Articles
INTENSIVE VITICULTURE AND ITS ENVIRONMENTAL IMPACTS: NITROGEN AS A CASE STUDY
Following the general experience with annual crops the inputs of agrochemicals increased from the beginning of the fifties up to the middle of the eighties.
As a consequence in the soils the non-leachable nutrients phosphorus and potassium accumulated whereas nitrates left the root zone and subsequently moved down to groundwaters.
Monitoring wells revealed that nitrate concentrations increased steadily and exceeded in a lot of viticultural areas the threshold values of 50 mg NO3/L. Fertilizer trials revealed that N efficiency was low.
Examining N uptake rates demonstrated that a maximum is reached after bloom, mainly at the end of June/beginning of July.
Shifting the fertilization date from early spring to the phenological stage “3–5 leaves unfolded” resulted in a good synchronisation between nitrogen applied and demand by the plant; as a consequence input could be reduced.
Viticultural sites are characterized by higher ambient temperatures, therefore naturally occurring mineralization of O.M. may contribute to soluble nitrates in the soil which has to be incorporated into the fertilization system.
Extensive incubation and calibration tests elucidated finally that with different rate constants for mineralization and only one labile C pool the nitrate delivering capacity of vineyard soils can be calculated during winter, spring and up to the critical uptake phase after bloom.
Combining N-uptake rates, application time and the endogenous nitrate available from the soil, a fertilization system for grapevines that can be managed in an environmentally sound way, (with reduced inputs and without reduced yields) can be developed.