从化区农田耕层土壤有效硅空间分布及影响因素

为探究广州市从化区农田土壤有效硅空间分布及影响因素，以期为促进我国粮食主产区水稻产量增长提供科学依据和参考，采用描述性统计、地统计学、相关性分析与GIS （地理信息系统）技术结合的方法对从化区土壤有效硅开展研究。结果表明，研究区土壤有效硅平均含量为60.31 mg·kg^-1，总体偏低，并呈现中度变异；在中心区域、粮食主产区和丘陵地带，土壤有效硅含量较高；有效硅含量与土壤pH、有机质含量、黏粒含量呈正相关，土地利用方式、成土母质对其也有显著影响。研究表明，在所考虑的影响因素中，成土母质对从化区农田土壤有效硅的影响程度居于首位。     

“彗星式通孔”减阻犁的试验研究

在分析犁耕阻力形成的基础上,提出改善摩擦面摩擦条件的设想。通过在铧式犁的犁胸和犁铧上设计“彗星式通孔”,使犁耕过程中犁面与土垡的接触界面形成气液相介质层,改变土壤与金属的摩擦性能,减小摩擦系数,从而达到减摩减阻的目的。田间试验表明:设计有“彗星式通孔”的犁在水耕时可减小犁耕比阻8％～12％,旱耕时犁耕比阻也可减小2.5％～3.5％左右。     

蟹塘双体投饵船行驶阻力分析及船型优化

采用双体投饵船是实现蟹塘遍撒投饵的可行方案之一。在航道存在水草的情况下,为减小巡航阻力、提升投饵船续航能力,设计尖底和圆棱底2种新型船底型线,并基于雷诺平均方程,构建船体在不同吃水深度和速度下的动力学计算模型。以平底船为对照船体,对比分析CFD数值计算与水池试验阻力,数据误差在9.6%以内,显示了计算模型的有效性。计算结果表明:圆棱底船在船速0.50~2.00 m/s时具有更好的减阻效果,与平底船相比减阻率在3.92%~16.27%;圆棱底船能减小底面与水草的滑动摩擦阻力;投饵船经济船速应小于1.50 m/s,经济吃水深度应小于0.18 m。所研发的圆棱底船的进一步测试结果表明了所提优化方案的有效性。     

Erosion and covered zones altered by surface coverage effects on soil nitrogen and carbon loss from an agricultural slope under laboratory-simulated rainfall events

Soil erosion, one of the most serious environmental concerns, might remove topsoil and essential element from terrestrial land. However, few attentions have been given to investigating how soil erosion regimes affect soil carbon and nitrogen loss. Therefore, this study investigated the effects of surface coverage rates (83%, 67%, 50%, 33%, 17% and 0%) and two positions (up- and downslope) on erosion regimes and its associated soil nitrogen and carbon loss under a sequence of six rainfalls (R1-R6). These results showed that the sediment concentrations with 33% (R4) and 17% (R5) coverage downslope were significantly lower than those with coverage upslope, whereas there was no significant difference between the runoff rates of the two slopes. Thus, surface coverage at different positions induced two soil erosion regimes (deposition- and transport-dominated processes). Dynamics of the DON and DIN concentrations indicated different release processes of soil nitrogen into runoff. The DON contributed to a substantial amount of soil nitrogen loss, which accounted approximately 81% of the organic form. The SBOC is significantly correlated with sediment-enriched clay particles from the deposition-dominated processes and is higher than that from the transport-dominated processes. The DOC is significantly correlated with Rr for transport-dominated processes. These results illustrated the critical role of erosion regimes in soil organic carbon loss in dissolved or sediment-bound form. It is concluded that erosion/covered zones altered by surface coverage could produce transport- and deposition-dominated erosion regimes and consequently affect soil carbon and nitrogen loss. In addition, these results demonstrated that surface coverage pattern may efficiently control soil erosion and soil carbon and nitrogen loss.     

基于野外原位光谱的棉田耕层土壤全氮含量监测模型研究

针对可见光和近红外光穿透力不强、难以监测到耕层土壤全氮的问题，以石河子垦区播前棉田土壤为研究对象，获取3种不同土壤质地类型的原位光谱及不同耕层的土壤全氮含量信息，通过Savitzky-Golay平滑处理及最大归一化处理对土壤原位光谱进行预处理，并利用广义传播神经网络(GRNN)、随机森林回归(RFR)、支持向量机回归(SVR)、最小二乘回归等4种建模方法，建立和筛选出不同土壤质地类型的棉田耕层土壤含量的最佳监测模型。结果表明：(1)不同建模方法在各耕层监测精度不同，在浅、中、深耕层表现最佳的监测模型均为GRNN模型（R²分别为0.72、0.68、0.63）。(2)优化后的NGRO-GRANN模型监测精度高于GRNN模型，在浅、中、深三个耕层的预测精度提高16.2%~30.2%。(3)基于原位光谱建立不同耕层的土壤全氮监测模型具有较好的监测效果，且大量简化了室内光谱处理的繁琐步骤。该研究为野外原位光谱快速获取棉田播前土壤各耕层养分信息提供了理论基础与技术支撑，具有一定的可行性与鲁棒性。     

精准扶贫视角下企业与贫困户双赢的商业模式创新研究

以六家涉农企业为例，运用扎根理论编码方法，提炼出精准扶贫导向的商业模式构成要素。基于探索性的多案例研究，结果发现：有效参与精准扶贫，需要企业设计出精准扶贫导向的商业模式，这一方面需要政府的引导及政策支持，另一方面需要企业进行商业模式创新，以实现企业与贫困户双赢。而企业与贫困户双赢的商业模式创新，首先，需要企业提出一个新的价值主张；其次，从本地能力、价值网络、关键资源能力、利益联结机制、盈利模式五大要素开展价值支撑措施；最后，为确保价值支撑不受侵蚀及价值主张能够实现，还要做好风险防范与应对的价值保持工作。