Estimation And Evaluation Of Nutrient Flow In The Staple Grain Crop Production-Consumption System In China

Nutrients such as N, P₂O₅ are the important material resources of the plantproduction, which management quality relates directly to the major issue of "thepopulation - resources - environment - grain security" and so on; But the nutrient flowis also the foundation of nutrient management, therefore, it makes us have to considernewly the fate of nutrient flow in crop production - consumption system in China.Taken N, P₂O₅, Fe as the research object, the theory and method of the matterflow and virtual resource flow were adopted in this article in order to study threestaple grain crops production and consumption behavior with nutrient fate frameconstructing, the literature material analysis, the status of nutrient longitudinal flow,nutrient region flow and the virtual resource flow was calculated at national countryscale, as well as the resource efficiency and environment price of nutrient flow wereestimated. The results were as follows:1. The grain crops wheat, rice nutrient efficiency was remarkably higher thanthat of the feed crop corn, the food chain enlarged the nutrient flow distance whichresulted in consuming many nutrients through product transform; While wheatnutrient efficiency was higher than that of rice, indicated the nutrient was largely lostwhen rice entered family. N, P₂O₅ and Fe finally came into family nutrition system,including plant products and animal products such as meat, egg, milk. The percentageof wheat nutrient was 55.2%, 31.7% and 10.5% respectively; the percentage of ricenutrient was 47.3%, 22.3% and 4.8% respectively, that of the corn nutrient wasl 3.0%,7.2% and 2.2% respectively.The nutrient production efficiency was very low in grain processing system,which wheat was slightly higher than that of rice. N edible efficiency of wheat, ricewas not largely different, about 65%, and the edible efficiency of rice P₂O₅ was lower10 percentage points than that of wheat——about 30%, the abundant of nutrient waspreserved in the by-products or lost in the processing, especially rice nutrient lost.2. In 2004, the family consumed one flour N, P₂O₅ were equal to 11.6 of coal,79.5 of phosphorite, resources price of one rice N, P₂O₅ were equal to 14.0 of coal,63.4 of phosphorite, when wheat, rice served as the feed, resources price of animalproduct N, P₂O₅ consumed was higher than that of plant product nutrient; The resources price of corn consumed as the grain were 7.3 of coal, 20.0 of phosphorite,while as the feed the resources price were 56.6 of coal, 407.1 of phosphorite, whichindicated that resources price of the corn served as feed were very high, especiallythat of P2O5. The resources price served as grain: corn＜wheat＜rice.3. The inflow and outflow of the virtual chemical fertilizer nutrient resourcesfollowed as crop nutrient region flow, the nutrient resources flow took on the patternof "the north grain transported the south" and "the south fertilizer moved the north".The output provinces of crop nutrient were with the fertilizer input simultaneously.The amount of international and province virtual chemical fertilizer resources flowwas based on the fertilizer nutrient needed by producing unit crop nutrient, in 2003our country exported the crop nutrient N, P₂O₅ were equal to export 162.5×10⁴ t urea,238.0×10⁴ t single superphosphat, and imported crop nutrient N, P₂O₅ were equal toimport 4.3×10⁴ t urea, 7.3×10⁴ t single superphosphat, therefore the amount of virtualfertilizer nutrient export obviously more than that of the import; The amount that theprovinces of nutrient outflow produced unit crop nutrient needed fertilizer nutrientwas higher than that of the crop nutrient inflow province, so the flow result was quitereasonable in domestic trade.4. The traditional manure was substituted by the chemical fertilizer, the employpercentage of manure nutrient was occupied N 10%, P₂O₅ 20%, and it reducedgradually; The ratio returning straw to the field was quite low, N less than 50%,Swine manure and manure nutrient load per hectare of cropland in the corn inputregion were all high, surpassing the limit standard, while swine manure nutrient cannot be full used in the corn output region and the chemical fertilizer was demanded.The producing level of chemical fertilizer was low, the PFP was low, and the ratioreturning manure nutrient to the field was also low in our country, so these canenlarge the resource and environment price.