Seasonal Patterns of Landrace Maize Root Architecture in Florida Under Limited Nitrogen Input.

Extensive root system will be beneficial for nutrient scavenging and is important for the region where nutrient leaching from agricultural areas causes numerous environmental concerns, such as Florida. Thus, exploiting germplasm, including landrace that has the potential for increased nutrient acquisition through large and extensive root systems could be critical contributions to breeding efforts for the region.  The objective of the study was to evaluate maize genotypes under a limited nitrogen environment in Florida sandy soils. Two Mexican landraces, Yucatan01 and Oaxaca01, and a commercial silage corn cultivar, Agratech 1023VIP, were planted with applications of 156 kg N/ha of ammonium sulfate, approximately 66% of the typical N application rate for the region. Seeds were planted 10 April 2014. The experimental design was a randomized complete block with six blocks. Root dimensions (length, and surface area) of the three genotypes were monitored on a two-week basis using a mini-rhizotron system (Bartz Tech. Co.) from May to September. Data were analyzed in four soil depth increments (0-20, 20-40, 40-60, and 60-90 cm soil depths) to investigate variation in seasonal root development. There were significant differences in root parameters between the two landrace cultivars and the commercial hybrid including total root length and surface area. Oaxaca01 and Agratech 1023VIP had similar patterns of root architecture at the 0-40 cm depth. For total root length, Yucatan01  had the most extensive root production in the 40-60 cm soil depth in June in comparison to the other genotypes: 479, 288, and 136 mm for Yucatan01, Oaxaca01, and  Agratech 1023VIP. Total root surface area showed similar patterns to root length. For instance, Yucatan01 showed a five-fold greater surface area than silage corn at the 40-60 cm soil depth in June: 98, 513, and 205 mm² for Agratech 1023VIP, Yucatan01 and Oaxaca01, respectively. The earlier and more extensive development of root architecture for the two Mexican landraces has the potential to better withstand adverse environments in the early growing season, with particular advantages for nutrient uptake and drought tolerance. Further quantification of full season changes in root length and surface area will be presented.