Fertilizer and Urea Application Rates and Precautions for Rice and Wheat per Mu

Rice and wheat are both grasses (Poaceae) and are also among humanity's staple foods. So how much fertilizer and urea should be applied per mu for each? What precautions are there? Here is a detailed introduction.

How much fertilizer and urea to use per mu?

I. Rice

1. The principle of rice fertilization should be: organic fertilizer and phosphate fertilizer as base fertilizer, potassium fertilizer mainly as tillering fertilizer, nitrogen fertilizer applied evenly in multiple splits, with special attention to plump-bud and plump-grain fertilizer, so as to achieve sufficient panicles while promoting large panicles and large grains.

(1) Base fertilizer mainly organic fertilizer. According to measurements, 50%-60% of the nitrogen and 70% of the phosphorus and potassium taken up by rice come from the soil. Insufficient fertilization will excessively deplete the soil's potential nutrients and reduce soil fertility, so increasing organic fertilizer application is an important way to maintain and improve soil fertility. Therefore, rice production should emphasize accumulating farmyard manure, developing the livestock industry to apply more barn manure and plant more green manure crops, and promoting panicle harvesting and rice straw return to the field, so that organic fertilizer accounts for 40% of the total fertilizer applied during the whole period.

(2) Apply tillering fertilizer early in appropriate amounts. The first application is 6-7.5 kg of urea per mu; about 7 days later, according to seedling conditions, for fields with poor growth, apply a second tillering fertilizer of no more than 4 kg of urea per mu; for fields with little organic fertilizer and potassium deficiency, apply 5-7.5 kg of potassium fertilizer per mu as a top dressing.

(3) Apply panicle fertilizer according to seedling conditions. Both flower-promoting fertilizer and flower-preserving fertilizer can be applied, each time 5 kg of urea per mu. Rice has a high demand for potassium fertilizer. After draining the field and reflooding, combine with nitrogen top dressing and apply about 2.5 kg of potassium fertilizer per mu, which has a significant yield-increasing effect.

(4) Apply grain fertilizer and foliar top dressing according to seedling conditions. For rice plants whose leaf color is too pale before initial heading, broadcast 2-2.5 kg of urea per mu; for fields that turn yellow too early after full heading, apply 2.5-3 kg of urea per mu; for normal-growing hybrid rice, only 500-750 g of urea diluted in 50 kg of water should be sprayed as grain fertilizer.

2. Urea contains 46% nitrogen and is an ideal fertilizer for rice. However, when applied improperly and unreasonably, it not only causes waste and has no effect, but instead causes the occurrence and spread of rice diseases.

(1) Base fertilizer should be applied deep. Before autumn plowing or after spring plowing, spread urea evenly on the field surface, then plow immediately to bury it in the soil. Because base fertilizer is applied deep and has a long fertilizer effect, the application amount should not be too much, so as to avoid excessive vegetative growth and lodging in the later stage of rice.

(2) Tillering fertilizer is applied 7-10 days after rice transplanting, at 5-7 kg of urea per mu.

(3) Spraying "urea" fertilizer can only be done one month after sowing and emergence. Generally speaking, there is no strict boundary between fertilizers used for foliar application and those used for root soil application. In principle, any fertilizer that is non-toxic, harmless and contains nutrients can be used.

(4) For late rice seedlings, apply startup fertilizer (send-off fertilizer) preferably 2 days before transplanting at 150 kg of ammonium sulfate or 75 kg of urea per hectare.

II. Wheat

(1). For winter wheat fertilizer application technology, it is generally believed that for every 100 kg of wheat grain produced, about 2.8-3.2 kg of pure nitrogen, 1-1.5 kg of phosphorus and 2-4 kg of potassium need to be absorbed, with the ratio of nitrogen, phosphorus and potassium being about 1:0.4:1. Among these, nitrogen and phosphorus are mainly concentrated in the grain, accounting for 76% and 82.4% of the total content of the whole plant respectively, while potassium is mainly concentrated in the stems and leaves, accounting for 77.6% of the total content of the whole plant.

(2) At the seedling stage of wheat, there should be sufficient nitrogen and appropriate phosphorus and potassium nutrition. According to the growth pattern and nutritional characteristics of wheat, base fertilizer should be applied heavily and top dressing should be applied early. The amount of base fertilizer should generally account for 60%-80% of the total fertilizer application, and top dressing should account for 40%-20%.

(3) According to data from fields with a spring wheat yield of 7500 kg/hectare compiled by the Soil and Fertilizer Institute of the Qinghai Academy of Agriculture and Forestry Sciences, for every 100 kg of grain produced, about 2.5-3.0 kg of nitrogen, 0.78-1.17 kg of phosphorus and 1.9-4.2 kg of potassium are required. The ratio of nitrogen, phosphorus and potassium is 2.8:1:3.15. Spring wheat has two peak periods of nitrogen, phosphorus and potassium uptake: the first is from jointing to booting, and the second is from flowering to milk-ripe, with the former slightly higher than the latter. The phosphorus uptake rate rises continuously from emergence to milk-ripe, increases sharply from jointing, and reaches its highest value at milk-ripe. According to the growth pattern and nutritional characteristics of spring wheat, base fertilizer should be applied heavily and top dressing should be applied early.

(4) Base fertilizer: apply 30-60 tons of farmyard manure, 375-600 kg of ammonium bicarbonate and 450-600 kg of superphosphate per hectare.

(5) Seed fertilizer: generally apply 150 kg of ammonium bicarbonate and 225-375 kg of superphosphate per hectare, mixed with 1500 kg of high-quality farmyard manure, or 150-300 kg of binary nitrogen-phosphorus compound fertilizer. When sowing, combined with a small amount of seed fertilizer, apply 75-120 kg of diammonium phosphate per hectare, and no top dressing afterward. This method is suitable for dryland.

The urea applied to wheat fields with different fertility levels is also different.

(1) High-fertility wheat fields: apply 5-7 kg of pure nitrogen as base fertilizer per mu (equivalent to about 13 kg of urea or about 35 kg of ammonium bicarbonate), or use wheat formula fertilizer with a total content of nitrogen, phosphorus, potassium and zinc of ≥50% (15-18-17 or 18-19-13) at 35-45 kg/mu.

(2) Medium-fertility wheat fields: apply 5-7 kg of pure nitrogen as base fertilizer per mu (equivalent to about 15 kg of urea or about 40 kg of ammonium bicarbonate), or use wheat formula fertilizer with a total content of nitrogen, phosphorus, potassium and zinc of ≥50% (15-18-17 or 18-19-13) at 30-40 kg.

(3) Low-fertility wheat fields: apply 5-7 kg of pure nitrogen as base fertilizer per mu (equivalent to about 10 kg of urea or about 26 kg of ammonium bicarbonate), or use wheat formula fertilizer with a total content of nitrogen, phosphorus, potassium and zinc of ≥54% (18-22-14) at 30-40 kg.

(4) Fertilization method: for nitrogen fertilizer in high-yield plots, use 60% of the total as base fertilizer and 40% as top dressing; in medium- and low-yield plots, use 50% of the total as base fertilizer, 10% as seed fertilizer and 40% as top dressing.