The economic benefits of using untreated and treated crop residues as feed for ruminants mainly depends on the source and cost of crop residues, cost of treatment, cost of urea or other ammonia source, on the price of protein supplements, as well as on agricultural production and technical levels and other factors. In relation to the potential of crop residue use, countries can be divided into four types:
Type 1 are developing countries and regions with a high population density. Most countries in the Far East and part of the Middle East belong to this group. Crop residues in general are used as the major feed for ruminants. Treated crop residues may result in very good economic returns.
Type 2 are developing countries and regions with low population density. Most countries and regions in Africa and Latin America where land use is not restricted belong to this type. Feed supply comes from various sources, but cattle production relies, in general, on natural pastures. Crop residues, treated or untreated in emergency situations, especially in the dry season, become an important feed resource.
Type 3 are developed countries and regions with an ample grain supply. The USA, Canada and France belong to this type. In addition to roughage, ruminants are fed with large quantities of concentrates to obtain high yields of animal products. Untreated crop residues are sometimes used as a source of fibre substituting hay or silage. Under these conditions, treated crop residues might give fairly good economic benefits. However, it might not be economical to utilize crop residues in areas where the production of hay or silage is high.
Type 4 are the developed countries and regions with small land area per capita. Most countries in north Europe belong to this type. In order to achieve self-sufficiency in food, the governments of these countries attach great importance to the utilization of crop residues so as to increase food output from the limited land. Among north European countries, Denmark and Norway use the highest proportion of crop residues as feed.
In China, the broad agricultural region, characterized by huge population with limited land, belongs to Type 2. It has good prospects for developing animal husbandry based on crop residues.
Status of the utilization of crop residues in China
In general, straw is used for burning, composting, paper making and animal husbandry. For a long period in the past, due to limited economic development and way of life, it was very popular to use straw as fuel for cooking. It is estimated that 70 percent of total straw was used as fuel. With the improvement in the rural economy and farmers' living standards, rural energy has become diversified to coal, natural gas, biogas, electricity, etc., so the amount of straw used as fuel has been reduced to less than 50 percent. Direct straw application to soils is also practised, but this operation increases the cost by about ¥ 10 per mu (¥ 150/ha). At the same time, it takes time for straw to fully decompose, thus interfering with germination and growth of the next crop. This is particularly true in regions with intensive agriculture because it increases the difficulties for crop rotation. In addition, returning straws directly to the field may have hidden dangers in terms of insects and diseases, so this utilization has its limitations. Returning straw to fields wastes the energy, decomposed by micro-organisms, while crops can only utilize part of the N, P, K and other inorganic nutrients after decomposition.
Another use for straw is as raw material for paper making. It is estimated that 2-2.5 tonne of rice straw can be processed into 1 tonne of paper. However, it is difficult to collect due to the large volumes involved and its disperse distribution, and only part of the rice straw can be utilized. Since 1995, the State has shut down many medium- and small-sized local paper plants due to environmental pollution. The...