How to comprehensively defend against midsummer drought in corn?

The dog days usually refer to the sanfu period from mid-July to mid-August, and drought occurring during this period is commonly called midsummer (summer) drought. Drought at this time causes the most serious harm to corn, so people call the drought disaster occurring in corn during this period “neck-gripping drought”. Neck-gripping drought affects tasseling, flowering and silking, pollination and seed set in summer corn, thereby causing severe yield reduction.

I. Standards for midsummer drought The precipitation standard for midsummer drought disaster in summer corn is that among the 3 ten-day periods from late July to mid-August, rainfall in more than two consecutive ten-day periods is less than 50mm, and the total rainfall of the 3 ten-day periods is less than 100mm.

The soil moisture standard for dog days drought is that when soil moisture drops to 65%-70% of maximum water-holding capacity, it is mild drought; 55%-65% is moderate drought; less than 55% is severe drought.

The morphological indicators of midsummer drought are: during the booting, flowering and pollination stage, and grain formation stage of corn, lower leaves of the plant showing brief curling and wilting at noon is mild drought; both upper and lower leaves of the corn plant showing brief wilting at noon is moderate drought; upper and lower leaves of the corn plant showing permanent wilting (unable to recover at night) is severe drought.

II. Characteristics and harm of midsummer drought During the dog days in Anhui Province, summer corn is exactly in the booting, flowering and pollination stage, and grain formation stage, which is also the period when summer corn needs the most water in its entire life and is most sensitive to drought. The period from booting to grain formation in corn is the least drought-tolerant period in its entire life, and the impact of drought during this period has long-lasting continuity; in particular, drought encountered during the flowering and seed-setting period has irreversible continuity. Once it encounters long-term severe drought damage, it will cause pollen death, silk drying, inability to pollinate and set seed, resulting in large-scale yield reduction. Hence the farming proverb “Early drought does not count as drought; midsummer drought cuts yield by half.” A large number of experimental results show that after suffering severe drought disaster at different growth stages, the extent of yield reduction varies greatly: generally 25% yield reduction at the jointing stage, 30% at the booting stage, and 40% at the flowering stage.

III. Countermeasures for midsummer drought in corn When midsummer drought reaches the moderate standard, irrigation must be carried out as early as possible to facilitate normal flowering, pollination and seed setting in corn, or to ensure the smooth progress of grain formation and filling. It is worth noting that midsummer drought is caused by the control of the western Pacific subtropical high, and this subtropical high is powerful and broad in scope, often lasting a long time, causing drought with high severity, long duration, and heavy damage. Therefore, once midsummer drought occurs, it is necessary to take advantage of abundant water sources and irrigate promptly with “harvest water” to play the role of irrigation in protecting a bumper harvest. Otherwise, when drought damage becomes severe, seedlings wither, leaves scorch, and water sources dry up, then irrigating with “life-saving water” often yields twice the result with half the effort.