| There are rich water and enough solar-thermal resource in Inner Mongolia Hetao irrigation. It is the important base of grain production in the Inner mongolia or even in the countrywide, and the wheat and the corn are the main crops. However, the parameters guiding the local fertilizer was created during the second soil survey, and the original fertilization index can not guide the current agricultural production. In order to improve the current situation, through collecting peasant households survey data, sampling analysis data and field experiment data, many research including irrigation's fertilization status, soil nutrient status and change, fertilization effect, wheat and corn fertilizing index were proceed during 2006~2008.1. There are 45846 households that were surveyed in Hetao irrigation area. The results showed that 28.1 percent of households area applied organic manure with average amount of 26205 kg/hm2, and 82.5% of households used in 15000～30000 kg/hm2. 97.3% of households applied N fertilizer with average amount of 250.2 kg/hm2, and 58.5% of households in 150.0～300.0 kg/hm2. 88.9% of households applied P fertilizer with average amount of 130.5 kg/hm2 P2O5, and 44.4 % households were in 75.0～150.0 kg/hm2. 10.6% of households applied K fertilizer with average amount of 33kg/hm2. Organic fertilizer and K fertilizer application rate were lower, and N and P fertilizer application rate was higher with a great varied rate of N, P.2. Soil nutrition condition and variation were discussed by survey on soil nutrition of cropland in Hetao irrigation area. The results showed that average soil Organic manure content of cropland was 14.8 g/kg, and 62.8% of cropland with Organic manure content was in 12.1-24.4 g/kg. The average total N content was 0.86 g/kg, 52.5% of cropland with total N content in 0.75-1.27 g/kg. Average available P content was 12.9 mg/kg, and 67.5% of cropland with available P was in 9.3-36.2mg/kg. Available K content was 166mg/kg, and 68.1% of cropland with available P content was in 101-200mg/kg. Organic manure, total N and available P of irrigated soil and meadow soils increased in different degree, but, Available K reduced compared to the date of soil survey in 1982 in Hetao irrigated area.3. Agronomy efficiency of N, P2O5 and K2O in wheat in Hetao irrigation area was 6.4, 6.0 and 5.4 kg/kg respectively. Contribution of N, P2O5 and K2O to wheat yield was mean of 33.5 %, 18.4% and 8.0% respectively, Contribution of fertilizer was 36.5%, and contribution of soil was 63.5%. Agronomy efficiency of N, P2O5 and K2O in corn in Hetao irrigation area was 10.6, 9.9 and 6.7 kg/kg respectively. Contrbution of N, P2O5 and K2O to corn yield was 27.2 %, 15.0 % and 4.4% respectively, Contribution of fertilizer was 38.5%, and contribution of soil was 61.5%. Yield response by fertilizer application increased with the declining of soil fertility, while decreased with agronomic efficiency.4. Fertilizer N, P and K recommendation models for wheat in Hetao irrigated area were established according to the relationship of optimal application of N, P2O5 , K2O and soil nutrients.Estimated by the distribute frequencies of rate of fertilizers, amount of households with rates of N, P2O5 and K2O applied beyond the range of rate of fertilizers recommendation accounted for 45.8%, 78.3% and 97.1% of total households surveyed about wheat, and 82.1%, 75.8%, 98.7% about corn respectively. From ratio of input and output of nutrients, surplus of N and P2O5 in soil for wheat were 87 and 58.5 kg per hectare, respectively. But deficit of K2O in soil was 165 kg per hectare. In wheat, corresponding values for corn were 87, 58.5 and 153 kg per hectare, respectively. Compared with conventional fertilization, rate of N and P with fertilizer recommendation were decreased by 33.6 and 16.3 % in wheat and 32.9 and 1.79% in corn, respectively, while rate of K for both crops was increased. The application rates of fertilizers recommendation were validated through experiments of wheat and corn. Some results showed that application of recommendation fertilizers can increase crop yields, income and improve the utilization rate of fertilizer.In summary, through the soil nutrients and fertilization effects, combined with the status of recommended fertilizer, NPK fertilizer was determined to the reasonable amount that will be helpful to increasing crop yields, reducing fertilizer waste, and increasing the income. Determining the recommended amount of fertilizer in wheat and corn has high application value in Hetao irrigation area.
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