Dr. Heiner Lieth

Professor, University of California Davis


Research Needs in In-door Vertical Plant Production

Plant production in facilities with no sunlight has a number of important research areas. In some of these cases plants are grown stacked vertically to maximize the production. This vertical arrangement leads to a number of issue which represent researchable topics. One facet of this is that the key issues in most cases are different from greenhouse production. The most obvious difference is that all greenhouse production is 2-dimensional so that all calculations are done per unit floor area. With in-door production we do the calculations volumetrically. This then leads to interesting observations about level of efficiency for water, energy, and land use. In many cases, these efficiencies are an order of magnitude different. Thus there are many questions which relate to quantitative measures of factors for  making financial decisions. More specifically for each crop that is a candidate for in-door production, we need crop models which reliably simulate growth and yield forecast return on investment.

The following are some areas where research is needed to fine-tune the methodology.

Soilless culture methods can be adapted from greenhouse to in-door production, but with in-door production all irrigation and fertilization is done using fertigation and recirculation, and the precise blend of nutrients is particularly critical as plant growth is much faster. Also, irrigation water can include condensate water from the air conditioning system; but it is not fully understood how to avoid problems with such water as it has no buffering capacity. In-door production without sunlight means that lamps are used. These generate heat which generally has to be removed (energy research). LED lamps can be specifically designed to create optimal spectra specific to particular plants and growth stages.  Research is also needed on the labor side of this: nearly all indoor and vertical production facilities are fairly expensive, making it cost-effective to shift plants several times during the production cycle (requiring labor or advances in automation). This means that in-door production may have a greater demand for labor. This is good for countries which seek to have a lot of high-tech agricultural jobs, but it fuels a need for research into automation systems in countries where labor costs are high.  There is also a need for better and less-expensive sensing systems along with decision support software.


Heiner Lieth Ph.D, is a Professor of Horticulture at the University of California, Davis. Dr. Lieth’s position in the Environmental Horticulture Department interacts directly with farmers and advisors on issues faced by greenhouse and nursery growers through cooperative extension programs. He has helped develop and laid the foundation for the teaching of undergraduate courses on greenhouse and container nursery production.

During the 1980s and 1990s, Dr. Lieth’s research focused flowers and ornamental plants as a protected cultivation system of agriculture in California. This emphasized greenhouse automation, aiming particularly at automated irrigation management and environmental control. He has also conducted research on ornamental cropping systems such as roses, lilies, and chrysanthemums for cut flowers or potted plants.

In the years since then, Dr. Lieth has broadened his research and extension programs to include all kinds protected cultivation, including a wider variety of crops (including lettuce, basil, etc…) with a specific focus on soil-less production.

In 2008, he co-edited a book entitled "Soilless Culture" which describes the state-of-the-art scientific methods of growing plants without field soil. Even today, it is still the most advanced and comprehensive book on the subject.

Dr. Lieth's current research areas include lighting technology, indoor plant production, and photovoltaic energy production as an integral part of agricultural plant production. Much of the work is specifically targeted to help growers achieve the highest levels of production and efficiency. At the same time, his research program also trains some of the brightest young scientists; many of his former students can be found in positions in the industry and at universities throughout the world. He has edited two books, has published over 80 peer reviewed scientific publications, more than 380 limited-distribution reports, and twelve book chapters.