Drought

Weather Update: Unsettled Weather Continues

Over the last two weeks, a more active pattern has brought numerous rounds of showers and thunderstorms across the Buckeye State. Many areas, from west central to southeast Ohio have received 2 inches of rain or more, with pockets of 4-6 inches across western Franklin, Fairfield, and Perry Counties. This has resulted in a decline in drought areas from 78% to 33% as of Thursday, June 22, 2023 (US Drought Monitor), leading to some improvement in crop conditions. However, large portions of southwest, northwest, and northeast Ohio have received less than normal precipitation over this period (Figure 1), intensifying drought conditions across these areas. Our CFAES Rapid Response Team continues to manage the early drought response resource site and encourages readers to continue to submit observations and impacts for your location by visiting https://go.osu.edu/drought_cmor.

Forecast

An upper-level low-pressure system is sliding east across the lower Great Lakes with showers and isolated storms on Monday and Tuesday. Temperatures are expected to remain cool on Tuesday with highs in the 70s and overnight lows in the 60s. Tranquil weather will return for Wednesday with highs in the mid-70s to low 80s across the state. A warming trend will continue for Thursday through Sunday, with highs generally in the 80s, pushing 90°F across the south. With warmer temperatures and increased humidity, isolated showers and storms are also possible throughout this period. The current forecast shows 0.25-0.5” is expected this week across northern counties, with totals over 1” near the Ohio River.

The Climate Prediction Center’s 8-14 Day Outlook and the 16-Day Rainfall Outlook from NOAA/NWS/Ohio River Forecast Center indicate that probabilities for temperatures and precipitation are leaning above average for the period July 3 – 9, 2023 (Figure 3). Climate averages include a high-temperature range of 83-86°F, a low-temperature range of 62-66°F, and average weekly total precipitation of 0.85-1.15 inches.

Potential for Nitrate Problems in Drought Stressed Corn

Source: Peter Thomison, Laura Lindsey, OSU

Have very dry soil conditions increase the potential for toxic levels of nitrates in corn harvested for silage? Nitrates absorbed from the soil by plant roots are normally incorporated into plant tissue as amino acids, proteins, and other nitrogenous compounds. Thus, the concentration of nitrate in the plant is usually low. The primary site for converting nitrates to these products is in the growing leaves. Under unfavorable growing conditions, especially drought, this conversion process is slowed, causing nitrate to accumulate in the stalks, stems, and other conductive tissue. The highest concentration of nitrates is in the lower part of the stalk or stem. For example, the bulk of the nitrate in a drought-stricken corn plant can be found in the bottom third of the stalk. If moisture conditions improve, the conversion process accelerates and within a few days, nitrate levels in the plant return to normal.

The highest levels of nitrate accumulate when drought occurs after a period of heavy nitrate uptake by the corn plant. Heavy nitrate uptake begins at the V6 growth stage and continues through the silking stage. Therefore, a drought during or immediately after pollination is often associated with the highest accumulation of nitrates. Extended drought prior to pollination is not necessarily a prelude to high accumulations of nitrate. The resumption of normal plant growth from heavy rainfall will reduce nitrate accumulation in corn plants, and harvest should be delayed for at least 1 to 2 weeks after the rainfall. Not all drought conditions cause high nitrate levels in plant. If the soil nitrate supply is low in the dry soil surface, plant roots will not absorb nitrates. Some soil moisture is necessary for absorption and accumulation of the nitrates.

If growers want to salvage part of their drought damaged corn crop as silage, it’s best to delay harvest to maximize grain filling, if ears have formed. Even though leaves may be dying, the stalk and ear often have enough extra water for good keep. Kernels will continue to fill and the increases in dry matter will more than compensate for leaf loss unless plants are actually dying or dead. Moreover, if nitrate levels are high or questionable, they will decrease as the plant gets older and nitrates are converted to proteins in the ear.