Introduction to Seeds and Propagation
- Plant propagation occurs via sexual (seeds) and asexual (vegetative) methods.
- A seed is a mature, fertilized ovule and the reproductive unit of flowering plants.
- Seeds are essential for crop establishment and genetic diversity.
Seed Rate – Definition and Calculation
- Seed rate: Quantity of seed required per unit area for desired plant population.
- Depends on spacing, test weight, and germination percentage.
Seed Rate Formula:- Seed rate (kg/ha) = [Plant population/ha × Seeds/hill × Test weight (g) × 100] / [1000 × 1000 × Germination %]
Sowing Methods – Overview
- Common sowing methods: Broadcasting, Dibbling, Sowing behind plough, Drill sowing, Transplanting.
- Choice of method depends on crop type, seed size, and field conditions.
Broadcasting
Definition:- Randomly scattering seeds over the soil surface.
Features:- Suitable for small to medium seeds (e.g., sesame, sorghum).
- Easy, quick, and labor-saving; commonly used in India.
- Criss-cross sowing improves uniformity.
Disadvantages:- Uneven seed distribution and depth.
- Higher seed rate required.
- Lower germination and risk of lodging.
Dibbling (Line Sowing)
Definition:- Placing seeds in holes at specific depth and spacing.
Features:- Used for medium to large seeds (e.g., maize, cotton, sunflower).
- Practiced on ridges, furrows, or beds.
- Facilitates uniform population and better germination.
Advantages:- Reduced seed rate.
- Enables mechanization (weeding, harvesting).
Disadvantages:- Costlier and more time-consuming than broadcasting.
Sowing Behind the Plough
Definition:- Seeds dropped in furrows opened by plough, then covered by soil.
Features:- Manual or mechanical methods available.
- Ensures uniform depth and spacing.
- Suitable for crops like groundnut, redgram, cowpea.
Drill Sowing (Drilling)
Definition:- Dropping seeds at definite depth using sowing implements (seed drills).
Features:- Maintains uniform depth and population.
- Fertilizer application possible during sowing.
- Suitable for intercropping.
Disadvantages:- Requires more time, energy, and cost.
Transplanting
Definition:- Raising seedlings in nursery, then transplanting to main field.
Features:- Ensures optimum plant population and crop intensification.
- Nursery area is about 1/10th of total field area.
Disadvantages:- Labor-intensive and expensive.
- Transplanting shock may occur (5–7 days of slow growth).
Germination – Definition and Factors
Definition:- Process where radicle emerges from seed, initiating seedling growth.
Key Factors Affecting Germination:- Soil type, texture, structure, and microorganisms.
- Moisture availability and excess can cause rotting.
- Temperature: Optimum range required for each crop.
- Light: Red light (662 nm) promotes, far-red (730 nm) inhibits germination.
- Soil tilth and sowing depth (3–5 cm for most crops).
Crop Stand Establishment and Plant Population
- Good crop establishment ensures optimum plant population and yield.
- Plant population: Number of plants per unit area in the field.
- Optimum population maximizes yield per area; excess or deficit reduces yield.
Factors Affecting Plant Population – Genetic
- Plant size: Larger plants need wider spacing (e.g., cotton vs. rice).
- Elasticity: Indeterminate plants tolerate wider population range.
- Foraging area: Early soil cover maximizes sunlight interception.
- Dry matter partitioning: Higher density increases canopy and dry matter.
- Crop and variety: Population varies by crop and variety (e.g., rice, maize, cotton).
Factors Affecting Plant Population – Environmental
- Time of sowing: Weather, day length, and temperature affect population needs.
- Rainfall/irrigation: Lower population under rainfed, higher under irrigated conditions.
- Fertilizer application: High population utilizes nutrients better; low fertility limits yield at high density.
- Seed rate: Higher in broadcasting, lower in line sowing/transplanting.
Planting Geometry (Crop Geometry)
Definition:- Arrangement of plants in rows and columns to optimize resource use.
Types:- Random: Unequal spacing, common in broadcasting.
- Square: Equal spacing in both directions (e.g., coconut, banana).
- Rectangular: Rows wider than plant spacing; includes solid row, paired row, skip row.
- Triangular: Used for wide-spaced crops (e.g., coconut, mango).
Importance:- Ensures efficient use of light, water, nutrients, and space.
Summary
- Selection of appropriate seed rate and sowing method is crucial for crop establishment.
- Optimum plant population and geometry maximize yield and resource efficiency.
- Understanding genetic and environmental factors aids in effective crop management.