Improving the efficiency of fertilizer use for spring rice crops.

(Baonghean) - Summarizing the role of fertilizers in rice production, our ancestors have long concluded, "With fertilizer, rice is like a plant with wealth."

Today, scientists have proven the crucial role of fertilizers in intensive crop cultivation in general and rice cultivation in particular. For rice, fertilizers contribute to a 40% increase in yield. Seed quality increases it by 30%, plant protection by 20%, and mechanization by 10%. Thus, fertilizers are the most important factor in intensive cultivation and increasing rice yield. They also account for a high percentage of rice production costs. Farmers also need to understand that the amount of fertilizer absorbed by rice plants is very low, or in other words, the efficiency of fertilizers is not as high as farmers expect. According to data from Professor, Dr. Nguyen Van Bo, Director of the Vietnam Academy of Agricultural Sciences, the efficiency of fertilizer use in our country is very low: nitrogen fertilizers are only 45-50%, phosphorus fertilizers 25-35%, and potassium 60%.

In Nghe An, fertilizer efficiency is even lower. Results from the "Balanced Fertilization for Rice" program, a collaboration between the Asia Pacific Institute of Phosphorus and Potassium and the Nghe An Agricultural Extension Center from 1995-2001, showed that fertilizer application to rice, sesame, and corn on various soil types in Nghe An contributed to a 35-42% increase in rice yield; however, fertilizer efficiency for rice only reached 35-40% for nitrogen fertilizer, 20-25% for phosphorus fertilizer, and 50-55% for potassium fertilizer.

In our opinion, the reason for this difference is the harsh weather in Nghe An. The winter-spring crop often experiences severe cold, affecting the absorption of nutrients by rice plants, especially nitrogen fertilizer. The summer-autumn crop is hot and sunny, with southwest monsoon winds, sometimes reaching outdoor temperatures of 39-40°C. In some places like Quy Chau and Tuong Duong, temperatures even reach 40-41°C. This causes fertilizer to evaporate quickly.

To improve fertilizer efficiency, we would like to share some information with farmers on "Balanced and Rational Fertilization" for spring rice crops as follows: First, farmers need to understand the effects of some key fertilizers in intensive rice cultivation.

Organic fertilizer:

There are two types of natural organic fertilizers: cow and buffalo manure, and microbial organic fertilizers, which are processed through the fermentation of organic products. Both types primarily provide the soil with organic matter, contributing to increased soil fertility. They also supply several other essential macro and micronutrients necessary for rice plant growth and development.

Inorganic fertilizers:

Nitrogen fertilizers: There are many types of nitrogen fertilizers, such as: Urea - CO(NH2), Sulfatammonium (NH4SO4), Nitrataminophen (NH4NO3).

Phosphate fertilizers: Natural phosphate fertilizers such as apatite and phosphorite are difficult to dissolve. Processed phosphate fertilizers include superphosphate and fused phosphate. Remember that phosphate is mainly obtained from nature.

Potassium fertilizers: Primarily formed naturally. There are two types of potassium fertilizers commonly used in agriculture: potassium sulfate (K2SO4) and potassium chloride (KCl).

Complex fertilizer: DAP (NH4)2HPO4, with a phosphorus content of 45% phosphorus and 16% nitrogen.

Mixed NPK fertilizers: These have varying NPK ratios. Currently, there are specialized NPK fertilizers for different types of crops.

Regarding the nitrogen, phosphorus, and potassium requirements of rice plants: To produce 10 tons of paddy and 8 tons of straw, rice plants extract approximately 218 kg of nitrogen, 31 kg of phosphorus, and 258 kg of pure potassium from the soil, equivalent to 474 kg of urea, 180 kg of superphosphate, and 516 kg of potassium. The stage when rice plants need the most nitrogen is during tillering and panicle differentiation. Insufficient nitrogen supply will result in stunted growth, slow development, and leaves that are pale green to yellow from the tip. Severe deficiency leads to low yield, low protein content, and poor rice quality. Adequate phosphorus fertilization increases nitrogen absorption, promotes strong root development, concentrated tillering, cold tolerance, abundant flowering, high pollination rates, good pest and disease resistance, high yield, and good rice quality. Phosphorus deficiency results in poor root development, many leaves and stems with purplish spots, slender stems, and small, dark green leaves.

Potassium promotes photosynthesis and increases the rice plant's ability to absorb nitrogen. Adequate potassium fertilization helps rice plants become stronger, more resistant to lodging, more tolerant to cold, more resistant to pests and diseases, and increases the percentage of plump grains, resulting in higher yield and quality. Potassium deficiency causes yellowing of the leaves along the leaf margins, a high percentage of empty grains, and brittle rice. Rice plants require potassium during the flower bud differentiation stage.

Regarding the appropriate ratio for rice cultivation: The ratio of nitrogen to potassium fertilizer for rice is 1:1. When researching this issue, most farmers do not pay attention to the ratio of different fertilizers when applying them. Mr. Pham Lac from Hamlet 2, Hung Khanh Commune, Hung Nguyen District, said that his fertilizer investment for one sao (approximately 1000 square meters) is as follows: 25kg NPK-8:10:3, 7kg urea, and 3kg potassium. If following these amounts, the NPK ratio is only 1:0.5:0.4. In our opinion, for hybrid rice, the amount of potassium should be increased to achieve an NPK ratio of approximately 1:0.6:0.8, which is more suitable.

Engineer: Phan Bui Tan

(Contributor)