MG III soybeans have been utilized in the early soybean production system (ESPS) in the Midsouth, especially on non-irrigated field. On the other hand, due to the early warm spring temperature, planting dates have been also pushed into March in the ESPS in recent years. However, research results indicated that March-planting inhibited the yield potential of yield potential of early soybeans, such as MG IIIs. This paper is to discuss the philological effects of early planting (March) on early MG soybeans (MG III). Experiments conducted at seven locations in Mississippi and Louisiana with time span of eight years (1998-2006) have been summarized. Results indicated that March planting has a detrimental effect on the yield potential of MG III soybeans mainly due to lower values of yield components such as short plant height, early flowering, lower position of flowers and pods and less pod number per plant. Short photoperiod induced early flowering is the key to all the subsequent effects. In practice, late April-planting showed the best yield potential for MG III soybeans in the Midsouth.