How effective are broad-scale nutrient mass balances for determining the sustainability of lot-feed manure application?

Nutrient mass balances have been used to assess a variety of land resource scenarios, at various scales. They are widely used as a simple basis for policy, planning, and regulatory decisions but it is not clear how accurately they reflect reality. This study provides a critique of broad-scale nutrient mass balances, with particular application to the fertiliser use of beef lot-feeding manure in Queensland.Mass balances completed at the district and farm scale were found to misrepresent actual manure management behaviour and potentially the risk of nutrient contamination of water resources. The difficulties of handling stockpile manure and concerns about soil compaction mean that manure is spread thickly over a few paddocks at a time and not evenly across a whole farm. Consequently, higher nutrient loads were applied to a single paddock less frequently than annually. This resulted in years with excess nitrogen, phosphorus, and potassium remaining in the soil profile. This conclusion was supported by evidence of significant nutrient movement in several of the soil profiles studied.Spreading manure is profitable, but maximum returns can be associated with increased risk of nutrient leaching relative to conventional inorganic fertiliser practices. Bio-economic simulations found this increased risk where manure was applied to supply crop nitrogen requirements (the practice of the case study farms, 200–5000 head lot-feeders).Thus, the use of broad-scale mass balances can be misleading because paddock management is spatially heterogeneous and this leads to increased local potential for nutrient loss. In response to the effect of spatial heterogeneity policy makers who intend to use mass balance techniques to estimate potential for nutrient contamination should apply these techniques conservatively.     

粪肥施用对抗生素在土壤上吸附的影响

磺胺类抗生素和氟苯尼考(FFC)是浙江省普遍使用的抗生素，在土壤上吸附弱而易于迁移，存在较高的环境风险.近年来，粪源抗生素对农田土壤潜在风险的研究多是在实验室条件下添加粪肥的方式进行，无法评估自然施肥状态下抗生素的污染风险.因此以浙江省长期施用不同肥料(鸡粪、猪粪和化肥)的5种旱地农田土壤[临安(LA)、嘉善(JS)、龙游(LY)、开化(KH)和金华(JH)]为对象，选用4种常用的抗生素[磺胺嘧啶(SD)、磺胺二甲基嘧啶(SMT)、磺胺甲基异噁唑(SMZ)和FFC],进行批量平衡实验，探究土壤不同类型和粪肥类型对抗生素在土壤中吸附的影响.结果表明，4种抗生素在实验土壤中的吸附都较弱，吸附次序为：SMT(1.44～13.23 mg⁽1-(1/n))·L^1/n·kg^-1)>SMZ(0.73～6.05 mg⁽1-(1/n))·L^1/n·kg^-1)>SD(0.16～5.57 mg⁽1-(1/n))·L^1/n·...     

Nutrient budgets: sustainability assessment of rainfed lowland rice-based systems in northeast Thailand

In northeast Thailand, the sustainability of rainfed lowland rice-based systems, the dominant land-use system (LUS) in the region, is a concern for the welfare of the population in this relatively poor region. Poor soil fertility and low inputs are seen as major causes of this lack of sustainability. In this context, the assessment of nutrient budgets is seen as a powerful tool for the assessment of critical components of the sustainability of this particular LUS. Biophysical, socioeconomic, and management-related data on the farming systems were collected for 30 farms in Ubon Ratchathani Province, northeast Thailand. A relational database system (RDBS) was developed to manage and analyze the data. The RDBS includes a calculation procedure for the semi-automatic generation of partial nutrient balances. Partial nutrient balances are good indicators for some critical components of sustainability, and important for decision support on soil fertility management when considered with the additional factors that are required for a full nutrient balance.For the rice-based systems of 30 farms, mean partial balances were 12 kg N ha⁻¹, 8 kg P ha⁻¹, and 7 kg K ha⁻¹ per year. Large variations in partial N, P, and K balances exist among different farms and, even more so, for different land utilization types (LUTs). The LUTs are distinct cropping system–management combinations that occur down to the subfield level. Many of the partial balances assessed were negative.Farmers manage nutrients for similar parcels of land in very different ways. This results in the observed large variation in partial nutrient balances, even for the same type of land use within the same farm. These results confirm the high inter-farm and intra-farm variability for partial balances of N, P, and K of several preliminary studies. Farmer interviews and field surveys revealed that different socioeconomic factors appear to be related with inter- and intra-farm variability in nutrient budgets. In addition, the socioeconomic component of the case study revealed that diversification of income sources, particularly off-farm employment, had a larger impact on household income than rice production. Furthermore, while many less well-off households had a greater reliance on rice production, many farms with high off-farm and non-rice farm income had a higher total production of rice.The nutrient balance approach, starting with partial nutrient balances, may become an important component of a dynamic and site-specific decision support tool (DST) for nutrient management, and a relational database of the form used in this study may become a key element.     

波纹板弯曲模

正弦波纹板的回弹量较大。此文详细介绍波纹板弯曲模的参数计算模具结构以及制造、使用模具的技术要领。     

规模化牲畜养殖场的环境效应及其对策

通过对江苏省2个典型地区的4个生猪养殖场的饲料、牲畜排泄物、土壤、地表水及水土水中养分状况的调查采样与分析，对牲畜规模养殖的环境效应进行了评价。在此基础上，对牲畜养殖排泄物的养分管理与资源化利用提出了建议，并通过对牲畜排泄物中养分状况及作物养分需求状况的分析统计，提出了种植－养殖区域养分平衡管理模式。     

河流水质1号模型探讨

介绍了河流水质模型70年来的发展历程和目前存在的不足之处,论述了河流水质1号模型(RwQM1)的研究成果.河流水质1号模型从活性污泥模型ASM中发展而来,并推出了建立模型的决策化方法,其对生化反应模型的完善而成为河流水质模型发展的一个标准平台.本文重点介绍了其在生化反应模型方面的进展,并和QUAL2E做了比较.     

污水生物处理单元平衡分析方法研究(Ⅰ)

依据热力学第二定律建立了污水处理单元Yong平衡分析的灰箱模型，提出了进行处理单元过程Yong评价的指标体系．在热力学意义上，污水生物处理是通过微生物内部的Yong耗散来消耗污水污染物能量的过程，推动该过程加速进行需要耗费外部的Yong．因此，节能的主要目的是节Yong，即应防止推动力过剩造成反应器单元的外部Yong损失．这一方法体系将为合理科学评判处理过程能耗机制奠定重要的理论基础．     

汽车钢板胀形区成形极限图的预测与验证

通过对胀形区成形极限图的理论分析和经验修正,建立了胀形区成形极限图的计算公式,经试验验证,在不同钢种、不同退火工艺、不同镀锌方式、不同表面处理方式下,按此公式计算的结果都能很好地符合试验结果。     

多点成形--金属板材柔性成形的新技术

多点成形是一种板材三维曲面柔性成形的新技术.简述了多点成形的基本原理与系统构成并介绍了几种成形方式.在多点成形中,厚板曲面件可直接成形,薄板曲面件则采用柔性压边技术进行成形.利用多点成形技术的柔性特点还能实现分段成形、反复成形、多道成形以及闭环成形等新的板材成形工艺.     

水解池—稳定塘工艺越冬技术措施研究

为提高污水稳定塘在冬季的处理效果,用水解池作为预处理措施,以降低有机负荷并改善污水的可生物降解性,因而提高了低温条件下的降解速率.通过对系统的热量平衡分析和技术经济分析,研究采用塑料大棚减慢稳定塘热量散失的措施.结合研究其它一些强化措施,提出了能适合北方地区冬季气候特点的稳定塘工艺流程.