2018-2020 Corn Weather Summary

Jarrod O. Miller, Extension Agronomist, jarrod@udel.edu; Cory Whaley, Sussex Co. Extension Ag Agent, whaley@udel.edu; Jake Jones, Extension Agriculture Agent, Kent County, jgjones@udel.edu; Dan Severson, Agriculture Agent, New Castle County, severson@udel.edu

Weather is always a limiting factor in crop production, and one we can’t control for. Fields with irrigation can potentially overcome limited rainfall, but high temperatures can still reduce yield during pollination and grain fill periods.

Over the past three years, spring has the larger fluxes in daily temperatures, with the potential for very cold weather in our early planting window. If weather remains above freezing, these cold days mostly delay early corn growth. That delay only becomes an issue later in the summer, where we can observe our highest temperatures during pollination (mid to late July). If temperature reduces pollination, there will be no kernels to fill later in the summer. One of the benefits of planting earlier is hitting pollination the first weeks of July, when our nights are still more likely to drop below 72°F. Yearly fluctuations show the luck that is involved, as 2018 had cooler weather in late July (Figure 1).

Figure 1. Temperatures from April-September 2018-2020

Planting earlier isn’t always an option due to spring rains, which can delay corn crops into early June. It appears that June planting is the most likely to pollinate during our hotter temperatures, so we should avoid late planting where possible. Over the past three years rainfall caused the most delays in 2018 (Figure 2), where most of the state had 10-15 inches of rain by June 1. This rainfall resulted in ponded, saturated soils for most of the early summer. The period of heavy rainfall in 2018 was followed by a long drought through late vegetative and early reproductive stages. Most parts of the state had similar rainfall totals.

Spring 2019 had steady rainfall (Figure 3), with periods of drought spread throughout the summer. However, by the end of 2019, sandy soils in Georgetown didn’t break 20 inches. Our most droughty spring appears to be 2020 (Figure 4), where we didn’t hit the 10” mark until the beginning of July. The excessive rainfall of the tropical storm gives Dover the appearance of greater water storage, but most of that probably had limited infiltration into our soils.

2018 Rainfall accumulation

Figure 2. 2018 Rainfall accumulation.

2019 Rainfall accumulation

Figure 3. 2019 Rainfall accumulation.

2020 Rainfall accumulation

Figure 4. 2020 Rainfall accumulation.

The only guarantee we have about 2021 is that it will be a variation of everything we see here. At some point during the growing season we will experience a drought, and yield can be protected in fields with irrigation. We know there is some early planting of soybeans being done in lieu of corn, but weather permitting, earlier corn planting will benefit with somewhat milder temperatures during pollination.

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