Chapter 3: Plant horticulture crops

Plant horticulture crops form a vital component of Kenya’s agricultural sector, contributing significantly to food security, income generation, and export earnings. The establishment of horticultural crops requires careful planning and management, including selection of appropriate inputs and planting methods. This chapter addresses the essential practices involved in establishing horticultural crops, focusing on inputs, planting techniques, and the comparative advantages of various methods suitable for Kenyan agricultural environments.

3.1 Horticulture crops establishment

Crop establishment is the stage from planting until the crop is growing well in the field, and the result is largely decided by the inputs that go into the soil and the method used to plant. A vegetable plot given the right fertiliser and manure, planted by a suitable method at the correct spacing, establishes evenly and reaches harvest on time. A plot with poor inputs or the wrong planting method shows gaps, uneven growth and low yields that cannot be corrected later. This topic describes the farm inputs used when establishing horticultural crops, the methods of planting them and the advantages and disadvantages of each method, so that an extension officer can advise a farmer on a choice that suits the crop, the soil and the money available.

3.1.1 Types of farm inputs

Farm inputs are the materials a farmer buys or produces and puts into the crop to prepare the land and grow it. In horticulture the main inputs at establishment are fertilisers, manures and planting materials, together with water, crop protection products and tools. Input quality and availability vary from one place to another, so the farmer must check where good products can be obtained and what they cost.

3.1.1.1 Inorganic fertilizer

Inorganic fertilisers are manufactured products that supply plant nutrients in a concentrated form that crops can take up quickly. They carry the nutrients nitrogen, phosphorus and potassium, which are shown on the bag as a ratio such as 17:17:17. The fertiliser to use and the amount depend on the crop, the soil and a soil test, and the recommendations of the extension officer should be followed.

• Straight fertilisers: These supply mainly one nutrient. Urea contains 46 per cent nitrogen and calcium ammonium nitrate (CAN) contains 26 per cent nitrogen, and both are used to feed the crop after planting.
• Phosphate fertilisers: Fertilisers such as DAP (18:46:0) are placed in the planting hole or furrow because phosphorus helps early root growth and moves little in the soil.
• Compound fertilisers: These carry two or more nutrients in one granule, for example NPK 17:17:17 for general use in vegetables.
• Basal and top-dressing application: A basal fertiliser is mixed with the soil at planting, and a top dressing is applied around the plants after they have established.
• Safe use: Mix basal fertiliser well with the soil so that it does not touch the seed, keep it away from the stem when top dressing, and store bags dry and closed.
• Soil test: A soil test shows which nutrients are lacking, so that money is not wasted on nutrients the soil already has.

3.1.1.2 Vegetative propagation materials

Vegetative propagation materials are the plant parts used instead of seed to establish a crop. They include cuttings, suckers, splits, crowns, slips, vines, tubers and grafted seedlings, and they are described in the topic on planting materials. At establishment, the farmer is concerned with their health, size and freshness. Material taken from healthy parent plants establishes quickly and gives a uniform crop, while material from diseased plants passes the disease on to the whole field.

• Source: Obtain material from a healthy, true-to-type parent or from a reputable nursery, and check for pests and disease symptoms.
• Freshness: Plant cuttings, vines and sweet potato slips soon after they are cut, because they dry out quickly. Pineapple crowns and slips are the exception: they are left in a shaded place for a few days so that the cut end heals before planting.
• Preparation: Trim and treat the material as recommended before planting, for example trimming and paring banana suckers.
• Planting depth: Plant at the depth and in the direction recommended for the crop, with the buds or nodes in the correct position.
• Watering: Water after planting and shade young material until it has rooted.

3.1.1.3 Manures

Manures are organic materials from animal and plant sources that add nutrients and improve the soil. They supply nitrogen, phosphorus and potassium in smaller amounts than fertilisers, but they also improve soil structure, increase water-holding capacity and feed soil organisms. Manures are particularly useful where the soil is low in organic matter.

• Farmyard manure: A mixture of animal dung and bedding from cattle, goats or sheep, applied after it has decomposed.
• Poultry manure: Rich in nutrients, but strong, so it is used in smaller amounts and well decomposed to avoid burning the roots.
• Compost: Plant residues and manure decomposed together into a dark, crumbly material that is safe to use at planting.
• Green manure: Fast-growing crops such as legumes that are dug into the soil while still green.
• Liquid manure: Manure steeped in water and diluted for use as a feed around the plants.
• Application: Spread and mix manure with the soil before planting or place it in planting holes, and use only well-rotted material, which avoids burning the roots and carrying weed seeds.

Other farm inputs for establishment

Besides fertilisers, manures and planting materials, a farmer needs quality seed, water, crop protection products and tools. Certified seed from a registered dealer has high germination and purity. Water is supplied by rain or irrigation equipment such as drip lines, sprinklers and storage tanks, and a steady supply is critical in dry areas. Crop protection products such as pesticides and fungicides must be used according to the label and with integrated pest management, which combines cultural, biological and chemical controls. Basic tools such as hoes, spades and dibbers are used for planting, and power tillers and seed planters help on larger farms.

3.1.2 Methods of planting horticulture crops

The planting method affects plant spacing, root development, the speed of establishment and the cost of the crop. The method is chosen for the crop, the seed size, the soil and the labour available, and the same farm may use several methods for different crops.

3.1.2.1 Direct seeding

Direct seeding is the sowing of seed straight into the field where the crop will grow and mature. It suits crops that do not transplant well or that have a short growing period, such as carrots, beetroot, peas and beans. It saves the labour and cost of a nursery. It needs a well-prepared seedbed, seed sown at the right depth (usually about two to three times the thickness of the seed) and timely sowing so that seedlings emerge evenly. Thin the seedlings after emergence to give the correct spacing.

3.1.2.2 Transplanting

Transplanting is the planting of seedlings raised in a nursery into the field when they are strong enough to survive. It is used for crops such as cabbage, tomato, kale, onion and capsicum. Seedlings are hardened by reducing water and increasing sunlight before moving, and they are lifted carefully with some soil on the roots. Transplanting is best done in the cooler part of the day or in cloudy weather, followed by watering, so that the seedlings recover quickly from the shock of moving.

3.1.2.3 Drilling

Drilling is the sowing of seed in a continuous, narrow line in a shallow furrow, either by hand or with a seed drill. The seeds are dropped thinly along the furrow and covered with soil. It is used for small seeds that need regular spacing and for crops that are thinned later, such as carrots and onions grown from seed, and for peas and beans. It saves seed compared with broadcasting and makes weeding and thinning easier.

3.1.2.4 Broadcasting

Broadcasting is the scattering of seed by hand over the surface of the prepared soil and covering it lightly with a rake or harrow. It is fast and needs little equipment, so it is used for cover crops, pasture and some leafy vegetables. Plant distribution is uneven, much seed is wasted and later weeding is difficult, so it is not suitable for high-value crops that need exact spacing.

3.1.2.5 Row planting

Row planting is the planting of seeds or seedlings in straight rows at a fixed spacing between the rows and between the plants in the row. The spacing is set by the crop and variety, and the rows are marked out with pegs and string. Row planting gives each plant enough space and light, makes weeding, spraying and harvesting easier and helps irrigation to be applied evenly. It is used for most vegetable crops such as tomatoes, cabbages and French beans and for fruit orchards.

Planting by cuttings and grafted plants

Crops such as sweet potato and many ornamentals are planted by cuttings or vines, and fruit trees such as avocado are planted as grafted seedlings. Cuttings allow quick multiplication of a chosen variety, and grafting joins a good fruiting variety to a strong rootstock that gives disease tolerance. Both need skilled handling and careful planting so that the cuttings do not dry up and the graft union is kept above the soil.

3.1.3 Advantages and disadvantages of various planting methods

Every method has trade-offs among cost, labour, plant performance and risk. The table compares them so that a farmer can match the method to the crop and the situation.

Chapter Summary

This chapter on plant horticulture crops covers the essential aspects of establishing horticultural farms, starting with the identification and use of various farm inputs such as inorganic fertilizers, vegetative propagation materials, and manures. It explains different planting methods including direct seeding, transplanting, drilling, broadcasting, and row planting, highlighting their respective procedures. The chapter also evaluates the advantages and disadvantages associated with each planting method to guide optimal crop establishment decisions. Additionally, it emphasizes the importance of accurate horticulture crop planting records, detailing how to prepare and maintain them for effective farm management. Practical steps for carrying out the establishment of different horticulture crops are provided to ensure successful crop production. Overall, the chapter equips learners with both theoretical knowledge and practical skills necessary for managing the establishment phase in horticulture.