Preventing lodging, premature senescence and delayed maturity in rice during the late growth stage
Abnormal phenomena in rice such as lodging, premature senescence and delayed maturity are caused by improper selection of varieties or by the influence of certain adverse factors during the growth and development of rice, resulting in conditions inconsistent with the normal growth targeted by cultivation, and seriously affecting the yield and quality of rice.
1. Lodging
Causes: Lodging is divided into root lodging and stem lodging. Root lodging occurs because rice plants remain in deep water for a long time, the root system develops poorly, roots are shallow, and the supporting force at the base is weak, so under slight wind and rain the plants easily fall flat. Stem lodging occurs because the cells at the base of the culm have a low cellulose content, the cell walls become thinner, and the culm is not sturdy enough to bear the weight of the upper part, resulting in lodging of varying degrees. From the perspective of cultivation management, the main causes of lodging are a shallow plough layer, excessively deep irrigation, excessively high planting density, poor root growth and development, and poor ventilation and light penetration within the population. Another cause is improper fertilizer and water management, one-sided heavy application of nitrogen fertilizer, excessively vigorous growth at the tillering stage, and too early canopy closure, causing excessive elongation of the internodes at the base of the culm.
Preventive measures: Irrigate scientifically. According to the different water requirements of rice at each growth and development stage, practice shallow-water transplanting, 1-cun water for tillering, and drain the field well at the end of tillering. On the premise of ensuring water demand, there must also be sufficient oxygen content in the soil to promote strong root growth. Reasonable close planting helps ventilation and light penetration. Fertilize rationally; do not apply nitrogen fertilizer one-sidedly, and increase the application of phosphorus and potassium fertilizers, so that the culm becomes solid and strong, elongation of the basal internodes is controlled, and the ability to resist lodging is thereby enhanced.
2. Premature senescence
Premature senescence refers to the premature decline of physiological functions in parts such as leaves and stems during the late growth period of rice, which weakens the photosynthetic capacity of functional leaves and reduces the source of filling substances, and is one of the main causes of empty grains. Causes: Some plants show premature senescence because they grew too vigorously in the early stage, which intensifies the contradiction between the population and the individual in the late growth stage and accelerates the death of roots and leaves. Another cause is improper fertilizer and water management in the later stage, too early cutting off of water, and insufficient supply of nitrogen and phosphorus fertilizers, so that the vegetative growth of the plants cannot receive nutrient supplementation. In other cases, because the soil has poor permeability and contains much oxygen deficiency and toxic reducing substances, the rice root system develops poorly in the later stage, the ability of the roots to absorb nutrients is weakened, and the aboveground part grows weakly as a result.
Preventive measures: Manage water scientifically, mainly to raise water temperature. From full heading to the grain-filling stage, irrigate frequently with shallow water to raise temperature and promote ripening. From the milk-ripe to yellow-ripe stage, irrigate intermittently to increase soil aeration, enhance root activity, and nourish roots and preserve leaves. Fertilize rationally, and skillfully apply ear and grain fertilizer to improve the photosynthetic capacity of the leaves.
3. Delayed maturity
Causes: The influence of factors such as low temperature, cold damage and soil drought hinders normal growth and development, delays reproductive growth, and prevents nutrients from being transported to reproductive growth on time. Insufficient photosynthesis intensity and light duration also aggravate the degree of delayed maturity. Applying too much nitrogen fertilizer or applying it too late, with excessive vegetative growth in the later stage, also easily leads to delayed maturity. If the population density is too high and ventilation and light penetration are poor, causing stems and leaves to be over-luxuriant, symptoms of delayed maturity are also likely to occur.
Preventive measures: Irrigate scientifically to prevent drought. Plant at a reasonable density, avoid transplanting too densely, which affects ventilation and light penetration and causes excessive plant growth. Nitrogen fertilizer should be supplied at the right time and in the right amount, and should not be excessive, so as to prevent delayed maturity caused by excessive vegetative growth of the plants.