planting

Planting refers to the placement of a seed, plant, or bulb in the ground so that it can grow. Several cultural practices are performed in order to ensure the successful planting and growth of the plant.

Learning Objectives

By the end of this lesson, you should be able to:

• Describe the different methods of preparation of planting materials.
• Explain the different methods of planting.
• Describe plant population
• Describe spacing in planting
• Describe seed rate

Preparation of planting materials

I. Breaking seed dormancy 

Some seeds undergo a dormancy period between maturity and the time they sprout. Seed dormancy refers to the period when a viable seed is inactive and cannot germinate, even under favorable climatic conditions. It should be broken before the seed is planted.

Methods of breaking seed dormancy

• Soaking in water
• Heat treatment, for example, through roasting, slight burning, or boiling.
• Scratching the seed coat to make it permeable to water. 
• Washing or removing the mucilage.
• Chemical treatment, for example, through the use of sulfuric acid or potassium nitrate.
• Storing the seeds over a given period of time or pre-conditioning the seeds.

II. Seed Dressing

Seeds are coated with fungicides or an insecticide or a combination of the two chemicals. The chemicals protect the seedlings from soil-borne diseases and pests. This is particularly common with cereals, sugarcane, and legumes. 

III. Seed inoculation

This is the practice of introducing a high number of nitrogen-fixing bacteria (Rhizobium) on the surface of legume seeds prior to planting. It is done to promote nitrogen fixation in legume crops. Seed inoculation results in increased formation of nodules in the roots.

In areas where soils are deficient in nitrogen, legumes such as beans, clovers, and peas should be coated with an inoculant. An inoculant is a preparation that contains the right strain of Rhizobium depending on the type of legume and encourages nodulation, hence nitrogen fixation.

IV. Chitting

This is the induction of sprouting in potato seeds, tubers, or sets. Sprouting of tubers under light produces short, tough, green sprouts.  Green sprouting or chitting enhances emergence, tuber formation, vine size, and earlier maturation by as much as two weeks. It helps maximum utilization of rain and nitrogen flush and leads to higher yield. 

V. Planting

Planting is the placement of a seed, bulb, or plant in the ground in order for it to grow. There are several factors to consider when determining the time for planting a crop. These factors include:

• Water availability or rainfall patterns. It is important to plant during a rainy season or in areas with adequate water to support the plants. Most plants need water, during and after planting.
• Type of the crop or growth habit of the crop. Different crops are planted in different seasons. Some do well in dry seasons, others in wet.
• Purpose of the crop. For example, You can plant corn for human consumption or use it as fodder for animals. Always consider the purpose of the crop when determining the time of planting.
• Expected harvesting time in light of market demand. If you are planting to sell on maturity, you must consider the demand market. Time your planting such that you harvest when market demand is high.
• Prevalence of diseases, pests, and other adverse environmental conditions. Different diseases and pests do best under certain conditions. For example, many fungal diseases are prevalent during cold seasons. Consider this while timing your planting, such that your plant escapes periods of pests and diseases most prevalent to the plant.

Methods of planting

There are four main methods of planting. 

• Broadcasting: Seeds are randomly spread by hand on a small scale or by tractors on a large scale. It is common with pasture seeds which are very tiny. 
• Row planting: These involve seeds being planted in straight lines with spaces between them.
• Undersowing: This is the establishment of pasture under an already existing growing crop. The existing crop can be a nurse or a main crop like maize. Under sowing is mainly practiced in highly productive areas where soils are fertile and rainfall is adequate.
• Oversowing: This refers to the establishment of a pasture legume or grass in an existing grass pasture.

Plant population

This is the number of crops per unit area, for example, per hectare. It is calculated using the formula:

Plant population = (area of land/spacing of the crop) x number of seeds per hole

The correct plant population is important as it leads to high yields and high-quality produce.

Spacing

Spacing refers to the distance between plants and between rows.

Factors that determine the spacing of a crop

• Soil fertility: Seeds are spaced closer if the soil is fertile and wider if the soil is infertile.
• Soil moisture content: Seeds are spaced wider in drier areas as compared to wet areas. 
• The intended purpose of the crop: For instance, maize grown for silage is spaced closer than that grown for grain production.
• Machinery to be used in subsequent farm operations: A crop whose operations will be mechanized is spaced wider to allow space for machinery, than that which will be manually managed.
• Growth habit of the crop: Plants that litter or produce suckers will tend to occupy a bigger area, and thus require a wider spacing than those that do not produce suckers.
• Prevalence of certain pests and diseases: Aphids and groundnut rosettes, for example, are controlled through closer spacing. Aphids mobility is reduced when groundnuts are closely spaced.
• Cropping system: A wider spacing is required for a crop that is to be inter-planted than in a pure stand.
• Height of the crop: Shorter crops require narrower spacing than taller crops.
• The number of seeds per hole: If many seeds are planted per hole, the spacing should be wider than if a few or one seed is planted per hole.

Seed rate

The seed rate is the quantity of seed of a crop that is required to sow a unit area of land for optimum crop production.

Importance of determining seed rate 

• To maintain optimum plant population in the field for higher yield harvest. 
• To prevent seed wastage from excess sowing such that it reduces the initial cost of production. 
• To know the quantity of seed needed for sowing in advance
• To ensure the quality of crop production

The factors to consider when determining the seed rate for a given crop include:

• Germination potential of the seed. Seeds with a high germination potential should be well spaced. Those with a lower germination potential have narrower spacing- a higher seed rate.
• Purpose of the crop. Crops grown for fodder can be closely spaced thus a lower seed rate.
• Growth habit of the crop. Plants that grow laterally and produce a lot of branches need to be spaced out, therefore, a lower seed rate.
• Size of the seed. The seed rate of large seeds should be lower than that of small seeds.

Planting depth

When planting a seed, it is crucial to properly determine the appropriate depth in order to enhance the plant’s chances of properly developing. Setting a seed in the correct depth has also been shown to drastically increase the plant’s germination rate while helping it develop into a proper seedling. The exact planting depth normally depends on the individual plant.

General guidelines for planting depth are: 

• Seeds should be planted at a depth of two times the width, or diameter of the seed. 
• For tiny seeds, place them on the surface of the soil and barely cover them with soil. 
• Don't compress the soil atop the seeds as you plant them. The soil should be firm but not compacted.

The factors that determine the depth at which seeds should be planted include:

• Soil type. In compacted soils like clay, you should plant your seeds shallow. This is to make sure the seed germinates and is able to emerge from the well-compacted soil. In loose soils like sand, you should plant the seed deeper to provide enough cover.
• Seed size. Large seeds are planted deeper to provide enough contact with the soil. Small seeds should be planted shallow to allow their emergence from the soil during germination.
• Soil moisture content. Seeds should be planted deeper in dry soils than in wet soils. This is done to give enough time to the seed to imbibe water and initiate the process of germination.
• Type of germination of the seed. Seeds like beans with epigeal germinations are planted shallower compared to seeds like maize seeds with hypogeal germinations. Hypogeal germination happens below the ground while epigeal germination happens above the ground.