Factors that influence plant growth

We cannot control and know all the factors that influence plant growth. We know that by addressing the most limiting factor to plant growth, plants grow better and produce higher yields. If you suspect that your yields are lower or that you have less marketable yields the than your neighbour, you should have a look at the plant growth factors. Be careful with assumptions. Some factors are hidden, such as underground water tables. 

As we have said, there are many things we don’t know. Such as:

• What are all the growth factors?
• Do we know for sure all the aspects of the factors?
• Can the factors be controlled?
• What is the theoretical yield we can achieve?
• How do you know you have achieved the maximum yield with all the current factors?
• What is the most limiting factor on your farm?

Below are some of the essential growth factors. There are many more, but some are very technical and outside the scope of this article.

Genetic growth factors

Plants react to the environment according to their genetic makeup. The only way to change the genetic makeup on farm level is to choose different varieties or change the crop type. A geneticist can change the DNA through scientific breeding, and that takes many years to do. Small scale farmers practise micro breeding and selection throughout Africa. However, this is not done intentionally with a specific goal in mind. 

Thus genetic growth factors can only be changed by selecting different varieties and testing them each year. We recommend testing at least five different varieties at all times of the year over five years. It provides a good indication of the long term reaction of each variety to your specific environment and farming style. Choosing a variety based on one year’s evaluation is not good enough. 

Some varieties can only be grown in one season such as tomatoes. Others grow throughout the year, like spinach. Spinach must be tested in each season to see which one grows best during that time. 

Climate

The macro climate is influenced by:

• Season
• Seasonal fluctuations
• Mountain ranges around your farm
• Height above sea level
• Location on a continent
• The position of your farm relative to the equator. The closer to the equator, the higher the angle of the sun rays hit the plants, and the hotter the plant and surrounding area is. 

The microclimate is influenced by:

• The trees around your land. And each land can be different.
• The structure of the soil. Clods, for instance, get so hot in the sun they burn seedlings. 
• Type of soil. Sandy soils are warmer then organic-rich clay soils.
• The type of irrigation system. Drip and flood irrigated lands are warmer than lands with sprinkler irrigation systems. 
• Prevailing winds. Air movement due to mountains can either increase or decrease the temperature. Air movement increases water loss from plants, making them sensitive to soil moisture availability. 

Climate is the most important factor that influences plant growth. 95% of the sun’s radiation heats a plant. The plant must use energy to release the heat through water evaporation. A plant can only use 5% of the sun’s radiation for photosynthesis. As a general rule, if you are uncomfortable in the sun, so is your plants. Keep them well watered and cool. Some plants can tolerate high radiation and heat such as watermelon and sweet potatoes. If you are in a hot climate, make use of these crops. 

Plant processes that influence growth

There are many hidden chemical and physiological processes inside the plant which we cannot see. Each of these processes can have a limiting effect on plant growth. 

• Photosynthesis
• Permeability of cell membranes
• Water uptake
• Transpiration
• Ion uptake
• Enzyme activity
• Ion balance in the plant

The soil

We have discussed genetics, climate and factors inside the plant. The last area is the conditions inside the soil. Soil is a living organism. It changes the whole time. Bacteria break down organic material, changing the fertility of the soil within a season. We all know that compost does not last very long. 

Some clay’s expand and contract more than others. For instance, montmorillonite expands so much that large cracks appear when it dries out. So the soil moves during a growing season, and it affects the root development. 

A light coloured sandy soil is cooler than dark coloured clay soil. This affects that temperature in the leaf canopy which influences transpiration (water use) and growth. Too high temperatures and the plant wills tress, lowering yields. Too low temperature will affect plant growth and lower yields. In some cases, higher temperatures due to dark coloured soils increase yields in winter.

How can a grower manage plant growth

In open-field farming, the grower is quite limited. There are more opportunities to control the environment in a greenhouse and soilless cultures. It does not mean a farmer should do nothing. If you do more than your competitors, you have the edge. Only 2.5% of growers try to optimise their farming operation, especially if they are small scale farmers.  

The fact that you read this article and got this far puts you in a different farmer segment. 

You cannot change the climate, but you can control the micro-climate to an extent. Only 2.5% of growers try to optimise their farming operation, especially if they are small scale farmers.

• You can use the climate to your advantage by planting crops and varieties that are suitable and grow well in your environment. 
• You have control over the amount, time and type of fertiliser applications. Make sure you apply the right amount. Too much cost money and lowers the yield. Both effects reduce profits. 
• Irrigate wisely. You might have to irrigate in the middle of the day to cool the plants down. Sprinkler irrigation at night increases the risk of leaf diseases. 
• Manage your weeds properly. Weeds compete for valuable nutrients and water. Produce contaminated with weeds reduce the price paid, making your farming operation less profitable.
• Know your weeds. There are some plants (not weeds) that attract predator insects. They reduce the cost of pesticides — plant companion plants along roads and walkways and around buildings. Some weeds attract pests away from your valuable crop saving cost of spraying.
• Watch the weather. It might sound silly, but rain is like irrigation. If you irrigate today and it rains the same evening, that is a double dose of water. Too much water leaches out valuable nutrients and causes waterlogging. Rain is free, and irrigation water is expensive. The more you use the irrigation system, the higher the maintenance cost. So you have to add the fuel cost and maintenance and shorter life span of your equipment to your calculations. 
• Apply intercropping. There are many advantages to this system, especially for small scale farmers. 
• Small scale farmers are not a threat to large commercial growers. Make friends and learn from them. Big successful people like talking about themselves and how good they are doing. Use it to your advantage. 

I am sure you can think of many more tips to improve crop growth, increase marketable yield and reduce cost. 

Cover Photo by Engin Akyurt from Pexels