Full HSC course Notes Flashcards
(143 cards)
1
Q
pH
A
measure of the acidity of alkalinity of the soil - ph affects availability of nutrients
- 0 Most acid
- 14 Alkaline
- 7 Neutral
- optimal: 5.5 – 7.5
2
Q
how is ph measured and what is it?
A
- measured using a test kit in the field or soil is send to a laboratory
- a measure of the relative amount of free hydrogen ions in the water - lower pH = higher amount of H ions
3
Q
what is soil acidification most often resulting from
A
nitrate leaching
4
Q
how does nitrte leaching in soil occur
A
nitrate is very mobile nad easily leached with water
- heavy rainfall
- over irrigation
- well drained soil and excess nitrogen in soil
5
Q
Nitrogen is added to the soil by:
A
- Planting legumes: bacteria that live in small growths called nodules on the roots. within these nodules, nitrogen fixation occurs by the bacteria and the NH3 they produce is absorbed by the plant. - this is a partnership between bacteria and plant
- Using nitrogen based fertiliser: will add nitrogen through soil and amount added can be controlled
- Breakdown of OM (Dung and urine): soil organisms including micro-organisms use soil organic matter as food. as they break down OM, excess nutrients such as nitrogen and phosphorus are released into the soil in forms that the plants can use. this process is called mineralisation.
6
Q
which fert improves pH of soil when acidic
A
lime - (commonly calcium carbonate) will neutralise soil acidity by neutralising acid reactions in soil.
- the carbonate component reacts with hydrogen ions int he soil and in doing so raises the soil ph
7
Q
effects of Ph:
A
- plant growth: at extreme pH, the availability of some nutrients is decreased (phosphorus at low pH and zinc at high pH) and the solubility of elements toxic to plants is increased (aluminium and manganese at low ph)
- Rate of biological chemical reactions within the soil: influencing the availability of nutrients and the activity of microorganisms
- microbial activity (rhizobia are inhibited in acid soils): (breakdown of OM and cycling of nutrients), reduced in acidic soil as growth and reproduction of the soil microbes, primarily fungi and bacteria are reduced
- nutrient availability: at extreme pH, the availability of some nutrients is decreased (phosphorus at low pH and zinc at high pH) and the solubility of elements toxic to plants is increased (aluminium and manganese at low ph)
- susceptibility to pests and disease: Where soil pH increases, activity of root-infecting pathogens may also increase. Nutrient deficiencies can predispose plants to a higher level of disease infection, further limiting plant growth.
8
Q
Ion exchange capacity
A
measure of the soils
ability to hold positively charged ions
This influences the soils ability to hold onto essential
nutrients and provides a buffer against soil
acidification
9
Q
Cation
A
ion with positive charge
10
Q
Anion
A
ion with negative charge
11
Q
CEC of OM
A
200-400 meq/100g
12
Q
CEC of Clay minerals
A
10-150 meq/100g
13
Q
CEC of Sandy soils
A
below 10 meq/100g
14
Q
why do sandy soils require good fertilisers programs
A
sandy soils have high porosity which leads to low nutrient and water retention and high leaching of nutrients
Sandy soils are known for their large particle size and high porosity, which result in low water and nutrient retention capacities. This often leads to rapid leaching of nutrients, necessitating more frequent but smaller applications of fertilizers to ensure nutrients remain available to crops
15
Q
Soil pH
A
- Measurement of hydrogen ions in soil
- Lower pH higher amount of H ions
- 10x more ions each shift down scale
- Limits available nutrients to plant
- Decrease microbes, reduces plant varieties able to grow
- Modify; adding lime, addition of fertilisers, monitoring of nitrogen fertilisers
- a measure of the acidity/alkalinity of the soil
- critical pH level of soil = 4
- optimal: 5.5 – 7.5
- affects availability of plant nutrients
- different plants can grow in different pH
environments - affects the activity of soil microorganisms,
thus affecting nutrient cycling and disease risk - INCREASE PH: lime, wood ashes, compost
- DECREASE PH: ammonium and ammoniumforming N fertilisers, elemental sulphur
16
Q
fert to increase ph of soil
A
lime, wood ashes, compost
17
Q
fert to decrease ph of soil
A
ammonium and ammoniumforming N fertilisers, elemental sulphur
18
Q
CEC
A
cation exchange capacity - indicator of soil fertility and nutrient retention capacity
- a measure of the quantity of cations that can be absorbed and held by a soil
- measured using electrical probes
19
Q
what holds cations in soil
A
negatively charged particles, OM and clay
20
Q
what does low and high CEC mean for soil?
A
Lower CEC = regular fertilising required, plants lack nutrients, High CEC =
soils retain nutrients
21
Q
how to modify CEC?
A
change pH, manage fertilisers, maintain OM
22
Q
what will a high CEC do to soil?
A
Make it harder to change factors like pH as less leaching of both cations and anions will occur
23
Q
soil carbon and organic matter
A
- carbon stored within the soil
- made up of plant/animal materials in various stages of decay
24
Q
how to measure OM of soil?
A
moist soil sample weighed, then heated and re-weighed, showing amount of OM
25
what does soil carbon and OM do to soil?
increase water holding capacity, improve soil structure, increase CEC, increase microbe
population
26
improvement methods for soil carbon/OM
green manuring, stubble retention
27
green manuring
a crop specifically cultivated to be incorporated into the soil while still green
28
stubble retention
leaving crop residues on the soil surface after harvest, rather than burning or cultivating them. This offers numerous benefits for soil health, including reducing erosion, improving water retention, and enhancing soil fertility.
29
Nutrient Status
- Amount of nutrients present in soil, composition of macro (N, P, K, S, Ca) and micro (Co, Fe, Mn, Cu, Zn, B) nutrients
30
how is nutrient status measured
CEC
31
what does nutrient status effect?
- in plants, it effects its ability to grow and
produce yield
- in animals, poor soil fertility can decrease
pasture production and feed quality thus
decreasing nutrients available for healthy
animal growth and production
32
Soil structure
The arrangement of soil particles (sand, silt, clay and OM)
- measured visually
33
effects of soil structure
compacted clay leads to difficult root penetration and water/air movement.
poor structure can cause problems with; erosion, water infiltration, porosity, aeration, root penetration and growth, temperature of soil
34
ways to improve and manage soil structure
- practices such as cultivation and grazing can
lead to pulverisation and compaction of soil peds which in turn can lead to soil erosion and other negative soil actions
- decreasing cultivation, increasing OM, decrease overgrazing and use preventative measures to reduce compaction
35
Soil Texture
- refers to the size of the soil particles and the
% of sand, silt and clay
- different % of sand, silt and clay can impact
soil fertility and structure
36
how can soil texture be classified/measured?
texture classification can be determined by ribbon method and a texture triangle
37
what does soil texture affect?
- in plants it affects root penetration, seed
germination, nutrient availability, porosity and
infiltration
- soil texture can decrease in quality and yield
of pasture production which in turn can
decrease the carrying capacity of stock
38
ribboning technique/texture triangle
ribboning:
- rolling a moist soil sample into a ball, and then pressing it out between your thumb and forefinger to form a ribbon
- no ribbon = sandy, ribbon less than 1 inch + feel gritty = sandy loam, smooth = silty loam and it neither = loam
Texture triangle:
- used to classify the texture class of a soil
- The sides of the soil texture triangle are scaled for the percentages of sand, silt, and clay.
39
pore spaces
- sandy soil = large pores = less of them, less WHC
- clay = small, large amount,
small pores = water storage
40
Porosity
- spaces between aggregates that allow for root penetration, infiltration and drainage
41
how to measure soil porosity
measuring the extra mass of water which is required to saturate a soil sample
42
what is the effect of soil porosity
- Optimal porosity enhances water infiltration, root growth, and biological activity
43
how to modify soil porosity
- add organic matter/ inorganic amendments
- implement practices that enhance soil structure and reduce compaction such as overgrazing and over cultivating
44
Bulk Density
refers to how tightly packed the soil peds are together
45
what does bulk density affect?
the amount of oxygen, water holding capacity and infiltration rate; roots are unable to penetrate soil to reach water
46
how is bulk density measured?
determine the dry weight of a sample and divide it by its total volume
47
effect if BD?
- High BD = increased compaction = poor root/plant growth, increased runoff,
erosion, decreased movement air/water
- low BD = less compaction = healthy aeration, water movement and root growth = better soil health and plant growth
48
how to modify BD?
increasing organic matter, protecting the soil surface (from cultivation/over grazing), and reducing tillage and equipment traffic to reduce compaction
49
experiment to determine soil pH
add barium sulfate and a universal indicator to soil sample to determine the pH
50
experiment to determine soil carbon
hydrogen peroxide - reacts with soil organic matter as the length/intensity of the fizzing can give a rough estimate to how much organic matter is present
51
experiment to determine soil structure/porosity
digging a hole 20-30 cm and taking out a slice and
observing pack weight of soil, softness , aeration
spaces that can be created by earthworms and other
microbes
52
experiment to determine soil texture
1. determined by feel; ribboning – different lengths of ribbon and initial feel can be related back to a table to determine type
of soil
2. mechanical analysis; mixed with water, particles
separate into sand silt and clay (% can be determined by this)
3. Texture triangle
53
experiment to determine bulk density
- take sample of soil and weigh its dry mass then divide it by the total volume of all constituents
54
nitrogen cycle
- nitrogen is nutrient needed in largest amounts by plants but excess can be
harmful to plant growth and crop quality as well as harming the environment
and water quality.
- Availability can affect rate of ecosystem processes e.g primary production
- Plants absorb nitrogen in form ammonium or nitrate through roots
55
two different forms of nitrogen
Urea and ammonium
56
nitrification
ammonium converted to nitrites then to plant available form nitrates
57
leaching
nitrates pass the plant root zone and contribute to soil acidification through water movement, rising water table or excess nitrogen that isnt taken up by plants
58
Denitrification
the process that converts nitrate to nitrogen gas
59
what can happen is soil nitrogen is mismanaged?
Too little nitrogen can stunt plant growth and reduce yield
too much can damage plants, contaminate water sources, and contribute to greenhouse gas emissions
60
carbon cycle
- a process in which carbon molecules are used and broken down in a recyclable manner. This occurs as animals/plants use carbon in different ways and in different forms.
61
how is global warming occuring
- Increased Co2 in atmosphere from human activities
- global warming occurs as radioactive heat is trapped in atmosphere
- plants are unable to keep up with increased co2
62
can soils store co2
yes, soils are co2 reservoirs
through process of carbon sequestration, plants take carbon dioxide from the atmosphere through photosynthesis and incorporate it into the soil
63
farming practices that increase co2
cultivation, burning
64
farming practices that decrease co2
Perennial pastures, stubble retention
65
cultivation
the practice of preparing and working the land to grow crops, including activities like tillage, planting, and weeding
66
soil nutrient cycles
process in which nutrients are recycled and made
readily available for consumption by plants and other organisms.
67
soil nutrient cycles steps
1. materials broken down by macro/meso-fauna
2. nutrients absorbed and converted by lower life forms in soil
3. conversion of these nutrients to organic forms within the cell or to inorganic forms released to soil
4. organism die/decomposed by other organisms > also releases
inorganic ions
5. inorganic material taken up by plants
6. repeat
68
what is the roles of microbes and invertebrates in the decomp of OM?
- Soil organisms (microbes and invertebrates) are responsible for the
decomposition of organic matter – which converts the OM into inorganic
substances and ions that are available for plant uptake.
- They play a major part
in nutrient cycling.
- Microbes such as bacteria eg. Nitrobacter, Pseudomonas, Rhizobium are present in large quantities and are involved in nutrient cycling (carbon) as well as cellulose/protein breakdown.
- Invertebrates (earthworms, millipedes and beetles) also involved in the breakdown of OM - also aid in aerating the soil.
69
nitrogen Nutrient Cycling and Microbes/Invertebrates:
when plants and animals die or expel waste, the initial form of nitrogen is organic.
Bacteria and fungi can convert this into ammonium ions
which can then be assimilated into the plants roots
70
carbon Nutrient Cycling and Microbes/Invertebrates:
Carbon is present in organic matter – microbial decomposition converts this back into carbon dioxide and return it back to the atmosphere.
71
Aboriginal land practices
- over 40 000 years, Aboriginal people have successfully managed the land
- using methods in such ways that resources are renewed and not exhausted.
- deep understanding of season changes and knowledge of the area.
- Aboriginal people have a deep and spiritual connection to the land
72
foods of aboriginal people
kangaroos, possum, ducks, snakes, goannas, lobsters, shellfish, witchetty grubs, crabs, tortoises and seals.
73
Aboriginal people caring for country
- by eating large variety of foods in systematic/sustainable manner, no one food source can be over-exploited.
- When eating plant foods, enough seeds are left so that there will always be new growth.
- The young of any animal, or any female if it still has offspring are rarely killed.
- When collecting eggs, some are always left to hatch thus ensuring survival of the species.
74
aboriginal people farming / technology
- includes hunting and all forms of food collecting as
well as intensive farming such as eel trapping and yam growing.
- Aboriginals used many techniques such as burning off vegetation, fallowing, using nets, sticky sap, using seeds, using snares, swimming underwater, shell hook and bark string, soaking poisonous plants in waterholes to obtain food.
75
Aboriginal people: Fire
- used for cleaning up vegetation – making it easier to walk through the
land and safer as snakes and other organisms could be avoided
- promote growth of valued plants – attracts grazing animals back to the area for hunting,
- drive out animals which can then be killed or food e.g. smoke from the fires to
flush out possums from trees.
- controlled use of fire has been used for thousands of years. The burning pattern has changed the appearance of the Australian bush with large areas of forest being replaced by open grassland.
- The impact of the continual use of fire meant that plant species which did not regrow well after fire declined in numbers, whist more fire-resistant species
dominated. - the use of fire also trained plant regrowth to be triggered by fire
- burning by aboriginal people was only very light and controlled and only burnt dead matter and gave animals time to escape, it was aimed for regrowth - different from modern back burning which is a harsh fire and can cause severe damage to bushland
76
firestock farming Impact on Land and Agricultural Systems
Decreased wildfires, provides fresh food for
livestock, germination
77
Clearing Land Impact on Land and Agricultural Systems
Can lead to increased weeds, beneficial
production of new crops
78
Multiple Cultivations Impact on Land and Agricultural Systems
Decreased soil, decreased OM
79
Clearing trees and Native Vegetative Impact on Land and Agricultural Systems
Soil erosion, increased weeds
80
Crop Rotations Impact on Land and Agricultural Systems
High nutrient status, increased soil structure, increased OM/WHC, decreased compaction
81
Synthetic Fertilisers Impact on Land and Agricultural Systems
Stimulates soil life, decreased pH, increased yield of crop
82
Cultivating Impact on Land and Agricultural Systems
Decreased soil structure, compacted
soil/erosion, increased weeds
83
summary of present day land use practices
- australia has gone through phases of exploitation and expansion
- industries have adopted new technologies and methods - dealt with major issues such as soil erosion/pests
- as consequence, there has been steady growth in the area of some land uses such as cropping and productivity in terms of animal numbers
84
intensification
- term used to describe modern day land use practices
- means the greater use of inputs or speeding up of processes
- intensification of australian land comes from new technologies to adapt to challenges and from the modification of natural resources (irrigation, frost avoidance, fert application)
85
historical phases of agricultural developtment in aus
- wool (untill 1900)
- beef/cattle (1900-1975)
- grains (1975 - current)
86
what defines land use
climatic factors
- intensive land use are generally in wetter temperate parts of aus
87
why have the total numbers of farms declined since 1960s
conversion of areas to conservation areas, infrastructure and urban development
88
major driver for changes in ag land use
- market process for potential products
- productivity gains
- personal drivers (development of skills)
- lifestyle objectives
- stewardship and orientation to change
- new technologies that open up opportunities to intensify or convert land uses
89
source of water: rainfall
- effective rainfall: no. of consecutive months of
rain that exceeds 1/3 of evaporative demand
- majority of continent has rainfall that is
inadequate for cropping or intensive farming
- on average, 10% of rainfall become run-off
and 90% is evaporated or used by plants
90
source of water: Aquifers (groundwater)
- makes up nearly 1/5 of Australia’s sustainable
water resources
- most of Aus. Groundwater is drawn up from
Great Artesian Basin
91
source of water: Stored Water
- 501 large dams in Australia
- more than 2 million farm dams in Australia
- estimated to have a total storage capacity of
8000 gigalitres
92
source of water: surface water
- river systems: license required to abstract
water for agricultural purposes
- harvestable rights:
allows landholders to collect up to 10% of average regional rainfall runoff on their property
- they can use this water in farm dams, provided the dam is built on a hillside or minor stream
93
how is water managed in aus
- the granting of water access entitlements (ongoing entitlement to exclusively access a share of water from a river system or bore)
- allocations (specific volume of water to be allocated in a specific season)
94
water management: irrigation
- sustainable irrigation methods need to be
employed by farmers; excessive irrigation can lead to rising of water table
- irrigation salinity can turn once productive land into an environment incapable of any form of agriculture
- the introduction of Partial Rootzone Drying (PRD) is one method used in the production of grapes that ensures irrigation levels remain low and the sustainability of the land is
guaranteed
95
Partial Rootzone Drying (PRD)
irrigation technique when the one side of the plant's roots is exposed to drought and in the same time other side is irrigated
96
water management: effective rainfall
- due to unreliability of rainfall and minimal
harvestable rights, farmers need to regulate their own use of water to guarantee
availability for stock/domestic use.
- construction of dams, troughs, rainwater tanks are important features of a typical farm
97
water management: monitoring quality of water
- farmers need to maintain water quality so that it stays safe for animal consumption
- effluent and chemicals running into bodies of
water need to be restricted as to limit risk of blue-green algae outbreak
- rivers often fenced to limit erosion and sediments going into waterway
98
legislation and government: water
- water use in managed through the granting of water access entitlement and water allocations
- entitlement can be issued to commercial users such as irrigators, mining and industrial purposes as well as non-commercial users including town supplies, recreation and environmental resources
99
water access license
entitles a holder to share available water in specific water source and to take water from a specific location
it specifies:
- size and share
- water source
- category (categories are a mixture of priority and purpose)
- location
- nominated works (usually works approval ID)
100
influences on availability and use of water
▪ if farmer has no license then they are only entitled to the limited water under harvestable rights
▪ with a license a farmer is capable of irrigation and more intensive farming practices
▪ due to water availability, a farmer’s productivity can be limited to season
101
impact on soil of soil erosion
- remove topsoil making soil less fertile
- cause ‘gullies’ which form when fast flowing runoff hits a 'nick' point such as a rabbit burrow, root hole and can cause further soil degradation
- reduce plant growth therefore reduce OM and lead to more soil structural decline
102
impact of soil erosion on water
- topsoil mixes with
waterways causing muddy water polluted water
- decrease in naive fish as water becomes uninhabitable
- affect light penetration of water bodies
- take fertiliser to water as well as other farm chemicals - pollution
103
effect of salinity (dryland and irrigation) on soil
● increased salt
content of soil
● affect soil fertility
● lowers CEC
104
effect of salinity (dryland and irrigation) on water
● increase salt concentration in water
● affect animal/human
consumption and may require water to have to be used from other off farm resources
● kill native plants/animals in water system
105
affect of soil acidification on soil
● affects CEC
● critical pH level: 4
106
effects of soil acidification on water
● affect plants and animals in waterways
● imbalance ecosystem
107
effects of soil structural decline on soil
● increase bulk density which in turn smothers plants roots, affects air spaces within soil and decrease plant growth (decrease OM and yield)
● increase in soil erosion when soil aggregates break down
108
effects of soil structural decline on water
● if soil erosion occurs - soil particles may enter water creating a turbid environment
● more water run off as it cannot percolate into the soil as of high bulk density
109
effects of loss of soil OM on soil
● decrease CEC due to decrease nutrient availability (which can in turn affect plant growth)
● decrease in soil fertility
● can lead to soil structural decline as OM cant contribute to structure in holding soil aggregates together
110
effects of loss of soil OM on water
● if soil structure decline occurs creating soil erosion; then can create a turbid environment
111
112
soil salinity
- the rising of the level of salts in the soils to such concentrations that they adversely affect the growth of plants.
- Deep in the soils are large reserves of salt; if the water table rises, these salts are
brought to the surface and can cause major impacts on agricultural productivity.
- most commonly caused by over watering through irrigation and the removal of deep rooted natives to be replaced with shallow rooted crops
113
effects of soil salinity on soil
- increased salt content
- affects fertility
- lowers CEC
- No plant growth (no OM, erosion, decreased structure)
- decreased feed for stock
114
effects of soil salinity water
- bad quality water
- Reduces usefulness of water for humans/plants/animals
- increase salt concentration
- affect animal/human consumption (salty water)
- kill native plants and animals in water system
115
where has salinity become a major issue
in irrigation and dryland areas
116
irrigation salinity
- the use of large quantities of irrigation water has resulted in the water tables rising and the upbringing of salts to the surfaces – which can affect plant growth.
117
ways to reduce and restore irrigation salinity
- installation of drainage systems
- storing salty water in large water basins
- more judicious and efficient use of irrigation water
- pumping water from the water table
- planting deep rooted trees and deep rooted perennials to maintain water table level
118
dryland salinity
- the accumulation of salts in the soil surface and groundwater in non-irrigated areas
- result of the water tables rising, bringing salt to the surface
- caused by the removal of trees that acted as pumps and maintained water tables, drawing water from deep in the soil and passing it into the atmosphere by transpiration.
- Salinity caused by the removal of trees can also contribute to soil
erosion.
119
fertiliser usage effect on water quality
- impacts the pH level in water negatively; as it provides an imbalance of nutrients to water
- excess nutrients can cause blue-green algae outbreak which is highly toxic
- can make it unsuitable for irrigation
119
methods to reduce and reverse dryland salinity
- reestablishment of deep rooted native trees
- planting of deep rooted perennials
-fencing off salt affected areas and planting them with salt tolerant pastures and crops
- using reduced stocking rates
120
fertiliser usage effect on water quantity
- decreases availability of water as less is able to used for human/animal consumption
121
solutions to decrease effects of fert usage on water
- Reduce runoff
- Crop rotations
- Retain ground cover
122
effects of stock on water quality
- increases faecal matter in water - which decreases hygiene on farm and can cause increase risk of disease
- increases turbidity
- increases effluent in water which in turn can increase nutrients in water
– can can cause blue-green algae outbreak which is highly toxic
123
effects of stock on water quantity
- decreases availability of water as less is able to used for human/animal consumption
124
solutions to decrease effects of stock on water
- Fence off stock from
waterways
- Grazing rotations
125
effluent
liquid waste or sewage discharged into a river or the sea.
126
effects of effluent management on water quality
If effluent management is poor it can:
- increase nutrients in water; this can can cause blue-green algae outbreak which is highly toxic
- decrease water quality overall
- make it unsafe for consumption and use on farm
- can pollute surrounding areas and cause death in native flora/fauna
127
effects of effluent management on water quantity
If effluent management is poor it can:
- decrease availability of water as less is able to used for human/animal consumption
128
solutions for the effects of effluent management on water
- Groundcover
- Fence off waterways
129
effects of chemicals on water quality
- pesticides etc. will kill natural flora and fauna
- chemicals such as oil on top of water can decrease oxygen and light penetration
- can contaminate water
- Imbalance in aquatic
environment
- Release toxic chemicals into ecosystems
130
effects of chemicals on water quantity
Volume is not affected, but the available of useable water is decreased.
131
solutions for the effects of chemical useage on water
- IPM
- Do not apply chemicals in areas of runoff risk
- Consider application method
- do a rotating roster of chemicals
- only use it when needed and only use the specific quantity
132
effects of grassed waterways on water quality
have a positive effect:
- offer filtration of water to possible pollutants
- plant growth holds soil
together therefore less erosion and turbidity
133
effects of grassed waterways on water quantity
volume of water can decrease due to plant uptake
134
riparian zones
land alongside waterways like rivers, creeks, and wetlands, acting as a buffer between terrestrial and aquatic ecosystems - for farms this can be fenced off areas with vegetation on banks of waterways
135
effects of riparian zones on water quality
have a positive effect:
- increase in water quality as less of a chance of faecal
matter from stock reaching
waterways
- decreases erosion and
turbidity
- filters water with natural
vegetation
- can decrease degradation of land alongside waterways
136
effects of riparian zones on water quantity
- there is a chance of slight
increase of volume as there is no stock consumption
137
effects of dam construction on water quality
decrease in water quality:
- less ‘flushing‘ of water (filtration)
- can lead to a build up of
effluent and chemicals in
water
- changes natural pattern of seasonal flow
138
effects of dams on water quantity
- decreases quantity
downstream but areas around have greater access as close by to the water source
139
solutions to dam construction on water quality/quantity
good management
140
effects if irrigation on water quality
if poor: (e.g flood irrigation)
- decrease water quality by the rising of the water table which can increase the problem of salinity
if good: (e.g. drip irrigation)
- there is little effect
141
effect of irrigation on water quality
if poor:
- decrease quantity of available water as there is large amounts being used
if good:
- still decreases as there is still large portions of water being used
142
