Land preparation starts with removal of shrubs and stumps from rice fields. The land is then ploughed using hand hoes such as jembe/panga, oxen or tractors. Power and equipment are required for tillage in different soil types are varied. It is essential to plough when land is dry to reduce weeds. However in difficult soils such as virgin lands there may be need to wet the field before ploughing. It is generally recommended that two ploughs and one harrow or rotovation are sufficient for soil disturbance long before planting to establish a fine tilth. Fine tilth improves germination reduces seeding rate and improves seedling uptake in irrigated ecologies. Ensure soil surface is level to enhance water application by irrigation. The field requires adequate drainage system to allow rapid removal of excess water. However, land preparation will vary according to cropping system used. Three main rice ecologies (Irrigated, Rainfed lowland and Rainfed Upland) require different land preparation techniques.
Land preparation in irrigated paddy fields is normally carried out after bunding and flooding. This ensures that the fields are wet enough to allow ploughing and strong enough to give reasonable levels of traction or grip to the tractor. This is essential for the soil to attain reasonable depth of 15 cm, kill weeds by burying and exposing their roots, prevent erosion and encourage water accumulation. Land preparation is laborious and the drudgery takes some 25 days to prepare using oxen. Mechanization is normally the best alternative, however manual land preparation is predominately practiced among small holder farmers. The second operation is carried out in the irrigated paddies to reduce clog sizes, weed control, and incorporate fertilizers in the soil and puddling. Conventional tillage is done using mould board ploughs, discs and rotary tillers for larger fields and thereafter are manually removed from fields.
Rainfed Lowland Ecologies
In this ecology land should be ploughed and harrowed to a fine tilth before rains.
Rainfed Upland Ecologies
Land preparation in upland ecologies is carried out where crops are grown in aerated conditions without standing water. Upland fields must be ploughed at least twice and harrowed ones to attain the required fine tilth for good germination, good seedling emergence, good and early growth vigour (i.e. stand establishment and good uniform growth). This makes land preparation to closely relate to methods of planting and available moisture. Land preparation in upland ecologies help reduce weeds, incorporation of fertilizers, increased soil porosity and aeration of the soils. Early land preparation allows soil to settle, catalyzes decomposition of organic matter and reduces plant debris.
LevelingIn all ecologies land preparation ends up with final operation that adequately levels the field. Levelling is done to ensure fair distribution of water across the field.
• Leads to proper crop management and water management
• Weed control
• Affect Plant density
• Pest and disease control
• Yield and quality maximization
Land Preparation and leveling therefore:-
- • Improves and restore soil fertility
• Ensures proper aeration and good root penetration
• Proper land levelling
• Improves soil workability
• Improves nutrient uptake by crops
• Prevents accumulation of salts near soil surface
• Improve structure and nutrient status of the soil