The phenomenon of premature aging of corn often occurs, corn is the main food crop on the mainland, due to its strong adaptability, it is widely cultivated in most parts of the continent, corn is easy to grow, easy to manage, and has high yields. Due to the late stage of corn growth, drought or pests and diseases, after entering the milk maturity, there will be yellowing and wilting of the middle and upper leaves, loose and drooping leaves wrapping the ears, the stems close to the ground become soft and easy to break, the underground root system dies, and the phenomenon of stunted development of corn kernels is called premature corn aging. This time coincides with the transport and accumulation of a large number of photosynthetic products into the grains, and the premature decay of roots and leaves, which seriously affects the manufacturing, transportation and accumulation of photosynthesis products, often resulting in insufficient corn grains and reduced grain weight. If the prevention and control of corn is not carried out in time or the control is not done properly after premature aging, the production capacity will be reduced by more than 15%. In the process of planting corn, corn farmers need to pay attention to preventing the occurrence of premature aging and avoid reducing yield and harvest. This paper will focus on the causes of premature senescence of maize and propose corresponding control measures.
1. The main factors causing premature corn aging
1. Late defertilization: corn milk is the peak period of corn fertilizer after maturity, if the soil fertility is insufficient and can not be applied in time, then corn will be premature aging due to poor cultivation conditions.
2. Drought: corn is a crop that needs more water, corn milk is ripe after corn needs water, fertilizer needs the peak period, if the weather is dry can not be watered in time, it will affect the development of corn roots and the ability to absorb nutrients, the plant will be weak and yellow, resulting in reduced yield.
3. Pests and diseases: the harm of corn large and small leaf spot, the large spot disease appears on the corn leaves with blue-brown water-stained spots, and then expands to the surrounding green dark brown, the middle light brown mold layer, in the later stage of the serious disease, the longitudinal cracks of the disease spots spread staggeredly to make the leaves wilt and affect the photosynthesis of leaves. Small spot disease occurs more often when maize is tasseled and flowering, and the leaves die when it is severe.
Second, the main prevention and control measures
1. Select green stalk yellow ripening and anti-premature aging varieties, this kind of variety in the later stage, the upper leaves are still green, the leaf life is longer, more photosynthetic products can be manufactured to transport to the grains, to ensure that there are rich nutrients transported to the grains during the filling process, even if this is the case to reach physiological maturity (grain maturity, bracts turn yellow), the early and upper leaves still have a large part of the green. When purchasing corn seeds, choose corn varieties suitable for local planting and choose varieties with strong disease resistance, which can prevent the occurrence of premature corn senescence and achieve the purpose of high and stable yield.
Second, the application of grain fertilizer, after the corn enters the milk ripening, the middle and upper leaves change yellow, gradually wilt, and the phenomenon of the gradual death of the underground root system is the premature aging of corn, this time is the transfer and accumulation of a large number of photosynthesis products to the grains, and the premature decay of roots and leaves, which seriously affects the manufacturing, transportation and accumulation of photosynthesis products, often causes the grains to be not full, the grain weight is reduced, and the main reason for the morning decline of corn is the later defertilization. Therefore, in the early stage of corn silking, 4-5 kg of urea per mu should be topdressed, or potassium dihydrogen phosphate should be used for foliar spraying, especially for varieties with long growth period or sandy soil, and grain fertilizer should be applied to prevent premature root and leaf senescence and ensure the normal process of grain filling and maturation.
Third, pest control, for corn diseases, to prevent in advance, the policy of comprehensive prevention and control, can be mixed in advance of seed dressing, seed dressing can not be prevented, in the early stage of the disease to spray fungicides in time for prevention. The prevention and control measures for large and small spot diseases are mainly to select disease-resistant varieties, rotate crops, clean the countryside, and uproot diseased plants. After the onset of the disease, 400 kg of water should be used with 0.5 kg of 50% antibacterial special, or 250-300 kg of water with 0.5 kg of 50% rice blast emulsion, and 75-100 kg of liquid medicine should be sprayed per mu.
Fourth, drought resistance and waterlogging: corn growth in the late stage of drought and waterlogging will cause premature root and leaf aging, if there is drought in the field, to irrigate in time, in the rainy season, due to too much rain, corn roots will be damaged due to lack of oxygen, resulting in the occurrence of premature aging, drought watering, after heavy rain should pay attention to drainage.