Modeling the Impacts of Farming Practices on Water Quality in the Little Miami River Basin

Since intensive farming practices are essential to produce enough food for the increasing population, farmers have been using more inorganic fertilizers, pesticides, and herbicides. Agricultural lands are currently one of the major sources of non-point source pollution. However, by changing farming practices in terms of tillage and crop rotation, the levels of contamination can be reduced and the quality of soil and water resources can be improved. Thus, there is a need to investigate the amalgamated hydrologic effects when various tillage and crop rotation practices are operated in tandem. In this study, the Soil Water Assessment Tool (SWAT) was utilized to evaluate the individual and combined impacts of various farming practices on flow, sediment, ammonia, and total phosphorus loads in the Little Miami River basin. The model was calibrated and validated using the 1990–1994 and 1980–1984 data sets, respectively. The simulated results revealed that the SWAT model provided a good simulation performance. For those tested farming scenarios, no-tillage (NT) offered more environmental benefits than moldboard plowing (MP). Flow, sediment, ammonia, and total phosphorus under NT were lower than those under MP. In terms of crop rotation, continuous soybean and corn–soybean rotation were able to reduce sediment, ammonia, and total phosphorus loads. When the combined effects of tillage and crop rotation were examined, it was found that NT with continuous soybean or corn–soybean rotation could greatly restrain the loss of sediments and nutrients to receiving waters. Since corn–soybean rotation provides higher economic revenue, a combination of NT and corn–soybean rotation can be a viable system for successful farming.     

旱三熟带状轮作小春预留行栽油菜技术

本文根据南充地区冬春气候特点,并针对旱地实行的中厢分带间套种植小春预留行未充分利用的状况,从1984年开始在预留行进行了栽油菜研究。结果表明,一般亩增菜籽30～40kg,增加产值34～45元,纯收入21～32元,并找出了适于预留行栽植的油菜品种和配套栽培技术。     

爆炸荷载作用下岩石的变形与破坏研究(Ⅰ)

无论是矿山工程、隧道工程中钻孔爆破效率的提高、工程爆破领域爆破振动参数的预测,还是最近一系列高技术常规局部战争中钻地炸弹对地下坚固目标的破坏,在不考虑岩石中强爆炸引起的光子和电磁辐射等极端效应情况下,都亟待要求对岩石中爆炸引起的应力、变形及其它运动参数和破坏效应作出比较准确的评估。目前对此问题的研究尚只能达到大致的机理及景象的定性认识和描述,定量上的确定存在数量级的误差,尤其是爆炸和冲击的近区,误差更大。其原因在于岩石中爆炸产生的变形和破坏特征,不仅与作用时发生相应的物理及力学运动密切相关,而且强烈地受岩石自身构造缺陷水平及其变化的制约。本文概述了爆炸作用下岩石的动力变形与破坏研究之现状。研究中考虑了岩石的构造特点及其对基本力学性状的影响,并简述了其研究的新趋向。     

地球自转不规则变化与苏皖及其附近地区中强地震的相关性

地球自转不规则变化的加速段与苏皖及其附近地区中强地震的相关性较好。用周期图分析的拟合曲线外推至 2 0 2 0年 ,可见这次地球自转不规则变化加速段将持续到 2 0 0 4年左右。因此 ,苏皖及其附近地区中强地震活动将持续到 2 0 0 4～ 2 0 0 5年左右。根据美国NEOS提供的数据 ,目前地球自转确在加速段。