The rice is very demanding to the quality of the soil, since it has an underdeveloped root system, which penetrates the soil by a maximum of 60 cm and a high transpiration coefficient of 400-800. It grows well on soils of heavy particle size distribution. The optimum pH for rice is 4-6.5.
To create 1 ton of grain and an appropriate amount of straw, rice takes up from the soil:
Most of all rice needs these elements during earing. During the tillering and flowering phases, 75% of total nitrogen, 95% of phosphorus and 80% of total potassium are assimilated.
When the seedlings just appeared, nitrogen and phosphorus are critical. The lack of phosphorus at this stage slows down the protein metabolism and the growth in general, the grain will be smaller size. Potash fertilizers will be needed already against the general background of a sufficient supply of nitrogen and phosphorus. In general, rice should be attributed to crops that need intensive fertilizer.
The upcoming dose of application is determined by the mineral content of the soil. It is permissible, simultaneously with the use of mineral fertilizers, to use manure (30-40 t/ha), to plow the green mass of alfalfa, leguminous plants or intermediate crops. The use of green fertilizers can increase the yield by 1 ton/ha.
The optimal doses for fertilizers can be considered as follows:
With such doses, we can expect a yield increase of 1.5-2.5 t/ha. If the culture precursor on the field was leguminous, then the dose of nitrogen from the list above can be reduced by half. It must always be remembered that an excess of nitrogen can cause lodging of rice crops, worsen the ripening of grain, increase the susceptibility of various diseases.
The selected dose of nitrogen is better to divide on the main application and feeding. They are carried out during the emergence of shoots and during the phases of tillering and the stem growing. This use of nitrogen gives a better yield increase than putting all of the same dose at one time. In addition, it is desirable to use ammonium and amide forms of nitrogen than nitrate. Long-acting type of fertilizers are preferred.
The introduction of phosphorus in doses of 60-90 kg/ha makes it possible to expect an increase in yield by 0.6-0.8 kg/ha. Exceeding this dose recommendation can give any noticeable result only on salt marshes.
Since rice is usually grown on heavy type of soils, where there is enough potassium even without additional application, then you should not expect a significant increase in yield from its use. You can use potassium as additional feeding in the phase of 5-8 leaves.
Since rice is grown under conditions of excess water, some micronutrient deficiencies occur. Boron, manganese, zinc and copper increase the resistance of rice to salinity, cobalt and molybdenum contribute to higher yields.
Especially great need for zinc - rice takes up to 300 grams of this metal from each hectare of crops. It is better to applicate it using the foliar way.
To provide the plants with manganese, usually it is enough to perform seed treatment.