Optimizing Planting Date and Maturity Group

Soybean producers and consultants have been trying to pushthe yield limits on modern, high-yielding soybean varieties in recent years. Onemeans of improving yields is by being strategic about planting timing andmaturity group selection, which play a major role in achieving maximum yieldpotential in a given year. Weather is ultimately the driving factor fordeciding when field activities take place in North Carolina, making it nearlyimpossible for growers to stick to a strict planting and management calendar.

However, the more we understand the relationship betweenmaturity group, planting date, and weather patterns, the more likely we are toattain our goal of improving yield. The NC Soybean Producers has funded amulti-year study to further understand the influence of planting date andmaturity group selection in conjunction with a group of crop consultants acrossEastern NC.

This work was carried out over the last two years across 5locations in the eastern part of the stae. Two in the Tidewater region(Perquimans and Beaufort) and three in the Coastal Plain region (Northampton,Pitt, and Robeson).

In 2017, favorable weather in April and a rapid accumulationof heat units favored soybean planting in Mid-April, with the optimal maturitybeing in the 4.8 to 5.2 relative maturity (RM) range. The 2017 study includedeight varieties ranging from RM 4.8 to 5.9 evaluated across five locations inNC. In 2018, the number of varieties and maturity groups were expanded tocapture the extreme limits of soybean maturity typically grown in NC. 2018included varieties from RM 3.2 to 6.

Three planting were tested included an early planting(mid-April), a mid planting (mid-May), and a late planting (mid-June) .

The response of soybeans to planting date was very differentfrom location to location. We averaged data from 2017 and 2018 to give a morecomplete picture of what is “typical” of each of the locations evaluated.

In Perquimans, Mid-April and Mid-May planted soybeans in theRM range of Late III to Late IV were on average 13 bu/A better on averagecompared with Mid-June planted beans. However, the benefit of early planting inPerquimans was minimal or a non-factor when later maturing varieties wereplanted. The highest yielding scenario in Perquimans was an Early IV planted inMid-April and May.

 In Beaufort, highestyields were achieved when soybeans of the Late III, Early IV, Late IV RM groupswere planted in May. On average, these early varieties planted in mid-May outyielded mid-April beans by almost 14 bu/A and mid-June planted beans by nearly29 bu/A. Several late planted plots were lost due in 2018 to bad weather makingit difficult to analyze the full impact of the interaction.

In Pitt, the opposite trend was observed compared with theBlackland locations. At this location, early maturing varieties (Late III toLate IV) performed better as planting date was later in the season and latermaturing varieties performed better when planted earlier in the season. Optimalyields were achieved when Group IV’s were planted in June and when Group V’swere planting in April or May.

In Robeson County, in most cases, planting in mid-May andmid-June was better than planting in mid-April across all maturities. The“sweet spot” for Robeson was a mid-May planting timing and a Early V soybean. Similarto Pitt, early maturing varieties seemed to do better when planted later.

In Northampton County, Late V’s and Mid-Late VI’s performedbest overall compared to all other maturity groups. Group V and VI beans outyielded group III and IV beans by nearly 15 bushels on average and highestyields were achieved by planting a Mid-Late Group VI soybean in mid-April.

Weather played a major role in the outcome of this study in2018. Heavy rains in the early fall from Hurricane Florence hurt yields ofearly planted and/or early maturing soybeans, particularly in Robeson, Pitt,and Northampton counties. Less than ideal growing conditions in April were notconducive to producing the high yields that were seen with early maturingvarieties in the Tidewater region in 2017. Abnormally high rainfall in Junehurt stands of late planted beans in Beaufort causing some bean plots to beabandoned.

This two-year study suggests that over all locations andenvironments the ideal combination is a Late IV or Early V planted fromMid-April to Mid-May. While most seasons have a “sweet spot” with the mostpotential for outstanding yields, finding it can be a difficult propositionunless you spread your risk as a producer.

For instance, averaged across all locations, the cost ofmaking the wrong decision in variety and planting date could have been as muchas 35 bu/A. Of course there is no way to predict the weather but this research shows how critical it is tomanage risk by paying attention to weather forecasts at planting time,multi-year/multi-location variety trial data when selecting varieties, andplanting multiple varieties of varying maturities in order to avoid significantweather events.