| Wheat is one of an important food crop of word, which has great significance in ensuring global food security production. However, recently in order to obtain high and stable yield of wheat, excessive fertilizer input has led to soil nutrient imbalance, fertilizer use efficiency and fertilization effect greatly reduced. Soil testing formula fertilization is an important scientific fertilization technology, has gradually become one of the effective method to solve the above problems. In oreder to explore the abundance and deficiency index of soil nitrogen, phosphorus and potassium for wheat and fertilization recommended, this study summarized the wheat fertilizer effect test results and based on the "3414" experiments in the field for many years and analysised systematically the non-irrigated farmland soil fertility status of wheat and built the soil nutrient index system and fertilization recommendation index of Mianyang city in Sichuan province. The main results were as follows:(1) Wheat soil nutrient in Mianyang city is extremely unbalanced. In order to test field for sampling unit of soil after previous harvest crop and wheat planting basal application before, soil samples (0-20 cm) were collected according to the principle of "S" putting random arrangement. The results showed that soil organic matter (SOM) mailly distributed between 0.90-46.10 g kg-1 with the average contents of 17.18 g kg-1 and coefficient of variation of 72.31%; total nitrogen (TN) mailly distributed between 0.01-2.56 g kg-1 with the average contents of 1.00 g kg-1 and coefficient of variation of 66.73%; available nitrogen (AN) mailly distributed between 36.00-221.00 mg kg-1 with the average contents of 101.09 mg kg-1 and coefficient of variation of 45.79%; available phosphorus (AP) mailly distributed between 0.30-103.00 mg kg-1 with the average contents of 20.51 mg kg-1 and coefficient of variation of 52.35%; available potassium (AK) mailly distributed between27.00-420.00 mg kg-1 with the average contents of 82.11 mg kg-1 and coefficient of variation of 60.17% of study, respectively. Comparing to the soil nutrient content classification standards from the second national soil survey of Sichuan, the contents of soil organic matter and available potassium were reduced, while total nitrogen, available nitrogen and available phosphorus had risen in different degrees, which may be mainly caused by excessive fertilizer application. Therefore, the original fertilizer recommendation system is not suitable for the current level of production.(2) The combination of N, P and K fertilizers significantly increased wheat yield. Researches were carried out based on the most widely used "3414" experiments with three factors of nitrogen, phosphorus and potassium and each factor 4 levels, a total of 14 treatments were carried out to study the optimal fertilizer effect of processing field experiment. The results showed that the wheat yield of N2P2K2 were increased by 60.7%,24.2% and 14.4% compared with no N (N0P2K2), P (N2P0K2) and K (N2P2K0) fertilization treatments, respectively. It was also concluded that combination of N, P and K fertilizers significantly increased the fertilizer use efficiency.(3) This paper successfully built the wheat soil nutrient abundance index system of Mianyang city. Taking plentiful-lack of soil nutrition as an index, TN, AP and AK were classified by wheat relative yield of 55%,65%,75%,85% and 90%. The contents of TN, AP and AK of wheat soil in Mianyang city could be divided into lower (TN<0.5 g kg-1, AP<5 mg kg-1, AK<15 mg kg-1), low(TN 0.5-1.0 g kg-1, AP 5-15 mg kg-1, AK 15-40 mg kg-1), medium (TN 1.0-2.0 g kg-1, AP 15-30 mg kg-1, AK 40-70 mg kg-1), high TN 2.0-2.5 g kg-1, AP 30-50 mg kg-1, AK 70-90 mg kg-1), higher (TN 2.5-3.0 g kg-1, AP 50-60 mg kg-1, AK 90-100 mg kg-1) and the highest (TN>3.0 g kg-1, AP>60 mg kg-1, AK>100 mg kg-1) 6 grade level. Compared with the original index system, TN and AP contents slightly increased, while AK contents significantly reduced.(4) According to the fertilizer response function model to establish recommended nitrogen, phosphorus and potassium fertilizer rate under different soil fertility level. Nitrogen fertilizer rates (N) are 140-190,110-140,80-110,70-80,60-70,0-60 kg hm-2 when soil fertilizer is classified by lower, low, medium, high, higher and the highest, respectively, phosphorus fertilizer rates (P2O5) are 100-110,80-100,60-80, 40-60,30-40,0-30 kg hm-2,while potassium fertilizer rates (K2O) are 90-110,55-90, 35-55,25-35,20-25 and 0-20 kg hm-2. |
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