Modelling Pod Growth Rate of Bambara Groundnut (Vigna subterraneaVerdc.) in Response to Photoperiod and Temperature

Abstract

Photoperiod and temperature are important environmental factors that affect the adaptation of bambara groundnut (Vigna subterraneaVerdc.) and other crops to hostile climates in the tropics. The use of the accumulation concept, in which the relative rate of progress towards podding sums up to one is a common methodology. However, the lack of quantitative information, has resulted in poor decision making for crop management practices in relation to the time of optimum pod growth rate (Ropt). This study investigated modeling pod growth using an additive and interactive relation between pod growth rate, mean photoperiod, and temperature during the pod inductive phase. The field experiment was conducted at Ekpoma Nigeria. Ten bambara groundnut landraces from three different regions in Nigeria (Anyigba, Otukpo, and Nsukka) were sown on six dates from 15 June to 1 September during the successive growing seasons of 2010 to 2012, thus exposing the landraces to mean natural photoperiods of 12 h 23 min, 12 h 19 min, 12 h 14 min, 12 h 10 min, 12 h 5 min, 12 h, 11 h 55 min, 11 h 51 min, and 11 h 47 min during the pod inductive period. The observed optimum photoperiod and temperature forRoptwere 12 h and 26°C, respectively, for all landraces. Allocation to pod growth began at the critical photoperiod (Pc) of 12 h 19 min for Otukpo landraces, whereasPcfor Nsukka landraces was 12 h 14 min. However, thePcfor Anyigba landraces occurred earlier at 12 h 23 min. The pod growth model that was developed provided good predictions of pod growth for a natural range of photoperiods and temperatures.