07/08/2013 Soil Unit 22175 and Plant Identification Unit 20574

Actual Temperature
14 degrees Celsius
Humidity : 85%
Rainfall : 0.00mm
Wind : Calm

In the morning section class was with Lisa Short on Soil Unit on Soil Organism. A living soil is full of organisms belonging to the plant and animal kingdoms. There are many different groups of soil organisms ranging from rabbit to bacteria. The total population of soil organisms is referred to as the soil biomass. 

• Large Animals Macro-fauna eg. rabbit may cause some erosion but generally have little effect on the soil.
• Smaller Animals Meso-fauna e.g.. earthworm, insects, mites, molluscs, nematodes worms are important for breaking down organic matter, mixing soils and forming aggregates.
• Smallest eg bacteria, fungi, algae, protozoa are very important for maintaining soil fertility.

Nitrogen Fixation 

78% of air is nitrogen, but plants cannon use this nitrogen until is has been converted into ammonium or nitrate. Nitrogen fixation is the conversion of gaseous nitrogen from the air into forms that can be used by plants. The best-known example of nitrogen-fixing micro-organisms that live in association with plants in New Zealand is rhizobial bacteria. These penetrate the roots of host plants such as clovers or lucerne when they form small bumps. 

The amount of nutrients that plants can obtain from the soil depends on :

• the soil type and the material from which the soil was formed
• the physical conditions in the soil
• the temperature and the water content of the soil, and hence the weather
• reactions between plant nutrients and soil particles
• soil acidity
• the amount and nature of organic matter in the soil and the activity of micro-organisms
• the amount and type of fertilisers that have been applied in the past
• the presence of pests, diseases and toxins
• the balance between the amount of nutrients present
• the plants species and their stage of growth
• competition for nutrients between the plants, soil organisms, leaching and gaseous losses.

The  amount of nitrogen fixed is also controlled by the amount of plant available mineral nitrogen already in the soil.

In the afternoon session was Plant Identification Unit also with Lisa Short. She explained and discussed about the Assessment questions and took all of us to opposite O Block to show all kinds of weeds and later to Botanical Garden regarding trees and shrubs.  Class adjourned at 3.00pm.