的急剧升高，减少稻田氨挥发损失，并提高早稻N肥利用率，而将其与尿素按比例进行互配能进一步促进N素吸收，提高N素利用效率，但氨挥发减排效果较单施聚氨酯包膜尿素低。     

新工科背景下混合式教学在“食品化学”课程教学中探索

为了更好地适应新工科建设人才培养的要求,充分发挥线上学习和线下教学的特点,以"食品化学"课程教学为例,将两者进行有机融合探索线上线下混合式教学模式。结果表明,"食品化学"采用混合式教学模式,丰富了学生的学习资源,调动了学生的学习积极性,提高了学生的学习效率,为培养创新型、应用型人才提供一条参考的课程教学模式。     

基于SPOC高职“食品生物化学”混合式教学的实践

分析了高职“食品生物化学”课程的教学现状,构建了基于SPOC的线上线下混合式教学模式。在这种教学模式中,充分发挥信息技术的优势实现线上线下教学内容的有机融合;注意多种教学方法灵活应用,实现良好的教学互动氛围;建设高质量的在线课程,激发学生的求知欲;强化学习反馈,促进学习效果与能力稳步提升。线上线下混合式教学的实践,解决了学时少和部分学生学习兴趣不浓的问题,有效促进高职学生的自主学习,提高了教学质量。