Field experiments were conducted with the objective of developing a general New Mexico chile type plant (Capsicum annuum L.) phenological model as a function of heat units accumulated after planting (HUAP). Field experiments were conducted from 2003 through 2005 in the Sulfur Springs Valley of Arizona, near Sunsites in Cochise County, Arizona (31° 56" N, 109° 52" W, about 4,000 feet elevation) on a Borderline fine sandy loam (coarse-loamy, mixed, superactive thermic Typic Calcigypsids) and in the Animas Valley, New Mexico (31° 57" N, 109° 48" W, about 4,400 feet elevation), on a Vekol fine sandy clay loam (fine, mixed, thermic, Typic Haplargids). Plant measurements were collected routinely and important phenological stages that corresponded to first bloom, early bloom, peak bloom, physiological maturity, and red harvest were identified and recorded. Results indicate that within locations, all varieties performed similarly in relation to HU accumulation patterns. A general New Mexico chile type plant phenological model as a function of HUAP for all sites and varieties was obtained. First bloom occurred at 954 ± 254 HUAP, early bloom at 1349 ± 306 HUAP, peak bloom at 1810 ± 261 HUAP, physiological maturity at 2393 ± 215 HUAP, and red chile harvest was identified to occur at 3159 ± 220 HUAP. The purpose of this phenological baseline or model is to provide a crop management tool for growers for predicting and identifying critical stages of growth. Further development and validation of this model is a continued objective of this research program.

Field experiments were conducted in 2007 to evaluate a cantaloupe (Cucumis melo L.) plant development model as a function of heat units accumulated after planting (HUAP). Field experiments were conducted in 2007 in the Yuma Valley, Arizona (32° 42' N, 114° 42' W), about 150 feet (~ 32 m) elevation in four commercial cantaloupe fields managed by a cooperator-grower using four varieties. Plant measurements were made on regular 14-day intervals and the following growth stages were identified in relation to plant measurement data collection: pre-bloom, early fruit set, early netting, and physiological maturity (harvest). The model was evaluated by comparing the observed HUAP versus the predicted HUAP values using a repeated measures design. Mean differences within each sampling stage were separated using the Fishers’ protected least significance difference (LSD) test at P≤ 0.01. In addition, regression models were performed for all in-season data collected and the accuracy of the model was evaluated on the basis of the R² values with a specified level significance (α = 0.01). No statistical differences were found between the observed phenological data and the predicted values from the model throughout the study period. Also, the model presented an overall accuracy of 54 ± 37 HUAP (2 ± 1 day) in predicting cantaloupe-harvesting time. It can be concluded that the model can be used as a useful tool to assist cantaloupe growers in predicting and identifying critical stages of growth for irrigated spring cantaloupe crops in Arizona and the desert Southwest.