AGRI 103: Agronomy - Plant Growth and Development pt. 2/2 lecture 7

AGRI 103: Agronomy - Plant Growth and Development

Growth Habits

  • Determinant:

    • Defined as plants with a finite growth period during which a plant reaches a predetermined size or height.

    • Typically, determinant plants produce all their fruit at once.

    • Example: Wheat.

  • Indeterminate:

    • Refers to plants that experience continuous growth throughout their life cycle.

    • They may produce fruit and foliage simultaneously.

    • Example: Lentil.

  • Semi-determinate:

    • Represents a growth habit that is intermediary between determinant and indeterminate.

    • Example: Canola.

  • Varieties with Mixed Habits:

    • Many crops or plants possess varieties that may showcase either determinant or indeterminate growth habits.

    • Examples include: Chickpeas, Tomatoes, Beans.

Specific Crop Growth Habits

  • Dry Beans Seeding:

    • Lentil plants exhibit an indeterminate growth habit, continuously flowering until they face stress factors such as:

    • Lack of moisture

    • High temperatures

    • Nutrient deficiency

    • This information is supported by Saskatchewan Pulse Growers (SaskPulse).

Tomato Types

  • Determinate Tomatoes:

    • Grow to a specific (determined) height.

    • Exhibit bushy growth.

    • Produce fruit that ripens all at once.

    • Typically require cage support.

    • Ideal for large batch cooking or preserves.

  • Indeterminate Tomatoes:

    • Grow to an indetermined height.

    • Have vine growth habits.

    • Produce fruit that ripens throughout the season.

    • Require trellis support.

    • Best for fresh, weekly harvests.

Crop Development and Management

  • Importance of Crop Stages:

    • Farmers and agronomists utilize various crop stages to describe crop development, which serves as a guide for applying management treatments. These treatments include:

    • Application of fertilizers

    • Application of pesticides

    • Application of plant growth regulators (PGRs)

    • Irrigation

    • Timing of swathing, desiccation, or harvest.

  • Pesticide Application Considerations:

    • Certain pesticides must be applied at specific crop development stages to minimize damage to the crop.

    • Identification of crop susceptibility to pests is critical, as crops are more vulnerable at specific developmental stages, making timely applications essential for effectiveness.

  • Plant Growth Regulation and Maturity:

    • Effective application of PGRs is stage-dependent. Plants must reach the proper stage of maturity before termination to maximize yield.

  • Nutrient Concentration Variability:

    • Crops display varying nutrient concentrations and requirements (both water and nutrients) contingent on their developmental stage.

Growing Degree Days (GDD)

  • Definition:

    • GDD is an index of heat accumulation, also referred to as heat units, over time.

  • Temperature Influence:

    • Temperature serves as a primary determinant of the growth rate and development of plants.

  • Estimation of Crop Development:

    • GDDs facilitate the estimation of crop development speed, helping predict when specific developmental stages will occur.

  • Calculation of GDD:
    The formula for calculating GDD is as follows:

    • The base temperature varies with each crop; it is the temperature above which growth occurs (for instance, (0°C)(0°C) for wheat).

  • Accumulation of GDD:

    • GDDs for each day since the start of the season (or since seeding) accumulate to provide a total GDD measure.

GDD Examples

  • Total GDD accumulation in Moose Jaw from 2019 to 2022 outlines the variability and trends in seasonal temperatures and plant growth.

  • Early-season varieties of crops will require fewer heat units to reach maturation compared to longer-season varieties.

  • Different varieties within a crop species showcase unique heat unit requirements for reaching each developmental stage.

Crop Developmental Stages

  • Identification Systems:

    • Various systems and scales have been developed to identify specific developmental stages of crops, such as:

    • Feekes Scale

    • Zadoks Scale

    • Haun Scale (for cereals, numerical)

  • Stage Classification:

    • Crops, such as soybeans and corn, can be classified into vegetative (V) and reproductive (R) stages.

  • Reading Assignment Reference:

    • Students are expected to consult the "Crop Diagnostic Handbook 2022 – SK Ministry of Agriculture, Section 1 General Agronomy – p. 3-18 (Plant Staging)" as this material will be testable.