- Production Guide (read on-line)
- Variety Trial Results
- Production and market risk management
- Budgets
- Soybean vegetative and generative growth stages
- Soil sampling and fertility management
- Selecting the right varieties
- Planting Dates & Populations
- Seed Inoculation
- Double Cropping
- Weed management
- Soybean nematode control
- Soybean disease control
- Insects
- Management of soybean insects
- Soybean insect control
- Soybean Harvest
- Farm-stored soybean insect mamagement
- Introduction to precision agriculture
- Authors
- Contact Information
Maturity Groups & Growth Habits
Pawel Wiatrak, Emerson Shipe, and Jason Norsworthy
Soybeans flower in response to day length and temperature and therefore are called facultative photoperiod sensitive. Varieties grown in the United States are divided into 13 maturity groups (MG), with MG 000 being the earliest and adapted to northern Minnesota and southern Canada, to MG X adapted to southern Texas.
The earlier varieties bloom when days are long and nights are short, while the later-maturing varieties bloom under relatively shorter days and longer nights. During the summer, days are longer at more northern latitudes, therefore the early MG will initiate flowering when days are longer. Earlier and later maturing groups develop differently and knowing the growth habit of different maturity groups (MG) can help with the crop management.
Most indeterminate varieties are adapted to maturity group IV and earlier. These varieties have overlapping vegetative and reproductive growth stages. Terminal growth bud on the main stem continues to grow after the first bloom and most of the pods are on the main stem. Flowers and pods develop at different times and rates depending on node locations. Nodes with the earliest flowers located near the bottom of stem; therefore, an indeterminate plant may contain pods with developing seed at lower nodes while upper nodes contain only small pods or flowers.
Most varieties with a determinate growth habit (maturity group V and later) have distinct vegetative and reproductive growth stages. Number of nodes and plant height of the main stem are terminated at the full bloom stage (R2). However, branch growth continues after first bloom and the number of pods often greater on branches than the main stem.
Due to different blooming periods, the recommended planting dates of different maturity groups in South Carolina are:
- MG IV and earlier - April 15 through May 10.
- MG V to VI - May 1 through June 10.
- MG VII to MG VIII - June 1 through July 1.
The following are approximate harvest dates of maturity groups V to VIII when planted full-season May 1 to June 10 in South Carolina:
- Group V: October 1 to 15.
- Group VI: October 10 to 25.
- Group VII and VIII: October 25 to November 15.
Harvest maturity is an important consideration for farmers who wish to:
- Plant small grain for grazing early in the fall after soybean harvest
- Harvest soybeans from Carolina bays or river bottoms before late fall rains saturate soils and make harvest difficult and untimely
- Avoid early frost damage to the crop, especially in the Piedmont region.
- Spread maturities to reduce risk of drought damage.
Since there is a range of harvest maturities of about 45 days for MG V through VIII, there is also a range of time for the bloom through pod-fill stages. Because adequate soil moisture from bloom through pod fill is important for good yields, farmers should consider planting varieties from more than one maturity group to reduce the risks of drought damage during pod fill. For example, in 2001, a drought in South Carolina in August and September reduced yields of many late planted MG VII and VIII varieties.
Farmers with earlier planted MG V and VI varieties were able to avoid most of the drought effects. The practice of spreading the maturity groups also spreads out harvest and thus helps to avoid harvest delays, which can reduce both yield and quality of the crop.