Knowledge about Mangzhong
The "芒" (máng) character in Mangzhong refers to the harvesting of awned crops like wheat, while the "种" (zhǒng) character refers to the sowing season for crops like millet and rice. The homophonic nature of "芒种" suggests that all crops are "busy sowing."
The general weather characteristics of Meiyu (plum rain) are numerous rainy days, heavy rainfall, high temperatures, and little sunshine, sometimes accompanied by low temperatures. About one-third (and in some years, one-half) of the annual rainfall in eastern China occurs during the Meiyu season. Meiyu in the middle and lower reaches of the Yangtze River generally begins after June. This is precisely when crops like rice and cotton are growing vigorously and require a great deal of water.
The reason for Meiyu formation is that after winter ends, the strength of the cold air weakens and it retreats northward. Correspondingly, the warm air from the south advances northward, extending to the middle and lower reaches of the Yangtze River. However, at this time, the cold air from the north still has considerable strength. As a result, the warm and cold air masses confront each other in the Yangtze-Huai River basin, forming a quasi-stationary front, which leads to continuous overcast and rainy weather. After a period, the warm air eventually overcomes the cold air, occupies the Yangtze-Huai River basin, and the Meiyu weather ends. The center of the rain belt then shifts to the Yellow-Huai River basin. At this time, the Yangtze-Huai River basin is busy with planting.
Meiyu is very beneficial for crops. In the eastern and middle-lower Yangtze River regions, if Meiyu is too light or arrives late, crops will suffer from drought.
"In April, Mangzhong means wheat is ready; in May, Mangzhong means wheat is not yet ready." This means that in North China, if Mangzhong falls in April, the wheat is mature, but if it falls in May, the wheat is not yet mature. Why is this? This is similar to the saying "In the second lunar month, Qingming means peach blossoms are open; in the third lunar month, Qingming means they are definitely not open," and it is all due to the lunar calendar calculation. According to the lunar calendar, a year is actually 354 or 355 days. This is 10-11 days shorter than the time it takes for the Earth to orbit the sun. Therefore, a leap month must be added every three years (sometimes two years) to make up for the shortfall. During a leap month, the solar terms are either advanced or delayed. Consequently, Mangzhong can sometimes be in April and sometimes in May. Chinese farmers are well aware that when Mangzhong is in April, due to an early "Beginning of Spring," the solar term is pushed forward, so planting is done early, before Mangzhong. When Mangzhong is in June, planting is done after the solar term. This is a scientific planting method known as "fixed solar terms, flexible measures."
"Sow broomcorn millet at Mangzhong, and also sow foxtail millet in a hurry." Broomcorn millet is a grass with the shortest growing period; early-maturing varieties can mature in 80 days, and even late-maturing varieties do not take more than 100 days. It is the last crop to be sown for the autumn harvest. Therefore, in North China, when there is a drought and other crops miss their planting time, broomcorn millet is often used as a substitute, and a good harvest can still be obtained. Under normal conditions, when broomcorn millet is sown at Mangzhong, foxtail millet can also be sown. However, foxtail millet has a longer growing period and may be damaged by frost. Therefore, the saying goes, "Sow broomcorn millet at Mangzhong, and also sow foxtail millet in a hurry."
The effective flowering period for cotton in the Yangtze River basin is in early to mid-September. This means the flowering period that allows cotton to boll and mature before the first frost generally requires 50-70 days, with frost occurring around mid-November. Therefore, to ensure cotton bolls and matures before the first frost and to guarantee high quality and yield, it is essential to strengthen seedling management to shorten the seedling growth period, promoting early budding and early flowering. This requires early seedling checks and reseeding, early hilling and weeding, early thinning and final plant spacing, early pest and disease control, and early topdressing.