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In this study, the input and output parameters of potassium (K) for wheat season were collected from 2000 to 2011 to evaluate the nutrient cycling and balance in North Central China, the Middle and Lower Reaches of the Yangtze River and Northwest China. The results showed that the K fertilizer application rates for each region were 74.7, 102.9 and 50.6 kg K/ha, the K brought from previous crop were 99.5, 19.8 and 23.4 kg K/ha, and brought from seeding were 1.0, 0.8 and 0.7 kg K/ha, respectively. The K input from atmospheric deposition and irrigation were all considered zero. The K uptake by harvest in above-ground plant in North Central China, the Middle and Lower Reaches of the Yangtze River and Northwest China were 131.8, 159.9 and 119.8 kg K/ha. As a result, The K balance in North Central China showed surplus by 43.6 kg/ha, while in the Middle and Lower Reaches of the Yangtze River and Northwest China, the K balance were both deficiency by 36.4 and 45.1 kg/ha, even though it did not affect the crop yield. While it is suggested that we need to adjust the K fertilizer application in a long term, in order to maintain the sustainable soil fertility.

In this study, the input and output parameters of Phosphorus (P) for wheat production system were collected from the year 2000 to 2011 to evaluate the nutrient cycling and balances in North Central China, the Middle and Lower Reaches of the Yangtze River and Northwest China. The results showed that the P fertilizer application rates for each region were 44.5, 39.7 and 42.3 kg P/ha, the P brought from previous crop were 14.8, 1.6 and 2.6 kg/ha, and brought from seeding were 1.5, 1.0 and 0.9 kg/ha, respectively. The P input from atmospheric deposition and irrigation were considered zero. The P uptake by harvest in above-ground plant in North Central China, the Middle and Lower Reaches of the Yangtze River and Northwest China were 41.2, 53.2 and 17.0 kg/ha. As a result, the P balance in North Central China and Northwest China were both showing surplus by 19.6 and 28.8 kg/ha, and in the Middle and Lower Reaches of the Yangtze River showed deficiency. It is suggested that we need to adjust the P fertilizer input in China, in order to maintain the sustainable soil fertility and avoid the negative impact on the environment.

The platform of rural distance learning (PRDL) is an interactive tool used to farmers for the video training, interactive consulting, teaching and management with the features of resource integration, safe, and reliable. PRDL was dual-network transmission structure via the Internet and E-government network, covering all the Beijings towns and villages, which is applied media asset management technology to build a municipal teaching resource library. The problems of PRDL are solved such as complex network for rural areas, limited bandwidth resources and diverse user needs base on in-depth study of distance learning key technologies. It is for farmers learning modern agricultural technology to provide a strong support.