Dynamics of Soil Organic Matter in Tropical Ecosystems
Dynamics of Soil Organic Matter in Tropical Ecosystems
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DOI：
10.5860/choice.27-5759
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发表时间：
1989-12
期刊：
影响因子：
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通讯作者：
D. Coleman;J. Oades;G. Uehara
中科院分区：
文献类型：
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作者：
D. Coleman;J. Oades;G. Uehara
对土壤的有机输入必须与土壤有机质(SOM)分开考虑，以正确理解热带农业生态系统可持续发展所涉及的物理、化学和生物过程。目前对有机投入的管理在很大程度上是经验的和定性的。需要更好地了解有机投入在凋落物分解、养分循环和土壤聚集过程中所起的作用。有机投入的管理应与化肥和石灰等无机投入的管理一样可预测。有机投入的应用应促进养分释放与植物生长需求的同步性。需要预测性参数来接近同步。有机投入分解研究应在不同的农业生态系统中进行。人们对根凋落物在热带农业生态系统中的作用知之甚少。确定了热带农业生态系统的六项研究任务：(1)量化地上有机投入的生物量和养分含量；(2)建立有机投入养分释放模式或质量的预测参数；(3)调查有机投入对热带农业生态系统养分有机投入管理的影响125有效性；(4)量化根的生产和养分释放，确定描述根系分解的资源质量参数，并确定根作为养分来源的相对重要性：(5)调查有机投入的质量和放置对土壤物理性质的影响；以及(6)了解在不同质地、矿物学以及水分和温度状况的土壤中，有机输入如何转化为功能性的SOM池。我们需要可靠的田间方法来测量根的产生和分解，将有机输入转化为土壤有机质组分，并在土壤有机质池之间转移过程。热带物种和耕作系统的多样性为改善热带农业生态系统提供了充足的作物和有机投入组合。农业生态系统与自然生态系统的不同之处在于，大量的生物质和营养物质作为农作物被去除。作物收获产生的养分输出远远超过其他养分流失途径的总和。表1显示了这一点，其中提供了温带地区国家年度作物养分收支研究的摘要。健康农业的一个长期原则是通过添加无机肥料或有机肥料来补充作物收获时失去的营养物质。除了增加养分外，有机添加剂还可以改善土壤物理性质，帮助保持土壤有机质含量，所有这些都会对植物生产力产生积极影响(Allison，1973)。对土壤的有机输入包括地上和地下凋落物、作物残留物、覆盖物、绿肥、动物粪便和污水。其中一些投入是在“表1.来自美国、英国、荷兰、法国、以色列和日本的18个作物生产系统的养分投入和产出摘要(Kg Hayr)”网站上种植和回收的。(根据Frissel，1978年的数据计算的平均值和标准差。)养分输入或输出氮磷钾输入无机肥156 t 189 39“t38 119=188固定19±：39其他13±：13 0.4 t 0.8 9 13总计188±75 39”t39 127 t 176输出-脱氮103 t 86 16±16 91±t13反硝化20 224a淋洗38b和总计127±：95 16=6.91±13平衡60“93 24±30 37=77 a。B.报告淋滤的18个数据集中的3个的平均值。ND=未确定。126热带生态系统中土壤有机质的动态(系统内部)，而其他的则来自其他地点，如清华，构成了养分和有机碳的主要来源。有机输入不同于土壤有机质(SONM)，后者可以被定义为在土壤中经历了部分或完全转化的、位于土壤表层以下的生物有机质。在许多文献中，有机：‘Puts和SOM被归类为“有机质”，创造了相当大的融合%4h，与草皮有机质相比，有机：Puts的作用很容易被评估和管理。因此，我们建议不鼓励使用有机物质一词，而鼓励使用有机投入物和有机物质(有机物质)。虽然早期的稻作严重依赖于有机投入，但随着无机肥料的丰富和经济实用，重点转向了无机肥料。今天，由于大部分热带地区的农业发展在很大程度上受到经济限制，因此必须再次强调使用有机投入以及L化肥。本文简要回顾了图1。概念模型cf-ra、cr-ccls和土壤有机质的迁移。数字表明了研究的重点(见正文结论)。
Organic inputs to the soil must be considered separate from soil organic matter (SOM) to understand properly the physical, chemical, and biologi cal processes involved in the sustainability of tropical agroecosystems. Present management of organic inputs is largely empirical and qualita tive. A better understanding of the role ot organic inputs on the processes involved in litter decomposition, nutrient cycling, and soil aggregation is needed. The management of organic inputs should be as predictable as that of inorganic inputs, such as fertilizers and lime. The application of or ganic inputs should promote the synchrony of nutrient release w;th plant growth demands. Predictive parameters are needed to approach synchrony. Research on decomposition of organic inputs should be con ducted in various agroecosystems. Very little is known about the role of root litter in tropical agroecosystems. Six research imperatives are iden tified for tropical agroecosystems: (1)quantify the biomass and nutrient content of aboveground organic inputs: (2)develop predictive parameters for nutrient release patterns, or quality, of organic inputs; (3) investigate the effect of piacement of organic inputs on nutrient Organic Input Management in Tropical Agroecosystems 125 availability; (4) quantify production and nutrient releaie by roots, identify resource quality parameters (see Chapter 4) that describe root decom position, and determine the relative importance of roots as sources of nutrients: (5) investigate the effects of quality and placement of organic in puts on soil physical properties; and (6) understand how organic inputs are transformed into functional SOM pools in soils differing in texture, mineralogy, and moisture and temperature regimes. We need reliable field methods ior measuring root production and decomposition, transfer from organic inputs into SOM fractions, and transfer processes among SOM pools. The diversity of tropical species and farming systems provides ample combinations of crops and organic inputs for improving tropical agroecosystems. Agroecosystems differ from natural ecosystems in that large amounts of biomass and nutrients are removed as crops. Nutrient outputs via crop harvests far exceed the other nutrient loss pathways combined. This is shown in Table 1 where asummary of annual crop nutrient budget studies from temperate-region countries is presented. A long-standing principle of sound agriculture is to replace the nutrienis lost via crop harvests by adding either inorganic or organic fertilizers. Aside from adding nutrients, organic additions improve soil physical properties and help maintain soil organic matter content, all of which positively affect plant productivity (Allison, 1973). Organic inputs to the soil consist of aboveand belowground litter, crop residues, mulches, green manures, animal manures, and sewage. Some of these inputs are grown and recycled on site " Tablo 1. Summary of nutrient inputs and outputs (kg hayr") of 18 crop production systems from the United Statos, United Kingdom, Netherlands, France, Israel, and Japan. (Mean and standard deviations calculated from data of Frissel, 1978.) Nutrient inouts or outouts Nitrogen Phosohorus Potassium Inputs Inorganic fertilizer 156 t 189 39 "t38 119 = 188 Nfixation 19 ±: 39 Other 13 ±: 13 0.4 t 0.8 9 13 Total 188 ± 75 39 "t39 127 t 176 Outputs -arvest removal 103 t 86 16 ±16 91 ±t 13 Denitrification 20 224a Leacflng 38b nd nd Total 127 ±: 95 16 = 6 91 ± 13 Balance 60 "93 24 ±30 37 = 77 a. Mean of 10 out ot 18 data sets reportir,j denitrification. b. Mean of 3 out of 18 data sets reporting leaching. nd = not determined. 126 Dynamics of SOM in Tropical Ecosystems (internal to the system), while others are brought in from other sites, thu, constituting an cetrnal source of nutrients and orezanic C. Organic inputs are distinct from soil organic matter (SONM), which can be defincd as organic material of biological oricin that has undergone partial or complete transformation in the soil and is located below the soil surface. In much of the literature, organi.: 'puts and SOM arc lumped together as "organic matter," creating considerable con-fusion %4hcnattempting to evaluate and manage the role of organic :nputs c mpared to that of sod organic matter. We proposc, therefore, to discourai'c using the term organicmatterand encourage the use of organic inputs and soti ,rgantc matter ISOM). Although early acriculturc depcnded heavily on organic inputs, the emphasis shiftcd to inorganic fertilizcrs as they became abundant and economi cally practical. Today, because agricultural development in much of the tropics is largely limited by economic constraints, emphasis must again be placed on use of organic inputs along 'ith chcmic:;l fertilizers. This paper briefly reviews Figure 1. Conceptual model cf ra;cr -ccls and transfers of soil organic matter. Numbers indicate focus of research 'mperatives (see text conclusions).