Landscape level heat accumulation and management of agrosystems

Landscape interactions among meteorological factors, cultural practices, and plant growth and development in commercial crop production were investigated. Plant performance data were collected over two growing seasons, plus some twenty meteorologic parameters. The logistic regression with binary response (growth stage completed, or not completed) and a series of single explanatory variables were used to rank effects of meteorological factors and their relative importance, at each of six stages of plant growth. Logit models evaluated likelihoods of successfully completing particular growth stages, in relation to cultural practices and climatic factors. Overall, temperature variables were most broadly influential, with soil moisture having significant secondary effects, in particular during crop maturity. A novel index, the accumulation of daylight degree-hours (incorporating variation in daylength), explained over 93% variance in phenology. It proved to be highly useful for predicting time to completion of individual growth stages. Studied plants accumulated 4800 to 14900 daylight degree-hours from seed germination through fruit maturity, depending on field location, planting time, cultural practices, and cultivar. Management intensity and other cultural elements significantly mitigated effects of climate on rate of plant development. The use of plastic mulch, raised beds, windbreaks, cultivar selection, and bee hives allowed for more efficient use of accumulated heat and apparent decrease in degree-days required for plant maturity. Application of plastic mulch over raised beds reduced the heat accumulation required for maturity by up to 25%. In contrast, use of high-yielding cultivars and irrigation systems significantly increased the heat needed for maturity. Results indicate that at landscape scale, meteorologic data, including estimates of daylight degree-hours, have potential as tools for large-scale prediction of plant performance, and evaluation of cultural practices.