Industrial Transplanting

It is the relocation of grown plants from one location to another. Plants are grown in greenhouses and transplanted (relocated) to larger acreage during the growing process.

Starting seedlings in a controlled climate provides multiple benefits including:

· Extends the growing season

· Mitigates germination problems

· Protects young plants from diseases and pests

Overview of current planting methods

Current transplanting methods occur with dirt planting (non-plastic) and plastic.

Non-plastic:

Figure 1 is a general idea as to what a more advanced planter looks like. This is planting without plastic however. Due to no plastic there are two wheels that accomplish the same function to be accomplished in this paper, bury the plants after being placed down.

Figure 1

(exploded view of planting tool. Seen here are six planting chairs and all crops to be planted)

Plastic:

While the construction of raised beds differs when done on the small-scale versus the large-scale, the advantages remain the same.

It does not matter if you want to grow vegetables, herbs, flowers, or fruit. Any industrial agricultural operation will benefit from incorporating raised beds [1]. Figure 3 gives an excellent example of raised planting beds for strawberries.

These are just a few benefits of utilizing plastic mulch:

· helps retain moisture

· suppress the growth of weeds and unwanted plants

· improve soil texture

· deter some pests

· protect plant roots from drowning or excessive temperatures

· encourage beneficial soil organisms

· provides a barrier for leafy crops from coming into contact with soil

Figure 3a

(Strawberry plants just trasplanted)

Figure 3b

(Mature Strawberry plants ready to harvest)

How the wheel perforates the plastic:

Being as the beds are covered farmers must perforate or punch holes in the plastic for placing the plant. A wheel equipped with metal spikes is driven by the friction between the wheel and the plastic. This is made possible by the weight of the wheel as it lays on the surface. Freely revolving in this way the wheel rotates around perforating a hole in the plastic. The proper name for this wheel is a water wheel and an excellent example can be seen in Figure 4. The size of the holes made in the surface are dictated by the size of the spikes equipped on the wheel. An array of sizes available can be found in Figure 5. Plants are then placed in the punched holes.

Figure 4a

(Transplanter with Water wheel between empty plant holding trays and punched holes in plastic)

Figure 5

What the base of the plant looks like when going into the ground:

Plants are grown in plastic celled sheets of the dimensions seen in Figure 6. These sheets are utilized to grow the seeds in a controlled environment such as a greenhouse. This method allows more plants to come to fruition by allowing them to not be exposed to harsh weather conditions before they are “Hardened”. Hardening off seedlings gradually exposes the tender young plants to the wind, sun, and rain. This toughens the plant by thickening the cuticle on the leaves. Another notable result of growing in these trays is the limiting size of the root ball that the plant creates within each partition. An example of this can be seen in Figures 7a and 7b.

Figure 6a

(Celled trays for starting seeds)

Figure 6b

(Lettuce seedlings in celled trays)

Figure 7a

(Strawberry seedling with exposed roots)

Figure 7b

(Bell pepper seedling)

When water wheels perforate the plastic mounds they create a hole of a larger diameter than the root ball of the plants. This is a problem because the plant's roots are left exposed. This portion of the plant can not be hardened leaving it vulnerable to undesirable temperatures until the roots become established in the planting bed.

Why not just make the spikes smaller?

An excellent question that acts as a double-edged sword when planting. Before going further another vital element for planting must be pointed out. Contained in the tanks outfitted on the machine, this element is an extremely expensive nutrient mixture that is deposited in the holes at the same time the spikes perforate the plastic. Downsizing to a smaller spike for the plant limits the amount of this vital nutrient deposited each time. So, there is a dilemma, should you size the hole down and decrease the boosting nutrient or size them up and create a larger void for the plants to stress.

While there are many ways to mitigate this problem the method being discussed in this paper is that of burying the plant after it is placed in each hole.

How the plants are placed into the holes:

Transplants while automated in some cases are placed into their holes by hand. One item that remains consistent is that these plants struggle to stay upright. The video below demonstrates the transplanting process for watermelon in Florida.

Current Process of burying:

Figure 8 pictures the numerous labourers’ needed to add additional dirt to the plants.

Figure shows how the dirt is compacted around the plant without plastic. This method is discussed later in this paper as it is still a viable option.

Reason for burring around the plant:

Burying the plant fills the difference between the plant’s roots and the sides of the punched hole. Adding soil around the starters effectively props them up keeping their leaves off the ground where heat is retained and pests are present.

Figure 8, Laborers burying by hand

Problem Statement

There are a lot of transplanting machines on the market that automate the process in their own way. However, after the plants are placed into the ground there is no effective way to add dirt around them for protection. This extra protection is needed when using plastic mulch on planting rows. The goal of this project is to develop a tool to effectively automate this process to increase crop yield.

Solution

Compacting Design

One thing that should be noted when compacting and closing the soil around the plant roots is how much static pressure is applied.

Static Pressure [3]

Static pressure is the most basic form of compaction. Virtually all objects exert some degree of static pressure compaction. The greater a particular weight, the more static pressure it will exert. Therefore, a human will only exert a fraction of the static pressure of a compacting machine, which can easily weigh upward of 19 metric tons.

Static pressure creates shear stresses. A shear stress acts to cause particles to slide across one another, forming tighter and more stable configurations. But static pressure doesn't work equally at all depths. It holds the most power at the surface and at shallow depths, but it will do relatively little when it comes to deeper soil. This design only needs to shift soil at a depth of 2-3 inches allowing for utilization of static pressure.

The downward force of the wheels is created through the weight of the wheels and the force exerted by the upper spring.

The spring is loaded in compression and is rated for 20 lbs force. There is an issue when compacting farming dirt because it cannot be too compact or the plant roots would not be able to propagate appropriately. The desired downward force set for this tool is allowed to remain constant if the elevation of the bed should change. For example if there were to be a hill there is the problem that the down force is increased. This problem is mitigated by allowing the spring to compress once it is loaded past the desired 20 lbs of force.

Isometric view

Element view

Side View

Back view

Top View

Conclusion

What I learned:

Throughout the whole project, there was a lot to learn. One thing that stuck out the most was that designing is limited to a certain degree. What I mean by this is that you can't design every last part of an assembly. When you are selecting parts for your design it is not wise to have the machine shop make the spring and bolts for a product. There is no need to do that when you can shop around from manufacturers that are great at producing just what you need. In that sense the only thing that an engineer needs to do is figure out what loads the spring will experience, the dimensions and geometry needed, and whether the part will work through back-end calculations or if it will fail. If it ends up failing you find another option that fills the same needs but may be of another material or something alike. Overall these are all problem-solving skills that have been developed through my education. Skills that are even more effective with a toolbox of engineering principles. It is also a great experience to apply my toolbox to real-world problems and take pride in finding one solution of many.

Appendix

[1] https://www.kenncomfg.com/blog/post/1536/raised-bed-farming-techniques

https://plant-pest-advisory.rutgers.edu/reasons-to-add-soil-around-the-transplant-planting-hole-on-plastic-mulch/#:~:text=Placing%20soil%20around%20the%20base%20of%20new%20transplants,don%E2%80%99t%20lose%20those%20savings%20by%20creating%20new%20problems%21