CROPPING SYSTEMS

A key aspect in cellular life is the phenomenon that a much greater quantity of cells are being produced by the organism than will be required. In essence, countless cells were born to serve no useful purpose and to die off prematurely. In this mechanism, nature ensures that there will be no shortage of the specialized cells required by life forms in order to function and multiply. This also creates a degree of natural selection, where only the healthiest and most useful cells produced are used, and less perfect cells die off prematurely. Through thousand of generations of selection, the species may be “improved” or adapted to localized conditions.

Growers may benefit from higher quality, healthier, and more disease resistant crops with significant increases in yield by developing cropping systems rather than “mono-cropping”. Many larger scale growers obtain their cuttings/clones from an outside source for successive crops. There is only one crop “on the go” at any given time where the same number of plants is often given the same amount of space for the entire duration of the cycle. For example, in a 10’ X 20’ area there are 10-1000W HID lamps. Cuttings are planted one per two gallon container, at a density of 16 containers per lamp for a total of 160 plants in a 200 square foot area. For the first few weeks, this is a tremendous waste of space and energy, and does not necessarily ensure the healthiest crop. Often, a portion of the plants will not establish themselves as well as the rest of the plantings, and will offer less yield for the same area occupied when compared to the more vigorous specimens.

Also as the crop develops through unique growth phases, the assumption that the conditions in the room will be ideal for each growth phase would be inaccurate. Growers may realize significantly higher and healthier yields while harvesting more frequently by developing specialized cropping systems.

Commercial greenhouse producers have been utilizing this practice for decades as efficiency correlates into profitability, particularly given the level of competition in such industries. Also with rising costs and decreasing availability of prime growing facilities, it is wise to maximize production in a given space.

Stonewool products have been developed for commercial applications requiring high efficiency levels and are an excellent example as to the basic principles of a cropping system, due to the various sizes and shapes used and their specific applications.

For example, let us examine a commercial Gerbera crop (cut-flowers). Cuttings or seeds are obtained or propagated in propagation sheets, containing individual planting cell/cubes, commonly 50 plants per 10” X 20” propagation tray. In this stage, many plants take up very little space. Light intensity and ventilation requirements are low. Diffused and constant blue light is preferred to promote short, sturdy and dense seedlings. A high efficiency compact fluorescent light will draw considerably less energy and produce much healthier plants at this stage than with HPS lighting. Experienced growers will produce 50 to 100% more plants than will be required for “finishing”. A portion may not root or germinate, and only the healthiest and most vigorous will be selected for the next growth phase. A number of cuttings/seedlings greater than required for the finishing stage are also retained for the next phase. Typically the rooting/germination period may last up to three weeks before plants have outgrown their allotted space. In this stage an area no bigger than a closet will have been used versus the entire 10’ X 20’ room. Carbon dioxide supplementation is much more efficient in smaller spaces.

In the finishing area which is 10’ X 20’ a total of 160 full sized plants will be required. The grower only needed a closet sized space for the first three weeks. Ideally a minimum of 200 plants will be grown-out to the size required for the finishing room. This way, the grower has a larger number to select 160 of the nicest specimens to finish. As a result, there will be a significant increase in yield because all the floor space in the final room will be occupied by vigorous plants capable of maximum production, as the “runts” have been culled out in the previous two stages. This stage prior to transplant into the finishing room (flowering) is for producing vegetative growth; the healthy frame work for heavy flower/fruit loads. In this example, the vegetative stage may last three to four weeks. Typically, the plants will be two feet tall and well branched through pruning before transplant into the flowering room.

In our example the commercial crop is being grown in stonewool products. For large sturdy plants, 6” X 6” X 6” blocks are used. A planting density of 49 to 64 blocks per 4’ X 4’ area is recommended. The blocks are “factory-drilled” for transplant with a cavity that snugly accommodates the tear-away stonewool plug that originated from the sheets in the seedling/rooting stage. Only four lamps and tables are required in this stage, while with conventional methods the entire crop would already be occupying the ten light 10’ X 20’ room. Again supplemental CO2 levels are much more efficient to maintain with the increased planting density. With all the plants in tables, watering may be simplified by use of a pump and timer initiating flood and drain cycles. The grower simply needs to keep the reservoir topped up and adjusted for TDS and pH.

Light usage can also be more efficient. Instead of having 10-1000W HPS lamps illuminating the crop at this point, only four HID lamps will provide optimal light. Retro type 600W lamps (producing halide type light with an HPS ballast) are perfect for illuminating a 4’ X 4’ area in the vegetative stage. Now we have 2400W of HID lighting doing the work of 10,000W of HID lighting required versus conventional “mono-cropping” methods. Ventilation and cooling requirements are reduced as only about 25% of the heat associated with conventional methods for the same number of plants is being generated.

One of the challenges in this method is keeping individual plants confined to the floor space they are each allotted. In our example, each plant will be occupying an area of approximately 6” X 6“ to 8” X 8”. Vertical growth is less efficient when using HID lighting, due to diminishing lighting intensities relative to distance from the HID source. By maintaining lower humidity levels, particularly in the dark cycle (i.e. use of a small heater during dark cycles) internodal distances can be kept shorter. Feeding the crop with slightly lower nitrogen levels while maintaining higher potassium levels also helps to prevent stretching during the vegetative growth phase. Lamps with higher Kelvin temperatures such as halide or retro lamps produce more “blue” light which has demonstrated to maintain tighter, more compact plants. The variety you choose to grow plays the largest role in determining just how much plants will “stretch.” Tighter, more compact plants are favoured for indoor cultivation.

Bending and pruning allow the grower to maintain a level of height and size control, while increasing the number of branches that the plants will have for the final stage (flowering) of production. Ideally, at the end of this stage, each plant will have six to eight main branches that are equal in height; having reduced the dominance of one main branch. This way, in the finished crop the grower will be harvesting six to eight “top” flowers versus one larger one surrounded by several smaller and lesser quality flowers. By removing the central growing point early in the vegetative stage, the grower buys the crop some time before vertical height becomes a problem while increasing the number of branches that will eventually develop into flowering tops.

So far we have spent about three weeks in the germination/rooting phase and another three or four weeks in the vegetative/structural phase. At this point, 160 of the nicest specimens are selected from the 200+ plants produced in the vegetative phase for transplant into the finishing phase in our 10’ X 20’ flowering room. At this point, the large 6” cubes have the plastic wrap removed and can be transplanted into larger containers. A minimum size of two gallons per plant is recommended for the flowering phase. Alternatively, growers may choose to transplant the well developed plants in 6” cubes into a hydroponic system such as a “bucket system”. Bucket systems, particularly with drain to waste applications, are reliable and are capable of helping the crop to achieve maximum yields. When using a hydroponic system with an inert media such as growrocks (lecca) with the 6” cubes, the medium can be sterilized for re-use with the next crop, eliminating the need to dispose of the old growing media and obtain and transport replacement growing media to the growing location. The crop is typically harvested after seven to nine weeks in the flowering phase of growth.

If the grower develops and manages a good cropping system, such as the one described above, there will always be a crop ready to transplant into the flowering room as each crop is harvested. In this method, the grower is harvesting every eight weeks on average. Also the crop harvested will tend to yield significantly higher and be of better quality because only 160 of the healthiest plants from an initial 240+ specimens have been selected to be grown to maturity.

The additional space required could be sub-divided from the original growing space available. Although this sacrifices available flowering space, the faster turn-around time between crops and the increases in yield per plant outweigh the loss of space in the flowering area. Ideally, the original size of the flowering room would be retained and a new area would be constructed. Keep in mind the additional space requirements are relatively small: a 3’ X 3’ area of the germination/rooting phase (240+ plants) and a 10’ x 10’ for the vegetative phase. Note that propagation and vegetative production do not need to occur at the same facility where the flowering/finishing area is located. A separate location can be maintained for these purposes, and plants ready to be flowered can be transported to the finishing facility as required. Note that faster flowering strains are better suited for cropping systems, as the time required for flowering is more near the same period of time required for the rooting and vegetative phase. For example: three weeks in rooting, four weeks vegetative totals seven weeks. Therefore, it would be ideal for the crop to finish flowering within 7 weeks. An eight week crop means that the grower must juggle additional time the plants will spend in the rooting and vegetative phases while the flowering crop matures.

In our example, we used stonewool products because they are available in a variety of sizes and configurations for the various applications/growth phases described. Disposal of stonewool can be problematic. At present, there are now a variety of coconut based products that are being manufactured in many of the sizes and shapes associated with stonewool products, particularly cubes and slabs. Coconut is an excellent quality growing media, and allows the grower the option of producing 100% organic crops. With proper management, good quality coco coir can be re-used over several crops, especially when much of the nutrition is supplied to the crop in the form of organic nutrients, which tend to have fewer salts to accumulate in the growing media as impurities. When the coconut is disposed of, it makes a natural looking addition to outdoor flower and vegetable gardens.