Agriculture Reference
In-Depth Information
nutrient status rather than relying on an analysis at one time. Spot samples
can be taken at any time up to veraison if a problem suddenly arises.
5. Soil testing is most appropriate at the time of vineyard establishment.
Soil tests are available for chemical, physical, and biological properties.
The most relevant chemical tests for established vineyards are for soil
pH, organic C, salinity (the concentration of soluble salts), and sodicity
(related to the exchangeable Na percentage). Appropriate physical tests
are discussed in chapter 4 and biological tests in chapter 5.
6. Nutrient deficiencies are corrected through the use of fertilizers (as
solids or dissolved in irrigation water or as foliar sprays), green manure
(in the case of N), animal manures, and composts. Fertilizers range
from single element fertilizers such as urea ((NH) 2 CO, supplying
N), to multinutrient fertilizers such as monoammonium phosphate
(NH 4 HPO 4 , supplying N and P), to blended fertilizers such as mixtures
of potassium chloride (KCl) and superphosphate (Ca(H 2 PO 4 ).CaSO 4 ),
supplyingK,P,Ca,andS.Micronutrientsaremostefectivelysuppliedas
foliar sprays.
7. Manycommercialproductsoferedtogrowersareblendedfertilizerswith
additional organic constituents such as humic and fulvic acids, molasses,
and extracts from seaweed or fishmeal. They are promoted not only for
their macronutrient content but also for the supply of growth-promoting
hormones and vitamins, the efficacy of which is difficult to substantiate.
Some of these products contain “shotgun” additions of micronutrients
(labeled as trace elements), and vendors recommend their use,
irrespective of whether a micronutrient deficiency has been identified.
8. A toxicity may be caused by a nutrient imbalance that can be corrected by
adjustments to the fertilizers or manures/composts applied, emphasizing
the point that the nutrient content of all added materials must be known.
Other forms of toxicity may arise if the soil pH is outside the optimum
range of 5.5 to 7.5 (measured in CaCl 2 solution). Aluminum toxicity
is a potential problem at low pH, whereas B and salt toxicity (resulting
from too much NaCl) can occur at high pH. High soil pH, especially in
limestone-derivedsoils,caninducedeicienciesofFe,Mn,Zn,andCu,
butMobecomesmoreavailableathighpH.
9. Organic viticulture, including biological and BD viticulture, aims to be
a closed system with external inputs used only as needed. Thus synthetic
herbicides, insecticide, fungicides, and chemical fertilizers are avoided,
except where approved by a certifying body. Composted manures,
preferably poultry or sheep manure, and composted vegetable matter are
used in organic vineyards where possible. Provided organic materials are
addedinsuicientquantities(>10t/ha)andregularly,theycanincrease
soil organic matter and biological activity in conventional, organic, or
BD vineyards.
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