Ghebremichael L T, Veith T L, Cerosaletti P E, Dewing D E, Rotz C A
Rubenstein School of Environment and Natural Resources, University of Vermont, Burlington, Vermont 05401, USA.
J Dairy Sci. 2009 Aug;92(8):4086-99. doi: 10.3168/jds.2009-2024.
In 2008, corn grain prices rose $115/t of DM above the 2005 average. Such an increase creates tight marginal profits for small (<100) and medium-sized (100 to 199) dairy farms in the northeastern United States importing corn grain as animal feed supplement. Particularly in New York State, dairy farmers are attempting to avoid or minimize profit losses by growing more corn silage and reducing corn grain purchases. This study applies the Integrated Farm Systems Model to 1 small and 1 medium-sized New York State dairy farm to predict 1) sediment and P loss impacts from expanding corn fields, 2) benefits of no-till or cover cropping on corn fields, and 3) alternatives to the economic challenge of the current farming system as the price ratio of milk to corn grain continues to decline. Based on the simulation results, expanding corn silage production by 3% of the cultivated farm area increased sediment and sediment-bound P losses by 41 and 18%, respectively. Implementing no-till controlled about 84% of the erosion and about 75% of the sediment-bound P that would have occurred from the conventionally tilled, expanded corn production scenario. Implementing a conventionally tilled cover crop with the conventionally tilled, expanded corn production scenario controlled both erosion and sediment-bound P, but to a lesser extent than no-till corn with no cover crop. However, annual farm net return using cover crops was slightly less than when using no-till. Increasing on-farm grass productivity while feeding cows a high-quality, high-forage diet and precise dietary P levels offered dual benefits: 1) improved farm profitability from reduced purchases of dietary protein and P supplements, and 2) decreased runoff P losses from reduced P-levels in applied manure. Moreover, alternatives such as growing additional small grains on marginal lands and increasing milk production levels demonstrated great potential in increasing farm profitability. Overall, it is crucial that conservation measures such as no-till and cover cropping be implemented on new or existing corn lands as these areas often pose the highest threat for P losses through runoff. Although alternatives that would likely provide the largest net profit were evaluated one at a time to better quantify their individual impacts, combinations of these strategies, such as no-till corn plus a minimum-till cover crop, are recommended whenever feasible.
2008年,玉米谷物价格比2005年的平均价格高出115美元/吨干物质。这种价格上涨使得美国东北部进口玉米谷物作为动物饲料补充剂的小型(<100头)和中型(100至199头)奶牛场的边际利润变得紧张。特别是在纽约州,奶农们试图通过种植更多的玉米青贮饲料并减少玉米谷物采购来避免或尽量减少利润损失。本研究将综合农场系统模型应用于纽约州的1个小型和1个中型奶牛场,以预测:1)扩大玉米种植面积对沉积物和磷流失的影响;2)玉米田免耕或覆盖作物种植的益处;3)随着牛奶与玉米谷物价格比持续下降,应对当前养殖系统经济挑战的替代方案。根据模拟结果,将玉米青贮产量提高到耕地面积的3%,沉积物和与沉积物结合的磷流失分别增加了41%和18%。实施免耕控制了约84%的侵蚀以及约75%的与沉积物结合的磷流失,这些流失原本会在传统耕作、扩大玉米生产的情况下发生。在传统耕作、扩大玉米生产的情况下实施传统耕作的覆盖作物,对侵蚀和与沉积物结合的磷都有控制作用,但程度小于不种植覆盖作物的免耕玉米。然而,使用覆盖作物时农场的年净收益略低于使用免耕时。在给奶牛饲喂高质量、高草料日粮并精确控制日粮磷水平的同时提高农场草料生产力有双重好处:1)通过减少日粮蛋白质和磷补充剂的采购提高农场盈利能力;2)通过减少施用粪肥中的磷含量降低径流磷流失。此外,在边际土地上种植更多小谷物和提高牛奶产量水平等替代方案在提高农场盈利能力方面显示出巨大潜力。总体而言,至关重要的是在新的或现有的玉米田上实施免耕和覆盖作物种植等保护措施,因为这些区域往往对径流造成的磷流失构成最大威胁。尽管为了更好地量化其各自的影响,一次只评估了可能带来最大净利润的替代方案,但只要可行,建议采用这些策略的组合,如免耕玉米加最小耕作覆盖作物。