Sustainable Land and Resource Management Elective

Sustainable Land and Resource Management Elective

1.  Processes in agricultural systems

Applying the Australian land capabilities system to the local area in order to compare existing land use to that suggested by a land capability assessment, to ensure sustainable land use

Symbol / Land type / Needs
I / Very rare and very fertile / No special needs
II / Nearly flat, fertile cropland / Up to 4 crops in 10 years within minimum tillage and pasture in other years to prevent soil damage
III / Fertile, sloping cropland / Up to 4 crops in 10 years within minimum tillage and pasture in other years and contour banks to stop runoff to prevent soil damage
IV / Good grazing land but too fragile for regular crops / Up to 2 crops in 10 years with minimum tillage to improve pastures. Keep pasture taller than 5cm
V / Fragile, grazing land / Up to 2 crops in 10 years with minimum tillage to improve pastures as well as contour banks to stop runoff. May need more lime or fertiliser. Keep pasture taller than 5cm
VI / Very fragile grazing land
No cultivation / Improve pasture by broadcasting seed and fertilisers. Limit tree clearing to 50% cover. Keep pasture taller than 8cm
VII / Too fragile for grazing
Keep trees for seed, honey or wood / Reduce fuels to save fire damage, ask before clearing any trees and control pests
VIII / Non-farming scenic woodland or wetland farm Holiday or bushwalking / No disturbance of natural bushland

Discussing the effects of soil degradation on agricultural productivity and sustainability

·  Land degradation results in loss of farm productivity and profitability

·  It costs about $1500 million annually in lost production

·  Impacts of land degradation reach beyond their source and into wider environments

·  Solutions need to be invested so that costs of land degradation are spread throughout whole community

·  Forms of degradation include soil erosion, Dryland salinity, irrigation salinity, soil acidification and soil structure decline – these forms reduce the quality and quantity of soil for agricultural production

Land degradation / Effects
Erosion / Wind Erosion – loss of fine particles leaves only larger particles which affect soil nutrient levels and its ability to retain moisture for plant growth. Can remove soil from bare areas to planted areas which buries plants and reduces yield or can bury fences or knock them down
Sheet and Rill Erosion – occur mainly on sloping land where there is insufficient groundcover. Rill and sheet erosion contribute to declining land productivity by removing layer of top soil (which contains higher proportions of nutrients and OM)
Gully Erosion – a problem as: it removes more fertile topsoil layers; contributes to sedimentation of creeks, rivers and water supplies; discolours and contaminates water caused by clay materials carried in suspension; lowers water table; forms pathways for removal of sediments of adjacent areas; reduces area of arable land dividing it into smaller parcels thus increasing the cost of farming operations;
Destroying public facilities (i.e. roads) by undercutting or burying
Dryland Salinity / Salts become concentrated in patches causing death of existing vegetation (salt stops osmosis which is needed to get water and nutrients) and formation of bare areas (which usually erode) – salt crystals can be observed on these bare areas and grazing salt congregate to lick salt crystals and their trampling aggravates erosion. Soil structure can break down, becoming loose and prone to erosion. Soil may become water logged and poorly aerated. Salt damages infrastructure (i.e. through rusting)
Irrigation Salinity / Salt is accumulated at or near the surface of soil, killing or stunting trees, crops, pastures and reducing yields (salt stops osmosis which is needed to get water and nutrients) Crops vary in tolerance to salt concentration. Soil structure can break down, becoming loose and crumbly and prone to erosion. Soil may become water logged and poorly aerated. Salt damages infrastructure (i.e. through rusting)
Soil acidification / As soil becomes more acidic, availability of nutrients change and some chemicals become unavailable whilst others increase to toxic levels – producing uneven crop and pasture growth. legume nodules develop poorly in acidic conditions and acid tolerant weeds (geranium, fog grass and sorrel) invade and can out compete pastures
Soil structure decline / Tillage machinery can pulverise soil aggregates and compact soil, OM is reduced by tillage, seedling emergence is reduced (as arrangement of particles and air spaces is altered so water infiltration and aeration are not optimal) and increases erosion hazard

Discussing the issues related to water quality, supply and regulation

Problems / Solutions
Over consumption / -  Water restrictions
-  Better water use (i.e. campaigns like Water Wise)
-  Use of more efficient systems (drip irrigation not flood irrigation)
-  Education and community awareness
Contamination with industrial waste, fertiliser and pesticides / -  Industrial waste regulation
-  Pollution controls
-  Purification systems
Urbanisation / -  Regulate urbanisation with planning controls
Loss of native fish and increasing carp levels / -  Restocking of rivers with native fish
-  Aquaculture industries
Groundwater contaminated by leaching from landfills and disposal areas / -  Regulation of designated disposal areas and landfills to prevent chemical seepage and leaching into groundwater supplies
River degradation / -  Maintenance of native vegetation to stabilise riverbanks
-  Vegetation acts as a filter for chemical runoff and soil deposition into river system
-  Fence off river banks so livestock cannot graze vegetation and trample soil
-  Engineering works to direct flow of water away from banks
Algae contamination / -  Prevention of excessive runoff of nitrogen and phosphorus fertilisers which encourage the rapid build up of algae
Rising water tables and salinity problems / -  Salinity control measures i.e. planting perennial pastures and trees and implementing drainage systems
Destruction of natural wetlands / -  Regulations to prevent destruction of wetlands

Examining the causes of the following types of soil degradation: soil erosion, Dryland salinity, irrigation salinity, soil acidification and soil structure decline (with special reference to those arising from farming practices)

1.  Soil erosion

·  Removal of soil from an area

·  Affects productivity of farm, district and catchment level because eroded soils are less fertile

·  Has an enormous impact on environment as soil washed into watercourses increasing turbidity and adding nutrients and other chemicals that can affect water quality

·  Main cause is loss of vegetation – more plant cover means soil is more protected against erosion

·  Cultivation and overgrazing can also leave soil unprotected and increase rate of erosion

·  Erosion by water begins with impact of raindrops on soil surface. Plant residue will cushion the fall of raindrops which otherwise shatter soil peds

·  Once surface is disturbed by raindrop impact, soil particles are readily washed away by water in runoff

·  Moving particles in turn scour other soil surfaces increasing rate of erosion – lack of vegetation will increase rate of runoff - fast moving water carries more soil and causes more damage than slow water

·  Sheet erosion (a uniform layer of soil is removed from surface), Rill erosion (runoff produces many small channels across surface) and Gully erosion (runoff cuts deeper channels through land surface) are all types of water erosion

·  Recommended treatments aim to maintain a good ground cover of grasses, herbs and leaf litter

·  Cultivated land soil conservation structural works such as contour banks are installed to:

-  Reduce velocity of surface runoff

-  Divert runoff to safe disposal sites

-  Contain sediment within bank channels

-  Direct tillage operations onto the contour

·  Crop and soil management practices are a necessary component to reduce sheet and rill erosion on cultivated land. Practices include:

-  Changes to rotations to reduce number of cultivations

-  Stubble retention to protect ground surface

-  Green manuring to improve OM levels

-  Reduced or Zero tillage systems which involve use of non-residual herbicides to control weed growth and reduce level of disturbance of soil

·  On grazing lands ground cover can be improved by:

-  Adjusting stocking rates

-  Evenly distributing grazing pressures by installing more watering points

-  Applying fertilisers, including trace elements for known deficiencies

-  Removing stock when ground cover levels fall below critical limits or if erosion levels fall below critical limits or if erosion levels are severe to very severe

-  Constructing works to control surface runoff across bare areas and assist revegetation

·  Wind is able to lift and carry away light, sandy soils and fine soils

·  Soil that is left is less fertile and less able to retain moisture

·  Risk of wind erosion is increased by reducing groundcover and by breaking soil aggregates into smaller, lighter pieces

·  Lands which are subjected to very severe wind erosion when disturbed are best left in their natural state

·  Where danger is less severe lands may be cleared for grazing but not cultivated for annual crops

·  On cropping lands, best ways to reduce threat of wind erosion are to:

-  Retain crop stubble for as long as possible after harvest

-  Avoid stubble burning

-  Sow succeeding crops into stubble residues

-  Use reduced tillage systems

·  Increasing length of rotation (in crop rotation) can improve soil structure which reduces hazard of erosion

·  Maintaining adequate groundcover can be achieved by retaining crop stubble, direct drilling crops into old stubble, reduced tillage, no burning of stubble and adjusting stocking rates (so no overgrazing occurs)

·  Farming practices that may increase ground over loss include increased stocking rates, sowing introduced pasture species, applying fertilisers (increases plant nutrients which increases the number of insects) and clearing vegetation

2.  Irrigation Salinity

·  The Murray-Darling River Basin has been severely affected by salinity

·  Cutting down trees has significantly contributed to salinity as trees used to use the water rather than letting it leak down into the water table. Water table rises with increasing groundwater. This groundwater can rise to the surface, bringing soluble salts with it (this is Dryland salinity)

·  Recommended treatments involve lowering saline water tables below the root zone of plants however it is more efficient to prevent the problem rather tan attempt to treat degraded land

·  Prevention requires improvement in irrigation practices - only water that is needed should be applied

·  Water applications should be timed on basis of soil moisture levels

·  Where water tables are already high and are restricting production, mechanical systems i.e. deep drainage can be installed to lower water table levels. If waters are saline, they should be diverted to evaporative basins to stop salt from entering rivers and affecting downstream areas

3.  Soil acidification

·  Plant growth is reduced as soil becomes acidified which in turn increases rate of erosion (no groundcover)

·  Main factors increasing soil acidity are:

-  Nitrate leaching – nitrogen compounds (i.e. from fertilisers and legumes) can be converted into nitrates in the soil. Nitrates begin to accumulate in soil if there are insufficient plants (particularly deep rooted perennial pasture grasses). These excess nitrates are leached deeper into subsoil or watercourses. Other nutrients (calcium, magnesium etc) leach away with nitrates. Overall effect of leaching is an increase in concentration of acid in topsoil

-  OM accumulation – improved pastures add OM to soil (much more so than natives) OM is acidic and when it accumulates in soil, pH can be lowered

-  Fertiliser use – some acidify the soil i.e. those containing ammonia or elemental sulphur will lower pH when they are converted to forms plants can use. Other fertilisers do not directly acidify soil even if fertiliser is acidic (i.e. Superphosphate) as there is not sufficient acid in application to change pH however it promotes the growth of plants (i.e. Superphosphate encourages clover) which in turn adds OM, building up nitrate reserves, leading to soil acidification

-  Product removal – acidity increases with the removal of hay, crops and animal products. Plants remove a range of nutrients from soil i.e. when calcium, magnesium and potassium are taken up by plants, acidity of soil increases

·  Recommended treatments for soil acidification include:

-  Liming with an appropriate rate and method of application of a suitable quality lime along with proper timing of application and effective incorporation into soil (lime increases soil pH by reducing hydrogen in soil water)

-  Use of acid-tolerant plant species

-  Changes in management of farming systems to reduce rate of acidification, including modifying fallowing practices, using deep rooted perennial species and ammonia based fertilisers and increasing grass levels in legume based perennials

4.  Soil structure decline

·  Tillage implements as well as stock trampling break up peds and destroy structure

·  The quickest and most effective way of reversing soil structure decline is to establish a good a pasture that includes fibrous rooted grasses

·  On cropping lands the following techniques are recommended:

-  Integrating pasture leys of suitable length within the cropping rotation (an essential requirement)

-  Using reduced/zero tillage and direct drilling practices (moderately textured red earth's)

-  Using green manuring crops to increase OM content (moderate to light textured soil)

-  Breaking up plough pans or compact soils by deep ripping (benefits of this rapidly disappear in high silt/sand content soils)

5.  Dryland salinity

·  Build up of salt in surface soil usually as a result of rising water table and subsequent groundwater seepage – refers to non-irrigated areas showing a salt problem

·  Native trees, shrubs and perennial grasses dry soil out – when land is cleared and these plants are replaced with shallow rooted crop and pasture plants (wheat and clover) and these do not soak up as much water therefore excess water leaks into groundwater causing level to rise until it reaches surface

·  When water table rises, salts stored deep in soil profile are mobilised and these salts become concentrated at surface by evaporation