Final Exam

*compost–decomposed plant material *manure–decomposed waste *non-legume cover crops *legume cover crops

-increased aggregation -increased water holding capacity -increased CEC -increased water infiltration -adds nutrients (nitrogen, phosphorous, potassium, etc.)

percentages vary but are generally below 5%

*non cash crop grown to amend soil, may be mown or left standing *increase soil OM, add nutrients (after decomp. OM), tie up nutrients in living plants to prevent nitrate leaching, reduce erosion, suppress weeds

-produce nitrogen -add OM -some provide nectar sources for pollinators and beneficial insects

-tie up nitrogen -add OM -fibrous roots

-long tap root -may have some biofumigant property when incorporated

-add decorative elements for agrotourism -provide habitat and food source for pollinators and beneficial insects

• What type of cover crop? (legume, grass, etc.) • Annual or Perennial? Does it self-seed? • When will the cover crop be actively growing? -cover crops don’t normally get irrigated, must be grown late fall/winter/early spring -most SJV cover crops are chosen to die/go dormant during warm season -if not they may need to be killed so they don’t compete with crops for water -in either case they should be mown, and may be tilled under

-are present in legume root nodules -bacteria are able to harvest nitrogen as N2 from the air and can convert it to ammonium (then converted into nitrate) so it is available to the plant -in return, bacteria receives carbohydrates from the plant

-root nodules that are slightly pink on the inside indicates the presence of healthy rhizobia bacteria

-not all strains of rhizobia are naturally present in the soil all the time, or may not be present in high amounts

-Nitrogen fixation rates peak just before bloom -Nitrogen that is fixed is available to the legume when it is actively growing -Nitrogen will not be available to the crop until the dead legume material begins to decompose

-temperature -soil moisture -whether the material is incorporated in the soil or left on the surface

the ‘Lana’ wooly pod vetch (cool season annual that reseeds itself)

-not a standard practice -growers concerned of costs, whether they will grow without irrigation, and whether it will take water and nutrients from the crop -compete with crops for water–not recommended for our area

-grasses can take up large quantities of nitrogen from soil, reducing nitrate leaching -to purposefully reduce nitrogen, wheat, oats or barley are often used and harvested as a crop, removing nitrogen from the soil -can be planted to release N into the soil very slowly–have a high C:N ratio

-Several species in the mustard family can uptake large amount of nitrogen like grasses do, but decompose more rapidly -Some brassicas (mustards) produce compounds that are toxic to soil-borne organisms when incorporated–potential for some biofumigant effect *efficiency of fumigant action is variable

-organisms needs carbon dioxide to survive -helps us track fuel used by all living organisms -excess carbon causing global warming

-photosynthesis by plants -respiration by plants, animals and microorganisms -decomposition of plants, animals and microorganisms -combustion of fuel

breakdown of large organic molecules into simpler components

• Moisture • Temperature • Contact of OM with soil • Carbon to Nitrogen ratio

*most microorganisms require a certain amount of nitrogen to decompose carbon materials -Low C:N ratio=they have lots of available nitrogen, will decompose relatively quickly, and plant available nitrogen will be released into the soil -High C:N Ratio=they will decompose slowly and may tie up all available nitrogen -microbes scavenge the soil for nitrogen, take all of it up, and none is available to plants to take up

-legume cover crops -grass clippings -finished compost