By Kyle Poling, Pioneer Field Agronomist
Crop scouting provides an opportunity to identify environmental stresses and evaluate effectiveness of management practices that impact yield. Being in your fields throughout the growing season can help in the detection and diagnosis of problems early so corrective action can be taken before major yield losses occur. Even though some issues cannot be fixed in the current year, regular scouting can identify management decisions that should be improved or changed for next year’s crop.
Plants cannot think or feel because they lack a brain or a nervous system; however, plants do have an extraordinary ability to respond to stimuli in their growing environment. If growing conditions are ideal, plants will thrive. Conversely, environmental stresses will cause normal plant development to be altered, often causing slow/stunted growth. Under extremely stressful conditions, plants may even die.
The primary factors that affect plant growth include: water, temperature, light, and nutrients. These four elements affect growth hormones in the plant, causing it to grow more quickly or more slowly. With a basic understanding of these factors, you will know how these factors affect plant growth and production of your crops. Either directly or indirectly, most plant problems are caused by environmental stress.
Water is the first ingredient in plant growth. It initiates germination of seeds and is the source of pressure to move roots through the soil. Water is a primary component of photosynthesis where plants harness energy from sunlight and produce simple sugars (carbohydrates) that are used to build all other plant parts. Plant size is controlled by water, as it helps increase cell size with turgor pressure and increase cell number through cell division. Water acts as a solvent to move resources such as nutrients and carbohydrates throughout the plant. On hot days, water controls transpiration that helps cool the plant.
Temperature is the primary factor affecting the rate of plant development. Warmer temperatures will cause plants to move quicker through growth stages. Increased temperature can also change a plant’s growth habit and appearance. When temperatures rise, plants grow taller and leaves become narrower and grow farther apart in order to cool themselves off. Grain yield can be significantly reduced if hot temperatures occur during the reproductive stages. Elevated nighttime temperatures can be especially detrimental on grain yield. Negative effects of high temperatures are increased during times of drought (water deficit) and flooding (excess soil moisture).
Light provides the energy necessary for plants to produce their own food through the process of photosynthesis (water and carbon dioxide are converted into carbohydrates and oxygen). The rate of this process is highly dependent on the light quantity. Cloudy days greatly decrease the amount of photosynthesis, which directly reduces the amount of carbohydrates produced. Less carbohydrates mean less energy available to grow vegetative material and produce grain. The length of uninterrupted darkness is critical for “short-day” crops, such as soybeans, to initiate flowering.
Nutrients are chemical elements needed for plant growth and functions. Plants combine the sugars they produce with plant nutrients to produce proteins, enzymes, and other elements essential to growth. A shortage or deficiency in any of the 17 essential nutrients will result in reduced or abnormal growth. Most of the nutrients a plant takes up are dissolved in water before being absorbed by the roots. In fact, 98% of nutrients are absorbed from the soil-water solution and only about 2% of nutrients are extracted from soil particles. Anything that reduces or stops sugar production in leaves can lower nutrient absorption. Thus, if a plant is under stress because of drought, reduced sunlight, or extreme temperatures, than nutrient deficiencies will very likely follow.
Plant appearance can provide clues that plant stress is impacting normal crop growth. Several of the most common symptoms that provide tips that something is not quite right with your crop include: leaf color, plant height, loss of leaf tissue, root growth (restricted, stunted, deformed), and wilting. Comparison of normal plants and abnormal plants in the same field can provide clues as to the cause of the stress impacting growth that is threatening your yield potential. Once the cause of stress has been determined, a course of action should be established to correct the current situation or prevent future struggles. This may include immediate applications of nutrients, fungicides/insecticides, or more long-term solutions such as tillage practice changes, improving drainage, or simply waiting for the next rainfall.