Rotz C A, Kamphuis G H, Karsten H D, Weaver R D
USDA, Agricultural Research Service, Pasture Systems and Watershed Management Research Unit, University Park, PA 16802, USA.
J Dairy Sci. 2007 Aug;90(8):3961-79. doi: 10.3168/jds.2006-527.
The current market demand and price for organic milk is encouraging dairy producers, particularly those on smaller farms, to consider organic production as a means for improving the economic viability of their operations. Organic production systems vary widely in scale, in practices, and across agroclimatic settings. Within this context, case studies of 4 actual organic dairy farms were used to characterize existing systems in Pennsylvania. Based on data from these farms, a whole-farm simulation model (Integrated Farm System Model) was used to compare 4 production systems representing organic grass, organic crop, conventional crop with grazing, and conventional confinement production. The performance of each of these systems was simulated over each year of 25 yr of central Pennsylvania weather data. Simulation results indicated that farm level accumulation of soil P and K may be a concern on organic farms that use poultry manure as a primary crop nutrient source, and that erosion and runoff loss of P may be of concern on organic farms producing annual crops because more tillage is required for weed control. Whole-farm budgets with prices that reflect recent conditions showed an economic advantage for organic over conventional production. A sensitivity analysis showed that this economic advantage depended on a higher milk price for producers of organic milk and was influenced by the difference in milk production maintained by herds using organic and conventional systems. Factors found to have little effect on the relative profitability of organic over conventional production included the differences between organic and conventional prices for seed, chemicals, forage, and animals and the overall costs or prices assumed for organic certification, machinery, pasture fencing, fuel, and labor. Thus, at the current organic milk price, relative to other prices, the case study organic production systems seem to provide an option for improving the economic viability of dairy operations of the scale considered in Pennsylvania. To motivate transition to organic systems, the economic advantage found requires the persistence of a substantial difference between conventional and organic raw milk prices.
当前有机牛奶的市场需求和价格促使乳制品生产商，尤其是那些小型农场主，将有机生产视为提高其经营经济可行性的一种方式。有机生产系统在规模、实践以及不同农业气候环境方面差异很大。在此背景下，对宾夕法尼亚州4个实际有机奶牛场进行了案例研究，以描述现有系统的特征。基于这些农场的数据，使用一个全农场模拟模型（综合农场系统模型）来比较4种生产系统，分别代表有机草地、有机作物、常规作物带放牧以及常规圈养生产。利用宾夕法尼亚州中部25年气象数据中的每年数据对这些系统的性能进行了模拟。模拟结果表明，对于将禽畜粪便作为主要作物养分来源的有机农场，土壤磷和钾在农场层面的积累可能是一个问题；而对于种植一年生作物的有机农场，磷的侵蚀和径流损失可能令人担忧，因为为控制杂草需要更多的耕作。反映近期情况的价格下的全农场预算显示，有机生产比传统生产具有经济优势。敏感性分析表明，这种经济优势取决于有机牛奶生产商的牛奶价格较高，并且受到使用有机和传统系统的牛群维持的牛奶产量差异的影响。发现对有机生产相对于传统生产的相对盈利能力影响较小的因素包括种子、化学品、饲料和动物的有机与传统价格差异，以及假定的有机认证、机械、牧场围栏、燃料和劳动力的总体成本或价格。因此，在当前有机牛奶价格下，相对于其他价格而言，案例研究中的有机生产系统似乎为提高宾夕法尼亚州所考虑规模的奶牛场经营的经济可行性提供了一种选择。为了促使向有机系统转变，所发现的经济优势需要传统和有机原料奶价格之间持续存在显著差异。
