Agriculture Reference
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that many soil indicators, such as organic C content, microbial biomass, and spe-
cies diversity, are better under organic or BD systems than conventional systems.
However, fruit yields are less in the former, primarily because nutrient inputs are
less and in some cases because of weed competition. Importantly, the effects on
soil biology in organic and BD systems are only comparable if inputs of organic
materialsarethesameinboth.Moreover,comparablebeneitsforsoilbiology
can be achieved under conventional viticulture if inputs of organic materials are
adequate.Asdiscussedin“Organic,Biodynamic,andConventionalViticulture,”
chapter6,theefectsoforganicorBDsystemsonwinequalitycomparedtocon-
ventional systems have been found to be small and inconsistent.
Table 3.16 lists the range of minerals from natural sources that are acceptable
as fertilizers or soil amendments in organic viticulture.
Precision Viticulture for Better Soil Management
Precision viticulture embodies the concept of measuring soil variation with a
dense spatial array of observations and using this information to plan the lay-
out, management, and harvesting of a vineyard most effectively. Whereas figure
3.10 illustrated the point that, although the P status of a block may be deemed
adequatebasedononecompositesample(igure3.10A),thespatialpatternof
variation shown in figure 3.10B reveals that more than half the vines are deficient
or marginal in P (figure 3.10C). Clearly, correcting the P deficiency through tar-
geted fertilizer application would improve the performance of this vineyard block.
However, the cost of sampling and analysis (190 samples in this case) by standard
“wet” chemical methods would be prohibitive for a commercial vineyard.
Soil properties sensed by rapid, in-field methods have the potential to be surro-
gatesforexpensivelaboratorymeasurements.heEM38measurementsdescribed
in chapter 2 are an example of a surrogate method for assessing the variation in soil
propertiessuchassalinity,depth,orclaycontent.Midinfrareddifuserelectance
spectroscopy is another inexpensive and rapid surrogate method for measuring soil
properties at a high spatial resolution. After calibration against a database of a soil
property values, measured by a standard method, midinfrared diffuse reflectance
analysis can be applied to new sites. Figure 3.16 is an example of this method used
to map the soil CaCO 3 content of a vineyard block. Alternatively, the method can
be calibrated using a “training” data set derived from a standard analysis of a lim-
ited number of samples, covering the full range of variability at a particular site.
However,thepresentinterestinprecisionviticulturetechniquesincommercial
viticulture is focused on mapping yield variation in relation to soil variability, which
can be caused by several factors, some of which are amenable to management and
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