Controlled release fertiliser as a management tool for productivity of tunnel-grown tomatoes
Date
2022-04
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : Stellenbosch University
Abstract
ENGLISH ABSTRACT: To be able to grow crops such as tomatoes on a commercial scale under stringent controlled
conditions in what is termed controlled environment agriculture (CEA), requires a great
amount of expertise and technology. Therefore, the aim of this study was to see if the use
of controlled release fertilizer as an alternative low expertise and low technology-based
fertilization method could produce the same yields and marketability than the conventional
fertigation fertilization methods used in greenhouse tomato production. The study assessed
this by (1) determining if the ratio of perlite to coco coir in the growth medium had any effect
on the yield response to an industry recommended controlled release fertilization
recommendation, (2) trying to establish an appropriate mixing ratio of controlled release
fertilizer (CRF) and liquid fertilizer (LF) to determine if a follow up fertilization application of
the pre-plant applied CRF can obtain improved yields. From the results it was evident that
by applying a mixture of 80% CRF (based on the fraction of the total % nitrogen applied)
and 20% LF with additional monthly manual application of calcium sulphate or calcium
nitrate to each planting bag, CRF could potentially replace a 100% LF fertilization
programme in greenhouse tomato production. Some results here indicate that a spike in
temperature at the beginning of the growing season may have contributed to the premature
release of nutrients from the CRF prill, causing a spike in EC. This stunted the growth of the
plants for the rest of the season, which could have been attributed to an initial toxic level of
salts in the rootzone and a prolonged deficit of other essential nutrients. The growth media
trial for the determination of the optimal perlite: coco coir ratio revealed that a mix consisting
of 20% perlite to 80% coco coir, or 40% perlite and 60% coco coir were the best ratios that
yielded the highest. Thus, for tomato production the effect of CRF would be greatly improved
if applied in an environment where the temperature and growth media properties are
favourable for the slow release of the nutrients. The evidence here did not support the
utilisation of 100% CRF as a replacement of the currently employed LF for commercial
greenhouse tomato production. In addition, it is imperative that additional calcium (Ca2+),
Sulphate (SO42-) and Nitrate (NO3-) be supplemented to reap the full benefits of CRF due to
the ongoing technological research into the ability to coat calcium-based fertilizer products
as a CRF.
AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar.
AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar.
Description
Thesis (MScAgric)--Stellenbosch University, 2022.
Keywords
Tomato growers, Controlled release fertilizers, Greenhouse tomato production, Controlled environment agriculture, Tomatoes -- Fertilizers, Tomatoes --Growth -- Yields, Greenhouse management, UCTD