Detailed Explanation of Key Technical Points for Soil Testing and Formulated Fertilization in Rice

I. Fertilization Principles

1. Soil testing and formulated fertilization for rice should follow the principles of determining yield target based on soil, determining fertilizer rate based on yield target, supplementing deficient nutrients, combining organic and inorganic fertilizers, and balanced application of nitrogen, phosphorus and potassium.

First, soil testing is required. Soil testing is the prerequisite for soil testing and formulated fertilization; through analysis and determination of soil nutrients, the soil nutrient status and fertilizer supply capacity can be accurately grasped, providing a scientific basis for formulated fertilization. Second, a good formula must be prepared. The formula is the key to fertilization. On the basis of soil testing, according to soil characteristics, cultivation practices, crop nutrient requirements, production level and climate conditions, combined with the previous year's yield level, the target yield is determined, and then according to the fertilizer effect, the optimal application rates and best ratios of nitrogen, phosphorus and potassium are proposed. Third, fertilizer preparation (fertilizer supply). According to the formula requirements, select high-quality single-element fertilizers or special-purpose fertilizers, compound fertilizers, organic-inorganic compound fertilizers and other fertilizer varieties for scientific combination. Fourth, fertilization model. According to soil type, crop growth characteristics and nutrient requirements, formulate the corresponding fertilization model.

The fertilizer requirement of rice is that every 100 kg of rice grain requires absorption of 2.0-2.4 kg of nitrogen, 0.9-1.4 kg of phosphorus pentoxide, and 2.5-2.9 kg of potassium oxide. Taking into comprehensive consideration factors such as soil supply capacity, fertilizer use efficiency and production level, under medium soil nutrient conditions, the ratio of nitrogen, phosphorus and potassium in the applied fertilizer should be about 1:0.5:0.9.

2. Apply sufficient basal fertilizer. Basal fertilizer should be mainly organic fertilizer, supplemented by chemical fertilizer. Organic fertilizer is a complete fertilizer containing various nutrients; in addition to nitrogen, phosphorus and potassium, it also contains sodium, magnesium, sulfur, calcium and various trace elements. Applying organic fertilizer can improve soil aeration, enhance fertilizer and water retention capacity, and promote steady growth of rice plants, thereby helping rice achieve high yield and good quality. Farmyard manure must be selected from thoroughly decomposed farmyard manure.

3. Control nitrogen fertilizer. Appropriate application of nitrogen fertilizer to rice can promote tillering and growth of rice plants, but excessive application will not only cause an increase in ineffective tillers, greening, lodging and aggravation of pests and diseases, but also lead to more empty and shriveled grains, a decrease in seed-setting rate, and affect rice yield. Therefore, during the growth and development of rice, attention should be paid to controlling the amount of nitrogen fertilizer.

4. Attach importance to applying phosphorus and potassium fertilizers. Phosphorus and potassium fertilizers are indispensable elements for the growth and development of rice. They can enhance the internal activity of plants, promote nutrient synthesis and transport, strengthen photosynthesis, prolong the functional period of leaves, make grains plump and full, and increase yield. Phosphorus fertilizer is suitable as basal fertilizer, while potassium fertilizer is better applied as topdressing.

5. Appropriately supplement medium and trace elements.

The medium elements silicon, calcium, magnesium and sulfur all have the effect of enhancing the stress resistance of rice plants, improving plant disease resistance, and promoting rice growth. Practice shows that applying sulfur fertilizer to sulfur-deficient soil and applying silicon fertilizer to silicon-deficient soil both have significant yield-increasing effects. Trace elements such as zinc and boron can improve the oxygen supply to rice roots, enhance the stress resistance of rice plants, improve plant disease resistance, promote later-stage root development, prolong the leaf functional period, and prevent premature senescence; they can accelerate flower development, increase pollen quantity, promote pollen germination, and help increase the panicle-bearing rate of rice; they can also promote larger panicles and more grains, improve the seed-setting rate and grain plumpness, thereby increasing rice grain yield.

II. Reference Fertilization Models for High-Yield Rice

The soil testing and formulated fertilization model for rice with a yield of 450-550 kg per mu is as follows:

(1) Total Fertilizer Application and Ratio

The ratio of nitrogen, phosphorus and potassium in fertilization should be about 1:0.5:0.9, and the total amount is approximately: nitrogen 10-13 kg, phosphorus pentoxide 5-7 kg, potassium oxide 8-12 kg.

(2) Fertilization Plan

1. Basal fertilizer:

(1) Organic fertilizer: generally for early rice, apply 1000-2000 kg of fresh green manure per mu, or 500-1000 kg of barnyard manure, or 60-80 kg of commercial organic fertilizer; for late rice, early rice straw can be returned to the field as organic fertilizer (the return amount is 1/2-2/3 of the early rice straw), or apply 500-1000 kg of barnyard manure per mu, or 80-100 kg of commercial organic fertilizer; for single-season rice, apply 500-1000 kg of barnyard manure per mu, or 80-100 kg of commercial organic fertilizer.

(2) Chemical fertilizer: urea 7-9 kg, calcium magnesium phosphate fertilizer 35-45 kg, potassium chloride 4-6 kg, zinc sulfate 1 kg.