Cover Crops

Question 1

What are the effects of using herbicides?

Answer 1

-Soil organic matter (SOM) decrease
- More som mineralised than added from above
- soil pH often decreased
-soil microbial life and earthworms decreased
-reduced nutrient cycling
-reduced water infiltration rates
-decreased aggregate stability of the soil

Question 2

3 big changes over the last 60 years?

Answer 2

-clean cultivation was practised to suppress weeds
-use of herbicides
-use of organic mulches, compost and cover crops

Question 3

Why control weeds in vineyards?

Answer 3

-weeds competr with vines for water and minerals
-presence of weeds increase risk of spring frost demafe
-weedd can make harvest nosre difficult and confer off flavors to the wine
-weeds can kill young vines

Question 4

Major techniques for floor managemen?

Answer 4

-mechanical weeding(tillage)
-cover crop
-chemical weeding

Question 5

Minor techniques for floor management?

Answer 5

-Thermal weeding
-black plastic soil cover
-green manure

Question 6

Why is bare earth policy recommended?

Answer 6

To reduce frost demage

Question 7

Cover crops definition?

Answer 7

Any plant species used singly or mixed, deliberately sown between vine or tree rows or as an intermediate crop before an annual cash crop, to improve soil physical, cemical and biological conditions

Question 8

What can cover crops do?

Answer 8

-decrease dust and erosion
-can be used in water management
-increase water filtration
-reduce leachinf of nutrients through the soil
-improve soil aggregate stability
-improve vineyard carrying capacity and accessibility
-immobilizing nutrients
-reduce the impact of rainfall
-reduce run off
-legume cover crops are nitrogen fixators
-produce organic matter
-provide food for micro-organisms
-could host predatory insects
-could out-compete undesirable weeds
-are attractive

Question 9

What nulching do?

Answer 9

Releases accomulated nutrients in cover crops back to the soil in 2-9 weeks, after incorporation

Mowing the same, but slower

Question 10

What reduces mineralisation speed?

Answer 10

Using a roller/crimper

Question 11

What short mown sward do?

Answer 11

-Limits frost risk
-improves soil structure water infiltration, traffic flow in the vineyard

Question 12

Negative impact of cover crops on vineyards?

Answer 12

-competition of water
-Competition of mineral nutrients
-reduction of vineyard temperature=>frost
-extra cultivation, sowing and maintenance at an extra cost
-soil compaction

Question 13

Nrgative practical impact of cover crops on vines?

Answer 13

-demage of buds through frost
-poor growth of young vines

Question 14

+- practical impact of cover crops on vines

Answer 14

-Delay veraison and slow down ripening
-reduction of the herbaceous character of the wine
-reduction of vigour and shading the fruit

Question 15

+ practical impact of cover crops on vines?

Answer 15

-improvement of berry composition
-reduction of downy mildew
-reduction of the incidence of botrytis

Question 16

Additional cover crop management

Answer 16

-cultivating
-sowing
-fertilizing
-irrigating
-mowing
-re-sowing?

Question 17

Soil organic matter consist of…?

Answer 17

-decomposing residues
-plant root exudates
-worms
-bacteria
-yeasts
-other microbial life

Question 18

Root exudates:

Answer 18

-regulate soil microbial community
-encourage beneficial symbioses
-change chemical and physical properties of soil
-inhibit growtg of competing plant species
-5-21% of photosynthetically fixed carbon being transferred to the rhizospherr through root exudates

Question 19

Which soil factors are posutively influenced by increased soil organic matter?

Answer 19

-soil tiltg and structure
-pH was moderated
-increased nutritional balance
-cation exchange capacity (cec)
-microbial activity
-water holding capacity
-water and air infiltration
-water drainage
-soil temperature and moisture were stabilised

Factors are important for plant healtg, heloing to maintain plant defences against pests and diseases

Question 20

How high SOM has to be?

Answer 20

Very low: <1%
Low: 1-2%
Satisfactory: 2-4%
High: >4%

Can take 5-19 years for OM to build up 1-2%, but takes only 2 years to lose the same amount

Question 21

The speed of SOM build up will depend on…?

Answer 21

-the amount of OM brought back into the soil
-the way of cultivation, because cultivation will increase the breakdown of SOM
-temperature and moisture

Question 22

Good sources of SOM include…?

Answer 22

-Plant material from previous seasons
-green manure from cover crops
-mulches, compostd from pruning and marc, imported plant materials, imported animal or town waste
-combination of any of the above

Question 23

Perennial cover crops

Answer 23

-offer year rounded protection of the soil
-improve access to the vineyard also over winter
-dont require frequent cultivation and sowing
-Mowing can cause soil compaction
-less active over summer and hence leys conpetitive for water
-with trickle irrigation, most water applied will go to the graoe vines while mid-row cover crops will dry off over summer

Question 24

The increase in plant available nitrogen happens through:

Answer 24

-N fixation by Rhizobium bacteria in legumes that convert nitrogen gas(N2) to ammonia(NH3)
-fertiliser
-manure
-acid rain
-crop residue

Question 25

N modifications that take place

Answer 25

-break down of organic matter
-mineralisation of organic N (proteins&amino acids) to ammonium(NH4+)
-nitrification of ammonium (from feltiliser and natice vegetation) to nitrite(NO2-) and nitrate(NO3-)
-De- or fixation of ammonium nitrogen

Question 26

The loss of plant available N can occur by means of:

Answer 26

-Leaching of nitrate
-run-off
-immobilisation of ammonium in OM
-crop removal
-plant uptake
-volatilisation of ammonia
-immobilisation of ammonium at the clay

Question 27

How available is N?

Answer 27

-both legumes and non-legumes contribute to N avaulability for vines by taking up mineral N from the soil that would otherwise have leached
-all N is immobilised through incorporation in plant structure and will be released again as the cover crop decomposes
-for decomposition of organic material with high C/N ratio, micro organisms initially take nitrate out of the soil
-most nutrients from organic materials will end up in the top layer of the soil profile
-in Winter temperature is too low for much mineralisation
-in dry soils N mineralisation is slow
-in wet soils cover crops can increase aeration and hence improve mineralisation
-flush of nitrate( NO3-) four weeks after cutting of the more lignified grass sward

Question 28

Nitrogen leaching

Answer 28

-most leaching takes place during low evapotranspiration and precupitation that exceeds infiltration, hence over winter
-cover crops can avoidebthe leaching of N by taking up mineral N, it is mostly immobilished by being made into organic N
-after decomposition, N mostly becomes availavle as NH4+. This is rapidly modified ibto BO3- by soil micro-organisms
-NH4+ is less pronr to leaching because as an anion it will adhere to the negative organic or clay fractions
-ehen modified into NO3- it starts moving more freely through the soil and will easily leach out of the profile
-ryegrass and ryecorn better retain existing N than legumes like veans, lupins
-for sufficient N uptake crops must have the time to develop, so soeing in late summer is needed
-when cover crops dies in Winter, temperature often too low fotlr mzch mineralisation to accour

Question 29

When water stress is really undesirable?

Answer 29

Between flowering and fruit set, because it can reduce the yield up to 50%

Question 30

When can some mild water stress be useful?

Answer 30

Between fruit set and veraison,
-to control potential berry site
-to harden the new growtg against stress
-minimise unwanted vegetative extension growth

Question 31

Vineyards with cover crops can increase water use… %?

Answer 31

10-30%

Question 32

Summer cover crops will compete with the vine for?

Answer 32

-the water in the soil
-total amount of water available to the vines from irrigation

Question 33

Does cover crop which grown iver winter compete for water during cropping season?

Answer 33

No.