Calculating fertilizer demand of rice plants by technique

The technique of 'defect umbrella' helps determine the role of plurality of elements (nitrogen, phosphorus and potassium) on rice fields, thereby helping farmers calculate the amount of fertilizer needed for each rice variety. each season, each field.

Fertilizer plays a very important role in cultivation, helps plants grow well, increases productivity and quality of agricultural products . However, how to use fertilizer effectively, many farmers still not caught. In this article, we introduce a technique to help determine the fertilizer needs for rice.

In order to use fertilizer effectively, especially in rice production, for many years, the agricultural sector has regularly advised farmers to use fertilizers on the '4-true' principle: right kind, right dosage, right way and right time . However, in the opinion of many scientists, in the above '4 correct', applying fertilizer to the right dose is not easy.

Therefore, to help farmers determine the correct amount of fertilizer to fertilize rice, the Mekong Delta Rice Institute introduced the technique of 'defect'. This technique is based on research on fertilization according to the needs of rice, conducted by the International Rice Research Institute (IRRI). The technique of 'defect umbrella' helps determine the role of plurality of elements (nitrogen, phosphorus and potassium) on rice fields, thereby helping farmers calculate the amount of fertilizer needed for each rice variety. each season, each field. People follow 4 steps as follows:

The technique of 'defect umbrella' helps determine the role of plurality of elements (nitrogen, phosphorus and potassium) on rice.

1. Determine target productivity

To determine the target productivity, statistics must be made and the average productivity of the three consecutive years must be calculated. The target productivity should be about 0.5 ton / ha higher than the average yield, but there must be a realistic basis, not offering too high or too low productivity levels.

2. Determine nutritional needs

In order to get enough nutrients, rice plants will have to absorb nutrients in the soil and fertilizer. IRRI's research shows that, to produce 1 ton of rice, rice must absorb and accumulate 15kg N, 6 kg P2O5, 18kg K2O. Thus, if the target yield is 7 tons / ha, per hectare, rice needs 105kg N, 42kg P2O5 and 126kg K2O.

3. Determine nutrient content from soil

Rice takes nutrients from soil and fertilizer. Therefore, to calculate the amount of fertilizer needed, the nutrient content of the soil must be determined. To determine the amount of nutrients in the soil, in the field, farmers build the banks into 3 adjacent small plots, each with size 5X5 m. In order not to distort the results, all 3 plots are always full of water, without pests and diseases, and weed attack. In turn, each cell corresponds to one of the three major elements that are missing (the cell does not apply nitrogen, the other cell does not apply phosphorus, the other cell does not apply potassium), the other two plurality elements are still full.

When harvesting rice in each plot, it is necessary to record the actual yield to calculate the amount of nitrogen, phosphorus and potassium that rice plants take from soil and other sources such as agricultural byproducts, silt, microorganisms . If in the field without nitrogen fertilizer, rice yield reaches 4.2 tons / ha, the amount of nitrogen that rice from soil is 4.2 (tons) X 15 (kg) = 63kg N / ha; if in the unfertilized plot, yield reaches 5.5 tons / ha, the amount of phosphorus that the rice from the soil is 5.5 (ton) X 6 (kg) = 33kg P2O5 / ha; If there is no potassium fertilizer in the plot, the yield reaches 6 tons / ha, the amount of potassium from the soil is 6 (tons) X 18 (kg) = 108kg K2O / ha. Thus, the demand for fertilizer for the target yield of 7 tons / ha will be: 42 kg N / ha (taking 105kg minus 63kg), 9kg P2O5 / ha (42kg P2O5 minus 33kg) and 18kg K2O / ha ( 126kg K2O minus 108kg).

4. Determine the amount of fertilizer to use

To determine the amount of fertilizer to use, we use the formula FR = Nt - Nđ / Re (FR is the amount of fertilizer to be applied; Nt is the total amount of nutrients needed; Nđ is the nutrient supply from the soil; Re is the effect fruit use of fruits).Note : The Re index depends on crop varieties, soil, season and farming techniques; usually with index nitrogen Re = 40–60%, with phosphorus Re = 20–30%, with potassium Re = 40–50%. Nt and Nđ are determined in steps 2 and 3 above. After that, design fertilizer process for each rice variety group, each region, each season . different.

Through the research results and the above calculation, in the winter-spring crop, farmers need to apply about 100–110kg / ha of nitrogen fertilizer, the summer-autumn crop is about 70–90 kg / ha. Phosphate amount is about 30–60kg / ha, potassium fertilizer 30–40kg / ha. It is possible to increase each crop by 10 kg of potassium to maintain stable potassium content in the soil.