Temperature and photoperiod sensitivity of development in five cultivars of maize (Zea mays L.) from emergence to tassel initiation

Abstract

Prediction of phenological development is crucial to the successful use of crop simulation in crop adaptation studies. Previous studies have shown existing predictive algorithms to be inadequate when applied to a broad range of cultivars and environments. The primary objective of the study was to quantify the temperature and photoperiod responses of the rates of development during emergence to tassel initiation (ETI) for a diverse set of maize cultivars. Five cultivars of maize, differing in maturity and adaptation, were sown on seven dates from 1 October 1993 to 29 March 1994 and grown under natural and extended (16.5 h) photoperiods at Gatton, Southeast Queensland, under non-limiting conditions of water and plant nutrient supplies. Timing of emergence and tassel initiation were observed for all treatments. The base, optimum, and maximum temperatures, and photoperiod sensitivity of each cultivar were determined using an iterative optimisation procedure. The critical photoperiod (12.5 h) was adopted from literature sources, as there was inadequate range in the short photoperiods in the present study to determine it with confidence. Photoperiod extension increased the duration of ETI and increased the number of leaves on all cultivars, the largest increases occurring in a tropically adapted cultivar (Barker), in five of the seven sowings. No response to photoperiod extension occurred in the crops sown on 24th February and 29th March 1994. The temperature response was the same in all cultivars, and was best described by a three-stage broken-stick linear function. Photoperiod sensitivity was linear at photoperiods in excess of 12.5 h. The optimised base, optimum and maximum temperatures were 8, 34 and 40°C respectively. Photoperiod sensitivity, expressed as the increase in number of leaves produced per hour of photoperiod in excess of 12.5 h, ranged from 0.3 to 1.5 leaves h−1. When expressed as the increase in thermal duration of the photoperiod-sensitive interval prior to tassel initiation, it was 5.0 to 27.3°C d h−1, (using the optimised base, optimum and maximum temperatures). The fitted values for the chronological duration of ETI were in close agreement (RMSD = 1.9 days) with the 57 observed values at Gatton, which spanned a range of 13–34 days. The optimised values for temperature and photoperiod responses should improve the prediction of tassel initiation in maize crop simulation models.