农田土壤有机碳管理与有机质平衡算法

Soil Organic Carbon Management and Farmland Organic Matter Balance Method

现代土壤肥料研究推动全球不同国家和地区建立了主要作物对氮、磷、钾等矿质养分需求量的推荐指标,这些量化指标成为科学施肥的基础,促进了农业实现增产、增收、增效和环境安全。土壤培肥是发展农业的基础。有机肥、绿肥、秸秆还田是培肥土壤的主要措施,尽管已有研究证实,过量施用有机肥料不仅造成人力、物力浪费,还会产生农田养分流失和环境污染。迄今为止,在国际范围,对农田培肥尚无量化推荐指标。近年由德国科学家建立并尝试采用的农田有机质平衡算法及推荐指标将可能打破这一僵局。本文择要介绍这一方法原理、应用范围和示例,以期为我国提供可资借鉴的经验。有机质平衡算法的科学基础是通过多点长期定位试验,获得作物和有机肥料的土壤有机质碳当量值,前者用以度量不同作物在其典型种植方式下,引起土壤有机质碳量变化的趋势,后者用于表征不同有机肥料施入土壤后产生的有机质量。通过有机质碳当量值,可以对作物在典型种植方式下引起土壤有机质的亏缺量或盈余量、秸秆还田或施用有机肥引起土壤有机质的增加量统一在一个量纲基准上进行分析和计算。该方法作为官方推荐方法,自2004年始在德国多个州和奥地利推广采用,既适用于综合农业,也适用于有机农业。在不允许使用矿质氮肥的有机农业上,该法兼作农田氮素养分管理方法。多点大田校验试验显示,采用此方法,农田土壤有机质供应水平从"低"提高至"平衡"等级时,产量增加幅度可达到50%-150%。有机质平衡算法作为专为农民研制的分区、分类、量化技术指标,延续德国为农民定制的其他技术指标风格,采用了五等级评价指标体系架构。五等级的各分级名、分级释义充分汇总各地长期试验和大量农户调查与验证结果,形成了全国统一的等级释义,保证了指标体系架构的稳定性,既便于各地农民记忆和长期推广,也便于与国家绿色农业补贴政策关联,是有机质平衡算法的前台指标。而与5个分级对应的农田有机质碳当量值范围、作物与肥料有机质碳当量作为支持前台指标的专业指标,允许各地农业科研机构根据本地条件,在保证前台指标释义不变前提下进行相应调整,从而保证了整个指标体系的可扩展性、科学性和实用性,促进了其在各地的广泛推广,切实提高了农民科学施肥与耕地保育技术水平,推动了农田精准化、标准化管理和农业面源污染管控效率,这一做法也值得我国借鉴。在中国应用这一方法的关键是研制适合各主要农区作物和有机肥料的有机质碳当量值。鉴于目前我国长期定位试验数量有限,可借鉴德国相关研究基础,采用长期与中、短期定位试验结合,大田定位试验与模拟试验、校验试验及农田定位调查相结合方式,边试验、边研制、边校验改进、边推广,逐步完善。

Progress of soil and fertilizer research work has promoted establishment of scientific recommendation for mineral nutrient requirements of major crops in different regions and counties.These quantitative and precise indicators have become the basis of scientific fertilization and ensured yield,income,and fertilizer efficiency increase and environmental safety.While application of organic manure,green manure and straw returning are the main measures to fertilize soil,studies have showed that excessive organic manure application will result in not only energy and resource waste,but also nutrient release and environmental pollution.Up to now,however,there are still no scientific and quantitative indicators for farmland fertilization in international arena.In recent years,a new method tried in Germany might break the deadlock.The purpose of this paper was to introduce the principle,application scope and examples of the method,so as to provide useful experience for China.The scientific basis of the method is the humus equivalent values(Heq)of crops and organic manures,and materials derived from long-term experiments in different regions.The Heq values of different crops is applied to identify the SOC changes caused by different crops under their typical production conditions.The Heq values of different manures and organic materials is applied to characterize the soil humus producing capacity after these materials applied to farmland.Through Heq value,the deficit or surplus of soil humus caused by crops and the increase of soil humus caused by straw returning or organic manure application can be analyzed and calculated on one unified dimension basis.In many states of Germany and in Austria,the method has been used as officially recommended approach.It was suitable for both integrated farming system and organic farming system.For organic farming system,where mineral nitrogen fertilizers were not allowed to apply,the method could also be used as nitrogen nutrient management approach.A large amount of field tests showed that yield increases arrived to 50%-150%,when SOC management level raised from"low"to"balanced"by using the method.Organic matter balance method,specifically designed for farmers,is a region condition identified,group classified and accurately quantified farming’s management approach.A five-grade evaluation,which was consistent with other methods designed for farmers in Germany,was also adopted in the method.In the five grade evaluation system,name,definitions and interpretation of each grade were nation-wide unified.This was achieved by summarizing a large amount of long-term experiments and farmers surveys from all of the major agricultural areas with different climate,soil and crop production conditions.The unified name and definitions were validated in different regions to ensure the stability of the evaluation indexes.This simplified,unified,and stable evaluation system has showed strong advantages both for learning by farmers and for making relationships between farming’s management measures in practice and subsidy policies for environment.Names,definitions and interpretation of the five grades were the front indexes of the method.The ranges of Heq values in corresponding to the five grades,the Heq values of different crops,manures and organic materials were regarded as the professional indexes or parameters to support the front indexes.These professional parameters were allowed to be adjusted in accordance with local conditions by agricultural research institutions without changing of the unified front indexes.By this way,the method stability,expansibility,scientificity and extensibility in farming’s practice were improved greatly.The architecture composed of front and background indexes designed for farmers for farming’s management is also worthy of our reference.For application of the approach in China,main difficulty is to develop Heq values suitable for crops and agricultural condition in China.Since the sum of qualified long-term experiments in China are limited,we can try to develop the Heq values by use of the available long-term experiments in combination with short-term experiments,simulation experiments as well as site-specific farmland survey in different major agricultural regions in China.To speed up the work,parameter development,calibration,improvement and field demonstration might be done simultaneously.