Chapter 3: Plant annual crops

Planting annual crops is a fundamental activity in Kenya's agricultural sector, especially for extension professionals who guide smallholder and commercial farmers. Annual crops complete their life cycle within one growing season, making their management critical for food security and income generation. This chapter focuses on understanding annual crop production, starting with the essential inputs required to establish and sustain productive farms. Knowledge of farm inputs enables extension officers to advise farmers on efficient resource use and improve crop yields.

3.1 Plant annual crops

Annual crops complete their life cycle, from seed to harvest, within a single year or season. They include cereals such as maize and sorghum, legumes such as beans and soya beans, oil crops such as sunflower, root crops such as Irish and sweet potatoes, and vegetables such as tomatoes and cabbages. Because the crop lives for only one season, everything it needs must be in place at planting: a prepared seedbed, good planting material and the right inputs in the right amounts. This topic introduces the farm inputs that are brought to the field at planting; the methods of placing seed and plants in the soil follow in the topics after it.

3.1.1 Types of farm inputs

Farm inputs are the materials, resources and services applied in crop production to raise the quantity and quality of the harvest. The main inputs for annual crops are fertilisers and manures to supply nutrients, seed or vegetative material to establish the crop, chemicals and biological products to protect it, water, and labour and machinery. Choosing inputs means matching them to the crop, the soil and the farm budget. A farmer who applies the wrong fertiliser, or too much of it, wastes money and may damage the crop or the soil.

3.1.1.1 Inorganic fertilizers

Inorganic fertilisers are manufactured or mined products that supply plant nutrients in concentrated, soluble form, so that crops absorb them quickly. A fertiliser bag shows the nutrient content as a grade: the percentages of nitrogen (N), phosphate (P2O5) and potash (K2O). Straight fertilisers carry one main nutrient, and compound fertilisers carry two or more.

To find how much nutrient a bag supplies, multiply the bag mass by the percentage and divide by 100. For a 50 kg bag of DAP: nitrogen = 50 × 18 ÷ 100 = 9 kg, and phosphate = 50 × 46 ÷ 100 = 23 kg. For a 50 kg bag of urea: nitrogen = 50 × 46 ÷ 100 = 23 kg.

Fertilisers act fast and give a measurable response when a nutrient is lacking, but they do not add organic matter, and heavy use of some types can acidify the soil. Apply the amounts recommended from a soil test or by the local extension officer, keep the fertiliser from touching the seed, because it can scorch it, and store bags dry, closed and off the floor, away from seed and food. Buy from a registered agro-dealer and check that the bag is sealed and labelled. Methods and timing of applying fertiliser are covered under Fertilizer application.

3.1.1.2 Seeds

Seed is a key input, because other inputs only pay if the seed germinates and produces a healthy plant. Certified seed has been produced and inspected under the seed certification system, so its variety, purity and germination meet the required standards. When choosing seed, consider:

• Variety: Use a variety recommended for the altitude, rainfall and market of the area, with the maturity period that fits the length of the growing season. Improved varieties are bred for yield, disease resistance and drought tolerance, and many are released by KALRO.
• Type: Hybrid maize seed gives high yield but is bought afresh each season. Open-pollinated varieties and most bean varieties can be saved and replanted, as explained under Obtain planting materials.
• Quality: Buy certified seed in a sealed, labelled pack, and check that the seed is clean, plump and free from damage.
• Seed rate: The amount of seed needed depends on the crop, the spacing and the germination percentage, and is found in the variety's recommendations.
• Treatment and storage: Treated seed is poisonous and must not be fed to livestock or eaten. Store seed in a cool, dry place away from fertilisers and chemicals.

The types of planting material, including seed and seedlings, are described under Obtain planting materials.

3.1.1.3 Vegetative propagation materials

Vegetative propagation materials are plant parts used instead of seed for crops that are planted from cuttings, vines, tubers or suckers, such as cassava, sweet potato, Irish potato and banana. As inputs they have to be planned, bought and handled like seed: the farmer calculates how many pieces are needed for the plot at the chosen spacing, orders them from a reliable source, and plants them quickly. Material from a clean source gives a healthy crop; material from infected plants carries disease forward. Because vegetative material is bulky and perishable, it is more costly to transport and store than seed, and it should be kept cool, shaded and moist until planting. The different forms and how to obtain them are explained under Obtain planting materials.

3.1.1.4 Manures

Manures are organic materials from animals or plants that are added to the soil to improve fertility and soil condition. They release nutrients slowly and add organic matter, which improves structure, water holding and the activity of soil organisms.

• Farmyard manure: A mixture of dung, urine and bedding from the cattle boma or goat pen. It is best used when well rotted, because fresh manure can burn roots and bring weeds.
• Poultry manure: Richer in nutrients than cattle manure, so it is applied in smaller amounts and must be well rotted.
• Compost: Made by heaping crop residues, weeds and animal dung and allowing them to decompose. It is ready when dark, crumbly and earthy-smelling.
• Green manure: A fast-growing crop, such as sunn hemp or lablab, ploughed into the soil while still green and soft to add organic matter and, in the case of legumes, nitrogen.
• Liquid manure: A diluted extract of manure or leaves steeped in water, applied around plants as a quick nutrient supply.

Manure is applied to the seedbed and mixed in before planting, or placed in the planting hole and mixed with the soil. Because its nutrient content varies, manure is often combined with a lower rate of inorganic fertiliser to give better results than either alone.

Other farm inputs

• Pesticides and herbicides: Chemicals that control pests, diseases and weeds. Use only products registered by the Pest Control Products Board, follow the label on dose and waiting periods, and wear protective clothing.
• Biological inputs: Rhizobium inoculants applied to legume seed help the plants fix nitrogen, and biopesticides use natural organisms or extracts to control pests.
• Water: Irrigation water supplements rainfall in dry areas and during dry spells. Drip kits and water harvesting structures use it efficiently.
• Labour and machinery: People, oxen, tractors and planters carry out land preparation, planting and other work on time.

Role of farm inputs in crop production

• Raising soil fertility: Fertilisers and manures replace the nutrients that crops remove.
• Protecting the crop: Pesticides and good pest management reduce losses.
• Establishing the crop: Certified seed and healthy planting material give even germination and vigorous plants.
• Saving water: Irrigation and water conservation inputs stabilise yields when rain is poor.
• Saving labour and time: Machinery and improved tools allow planting and harvesting at the best time.

Challenges in obtaining and using farm inputs

• High cost: Fertilisers and improved seed are expensive for many smallholders, especially in the planting season when demand is high.
• Poor quality or fake products: Substandard or counterfeit seed and chemicals reduce yields, so buy only from registered agro-dealers and check seals and labels.
• Limited knowledge: Without extension advice, farmers may apply too little or too much.
• Lack of credit: Delays in getting finance prevent timely purchase of inputs.
• Poor supply and distribution: Remote areas may have delays or shortages because of poor roads and few stockists.

Chapter Summary

This chapter on planting annual crops covers the essential types of farm inputs including inorganic fertilizers, seeds, vegetative propagation materials, and manures, each playing a critical role in crop establishment and growth. Various methods of planting annual crops are detailed, such as direct seeding, transplanting, drilling, broadcasting, hill planting, and row planting, highlighting their distinct procedures and applications. The chapter further explores the advantages and disadvantages associated with each planting method, providing a balanced understanding to inform practical decisions on the farm. It emphasizes the importance of preparing comprehensive planting records to monitor crop progress and manage resources effectively. Finally, the chapter guides the practical steps involved in establishing annual crops, ensuring that students can apply theoretical knowledge in real agricultural settings. This holistic approach equips learners with the foundational skills necessary for successful annual crop production.