Abstract: An agroecosystem is a grey box. In the last two years we tried to regulate the inputs of the grey system by the method of related degree analysis and obtained sound results. Related degree analysis has been applied to the regulation of chemical fertilizers (especially nitrogen fertilizer), manure and crop residues inputs to the farmland ecosystem. The results show that related degree analysis can be regarded as a supplementary means in the analysis of energy and material flows. Related order analysis and association coefficient analysis can also be applied to the regulation of input structure and input technique (the choice of time, space, grades and forms). The application program of related degree analysis and nomenclatures like "contribution curve" and "potentiality curve" are introduced.

Key words: Related degree analysis, Related order, Association coefficient, Agro-ecosystem, Technical regulation