Investigating the potential of medicinal perennial species as permanent cover crops in deciduous orchards and vineyards
Date
2023-03
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Stellenbosch : Stellenbosch University
Abstract
ENGLISH ABSTRACT: Two intercropping trials were conducted, one was on Welgevallen research Farm in Stellenbosch in a
plum orchard (Prunus salicina), on a heavy clay soil with limited irrigation during 2022, with a
selection of five commercially available medicinal cover crop species (Salvia rosemarinus,
Artemisia afra, Pelargonium capitatum, Helichrysum crispum and Eriocephalus africanus). The other
was an established trial on Bon Vallon Farm in Robertson (2019) in a Chardonnay vineyard, on a
sandy clay loam soil with limited irrigation during its establishment and a selection of four
fynbos medicinal cover crop species (Salvia rosemarinus, Artemisia afra, Helichrysum crispum and Eriocephalus africanus). The trial at Welgevallen investigated cover crops during establishment,
while the Robertson trial investigated an already-established cover cropping system. Similar
parameters were investigated to evaluate the scientific impact and economic potential of both.
A literature review was conducted to evaluate how medicinal cover crops affect soil health, and how
they contribute to a more sustainable and low input agricultural system. The contrast between
conventional farming and diversified farming practices was investigated, focusing on the use of
perennial medicinal species as a more sustainable approach for crop production systems. The effect
of the different medicinal cover crop species was quantified using several parameters including
evaporation rates, soil temperature, chemical parameters and soil nutrients, survival rates, plant
cover, weed density, climate, snail presence and the harvest of medicinal cover crop biomass for a
potential secondary income.
Findings showed that in a deciduous orchard, A. afra and S. rosemarinus were the most successful
medicinal species at establishment. A. afra was the most efficient in weed suppression. A. afra
resulted in a significantly higher biomass return per hectare, although none of the treatments
resulted in a secondary income with regard to the calculations in our study. The three-year
established trial showed that the efficiency of all medicinal cover crops for weed suppression
increased as the season progressed. Both S. rosemarinus and H. crispum had significant effects on the evaporation rates compared to the control treatment. For soil temperature, there was a
significant difference between the control compared to all other treatments. No treatments resulted
in a secondary income after one harvest, although A. afra and S. rosemarinus were the most beneficial medicinal species over both trials regarding environmental
and economic sustainability in the long-term.
AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar.
AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar.
Description
Thesis (MScAgric)--Stellenbosch University, 2023.