英文文献：Does Soil Nutrient and Remobilization Affect Harvest Strategy and Nutrient Management Decisions for Switchgrass Feedstock?-土壤养分和再迁移是否影响柳枝稷原料的收获策略和养分管理决策?传统的分析方法用于确定最经济的以农民为基础的收获系统和生产柳枝稷原料的相应养分管理策略，没有考虑与土壤养分开采相关的农艺问题和随后的经济问题
英文文献作者：Haque, Mohua,Biermacher, Jon T.,Guretzky, John A.,Kering, Maru K.
英文文献摘要：
Conventional analytical methods used to determine the most economical farmer-based harvest system and corresponding nutrient management strategy for producing switchgrass (Panicum virgatum L.) feedstock do not consider agronomic and subsequent economic problems associated with soil nutrient mining. The objective of this study was to determine the long-term, economically sustainable harvest system and corresponding rates of N, P and K for producing switchgrass feedstock in the southern Great Plains. Data collected from a four-year, two-location agronomic field trial in south-central Oklahoma were used for analyses that included two harvest systems, including (1) a single cut after a hard freeze, after plant senescence (WNTR), and a summer cut at plant maturity in July followed by a second cut after a hard freeze, after plant senescence (SMWNTR). Each system received 0, 45, 90, 135, 179, and 224 kg of N ha-1 yr-1, and received 67 and 135 kg ha-1 yr-1 of P2O5, and K2O, respectively. A standard forage analysis was used to determine the concentrations of N, P and K nutrients in the feedstock harvested from each plot in each year and location and converted to N, P2O5 and K2O (kg ha-1) equivalents. These data were used to determine the extent of soil nutrient mining or nutrient remobilization for each harvest system. Two separate econometric models were estimated and used with enterprise budgeting techniques to compare the effects of harvest system and nutrient levels on yield and economic net return. Model 1 represents the conventional economic approach that uses the fertilizer treatments applied in the experiment. Model 2 reflects the long-term, economic sustainability approach and uses the nutrient concentration levels calculated from the switchgrass forage samples collected in the study. For a farm-gate feedstock price of $83 Mg-1 and nutrients priced at 2012 market rates, the results showed that it was economically sustainable to harvest only once after a hard freeze (i.e., the WNTR system) and apply 84, 28 and 50 kg ha-1 yr-1 of N, P2O5 and K2O, respectively. For this base-case scenario, farmers earned $79 ha-1 more net return with the economic sustainability approach compared to the results generated from the conventional economic approach. However, the comparative results between the two economic approaches are quite sensitive to the assumptions about yield response to nutrient concentration levels and assumptions about the percentage of nutrients remobilized in the WNTR system that are actually available for reuse by switchgrass plants.

本研究的目的是确定在美国南部大平原地区生产柳枝稷原料所需的长期、经济上可持续的收获制度和相应的氮、磷、钾率。从四年收集的数据,在俄克拉何马州中南部two-location农艺现场试验被用于分析包括两个收获系统,包括(1)一个切硬冻结后,在植物衰老(WNTR),和一个夏天在植物成熟之后,7月第二个切硬冻结后,在植物衰老(SMWNTR)。每个系统分别接收0、45、90、135、179和224 kg的N ha-1 yr-1，接收67和135 kg的ha1 yr-1 P2O5和K2O。使用标准饲料分析来确定每年从每个小区收获的饲料中氮、磷和钾营养素的浓度，并将其转化为N、P2O5和K2O (kg ha-1)等效物。这些数据用于确定每个收获系统的土壤养分开采或养分再转化的程度。估计了两个单独的计量经济学模型，并与企业预算技术一起使用，以比较收获制度和养分水平对产量和经济净收益的影响。模型1代表了在试验中使用化肥处理的传统经济方法。模型2反映了长期的、经济的可持续性方法，并使用研究中收集的柳枝稷饲料样本计算出的养分浓度水平。对于农场饲料价格为83 Mg-1美元，营养品价格为2012年市场价格的农场，结果表明，仅在硬冻后收获一次(即WNTR系统)，施用氮、P2O5和K2O的84 kg、28 kg和50 kg ha-1 yr-1在经济上是可持续的。在这个基本情况下，与传统经济方法产生的结果相比，农民使用经济可持续性方法多获得79美元ha-1的净收益。然而，这两种经济方法的比较结果对有关产量对养分浓度水平的响应的假设以及对柳枝稷实际可重复利用的WNTR系统中营养素再转化百分比的假设相当敏感。