Greenhouse Area Research Articles

Florida Vegetable Transplant Producers Survey, 1989-1990

Thirty-four operators produced > 1.15 billion vegetable transplants in Florida in the 1989-90 season. Sales, concentrated in the winter and spring, were estimated at $30 million. Firms in the industry also made additional sales of ornamental and agronomic plants. Nine large firms accounted for 88% of all transplants produced. More than 109 acres (44 ha) of greenhouse area are allocated to containerized vegetable production. The majority (83%) of Florida s vegetable transplants were from three crops--tomatoes (45%), peppers (28%), and cabbage (10%). Only 36% of the transplants produced in the state were shipped out-of-state. This report discusses various facets of production, marketing, labor, and general business conditions of the containerized vegetable transplant industry.

BIOLOGICAL PEST CONTROL WITH CONTINUOUS GREENHOUSE CULTURE

A strategy for controlling pests with biological control was sought for production of salad greens and herbs in a nutrient film technique (NFT) growing system. A case study was initiated in October 1989 using a one half hectare greenhouse range (1988 construction) with no past or present synthetic insecticide use. Problematic pests were aphids and thrips. A natural predator/pest cycle (NPC) area was established (5% of total greenhouse area with potted herbs on benches) to provide an area for predators to establish and reproduce. Introduced predators, which successfully reproduced in the greenhouse, were Apidoletes aphidimyza (aphid control), Amblyseius macKenzie, and A. cucumeris (thrip control), Encarsia formosa (whitefly control), and Phyoseiulus persimilus (two spotted spider mite control), Naturally occuring predators of importance included a wasp parasitoid of aphids (Hymenoptera) and an insect predator, the minute pirate bug (Hemipters, Anthocoridae), which feeds on thrips and aphids.Two flying predators of aphids (A. aphidimyza and the wasp parasitoid) dispersed well from the NPC area and provided effective control. The technique of applying the thrips predators, a slow moving mite to flats shortly before transplanting provided good dispersal on all transplants. The time for effective control by the predator was 4 to 6 weeks. Effective control was observed in chives but not shorter cycle crops (3 to 5 weeks average). Immature minute pirate bugs were also observed in the chives assisting in control. Effective spider mite control was accomplished 2 to 3 weeks after the release of P. persimills into infested area. Whitefly populations have been effectively controlled by E. formosa.

ENERGY EFFICIENT SUB-TROPICAL GREENHOUSES WITH CARBON DIOXIDE ENRICHMENT

A system for greenhouse temperature control to make carbon dioxide enrichment of greenhouse atmospheres in sub-tropical climates practical is proposed. The system which incorporates a rockpile thermal energy storage for both cooling and heating the greenhouse is expected to result in a reduction in greenhouse area and energy input required for the production of a given quantity of greenhouse crops. Design concepts and predicted performance of the system for an experimental greenhouse are presented.

Optimal greenhouse production under economic constraints

The rates of growth and development of a greenhouse crop are affected by the inside environmental conditions. These can be manipulated by the grower, at a cost which reflects the applied intensity of cultivation. More intensive cultivation, namely, more heating, more CO 2 enrichment, etc., results in a higher operational cost, but in a shorter growing period or better produce. The economically optimal cultivation intensity, which is a function of the biological characteristics of the crop, the engineering characteristics of the structure and the weather and economic environments of the greenhouse operation, can be obtained by methods of optimal control theory. In simple cases, such as growing certain vegetative crops, the optimal cultivation intensity is a single constant number. This number, when inserted into a control generating function, can produce a non-repeating control sequence, depending on the continuously varying weather. The value of this policy parameter depends, among other factors, on the economic constraints imposed on the production system. In particular, a grower operating under a quota constraint, should not change his cultivation intensity as a result of changing market prices for his produce. On the other hand, a grower whose greenhouse area is limited, but not his market, should increase his intensity of cultivation as the market price increases.

Hydroponic Production of Cut Chrysanthemums: A Commercial Trial

Abstract A hydroponic nutrient film (NF) system was compared with soil for the production of five cut chrysanthemum crops in a commercial greenhouse. Crops of the cultivars Polaris; Blue, White and Florida Marble; Icecap; Chardonnay; and Heirloom matured 5 days earlier, on average, in NF than in soil. Yields of flowering stems were similar in each system, but close spacing increased productivity per unit greenhouse area for NF. Costs and returns for installation and operation of soil and NF systems in a 1-ha greenhouse were analyzed based on data obtained from the trial crops. Capital and operating costs per unit area increased for NF, but productivity and returns were also greatly improved. Internal rates of return (IRR) were higher for NF, compared to soil, over economic lifetimes ranging from 5 to 25 years. Product price variations caused similar changes in IRR for both systems. A 20% downturn in price, however, resulted in IRR of 3.5% and 19.4% for soil and NF, respectively, over a 25-year lifetime.

Surface Heating Greenhouses with Power Plant Cooling Water

ABSTRACT A small greenhouse was heated with power plant cooling water during February and March, 1977. The heating system used nozzles to spray heated cooling water on the outside of the greenhouse. The ad-vantages of this system for utilizing heated cooling water are low capital costs for the system and no in-crease in greenhouse humidity because the green-house air does not contact the water. A flow rate of 0.094 L/s per m2 of greenhouse area is sufficient to heat the greenhouse to 15 °C using 30 °C water. With this efficiency the cooling water from an 1800 megawatt power plant could be used to heat ap-proximately 30 ha of greenhouses.

Control of Grapevine Aphid, 1976

Abstract Several insecticides were evaluated for control of the grapevine aphid on 2-year-old potted grape vines reared in a greenhouse. Cultivars used in tests were Chancellor, Aurore, Cayuga White, Seyval, Clinton, Vidal 256, Ellen Scott, Vignoles, Villard Noir, Gewurztraminer and Chardonnay. All cultivars were naturally infested by the aphids. In Test I , plants were carried outside the greenhouse, sprayed and left outdoors until counts were made. In Test I I , plants were sprayed in hooded area of greenhouse and held inside until mortality was recorded. Treatments were composed of single vines replicated 4 times in randomized blocks. Only the aphids on the apical 1 1/2 inches of one shoot per vine were considered. Counts were made prior to and 24 hr after application. Sprays were applied to run-off, at the rate of 100 gal per acre using a Hudson 6209 Favorite sprayer at 40 psi. Nu-Film-17 extender was added to all treatments at the rate of 1 pt/100 gal.

Quelques essais d'inoculation mycorrhizienne

Tests of mycorrhizal inoculations were made in containers (greenhouse and propogation area) and in the nursery. Several types of inoculum were tested: forest humus, spores, pure cultures on wheat grains, on agar medium and on a mixture of vermiculite and peat. The inoculum on wheat grains gave good results in the nursery while in containers spores were the most efficient in producing mycorrhizae.