FANR 3060: CHAPTER 8: FERTILIZERS AND SOIL MANAGEMENT
32 Cards in this Set
| Front | Back |
|---|---|
|
the law of diminishing returns
|
a "response function" obeyed by plant production systems describing how levels of inputs affect system output
also describes how many other economic systems behave with respect to levels of inputs
|
|
what is the general idea behind the law of diminishing return?
|
there is a maximum output level, in the case of crops determined by the genetic potential of the plant
in any given soil, the yield is less, restrained by some limiting factor
as inputs are added, yields will go up, but each additional unit of input results in proportionately less incre…
|
|
growth response curve
|
shows how yield (or value of yield) changes with increasing inputs on the x axis
|
|
point of maximum profit
|
where the lower profit curve is at a maximum
|
|
point of maximum yield
|
where the yield curve plateaus
|
|
soil testing
|
attempts to get a measurement of initial amount of nutrient present in a soil, and thereby predict response to fertilizer
process involves extracting soil sample with chemical solution that is chosen to solubilize some of the soil nutrient of interest; solution is analyzed for the nutrie…
|
|
fertilizer
|
anything added to soil for primary purpose of adding plant nutrients
may be divided into inorganic types, which are largely industrially synthesized, soluble salts often referred to as "commercial" fertilizers and organic types, mostly byproduct materials that contain a lot of carbon
|
|
soil conditioner
|
something added not for nutrient content, but for its effect on soil physical properties mostly
|
|
liming agent
|
added for the purpose of increasing soil pH
|
|
fertilizer analysis
|
regulated by state laws...state occasionally analyzes them to make sure analysis is correct
nutrients must basically be in soluble form to be counted in analysis
expressed as 3 numbers corresponding to the N, P, and K content of material, given in percent
N is just %N but P and K are g…
|
|
nitrogen fertilizer
|
produced by the Haber process, first developed by Haber
N gas is reacted in a reducing flame under pressure to form ammonia gas:
N2 + 3H2 → 3NH3
the ammonia gas produced is compressed and stored as a liquified gas...ammonia itself is widely used as very concentrated form of N fertilize…
|
|
ammonium nitrate
|
NH4NO3
most common solid N which is a white pellet commonly applied alone or mixed with P and K solids (analysis of 33-0-0)
|
|
urea
|
another N solid with analysis of 45-0-0
|
|
choosing which N material to use
|
largely based on economics (i.e. which is cheapest)
also might consider that some N fertilizers (urea, annhydrous ammonia) volatilize back to NH3 gas under dry, alkaline soil conditions
|
|
advantages and disadvantages of nitrate-based fertilizer
|
advantage: absence of acid-producing nitrification
disadvantage: materials are much more expensive to purchase than ammonium forms
|
|
advantages and disadvantages of ammonium-based fertilizers
|
advantage: cheaper
disadvantage: results in production of soil acidity due to the nitrification reaction that occurs rapidly in most aerobic soils:
2NH4+ + 4O2 → 2NO3- + 2H2O + 4H+
|
|
slow release form
|
due to high solubility and limited absorption of NO3 in soil, some N fertilizers are formulated in a slow release form, when the N is released into solution gradually over several months
|
|
phosphorus fertilizer
|
second only to N in tonnage applied
manufactured using a sedimentary mineral deposit, rock phosphate, containing the mineral apatite
phosphate rock is strip-mined, crushed and treated with sulfuric acid to convert P to soluble form
calcium phosphate produced is quite soluble and used a…
|
|
potassium fertilizers
|
another mined product; large deposits of evaporite minerals, soluble salts of Na, K, Mg, Cl, and SO4, are mined to produce K fertilizer
"potash" is common trade name for K in general, referring to large amounts of K in wood ash
KCl is by far major K fertilizer used with analysis of 0-0-…
|
|
micronutrients in fertilizers
|
can be applied directly or sprayed on plant leaves (i.e. foliar sprays)
usually mixed with other fertilizer by dealer or applicator
micro-cations often applied in "chelated" form, meaning they're bound to soluble organic molecule to help keep it soluble so the plant can take it up
|
|
mixed ("complete") fertilizers
|
contain more than one macronutrient, often all three, and sometimes with micronutrients added in
can be formulated in two ways: granular fertilizers or bulk blends
|
|
granular fertilizers
|
made by chemically formulating multiple nutrients into each fertilizer pellet
each pellet in bag is identical and has analysis of something like 10-10-10
advantage: convenient to buy and apply
disadvantage: fixed ratio of N-P-K so you can't put more of one nutrient
|
|
bulk blends
|
physical mixtures of two or more fertilizers, so they contain several different kinds of pellets with different compositions
done to custom blend a mix to meet specific soil test recommendation
advantage: cheaper when bought in bulk
disadvantage: sometimes components are not mixed well…
|
|
organic fertilizers
|
mostly byproducts that contain some amount of macronutrients
includes manures, composts, some industrial wastes
often have high water contents when produced; thus, large amounts must be applied to get required amounts of nutrients and much of what is applied is actually water
much of N…
|
|
advantages and disadvantages of organic fertilizers
|
advantages: contain P and K which have value; "slow release"...nutrients released over time and less subject to leaching; increase humus levels and thus improve physical and chemical properties...use of organic materials increases "long-term" productivity of soils much more than inorganic…
|
|
LIME
|
go back and do lime
|
|
fertilizer practices
|
many fertilizers are simply broadcast (evenly spread over area) and incorporated (mixed into soil by tillage)...lime nearly always applied this way
organic fertilizers are also broadcast and typically incorporated...this is usually done over winter or early spring so there's time for rea…
|
|
starter fertilizer
|
solid or liquid applied at time of planting, often used with N and P
usually concentrates fertilizer near seed so it is readily accessible when plant begins growth
|
|
avoiding loss of nitrogen
|
N is readily lost by denitrification and leaching of NO3
to avoid losses applications are often split by applying some starter N and then applying more later in growing season on the growing crop
|
|
sidedressing
|
application of fertilizer beside rows of growing crops, often done with corn using either solid pellets surface-applied, liquids, or anhydrous ammonia injected into soil
|
|
topdressing
|
same idea as sidedressing but on a solid-seeded crop w/o rows, pastures, small grains such as wheat, or even trees
|
|
fertigation
|
process in irrigated agriculture through which nutrients can be directly injected into irrigation water to provide small amounts of nutrients continually over growing season
especially useful on very sandy soils where low CEC results in rapid leaching of large amounts of broadcasted fert…
|
FANR 3060: ROCKS