Rice empty grains refer to unfertilized empty grains and half empty grains that cannot develop after fertilization, which is a common physiological disorder in rice production. Under normal climate and cultivation conditions, the empty grain rate of rice is about 10-20%; But in abnormal years, the empty grain can reach 30-40% or even higher, which has a significant impact on rice yield.
Therefore, in rice production, in addition to striving for multiple and large panicles, it is also necessary to reduce empty grains, improve seed setting rate, and increase thousand grain weight in order to achieve high yield. Now, the editor will talk about the causes and prevention measures of empty chaff, for your reference:
Causes of empty grain formation
1. Internal factors formation:
There are generally two reasons for the internal causes of rice husks:
One is incomplete development of male and female sexual organs before heading, which prevents the completion of fertilization and results in the formation of empty shells.
Secondly, when heading and flowering, the male and female sexual organs cannot coordinate and cannot receive pollen, resulting in the formation of empty shells.
The internal cause of the formation of chaff is mainly due to poor nutrient supply of grains in the ear, which leads to the cessation of development of the ovary or endosperm and results in chaff.
2. External factors causing:
The external factors of empty rice grains are relatively complex, including climatic and cultivation conditions.
In terms of climatic conditions, meteorological factors such as temperature, humidity, light, and wind have a significant impact on the formation of empty grains. The most suitable temperature for rice heading and flowering is 25-30 ℃. Even temperatures below 20 ℃ cannot complete the fertilization process and form empty shells. But encountering high temperatures above 35 ℃ also has adverse effects on the fertilization process, and the empty shell rate will increase significantly.
Light also has a significant impact on the formation of empty grains. Due to the fact that over 95% of the dry matter in rice grains comes from the products of photosynthesis, during the heading and fruiting period, when there are many rainy days and insufficient sunlight, empty grains will increase.
Humidity and wind speed also have a certain impact on the formation of empty grains. The most suitable humidity for rice flowering and fertilization is 70-80%. A dry climate is not conducive to fertilization and can easily form empty shells. However, heavy rain or continuous rainy days during the flowering period, as well as excessive humidity, can also affect fertilization and fruiting, resulting in empty grains.
In addition, improper cultivation conditions can also affect the formation of empty grains.
Excessive application of nitrogen fertilizer during the differentiation stage of young panicles leads to high nitrogen content in leaves, which is not conducive to the accumulation of nutrients and increases the number of empty grains. Insufficient nitrogen fertilizer in the early stage of heading can lead to premature senescence of heading leaves and increase the number of empty grains, resulting in reduced yield.
In addition to nitrogen fertilizer, the lack of phosphorus and potassium nutrients during the growth period of rice can also affect the decline of photosynthesis and physiological functions, and increase the number of empty grains.
In terms of irrigation, if there is a lack of water during the heading and flowering stages, it can lead to poor fertilization and fruiting, resulting in an increase in empty grains.
Poor drainage in paddy fields, or long-term deep irrigation, can cause black roots, prolonged and heavy sun drying in the middle stage, and premature water cut-off in the later stage, leading to premature aging and increased empty grains. Improper close planting, premature closure, poor ventilation and light transmission, or damage from pests and diseases, if not prevented and controlled in a timely manner, can also lead to a significant increase in empty grain, resulting in serious yield reduction.
Prevention and control measures for empty grains
1. Choose sturdy and good varieties.
The physiological morphology of rice varieties varies greatly, resulting in significant differences in seed setting rates. Generally, varieties with strong stress resistance and wide adaptability have high seed setting rates. In production, varieties that are cold resistant or heat-resistant, resistant to fertilizer and lodging, have neat heading, are not prone to premature aging in the later stage, and have strong disease and insect resistance should be selected. In adverse environments, the impact can be reduced to ensure a high seed setting rate.
2. Sow and transplant at the appropriate time to avoid damage from high and low temperatures.
Adapt to local conditions and arrange the season accordingly. Early maturing varieties should not be sown too early to avoid encountering low temperatures during the panicle stage, which may increase the number of empty grains.
3. Reasonable fertilization and irrigation can improve the fruiting rate.
Reasonable and dense planting, scientific water use, prevention of premature closure, affecting ventilation and light transmission, as well as later greening and premature aging, causing nutritional imbalance, creating favorable conditions for the formation and development of rice grains, thereby improving seed setting rate and promoting grain plumpness.
4. Take timely emergency measures to mitigate losses.
During the period from booting to heading and flowering of rice, if high or low temperatures are encountered, timely defense measures should be taken to reduce damage and improve seed setting rate. During the booting stage of early rice or the flowering stage of late rice, if low temperatures below 20 ℃ are encountered, deep water should be promptly irrigated for insulation, which has a better effect.
If insulation agent is added while irrigating deep water, the effect will be better. During the heading and flowering stage of early rice, if it encounters high temperatures above 35 ℃, it is recommended to irrigate deep water daily and cool it down at night. The temperature can be appropriately lowered and the relative humidity can be increased, which is beneficial for improving the grain setting rate.
5. Topdressing outside the roots can be sprayed with phosphorus and potassium fertilizers.
When high or low temperatures occur, spraying phosphorus and potassium fertilizers can enhance the resistance of rice plants to high and low temperatures, which is beneficial for improving seed setting rate and increasing thousand grain weight.