Study On The Concept And Accounting Methods Of Agricultural Productivity On Ecosystem Scale And Their Applications

What is the connotation and the extension of the productivity concept, and how to calibrate it are the core problems in evaluating an agricultural production process. The attributes of agricultural production and its expanding scope have changed greatly in the last 100 years, and the methods to describe and measure the productivity failed to keep up with, resulting in a totally vague, incomplete valuation of the production processes. The serious pollution is usually missed behind shortdated profit, bringing along a blooming and flooding polluting; sometimes the great ecological benefits are ignored and the corresponding production processes are died from "economic deficit". With the old agricultural productivity indices, it can't be told what an agroecosytem is ultimately producing to mankind, pollution or welfare. A new concept, Agricultural Productivity on Ecosystem Scale(APES) and the related indices are defined here to solve these problems. Emergy and exergy are introduced to help the measurement of the indices. APES of an agroecosystem is the aggregated contributions of all components to mankind and its habitat in uniformed dimensions, may be expressed in material, energy, information, organization or pollution, damage etc., positive or negative. The comparative studies suggested that emergy be the memory of energy, not sensitive to quality of inputs, by-products utilities and circular systemes, and fitted to be used to measure the total cost, including natural capital and social capital, not the productivities. And exergy shows maximum utilities and organization, and fitted to be used to measure the productivity.APES are specially used here to distinguish from the concept of Agroecosytem Productivity derived from Ecosystem Productivity. Related Variables to account APES are Agroecological Total Cost(ATC), meaning all the natural and social inputs, counted in emergy methods; Agroecological Gross Output(AGO), meaning total aimed output; Environment Depletion(ED), meaning the consumption in the environment by the producing process; and some other indexes showing the efficiency of the system, eg, Agroecological Output Ration(AOR), Agroecological Coupling Degree(ACD) and Agroecological Organizing Index(AOI). AGO and ED have the same basic attributes, both mean the abilities to affect. They can be calculated with the same method, Exergy Valuation. APES equal to AGO subtract ED. Among the efficiency indices, ACD is the quotient of APES and ATC, marking the abilities to utilize resources, consume environment and to yield, and can be used as a very good indicator to the systemic sustainability; AOR means how much AGO each unit ATC produce; while AOI shows how much ATC one unit APES cost, actually, AOI is the reciprocal of ACD.The formula to calculate the variables above are developed from Emergy Accounting and Exergy Acounting methods, which made it possible to account the complete cost, including natural capital and social capital, the whole output, including all kind of products and services, and the consumption in environment by the producing process in one uniformed dimension. All the concepts and accounting methods are successfully used to analyze a small farm, where two farming system are designed, and agricultural system in Shunyi district, a suburb of Beijing, where fanning system was restructured.