Chapter 3: Plant annual crops

Planting annual crops requires a comprehensive understanding of the particular crop cycles, environmental conditions, and farm management practices suited to Kenya’s diverse agro-ecological zones. This chapter focuses on the essential aspects of establishing annual crops, which complete their life cycle within one year, making them central to food security and income generation for smallholder farmers and commercial enterprises alike. Mastery of farm inputs and their effective application is critical for optimizing yield and sustaining soil health in Kenya’s agricultural landscapes. Extension officers and agronomists play a vital role in advising farmers on selecting and managing these inputs to enhance productivity and sustainability.

3.1 Plant annual crops

Annual crops complete their life cycle, from seed to harvest, within a single year or season, unlike perennial crops, which live for several years. They include cereals such as maize and sorghum, legumes such as beans, oil crops such as sunflower, root crops such as Irish and sweet potatoes, and vegetables such as kale, 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 inputs described here are inorganic fertilisers, seed, vegetative propagation materials and manures. Choosing inputs means matching them to the crop, the soil and the farm budget, because soil fertility and pest pressure vary widely from farm to farm. 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. Nitrogen (N), phosphorus (P) and potassium (K) are the primary nutrients, needed in large quantities. Calcium, magnesium and sulphur are secondary nutrients, and elements such as zinc and boron are micronutrients, needed in small amounts but essential for crop development. 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, and it is sold in sealed, labelled packs. 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.
• Genetic purity and germination rate: Certified seed is free from mixtures, so the plants are true to type, and a high germination rate gives a better plant population. 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: Seed treatment with a fungicide or insecticide protects young seedlings from soil-borne diseases and pests, but 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, so that it keeps its viability and is not infested by pests such as grain weevils.

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

Water, products that protect the crop, labour and machinery are also farm inputs. They are used during crop management and are covered in the later topics of this unit.

Role of farm inputs in crop production

• Raising soil fertility: Fertilisers and manures replace the nutrients that crops remove.
• Establishing the crop: Certified seed and healthy planting material give even germination and vigorous plants.
• Improving the soil: Manures add organic matter, which improves soil structure and water holding.
• Matching inputs to the farm: Choosing the crop, variety and fertiliser rate to suit the soil, rainfall and budget avoids waste.
• Lowering disease risk: Clean seed and planting material from a reliable source carry less disease into the field.

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 fertilisers 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 covered the essential aspects of planting annual crops, beginning with an overview of the various types of farm inputs necessary for successful crop production. It detailed the roles of inorganic fertilizers, quality seeds, vegetative propagation materials, and manures in supporting crop growth. The chapter then explored different methods of planting annual crops, including direct seeding, transplanting, drilling, broadcasting, hill planting, and row planting, highlighting how each method is applied in practice. An analysis of the advantages and disadvantages of these planting methods provided insight into their suitability under different farming conditions. Furthermore, the chapter explained the importance of preparing accurate planting records to monitor crop establishment and management. Finally, it outlined the procedures involved in carrying out the establishment of annual crops, ensuring effective implementation from planting to early growth stages. This comprehensive approach equips learners with the knowledge to manage annual crop production efficiently.