Understanding phenology: a guide to agricultural success
Soil, water, nutrients, diseases, and pests are some of the key factors that determine the success of a crop. However, one of the most critical aspects that often doesn’t receive enough attention is the selection of the crop variety and planting time.
The importance of variety selection and planting time
The choice of the right variety and the correct planting time can significantly influence the overall health and yield of your garden or farm. It’s not just about planting any seed at any time; it’s about understanding the specific adaptations and cycles of each plant variety.
Understanding phenology
In the absence of stressors such as drought or diseases, plants go through a gradual development with a well-defined sequence of events. This development can vary significantly between species. For instance, some plants produce flowers before leaves each year, while others first show their leaves and then bloom. This sequence of developmental phases is known as phenology.
Phenology refers to the study of periodic plant and animal life cycle events and how these are influenced by seasonal and interannual variations in climate. Each plant follows a specific biological clock, which progresses based on the accumulated heat in the environment.
In the northern emisphere as spring begins, plant growth is slow but tends to accelerate as we approach summer. The duration of a plant’s growth cycle thus varies with the specific temperatures of a given year.
Measuring heat accumulation: growing degree days
The concept of growing degree days (GDD), was introduced by René de Réaumur in the 1700s. This model is still widely used in agricultural sciences to predict the number of days needed for germination, flowering, and crop maturity. It’s also used to predict the development of other organisms like insects and fungal pathogens.
Degree days are estimated using various methods, starting from the daily maximum and minimum temperatures. The simplest estimation involves subtracting the plant’s minimum growth temperature, known as the base temperature ($T^\circ_{base}$), from the average daily temperature.
$$ GDD (day) = \frac{T^\circ_{max} + T^\circ_{min}}{2} - T^\circ_{base} $$
The base temperature varies for each species and can even differ among varieties. The maximum temperature is often capped at 30 °C, beyond which a plant stops accumulating optimal degree days.
So, for example, if we assume that the $T^\circ_{base}$ of a tomato is 12 °C, and the minimum an maximum temperature in a given were 15 and 25 °C, respectively, then that day the plant will have accumulated:
$$ \frac{25 + 15}{2} - 12 = 8\ GDD $$
eight growing degrees day.
This degree day model is very simplistic; however, more complex models consider factors like optimal growth temperature, water availability, and photoperiod, which can further modulate plant phenology.
Choosing the right variety
Each plant variety requires a specific total number of degree days to reach each phenological stage.
So, how we can leverage this knowledge to choose which varieties to grow and when to plant them? Literature is rich with research estimating the growth temperatures of different species and varieties. Alongside this, temperature data from your cultivation location is essential.
If you don’t have access to a personal weather station, there are many public weather data sources available. With the necessary information, you can use digital tools to estimate the periods of different phenological phases.
Application in crop planning
This knowledge is crucial for understanding how well a plant suits your cultivation area and for organizing seeding and transplanting schedules.
Selecting the right crop variety and knowing its growth cycle are vital for a successful crop. By understanding phenology and degree days, farmers and gardeners can make informed decisions, leading to healthier plants and more abundant harvests.
At Mater, we’ve developed a user-friendly tool that can download weather data from open APIs and calculate the suitability and ideal sowing window for different crops at selected coordinates. It simplifies the process of matching crop varieties with local climate conditions, ensuring that you plant the right crop at the right time. Using this tool, you can make data-driven decisions, optimizing your agricultural efforts for maximum efficiency and yield.
Stay tuned as we’ll make this tool available very soon.