Greenhouse climate control involves optimising the elements to maximise yield at the lowest possible cost, and to do this properly, growers need to understand the effect of vapour pressure deficit (VPD) on plant growth. This is according to Deon van Rooyen, commercial manager at Vegtech Netafim and a speaker at a Netafim South Africa seminar held in Stellenbosch in November.
VPD, explains Van Rooyen, is the difference between the amount of moisture within a plant’s leaves and the air surrounding the plant. It drives various plant processes, such as transpiration, the opening of stomata, and the uptake of carbon dioxide (COâ‚‚) and nutrients.
“By managing respiration rate through VPD, one cannot only optimise plant growth, but ensure that plants stay stress-free and thus healthier. The process further optimises nutrient uptake, resulting in better yields,” he says.
TEMPERATURE PLUS HUMIDITY
Optimal VPD is achieved through the management of the humidity and temperature in greenhouse or tunnel structures.
“When it comes to climate control, growers are normally more focused on temperature than relative humidity, which refers to the amount of water vapour in the air. Humidity, nevertheless, has a much greater impact on plant health and growth than temperature has. Both should therefore be taken into account when using VPD to manipulate plant growth,” says Van Rooyen.
He adds that it means little to know the temperature in an undercover structure without knowing the humidity levels at that temperature.
Unfortunately, there is no ideal VPD setting, as it fluctuates in accordance with relative humidity and temperatures.
ãã®èšäºã¯ Farmer's Weekly ã® February 18, 2022 çã«æ²èŒãããŠããŸãã
7 æ¥éã® Magzter GOLD ç¡æãã©ã€ã¢ã«ãéå§ããŠãäœåãã®å³éžããããã¬ãã¢ã ã¹ããŒãªãŒã9,000 以äžã®éèªãæ°èã«ã¢ã¯ã»ã¹ããŠãã ããã
ãã§ã«è³Œèªè ã§ã ?  ãµã€ã³ã€ã³
ãã®èšäºã¯ Farmer's Weekly ã® February 18, 2022 çã«æ²èŒãããŠããŸãã
7 æ¥éã® Magzter GOLD ç¡æãã©ã€ã¢ã«ãéå§ããŠãäœåãã®å³éžããããã¬ãã¢ã ã¹ããŒãªãŒã9,000 以äžã®éèªãæ°èã«ã¢ã¯ã»ã¹ããŠãã ããã
ãã§ã«è³Œèªè ã§ã? ãµã€ã³ã€ã³
Review: the Toyota Hilux 2.8GD-6 DC 4Ã4 GR-Sport III
The third iteration of the Hilux GR-Sport has finally achieved a sense of presence and style befitting its raceinspired branding. But is this the ultimate modern Hilux? Car Magazine takes a closer look.
Why maize prices soar in Kenya and Malawi but not Tanzania
Namhla Landani, an economist at the Centre for Competition, Regulation and Economic Development, University of Johannesburg, and Arthur Khomotso Mahuma, economist and researcher at the Centre for Competition, Regulation and Economic Development, University of Johannesburg, analyse the issue.
Wet carcass syndrome: a scourge in SA sheep farming
Wet carcass syndrome continues to take a huge financial toll on South African sheep farmers. Octavia Avesca Spandiel spoke to two experts about the ongoing genetic research aimed at addressing this issue.
Pollination innovation
Bee-Tech Group is transforming South African agriculture with pollination technologies that boost crop yields and enhance sustainability. Founder Michiel Bruggeman spoke to Octavia Avesca Spandiel.
The valuable addition that makes this farm tick
Owning the value chain provides farmers with far more control over their produce. However, it requires a fine balance between production and ensuring there is a strong and steady market. Lindi Botha visited Rosemary Hill to find out how this essential oil producer leverages hospitality to make the farm viable.
The benefits of recirculating aquaculture systems
A powerful set of attributes has established recirculating aquaculture systems as a cornerstone of global temperate fish farming, writes Leslie Ter Morshuizen, owner of Aquaculture Solutions.
Minister has big plans for emerging and commercial farmers
DA leader and Minister of Agriculture John Steenhuisen spoke to Glenneis Kriel about his priorities for his department over the next five years, including an increased focus on biosecurity.
New study aims to make wheat more disease resistant
A recent international study explains how bread wheat has helped to transform the ancient world on its path to becoming the iconic crop that today helps sustain a global population of eight billion.
Conservation farming and biodiversity boost soil health and sustainability
A recent academic event focused on research into the links between soil biodiversity, soil health and sustainable agriculture
What has led to the unparalleled rice shortage in Japan?
Japan is facing a rice shortage amid concerns about a potential 'megaquake', several typhoons and an annual week-long holiday, which has led to an increase in panic buying.