Abstract:

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.

Key words: SOC management, organic matter balance, nonpoint-source pollution control, organic farming, technique index designed for farmers