2 Fertility subtraction method to calculate the amount of fertilizer applied

2.1 Determine the target yield

The target output, the planned output, is determined based on the level of soil fertility. Usually can be found by empirical formula: y = a + bx. In the formula: y - target production: x - no fertilizer production. First, under a variety of fertility conditions, through a multi-point test, a large number of pairs of the most economic output (target production) and no fertilizer area yield, obtained coefficient a, b, establish the equation. Knowing the yield x of the fertilizer-free zone of a certain field, the target yield y can be obtained from y=a+bx. The target yield can also be determined by using the average output under the normal climate and cultivation conditions in the first three years as the base, and then increasing it by 10% to 15%.

2.2 Determine the Fertility-free Production Area

Fertilizer-free production, also known as basic yield, can be obtained from field trials. Some common crops can also be obtained from farmers.

2.3 Calculate crop yield per unit nutrient uptake

Crop yield per unit of nutrient absorption refers to the amount of nutrients absorbed per target unit of production (eg, 100kg), mainly nitrogen, phosphorus, and potassium, and is generally stable (refer to relevant publications, manuals). As long as the planned unit area yield of a crop is multiplied by the nutrient amount of nitrogen, phosphorus, and potassium needed to produce 100 kg of crop, the amount of nitrogen, phosphorus, and potassium absorbed by the crop's planned production can be calculated.

2.4 fertilizer utilization rate in the season

Soil fertility utilization is more difficult to determine, the exact method is to conduct field trials, and then calculated according to the formula. Fertilizer utilization refers to the ratio of crop uptake to fertilizer input, and the formula is: the utilization rate of an element in the current season = (the total amount of the element absorbed by the fertilizer in the fertilized area - the total amount of the element absorbed by the crop in the non-fertilized area) x 100% Fertilizer contains the total amount of this element. In rough calculations, fertilizer utilization can also be determined by consulting relevant data. The use of the same fertilizer in different crops varies. Fertilizer nutrient content can refer to the relevant literature.

3 Soil nutrient effective correction coefficient method to calculate the amount of fertilizer application

When using soil nutrient effective correction coefficient method fertilization formula to calculate the amount of fertilizer, it is necessary to determine the soil effective nutrient correction coefficient, target production needs of total nutrients, fertilizer utilization and other parameters. The last two parameters are the same as the subtraction method. Only the soil effective nutrient correction coefficient should be studied. Soil nutrient correction factor = no fertilizer area yield × crop unit yield nutrient absorption amount / (measured value of soil nutrients × 0.15). In the formula, 0.15 is the conversion factor expressed in units of kg/mu converted from the unit of nutrients contained in the plough layer soil (0 to 20 cm topsoil) in units of mg/kg. The soil nutrient correction coefficient varies with the soil content and the type of crop. For a certain fixed crop in a specific region (such as a county or town), the nutrient correction coefficient varies with the soil nutrient content. The law of change. In the case of determining the crop type, the nutrient content of the soil generally increases, and the nutrient correction coefficient decreases.

The advantages of the subtraction of fertility difference method and formula fertilization is that the fertilization formula can be determined according to the basic yield of the ground force, and it is suitable for users who do not have soil testing conditions to facilitate the promotion. The nutrient correction coefficient method has a wide adaptability and the scope of application is not limited. Therefore, the nutrient correction coefficient method is often used for the theoretical basis for recommending formula decision support.

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