Delaware Agronomy Blog

University of Delaware Cooperative Extension

Category: Corn (page 3 of 7)

Keep Stress Down During Reproductive Stages

July 23, 2021 / / Comments Off on Keep Stress Down During Reproductive Stages

 

Corn silks have pollinated kernels as they move into the R2 stage

A corn ear that has pollinated and is in the R2 ( blister) stage.

As we enter the grain fill period, with some of our fields already at R2 (blister stage) or R3 (milk stage), it is important to keep stress down. Fields still at R1 or R2 (mid-May planting dates) may have the most to lose as kernels are being pollinated and start to fill. In past field trials, we have observed that yield correlates the best between about R2-R4 (from drone imagery, see below), so while there isn’t much you can do to improve yield, you can certainly do your best to maintain it by managing irrigation wherever it is needed.

Vegetation indexes and their correlation to yield over the corn growing season.

Vegetation indexes and their correlation to yield over the corn growing season.

July Temperatures and Pollination

July 15, 2021 / / Comments Off on July Temperatures and Pollination

According to data from the last two years (https://sites.udel.edu/agronomy/2020/09/23/2019-2020-corn-growing-degree-days/), silking and pollination (R1) has occurred between 1320 and 1594 growing degree days, while VT (tasseling) occurs between 1200-1300. In many of our research fields, VT also began to occur in this range last week, followed quickly by silking. Stress during pollination can determine initial pollination and kernel set, so temperature becomes very important. Planting date is an important part of this, as corn growth will follow heat accumulation, so cooler springs will take longer to reach R1 and vice versa. Continue reading

Checking Vegetative Growth Stages

May 26, 2021 / / Comments Off on Checking Vegetative Growth Stages

Corn at our research station is at V4, which means we will probably be sidedressing several fields next week. Anyone who planted prior to April 25th may be one leaf ahead, and plans for sidedressing should be done. If you are unsure of which stage you are at, one common method is to count leaves based on the presence of the collar (Figure 1a). While many leaves can be emerged from the whorl, only those with collars are considered fully developed. Continue reading

A Warmer 2021 is Boosting Emergence

May 4, 2021 / / Comments Off on A Warmer 2021 is Boosting Emergence
Emerging corn in a rye cover crop

Emerging corn in a rye cover crop

While it may not seem much warmer than it was in 2020, having steady days above 50°F had provided much faster emergence than last year. In 2019 we were getting about 10 growing degree days (GDD) per day, while now we are seeing 15-20. The threshold for emergence is about 100-120 GDD, which we have reached for most fields planted between April 15 and April 22nd (Table 1). In 2020, we had only reached half of that (60-90 statewide) over the same time period.

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Cover Crop Termination for 2021

March 31, 2021 / / Comments Off on Cover Crop Termination for 2021

Jamie Taraila,  Jarrod Miller,  and Amy Shober

With April and warmer temperatures finally here, it is time to think about cover crop termination. This spring, we expect lower cover crop biomass at burndown due to the cool, wet winter conditions that delayed growth, particularly small grains. Therefore, termination timing decisions are very important this year. We must recognize that there are pros and cons of early and late cover crop termination and make decisions that maximize benefits.

Figure 1: Vetch cover crop before spring corn planting.

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