Nelson Richard G, Hellwinckel Chad M, Brandt Craig C, West Tristram O, De La Torre Ugarte Daniel G, Marland Gregg
Engineering Extension, Kansas State Univ., Manhattan, KS 66502, USA.
J Environ Qual. 2009 Feb 6;38(2):418-25. doi: 10.2134/jeq2008.0262. Print 2009 Mar-Apr.
Changes in cropland production and management influence energy consumption and emissions of CO(2) from fossil-fuel combustion. A method was developed to calculate on-site and off-site energy and CO(2) emissions for cropping practices in the United States at the county scale. Energy consumption and emissions occur on-site from the operation of farm machinery and occur off-site from the manufacture and transport of cropland production inputs, such as fertilizers, pesticides, and agricultural lime. Estimates of fossil-fuel consumption and associated CO(2) emissions for cropping practices enable (i) the monitoring of energy and emissions with changes in land management and (ii) the calculation and balancing of regional and national carbon budgets. Results indicate on-site energy use and total energy use (i.e., the sum of on-site and off-site) on U.S. croplands in 2004 ranged from 1.6 to 7.9 GJ ha(-1) yr(-1) and from 5.5 to 20.5 GJ ha(-1) yr(-1), respectively. On-site and total CO(2) emissions in 2004 ranged from 23 to 176 kg C ha(-1) yr(-1) and from 91 to 365 kg C ha(-1) yr(-1), respectively. During the period of this analysis (1990-2004), national total energy consumption for crop production ranged from 1204 to 1297 PJ yr(-1) (Petajoule = 1 x 10(15) Joule) with associated total fossil CO(2) emissions ranging from 21.5 to 23.2 Tg C yr(-1) (Teragram = 1 x 10(12) gram). The annual proportion of on-site CO(2) to total CO(2) emissions changed depending on the diversity of crops planted. Adoption of reduced tillage practices in the United States from 1990 to 2004 resulted in a net fossil emissions reduction of 2.4 Tg C.
农田生产和管理的变化会影响能源消耗以及化石燃料燃烧产生的二氧化碳排放。已开发出一种方法，用于计算美国县级层面作物种植方式的场内和场外能源及二氧化碳排放。能源消耗和排放发生在农场机械作业的场内，以及化肥、农药和农用石灰等农田生产投入品的制造和运输的场外。对作物种植方式的化石燃料消耗及相关二氧化碳排放的估算能够：（i）随着土地管理的变化监测能源和排放；（ii）计算和平衡区域及国家碳预算。结果表明，2004年美国农田的场内能源使用和总能源使用（即场内和场外之和）分别为1.6至7.9吉焦·公顷⁻¹·年⁻¹和5.5至20.5吉焦·公顷⁻¹·年⁻¹。2004年的场内和总二氧化碳排放分别为23至176千克碳·公顷⁻¹·年⁻¹和91至365千克碳·公顷⁻¹·年⁻¹。在该分析期间（1990 - 2004年），全国作物生产的总能源消耗为1204至1297拍焦·年⁻¹（拍焦 = 1×10¹⁵焦耳），相关的化石二氧化碳总排放量为21.5至23.2太克碳·年⁻¹（太克 = 1×10¹²克）。场内二氧化碳占总二氧化碳排放的年比例因种植作物的多样性而有所变化。1990年至2004年美国采用减少耕作方式使化石净排放量减少了2.4太克碳。
