Agriculture Reference
In-Depth Information
some not. Data are obtained with a yield monitor attached to a mechanical harvester
and imported into a geographic information system. If the pattern of yield variation
is consistent from year to year, blocks of vines can be identified for which soil man-
agement can be tailored to achieve desired outcomes, according to the style of wine
produced and the price point. As more data are recorded from year to year, under
different seasonal conditions, the information for decision making can be revised so
that uncertainty in the predicted outcomes is decreased. Proffitt et al. (2006) give
more details of precision viticulture and its applications in vineyards, a topic devel-
opedfurtherin“ManagingNaturalSoilVariabilityinaVineyard,”chapter6.
Summary Points
1. Grapevinesrelyonthesoiltosupplythefollowingessentialelements:N,
P,S,Ca,Mg,K,Cl,Fe,Mn,Zn,Cu,B,andMo,whicharetakenup
as inorganic ions (nutrient ions) from the soil solution. The elements
fromNthroughtoClarecalledmacronutrientsbecausevinesrequire
them in large concentrations (>1000 ppm) compared with the
elementsfromFetoMo—themicronutrients,whicharerequiredin
lowconcentrations(<1000ppm).CarbonandOaresuppliedasCO
2
through photosynthesis and H and O as water.
2. Mostofthenutrientionsareheldbyadsorptionontochargedclay,oxide,
and organic matter surfaces, which affects their availability to vines.
NutrientssuchasP,Ca,Fe,Mn,Zn,andCucanalsoforminsoluble
precipitates. Because of the strong adsorption of P by clays and oxides,
and its tendency to form insoluble precipitates, “available” P in soil
decreases markedly with time, a process commonly called P fixation.
Arbuscular mycorrhizas, a symbiotic association between a plant root and
soil fungus, can improve the P supply to vines in P deficient soil.
3. Although NH
4
+
and NO
3
−
are the forms of N taken up by vines
(the available N), 99% or more of soil N exists in an organic form.
Similarly, a significant proportion of soil P and S is in organic forms,
and the availability of N, P, and S is influenced by the balance between
mineralization (conversion to a mineral form) and immobilization
(incorporation into microorganisms and thence into humic compounds).
IronandtheothermicronutrientsexceptBandMoalsoformcomplexes
of limited availability with soil organic matter.
4. Nutrient deficiencies and toxicities can be identified from visual
symptoms, plant analysis, and soil testing. The grapevine, being a
perennial, is particularly suited to plant analysis for both macro- and
micronutrients. Protocols exist to determine which part of a vine to
sample, when to sample it, and how many samples to take. Regular plant
analysis (every one to two years) is recommended to identify trends in
