What is the standard for timely harvesting of corn

The standards for timely harvesting of corn mainly include yellowing and drying of ear buds and leaves, disappearance of grain milk line, compliance with grain hardness standards, yellowing of plant stems and leaves, and low field lodging rate. Harvesting corn too early or too late can affect yield and quality, and should be judged comprehensively based on variety characteristics and climatic conditions.

1. When the outer layer of corn ear bracts turns from green to yellow white and the texture becomes dry, it indicates that the grain has entered the maturity stage. At this point, a separation layer is formed at the connection between the bracts and the ears, which can be easily peeled off by gently tearing. If the bracts are still green and have a high moisture content, the grain filling is not yet complete, and premature harvesting can lead to a decrease in thousand grain weight.

2. Disappearance of grain milk line

During the mature stage of maize, milk lines formed by milky white slurry can be seen when cutting the grain longitudinally. As starch continues to deposit, the milk lines gradually move towards the embryo end until they completely disappear. After the disappearance of the milk line, the accumulation of dry matter in the grains reaches its peak, and harvesting can ensure maximum yield at this time. When the position of the milk line is one-third of the distance from the top of the grain, it is the waxing stage, suitable for harvesting fresh corn.

3. Grain hardness meets the standard

When pressing the top of the grain with a fingernail, there is a clear indentation but no juice leakage, indicating that the moisture content of the grain has dropped below 28%, meeting the mechanical harvesting standard. The seeds present an inherent luster of the variety and the embryo is concave. When the nails are difficult to cut, the moisture content is about 25%, making it suitable for long-term storage. Soft grains are prone to damage during threshing, which affects the quality of the product.

4. When 3-4 leaves in the lower part of a corn plant turn yellow and the elasticity of the stem base weakens, it reflects a decline in root vitality and the transfer of nutrients is basically completed. At this time, keeping 2-3 green leaves on the plant can balance grain harvesting and straw utilization. If the whole plant is harvested with green stalks, the dehydration of the grains is slow and prone to mold growth.

5. Low lodging rate in the field

When the proportion of lodging plants in the field exceeds 15% from the late stage of milk ripening to the fully ripe stage, they should be harvested in advance to avoid mold damage. For varieties that are resistant to lodging or fields with good upright conditions, they can be harvested after the seeds have fully matured. Harvesting in rainy areas should be completed within one week after the bracts and leaves dry up to prevent the occurrence of ear rot disease. After harvesting corn, it should be promptly dried or air dried to reduce the moisture content of the grains to below 14% for safe storage. Natural drying, mechanical drying, or ventilated storage can be used to avoid heap fermentation and heat generation. Stopping irrigation 15 days before harvest is beneficial for promoting grain dehydration. Sandy soil blocks can be harvested earlier, while sticky soil blocks should be harvested later. Different varieties need to adjust their harvest time according to the recommended growth period days in the approval announcement, combined with local accumulated temperature conditions. Grain directly harvested varieties can be delayed by 5-7 days compared to ear harvested varieties.